Comparative assessment of engine performance and emissions fueled with three different biodiesel generations

Renewable Energy 147 (2020) 1058e1069

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Renewable Energy journal homepage: www.elsevier.com/locate/renene

Comparative assessment of engine performance and emissions fueled with three different biodiesel generations Sara Tayari a, *, Reza Abedi b, Abbas Rahi c a

Faculty of Environment and Energy, Islamic Azad University Science and Research Branch, Tehran, Iran MLC Research and Development Center, MAPNA Group Co., Tehran, Iran c Faculty of Mechanical & Energy Engineering, Shahid Beheshti University, Tehran, Iran b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 16 January 2019 Received in revised form 19 July 2019 Accepted 15 September 2019 Available online 17 September 2019

Emissions from biodiesel combustion depend on types of feedstocks. This study investigated physicochemical properties of biodiesels in three various feedstocks generations and the effect of them on emissions and performance of the unmodified engine. Methyl esters from Eruca sativa (ES) which has crops with short production cycle and drought-tolerant capacity, waste cooking oil (WCO) as an economic feedstock, and microalgae Chlorella vulgaris (MCV) which have high growth rate and productivity without farmland requirement, were produced by transesterification process with methanol and KOH catalyst. Physicochemical properties of these biodiesels were determined by GC-MS and FTIR analysis and evaluated with ASTM D6751 standard. FAME components profile illustrated the high value of oleic acid (C18:1) in ES and WCO and long-chain fatty acids (C18:2 and higher) in MCV. The engine tests results indicated that MCV biodiesel produced slightly lower power and higher BSFC compared with others. There was a slight increase in NOx for MCV biodiesel compared with pure diesel. Conversely, ES and WCO biodiesels had a reduction in NOx. On the other hand, MCV biodiesel resulted in the greatest reduction in CO and HC emissions. Based on the results, MCV blends had the lowest emissions and the best function among all feedstocks. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Chlorella vulgaris Waste cooking oil Eruca sativa GC-MS FTIR Exhaust emissions

1. Introduction Biodiesel is one of the greatest prominences over petroleum fuel with sulfur-free and adequate oxygen content, which has a comparatively easier manufacturing process and reduces GHG emissions. Nowadays, due to production cost and local conditions, many potential sources are being used as feedstocks for biodiesel production [1]. Common feedstocks can be divided into edible and non-edible vegetable oil, animal fats, waste or recycled oil, and algae or microalgae [2e4]. The use of edible vegetable oils as the first generation feedstocks, such as soybeans, sunflower, palm, and rapeseed has been € considered by many studies [5e8]. Ozener et al. [9] considered performance and emissions of a single-cylinder engine fueled with B10, B20, and B50 blends of soybean biodiesel. Their results demonstrated that while CO, HC, and NOx emissions significantly declined, CO2 emissions and BSFC increased slightly. Chong et al.

* Corresponding author. E-mail address: [email protected] (S. Tayari). https://doi.org/10.1016/j.renene.2019.09.068 0960-1481/© 2019 Elsevier Ltd. All rights reserved.

[10] conducted an experimental investigation on a direct injection engine with palm biodiesel. Their experiment results showed a reduction in NOx emissions and in thermal efficiency with the addition of biodiesel blends. Aldhaidhawi et al. [11] reported that rapeseed biodiesel had a significantly lower PM while higher CO2 and NOx rather than pure diesel. As a result of being competitive with food resources, consideration of edible vegetable oils for producing biodiesel is going to be less; therefore, non-edible vegetable oils, waste oil, as well as animal fats, are considered as the second generation biodiesel feedstocks for substituting traditional edible food crops [12]. High SFA (Saturated Fatty Acids) content in animal fats, which tend to be solid wax, results in problematic production [13]. Additionally, researches on animal fats biodiesel production are not as extensive as on vegetable oils due to inadequate availability of them [14,15]. Therefore, the share of waste oil and non-edible plant oil such as Jatropha, cottonseed, and neem as biofuel feedstocks will be significant. Rahman et al. [16] and Chauhan et al. [17] revealed that Jatropha biodiesel blends reduced CO and HC emissions, but slightly increased NOx and fuel consumption. Hirsute et al. [18] considered performance and emissions of waste fried oil biodiesel

