Diesel engine performance and exhaust gas emissions using Microalgae Chlorella protothecoides biodiesel

Renewable Energy 101 (2017) 690e701

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Diesel engine performance and exhaust gas emissions using Microalgae Chlorella protothecoides biodiesel Saddam H. Al-lwayzy a, b, *, Talal Yusaf a a b

National Centre for Engineering in Agriculture (NCEA), University of Southern Queensland, Toowoomba 4350, QLD, Australia Department of Agricultural Machinery, College of Agriculture and Forestry, University of Mosul, Al-Majmoa'a Street, Mosul 09334, Iraq

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 February 2016 Received in revised form 31 August 2016 Accepted 17 September 2016

Microalgae biodiesel has captured the attention as a clean renewable fuel for diesel engines due to their positive characterizations such as high productivity, fast growing rate and their ability to convert CO2 to fuel. This work investigates the use of microalgae biodiesel from Chlorella Protothecoides (MCP-B) as alternative fuel for Compression Ignitions (CI) engines. Engine performance and emissions along with the fuel properties of the MCP-B100, MCP-B50, and MCP-B20 were evaluated and compared with petroleum diesel (PD). Analysis of variance statistical test (ANOVA) was conducted to evaluate the significance of the differences between the parameters means. The results showed that MCP-B100 produces less emission compared to PD. Statistically significant differences were found in the engine brake power, torque, BSFC, exhaust gas temperature, CO, O2 and NOx when MCP-B100 and its blends were used compare to PD. MCPB100 showed a reduction of 7, 4.9, 6.1, 28, 4.2 and 7.4% in brake power, torque, exhaust gas temperature, CO, CO2 and NOx, respectively. Contrarily, the use of MCP-B100 resulted in an increase of 10.2 and 15.8% in BSFC and O2, respectively compared to PD. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Microalgae Chlorella protothecoides Biodiesel Fuel properties Engine performance Exhaust gas emissions ANOVA test

1. Introduction Biodiesel is the most potentially attractive fuel for diesel engines and has been proven to operate diesel engines without modifications [1e3]. Producing biodiesel from vegetable oil or from other edible sources has a direct significant impact on human food prices. On the other hand, using non-edible feedstocks as source for fuel, indirectly impact the human food production by using large lands and consuming fresh water for irrigation. Furthermore, crops biodiesel, waste cooking oil or animals fat are limited and cannot cover the transportation demand for oil [4]. Therefore, the alternative resource of biofuel has to fulfil the main requirements of high productivity, low impact on human food and environmentally friendly. It is reported that microalgae are the only alternative source of biomass feedstock for biodiesel that can meet the global demand of the transportation sector due to superior biomass productivity and high oil content. Microalgae have the ability to produce double biomass in a short time of about two days [5e7]. Some

* Corresponding author. National Centre for Engineering in Agriculture (NCEA), University of Southern Queensland, Toowoomba 4350, QLD, Australia. E-mail addresses: [email protected], [email protected] (S.H. Al-lwayzy). http://dx.doi.org/10.1016/j.renene.2016.09.035 0960-1481/© 2016 Elsevier Ltd. All rights reserved.

species of microalgae have high oil content of up to 80%. Microalgae production is an environmentally friendly method that involves CO2 sequestering from the atmosphere [7e9]. Each biodiesel has its own fatty acid methyl esters (FAMEs) that affect the biodiesel properties and consequently affect the engine performance and the quality of the emission [6,10,11]. Microalgae biodiesel has been reported to have similar fuel properties to other biodiesels [12] and can be an excellent alternative fuel for CI engines with minor modifications. However, the research work on the physical and chemical properties of microalgae oil and biodiesel and their behaviour in diesel engines still requires further investigations [13]. Haik, Selim and Abdulrehman [13] tested microalgae fuels in a Ricardo diesel engine and investigated the factors affecting the incylinder pressure wave and maximum in-cylinder pressure rise. They used PD, crude microalgae oil and biodiesel. In their study, microalgae oil and biodiesel reduced the engine performance and increase the engine noise. Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] assessed engine performance and emission using PD and biodiesel from soybean, microalgae (Chaetoceros gracilis), bacteria and yeast. However, the study was conducted under limited operating condition and the results of the exhaust gas emissions were only tested under no-load

