Characteristics of microalgae spirulina biodiesel with the impact of n-butanol addition on a CI engine

Energy xxx (xxxx) xxx

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Characteristics of microalgae spirulina biodiesel with the impact of nbutanol addition on a CI engine Upendra Rajak a, Prerana Nashine b, Tikendra Nath Verma a, * a b

Department of Mechanical Engineering, National Institute of Technology Manipur, 795004, India Department of Mechanical Engineering, Manipur Technical University, Manipur, 795001, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 10 December 2018 Received in revised form 23 August 2019 Accepted 8 October 2019 Available online xxx

The aim of the present study is to investigate the effect of ternary blends of n-butanol-spirulina microalgae biodiesel and diesel fuel on compression ignition engine characteristics. Investigation was performed comparing n-butanol blended with microalgae spirulina biodiesel (MSB), low sulphur diesel and pure biodiesel at different engine loads. The MSB (40, 30 and 20%) e n butanol (10, 20 and 30%) blends were 50% with low sulphur diesel fuel in volume basis as B1 (LSD50-MSB40-nB10), B2 (LSD50MSB30-nB20) and B3 (LSD50-MSB20-nB30). The comparison was made with diesel, biodiesel and nbutanol blended fuels which shows a reduction in exhaust gas temperature, Bosch smoke number (BSN), and brake specific particulate matter (BSPM) emission while showing higher specific fuel consumption (SFC), carbon dioxide, and nitrogen oxides emissions. The B20 blend led to a slight reduction in BTE (0.75%), NOX emission (12.58%), BSN (8.95%), and BSPM emission (31.88%) while increasing SFC as compared to diesel fuel. With the addition of the n-butanol in the diesel - microalgae spirulina biodiesel blends, brake thermal efficiency (BTE) has significantly improved during higher heat release rate and cylinder pressure while reduction in smoke and BSPM emissions at all engine loads for B1, B2 and B3 blends. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Compression ignition engine Engine characteristics Ternary blend Spirulina Simulation

1. Introduction The use of alternative fuel in compression ignition (CI) engine is an attractive technique for lesser producing exhaust gas emission. In exact, the diesel-alcohol-alternative blend ratio has the possible to be a substitute at a place of diesel fuel for CI engines. The fuel resources for CI engine using diesel-alcohol-alternative blend ratio in a place of pure petroleum fuel, reduces the dependency of petroleum fuel resources and meet their energy demands in the world [1,2]. In this regards, the different alternative fuel are used in CI engine by the previous researches such as diesel-butanol blends [3], waste plastic oil-n-butanol-diesel blend [4], isobutanol and Calophyllum inophyllum [5], butanol-exhaust gas recirculationdiesel [6], diethyl-ether-biodiesel-diesel [7], DEEekeroseneediesel [8], restaurant yellow grease and n-pentanol-diesel [9], Cymbopogon flexuosus-diesel [10], microalgae oil [11], etc. Rajak et al. [12] showed the uses of diesel and nine different

* Corresponding author. E-mail address: [email protected] (T.N. Verma).

alternative fuel on different engine load, which has been performed at constant speed, and injection timing. Results show that there is lower ignition delay period and soot emission, while specific fuel consumption increases at CR 17.5 and 100% load. Rajak U. and Verma T N [13]. numerically investigated diesel emission characteristics using five different categories of biofuels on single cylinder direct injection engine. Results shows reduction in NOX emission by 94.56% for butanol, PM emission by 93.78% for poultry fats, smoke emission by 93.8% for sunflower and summary of emission by 43.37% for veal oil at full load. Tuccar G. and Aydın K [14]. recent investigation indicate that the use of microalgae oil methyl ester with different blends is a place of petroleum-diesel fuel for diesel engine is better alternative. The results show a small variation in engine power, torque and essential reduction in emissions of CO and NOX emission with different engine speed. Sharon H. et al. [15] evaluated experiments on a diesel engine with fueled palm oilbutanol blends at different engine load (0e100%). During their experiment study, they found to be fuel consumption and thermal efficiency lower than pure diesel fuel while increasing the percentage of butanol in blend increases thermal efficiency. Within the study obtained a reduction in CO, NOX, CO2 and smoke emission but

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higher of HC emission with used of butanol compared to diesel. Labeckas et al. [16] they conducted experimental studies on the ethanol, and rapeseed oil methyl ester has been carried out engine characteristics. The results show that the reduction in NOX and the HC emissions adding of the ethanol to diesel fuel. Atmanlı A. et al. [17] determined that when working on diesel fuel by 60%- cotton oil by 10%-n-butanol by 30%, diesel fuel by 50%- cotton oil by 30%-nbutanol by 20%, diesel fuel by 30%- cotton oil by 30%-n-butanol by 40%, diesel fuel by 30%- cotton oil by 10%-n-butanol by 60%, and diesel fuel by 20%- cotton oil by 20%-n-butanol by 60% as a fuel for diesel engine with various engine speed (1800e4400 rpm) at full load. They found to be a reduction in thermal efficiency, BT, BP and EGT but increase fuel consumption with increasing percentage of nbutanol in the blends. The volume of n-butanol addition with diesel-vegetable oil in the blends obtained lower CO, HC emissions and more NOX emission. The higher percentage of n-butanol shows lower CO and HC emissions and higher fuel consumption. Devarajan Y. et al. [18] investigated the effect of adding noctanol 10, 20 and 30% by volume basis in mustard oil biodiesel on a diesel engine at CR17.0 with higher fuel injection pressure. They concluded that by adding n-octanol to mustard oil biodiesel reduction in HC, and CO emissions. A significant reduction in NOX by 30% emissions and higher fuel consumption. Rajak U. and Verma T N [19]. investigated the effect of microalgae spirulina biodiesel adding in diesel on a water cooled diesel engine. Results show that reduction in SPM, NOX and smoke emission while increases the SFC, HRR and CO2 emission. Emiroglu A O. and S¸en M [20]. studied the effect of ternary blends (biodiesel-diesel-alcohol) on a four stroke, diesel engine. Test results indicated that the improved in ignition delay period for alcohol-biodiesel- diesel blends. The B20 and alcohol blends let to higher HC and NOX but lowered CO and smoke emissions. The butanol had a lower cetane number than diesel and therefore it might protract the ignition delay and increase in emissions. The objective of this study is to evaluate the potential of adding spirulina microalgae biodiesel with diesel and n-butanol to different blends in order to improve the general fuel performance and reduce harmful emission from the compression ignition engine. In the further, third generation non-edible biodiesel based mixtures were prepared with using n-butanol, spirulina microalgae oil and diesel. The influences of spirulina microalgae oil additive on engine performance, combustion, and exhaust emission characteristics of a diesel engine fueled with ternary blends were investigated, and the results were compared to biodiesel with and without diesel fuel. This work was divided into four parts; (1) use of ternary blend of n butanol-biodiesel-diesel and microalgae biodiesel in CI engine compassion of different characteristics of diesel engine by the previous research, (2) determining the method of microalgae biodiesel, n-butanol production and chemical structure of spirulina microalgae, (3) focus on a mathematical tool “Diesel-RK” for validating with experimental data obtained from the test engine and correlation and comparison results, and (4) evaluation of the CI engine characteristics with use of ternary blends B1 (LSD50 þ MSB40 þ n butanol10), B2 (LSD50 þ MSB30 þ nbutanol20), B3 (LSD50 þ MSB20 þ n-butanol30) as compared to diesel fuel.