S. Tayari et al. / Renewable Energy 147 (2020) 1058e1069

Nomenclature BSFC BTDC B(X) CA CI CN CO CO2 ES FAME

Brake specific fuel consumption Before top dead center X% biodiesel þ (100-X)% diesel Crank angle Compression ignition Cetane number Carbon monoxide Carbon dioxide Eruca sativa Fatty acid methyl ester

on a single-cylinder diesel engine. Results indicated that performance parameters for different blends were almost similar to diesel and the average reduction of CO emissions was determined 21e45% for different blends. Recently, as a consequence of high oil content, yield and growth rate, and productivity without the requirement of farmland or freshwater, attentions have shifted to algae and microalgae biodiesel production [19e22]. Other advantages of utilizing microalgae as a biofuel feedstock include CO2 sequestration, selfpurification, and potentially valuable co-products such as fertilizer, antioxidants or pigments [23e25]. Hence, all phases of microalgae biodiesel production will cut down the total greenhouse gas emissions and its role should not only be limited to exhaust emissions. In addition, this superior feedstock can grow with wastewaters derived from municipal and industrial activities, which potentially provide a cost-effective and sustainable product. Demirbas¸ [26] considered oil extraction and chemical properties of a macroalgae Cladophora fracta and a microalgae Chlorella protothecoides. He found that heating value and polyunsaturated fatty acids of Chlorella protothecoides were considerably higher than Cladophora fracta. Al-lwayzy et al. [27] investigated the performance and emissions of the CI engine fueled with microalgae Chlorella protothecoides biodiesel. Their analyses showed that Chlorella protothecoides had a reduction in power, CO, CO2, and NOx emissions. In subsequent work, the authors [28] found that Chlorella vulgaris biodiesel had significantly lower exhaust gas temperature, NOx, and CO2 emissions in the engine compared with cottonseed biodiesel. Singh et al. [29] compared marine microalgae Chlorella variabilis cultivated in salt pans and wastelandcompatible Jatropha biodiesel. Their test results showed that NOx emissions of microalgae biofuel were 17% lower than Jatropha biodiesel. Mathimani et al. [30] evaluated the performance and emissions of a single-cylinder engine fueled with Chlorella vulgaris biodiesel blends. Their results demonstrated an evident reduction in CO, CO2, NOx, and HC emissions compared with diesel. The assessments of feedstocks biodiesel in some researches are shown in Table 1. Some studies have stated increase in NOx emissions with biodiesel compared with pure diesel [28,33,35,49,55] whereas others have reported reduction [9,32,37,40,41,44,50e54, 56,58]. Furthermore, the results demonstrated a reduction in CO emissions in the majority of studies except for a few ones [34,38,51,53,61]. As can be seen in Table 1, the experimental tests were not conducted in the same conditions and the results are different even for the same feedstock. There are some review studies [1,2,7,15,61e64] which compare physicochemical properties of different generation feedstocks and the effects of them on emissions and performance of the engine. However, results achieved from different experimental processes cannot simultaneously provide a comprehensive comparative

GHG HC HTL KOH MCV NOx PM rpm SFA TDC WCO

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Greenhouse gas Hydrocarbon Hydrothermal liquefaction Potassium hydroxide Microalgae Chlorella vulgaris Nitrogen oxides Particulate matter Revolutions per minute Saturated Fatty Acids Top dead center Waste cooking oil

analysis for consideration (the relevant variations caused by the different transesterification routes, engine power, and speed during the tests of biodiesel production). Furthermore, a few studies [6,38,39,65e71] compare biodiesel from edible and non-edible oils (first and second generations) including their use as a fuel in diesel engines. However, there is a paucity of literature on the comparative assessment of three different generations (edible, non-edible or waste oil and microalgae biodiesel). Therefore, the physicochemical properties of different blends of Eruca sativa (first generation), waste cooking oil (second generation), and microalgae Chlorella vulgaris (third generation) and their performance and emission characteristics in a diesel engine with variable engine speeds were compared for the first time in the present study. These three biodiesels were selected for evaluation as follows: - Eruca sativa (ES) feedstock has not only crops with short production cycle but also the drought-tolerant capacity. - Waste cooking oil (WCO) biodiesel can contribute to the reduction of environmental impacts of WCO disposal. It reduces the economic load related to the operational problems in municipal sewage treatment plants. Moreover, it contributes a small but non-negligible fraction of renewable energy to society and has promising potentials [45]. - Microalgae Chlorella vulgaris (MCV) biodiesel does not compromise the production of food and other products derived from crops and has a high growth rate and oil content. The comparison of biodiesels from these three alternative feedstocks offers the possibility of defining the cleanest and the most efficient biodiesel feedstock. 2. Material and methods 2.1. Biodiesel preparation The production of biofuels was carried out in the laboratory where the main physical and chemical characteristics of the fatty acid composition and primary fuels were examined. The oils of these materials for biodiesel production were:
ES oil extraction was carried out using n-Hexane as the solvent. In this optimized process, seeds were placed in Soxhlet extractor by the boiling solvent for about 5e6 h. To separate the oil from the solvent, a rotary separator was used at 70  C. The purity of oil was approximately 35% in this method.
WCO was supplied by an authorized waste oil collector from restaurants and food industries. Treatment and filtration of solid particles from waste oil were done into the laboratory of Chemistry Department at Azad University Tehran North Branch.