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Abbreviations ANOVA Analysis of variance ATDC After top dead centre BP Brake power, British Petroleum BSFC Brake specific fuel consumption BTDC Before top dead centre CA Crank angle CO Carbone monoxide CO2 Carbone dioxide CP Chlorella protothecoides EG Temp.Exhaust gas temperature FAME Fatty acid methyl ester LSD Least significant difference MCP Microalgae Chlorella protothecoides NOx Oxides of nitrogen O2 Oxygen PD Petroleum diesel rpm Revolutions per minute TDC Top dead centre WOT Wide open throttle q Crankshaft angular displacement from TDC

conditions at 3500 rpm. Tüccar and Aydın [14] tested microalgae biodiesel in diesel engine and reported that, microalgae biodiesel can be used as alternative fuel in CI engines with less exhaust gas emissions. Chen, Huang, Chiang and Tang [15] and Satputaley, Zodpe and Deshpande [16] reported that MCP-B100 (from the Soley Institute) have physical and chemical fuel properties that meet the ASTM standards. Ozsezen, Canakci and Sayin [17] found that there was an insignificant difference in the maximum in-cylinder pressure between biodiesel and PD. In another study conducted by Ozsezen, Canakci, Turkcan and Sayin [18], the in-cylinder pressure was 0.45 MP at 1500 rpm at full load and found to be higher than that obtained from PD and 0.25
advance. The reasons for the pressure rise were the higher BSFC, cetane number and oxygen (O2) content and the advance in the ignition. The cetane number for biodiesel leads to easier auto-ignition [18,19]. Biodiesel spray, evaporation and atomisation are dramatically affected by the higher viscosity of biodiesel resulting in longer combustion duration [20,21]. Chokri, Ridha, Rachid and Jamel [22] reported a reduction in the engine power and torque by about 5% when biodiesel from waste vegetable oil was compared with PD. Similar reductions of 1e4% in engine torque was reported with biodiesel from soybean [21]. BSFC has been reported to be higher with biodiesel than PD because of the lower heating value of biodiesel [21,23,24]. Dorado, Ballesteros,
mez and Lo
pez [25] applied a statistical test that revealed Arnal, Go significant differences in the engine thermal efficiency and an increase in the BSFC with biodiesel from waste cooking olive oil compare to PD. Canakci, Ozsezen and Turkcan [26] and An, Yang, Maghbouli, Li, Chou and Chua [20] reported that BSFC and the thermal efficiency increased compared with PD. When biodiesel fuel was used, the exhaust gas temperature was found to be lower than that from PD [24]. Similarly, Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] found that microalgae (Chaetoceros gracilis) biodiesel gave lower exhaust gas temperatures than PD. The CO level in exhaust gases is an indicator of incomplete combustion. Biodiesel fuels produce lower CO and CO2 than PD € € [20,24]. In a study by Ozener, Yüksek, Ergenç and Ozkan [21],

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biodiesel from soybean emitted significantly lower CO emissions of about 28e46% with a slight increase of 1.46e5.03% in CO2 emissions compared with PD. Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] reported that in comparison with PD, microalgae (Chaetoceros gracilis) biodiesel produced about 17.4% lower CO and about 2.6% higher CO2 during no-load testing at 3500 rpm. Varatharajan and Cheralathan [27] reported that the biodiesel market could be limited by the higher NOx emission. The NOx formation percentage in the exhaust gas emissions produced by biodiesel fuel compared to PD is still unclear [28]. Some studies have reported an increase in NOx with biodiesel fuel whereas others have € reported a reduction. Ozsezen and Canakci [18] and Ozener and Yüksek [21] reported higher NOx with biodiesel than PD. An, Yang, Maghbouli, Li, Chou and Chua [20] reported that the NOx emission from waste cooking biodiesel was lower than that of PD at most engine conditions because it is very sensitive to the exhaust gas temperature. Similarly, Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] found a reduction of about 14% in NOx with microalgae (Chaetoceros gracilis) biodiesel compared to PD. In the light of the literature review, it appears that the engine performance and emission from biodiesel are depending on biodiesel's physical and chemical properties, the engine type and the operating conditions. Biodiesel from different feedstock have been widely studied in diesel engines. However, engine performance and emissions using microalgae still have not been fully understood [16,29,30]. The current work aims to study the biodiesel from MCP in different blend ratios with PD as a promising future fuel. The study includes characterising chemical and physical properties, spray pattern, engine performance and exhaust gas emission at different engine speeds with maximum load conditions. This study also aims to apply statistical analyses using analysis of variance (ANOVA) for the engine performance and emissions. 2. Methodology and experimental apparatus 2.1. Engine test setup A 4-stroke, single-cylinder air-cooled diesel engine Yanmar L48N6 was used to evaluate the fuel performance. The engine capacity is 0.219 L with continuous rating output power of 3.09 kW @ 3600 rpm. The Injection timing is 16.5 BTDC. A Land and Sea waterbrake dynamometer was used to load the engine and measure the brake torque, engine speed and break power. A Kistler 6125C piezoelectric pressure sensor was installed in the engine cylinder head to measure the in-cylinder pressure and connected via a Kistler SCP slim 2852A11 charge amplifier to a National Instruments data acquisition board. A wideband lambda sensor, incremental rotary encoder, air and fuel flow meters, exhaust gas temperature and were also installed. A Coda gas analyser that detects n-Hexane or propane, CO, CO2, O2 and NOx was used to measure the exhaust gas emissions. 2.2. Fuel preparation and properties Microalgae Chlorella protothecoides is considered a robust species and can grow in various conditions such as photoautotrophic and heterotrophic [31]. Growing MCP is reported to be used for both CO2 fixation method and oil production. MCP oil (100%) was used in this project due to its availability in a commercial scale and its suitability as biodiesel fuel. The microalgae oil was converted to biodiesel (MCP-B100) through transesterification process using methanol and NaOH (Sodium hydroxide) as a catalyst. Petroleum diesel (PD) and MCP-B100 were used to prepare the blends of MCP-

