Bio-butanol as a new generation of clean alternative fuel for SI (spark ignition) and CI (compression ignition) engines

Journal Pre-proof Bio-butanol as a new generation of clean alternative fuel for SI (spark ignition) and CI (compression ignition) engines

Xudong Zhen, Yang Wang, Daming Liu PII:

S0960-1481(19)31616-7

DOI:

https://doi.org/10.1016/j.renene.2019.10.119

Reference:

RENE 12488

To appear in:

Renewable Energy

Received Date:

20 December 2018

Accepted Date:

20 October 2019

Please cite this article as: Xudong Zhen, Yang Wang, Daming Liu, Bio-butanol as a new generation of clean alternative fuel for SI (spark ignition) and CI (compression ignition) engines, Renewable Energy (2019), https://doi.org/10.1016/j.renene.2019.10.119

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Journal Pre-proof

Bio-butanol as a new generation of clean alternative fuel for SI (spark ignition) and CI (compression ignition) engines Xudong Zhen a,, Yang Wang b, Daming Liu a a

School of Automotive and Transportation, Tianjin University of Technology and Education, Tianjin 300222, China

b

State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China

 Corresponding author. Tel.: +86 22 88181100. E-mail address: [email protected] (X. Zhen).

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Bio-butanol as a new generation of clean alternative fuel for SI (spark ignition) and CI (compression ignition) engines Abstract: Bio-butanol (N-butanol) is a renewable, environmentally friendly, and economical alternative fuel that, like many other alternative fuels such as methanol, ethanol, and natural gas, is also considered to be one of the most advantageous fuels to replacement for conventional petroleum fuels (such as gasoline or diesel fuel). Bio-butanol fuel has recently been used as an alternative fuel to conventional fuels for IC engines (gasoline or diesel engines) to meet some environmental and economic considerations. Compared with conventional fuels (gasoline and diesel fuels), bio-butanol has many advantages, so it has the potential to reduce vehicle emissions, thereby improving the atmospheric environment, reducing energy demand pressure, and significantly decreasing the car's dependence on non-renewable resource. The research and application of bio-butanol have made great progress in the past few years, so it is worth to summarize and analyze the application of bio-butanol in IC engines. This paper systematically introduces the application of bio-butanol fuel in SI and CI engines, and summarizes the application methods of bio-butanol/gasoline, bio-butanol/diesel and other mixed fuels on SI and CI engines. Finally, some suggestions for the future research and development direction of bio-butanol engines are put forward in study. Keywords: Bio-butanol; Application methods; Spark ignition engines; Compression ignition engines Nomenclature ABE: acetone, butanol and ethanol

ANN: artificial neural network BA: butanol-acetone 1

Journal Pre-proof BBu: biodiesel-bio-butanol BE: biodiesel-ethanol BRE: n-butanol rotary engine BSFC: brake-specific-fuel-consumption BTE: brake thermal efficiency CAD: crank angle degrees CDC: conventional diesel combustion CI: compression ignition CN: cetane number CO: carbon monoxide CO2: carbon dioxide CR: compression ratio DEE: diethyl either DI: direct injection DISI: direct injection spark ignition DME: dimethyl ether EGR: exhaust gas recirculation EVC: exhaust valve closing FTIR: Fourier Transform infrared GCI: gasoline compression ignition GDI: gasoline direct injection GMD: geometric mean diameter 2

Journal Pre-proof GTL: gas-to-liquid HBRE: hydrogen-enriched n-butanol rotary engine HC: hydrocarbon compounds HCCI: homogeneous charge compression ignition HPCC: highly premixed charge combustion mode HSDI: high-speed direct injection IBE: isopropanol-bio-butanol-ethanol IC: internal combustion IMEP: indicated mean effective pressure KLST: knock limited spark timing LD: light duty LPG: Liquefied petroleum gas LTC: low-temperature combustion MFB: mass fraction burned MON: motor octane number MPRR: maximum pressure rise rate NG: natural gas NOx: nitrogen oxides PAH: polycyclic aromatic hydrocarbon PCI: premixed compression ignition PFI: port fuel injection PM: particulate matter 3

Journal Pre-proof PN: particulate numbers PPC: partially premixed combustion PPCI: partial premixed compression ignition RCCI: reactivity controlled compression ignition RON: research octane number SI: spark ignition TEM: transmission electron microscope TI-LII: two-color laser induced incandescence TPNC: total particle number concentration UBHC: unburned hydrocarbon UHC: unburned hydrocarbons ULSD: ultra-low sulfur diesel UV: ultraviolet VCR: variable compression ratio WOT: wide-open throttle 1-D: one-dimensional

1. Introduction Nowadays, the emission of automobile exhaust becomes more and more serious, and it has been paid more and more attention by governments. Some European countries (Such as the United Kingdom, Sweden and many other countries) have even proposed plans to cancel conventional fuel vehicles (gasoline engines and diesel engines), and the timetables have been set. Today’s gasoline vehicles are under 4

Journal Pre-proof tremendous pressure. The use of electric vehicles is increasingly being promoted in some countries such as China, and its applications are increasing. However, there are also many problems with electric vehicles, for instance, the charging time of the power battery, the cruising range and the post-processing of the battery (currently, there is no revolutionary breakthrough in power battery technology). The safety and maintenance problems of electric vehicles are also increasingly exposed. Therefore, it is quite difficult to promote electric cars and achieve a certain number of applications in a short time. Compared with electric vehicles, hydrogen fuel cell vehicles are more difficult to promote (hydrogen storage and safety issues etc). In addition, the use of energy by a single use of electrical energy is not scientific. The energy used in vehicles should consider some key issues such as energy security issues, balance issues, and regional characteristics issues. Therefore, the development of alternative energy sources, even the use of renewable energy, has good prospects in vehicles. With the development of the production technology of bio-butanol, it is found that there are certain possibilities for use in vehicles. It has a good application prospect in the future. Bio-butanol is a promising alternative fuel, its production technology, storage technology and transportation technology are becoming more and more mature. Compared with the conventional fossil fuels, bio-butanol (CH3(CH2)3OH) fuel has been considered to be a new generation of alternative fuels for IC engines (SI engines or CI engines) in the future. Bio-butanol fuel is adapted to various types of IC engines, for instance, 1: it can be used in CI engines; 2: it can be used in inlet port 5

Journal Pre-proof injection SI engines; 3: it can be used in GDI engines; 4: it can be used in HCCI engines; 5: it may be applied to the rotor engines. As countries around the world impose stricter requirements on vehicle emissions, it is only a matter of time before gasoline and diesel are gradually replaced by other fuels. In the future, the proportion of renewable energy in IC engines will gradually increase. In China, ethanol gasoline (E10) fuel has been used to replace pure gasoline, and the application of methanol fuel has been gradually recognized by the government and automobile companies. The application of bio-butanol in engines has many advantages, such as reducing engine fuel consumption and emissions. At present, the bio-butanol mixed combustion method is widely used in SI and CI engines. In the future, the application of bio-butanol fuel in engines will gradually increase. The research on bio-butanol engines has certain practical significance and good prospects. This paper systematically introduces the application of bio-butanol fuel in SI and CI engines, and summarizes the application methods of bio-butanol/gasoline, bio-butanol/diesel and other mixed fuels on SI and CI engines. Compared with other review articles, this study mainly introduces the application mode, application technology and application trend of bio-butanol fuel in SI and CI engines. The working principle and application of the two engines are completely different, and the bio-butanol replacement method is different, this paper mainly introduces the application of bio-butanol in two kinds of engines, and what is the performance of the bio-butanol engine being studied. In this study, some many methods of application such as bio-butanol/gasoline, bio-butanol/diesel blends which can be used on the IC 6

Journal Pre-proof engines are summarized, which has certain reference value to the research and application of bio-butanol engines. Finally, it puts forward some suggestions for the future research and development directions for the bio-butanol engines. 2. The production methods, marketing and the properties of bio-butanol 2.1 The production methods and marketing of bio-butanol Bio-butanol fuel can be produced and refined from lignocelluloses, and it plays deterministic roles in bio-butanol production (pretreatment and hydrolysis can be customized) [1]. Bio-butanol also can be produced by many various resources and technologies. With the development of technology, the current production techniques and methods of bio-butanol have been greatly improved [2-18], it can be produced based on many various resources, for instance, syngas [3], sugars [4], municipal solid [5], lignocellulosic biomass [7], bio-diesel [9], waste of corn [10], wheat starch wastewater [11], ethanol [12], crude glycerol [13], etc. Fermentation is an important technique in bio-butanol production, for instance, it can be produced by fermentation using clostridium carboxidivorans or solventogenic clostridia [2]. However, due to the high substrate costs and low fermentation efficiencies, economical production of bio-butanol is hampered. Currently, in order to overcome and avoid these problems, genetic manipulations have been widely applied to solventogenic clostridia on the basis of systems metabolic engineering [19]. Today, most of bio-butanol production is synthetic, and derived from a petrochemical route based on propylene oxo synthesis, in which aldehydes from propylene hydroformylation are hydrogenated to yield bio-butanol. Synthetic bio-butanol production costs are not only with the propylene 7

Journal Pre-proof market, but also with the price of crude oil [20, 21]. In the production of bio-butanol fuel, different methods will produce different impacts on the environment, so the choice of production method is very important. The environmental impacts of three butanol production methods have been analyzed and compared by the Brito and Martins [22]. In study [22], the first production method is based on the oxo synthesis, and the other production methods are based on ABE fermentation. A method of life cycle assessment for all alternatives was also carried out in study. It was found that during the ABE fermentation process, with the corn the variation of wastewater produced, the environmental impact could be decreased lower than 1%. A kinetic model of ABE fermentation has been developed by Zhou et al [23], and the acetic/lactic acids effects were considered in the developed model. Overall, with lactic acid or acetic acid addition, the developed kinetic models could accurately predict the dynamic behavior of metabolites in ABE fermentation, and consequently identify genetic manipulation strategies for higher bio-butanol productions in the future. The conventional bio-butanol fermentation process mainly uses corn liquefaction, semi-continuous fermentation, and product distillation, etc. as indicated in Fig. 1 (the first generation bio-butanol production method) [24].

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Fig. 1. First generation, second generation and third generation bio-butanol processes and their corresponding microbial bio-butanol fermentation pathway [24, 25]

Feedstock and utilities (mainly steam cost for distillation) account for the largest costs, 66% and 16%, respectively, of the whole process (Fig. 2) [26]. Besides the common feedstock like sugar and starch (sucrose containing feedstocks), other biomasses can become feedstocks such as barley, straw, bagasse, corn core or other materials. The detailed cost distribution, technology and methods of bio-butanol fromeach process are illustrated in Table 1 [24, 25].

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Journal Pre-proof Table 1 Cost distribution, technology and methods of bio-butanol fromeach process [24, 25] Corn

Corn-based

Fixed costs &

Waste water

others

treatment

66%

12%

5%

17%

1.87

Feedstock

Fixed costs &

Enzymes &

Utilities&

N-butanol

others

pretreatment

Waste

n-butanol Cellulosic n-butanol

Utilities

N-butanol

cost

($/kg)

water

cost

($/kg)

treatment 30%

15%

35%

20%

1.32

Biobutanol

Extractive

Gas

pervaporation

Two-step

Immobilization

Four

separation

fermentation

formulation

fermentation

techniques

step

technology

method

Reasons

Butanol

is

Low

affecting

more toxic to

yield

butanol

bacterial

fermentation

strains

The

Starch

and

sugar

raw

raw

material

solvent

Cellulosic

Low

Fermentation

production

materials are

efficiency

expensive

biosyngas

Agricultural

Glycerin

and

algae

materials strain

waste biomass

Clostridium

Clostridium

Clostridium

Clostridium

difficile

saccha

beijerinckii

Saccharobutyl

Roperbuy

icum

lacetonicum Method

of

butanol

forestry

Carbonyl

alcoholization

synthesis

Biological fermentation

production Butanol

Pre-fermentati

Main

Post-fermentat

fermentation

on

fermentation

ion

process

(acid

stage

(acid recovery

increasing

(acid reduction

period)

period)

stage)

The use of

Used

butanol

solvent

period

as and

perfume

Used as raw material

period

biofuels

in

organic synthetic chemical industry

10

and

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Fig. 2. Cost distribution of corn-based and cellulosic bio-butanol fromeach process area in China, based on percentage and overall cost [26]