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Table 1 Review of current researches in emissions and performance of the engine fueled with biodiesel from different generation feedstocks. Feedstock

First Generation

Reference

Vegetable oil E. sativa

Waste oil

Third Generation

Microalgae

B10, B20, B50, B100 B10 B10, B20, B50 B10, B20, B30, B40 B5, B20, B50, B85 B100 B100 B5, B20, B70, B100 B20, B50 B100 B100 B5, B10, B20, B30 B5, B10, B15, B20 B10, B20 B10, B20, B30, B50 B10, B20, B40, B50 B100 B20, B50 B30, B50, B100 B100 B10 B20, B100 B25, B50, B75 B20, B40, B80, B100 B5, B10 B10, B30, B50 B5 B10, B20, B50 B30 B100, B20 B30, B40, B50, B60 B10, B15, B20 B2 B20, B50, B100 B100

Engine operation

3200 rpm 5.88 kW at 2600 rpm 1200e3000 rpm Full load, 1400e2100 rpm 9.6e35.7 kW 250 bar at 2400 rpm 250 bar at 2400 rpm Full load, 1000e2100 rpm 1200,1800, 2200 rpm 1500 and 2000 rpm 20% to full load 1000e4000 rpm 1400e2200 rpm Full load 1500e2400 rpm 1900 rpm Full load, 1750e4400 rpm 1300 rpm 600 Nm, 1100, to 1700 rpm Full load, 1500 rpm Full load, 800e3600 rpm Full load, 1000e2400 rpm 0e25 kW 1500 rpm, 0e5 kW 0.12e0.48 MPa, 2200 rpm Full load, 1000e2000 rpm Full load, 1000e2500 rpm 2000 rpm, 25% to Full loads 1500 rpm, full load 3670 rpm, full load 1500 rpm, full load Variable load 2200 rpm, 50% load 1700 to 2900 rpm 1500 rpm, Variable load

Emissions % (vs diesel)

Engine power

NOx

HC

CO

CO2

2.38 to 13.21 108 6.95 to 17.62 5 e 20 11 6 to 12 15.65 to 20.54 0.3 to 4.5 23 for B20 11.32 for B20 4 for B20 27.25 99.05 for B50 0.55 e 20.6 to 44.8 e 11 to 66 19 4.8 for B50 18.33 6.4 to 8.7 4.7 to 19.0 24 22 for B50 0 60.94 1 for B50 38 2 2.4 13

4.76 to 33.3 e e 27 9 to 18 e e e 18.19 to 32.28 17 to 23 22.6 for B20 - 48 for B20 7.9 for B20 - 7.4 e e 26.7 22.9 to 16.4 9.52 to 14.29 33 24.7 23.5 for B50 57 2 to 29 e 28 50 for B50 - 25 to 5 e 13 for B50 31 - 50.2 e 27

33.3 30 28 to 46 27 28 to 48 33 25 12 to 35 2.59 to 35.21 20 to 25 19.6 for B20 - 53.06 for B20 21 for B20 - 16.3 150 for B50 17.14 18.6 5.2 to 9 72.68 to 86.89 300 e 20.1 for B50 - 31 11.8 to 51 3.3 to 26.3 e e 10 e 40 for B50 20 - 0.34 12.3 31

0.60 to 10.71 160 1.46 to 5.03 e 0.89 to 1.48 e e e e e 20 for B20 e 3 for B20 13.08 - 40 for B50 8.05 e e 1.74 to 1.74 11 to 31 e 8.5 for B50 e 3.3 to 5 8.7 to 38.5 8.5 e e 11.6 18.6 for B50 e e 0.7 e

e e 1 to 4 5 e 12.9 2.5 - 5 to 10 0.05 to 3.8 3.5 to 0.2 e 3.69 for B20 12 for B20 4.5 16.01 for B50 0.55 e e e 10 1.1 e e e 1.6 to 6.7 e e e 15.1 e e 1.2 3.09

S. Tayari et al. / Renewable Energy 147 (2020) 1058e1069

Second Generation

Li et al. [31] Chakrabarti et al. [32] € Soybean Ozener et al. [9] Qi et al. [33] Valente et al. [34] Çelikten et al. [35] Rapeseed Çelikten et al. [35] Buyukkaya [37] Jatropha Sahoo et al. [38] Huang et al. [39] Chauhan et al. [40] Palash et al. [41] Sanjid et al. [42] Ong et al. [43] Dharma et al. [44] Zafer et al. [45] Meng et al. [46] Lujan et al. [47] Ozsezen et al. [48] An et al. [49] Lin et al. [50] Valente et al. [51] Gopal et al. [52] Can [53] Chuah et al. [54] Khalife et al. [55] C. cohnii Islam et al. [56] Chlorella sp. Makareviciene et al. [57] Chlorella vulgaris Al-lwayzy et al. [28] Mathimani et al. [30] Patel et al. [58] Mwangi et al. [59] Chlorella Al-lwayzy et al. [27] protothecoides Satputaley et al. [60]

Biodiesel blends

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Fig. 1. Experimental photobioreactor process of biomass production.