30e40 min and after shaking the requirements were placed in contact with sunlight. The pH value (7.5) of solutions was maintained constant. Consistent represents that the culture was performed after the time of every 15e18 days. In a presentation of light intensity for growth of microalgae species, the chamber was incubated under illumination (2000e3000 lx) at 25e28 ± 1  C, with dark cycles of 12:12 h for 15-12 days continuously with bubbling of air at present of current pressure required to maintain stirring of the cultures. Without BG 11 common concerns of large-scale cultivation of algae was also attempted in tap water. The combination of methanol and sodium hydroxide used for extracted microalgae oil. The extracted oil is preheated to 60  C and after that mixed with a blender for an hour. All step are done followed by the lipid separation processing by the transesterification process for the biodiesel production. The lipids solvent treated with methanol and H2SO4 at 60  C for hours (lipid to methanol ratio 1:10, H2SO4 1.5% (v/v) [24,59e61]. During the process reactor was adequately maintained, the reaction was completed and produced product allowed to cool at room temperature. The reactor allows the addition adding of water and transfer to separating funnel and also used of heterogenous catalyst in biodiesel production [14,24,25,27,29,64]. The production of microalgae biodiesel process as shown in Fig. 1.

2.2. n-butanol production using oxo process The oxo synthetic is based method on the hydroformylation of propene. The combination of propene and CO þ H2 and catalyst is used for hydroformylation of propene. The hydroformylation of propene is aldehydes reaction and after that catalytic hydrogenation for a separation of Oxo process has different dissimilarities regarding reaction conditions such as temperature and pressure. Oxo process with high pressure processes used to around 75% nbutanol and around 25% 2-methyl-1-propanol, while the current process used to low pressure and modified Rh- catalysts can achieve n-butanol about 95.0% and 2-methyl-1-propanol about 5.0%

2. Material and producer of experiments 2.1. Biodiesel production for microalgae biodiesel The sample of fuel maintained within the conical flask containing 50e100 ml sterile BG 11 media. The proper shaking conditions in time interval were kept at 120 rpm and 24e26  C for

Fig. 1. Microalgae biodiesel process.

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lnnb ¼

3 X

CNb ¼

3 X

2.3. Determination of fuel properties

i¼1

According to previous literatures, n-butanol fuel were investigated in different biodiesel such as waste plastic oil [4], butanol and Calophyllum inophyllum [5], palm oil and diesel [15,30], vegetable oil [17], safflower biodiesel [31], waste cooking oil [39], etc. using different blends, while there is no literature is available on addition of n-butanol with spirulina microalgae biodiesel and diesel fuel different blends as an alternative fuel. Therefore, there is an interest to apply n-butanol with spirulina microalgae biodiesel and diesel fuel and to clearly identify the different percentage of diesel fuel. The n-Butanol, low sulphur diesel (LSD) and microalgae spirulina biodiesel (MSB) were used in this study. The microalgae spirulina biodiesel chemical structure were shown in Table 1. Higher engine performance with lower value of acid compositions [63]. The spirulina biodiesel extracted involves of palmitic by 41.21% and linolenic by 17.79% compounds and linoleic by 12.64% is higher. The ternary blends were selected as (B1) LSD50-MSB40-nB10 (low sulphur diesel by 50% þ MSB by 40% þ n-butanol by 10%), (B2) LSD50-MSB30-nB20 (low sulphur diesel by 50% þ MSB by 30% þ nbutanol by 20%) and (B3) LSD50-MSB20-nB30 (low sulphur diesel by 50% þ MSB by 20% þ n-butanol by 30%). The present work aims to substitute of low sulphur diesel through 50%, only the volumes of spirulina biodiesel and alcohol (n-butanol) were mixed. All the fuel properties taken from published previous data and fuel properties belongs to American Society for Testing and Materials (ASTM) methods. The fuel properties and its blend are shown in Table 2 and the source of material [3,4,19,24,26,30,36,40,51]. In this study, the estimated values for the three blends based on equations. (1) to (5) [32,35,38,48].

3 P

rb ¼

3 X

Xi ri

(1)

i¼1

Xi lnni

(2)

Xi CNi

(3)

i¼1

Xi ri HVi HVb ¼ i¼1 3 P Xi ri

(4)

i¼1





e ðVBIb 10:975Þ 14:534

hb ¼ e

=

[50]. The all Oxo process step by step is done after that produced nbutanol biodiesel. The main features of the oxo process are presented in Fig. 2.

3

 0:8

(5)

where Xi is mixing ratio, ri, CNi, HVi, and vi are known parameters such as density, cetane number, heat value, viscosity, flash point and rb, vb, CNb, and HVb are calculated parameters and VBIb is Viscosity Blending Index. 2.4. Experimental procedure Tests were performed in a constant engine speed (1500 rpm), single cylinder, four-stroke, direct-injection diesel engine coupled to an eddy current dynamometer at different engine loads fueled with diesel fuel for Diesel-RK model [44e46,63] validation. Engine key specifications for the test and the layout of the key-engine are shown in Table 3 and Fig. 3, respectively. This engine was coupled to an eddy current dynamometer which has a torque range of 0e2.4 k.gm and speed range of 0e1500 rpm to measure engine torque. The single cylinder engine was operated 20e30 min at 1500 rpm for steady state condition fueled with regular diesel. The engine reached steady condition after that start the experiments procedure, and experiments repeated three times to ensure the repeatability of engine results, minimise error, and take the average value. Engine performance characteristics were noted by the support of a computer system of control unit which can take values in 10 min time intervals and emissions were taken by the flue gas analyser and smoke meter. Air cooking Piezoelectric Kistler type pressure sensor was used for calculating the combustion cylinder pressure. A crank angler encoder mounted on the crankshaft was used to angular position. The k-type thermocouple was used to measure engine inlet and outlet water, inlet and outlet water temperature for exhaust gas calorimeter and inlet and outlet exhaust gas temperature and ambient temperature. A flue gas analyser (Testo-350) was used to measure exhaust gases from exhaust gas calorimeter such as nitrous oxides, carbon monoxide, and hydrocarbons, etc. Smoke meter was used for calculating the smoke emission. The uncertainty in experiment setup as shown in Table 4. The total percentage of uncertainty analysis ±2.2%, it’s within the range. Uncertainty analysis was calculated by using the standard deviation equation as given in literature [5,7,9,12,13,49,57,58]. 2.5. Numerical model The software Diesel-RK is based on the first law of thermodynamics and is used for the calculation of combustion, engine performance, combustion and emission analysis parameters are given in governing equations (6)e(24) [55e57,62,65].