Fig. 3 (a) shows the process of bio-butanol production with different feedstocks [25, 27, 28]. It basically shows the steps followed during the process. Fig. 3 (b) brings the schematic drawing of a possible configuration of a bio-butanol production plant. It is based on the process described above and using the different feedstock cited [25, 27, 28]. In Fig. 3, the production steps can be followed during the process: (1) biomass containing lignocellulosics is pretreated for the fementation; (2) detoxification to remove the inhibitors; (3) fermentation; (4) the acetone, ethanol and butanol are separated based on the different boiling points. As the increase in applications, technological advancements, and the growing demand in Asia-Pacific, the global bio-butanol market witness high growth. There has been a considerable growth in the production and application of bio-butanol fuel. Because bio-butanol has many advantages, so bio-butanol is a very competitive renewable bio-fuel for IC engines (SI engines and CI engines). Compared with the 11

Journal Pre-proof conventional gasoline, diesel fuel, and some widely used bio-fuels, i.e. methanol, ethanol, bio-diesel, it was found that bio-butanol has the potential to overcome the drawbacks brought in by low-carbon alcohols or bio-diesel. The market of bio-butanol has grown significantly during the past many years. It is forecast to grow at a more rapid pace in the next few years, mainly driven by the growing demands in the Asia-Pacific region. China consumed around 34.8% of the global bio-butanol demand in 2012. Production facilities of bio-butanol are majorly concentrated in Europe and North America, which are the key exporting regions. Asia-Pacific bio-butanol market has been valued at $3.0 billion in the year 2013 growing at 7.7% annually, and is projected to reach $4.3 billion by the end of the year 2018. Asia-Pacific bio-butanol market constitutes 44.5% of the global bio-butanol market, and is poised to grow its market share to 45.7% by the end of year 2018 [26, 29]. At present, the energy supply is mainly fossil fuels such as gasoline and diesel fuel, and it is non-renewable source. With the growth of the world’s population and the continuous deterioration of the atmospheric environment, the development of renewable resources is indispensable. Bio-butanol is a very good alternative fuel to instead of conventional fossil fuels. Among many various renewable alternative resources, there are many advantages to develop alcohol-based fuels, for instance, First, in can improve the emission environment, especially for vehicle exhaust; Second, it can guarantee a country’s energy balance and reduce dependence on conventional fossil fuels; Third, it can guarantee the national energy security and sustainable development; Fourth, developing renewable resources can also bring more 12

Journal Pre-proof job opportunities to the country.

(a)

(b)

Fig. 3. Schematics of a biobutanol production process and plant [25, 27, 28]. (a) Schematic of biobutanol production process. (b) Schematic of a biobutanol production plant. 13

Journal Pre-proof 2.2 The physical and chemical properties of bio-butanol Bio-butanol, as a kind of alcohol substitute fuel with methanol and ethanol, has unique advantages. Its hydrophilic is weak, its corrosion is small, and it is convenient for pipeline transportation. So, it can be applied in various engines such as SI engines and CI engines. As the fuel demand and environmental protection increasing, people began to search for new alternative energy sources for IC engines. Biofuels are often added to fossil fuels for application, the most common being the addition of ethanol to gasoline and diesel. It is a huge challenge of coordinating their performance with the engine for the automotive and petroleum industries. The demand for diesel in Europe is increasing, while demand for gasoline is declining. This raises the question of how to increase the amount of biological additives in diesel. Bio-butanol is a four-carbon, straight chained alcohol, and it is an important chemical precursor for paints, polymers, and plastics. Bio-butanol has also significant advantages in fuel performance and economy. First, butanol is more compatible with gasoline and can achieve a higher mixing ratio with gasoline. Without changing the engine, ethanol can be mixed with gasoline at a maximum of 10%, and the amount of butanol allowed in gasoline can be even higher. Second, butanol has a higher energy density. Compared with conventional fuels, it gets 10 percent more miles per gallon than conventional fuel and 30% percent more than ethanol. Compared with methanol and ethanol fuels, the molecular structure of bio-butanol contains more carbon atoms, and can store more energy per unit volume. Experiments have shown that the energy density of bio-butanol is similar to that of gasoline, and the energy density of ethanol 14

Journal Pre-proof is 35% lower than that of gasoline. Third, compared with many other alcohol fuels such as ethanol, bio-butanol has a low vapor pressure, so it can flow through the pipeline, and has a high tolerance to water as an impurity when mixed with gasoline, making it more suitable for use in existing gasoline supply and distribution systems. Table 2 the properties of bio-butanol, gasoline and diesel [30-34] Fuel property

Bio-butanol

Gasoline

Diesel

Formula

C4H 9 OH

C5-12

C10-26

Molecular weight

74.11

95 ~ 120

180 ~ 200

Oxygen content

21.5%

0

0

Stoichiometric air/fuel ratio

11.2

14.6

14.5

Low calorific value (MJ/kg)

33.1

44.5

42.5

46.6

45.8

High calorific value (MJ/kg) Freezing point (ºC)

-88.9

-57

-1 ~ -4

Boiling point (ºC)

118

30 ~ 220

175 ~ 360

Flash point (ºC)

35

-45

55

Auto-ignition temperature (ºC)

343

228 ~ 470

220 ~ 260

Research octane number

98

80 ~ 98

Motor octane number

85

81 ~ 84

20~30

Cetane number

25

0 ~ 10

40 ~ 55

inflammability limit

1.4-11.2

1.47 ~ 7.6

1.85 ~ 8.2

specific heat (20 ºC ) (kJ/kg · K)

2.63

2.3

1.9

latent heat (kJ/kg)

582

310

270

Viscosity (20 ºC) (CP)

3.6

0.29

3.9

The physical and chemical properties of bio-butanol, gasoline and diesel fuels are shown in Table 2 [30-34]. Bio-butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for gasoline and for diesel applications. Bio-butanol as a potential second generation biofuel could be a future option for blending with diesel [35]. Compared with the gasoline, diesel or other 15

Journal Pre-proof alcohol fuels, it has good miscibility, higher calorific value, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Compared with short-chain alcohols, bio-butanol has many advantages, so it is considered to have a good prospect of soot reduction [36]. The characteristics of bio-butanol are summarized as follows: (1) with the increase of carbon atoms numbers, the low calorific value of alcohol fuel is increased. The low calorific value of bio-butanol is 31% higher than ethanol and 76% higher than methanol. Therefore, compared with methanol and ethanol, when it is applied to engines, its power output and fuel consumption are better; (2) compared with methanol and ethanol, the volatility is weaker, so the possibility of cavitation and air resistance in the fuel supply pipeline can be reduced; (3) when the fuel is vaporized, the higher vaporization latent heat value of butanol leads to the obvious decrease of the temperature in the cylinder. Although it is beneficial to the air intake of the engine and the power performance is compensated, due to the low combustion temperature in the cylinder, it is easy to cause the difficulty of cold starting under the low temperature environment. At present, the mixed combustion method is widely used in engines; it can reduce the temperature of cylinder mixture, reduce the emission of nitrogen oxides; (4) the higher octane number of bio-butanol can improve the anti-knock property of mixed fuel, and the compression ratio of engine can be increased; (5) bio-butanol has a wide ignition range and is capable of achieving lean combustion; The flame propagation rate of bio-butanol is faster than that of gasoline, which promotes combustion; (6) bio-butanol is an oxygen-containing fuel, which can 16

Journal Pre-proof reduce the emissions such as CO, HC and NOx. 3. Bio-butanol fuel used on SI engines 3.1 Engine using pure bio-butanol (Bu100) as fuel From the engineering application perspective, bio-butanol fuel can be an ideal renewable, environmentally and economically alternative fuel for conventional fuels (gasoline or diesel fuels). Bio-butanol has a high calorific value and octane number, which is very close to gasoline, which can replace gasoline as engine fuel and reduce the dependence of fossil fuels [27, 37, 38]. The pure bio-butanol fuel engine is an alternative to gasoline engine [39, 40]. The emissions characteristics of neat butanol fuel have been studied by Wigg et al [37] in a port fuel-injected, SI engine. In study [37], the brake torque and exhaust gas temperature performance were studied, and the emissions of unburned HC, CO, and NOx were studied based on the three fuels (gasoline, n-butanol, ethanol) in terms of combustion byproducts. It was found that butanol and gasoline were close in engine performance, and the butanol producing slightly less brake torque, and a lower peak combustion temperature. The combustion process has been investigated by Irimescu et al [39] in an optically accessible DISI engine. The results showed that bio-butanol induced little increase in performance, and reduction of smoke opacity and NOx; bio-butanol was featured by higher flame speed than gasoline, but slower flame kernel evolution; at fixed load, butanol showed comparable OH emission with lower CO-O and CH intensity than gasoline. Liu et al [40] studied the effects of air dilution and effective compression ratio on the combustion characteristics of a HCCI 17

Journal Pre-proof engine fuelled with bio-butanol. The results showed that air dilution and the decrease in EVC could retard the auto-ignition timing of bio-butanol, and effectively decreased the MPRR of the HCCI engine. Air dilution was more effective in reducing the MPRR, but lead to longer combustion duration as compared to decreased EVC. Venugopal and Ramesh [41] studied the effective utilization of butanol along with gasoline in a SI engine through a dual injection system. The new dual injection system can easily vary the ratio of alcohol and gasoline. It was found that compared with the gasoline, neat bio-butanol could reduce the knock tendency at full load by charge cooling, and engine torque could be improved at full load with bio-butanol. Agathou and Kyritsis [42] investigated the bio-butanol laminar non-premixed flamelets. It was found that compared with the methane fuel, butanol flames were more vulnerable to extinction, and N2 concentrations varied inversely proportionally to temperature across the flame. The laminar flame propagation of bio-butanol/air and bio-butanol/ (14% O2/86% He) mixtures was investigated in [43]. In study [43], a constant-volume combustion vessel was used at the unburnt temperature of 423 K, initial pressures of 1-20 atm and a series of equivalence ratios. Flame instabilities of bio-butanol, including cellular instability and pulsating instability, were studied based on flame morphology. Compared with the bio-butanol/air flames, the smaller densities and lower reactant concentrations resulted in the smaller laminar burning fluxes of bio-butanol/O2/He flames. Sensitivity analysis was performed using the updated model under wide pressure and equivalence ratio ranges. The similarity in the sensitivities indicated that the sensitive reactions in bio-butanol/air flames could be 18

Journal Pre-proof validated by using bio-butanol/O2/He flames, which greatly compensated the problem that the bio-butanol/air flames were susceptible to flame instabilities at high pressures. The weaker pressure dependence of the LBVs of bio-butanol/O2/He flames indicated that their flame chemistry changed less to resist the pressure variation. 3.2 Engine using bio-butanol/gasoline blends as fuel Bio-butanol fuel can be blended with gasoline in engines, and it can be blended with gasoline (90% bio-butanol and 10% gasoline; 80% bio-butanol and 20% gasoline) or many other percentages, and it can replace gasoline without performance penalties in many operation conditions. Many butanol/gasoline blends engines have been studied by researchers [44]. 3.2.1 The power input and economy performance of bio-butanol/gasoline engines Bio-butanol is an option of bio-fuel with potential to be used in the transportation industry. There is little information about performance of engines running with this alcohol, and thus is very difficult to evaluate its advantages. A way to bypass this limitation is to use numerical simulation, mainly 1-D models, to represent the whole engine and preview its performance running with different fuels [45], the established engine model is illustrated in Fig. 4 (a) (Gt-power software platform model, which is an engine industry standard simulation tool and used by most engine and automotive manufacturers and suppliers worldwide) [45], starting with a virtual engine model, the fuel properties were adjusted based on test measurements until good agreement between numerical results and measured results was obtained. It can be seen from Fig. 4 (a) [45], It can be seen from Fig. 4 (a) [45] that the model consists of eight parts: 19

Journal Pre-proof engine inlet, intake manifold, intake ports and valves, cylinders, base engine, exhaust ports and valves, exhaust manifold, and exhaust after-treatment, the details are as follows: 1) Engine inlet: Air is drawn into the air filter from the air inlet and the air filter filters the air. 2) Intake manifold: The intake manifold is the intake pipe between the throttle and the intake ports. The air is mainly distributed to each cylinder intake ports by throttle. The model in the figure is a four-cylinder engine, so the intake manifold has four lanes, and the length of the intake manifold is the same to distribute the air evenly to each cylinder. 3) Intake ports and valves: The intake ports are passage of air into the cylinder and is mainly composed of pipes designed on the cylinder head. The end of the intake ports is the intake valves, and the intake valves are mainly to control the intake air. The fuel injector is located on the bifurcation line between the intake manifold and the intake ports. The injector is mainly used to inject fuel into the intake ports and mix it with air. The model has two intake ports and intake valves on each cylinder, and the four cylinders have a total of eight intake ports and intake valves. 4) Cylinders: The cylinder is a cylindrical metal member that guides the piston to linearly reciprocate within the cylinder. The model has four cylinders. The combustion of the mixture in the cylinder converts thermal energy into mechanical energy. 5) Base engine: The base engine is mainly composed of crankcase, crankshaft and 20

Journal Pre-proof engine body. Lubricating oil in the crankcase cools and lubricates the engine. The piston is connected to the crankshaft, and the combustion of the mixed gas pushes the piston to move, and the movement of the piston causes the crankshaft to rotate and output the torque. 6) Exhaust ports and valves: The exhaust gas generated after the combustion of the mixed gas is discharged from the exhaust valves, and the exhaust valves mainly control the exhaust gas. The exhaust ports are located between the exhaust valves and the exhaust manifold. The model has two exhaust ports and valves on each cylinder, and the four cylinders have a total of eight exhaust ports and valves. 7) Exhaust manifold: The exhaust manifold mainly collects the exhaust gas of each cylinder and introduces it into the exhaust main. The model has four exhaust manifolds to reduce the interaction of gases within the exhaust pipe. 8) Exhaust after-treatment: exhaust aftertreatment mainly treats exhaust gas through a three-way catalytic converter to reduce CO, NOx and HC emissions. Finally, the treated exhaust gas is discharged into the atmosphere through the engine outlet. Fig. 4 (b) shows the power cell used in the calculation [45]. The calculated results are illustrated in Fig. 5 [45]. In Fig. 5 [45], it is clearly illustrated the engine torque, power output and fuel economic results by using four blends fuels (E25, E100, BU40, E0), and the advantages and disadvantages of each fuel are clearly displayed. It can be seen that the BU40 engine power output and fuel consumption are between the E100 and E0, and is very close to the E25 engine.