Unicellular with 5e10 mm size makes Chlorella vulgaris suitable for combining in a renewable fuel [72]. MCV was cultivated in photobioreactor depicted in Fig. 1. After harvesting, a centrifuge machine and a dryer were employed for complete drying of biomass. For oil extraction, similarly as in ES oil extraction, dried biomass was placed in the reservoir located in Soxhlet extractor by the boiling solvent for about 4 h and n-Hexane submerged the biomass and dissolved lipids. The mixture of hexane and oil could be separated based on their boiling point by a rotary in which the temperature was slightly above the boiling point of alcohol. These three oil samples were converted into methyl esters through transesterification process with methanol in the presence of KOH as a catalyst which is shown in Fig. 2. Treated oils were mixed with methanol (99.5% with a molar ratio 1:6) containing 1% of the oil weight KOH catalyst at the temperature of 65e70  C for about 2 h at the continuous stirring speed of 400 rpm. After the reaction, a mixture of biodiesel, glycerol, and other minor products such as mono-, di-, and tri-glycerides was obtained. Flask contents

were poured into the separating funnel for several hours at room temperature until the glycerol as a valuable by-product of the ester was isolated [65]. The final products were leached with deionized water (30% of oil weight) to remove unreacted methanol and catalysts. Moisture was removed from biodiesel by absorbents such as inorganic salts (sodium sulfate, anhydrous). The finished biodiesel was characterized by being transparent, clear color, and no impurities or deposits. Each biodiesel sample was blended with diesel fuel at different proportions to be used as fuel in engine tests. Three different mixtures of fuel for each biodiesel sample (B5, B10, and B20) were used in engine tests and compared with pure diesel fuel (B0). 2.2. Experimental setup The experimental analysis was carried out on a single-cylinder, four-stroke diesel engine, Lombardini 3LD 510, with main parameters are shown in Table 2. The biodiesel fuel was injected at a pressure of 200 bar and injection timing of 24 BTDC. The adjustment was performed by changing the shims in the injection pump.

Fig. 2. Process of biodiesel production from feedstocks.

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S. Tayari et al. / Renewable Energy 147 (2020) 1058e1069 Table 2 Technical specifications of the engine. Engine model

3 LD 510 Lombardini

Engine Type Cylinder Number Stroke Volume Bore x Stroke Compression Ratio Maximum Power Maximum torque Fuel injection timing Fuel injection pump Nozzle operation Type of cooling Combustion chamber

4-Stroke, Direct Injection 1 510 cc 85  90 mm 17.5: 1 9 @3000 kW@rpm 32.8@1800 N-m@rpm 24  CA BTDC Mechanical pump, Housing with plunger and barrel assembly with Roller Tappet Assy., 3 Plunger Pump Hole Type with Ring Groove, Long Shank without Ring Groove, 160 Spray Angle, 200 bar Forced-air cooling Hemispherical open type

In this study, there was no modification in the injection system. All engine tests were accomplished in the laboratory of Agriculture Faculty at Tarbiat Modares University. The schematic diagram of the experimental setup is shown in Fig. 3. The engine was coupled to a dynamometer with a maximum measuring torque of 80 Nm and a load sensor device measuring the load on the dynamometer. For each sample, performance and emission tests were conducted at the full load condition with variable engine speeds (2000-3000 rpm) and with emission tester MAHA MGT5 determining the exhaust gas emissions (CO, CO2, HC, and NOx). 2.3. Experimental errors analysis Errors in experimental tests can be induced by environmental conditions, observation, and equipment quality [73]. In order to

enhance the accuracy of the analyses, tuning and calibration of the instruments should be carried out by the technician. Thus, FT-IR device was calibrated by polystyrene film, which covered the complete range of IR region. Furthermore, calibration of the GC-MS instrument was done by specific concentrations of Decafluorotriphenylphosphine and p-Bromofluorobenzene. Tester MAHA gas analyzer was calibrated with standard gases and zero gas. In order to have more accurate emission measurements, oil and air filter were changed with new ones after each engine test, the fuel tank was cleaned before changing the liquid fuel, and then the injection pressure was calibrated. In addition, before testing, the engine was allowed to run for an adequate period to consume remained fuel and to reach steady-state conditions. Furthermore, the test for each sample continued until concentrations of exhaust gas touched a fixed amount in the gas analyzer. All tests were repeated three times in the same conditions and the low deviations were observed. Measurement uncertainty is a parameter to describe of quantifying possible errors and to combine the results with the aim of obtaining an estimate different from the accurate value [74]. Based on the root mean square method, the total uncertainty of the experiments is calculated as follows [75]:

vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi u n  2 uX vu DU ¼ t Dxi vxi i

(1)

where DU is the estimated value of quantity u, depending on the variables xi with individual error Dxi. Resolution and uncertainties percentage of parameters are shown in Table 3.