Fig. 2. Oxo process.

2.5.1. Governing equations Species conservation equation considering the evaluation (6e9)

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Table 1 Major chemical compounds in microalgae biodiesel and their composition. Components

% (w/w)

Structure

Formula

Molecular weight

Caprylic

3.90

8:0

C8H16O2

144.11503

Molecular structure

Cis-10-Pentadecanoic

3.07

15:1

C15H28O2

240.20893

Eicosapentaenoic

e

20:5

C20H30O2

302.22458

Linoleic

12.64

18:2

C18H32O2

280.24023

O

Linolenic

17.79

18:3

C18H30O2

278.22458

O

Lauric

1.14

12:0

C12H24O2

200.17763

Myristic

2.52

14:0

C14H28O2

228.20893

Palmitic

41.21

16:0

C16H32O2

256.24023

O

Palmitolec

3.39

16:1

C16H30O2

254.22458

O

Oleic

4.11

18:1

C18H34O2

282.25588

O

Stearic

1

18:0

C18H36O2

284.27153

O

O OH O OH O OH

OH

OH

O OH O OH OH

OH

OH

OH

Table 2 Physical properties of test fuels. Fuel properties

LSD

MSB

MSB20

n-Butanol

B1

B2

B3

LHV (MJ/kg) Viscosity at 40  C (mm2/s) Density (kg/m3) CN Flash point ( C)

43.1 3.8 838 54 70

41.36 5.66 860 52 130

42.921 4.11 845.99 53.81 82.0

34 2.2 810 25 36

41.21 4.366 840.87 48.60 90.66

40.573 4.2666 840.57 44.706 78.6

39.937 4.166 840.27 40.806 66.6

dm X $ ¼ mj dt

(6)

mi m

(7)

j

Yi ¼

dðmYi Þ ¼ dt ·

Yi¼

X

$

m j Yi þ S g

(8)

j

· Xm j  j

j

·

m

j

cyl

Yi  Yi



þ

Ui Wmw r

(9)

The air-fuel mixture equivalence ratio, denoted by a1, is the ratio of actual air/fuel ratio to the stoichiometric air/fuel ratio, given in equation (10)

 · .·  ma m f ðA=FÞ a1 ¼ ¼ · . ·  ðA=FÞs ma m f

(10)

s

The frictional mean effective pressure (FMEP) is calculated as in equation (11)and using the friction model of Chen and Flynn. SFC was calculated by the next equation (12) [28,34]. The l is given in equation (13) [4,49]. The rate of change of energy, was calculated by the following equation (14) [2,5,8,9]. In the equation (12) FCR is called Fuel Consumption Rate.

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5

Table 3 Engine key specifications for test engine. Key specification

value

Number of cylinder Stroke & Bore (mm) Power rated (kW) & cooling Compression ratio Speed (rpm) Aspirated engine Fuel injection type Fuel pressure Dynamometer type Inlet valve open and closed Outlet valve open and closed Timing Injection Spray angle Number of nozzle and hole diameter (mm) Piston type

Single 110 & 80 3.7 & water 17.5:1 1500 Naturally Higher pressure common rail 500-800 bar Eddy current and air cooling 4.5 (deg. before TDC) and 35.5 (deg. after BDC) 35.5 (deg. before BDC) and 4.5 (deg. after TDC) 23.5 (deg. before TDC) Direct 120 deg. 3.0 and 0.25 Bowl

Fig. 3. Layout of engine.

FMEP ¼ a þ bРmax þ gVp

Table 4 Details of instrumentation. Instruments

Uncertainty (%)

Temperature sensor Pressure sensor Speed sensor Encoder Load cell Burette for fuel measurement Smoke Exhaust gas analyser CO CO2 HC O2 NOX

±0.15 ±0.5 ±1.0 ±0.2 ±0.2 ±1.0 ±1.0 ±0.3 ±1.0 ±0.1 ±0.3 ±0.5

 SFC ðg = kWhÞ ¼

l¼

 FCR ðg=hÞ BPðkWÞ

Air=Fuel ðAir=FuelÞstoich

dðmuÞ dn dQ ht X · ¼ p þ þ mj hj dt dt dt j

(11)

(12)

(13)

(14)

The calculating of auto ignition delay period as in equation (15), during premixed combustion, mixing-controlled combustion phase and late combustion phase. The Heat release rate calculated by using modified Tolstov’s equation.

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sffiffiffi     T Ea 70 4 exp 1  1:6  10 :n  p 8:312T CN þ 25

The thermal NO is calculated using chain Zeldovich mechanism, which is given the in equation. The volume concentration of NO in combustion products is calculated using equations (16)e(21) [47].

emission by 2.22% between the investigated and simulation results at full load condition. Therefore, the differences between experiment and numerical results lie within the acceptable range. The comparison of simulation and experimental data are shown in Table 5 and Fig. 4 for cylinder pressure, Fig. 5 for cylinder heat release rate, Fig. 6 for thermal efficiency of engine and Fig. 7 for smoke emission with the same input boundary condition (see Fig. 8).

O2 42O

(16)

3. Results and discussion

N2 þ O4NO þ O

(17)

3.1. Performance analysis

N þ O2 4NO þ O

(18)

3.1.1. Brake thermal efficiency (BTE) The depiction of BTE for the diesel, microalgae, n-butanol and its blends with respect to loads is shown in Fig. 9. The BTE is defined as the ratio of brake power developed to the heat energy supplied by the fuel. The fuel conservation efficiency is described as the thermal efficiency of the diesel engine. It is clear from the figure, BTE increased with the higher percentage of n butanol due to the presence of an oxygen molecule in butanol [4,5]. At 100% load, the BTE (%) was found to be 33.18 for diesel, 30.71 for MSB, 32.8 for n-butanol, 32.93 for B20 (LSD80 þ MSB20), 30.07 for B1 (LSD50 þ MSB40 þ n-butanol10), 30.87 for B2 (LSD50 þ MSB30 þ n-butanol20), and 34.57 for B3 (LSD50 þ MSB20 þ n-butanol30). The BTE gradually increase with higher percentage of n-butanol due to decrease density of blends with increasing percentage of n-butanol within the blend which may improve spray atomization [4]. The BTE for the blend of B3 (LSD50 þ MSB20 þ n-butanol30) and pure n-butanol was found to be 4.02% and 11.2% higher compared to low sulphur diesel fuel due to a higher percentage of oxygen contents within the fuel and results in higher efficiency. The addition of low cetane number nbutanol rises the ignition-delay period of the blends during combustion due to the effect of OH group as most of the n-butanol undergoes H-abstraction by OH radicals from the a-carbon position. This increased ignition delay period helps fuel-air mixing which increased the efficiency. The increase in engine load, the increased BTE due to better mixing rate of fuel and higher cylinder temperature and decreased ignition delay period [4,34].