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(a). the established engine model [45]

(b). the schematic of the power cell used in the calculation [45] Fig. 4 The established engine model and the schematic of the power cell used in the calculation [45]

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Fig. 5 Comparison of results of engine performance for different fuels (E0, E25, E100 and BU40), four cylinders engine, aspirated [45] 23

Journal Pre-proof Nowadays, as petroleum shortages and air pollution from vehicles emissions increase, researchers and engineers around the world are looking for clean alternative fuels [46]. Butanol was considered as an excellent clean alternative fuel for gasoline engines, it has many unique advantages to NG, LPG, carbinol and ethanol [46], Yang et al [46] investigated the dyno test of gasoline engine fueled with butanol-gasoline blends. It was found that when the butanol concentration was below 20% by volume, the engine power level could maintain, and the engine needs not any necessary modifications. The combustion performance of dual-injection using bio-butanol DI and gasoline port fuel-injection was studied by Feng et al [47] in a SI engine. PFI and DI dual-injection system with varying ratio of bio-butanol was developed in study. It was found that with optimum spark timings, dual-injection extended engine IMEP; with the increase of bio-butanol DI mass fraction, nonlinear knock resistance occurred; dual-injection improved fuel efficiency by decreasing energy consumption rates. Huang et al [48] studied on the application of butanol/gasoline blends fuel on a scooter engine. In study [48], different volume percentage of butanol/gasoline blends fuel, B10, B20, B40, B60, B80 and B100 were applied on a 125 cc scooter, and higher than B60 blend fuel was declared as high butanol concentration blend fuel. The engine experimental results showed that the B100 fuels could increase engine performance under engine 4000 and 6000 rpm. In addition, B10 and B20 fuels could improve not only BSFC, but also emissions under stoichiometric air-fuel ratio. However, because of high butanol concentration, engine run unsteadily, which might be caused by bad spray atomization due to high viscosity under ambient temperature. 24

Journal Pre-proof Bata et al [49] evaluated the butanol as an alternative fuel for IC engine, and the evaluation was made by measuring the performance of a 4-cylinder automotive SI engine with 4 different fuels. It was found that as the addition of butanol fuel, the proportion reached 20%, and the engine’s thermal efficiency was reduced by only 2.5 percent (the BSFC was increased by about 6.5%). The results showed that butanol had better advantages than methanol and ethanol (and correspondingly lower BSFC). Feng et al [50] studied the combustion performance of dual-injection using bio-butanol DI and gasoline port fuel-injection in a SI engine. The results showed that the dual injection extended ignition time, and with the increase of the bio-butanol mass fraction, nonlinear knocking occurred; double injection improved fuel efficiency by reducing energy consumption. Thomas et al [51] investigated the effect of compression ratios on performance and emissions of SI engine fueled with gasoline and bio-butanol blends at different loads. The results showed that with the increase of the full load compression ratio, the BTE increased, especially when using the fuel with better anti-knock performance, the concept of VCR technology could improve the partial load efficiency of the SI engine. Both the thermodynamic potential and the impact on emissions were investigated by Niass et al [52]. It was found that the RON and MON values of the gasoline/butanol mixture and the heat of vaporization were both significantly increased. Therefore, pre-ignition could increase the high full load efficiency, resulting in a more favorable combustion center. The performance of a “downsized” SI engines, fueled with gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed by Galloni et al [53]. It was found that 25

Journal Pre-proof as the alcohol content increased, the torque and thermal efficiency slightly decreased; at part load, as the alcohol content increased, spark advance did not changed. 3.2.2 The combustion performance of bio-butanol/gasoline engines Pechout et al [54] studied the effect of higher content bio-butanol blends on combustion, exhaust emissions and catalyst performance in an un-modified SI vehicle engine. It was found that compared with gasoline, the duration of the early combustion stage for butanol blends was slightly shorter, and the length of the main phase of combustion was generally comparable. With higher butanol content, the flame propagation was faster. In pursuit of reducing dependencies on foreign oil coupled with U.S. renewable fuel standards, and an overall focus and interest in greenhouse gas emissions, investigations continue on feasibility of replacement biologically derived fuels such as ethanol and butanol. Butanol has specific energy content closer to that of gasoline, suggesting open-loop engines may be less prone to negative effects of increased biologically derived fuel concentrations in gasoline [55]. Yang et al [56] studied the performance of an engine fueled with butanol/gasoline blends of different mixing fractions, it analyzed based on chemical reaction dynamics theory. It was found that butanol was a very promising alternative fuel with great potential for saving energy, which has been observed a reduction of 14% in brake specific energy consumption and reduction emissions. The evolution of SI flame kernels of butanol/gasoline blends was studied by Merola et al [57] based on detailed UV-visible optical characterization. A post-detection procedure was applied to evaluate flame kernel areas evolution, and its correlation to the MFB. UV-visible 26

Journal Pre-proof natural emission spectroscopy was applied to investigate the formation, and the evolution of the main compounds characterizing the SI combustion process. The combustion characteristics of gasoline engine with independent intake port injection and direct injection systems for bio-butanol and gasoline was studied by He et al [58], in study [58], different injection approaches for bio-butanol and gasoline combustion were carried out. The results showed that bio-butanol had a high proportion of total fuel energy, which improved the combustion stability of fuel; bio-butanol promoted ignition and shortened combustion time; different fuel injection methods had less influence on average effective pressure. Serras-Pereira et al [59] investigated the characteristics of sprays and combustion by using ethanol, butanol, iso-octane and gasoline fuels in a DISI engine. As countries' regulations on emissions regulations become more stringent, the current conventional fuel vehicles are under tremendous pressure, one of the best ways to deal with them is to find alternative fuels for vehicles to meet emissions requirements. In study [60], the early combustion processes of regular gasoline and alternative fuels, including ethanol and butanol, were studied by simultaneously, the in-cylinder pressure and the high-speed flame images were recorded in a single-cylinder SI DI engine [61]. The experimental results showed that there was a reasonable correlation between the heat release rate and the flame area at the initial stage of combustion process. The relationship between the flame area and the heat release of gasoline, ethanol, and butanol could also be distinguished by the properties and characteristics of each fuel. The plasma assisted ignition effects on a DISI engine fueled with gasoline and butanol were studied by 27

Journal Pre-proof Irimescu et al [61] under lean conditions and with EGR. The results showed that the use of an alternative ignition system could improve the stability of the engine, and the effects of butanol were related to its different chemical properties. Wei et al [62] studied knocking combustion characteristics of bio-butanol gasoline blends in a DISI engine. It was found that bio-butanol showed better knock resistance characterized by improved KLST; Compared with gasoline fuel, Bu20 (mixed fuel with 20% bio-butanol content) had a slightly lower anti-knock performance; the knocking oscillation frequency was related to the resonance mode of the combustion chamber. The performance in a turbocharged SI engine, firing with butanol/gasoline blends, was investigated by Scala et al [63] based on numerical analysis. It was found that the butanol content could reduce the combustion duration. Irimescu et al [64] studied the effects of coolant temperature on air-fuel mixture formation and combustion in an optical DI SI engine fueled with gasoline and butanol. It was found that at low load, compared with gasoline, alcohol performed slightly better, while at the time of opening the throttle valve, the opposite was recorded; the effect of coolant temperature on butanol was more pronounced. Knocking combustion in a SI engine fuelled with butanol/gasoline blends were measured by Merola et al [65] based on in-cylinder spectroscopic. UV-visible natural emission spectroscopy was applied in study [65]. It was found that the flame kernel was detected early for butanol/gasoline blends than gasoline; spectral evidence of soot precursors was allowed to confirm the influence of fuel injection mode on the fuel deposits burning; the emissions of OH radicals at 325 nm may be considered a good knocking optical 28

Journal Pre-proof indicator. Deng et al [66] carried out the heat release analysis of bio-butanol/gasoline blends in a high speed SI engine, the impacts of ignition timings, butanol blend ratios, engine loads, and fuel/air compositions on heat release were studied. It was found that butanol could provide higher knock resistance, the spark timings could be advanced, and engine load had stronger impact on combustion process than speed or fuel type. 3.2.3 The emissions performance of bio-butanol/gasoline engines Hergueta et al [67] studied the effects of butanol/gasoline blends and EGR technique on GDI engine emissions, the schematic of the engine and instrumentation set up is illustrated in Fig. 6 [67], an example of the TEM micrograph of particles collected from the GDI engine exhaust for both fuels is shown in Fig. 7 [67]. The results showed that B33 ( 33% v/v of butanol ) fuel and EGR improved engine emissions and thermal efficiency; B33 reduced gaseous and particulate emissions without affecting primary particle diameter; the BTE was not affected from the incorporation of butanol in gasoline.

Fig. 6. Schematic of the engine and instrumentation set up [67] 29

Journal Pre-proof

Fig. 7. TEM micrographs of PM at 60 Nm/2100 engine condition: a) B33 and b) Gasoline [67]

Merola et al [68] investigated the early flame development in a DI SI engine fueled with bio-butanol and gasoline by using optical diagnostics. It can be found that compared with gasoline, butanol induced higher flame contour distortion, especially in lean case; butanol ensured lower smoke opacity and strong reduction in NOx concentrations. Regalbuto et al [69] investigated the butanol isomer combustion in SI engines. In [69], three isomers (bio-butanol, iso-butanol, and sec-butanol) of four butanol isomers (bio-butanol, iso-butanol, and sec-butanol) were used. The three isomers were mass-mixed using 30% butanol and 70% gasoline as raw materials. These fuel mixtures were tested on a single cylinder jet silicon engine. The study found that bio-butanol, iso-butanol, and sec-butanol performed similarly in terms of braking torque and peak pressure in the cylinder, but the performance in terms of emissions was quite different. While sec-butanol showed the highest UHC emissions, iso-butanol showed the highest CO emissions, and bio-butanol showed the highest NOx emissions. The study with different butanol portions in gasoline was studied by 30

Journal Pre-proof Czerwinski et al [70] on the two cylinder SI engine, and several parameters on engine dynamometer changed. In the steady state operation, it was found that Bu-blends could reduce the emissions of CO, HC, NOx in untreated exhaust gas, and it had a very little influence on catalytic conversion rates of the 3-way-catalyst. At lower engine part load, “Bu” shortened the inflammation lag and reduced the combustion cyclic dispersion. Nevertheless, as the engine loads and “Bu” proportions were higher, the advantage disappeared. Williams et al [71] studied the impacts of butanol and other bio-components on the thermal efficiency of prototype in conventional engines. The results showed that the thermal efficiency of the butanol blends was consistent with the increase of the octane number of the base gasoline, and had a measurable gain; the crude oil-derived gasoline of butanol blends had the largest volume and the lowest NOx emission. Liu et al [72] studied the feasibility of low-concentration butanol as motorcycle fuel. The study conducted an immersion test on 50% bio-butanol gasoline (nB50) and rubber, thermoplastics and aluminum alloys commonly used in motorcycle engine fuel systems. The materials compatibility of bio-butanol gasoline (nB50) and rubber, thermoplastics and aluminum alloys were studied. The combustion characteristics of 20% bio-butanol gasoline (nB20) and ordinary gasoline were compared. The results showed that as fuel on gasoline-injected motorcycles, there was no hidden trouble in the use of bio-butanol gasoline (nB20). However, the increase in NOx emissions was a common alcohol replacement fuel problem on motorcycles. The experimental and kinetic investigation on soot formation of bio-butanol/gasoline blends was carried out 31