3. Results and discussion 3.1. Fuel properties

Fig. 3. Schematic diagram of the experimental setup and laboratory devices.

The fatty acid methyl ester (FAME) of each fuel was determined by GC-MS analysis in the range of C16 to C18 and is shown in Table 4. The most prominent FAME found in ES and WCO biodiesels was methyl oleic (C18:1) with 28.3 and 38 wt%, respectively. This leads to better oxidative stability with no influence on cold flow properties [76]. WCO methyl ester was found similar in palmitic fatty acids (C16:0) to ES biodiesel with 29.4 wt%. The presence of these shorter FAME results in more complete combustion [63]. On the other hand, longer FAME length results in a shorter ignition delay, which leads to lower heat release rate and produces less NOx during combustion compared with shorter chained ones [36]. The biodiesel obtained from microalgae oil differs from plant oils in both distribution and structure of fatty acids. MCV biodiesel had the highest diversity of long carbon chain length, containing a

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Table 3 Uncertainty analysis of the experimental test. Parameters

Measurement device

Range

Resolution

Uncertainty (%)

CO (%) CO2 (%) HC (ppm) NOx (ppm) Engine Torque (Nm) Engine Speed (rpm)

Gas analyzer MAHA MGT5

0e15% Vol. 0e20% Vol. 0e20000 ppm 0e5000 ppm 0-100 Nm 0e5000 rpm

0.01 0.01 1 1 0.2 1

0.06 0.05 0.005 0.02 0.5 0.2

Dynamometer loading unit Speed encoder unit

Table 4 Fatty acid compositions of different feedstocks biodiesel. Fatty acids

Chemical formula

Contents (%) ES Biodiesel

WCO Biodiesel

MCV Biodiesel

C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 Other

C16H32O2 C16H30O2 C18H36O2 C18H34O2 C18H32O2 C18H30O2 e

28.3 0.4 2.5 28.3 22.7 12.4 5.4

29.4 0.3 4.2 38.0 21.4 1.5 5.2

16.5 1.6 10.4 21.8 31.6 13.2 4.9

(palmitic) (palmitoleic) (stearic) (oleic) (linoleic) (linolenic)

(CH₃(CH₂)₁₄COOH) (CH₃(CH₂)₅CH]CH(CH₂)₇COOH) (C₁₇H₃₅CO₂H) (CH3(CH2)7CH]CH(CH2)7COOH)

Table 5 Functional group frequencies of biodiesels identified. Types of vibration

Functional groups

Wavenumber (cm1) ES

WCO

MCV

stretching asymmetric stretching asymmetric stretching asymmetric stretching stretching bending bending and rocking

OeH (alcohols) ¼ CeH (alkenes) CeH (alkanes) CeH (methylene) C¼O (ester carbonyl) C ¼C (aromatic) CeH (methyl)

stretching

CeO (alkoxy esters, ethers)

out of plane bending out of plane bending bending of alkenes and overlapping of rocking vibration of methylene out of plane bending

¼ CeH (trans-disubstituted alkene) ¼ CeH (alkenes) e(CH2)n and ¼ CeH (methylene, cis disubstituted alkenes) ¼ CeH (cis-disubstituted alkene)

3467.75 3007.54 2925.67 2854.41 1744.00 1684.56 1320.09 e1464.77 1101.77 e1247.57 1014.54 880.42 722.40

3468.03 3007.46 2925.06 2854.33 1743.78 1627.14 1363.50 e1465.22 1117.33 e1247.8 1015.23 880.95 722.61

3466.87 3008.12 2924.91 2854.06 1742.83 1608.47 1363.89 e1463.265 1169.83 e1248.21 1013.44 882.04 720.83