t ¼ 3:8  10

6

(15)

d½NO ¼ dq

Р  2:333  107 :e

( 2 )  ½N2 e :½Oe : 1  ½NO=½NO e 1 : 0 1

38020 T b

2365 B Tb ½NO C :½NO A R:Tb :@1 þ 2365 Tb :e

u

e

(19) The NO concentration in a cylinder is given by:

rNOc ¼ rNO rbc

(20)

and the specific NO in g/kWh is expressed as

eNO ¼

30  rNO  Mbg LC  hM

(21)

The level of soot formation can be calculated using the Hatridge smoke level, which is expressed as given in equation (22). The soot formation in the burning zone is calculated by the equation (23). The specific particulate matter emission was calculated by the following equation (24) [12].

Hartridge ¼ 100f1  0:9545 expð2:4226½CÞg 

d½C dt

 ¼ 0:004 K

qc dx V dt

 SPM ¼ C  565 ln

10 10  BN

(22) (23)

1:206 (24)

2.6. Validation tool Thermodynamic models dependent on the first law of thermodynamics and are used to examine the combustion performance of engines in Diesel-RK software. Pressure, temperature and other essential properties are assessed with respect to crank angle or with respect to interval. The engine friction and heat release are taken into account using semi-empirical correlations derived from experimental results. The ignition process inside the engine cylinder is simulated using multi-zone model. The governing equations are taken into attention in this model as defined by Fiveland and Assanis [44e46,56,57]. Validation of simulation tool diesel-RK model with the experimental data obtained from the engine and comparison with simulation data were carried out on a diesel engine. The maximum deviation in BTE by 2.13%, CP by 2.99% HRR by 4.89% and smoke

3.1.2. Brake specific fuel consumption (SFC) The variation of SFC for the engine with different loads is shown in Fig. 10. The suction pressure developed with higher engine load than decreased SFC. The SFC was found to be lower for 50% diesel20% MSB- 30% butanol combination of the blend than the pure biodiesel and n-butanol because of having higher energy. When the percentage of n-butanol increased in the blend, SFC decreased which might be due to the increased oxygen and more oxygen content leads to the better combustion process. At full load, the SFC (g/kWh) was found to be 251.72 for diesel, 283.52 for MSB, 283.07 for n-butanol, 254.67 for B20 (LSD80 þ MSB20), 291.12 for B1 (LSD50 þ MSB40 þ n-butanol10), 287.43 for B2 (LSD50 þ MSB30 þ n-butanol20), and 260.69 for B3 (LSD50 þ MSB20 þ n-butanol30). The SFC for the MSB by 11.21%, n-

Table 5 Comparison of experimental and simulation results at 100% load. Parameters

Experimental

Simulation

Deviation (%)

CPP (MPa) BTE (%) HRR (J/deg.) Smoke Opacity (BSN) NOX emission (ppm)

8.75 32.1 65.4 0.88 3409.7

9.02 32.8 62.2 0.90 3585.0

2.99 2.13 4.89 2.2 4.88

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Injection pressure = 220 bar Speed = 1500 rpm CR = 17.5

8

40

Experimental Numerical

Injection pressure = 220 bar Speed = 1500 rpm CR = 17.5 Brake thermal efficiency (%)

In-cylinder pressure (MPa)

10

6

4

2

7

0

30

20

10

340

350

360

370

380

390

400

25

50

Crank angle (deg.)

100

Fig. 6. BTE with load.

80

1.0

Experimental Numerical

Injection pressure = 220 bar Speed = 1500 rpm CR = 17.5

Injection pressure = 220 bar Speed = 1500 rpm CR = 17.5 Smoke emission (BSN)

60

75

Load (%)

Fig. 4. Cylinder pressure.

Cylinder heat release rate (J/deg.)

Experimental Numerical

40

20

Experimental Numerical

0.5

0 0.0

330

340

350

360

370

380

390

400

Crank angle (deg.)

25

50

75

100

Load (%) Fig. 7. BSN with load.

Fig. 5. Cylinder heat release rate.

butanol by 11.07%, B20 by 1.15%, B1 by 13.53%, B2 by 12.42%, and B3 by 3.44% was found to be higher compared to low sulphur diesel fuel. This happens due to lower energy content within the biodiesel, n-butanol and its blends compared to diesel fuel. This is one negative aspect of the diesel-biodiesel-n-butanol blend. It was observed that there is a decrease in SFC with an increases in engine load but slowly reduced from 50% to 100% loads. This slight drop could be caused due to the low excess air-fuel ratio at high engine loads that decreased combustion output, which requires more amounts of fuel to be combusted inside the cylinder to produce the same amount of work output. They have concluded that according to the contrast in lower calorific value of alternative fuel and their blends as compared to diesel fuel, the fuel burning increased than the diesel fuel [7e9].

3.1.3. Exhaust gas temperature (EGT) The variation of EGT for the engine at 25, 50, 75 & 100% engine load conditions is shown in Fig. 11. The increased engine load than higher EGT because of more fuel injected in the cylinder chamber, more equivalence ratio leads to more temperature [15,41]. At full load, the EGT (K) was found to be 682.6 for diesel, 653.31 for MSB, 659.89 for n-butanol, 660.5 for B20 (LSD80 þ MSB20), 642.2 for B1 (LSD50 þ MSB40 þ n-butanol10), 641.67 for B2 (LSD50 þ MSB30 þ n-butanol20), and 659.76 for B3 (LSD50 þ MSB20 þ n-butanol30). The EGT for the MSB by 4.29%, nbutanol by 3.3%, B20 by 3.32%, B1 by 5.92%, B2 by 5.99%, and B3 by 3.3% was found to be lower compared to low sulphur diesel fuel. This happens due to lower energy content, the high latent heat of evaporation within the biodiesel, n-butanol and its blends compared to diesel fuel. The similar result obtained by previous studied working with butanol [17,31,32]. The presence of more

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4000

Experimental Numerical

Average exhaust gas temperature (K)

Speed=1500 rpm CR=17.5

NOX emission (ppm)

3000

2000

1000

0

25

50

75

100

50

n-Butanol

B20

B1

Brake thermal efficiency (%)

40

30

20

10

0 25

50

75

100

Engine load (%) Fig. 9. BTE with engine load.