Journal Pre-proof by Liu et al [73], and in study [73], the laminar coflow diffusion flame, the soot volume fraction of bio-butanol/gasoline in laminar diffusion flame was measured based on the TI-LII technique. The results showed that with the increase of bio-butanol content, the effects of bio-butanol on soot emission reduction was enhanced. As the addition of bio-butanol, the concentration of aromatic hydrocarbons in gasoline had a greater impact on the reduction of soot; OH and HO2 had the important indirect effects on the formation of soot precursors. Chen et al [74] studied the thermodynamic process and performance of high bio-butanol/gasoline blends fired in a GDI production engine running WOT, and 30% and 50% bio-butanol were added into a GDI engine running WOT. The results showed that high bio-butanol/gasoline blends had the effects of promoting combustion, lowering exhaust temperatures, and reducing NOx and CO2. Yu et al [75] studied the effects of gasoline/bio-butanol blends on gaseous and particle emissions from a DI SI engine. The results showed that as the addition of bio-butanol, it could effectively reduce the number of particles in the nucleation mode, and increase the number of particles in the nucleation mode; the 20% bio-butanol blend had the smallest total particle size under enrichment conditions. Feng et al [31] studied the combustion and emissions on motorcycle engine fueled with butanol/gasoline blends. It was found that the butanol/gasoline blend had higher blast resistance; the butanol/gasoline blend fuel was more highly efficient, and engine torque, BSEC, CO, HC, and O2 emissions were also better. Wang et al [76] studied the combustion and particle emissions of bio-butanol and gasoline based on different 32

Journal Pre-proof injection approaches in a GDI engine equipped with dual-injection system. It was found that gasoline blended with bio-butanol could reduce PN and increase IMEP of GDI engine; compared with GDI engine, bio-butanol/gasoline dual injection could effectively decrease PN; the bio-butanol mixed fraction had a different effect on the particle distribution. Singh et al [77] studied the technical feasibility of butanol/gasoline blends for powering medium-duty transportation SI engine. The results showed that the NO, CO and smoke emissions of butanol blends were lower; the HC mass emissions of high butanol blends were lower than that of gasoline; the combustion characteristics of butanol blends were basically the same as those of gasoline. Elfasakhany [78] investigated the emissions and performance of an IC engine fueled with gasoline and gasoline/bio-butanol blends. The study found that engine performance and emissions depended on engine speed and mixing ratio; CO and UHC for mixed fuels were up to 3000-3100 r/min; the higher the proportion of bio-butanol, the lower the emissions and performance. The combustion performance and particle number emissions of a GDI engine fueled with gasoline/butanol blends in steady state modes was studied by Li et al [79]. Each isomer was tested at blend ratios from 10% to 50% by volume. The results showed that as the butanol content increasing, the particle number concentration was reduced significantly for all the isomers. Sec-butanol/gasoline yielded the lowest particle number concentration, closely followed by bio-butanol/gasoline, and then iso-butanol/gasoline, tert-butanol/gasoline yielded the highest particle number concentration. As the addition of butanol, the 33

Journal Pre-proof particle mean diameter decreased slightly. In study [80], experiments were carried out in an optical single-cylinder direct injection SI engine fuelled with bio-butanol and gasoline, alternatively. In order to track the combustion process, different optical diagnostic methods were used from ignition to flame front propagation: cyclic analytical visualization, chemiluminescence and natural emission flame spectroscopy in the UV-V range. Optical data was associated with traditional thermodynamic analysis and exhaust emission measurements. It was found that for gasoline, the effect of dispensing (ie, two injections per cycle) was relatively negligible, while for alternative fuels, there was a significant difference from one injection to two injections; the butanol mixture was blended into a non-oxygenated reference gasoline with a RON of 97, and the butanol blending ratios were 15% and 30% by mass. 3.3 Engine using bio-butanol/hydrogen blends as fuel As the addition of hydrogen fuel, the performance of the SI bio-butanol engine can be effectively improved. The bio-butanol fuel can be mixed with hydrogen in engine, for example, it can be mixed with hydrogen (eg, 85% bio-butanol and 15% hydrogen) or many other percentages. Table 3 shows the physical and chemical properties of bio-butanol and hydrogen [34, 45]. Hydrogen has a high thermal diffusivity and mass diffusivity, and hydrogen enrichment can improve the formation of the fuel/air mixture in the engine intake manifold. Meanwhile, due to the high flame velocity and large flammability limit of hydrogen, the enrichment of hydrogen can also promote the turbulent combustion of conventional fuel engines [81-84].

34

Journal Pre-proof Table 3 the properties of bio-butanol and hydrogen [34, 45] Fuel property

Bio-butanol

Hydrogen

Chemical structure

C4H 9OH

H2

Oxygen content by mass (%)

21.5%

0

Density at NTP (kg/l)

0.81

0.00008

Lower Heating Value (MJ/kg)

33.1

120

Volumetric Energy Content (MJ/l)

29.2

0.010

Stoichiometric Air to Fuel Ratio (kg/kg)

11.2

34.2

Energy per Unit mass of air (MJ/kg)

3.51

Research Octane Number

98

130 (  =2.5)

Motor Octane Number

85

NA

Sensitivity (RON-MON)

13

NA

Boiling point at 1 bar (℃)

118

-253

Heat of vaporisation (kJ.kg)

582

461

Reid Vapour Pressure (psi)

18600

NA

Mole ratio of products to reactants

0.852

Flammability Limits in Air (  ) Laminar flame speed at NTP,

 =1 (cm/s)

Adiabatic Flame Temperature (℃) Specific CO2 Emissions (g/MJ)

1.4-11.2

0.15-10.57

58.5

210

2340

2117 0.00

The effects of bio-butanol and hydrogen in rotary engines were study in [85-90]. Su et al [85] studied the idle performance of a hydrogen/bio-butanol in a rotary engine. The results showed that as the addition of hydrogen, it could reduce HC and CO emissions. It was also found [86] that as the addition of hydrogen, it could reduce NOx emissions by lean burn strategy. The schematic of the original engine is illustrated in Fig. 8 [87, 88]. The sketch of experimental system is shown in Fig. 9 [87, 88], injector 11 is for hydrogen injection and injector 9 is for bio-butanol injection, and more details are illustrated in Table 4 [87, 88]. Fig. 10 illustrates the BTE results of different ignition timings [87]. It was found that as ignition was advanced, the BTE 35

Journal Pre-proof firstly increased and then decreased for both BRE and HBRE. Nevertheless, the excessive spark advance leads to sharp increase in negative compression work, finally dropping brake power and BTE. It also found that as the H2 enrichment, the BTE was increased, moreover, the CO, HC and NOx emissions also improved [87, 88].

Fig. 8. The schematic of the original engine [87, 88]

Fig. 9. The sketch of experimental system [87, 88] 36

Journal Pre-proof Table 4 Illustration of the experimental system [87, 88] Number

Explanations

Number

Explanations

1

Container for hydrogen

13

HECU

2

Pressure regulation for hydrogen

14

Spark plug with pressure transducer

3

Pressure meter for n-butanol

15

Charge amplifier

4

Volumetric flow meter for

16

A/D converter

hydrogen 5

Backfire arrestor

17

KiBox

6

Tank of n-butanol

18

Oxygen sensor

7

Mass flow meter for n-butanol

19

Lambda analyzer

8

Pump for n-butanol

20

Exhaust sampling tube

9

Injector for n-butanol

21

Emissions analyzer

10

Mass flow meter for air

22

Tooth trigger wheel

11

Injector for hydrogen

23

Photoelectric magnetic sensor

12

Calibration computer

Fig. 10. BTE versus ignition timings [87]

Zhang et al [90] investigated the lean combustion performance of a hydrogen-enriched bio-butanol engine. The results showed that as the addition of hydrogen, it could increase the thermal efficiency of the bio-butanol engine, and prolong the lean limit of the bio-butanol engine, and shorten the combustion time of the bio-butanol engine. Meng et al [91] studied the combustion and emission 37

Journal Pre-proof characteristics of bio-butanol engine with hydrogen direct injection under lean burn condition. It was found that as the addition of hydrogen, the bio-butanol engine’s power and fuel economy were significantly improved, and HC and CO emissions were significantly reduced. Raviteja and Kumar [92] studied the effects of hydrogen addition on the performance and emission parameters in an SI engine fueled with butanol blends at stoichiometric conditions. Combustion analysis results showed that the delay time was shortened, the combustion duration was short, the cylinder pressure was increased, the temperature was increased, and the combustion effect was improved. HC and CO emissions enriched were reduced with 10% hydrogen by an average of 60%, while NO emissions almost doubled. 3.4 Engine using bio-butanol/methanol/ethanol/gasoline blends as fuel Table 5 shows the physical and chemical properties of bio-butanol, methanol and ethanol [34, 41]. Irimescu et al [93] investigated the effects of butanol and ethanol fueling on combustion and PM emissions in an optically accessible DISI engine. Measurements were performed on a wall guided power unit with optical accessibility,

which

was

fueled

with

gasoline, ethanol, and butanol

fuels.

Thermodynamic results were combined with exhaust gas measurements, particle size distribution and cycle-resolved imaging. The schematic representation of the experimental setup and detail of the optical accessibility are illustrated in Fig. 11 [93, 94]. Fig. 12 illustrates the selection of images detected during late combustion [93]. Through the complete characterization of thermodynamic, exhaust and visualization data, the mechanism of fuel jetsimpinging on the combustion chamber walls was 38

Journal Pre-proof identified as the main influence. The alcohols’ higher latent heat of evaporation and low saturation pressure were recognized as determining fuel properties that induced the observed changes. Table 5 the properties of methanol, ethanol and bio-butanol [34, 41] Fuel property

Methanol

Ethanol

Bio-butanol

Chemical structure

CH3OH

C2H5OH

C4H 9OH

Oxygen content by mass (%)

50

34.8

21.5%

Density at NTP (kg/l)

0.79

0.79

0.81

Lower Heating Value (MJ/kg)

20.09

26.95

33.1

Volumetric Energy Content (MJ/l)

15.9

21.3

26.91

Stoichiometric Air to Fuel Ratio (kg/kg)

6.5

9

11.2

Energy per Unit mass of air (MJ/kg)

3.12

3.01

Research Octane Number

109

109

98

Motor Octane Number

88.6

89.7

85

Sensitivity (RON-MON)

20.4

19.3

13

Boiling point at 1 bar (℃)

65

79

118

Heat of vaporisation (kJ.kg)

1100

838

582

Reid Vapour Pressure (psi)

4.6

2.3

18600

Mole ratio of products to reactants

1.061

1.065

Flammability Limits in Air (  )

0.23-1.81

0.28-1.91

1.4-11.2

42

40

58.5

Adiabatic Flame Temperature (℃)

1870

1920

2340

Specific CO2 Emissions (g/MJ)

68.44

70.99

Laminar flame speed at NTP,

 =1 (cm/s)

39

Journal Pre-proof

Fig. 11 The schematic representation of the experimental setup and detail of the optical accessibility [93, 94]

Fig. 12 The selection of images detected during late combustion [93] 40

Journal Pre-proof Li et al [95] investigated the combustion, performance and emissions of methanol, ethanol and butanol in a SI engine. It was found that as the addition of these alcohols, combustion phasing was advanced; butanol/gasoline blends showed the lower brake specific fuel consumption, ethanol/gasoline blends produced the lowest UHC emission, and methanol/gasoline blends showed the lowest NOx emission. Moxey et al [96] studied the flame development of butanol and ethanol in an optical SI engine. High-speed natural light (or chemiluminescence) imaging and simultaneous in-cylinder pressure data measurement and analysis were used in study [96]. As a possible mainstream fuel additive, the fundamental influence of both low and high carbon content in alcohol fuels was study on turbulent flame propagation and subsequent mass burning. The results showed that the butanol blend tested was similar to the ethanol blend tested in terms of combustion duration, pressure development and flame radius development. Elfasakhany

and

Mahrous

[97]

investigated

the

performance

of

bio-butanol/methanol/gasoline blends in SI engines. Four test fuels (namely 0, 3, 7 and 10 volumetric percent of bio-butanol/methanol blends at equal rates, e.g., 0%, 1.5%, 3.5% and 5% for bio-butanol and methanol, in gasoline) were investigated in an engine speed range of 2600-3400 r/min. In addition, the dual alcohol (methanol and bio-butanol)/gasoline blends were compared with single alcohol (bio-butanol)/ gasoline blends (for the first time) as well as with the neat gasoline fuel in terms of performance and emissions. The experimental results showed that compared with the results of neat gasoline and single alcohol/gasoline blends, as the addition of low 41