586.7

585.45

585.45

significant amount of FAME derived from C16:0 (16.5 wt%), C18:1 (21.8 wt%), and C18:2 (31.6 wt%) fatty acids. The FTIR spectroscopy helps to recognize the structure of FAME component in the biodiesel and reveals the presence of alcohol, methyl, aromatic, alkyne groups, alkene, acid, and ether in samples [77]. Table 5 shows peaks from FTIR spectra of biodiesels identified in Fig. 4. Physical properties of the biodiesel compared with neat diesel and ASTM D6751 standard are shown in Table 6. Each biodiesel density, influenced by the chain length, was in the ASTM standard range. All samples in this study were within the acceptable range of kinematic viscosity (1.9e6.0 mm2 s1). While MCV biodiesel had the minimum kinematic viscosity at 3.7 mm2 s1 among other biodiesels, WCO was measured as the maximum at 5.03 mm2 s1. One of the important factors for the quality of fuel is energy density, which is expressed as the heating value. ES biodiesel had the highest heating value (43.7 kJ g1) among the biodiesel fuels tested, although it was slightly lower than diesel (46.8 kJ g1). Biodiesel from both WCO and MCV were found to have the heating value respectively 3.45% and 5.09% less than that of ES. Moreover, MCV biodiesel had the highest cetane number (CN), followed by ES and WCO with 47.5 and 46.6, respectively.

It should be mentioned that it is difficult to anticipate the CN in fuels containing a substantial amount of branched-chain fatty acids since the CN in biodiesel is dependent on the proportion of straight-chain fatty acid esters. Consequently, the differences, which could be seen in WCO performance or emissions while applying it in an engine, might not be clarified with the predicted CN [78]. 3.2. Performance characteristics One of the most significant methods for evaluation of alternative fuel is the analogy of an engine performance while using it instead of fossil fuels. Figs. 5 and 6 illustrate the engine power and torque under full load operation at 2000e3000 rpm speed range. Due to the lower heating value of biodiesel, the engine brake power and torque decreased for all blends of biodiesels [15]. The maximum power output of diesel fuel was measured at 8.48 kW at 3000 rpm. Compared with other biodiesels, the highest power output was achieved by ES biodiesel and ES-B5 blend had 97.8% of the diesel output. On the other hand, the minimum result belonged to MCVB20, which produced 78.9% of the diesel output. These proportions for WCO were in the Mid-range of three biodiesels. WCOeB5,

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Fig. 4. FT-IR spectrum of a) MCV b) WCO c) ES biodiesel.

Table 6 Physical properties of biodiesels in comparison with ASTM standard and neat diesel. Property

standard ASTM

Diesel

ES Biodiesel

WCO Biodiesel

MCV Biodiesel

Flash point ( C) Pour point ( C) Density (g/cm3) Viscosity (cSt) Sulfur content (%) Acid value (mg KOH/g) Cetane number Calorific value (MJ/kg)

120, min. 10 to 15 0.86e0.90 1.9e6.0 0.15 max. 0.8 47 min. N/A

88 7 0.83 3.1 N/A N/A 46.2 46.8

185 10 0.87 4.19 0 0.11 47.5 43.7

183 1 0.86 5.03 0.04 0.14 46.6 40.3

124 15 0.86 3.7 N/A 0.4 51.4 38.7

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Fig. 5. Engine power of diesel and biodiesel blends at various engine speeds.

Fig. 6. Engine torque of diesel and biodiesel blends at various engine speeds.

Fig. 7. BSFC of diesel and biodiesel blends at various engine speeds.

WCOeB10, and WCOeB20 blends achieved 89.1%, 87.6% and 86.5% of pure diesel, respectively. As can be seen in Fig. 6, the maximum torque of almost 28.86 Nm was achieved by diesel at 2000 rpm. The torque of ES-B5 at 2000 rpm was 28.26 Nm, 2.1% lower than that of pure diesel. Similar to the power, the lowest torque belonged to MCV-B20 with 9.8% reduction.

observed with MCV-B20 at 12.2% compared with diesel. The average reductions of this amount for ES-B20 and WCO-20 were 3.3% and 6.5%, respectively. 3.4. Emission characteristics

3.3. BSFC and exhaust gas temperature

Owing to biodiesel properties such as density, viscosity, boiling point, surface tension, CN, and carbon chain length, emissions of biodiesel are varied for each feedstock and less than diesel.

Brake specific fuel consumption (BSFC) is depicted in Fig. 7 for each biodiesel blend. It can be concluded that raising the biodiesel content in fuel blends, BSFC increased due to the lower calorific value and higher oxygen content of the biodiesel compared with pure diesel. BSFC of ES-B5 with 3.0% increase was the nearest one to pure diesel. Furthermore, the maximum average BSFC belonged to MCV-B20, which was 15.2% higher than pure diesel. The average BSFC of ES-B10, ES-B20, WCOeB10, WCOeB20, and MCV-B10 was 4.1%, 6.3%, 8.8%, 11.0% and 14.0% higher than B0, respectively. Fig. 8 shows exhaust gas temperature of biodiesel blends with variations of the engine speed compared to diesel fuel. As expected, exhaust gas temperatures of each biodiesel fuel were significantly lower than diesel. The lower amount of exhaust gas temperatures was