800

Specific fuel consumption (g/kWh)

D100 B2

MSB B3

n-Butanol

B20

B1

600

400

200

0 25

50

n-Butanol

B20

B1

800

600

400

200

0 25

50

75

100

Fig. 11. EGT with engine load.

Fig. 8. NOX emission with load.

MSB B3

MSB B3

Engine load (%)

Load (%)

D100 B2

D100 B2

75

Engine load (%) Fig. 10. SFC with engine load.

100

amount of oxygen in the chemical structure of n-butanol may create an important cooling effect of the fuel spray patterns leading to longer ignition delay, causing incomplete combustion and lower exhaust gas temperatures [17]. 3.1.4. Volumetric efficiency The variation of volumetric efficiency for the engine with 25, 50, 75 and 100% engine loads is shown in Fig. 12. The volumetric efficiency depends on a different factor of an engine such as throttle valve, engine speed, and exhaust gas layout [38]. The increased engine load than lower volumetric efficiency due to increased exhaust gas temperature because of more fuel burned within the engine cylinder [19]. At full load, the volumetric efficiency (%) was found to be 90.42 for diesel, 91.73 for MSB, 91.91 for n-butanol, 91.81 for B20 (LSD80 þ MSB20), 91.42 for B1 (LSD50 þ MSB40 þ n-butanol10), 91.49 for B2 (LSD50 þ MSB30 þ n-butanol20), and 91.62 for B3 (LSD50 þ MSB20 þ n-butanol30). The volumetric efficiency (%) for the MSB by 1.42, n-butanol by 1.62, B20 by 1.51, B1 by 1.1, B2 by 1.16, and B3 by 1.3 was found to be higher compared to low sulphur diesel fuel. This happens due to lower energy content, more fuel injected in the cylinder, biodiesel, n-butanol and its blends compared to diesel fuel. The increasing fraction of biodiesel within the blend increases the density and volumetric efficiency due to the increase in engine power with higher engine loads. Volumetric efficiency was found to be higher for alternative fuel and its blends due to its better combustibility. The percentage of air taken inside the combustion cylinder is dependent on the volumetric efficiency of an engine and hence puts a limit on the amount of fuel which can be efficiently burned and correspondingly the power output. Also, the volumetric efficiency depends upon fuel type, throttle opening and engine speed as well as induction and exhaust system layout, port size and valve timing and opening duration [19,38]. 3.1.5. Air fuel equivalence ratio (Lambda) The variation of air fuel equivalence ratio (Lambda) for the engine at 25, 50, 75 and 100% loads is shown in Fig. 13. The microalgae spirulina biodiesel and n-butanol used higher volume, the mixture is leaner. The engine runs higher leaner with microalgae spirulina biodiesel -n butanol-diesel ternary blends compared to low sulphur diesel as verified from the figure. At full load, the lambda was found to be 1.264 for diesel, 1.438 for MSB, 1.643 for n-butanol, 1.371 for B20 (LSD80 þ biodiesel20),

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D100 B2

MSB B3

n-Butanol

B20

B1

Volumetric efficiency (%)

100

80

60

40

20 25

50

75

100

Engine load (%) Fig. 12. Volumetric efficiency with engine load.

Air fuel equivalence ratio in the cylinder

10

D100 B2

MSB B3

n-Butanol

B20

B1

8

6

4

2

0 25

50

75

100

Engine load (%) Fig. 13. Lambda with engine load.

1.349 for B1 (LSD50 þ MSB40 þ n-butanol10), 1.388 for B2 (LSD50 þ MSB30 þ n-butanol20), and 1.433 for B3 (LSD50 þ MSB20 þ n-butanol30). The lambda for the MSB by 12.1%, n-butanol by 23.06% B20 by 7.8%, B1 by 6.3%, B2 by 8.9%, and B3 by 11.79% was found to be higher compared to low sulphur diesel fuel. Where Air/Fuel is the actual overall air-fuel ratio and (Air/Fuel)stoich is the stoichiometric air-fuel ratio. Higher the values of l, leaner the mixture is and also lower heat value of blends affected. It can be inferred that, higher the concentration of n-butanol in the biodiesel/diesel blends, the leaner the mixture is. The engine runs overall leaner when fueled with diesel/biodiesel/n-butanol ternary blends compared to biodiesel as shown in Fig. 13. This is in accordance with the decrease in fuel consumption with increasing percentage of n-butanol in the blends [4,49]. 3.2. Combustion analysis 3.2.1. Cylinder pressure The variation of fuel cylinder pressure versus crank angle for the engine at 25, 50, 75 and 100% loads as shown in Fig. 14. The comparison of cylinder pressure with the cylinder pressure-crank angle diagram shows similarity in combustion process for diesel, MSB, n

9

butanol and its blends of B1, B2 and B3. The cylinder pressure-crank angle of MSB, n butanol and its Blend of B1, B2 and B3 are a similar trend to that of petroleum diesel for the entire range of crank angle except between 330 and 400 of crank angle. Maximum cylinder pressure increases with increasing engine load for petroleum diesel, MSB, n butanol and its Blend of B1, B2 and B3. The maximum cylinder pressure value of MSB by 6.0% B1 by 15.9%, and B2 by 15.43% is higher as compared to low sulphur diesel because of temperature, vaporisation rate, heat release rate, ignition delay is higher [7,43]. The maximum cylinder pressure produced for petroleum diesel is 11.646 MPa at 367.0 , 12.398 MPa for MSB at 366.0 , 8.15 MPa for n butanol at 375.0 , 8.32 MPa for B20 at 364.0 , 13.856 MPa for B1 at 363.0 , 13.771 MPa for B2 at 163.0 and 11.61 MPa for B3 at 365.0 of crank angle. Cylinder pressure increases with increasing percentage of n-butanol due to higher fuel consumption, ignition delay period, combustion duration and lower diffusion combustion for B1, B2 and B3 and that is the ron behind for the higher cylinder peak pressure for blends. The cylinder pressure gradually increases as the combustion progresses. The maximum cylinder pressure of n-butanol slightly lower than low sulphur diesel due to less calorific value than low sulphur diesel. The addition of biodiesel and n-butanol has an intermediate result on the blends. The addition of biodiesel increases the oxygen content in the combination that leads to better combustion efficiency and thus higher in-cylinder pressure; this is accounted for by the higher calorific value of diesel. The lower engine load indication of lower cylinder peak pressure is owing to the higher ignition delay [1]. 3.2.2. Cylinder heat release rate The peak heat release rate (J/deg.) for the spirulina biodiesel -n butanol - diesel, and its blends (B1, B2 and B3) fuels at 25, 50, 75 and 100% loads is given in Fig. 15. It is clear from the figure that the spirulina, n butanol, B1, B2, and B3 produces more HRR compared to petroleum diesel due to late combustion of spirulina biodiesel, n butanol, B1, B2 and B3 with higher ignition delay comparison with diesel fuel which occurred rapid combustion with time. When the volume of n butanol is increased within the blends than more HRR occurred due to better-premixed combustion and reduced cetane number and higher oxygen contents [5,15]. The cylinder heat release rate-crank angle of MSB, n butanol and its Blend of B1, B2 and B3 are a similar trend to that of petroleum diesel. The peak HRR point occurrence is almost similar for all tested fuel and blend. The cylinder peak heat release rate (J/deg.) produced for petroleum diesel (D100), MSB (microalgae spirulina biodiesel), n-butanol, B20, B1, B2 and B3 are 87.9, 94.5, 90.8, 91.1, 118.0, 117.1 and 101.1 respectively at 100% engine load. It can also be concluded that the alternative fuel starts prior combustion than low sulphur diesel, owing to fuel properties. Addition of n-butanol to spirulina microalgae biodiesel and low sulphur diesel results in relatively higher heat release rate as compared to diesel and this can be accounted for its higher contents of oxygen and a lower CN than low sulphur diesel that leads to a longer ignition delay and hence delayed combustion start. Due to increased and improved premixed combustion [5,15]. 3.2.3. Ignition delay period (IDP) Ignition delay period (degree) for the diesel, spirulina biodiesel, n butanol and its blends (B1, B2 and B3) fuels at different engine loads as shown in Fig. 16. The ignition delay period is defined as the time period between when 5% of the total heat is released and the start of injection [40]. IDP is an essential factor of the combustion engine and depends on the CN of the fuel. The ignition delay is calculated as the difference between the SOI and the SOC. In general, increases the engine load with reduction of the ignition delay