Journal Pre-proof content rates of bio-butanol/methanol to neat gasoline, the engine performance and exhaust gas emissions had an adverse effect; in particular, there was a reduction in engine volumetric efficiency, brake power, torque, in-cylinder pressure, exhaust gas temperature and CO2 emissions, and there was an increase in concentrations of CO and UHC emissions for the dual alcohols. Exhaust emissions and performance of ternary iso-butanol/bio-methanol/gasoline and bio-butanol/bio-ethanol/gasoline fuel blends in SI engines have been studied by Elfasakhany [98]. It was found that compared with neat gasoline, both ternary fuel blends showed lower performance. iBM fuel blends improved performance and pollutant emissions than the nBE one. Compared with gasoline fuel, both fuel blends achieved the goal of more green sustainability. Sharudin et al [99] investigated the effects of iso-butanol additives on SI engine fueled with methanol/gasoline blends. It was found that as the addition of iso-butanol to methanol/gasoline blends, the brake power was improved. For methanol/gasoline blends with iso-butanol, CO and HC emissions decreased, and NOx and CO2 emissions were higher. The performance and engine-out emissions (NOx, CO, HC and PM) of methanol, ethanol and butanol were examined on a four cylinder 2.4 DI production engine, and were compared with those neat gasoline [100]. It was found that when running on alcohol fuels, the BTE was significantly better than with gasoline while emitting fewer emissions. In a knock limited case for gasoline, the BTE on methanol was more than 5 percentage points better than on gasoline. 3.5 Engine using bio-butanol/acetone/ethanol/gasoline blends as fuel 42

Journal Pre-proof ABE, the intermediate product in the ABE fermentation process for producing bio-butanol, is being studied as an alternative fuel. Because it not only preserves the advantages of oxygenated fuels, but also lowers the cost of fuel recovery for individual component during fermentation. To reduce the energy consumption of a downstream recovery unit, the feasibility of pervaporative concentration of organic compounds from an ABE mixture was investigated [101]. The study of experimental comparison of ABE and IBE as fuel candidate was carried out by Li et al [102] in SI engine. In study [102], the combustion and emissions performance were investigated. Fig. 13 shows the engine setup, the engine used in the experiments was a single-cylinder PFI SI engine with identical cylinder geometry to 2000 Ford Mustang Cobra V8 engine [102]. It was found that compared with ABE, IBE seems to be more attractive for fuel application in SI engine. Fig. 14 illustrates the engine performance for G100, ABE10 and IBE10 under various mixture concentrations and engine loads [102]. It can be seen from Fig. 14 [102] that at rich conditions, compared with gasoline, ABE10 and IBE10 enhanced the BTE by 0.9% and 0.2-0.4%. In addition, at lean conditions, it was noted that IBE10 enhanced the BTE by 0.2-0.8%, because when the combustion phasing was close enough, the negative effect of improper combustion phasing of IBE10 on the BTE was offset by the improved combustion quality. Moreover, compared with ABE10, IBE10 decreased the BSFC by 0.7-2.3%. Fig. 15 illustrates the engine emissions for G100, ABE10 and IBE10 under various mixture concentrations and engine loads [102]. It can be seen from the Fig. 15 [102] that compared with gasoline and ABE10, the CO emission was reduced by 0.6-2.7% 43

Journal Pre-proof and 0.9-7.3% when using IBE10. Compared with gasoline and ABE10, the UHC emission was decreased by 4.4-6.1% and 12.4-25.1% at 3 bar BMEP, and 3.9-22.6% and 3.3-9.6% at 5 bar BMEP. Compared with gasoline, although a higher oxygen concentration was provided, the decreased combustion temperature caused a 0.5-9.4% and 4.3-13.9% decrease of the NOx emission for ABE10 and IBE10.

(a)

(b)

Fig. 13. Engine setup [102] 44

Journal Pre-proof

Fig. 14. Engine performance for G100, ABE10 and IBE10 under various lambda and engine loads [102]

Fig. 15. Engine emissions for G100, ABE10 and IBE10 under various lambda and engine loads [102]

45

Journal Pre-proof With the development of advanced ABE fermentation technology, the volumetric percentage of acetone, butanol and ethanol in the bio-solvents could be precisely controlled [103]. Nithyanandan et al [103] investigated the impact of acetone on the performance and emissions of ABE and gasoline blends in an SI engine. It was found that compared with gasoline fuel, the combustion characteristics and emission behavior of ABE was improved. ABE (6:3:1) showed combustion phasing closest to gasoline, accompanied by an improved BTE. Due to incomplete combustion, the HC and CO emissions could be increased by increasing bio-butanol contents. On the other hand, ABE (6:3:1) had good effect on HC emissions [104]. An experimental investigation of the performance, combustion and emission characteristics of a port fuel injection SI engine fueled with ABE/gasoline blends was carried out by Li et al [105]. By testing different ABE/gasoline blends with varying ABE contents (0 vol%, 10 vol%, 30 vol% and 60 vol% referred to as G100, ABE10, ABE30 and ABE60), ABE formulations (A:B:E of 1:8:1, 3:6:1 and 5:4:1 referred to as ABE (181), ABE (361) and ABE (541)), and water contents (0.5 vol% and 1 vol% water referred to as W0.5 and W1), it was found that ABE (361) 30 performed well in terms of engine performance and emissions, including BTE, BSFC, CO, UHC and NOx emissions. The experimental study on the laminar burning velocities and Markstein lengths of ABE mixtures and its components was performed [106] in a constant-volume combustion vessel. A detailed mechanism was applied to simulate the 1-D premixed laminar flames of ABE mixtures and its components. The results showed that the 46

Journal Pre-proof laminar burning velocities of ABE mixtures were slower than those of ethanol, faster than those of acetone, and close to those of bio-butanol. Moreover, the Markstein lengths of ABE mixtures were close to those of bio-butanol, indicating that the instability of laminar flames of ABE mixtures was also similar to that of bio-butanol. Based on kinetic analysis, it was found that the consumption channels of acetone, ethanol and bio-butanol in single component fuel/air flame and ABE/air flame were very close. If ABE could be directly used for clean combustion, the separation costs would be eliminated which save an enormous amount of time and money in the production chain of bio-butanol. Li et al [107] studied the regulated and unregulated emissions from a SI engine fueled with ABE/gasoline blends. It was found that the regulated and unregulated emissions could be improved by using the ABE/gasoline blends. 3.6 Engine using bio-butanol/water/isopropanol/ethanol/gasoline blends as fuel Table 6 the properties of methanol, diesel , isopropanol and bio-butanol Fuel property

Ethanol

Gasoline

Isopropanol

Bio-butanol

Molecular formula

C2H5OH

C5-12

C3H8O

C4H 9OH

Molecular weight

46

95 ~ 120

60.09

74.11

0.7851

0.81

Specific gravity % of Oxygen by weight

34.8

0

26

21.5%

Heat of evaporation (kJ/kg)

838

310

666

582

Cetane Number

8

0 ~ 10

-

25

Lower Heating Value (kJ/kg)

26.95

445000

24040

33100

Table 6 shows the physical and chemical properties of bio-butanol, gasoline, bio-butanol and isopropanol. Due to its favorable physicochemical properties, 47

Journal Pre-proof bio-butanol has attracted great attention as a potential alternative fuel in IC engines. Water containing IBE can be used as an alternative fuel of SI engine. Li et al [108] carried

out

the

experimental

evaluation

of

water-containing

isopropanol/bio-butanol/ethanol and gasoline blends as a fuel candidate in SI engines. The effects of IBE and water addition on combustion, performance, and emissions characteristics were first investigated at stoichiometric condition. The results showed that due to its eco-friendly production method, water-containing IBE could be used as a fuel candidate in SI engine, and was potential to improve energy efficiencies and reduce emissions. 4. Bio-butanol fuel used on CI engines 4.1 Engine using neat bio-butanol as fuel Yanai et al [109] investigated the characteristics of the combustion, emissions and thermal efficiency in a direct injection diesel engine fueled with neat bio-butanol. An engine test was performed on a single-cylinder four-stroke DI diesel engine. The test results showed that compared with diesel fuel, the ignition delay of bio-butanol fuel was significantly longer. Bio-butanol generally released heat rapidly in a short period of time, resulting in an excessive rate of pressure rise. It also found that bio-butanol fuel had the potential to achieve ultra-low emissions. 4.2 Engine using bio-butanol/diesel blends as fuel For diesel engines, alcohols, especially bio-butanol, are receiving increasing attention because they are oxygenated and renewable fuels. The bio-butanol fuel can be mixed with diesel in the engine or mixed with diesel (eg, 85% bio-butanol and 48

Journal Pre-proof 15% diesel) or many other ratios. Bio-butanol is a renewable biofuel that is considered a promising alternative to diesel engines. When bio-butanol is mixed with diesel for pilot ignition of natural gas engines, low emissions can be achieved without sacrificing thermal efficiency. However, the high blending ratio of bio-butanol is limited by the longer ignition delay caused by higher latent heat and octane number, which limits the improvement of its emission characteristics. The possibility of increasing the butanol blend ratio by adding EGR was investigated in [110]. The results showed that the use of thermal EGR could increase the ignition range of the bio-butanol blend ratio from 40% to 60%. At a bio-butanol ratio greater than 30%, the addition of an appropriate proportion of hot EGR could increase thermal efficiency. In general, optimization of NOx and CO thermal efficiency and emission characteristics could be achieved by adding 5% and 10% hot EGR. The study also found that when the bio-butanol blend ratio was less than 30%, the addition of hot EGR could improve the emission of polycyclic aromatic hydrocarbons. As the addition of bio-butanol, it could reduce the emission of polycyclic aromatic hydrocarbons above two rings. [110]. For reducing smoke and improving the performance of a butanol/diesel common rail dual fuel engine, the multiple injection strategies were studied by Yadav and Ramesh [111]. Fig. 16 shows a schematic view of the experimental setup [111], and the illustration of the setup is shown in Table 7 [111]. The engine was coupled to an eddy current dynamometer with closed loop control of speed. An in-house developed field-programmable gate array based open engine controller along with commercially 49

Journal Pre-proof available driver modules was used to vary the diesel fuel rail pressure, injection timings and number of diesel injection pulses. The results showed that the main post injection could improve the energy efficiency of the butanol dual fuel engine. Meanwhile, the smoke, NO and fuel consumption could be decreased. Auto-ignition of butanol prior to diesel injection limited the energy share of butanol. Fig. 17 [111] shows the variation in smoke emission with butanol to diesel energy share at different main to post offset at 75% and 100% loads. Due to its effects on in-cylinder mixing and temperature, the post injection of diesel had a significant reduction in smoke emission. However, beyond a BDES of 20% the smoke level increased with SPI of diesel as the butanol air mixture became richer, and started to auto ignited which created a high temperature environment when the diesel was injected.

Fig. 16. The schematic view of the experimental setup [111]

50

Journal Pre-proof Table 7 Illustration of the experimental setup [111] Number

Explanations

Number

Explanations

1

Air filter

13

Temperature indicator

2

Intake manifold

14

Boost pressure indicator

3

Butanol port fuel injectors

15-17

Exhaust gas analyzers

4

Diesel solenoid direct injector

18

Turbocharger

5

Diesel fuel tank

P.