3.4.1. CO and CO2 Fuel combustion with the absence of oxygen content and lower temperature produces CO emissions. Fig. 9 shows the variation in CO emissions of diesel and biodiesel blends with the variations of engine speeds. It was observed that biodiesel blends significantly reduced CO emissions compared to diesel. Based on Fig. 9, microalgae Chlorella vulgaris biodiesel blends produced lower amounts of CO emissions compared with waste cooking oil and Eruca sativa biodiesel blends. The average lowest amount of CO emissions was produced by MCV-B20, which was 47.4% lower than B0. The average reduction in CO emissions for ES-B10, ES-B20, WCOeB10, WCOeB20, and MCV-B10 compared with diesel was 22.1%, 30.9%, 29.9%, 38.0%, and 41.7%, respectively. As a consequence of high

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Fig. 8. Exhaust gas temperature of diesel and biodiesel blends at various engine speeds.

percentage of ES and WCO biodiesel blend. The average rise in CO2 emissions for ES-B10, ES-B20, WCOeB10, and WCOeB20 compared with B0 were 8.4%, 10.9%, 11.4%, and 14.3%, respectively. One of the reasons that make the CO2 content higher in WCO and ES is converting CO into CO2 due to complete combustion. On the other hand, the MCV biodiesel had the opposite behavior. The minimum CO2 belonged to MCV-B20 with 5.3% reduction compared to diesel.

Fig. 9. CO emissions of diesel and biodiesel blends at various engine speeds.

Fig. 10. CO2 emissions of diesel and biodiesel blends at various engine speeds.

oxygen content and higher viscosity in biodiesel, complete consumption occurred, leading to the decrease of CO emissions [15]. The CO2 emissions of different biodiesel blends are shown in Fig. 10. The amount of CO2 emissions was increased with the rising

3.4.2. HC The main causes of HC emissions production are less ignition temperature and incomplete combustion [79]. Moreover, the ignition temperature of the fuel is augmented by high oxygen content in biodiesel [15]. Fig. 11 shows the test results of HC emissions for diesel and different biodiesel blends at different engine speeds. From the results, the trends of HC emissions from the engine using different fuels were similar and declined with rises in engine speed. The best improvement of HC emissions occurred in MCV-B20 (51.1%) followed by MCV-B10 (44.3%) and WCOeB20 (42.7%). The average HC emissions of ES-B10, ES-B20, and WCOeB10 were respectively 28.2%, 38.2%, and 36.6% lower than pure diesel. Due to very long-chained fatty acids and high oxygen content in microalgae biodiesel, HC emissions of this fuel sample were considerably lower than other feedstocks. 3.4.3. NOx The key factors to the formation of NOx are the combustion temperature, ignition delay, and the physical and chemical properties including viscosity, density, and oxygen content of the fuel [80]. Fig. 12 shows the NOx emissions for diesel and different biodiesel blends with the variations of engine speeds. Based on the results, the reduction of NOx emissions for ES-B10, ES-B20, WCOeB10, and WCOeB20 were respectively 5.3%, 7.3%, 8.9%, and 13%, compared with pure diesel. MCV demonstrated an opposite behavior in NOx emissions with an increase of 1.9% and 5.1% for MCV-B10 and MCV-B20 compared with diesel. The formation of NOx can be explained by the amount of oxygen in biodiesel. Generally, high oxygen content leads to higher combustion gas temperatures and NOx formation. It has also been proposed that the higher bulk modulus, compressibility, viscosity, and density in the fuel blends containing biodiesel impact the injection timing, and the improvement of injection timing increases the NOx

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Fig. 11. HC emissions of diesel and biodiesel blends at various engine speeds.

emissions [81]. Fig. 13 summarizes the differences in the average performance and emissions of biodiesel from various feedstocks and their blends compared with pure diesel.

4. Conclusion This paper presented the process of preparing and characterizing the physicochemical properties of three different biodiesel generations and their blends with pure diesel. These biodiesels were evaluated with regular diesel and ASTM D6751 standard and their blends (B5, B10, and B20) were tested in unmodified diesel engine for evaluation performance and exhaust emissions. The experimental results give the following conclusions: Fig. 12. NOx emissions of diesel and biodiesel blends at various engine speeds.


Microalgae Chlorella vulgaris methyl ester contains the longest chain fatty acids among other feedstocks.

Fig. 13. Averaged engine performance and exhaust emissions of biodiesels differences compared with diesel.