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10

U. Rajak et al. / Energy xxx (xxxx) xxx D100 B2

MSB B3

n-Butanol

B20

12

B1

(a) Load =25%

8

In-cylinder pressure (MPa)

In-cylinder pressure (MPa)

10

6

4

2

10

D100 B2

MSB B3

B20

B1

(b) Load =50%

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6

4

2

0 330

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400

0 330

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D100 B2

MSB B3

n-Butanol

B20

16

B1

14

(c) Load =75%

In-cylinder pressure (MPa)

14

360

370

380

390

400

Crank angle (deg.)

Crank angle (deg.) 16

In-cylinder pressure (MPa)

n-Butanol

12 10 8 6 4 2

D100 B2

MSB B3

n-Butanol

B20

B1

(d) Load =100%

12 10 8 6 4 2

0 330

340

350

360

370

380

390

Crank angle (deg.)

400

0 330

340

350

360

370

380

390

400

Crank angle (deg.)

Fig. 14. Cylinder pressure at a) 25%, b) 50%, c) 75% & d) 100% engine load.

period of engine load due to several factors such as the mixing of air-fuel, load, oxygen, etc. [2,5]. The combustion ignition delay of microalgae spirulina biodiesel, n butanol and its Blend of B1, B2 and B3 are a similar trend to that of petroleum diesel. At 100% load, ID (degree) produced for petroleum diesel is 11.7, 10.8 for MSB, 16.53 for n butanol, and 9.93 for B20, 11.79 for B, 13.23 for B2 and 14.89 for B3. The ignition delay period was found to be higher for n butanol and blends (B1, B2 & B3) due to lower cetane number compared to diesel fuel and spirulina biodiesel. A similar work by Ashok B. et al. [5] on a ternary blend of the higher isobutanol with diesel and calophyllum inophyllum biodiesel presented a higher ID for the increasing percentage of the alcohol which is due to lower of CN. In the present numerical study, the increase in ID with increasing percentage of n-butanol in mixtures was obtained. It may be due to advanced fuel injection timing because of lower viscosity, density, CN and more latent heat of n-butanol [8,15]. 3.2.4. Combustion duration (CD) Combustion duration (degree) for the diesel, spirulina biodiesel, n butanol and its blends (B1, B2 and B3) at 25, 50, 75 and 100% loads as shown in Fig. 17. The combustion duration (CD) is defined as the time period between hen 5% of the total heat is released and 95% of the total heat is released [40]. CD is an essential factor of the combustion engine and depends on the CN of the fuel and combustion temperature in premixed phase. In the present study, the combustion duration is calculated as the period between when 5% of the total heat is released (CA5) and when 95% of the total heat is released (CA95). In general, the combustion duration increase with increasing engine load due to more fuel quantity injected into the cylinder. The combustion duration depends on the several factors such as cetane number, latent heat of evaporation, droplet size, oxygen, and flame propagation [1,6,37,40]. The ignition delay

increases lead to higher combustion duration [10]. Addition of nbutanol with spirulina biodiesel with low sulphur diesel fuel increases CD, owing to fuel injection and air/fuel mixture formation [1]. At 100% load, CD (degree) produced for petroleum diesel is 83.1, 85.92 for MSB, 87.54 for n butanol, and 89.59 for B20, 55.43 for B1, 87.83 for B2 and 89.6 for B3. The CD was found to be higher for spirulina biodiesel, n butanol and its blends (B1, B2 & B3) compared to diesel fuel due to CN and oxygen percentage. The CD increase with increasing engine loads due to decreasing ignition delay period cause of increasing combustion temperature with higher engine loads [1]. 3.3. Emission analysis 3.3.1. Smoke analysis Bosch Smoke Number (BSN) for the diesel, spirulina biodiesel, n butanol and its blends (B1, B2 and B3) fuels at various loads as given in Fig. 18. In CI engine, the smoke emission is produced in two different way: formation and oxidation of soot. The soot formation rate depends on the collisions of molecular rate, and soot oxidation is based on collisions of the gas phase. The smoke emission formation produced due to soot oxidation mechanism [21,51,52]. The BSN happens primarily in the fuel-rich zone of the combustion chamber, at high combustion chamber pressure-temperature. If the delivered fuel is moderately oxygenated, locally over-rich rons can be reduced, and the first formation of smoke emission can be controlled [25]. The principle of light absorption is described of BSN which is measure the amount of light absorbed when the light passes through the exhaust gas. The BSN increases with increasing engine load, which is clear from the figure. At full load, BSN produced for petroleum diesel is 3.35, 2.49 for MSB, 2.62 for n butanol, and 3.09 for B20, 3.01 for B1, 2.65 for B2

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80

D100 B2

MSB

n-Butanol

B20

B1

B3

Cylinder heat release rate (J/deg.)

Cylinder heat release rate (J/deg.)

40

11

(a) 25% load 30

20

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0 330

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D100 B2

MSB

n-Butanol

B20

B1

B3

(b) 50% load

60

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20

0 330

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390

400

B20

B1

Crank angle (deg.)