In-cylinder pressure transducer

6

Butanol fuel tank

m1

Air flow rate

7

Charge amplifier

m2

Butanol fuel flow rate

8

Crank angle encoder

m3

Diesel fuel flow rate

9

Data acquisition system

m4

Intake charge temperature

10

Intake manifold pressure sensor

m5

Exhaust gas temperature

11

Speed indicator

m6

Exhaust gas sample for analyzer

12

Torque indicator

Fig. 17 Variation in smoke emission with butanol to diesel energy share at different main to post offsets at 75% and 100% loads [111]

In order to investigate soot formation, concentration and morphology differences affected by adding butanol to diesel, an experimental study was performed to compare in-flame soot morphology of diesel and butanol/diesel blends in a constant volume combustion chamber [112]. The results showed that as the addition of butanol , it could promote fuel atomization, optimize fuel/air mixing, delay ignition, accelerate combustion, and inhibit soot formation. Compared with pure diesel, the number and 51

Journal Pre-proof mass concentration of soot were significantly lower, the average particle size was smaller, and the geometry of soot was also changed. In order to utilize bio-butanol as an alternative fuel for diesel engines, the effects of butanol isomer, where 1-butanol, 2-butanol and iso-butanol were studied except for tert-butanol, on the combustion characteristics and exhaust emissions of butanol/gas blend was investigated by Fushimi et al [113] using a DI diesel engine without modification of engine parameters. It was found that 1-butanol was best for gas oil blending use among three isomers. In order to utilize bio-alcohols as the fuel for diesel engines, combustion characteristics of alcohol blended with gas oil were compared between ethanol and bio-butanol in a DI diesel engine [114]. It was found that compared with the ethanol blends, the smoke density of the butanol blends was smaller. For conventional diesel engines, in order to meet emission regulations, low NOx and PM emissions post-treatment systems were applied, Xie et al [115] investigated the emissions of HCCI combustion in a diesel engine fueled with butanol, and an analysis of the hydrocarbon species in the exhaust was performed. In study, the Fourier transform infrared spectroscopy was used to gain insight into the combustion characteristic of butanol in HCCI. A comparison was made with gasoline fuel to compare the reactivity of butanol in this pair of high volatility fuels. Saxena and Maurya [116] studied the effects of butanol addition on performance, combustion stability and nana-particle emissions in a conventional diesel engine. The experiments were conducted for neat diesel, 10%, 20% and 30% butanol/diesel blends on the volume basis at different engine loads. Combustion characteristics were 52

Journal Pre-proof investigated based on in-cylinder pressure measurement and heat release analysis. The results showed that as the addition of butanol in diesel, the total particle size concentration decreased. In addition, butanol mixtures were also likely to decrease CO, NO, and opaque emissions of smoke in diesel. However, as the addition of butanol in diesel, HC emission was increased. Li et al [117] investigated the mechanism of flame spread over butanol/diesel blended fuel. Several fundamental parameters of flame spread, including the flame spread rates, frequencies of flame oscillation, temperature distributions, and velocities of subsurface flow were characterized. Fig. 18 shows the schematic diagram of the flame spread experiments [117]. Fig. 19 shows the sequent images of flame front for flame spread over blended fuel with γ equal to 15% and 17.5% respectively, where γ is the ratio of butanol [117]. The flame spread characteristics of the blended fuel approach those of diesel fuel as the ratio of butanol was less than 17.5%, whereas they resemble those of pure butanol fuel with the ratio of butanol beyond 17.5%. Further, an increase in the ratio of butanol led to an increase in the flame spread rate as well as the velocity of subsurface flow.

Fig. 18. The schematic diagram of the flame spread experiments [117] 53

Journal Pre-proof

Fig. 19. Sequent pictures of flame front with 15% and 17.5% butanol [117]

Zhang et al [118] studied the combustion characteristics for partially premixed and conventional combustion of butanol and octanol isomers in a light duty diesel engine. A viable way to achieve PPC by low CN alcohol/diesel blends in a single cylinder LD engine was applied. Because of its lower combustion temperature and increased fuel/air mixing, PPC produced very low soot and NO emissions, independently of the fuels used. Gurgen et al [119] studied the prediction of cyclic variability in a diesel engine fueled with bio-butanol and diesel fuel blends using ANN. ANN model was developed to estimate cyclic variability in a diesel engine. The schematic of the experimental system is shown in Fig. 20 [119]. It was found that cyclic variability mainly depended on engine speeds and percentages of bio-butanol ratio, as the bio-butanol added to diesel fuel, cyclic variability was increased.

54

Journal Pre-proof

Fig. 20 The schematic of the experimental system [119]

In study [120], the effects of bio-butanol addition on combustion characteristics and emissions in reactivity controlled engine was investigated experimentally. The ratio of butanol/diesel blends under different EGR and premix ratios was investigated. The butanol/diesel blend was injected directly into the combustion chamber and the gasoline is injected at the inlet. The results showed that as addition of bio-butanol, it had little effect on thermal efficiency, and it reduced the optimal premixing ratio of the premix. As the bio-butanol content higher, the premixed combustion stage and CO oxidation could be improved. Han et al [121] investigated the applicability of bio-butanol as a next generation biofuel to replace diesel in CI engines for efficient operation, pollutant mitigation, and CO2 reduction. The schematic of the experimental setup for the research engine is shown in Fig. 21 [121]. An optical encoder (resolution of 0.1_CA) was used to determine the piston position and engine crank angle. A piezoelectric pressure transducer (AVL GU13P) was installed in place of the glow plug for cylinder pressure 55

Journal Pre-proof measurement. An external compressor with a conditioning unit supplies clean and dry air was used to simulate the engine intake boost. Fig. 22 [121] illustrates the n-butanol PPCI SOI sweep-exhaust emissions, NOx, smoke, THC, and CO. In Fig. 22 [121], the lean burn of a premixed cylinder charge has low flame temperatures and thus produces ultralow NOx (<20 ppm) and near-zero smoke. Similar to most low temperature combustion strategies, n-butanol PPCI has relatively high unburned HC and CO emissions.

Fig. 21 The schematic of the experimental setup for the research engine [121]

Fig. 22 The n-butanol PPCI SOI sweep-exhaust emissions, NOx, smoke, THC, and CO [121] 56

Journal Pre-proof In Fig. 23 [121], fuel spray images obtained by high speed direct imaging were compared between diesel and bio-butanol. At an injection pressure of 1200 bar, the fuel was injected into an optical chamber filled with nitrogen, and 1000 ls was injected at a pressure of 40 bar and room temperature. Compared with the diesel spray, the two fuel sprays were very similar except that the bio-butanol had a slightly narrower cone angle. As a result, it was found that since the temperature in the optical cavity was much lower than the compression temperature of the actual diesel engine, the evaporation effect was not sufficiently captured, and the bio-butanol had a lower boiling point and a faster evaporation rate than the diesel engine, thereby improving fuel/air mixing. Liu et al [122] investigated the particle emission characteristics of partially premixed combustion fueled with high bio-butanol/diesel ratio blends. The early injection PPC strategy could decrease GMD when B00 fuel was used, GMD could be decreased by employing the early injection strategy when B00 fuel was used, GMD remained in the nucleation mode area when B30 and B50 fuels were used, and the total mass concentration under the pre-injection PPC strategy was usually higher.

Fig. 23 Examples of high speed imaging bio-butanol and diesel sprays – pinj 1200 bar, background pressure 40 bar, room temperature [121]

57

Journal Pre-proof The effect of blending of bio-butanol in diesel was studied by Nayyar et al [123] on a small size VCR diesel engine. Effects of varying compression ratios, injection timings and injection pressures on performance and emissions were studied. Mathematical Modeling was applied to analyze and verify the observed results from experiments. The thermal efficiency was improved (5.54%) and emissions of smoke and NOx were decreased (59.56% and 15.96%) using B20. Optimum results for B20 were observed at higher compression ratio than that of diesel. Huang et al [124] studied combustion and emissions performance in diesel engines by fueling bio-butanol/diesel/PODE3-4 (polyoxymethylene dimethyl ethers) mixtures. The results showed that PODE3-4 could improve efficiency and decrease emissions significantly, the addition of PODE3-4 in bio-butanol/diesel blend reduced CO and THC, PODE3-4 could improve the accumulated particulate matters emission. Nabi et al [125] studied the engine performance and emissions with neat diesel and diesel-butanol blends in the 13-mode European stationary cycle. The engine performance had significant changes by using bio-butanol blends. Much lower UBHC emissions with increase in blow-by and NOx emissions were observed with bio-butanol blends. Substantial reductions in both PM and PN emissions were observed with bio-butanol blends. Satsangi and Tiwari [126] investigated the combustion, noise, vibrations, performance and emissions characteristics of diesel/bio-butanol blends driven genset engine. These bio-butanol blends showed an appreciable reduction in exhaust emissions with a little penalty on performance parameters. So, in an overall sense, bio-butanol was appeared as good alternatives to diesel for genset applications. 58

Journal Pre-proof However, while implementing this change, lubricity studies on blended fuels should be conducted, and if required appropriate additives could be used to compensate for any loss of lubricity of fuel due to presence of butanol. Cheng et al [127] investigated partially premixed combustion fueled with bio-butanol/diesel blends in a four-cylinder light-duty diesel engine. It was found that compared with the pure diesel engines, bio-butanol/diesel blends could effectively decrease the soot mass, but had little influence on the PM size distribution. Results indicated that bio-butanol/diesel blends were more conducive to expand PPCI operating conditions and improve engine performance and emissions. The diesel/gasoline/iso-butanol blends were investigated by Wei et al [128] in a CI engine. It was found that the blends with gasoline or iso-butanol produced higher HC emission, CO increased at low loads and decreased at medium and high loads with blend fuels, gasoline or iso-butanol decreased large particles but increased small particles. The impact of bio-butanol and iso-butanol as components of butanol/acetone mixture/diesel blends on spray, combustion characteristics, engine performance and emissions by Algayyim et al [129] in a DI diesel engine. It was found that compared with pure diesel fuel, spray penetration of both n-and iso-BA-diesel (butanol-acetone mixture) was slightly higher, and iso-BA/diesel blends showed high peak in-cylinder pressure and slight improvement in brake power, N-BA/diesel produced lower UHC and NOx emissions, and iso-BA/diesel blends showed much lower CO emissions. Dual fuel applications of alcohol fuels such as ethanol or butanol through port injection with direct injection of diesel could be 59

Journal Pre-proof effective in reduction of NOx. However, these dual fuel applications are usually associated with an increase in the incomplete combustion products such as HC, CO, and H2 emissions. An analysis of these products of incomplete combustion and the resulting combustion efficiency penalty was made by Dev et al [130] in the diesel ignited alcohol combustion modes. Hydrocarbon speciation and hydrogen concentration of the exhaust gas were performed, and a FTIR spectrometry gas analyzer system and a mass spectrometer were used respectively. Based on the analysis of the unburnt hydrocarbon species, it suggested that for ethanol dual fuel application, a majority of the combustion efficiency penalty could be attributed to the unburnt ethanol (between 30 to 40%). Whereas, when butanol was used, heavier HC species contributed to the combustion efficiency loss (between 30 to 50%). Zoldy et al [35] found that low butanol blends (up to 5vol% butanol content) appeared to be a good alternative for CI engine utilization: it hold the cetane number limits without extra cetane booster additivisation; it allowed nearly the same fuel consumption level along with a considerable increase in injector cleanness. The test results supported that the utilization of butanol as a diesel extender could be very advantageous, if the difficulties of flash point reduction could be handled in the logistical chain. Zhang et al [131] investigated the use on butanol or octanol blends in a heavy duty diesel engine. It was found that compared with the bio-butanol blends, the iso-butanol (because of its branched molecular structure) blends yielded slightly higher soot emissions, and the substantial potential of renewable longer-chain alcohols as 60

Journal Pre-proof components of blended diesel fuels. Jeftic et al [132] studied the effects of the engine load and the effects of different fuels (ultra-low sulphur diesel and bio-butanol) on the post injection characteristics in a modern CI engine. The results showed that post-injection was an effective method to improve the operating range of the engine load. Studies have also shown that the engine power could be increased by injecting butanol, and the peak pressure rise rate and the in-cylinder peak pressure were not affected significantly. Hydrocarbon morphological analysis indicated that the butanol after injection often produced mainly formaldehyde, ethane and unburned butanol hydrocarbons, and no hydrogen, methane, ethylene and propylene were detected under these test conditions. In order to realize a PCI engine by utilization of bio-alcohol, combustion characteristics of bio-alcohol blended with gas oil were compared between ethanol and bio-butanol in a diesel engine. The effects of the ethanol blends ratio and the butanol blends ratio on ignition delay, premixed combustion, diffusion combustion, fuel consumption and exhaust emissions such as smoke density and NOx were investigated experimentally by Yamamoto et al [133]. The results showed that butanol was more useful than ethanol, because butanol could be mixed with gas oil without the use of surfactants, and the fuel consumption and flue gas of the two mixed fuels were almost equal at the same alcohol ratio. Gao et al [134] studied the feasibility of using direct injection butanol as an ignition source for dual-fuel combustion. It was found that compared with conventional pure diesel combustion, dual fuel operation not only broadens the 61