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ES biodiesel has a higher calorific value and engine performance output. The lowest power belongs to MCV, which produces 78.9e86.1% of the output achieved by diesel.
The maximum increase of BSFC belongs to MCV (15.2%), which is consistent with their lower calorific value and higher oxygen content.
CO emissions from all samples are lower than pure diesel and the most reduction in CO belongs to MCV.
WCO and ES biodiesels have higher CO2 emissions compared to pure diesel. However, MCV shows the opposite behavior with a 5.3% reduction.
The test analyses show that the effect of biodiesels in HC emissions is statistically significant, and MCV results in the greatest reduction by 51.1%.
Contrary to ES and WCO, the NOx emissions in MCV biodiesel are 5.1% higher than pure diesel. In conclusion, these results show that while MCV-B20 reduces the engine performance slightly, it has lower exhaust emissions amongst the other three samples and can be used in vehicles without any substantial modifications. Acknowledgment The authors are thankful for the opportunities in order to use the laboratories in “Azad University, Tehran North Branch, Faculty of Chemistry” and “Tarbiat Modares University, School of Agriculture”. References [1] A.S. Silitonga, H.H. Masjuki, T.M. Mahlia, H.C. Ong, W.T. Chong, M.H. Boosroh, Overview properties of biodiesel diesel blends from edible and non-edible feedstock, Renew. Sustain. Energy Rev. 22 (2013) 346e360. [2] N. Kumar, S.R. Chauhan, Performance and emission characteristics of biodiesel from different origins: a review, Renew. Sustain. Energy Rev. 21 (2013) 633e658. [3] M. Lapuerta, O. Armas, J. Rodriguez-Fernandez, Effect of biodiesel fuels on diesel engine emissions, Prog. Energy Combust. Sci. 34 (2) (2008) 198e223. [4] A. Chhetri, M. Tango, S. Budge, K. Watts, M.R. Islam, Non-edible plant oils as new sources for biodiesel production, Int. J. Mol. Sci. 9 (2) (2008) 169e180. [5] M.S. Graboski, R.L. McCormick, Combustion of fat and vegetable oil derived fuels in diesel engines, Prog. Energy Combust. Sci. 24 (2) (1998) 125e164. [6] M.U. Kaisan, F.O. Anafi, J. Nuszkowski, D.M. Kulla, S. Umaru, Calorific value, flash point and cetane number of biodiesel from cotton, jatropha and neem binary and multi-blends with diesel, Biofuels 1 (2017) 1e7. [7] M. Mofijur, A.E. Atabani, H.A. Masjuki, M.A. Kalam, B.M. Masum, A study on the effects of promising edible and non-edible biodiesel feedstocks on engine performance and emissions production: a comparative evaluation, Renew. Sustain. Energy Rev. 23 (2013) 391e404. , Exhaust emissions from a diesel powered vehicle [8] M.L. Randazzo, J.R. Sodre fuelled by soybean biodiesel blends (B3eB20) with ethanol as an additive (B20E2eB20E5), Fuel 90 (1) (2011) 98e103. € € [9] O. Ozener, L. Yüksek, A.T. Ergenç, M. Ozkan, Effects of soybean biodiesel on a DI diesel engine performance, emission and combustion characteristics, Fuel 115 (2014) 875e883. [10] C.T. Chong, J.H. Ng, S. Ahmad, S. Rajoo, Oxygenated palm biodiesel: ignition, combustion and emissions quantification in a light-duty diesel engine, Energy Convers. Manag. 101 (2015) 317e325. [11] M. Aldhaidhawi, R. Chiriac, V. Badescu, Ignition delay, combustion and emission characteristics of Diesel engine fueled with rapeseed biodieseleA literature review, Renew. Sustain. Energy Rev. 73 (2017) 178e186. [12] I.B. Bankovi c-Ili c, I.J. Stojkovi c, O.S. Stamenkovi c, V.B. Veljkovic, Y.T. Hung, Waste animal fats as feedstocks for biodiesel production, Renew. Sustain. Energy Rev. 32 (2014) 238e254. [13] H. Pehlivanoglu, M. Demirci, O.S. Toker, Rheological properties of wax oleogels rich in high oleic acid, Int. J. Food Prop. 20 (sup3) (2017) S2856eS2867. [14] J. Janaun, N. Ellis, Perspectives on biodiesel as a sustainable fuel, Renew. Sustain. Energy Rev. 14 (4) (2010) 1312e1320. [15] W.N. Ghazali, R. Mamat, H.H. Masjuki, G. Najafi, Effects of biodiesel from different feedstocks on engine performance and emissions: a review, Renew. Sustain. Energy Rev. 51 (2015) 585e602. [16] S.A. Rahman, H.H. Masjuki, M.A. Kalam, M.J. Abedin, A. Sanjid, S. Imtenan, Effect of idling on fuel consumption and emissions of a diesel engine fueled by Jatropha biodiesel blends, J. Clean. Prod. 69 (2014) 208e215. [17] B.S. Chauhan, N. Kumar, H.M. Cho, A study on the performance and emission of a diesel engine fueled with Jatropha biodiesel oil and its blends, Energy 37

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