Crank angle (deg.)

Cylinder heat release rate (J/deg.)

120

B0 B2 100

MSB B3

n-butanol

B20

B1

(c) 75% load

80

60

40

20

0 330

340

350

360

370

380

390

400

Crank angle (deg.) Fig. 15. Cylinder peak heat release rate for a) 25%, b) 50%, c) 75%, d) 100% loads.

30

25

100

D100 B2

MSB B3

n-Butanol

B20

B1

D100 B2

MSB B3

n-Butanol

Combustion duration (deg.)

Ignition delay period (deg.)

80

20

15

10

5

0 25

50

75

Engine load (%) Fig. 16. Ignition delay with engine load.

100

60

40

20

0 25

50

75

100

Engine load (%) Fig. 17. Cylinder combustion duration engine load.

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U. Rajak et al. / Energy xxx (xxxx) xxx

5

Bosch smoke number (BSN)

D100 B2

MSB B3

n-Butanol

50

75

B20

B1

4

3

2

1

0 25

100

Engine load (%) Fig. 18. BSN versus load.

and 2.51 for B3. The BSN was found to be lower for spirulina biodiesel, n butanol and its blends (B1, B2 & B3) compared to diesel fuel due to higher oxygen percentage and lower C/H of biodiesel and n butanol and its blends. The addition of spirulina biodiesel, and n-butanol to low sulphur diesel fuel sustained to reduce BSN at higher loads, yet not much at lower loads. Oxygen content, oxygenated nature, and lower carbon content of n-butanol could also be evidenced from the lean burning nature of the ternary blends. A similar work of smoke emission alcohol addiction with diesel fuel to other studies [4,5,21,23]. 3.3.2. Brake specific carbon dioxide emission Brake specific carbon dioxide (BSCO2) emission for the diesel, spirulina biodiesel, n butanol and its blends (B1, B2 and B3) fuels at various loads as given in Fig. 19. The BSCO2 emission as a product of exhaust gas emission from compression ignition engine and no effect on global warming due to absorbing by plants during photosynthesis which causes net zero carbon emission [15]. Higher carbon dioxide emission shows the complete combustion of the fuel. The amount of carbon dioxide increase with higher combustion temperatures and sufficient oxygen for an exact burn [42,52].

The specific carbon dioxide emission decreases with increasing engine load, which is clear from figure but higher for biodiesel. The carbon dioxide emission of MSB, n butanol and its Blend of B1, B2 and B3 is the similar trend to that of petroleum diesel. The BSCO2 (g/kWh) emission levels was found to be 794.33 for diesel, 823.67 for spirulina biodiesel, 680.01 for n butanol, 801.23 for B20 (80% LSD þ 20% biodiesel), 870.84 for B1 (50% LSD þ 40% MSB þ 10% nbutanol), 843.38 for B2 (50% LSD þ 30% MSB þ 20% n-butanol), and 750.0 for B3 (50% LSD þ 20% MSB þ 30% n-butanol) at 100% load. The BSCO2 emission was found to be higher for spirulina biodiesel, B20, B1 and but lower for n butanol and B3 comparison with low sulphur diesel fuel due to oxygen percentage, fuel consumption and C/H of biodiesel and n butanol and its blends. This is owing to effects of increase cylinder temperature and better combustion with increasing engine loads and lower C/H ratio and higher percentage of oxygen cause of reduction BSCO2 emission. High BSCO2 emissions at low engine due to low combustion temperature (cooling effect due to higher latent heat of evaporation) and prolonged oxidation process [22,28,29]. A similar work of BSCO2 emission alcohol addiction with diesel fuel owing to complete combustion of fuel to other studies [22,66,67].

3.3.3. NOX emission NOX emission values for all test fuels at 25%, 50%, 75% and 100% engine loads are specified in Fig. 20. NOX emission for the test blends was increased in comparison with diesel fuel with the addition of n butanol and lower with biodiesel and its blend. NOX emissions obtained from diesel, MSB, D80-B20, D50-MSB40-n buatnol10, D50-MSB30-n buatnol20 and D50-MSB20-n buatnol30 were observed the almost same trend for tested fuel. NOX emission was found to be higher for the ternary blends but lower for nbutanol, spirulina biodiesel and blend (B20) comparison with low sulphur diesel fuel due to higher flame temperature during combustion process of diesel-spirulina-n butanol blends. In addition to butanol with diesel-biodiesel, the higher oxygen content also lead to higher combustion cylinder temperature and also lead to increase NOX emission. The NOX emission (ppm) levels was found to be 3409.7 for diesel, 3309.1 for spirulina biodiesel, 1842.2 for n butanol, 2892.8 for B20 (80% LSD þ 20% biodiesel), 3650.8 for B1 (50% LSD þ 40% MSB þ 10% n-butanol), 3498.2 for B2 (50% LSD þ 30% MSB þ 20% nbutanol), and 3500.8 for B3 (50% LSD þ 20% MSB þ 30% n-butanol) at 100% load condition. The NOX emission was found to be higher

D100 B2

MSB B3

n-Butanol

B20

5000

B1

D100 B2

2000

MSB B3

n-Butanol

B20

B1

4000

NOX emission (ppm)

Brake specific carbon dioxide (g/kWh)

2500

1500

1000

500

3000

2000

1000

0

0

25

50

75

Engine load (%) Fig. 19. Brake specific carbon dioxide versus engine load.

100

25

50

75

100

Engine load (%) Fig. 20. NOX emission engine load.

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for 50% LSD þ40% MSB þ10% n-butanol, 50% LSD þ30% MSB þ20% n-butanol, and 50% LSD þ20% MSB þ30% n-butanol and but lower for spirulina biodiesel, blend (B20) and n butanol comparison with low sulphur diesel fuel due to oxygen percentage, combustion temperature, high latent heat of vaporisation, iodine value, degree of unsaturation, double bonds in the chemical structure, ignition delay, reaction time, premixed portion of combustion [14,33,49,54]. It can be seen from the figure of NOX emissions with engine loads, NOX emission increases with increase in engine load. Higher engine load means higher combustion temperatures, which is effected by amount of injected fuel in cylinders. Combustion temperature and contents of oxygen plays a dynamic role in formation of NOX. Higher combustion temperatures and residence time of the gases at that temperatures result in higher NOX formation rates [66e68].