Journal Pre-proof applicability of fuels, but also increased the potential for efficient engine clean combustion. The use of two different alcohol fuels, ethanol and butanol, in a high compression ratio diesel engine has been investigated by Gao et al [135], which can be used to examine their potential as substitutes for conventional diesel fuel when operating under low temperature combustion mode. The effects of diesel injection timings, alcohol fuel ratios, and EGR on engine emissions and efficiencies were studied at IMEP in the range from 0.8 to 1.2 MPa. Based on the obtained results, it was indicated that combustion with ultra-low smoke and nitrogen oxides emissions could be achieved with port injection of butanol at low to medium engine loads, and with port injection of ethanol at high engine loads. The main challenge encountered in these alternative fuel studies was to control the onset of butanol combustion and the peak cylinder pressure for ethanol combustion. He et al [136] studied the influence of alcohol additives and EGR on the combustion and emission characteristics of diesel engine under high-load conditions. It was found that with the increased fuel-bound oxygen contents in the blended fuels, moreover, the TPNC decreased; B40 (15% ethanol, 15% butanol and 40% butanol by volume) combined with medium EGR could be more efficient at high-load. 4.3 Engine using bio-butanol/bio-diesel blends as fuel The bio-butanol fuel can be mixed with bio-diesel in the engine or with biodiesel (eg, 85% bio-butanol and 15% biodiesel) or other ratios. Biodiesel is an alternative fuel to CI engines. Compared with diesel, it can reduce HC, CO and PM emissions. Bio-diesel has been a lucrative commodity in current global economic trade, as people 62

Journal Pre-proof are increasingly concerned about issues related to the environment and oil depletion. Bio-diesel has proven to be the next alternative renewable fuel because of its environmentally friendly, sustainable, and combustion characteristics similar to petroleum diesel. However, due to the high density and viscosity of bio-diesel, pure bio-diesel is not widely used in diesel engines. [108]. Therefore, the method of bio-butanol/bio-diesel blends was widely studied and used. Table 8 the properties of bio-butanol and bio-diesel [34, 36] Fuel property

Bio-butanol

Biodiesel

Cetane number

25

51

Lower heating value (MJ/kg)

33.1

37.5

Density (kg/m3)@20 ℃

813

871

Viscosity (mPa s) 40 ℃

2.95

4.6

Heat of evaporation (kJ/kg)

582

300

Carbon content (% mass)

65

77.1

Hydrogen content (% mass)

13.5

12.1

Oxygen content (% mass)

21.5

10.8

Sulfur content (mg/kg)

<10

Table 8 shows the physical and chemical properties of bio-butanol and bio-diesel [34, 36]. Vegetable oils, bio-diesel, bio-ethanol and biogas are some of the most popular biofuels whose applicability in CI engines is assessed. Among these fuels, bio-ethanol can be produced from a variety of biomass through fermentation and biosynthesis, and does not require additional cultivated land. Therefore, bio-alcohols can be considered as the next generation alternative fuels for automobiles [137]. Jeevahan et al [137] investigated the suitability of 1-butanol blended with bio-diesel as an alternative bio-fuel in diesel engines. Experiments were conducted in a single cylinder CI diesel engine for 4 load conditions (5 kg, 10 kg, 15 kg and 20 kg) at a 63

Journal Pre-proof constant speed of 1500 rpm. BTE and emissions of CO, NOx and HC for engines were recorded and discussed in study. Based on the engine emissions and performance, it was found that as the butanol addition to the bio-diesel, it seems to be an alternative fuel, so it could replace conventional diesel engines. Zhang et al [138] studied the combustion

characteristics

of

a

bio-butanol/bio-diesel

droplet.

Combustion

characteristics of BUT00 (pure biodiesel) and BUT50 (50% bio-butanol and 50% biodiesel by mass) were investigated using droplet suspension technology under 1 bar and 900 K. It was found that one flame was observed for BUT00 while two flames were observed for BUT50; the first and second flames of BUT50 were caused by bio-butanol and bio-diesel combustion respectively; similarity degree of BUT00 was higher than 97% before auto-ignition and 90-97% after auto-ignition. Rakopoulos [139] investigated the combustion and emissions of cottonseed oil, and its bio-diesel in blends with either bio-butanol or DEE in HSDI diesel engines, fuel consumption, exhaust smoke, NOx, CO and THC were measured. It was found that bio-butanol and DEE, which could be produced from biomass (bio-butanol and bio-DEE), as it added to the vegetable oil or its bio-diesel, the diesel engine performance could be improved. Celebi and Aydin [140] investigated the effects of butanol addition on safflower bio-diesel usage as fuel in a generator diesel engine. Binary blends of butanol/bio-diesel and ternary blends of ultra-low sulfur diesel/bio-diesel/butanol were contained 5%, 10%, and 20% butanol in volume basis. The tests were carried out on a 4 cylinder, 4 strokes, and DI diesel engine at half load operation with stable 64

Journal Pre-proof engine speed of 1500 rpm. Experimental studies have been conducted on the combustion characteristics, emissions and performance of fuels. The test results showed that the heat release rate and the in-cylinder pressure curve of the two gases were basically the same, and the total heat transfer, average gas temperature and combustion mass fraction did not change much; the ternary blends showed lower emission, and it could increase BTE up to 1.5%. An experimental study of combustion of diesel/butanol/bio-diesel blended fuels was carried out by Kilic et al [141], and effects on boiler performance and emissions were also studied in a reversal flame tube boiler. Pure diesel, blends of diesel/butanol, and blends of diesel/butanol/bio-diesel were used in the experiments. It was found that butanol/bio-diesel blended fuels decreased the size of the peak temperature zones. The CO emission was decreased significantly from 281 ppm to 4.5 ppm by using D70B30 (diesel/butanol blends). NOx emissions did not change considerably, remained by about 46-48 ppm. The efficiencies were increased from 90.5% to 90.8% by using D70B30 fuel. Zheng

et

al

[142]

investigated

the

combustion

and

emissions

of

bio-butanol/bio-diesel under both blended fuel mode and dual fuel RCCI mode. It was found that blended fuel mode showed the potential for maintaining high thermal efficiency. RCCI was capable of tolerating high bio-butanol ratio and extending upper load limits. Considering emissions and efficiency, 30% EGR rate was optimum for both modes. Zheng et al [143] investigated the combustion and emissions of dual fuel RCCI

mode

fueled

with

bio-diesel/bio-butanol, 65

bio-diesel/2,

DME

and

Journal Pre-proof bio-diesel/ethanol. It was found that the latent heat of PFI fuels had significant effect on ignition delay, bio-butanol was good to improve thermal efficiency, but the max PFI ratio was limited. The difference on RCCI combustion caused by PFI fuels was enlarged by increasing load. Wei et al [144] studied the effects of bio-diesel/ethanol and bio-diesel/butanol blends on the combustion, performance and emissions in a diesel engine. It was found that BBu blends had less adverse influence on BSFC and BTE than BE blends, BE/BBu blends had adverse effects on combustion noise and stability of power output, BE blends were better than BBu blends in decreasing NOx and PM emissions, BE blends led to higher CO and HC emissions than BBu blends. Wang et al [145] developed a reduced bio-butanol/bio-diesel mechanism for a dual fuel engine, and the developed reduced mechanism contains 170 species and 769 reactions, and the interaction of bio-butanol/bio-diesel during the ignition process was analyzed (the combined mechanism was validated against the bio-butanol experimental data including ignition delays in shock tubes and the mole fractions of species in a jet-stirred reactor). The results showed that the mechanism could be used for bio-butanol/bio-diesel dual fuel engines simulation. Ibrahim A [32] studied the performance and combustion characteristics in a diesel engine fuelled by butanol/bio-diesel/diesel

blends,

diesel,

bio-diesel,

and

blends

of

butanol/diesel/bio-diesel were tested in a diesel engine. It was found that compared with the diesel fuel, using the B50 (diesel/bio-diesel fuel blends) blend led to the highest engine efficiency and lowest fuel consumption, using butanol led a tolerable 66

Journal Pre-proof change in engine performance. Yilmaz and Davis [146] studied PAH formation in a diesel engine fuelled with diesel, bio-diesel and bio-diesel/bio-butanol blends, bio-diesel/bio-butanol blends were tested in a diesel engine for blends up to 40% bio-butanol. It was found that the toxicity of PAH emission was increased by blending more than 20% bio-butanol with bio-diesel. The LTC of PCCI with bio-butanol and cotton seed bio-diesel was analyzed by Soloiu et al [147], and it was found that compared with conventional diesel combustion, the cooling effect of bio-butanol during spray development and mixture formation increased ignition delay of bio-butanol/bio-diesel mixtures. In PCCI operation, due to the high O2 content in bio-diesel and bio-butanol, NOx and soot decreased concurrently. Tuccar G et al [148] studied the effects of diesel-microalgae bio-diesel/butanol blends on performance and emissions in diesel engine. The results showed that although butanol addition caused a slight reduction in torque and brake power values, the engine emission values were improved. Therefore, butanol could be used as a very promising additive to diesel-microalgae/bio-diesel blends. Bio-diesel is a promising alternative fuel with renewables and a wide range of raw materials. Butanol can be mixed with bio-diesel to reduce kinematic viscosity and promote fuel atomization. In study [149], bio-diesel was blended with 10% and 20% bio-butanol, and the combustion characteristics and particulate emissions of the fuel blends were tested in a turbocharged, 6 cylinders, common rail diesel engine at a constant speed of 1400 rpm under 7 engine loads. The experimental results showed that under different engine loads, the bio-butanol and bio-diesel blends had higher 67

Journal Pre-proof oxygen content of bio-butanol, but the cetane number of butanol was lower, and the burning rate was faster than that of diesel, leading to pre-combustibility strong. The addition of butanol facilitates concentrated heat release, and thus reduced burn time. As the proportion of butanol increased, the soot emissions of the butanol/bio-diesel blended fuel decreased. Yang et al [150] studied the carbonyl compound emissions in a diesel engine generator fueled with blends of bio-butanol, bio-diesel and diesel. Diesel/bio-diesel mixtures and diesel/bio-diesel/butanol blends were compared with premium diesel fuels in terms of their emissions. Experimental results showed that formaldehyde and acetaldehyde were the primary and secondary carbonyls in the exhaust, which accounted for 76.0-57.2 vol.% of total carbonyl compounds concentrations for all test fuels (including diesel). Lapuerta et al [151] studied the auto-ignition of blends (bio-butanol and ethanol) with diesel or bio-diesel fuels in a constant-volume combustion chamber. The results showed that as the increase of initial pressure and initial temperature, the 10% v/v alcohol blend in diesel or bio-diesel had a lower delay time, while the retardation effect of biodiesel was slightly higher than that of diesel. Sukjit et al [152] studied the effects of hydrogen on butanol/bio-diesel blends in CI engines. It was found that the hydrogen addition as a combustion enhancer could be used to counteract the increase in THC emissions, and further decreased CO and PM emissions. The emission benefits with hydrogen addition were shown to be further improved for RME/butanol fuel blends. Yilmaz et al [153] studied the effects of bio-diesel/butanol fuel blends on emissions and performance characteristics in a 68

Journal Pre-proof diesel engine. The bio-diesel/butanol blends were 5%, 10%, and 20% butanol in volume basis (B95Bu5, B90Bu10, B80Bu20). Compared to bio-diesel fuel, butanol blended fuels showed lower exhaust gas temperatures and NOx emissions while exhibiting higher CO and unburned HC emissions. Compared with diesel fuel, butanol blended fuels produced lower CO and higher NOx emissions for low concentrations of butanol (5% and 10%), but there was no significant change in terms of HC emissions. Control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since stringent criteria for exhaust emission levels must be met as dictated by the legislated transient cycles, Rakopoulos et al [154] investigated the emissions during acceleration in a turbocharged diesel engine operating with bio-diesel or bio-butanol diesel fuel blends. It was found that compared with the baseline operation of the engine, the two bio-fuel/diesel fuel blends, both leading to serious smoke reductions, but also NO increased. The auto-ignition reactivity of blends of diesel and bio-diesel fuels with butanol isomers have been studied by Hernandez et al [155], the effects of bio-butanol replacement by iso, sec or tert-butanol on the auto-ignition reactivity of diesel and bio-diesel/butanol blends (the total alcohol content being 40% by vol.) were analyzed. The study was performed in a constant volume combustion chamber under different initial temperatures (535 °C, ∼ 600 °C and 650 °C) and bio-butanol substitutions. The partial substitution of bio-butanol by tert-butanol could be an attractive method for increasing the alcohol content while keeping safe engine operation. Partial 69

Journal Pre-proof substitutions with iso or sec-butanol could promote partially premixed combustion conditions with limited pressure gradient peaks. Chemical kinetic simulations confirmed that the difference in the rate of active radical consumption in the butanol isomer was responsible for this trend. Compared with diesel fuel, due to its higher number of secondary C-H bonds, bio-diesel blends were less sensitive to the isomer replacing bio-butanol. 4.4 Engine using bio-butanol/acetone blends as fuel Because BA releases fewer emissions than other fuels, its mixture is considered a green energy resource. BA can produce via fermentation from biomass (agricultural waste and residues) that is non-edible. Butanol has excellent fuel properties such as fast burning speed and high calorific value. As a conventional diesel additive, its superiority has been supported by many studies. But butanol has high production cost, high recovery rate and high production cost, which is the main problem of the use of butanol as a fuel. Because it is not necessary to separate the butanol from other chemicals in the biofuel, so it is cheaper to produce BA than butanol [156]. Table 9 the properties of acetone and bio-butanol [156] Fuel property

Acetone

Bio-butanol

Molecular formula

CH3COCH3

C4H 9OH

Molecular weight (kg/kmol)

58.08

74.11

Stoichiometric fuel/air ratio

0.10526

0.08929

Cetane number

110

25

Flash point (℃)

-20

35

Ignition temperature (℃)

465

343

Viscosity at 298.15 K (mPa s)

0.32

2.95

Density (g/cm3)

0.788

0.81

Lower heating value (MJ/kg)

29.6

33.1

70

Journal Pre-proof Heat of vaporization (MJ/kg)

0.518

0.582

Table 9 shows the physical and chemical properties of acetone and bio-butanol [156]. Algayyim et al [156] studied the impacts of butanol/acetone mixture as a fuel additive on diesel engine performance and emissions. It was found that CO emission levels had a significant decrease for all BA blend with a maximum 64% reduction than D100; CO2 emission was correlated with BP; NOx decreased at all BA blend with a maximum 10% reduction than D100 (100% diesel). ABE is an intermediate product in the ABE fermentation process for producing bio-butanol. As a diesel additive, it had been shown to improve spray evaporation, improve fuel atomization, enhance air/fuel mixing, and improve overall combustion. The combustion characteristics of ABE blended with diesel has been studied by Lee et al [157] in a CI engine. The results showed that by properly tuning the injection quantity and injection timings in the engine, ABE/diesel mixtures had the potential for improving efficiency, and reducing emissions at the same time without sacrificing engine performance. In order to further evaluate the feasibility of increasing the particulate filter regeneration rate, the effects of addition of ABE (up to 30% by volume) to diesel on the soot oxidation reactivity were investigated [158]. The average activation energy calculated using the thermogravimetric curve was compared for the oxidation activity of soot samples. It was found that the average activation energies of the ABE/diesel blends-derived soot were lower than that of diesel-derived soot. Algayyim et al [159] investigated the effect of a butanol-acetone mixture as an additive blended with bio-diesel to improve the latter’s properties. 71

Journal Pre-proof Macroscopic spray characteristics (spray penetration, spray cone angle and spray volume) were measured in constant volume vessel (CVV) at two injection pressures. A high-speed camera was used to record spray images. The results showed that BA could enhance the spray characteristics of bio-diesel by increasing both the spray penetration length and the contact surface area, thereby improving air-fuel mixing. Comparing the effect on emissions of adding BA to biodiesel, increasing the amount of BA reduced NOx and CO (7%) and (40%) respectively compared to neat biodiesel, but increased UHC. 4.5 Engine using bio-butanol/water blends as fuel Experiments were conducted on a turbocharged 3 cylinder automotive common rail diesel engine with port injection of butanol [160]. This dual fuel engine was run with neat butanol and blends of water and butanol (up to 20% water by mass). Compared to butanol without water, water butanol blends improved the BTE by a small extent because of better combustion phasing. As increase in the amount of butanol, the NO emission decreased because of reduced charge temperature. However, due to its small quantity, the water in the blend had little impact. Smoke and NO emissions were lower with the water butanol blends. Use of main plus post injection with the blend (W10) was effective in reducing NO (by 10%) and smoke (by 52%) emissions, without any adverse effect on BTE. 4.6 Engine using bio-butanol/Jatropha oil blends as fuel Due to their carbon neutrality and broad availability, vegetable oils such as jatropha appear to be a promising alternative to mineral diesel. Dilute Jatropha oil 72

Journal Pre-proof with bio-butanol can improve its blended fuel performance. Butanol has the advantages of low viscosity, good oxidizability, and complete miscibility with jatropha oil. Three different blends were prepared [161] having 5%, 10%, 20% bio-butanol mixed with 95%, 90% and 80% Jatropha oil respectively. The results showed that the content of bio-butanol in Jatropha oil increased the calorific value, kinematic viscosity, density and specific gravity of Jatropha oil. BTE was found to increase and brake specific energy consumption was reduced with JO-bio-butanol blends. During the engine test, a significant reduction in emissions of CO, CO2, smoke and NOx was observed [161]. 4.7 Engine using bio-butanol/Waste plastic oil blends as fuel Two oxygenated fuels consisting of butanol and DEE, both possess same number of carbon, hydrogen and oxygen atom but difference functional group, were blended with the waste plastic pyrolysis oil to use in a 4-cylinder DI diesel engine without any engine modification. The results found that compared with the butanol addition at low engine operating condition, the DEE addition to waste plastic oil increased more HC and smoke emissions. However, compared with butanol blend, the benefit to reduce HC and smoke was observed when the DEE blend was tested at high engine operating condition, while CO and NOx were similar [162]. 4.8 Engine using bio-butanol/Fischer-Tropsch fuel blends as fuel LTC was researched by introducing an 80% mass fraction of bio-butanol in reactivity RCCI mode. A 60% mass fraction of bio-butanol was PFI and the additional 20% was direct injected through a blend of bio-butanol with Fischer-Tropsch gas to 73

Journal Pre-proof liquid synthetic paraffinic kerosene or ULSD as reference [147, 163]. The research was conducted with a medium duty experimental diesel engine, it with a proprietary designed high pressure common rail system replacing the OEM injection system. The common rail is configured with a 263 externally driven Bosch CP3 radial pump, piezoelectric fuel injector with a custom nozzle designed for the OEM combustion chamber. The nozzle has an asymmetric spray with a spray angle reducing from 85 to 50 degrees for suitable propagation in the combustion chamber at the designed injection timing. The engine was additionally implemented with a low-pressure EGR circuit, a PFI system, and a centrifugal supercharger driven by an external AC motor with a variable frequency drive as illustrated in Fig. 24 [147, 163]. It was found that RCCI delayed ignition by 7 CAD compared to CDC with a sharper rise in pressure; the butanol blends increased ringing intensity by 85% versus CDC; RCCI with low temperature combustion reduced both NOx and soot by 90%. Compared with the ULSD-butanol blend, the F-T GTL-butanol blend reduced UHC. Fig. 25 shows the aldehyde emissions. In Fig. 25 [163], compared with single fuel injection, ULSD40-Bu60 increased aldehyde emissions by 80-85%, increasing further with the n-butanol blends. It has been found as a consequence of using alcohol for binary mixtures and in-cylinder blending confirmed in [164]. The butanol blends had the highest aldehyde emissions correlating to quenching effects, and trapped mass in the piston fireland and crevice flow seen in also in [165].

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Fig. 24 Experimental engine setup [147, 163]

Fig. 25 the aldehyde emissions [163]

5. Conclusions and recommendations 5.1 Conclusions 75

Journal Pre-proof With the strengthen of people’s environment protection consciousness, the emission regulations of world are becoming stricter and stricter, the current conventional fuel vehicles under tremendous pressure. In order to meet emissions regulations, one of the best solutions is to develop alternative fuel engines for vehicles. Due to the huge technical problems of electric vehicles (such as the charging time of the power battery, the cruising range and the post-processing of the battery etc) and hydrogen fuel cell vehicles (hydrogen storage and safety issues etc), it is difficult for electric vehicles and hydrogen fuel cell vehicles to be widely promoted in a short time. In addition, the use of energy by a single use of electrical energy is not scientific. The energy used in automobiles should consider some key issues such as energy security issues, balance issues, and regional characteristics issues. Therefore, the development of alternative energy sources, even the use of renewable energy, has good prospects in vehicles. With the development of the bio-butanol production technology, it is found that there are certain possibilities for its application in the engines. The future has a certain application prospect. Bio-butanol is a promising alternative fuel, and its production technology, storage technology and transportation technology are becoming more and more mature and perfect. This paper systematically reviews the bio-butanol fuel as an alternative in IC engines, which includes the replacement for SI engines and CI engines. Also, many various application methods such as bio-butanol/gasoline, bio-butanol/diesel blends which can be used on the SI and CI engines are summarized in study. The development and application of bio-butanol fuel to replace the current conventional 76

Journal Pre-proof fuels such as gasoline and diesel fuels can reduce the dependence of petroleum resource. Compared with the conventional fuels (gasoline and diesel fuels), bio-butanol has many various advantages, so it has the potential to improve vehicle emissions, and consequently to improve the atmospheric environment, and improve the pressure on the energy demand, and significantly improve the dependence of non-renewable energy resources. 5.2 Recommendations Despite a lot of effort made by researches from all over the word, bio-butanol applications are still a crucial topic concerning bio-butanol engine development, and it needs further many improvements, some recommendations for future research and development are summarized as follows: (1) More advanced bio-butanol refining technology (fermentation technology), storage technology and transportation technology should be studied, and infrastructure also should be promoted, which are beneficial to the application and promotion of bio-butanol vehicles; (2) From the perspective of engineering applications, bio-butanol fuel is an ideal alternative, renewable, environmentally and economically attractive fuel, the development of high performance (higher thermal efficiencies, lower emissions and fuel consumptions performance) bio-butanol engines to replace the conventional SI engines (gasoline engines) and CI engines (diesel engines) on automobiles have important research significance; (3) The study of combustion and emission mechanisms of bio-butanol fuel (for 77

Journal Pre-proof instance, the detailed chemical reaction kinetics) is the core scientific engineering technology issue to the development of bio-butanol engines; (4) Many new combustion modes such as GCI, HPCC, HCCI, PCCI and RCCI should be more study and improve, which play an important role in the development of bio-butanol engines. Some other new combustion modes should be proposed and development; (5) The small enhanced and advanced supercharging technology should be used in bio-butanol engines, gradually improve the thermal efficiency of bio-butanol engine; (6) The electronic control system need more precise and detailed, intelligent control technique (for instance, multi-variable, multi-condition control technology, etc) can be used in bio-butanol engines; (7)

The

development

of

gasoline/bio-butanol

hybrid

engine

and

diesel/bio-butanol hybrid engine is also a good choice, which has a good automotive market prospect. (8) On dual fuel (gasoline/bio-butanol, diesel/bio-diesel fuels) engines, the development of dual direct injection mode is beneficial to reduce engine fuel consumption and emissions. (9) In the development and research of bio-butanol engines, many more considerations should be given to the national conditions of different countries and cities. So, in order to satisfy the realistic market demand, the authors believe that future researches should focus on above areas, which not only could help explain the 78

Journal Pre-proof combustion and emission mechanisms of bio-butanol fuel, but also have an important contribution to the development, application and promotion of bio-butanol engines. In the future, as countries around the world pay more and more attention to energy conservation and environmental protection, I believe that in the field of IC engines (SI and CI engines), renewable energy such as bio-butanol will be more and more attention and recognition. Acknowledgement This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 51406135, 51776135, 51706155). References [1]. Amiri H, Karimi K. Pretreatment and hydrolysis of lignocellulosic wastes for butanol production: Challenges and perspectives. Bioresource Technol 2018: https://doi.org/10.1016/j.biortech.2018.08.117 [2]. Patakova P, Kolek J, Sedlar K, Koscova P, Branska B, Kupkova K, Paulova L, Provaznik I. Comparative analysis of high butanol tolerance and production in clostridia. Biotechnol Adv 2018; 36 (3): 721-38 [3]. Sun X, Atiyeh HK, Kumar A, Zhang HL, Tanner RS. Biochar enhanced ethanol and butanol production by clostridium carboxidivorans from syngas. Bioresource Technol 2018; 265: 128-38 [4]. Birgen C, Preisig HA. Dynamic modeling of butanol production from Lignocellulosic Sugars. Computer Aided Chemical Engineering 2018; 43: 1547-52 [5]. Farmanbordar S, Karimi K, Amiri H. Muncipal solid waste as a suitable substrate for butanol production as an advanced biofuel. Energy Convers Manage 2018; 157: 396-408 [6]. Xue C, Liu F, Xu M, Tang I, Zhao J, Bai F, Yang S. Butanol production in acetone-butanol-ethanol fermentation with in situ product recovery by adsorption. Bioresource Technol 2016; 219: 158-68

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Journal Pre-proof Highlights  The production methods, marketing and the properties of bio-butanol were summarized.  In SI and CI engines, bio-butanol has a position effect on fuel consumption and emissions.  At present, the bio-butanol mixed combustion method is widely used in SI and CI engines.  This paper put forward some new suggestions in the researches of bio-butanol engine in the future.  To meet environmental and energy balance considerations, bio-butanol has a bright future in SI and CI engines.