3.3.4. Brake specific particulate matter (BSPM) emission Brake specific particulate matter (BSPM) emission values for the test fuels under the different engine load of 25, 50, 75 and 100% are presented in Fig. 21. In present research, for n-butanol usage BSPM emission were observed lower for spirulina biodiesel, n butanol and its blends as comparison with diesel fuel. BSPM emission results can be affected with the oxygen content of spirulina biodiesel, nbutanol, and its blends. In general, BSPM emission decrease with increase in engine load. For 50% LSD þ20% MSB þ30% n-butanol, higher amount of BSPM emission reduced by 73.9% as comparison with diesel fuel. According to the previous studied, BSPM emissions were lower for n butanol blends as comparison with diesel fuel [3,22,53]. Biodiesel has better combustion characteristics and this composed the occurrence of higher oxygen contents has helped better combustion, and hence, a significant reduction in PM emission is observed [65]. The BSPM emission (g/kWh) levels was found to be 0.828 for diesel, 0.625 for spirulina biodiesel, 0.630 for n butanol, 0.564 for B20 (80% LSD þ 20% biodiesel), 0.258 for B1 (50% LSD þ 40% MSB þ 10% n-butanol), 0.261 for B2 (50% LSD þ 30% MSB þ 20% nbutanol), and 0.216 for B3 (50% LSD þ 20% MSB þ 30% n-butanol) at 100% load condition. The BSPM emission was found to be lower for, 80% LSD þ20% MSB, 50% LSD þ40% MSB þ10% n-butanol, 50% LSD þ30% MSB þ20% n-butanol, and 50% LSD þ20% MSB þ30% nbutanol compared with diesel fuel due to higher percentage of oxygen.

3.3.5. Factor of absolute light absorption Factor of absolute light absorption (FALA) emission values for all test fuels at different engine load of 25, 50, 75 and 100% are illustrated in Fig. 22. FALA emission for the test blends were increased in comparison with diesel and spirulina and n butanol fuel. FALA emissions obtained from diesel, MSB, D80-B20, D50-MSB40-n buatnol10, D50-MSB30-n buatnol20 and D50-MSB20-n buatnol30 were observed the almost same trend for tested fuel. FALA emission was found to be higher for the ternary blends and blend (B20) but lower for n-butanol, spirulina biodiesel comparison with low sulphur diesel fuel. Because of higher calorific value and oxygen of spirulina and n butanol. The FALA emission (1/m) levels was found to be 1.2 for diesel, 0.72 for spirulina biodiesel, 0.77 for n butanol, 1.78 for B20 (80% LSD þ 20% biodiesel), 2.81 for B1 (50% LSD þ 40% MSB þ 10% n-butanol), 2.1 for B2 (50% LSD þ 30% MSB þ 20% nbutanol), and 2.4 for B3 (50% LSD þ 20% MSB þ 30% n-butanol) at 100% load condition. The FALA emission was found to be higher for 50% LSD þ40% MSB þ10% n-butanol, 50% LSD þ30% MSB þ20% nbutanol, and 50% LSD þ20% MSB þ30% n-butanol, B20 (80% LSD þ 20% biodiesel) and but lower for spirulina biodiesel, and n butanol compared to diesel fuel. This may happen due to oxygen percentage.

4. Conclusion The effects of n-butanol is addition to spirulina biodiesel and diesel blends on diesel engine characteristics at different engine loads have been numerically evaluated and experiments conducted for tool validation with diesel fuel. Microalgae spirulina biodiesel (MSB), n-butanol (B100) and low sulphur diesel (LSD100) are blends as B1 (LSD50 þ MSB40 þ B10), B2 (LSD50 þ MSB30 þ B20), and B3 (LSD50 þ MSB20 þ B30) were investigated and comparisons have been made with MSB100 and LSD100. The following conclusions obtained from simulation work.  Increasing volume of n-butanol in spirulina biodiesel and diesel blends than BTE of the engine increases as compared to spirulina biodiesel and n-butanol. B20 (LSD80 þ MSB20), B2 (D50 þ MSB30 þ B20) and B3 (LSD50 þ MSB20 þ B30) blends provides better performance than diesel, MSB and n- butanol. The diesel engine was found to have better efficiency for LSD50MSB20-B30 as compared to diesel.

2.5

MSB B3

n-Butanol

B20

2.0

BSPM emission (g/kWh)

4

B1 Factor of absolute light absorption (1/m)

D100 B2

1.5

1.0

0.5

0.0

13

D100 B2

MSB B3

n-Butanol

B20

B1

3

2

1

0

25

50

75

Engine load (%) Fig. 21. BSPM emission versus engine load.

100

25

50

75

100

Engine load (%) Fig. 22. FALA emission engine load.

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U. Rajak et al. / Energy xxx (xxxx) xxx

 SFC of the ternary blends was more than LSD due to its LHV. However, the B20 and B3 shows lower SFC as compared to MSB, n-butanol. The SFC for the MSB was found to be higher by 11.21%, n-butanol by 11.07%, B20 by 1.15%, B1 by 13.53%, B2 by 12.42%, and B3 by 3.44% as compared to low sulphur diesel fuel.  The ternary blends were found to be higher ignition delay as compared to LSD, microalgae spirulina and its blend because of the presence of n-butanol in the blend.  The ternary blends of B1, B2, B3 and pure microalgae spirulina biodiesel results in higher HRR and CPP as compared to low sulphur diesel fuel due to the presence of more oxygen.  On the contrary, n-butanol ternary blends effectively reduces the BSPM, and smoke emissions when compared to microalgae spirulina, n- butanol and low sulphur diesel fuel and LSD50MSB20-B30 were found better concerning BSPM, and smoke emission reduction.  The addition of n-butanol in low sulphur diesel with microalgae spirulina biodiesel increases the NOX emission for B1, B2 and B3 blends and reduces with microalgae spirulina biodiesel B20 (LSD80 þ MSB20). The overall test result indicates that the trade-off between NOX and BSPM of diesel engine was reduced by using microalgae spirulina biodieselediesel blends and B3 (LSD50 þ MSB20 þ B30) the optimum and most favourable blend ratio was found to be without any modifications in the engine. Nomenclature BP BN C CN CP CR FCR HRR LSD LHV MSB CPP P rpm SFC SOC SOI SPM TDC V B1 B2 B3 B20 CO2 NOX

g l

Brake power Bosch number Constant Cetane number Cylinder pressure Compression ratio Fuel consumption rate Heat release rate Low sulphur diesel Lower heating value Microalgae spirulina biodiesel Cylinder peak pressure Pressure Revolutions per minute Specific fuel consumption Start of combustion Start of injection Specific particulate matter Top dead centre Volume LSD50 þ MSB40 þ B10 DLS50 þ MSB30 þ B20 LSD50 þ MSB20 þ B30 LSD80 þ MSB20 Carbon dioxide Nitrogen oxides Ratio of the specific heat for ideal gas Air-fuel equivalence ratio

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Please cite this article as: Rajak U et al., Characteristics of microalgae spirulina biodiesel with the impact of n-butanol addition on a CI engine, Energy, https://doi.org/10.1016/j.energy.2019.116311