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B50 and MCP-B20 by volumes. The chemical profile for the MCPB100 (fatty acids methyl ester) is presented in Table 1. The FAME profile of MCP-B100 was measured using A Shimadzu GCMSQP2010 Plus gas chromatograph-mass spectrometer. The results of the measured FAMEs, presented in Table 1, showed a good agreement with the FAMEs profile provided by the supplier. The physical properties of PD and MCP-B100 were also obtained from the suppliers. The viscosity of PD, MCP-B100, MCP-B50 and MCP-B20 was measured using a Brookfield Viscometer DV-IIþPro Extra (Middleboro, MA, USA). The viscometer was connected to a Brookfield temperature controller. The suitable spindle and its rotational speed were selected to obtain a torque percentage within the working range of the device at each temperature [32]. The device gives the viscosity based on the spindle rotational speed and its contact area with fuel by measuring the fuels resistance to the rotating spindle. Table 2 depicts the physical properties of PD, MCPB100, MCP-B50 and MCP-B20. 2.3. Fuel spray pattern tester

Table 2 Fuel properties. Fuel property

PD

MCP-B100

MCP-B50

MCP-B20

Density at 15
C (kg/L)a Cetane number Energy content (MJ/kg)a Lower hating value (MJ/kg) Viscosity at 40
C (cp)a Flash point (
C) Oxidation stability, 110
C hours Sulfuret content (mg/kg)

0.86 51.0 46.20 43.25 2.53 66.0 5.0 8.0

0.90 52.0 40.04 37.50 4.22 124.0 12.0 2.0

0.88 51.5 43.12 40.38 3.20 95.0 8.5 5.0

0.87 51.2 44.97 42.10 2.80 77.6 6.4 6.8

PD properties obtained from British Petroleum. MCP-B100 obtained from Soley Institutes. a Measured.

The engine set-up in Fig. 1, was carefully calibrated and tested using diesel fuel. Each test was repeated three times for each fuel. The engine was run for 10 min with PD at the start of each test to warm up the engine at partial load. 2.5. Statistical analysis

High viscosity of fuel can affect the spray angle, injection process and then the combustion process. An injector tester was constructed to study the effect of fuel viscosity on the fuel injection spray pattern (Fig. 2). The same fuel system was used to construct the injector spray pattern tester to compare MCP-B100 and it blends with PD using a photron high speed camera. A perspex box with a black background was designed and the fuel injector was inserted on it at a certain angle. The camera was located and focused on one orifice perpendicularly. To avoid any effect of different injection pressure on the spray pattern, the fuel injection pressure was measured using the same pressure transducer and data acquisition system described in Section 2.1. The camera was set on 1000 frame per second to record the spray pattern of PD and MCP-B100 at similar injection pressures.

3. Results and discussion

2.4. Test procedure

3.1. Fuel properties

The test was performed at five engine speeds of 3800, 3670, 2900, 2350 and 1770 rpm. At these speeds, the engine speed (rpm) was very stable with a variety of fuels. The variation or the uncertainty level in the engine speed was ±5e7 rpm (maximum engine speed error was 0.39%). The engine test was conducted at the maximum fuel line with a wide open throttle (WOT). At the WOT, the engine speed was 3800 rpm with no load. The load was applied until the engine speed dropped to 3670, 2900, 2350 and 1770 rpm. The engine was maintained at each speed for 10 min to record and save the readings in two computers.

Fuel physical and chemical properties are very important and need to be assessed. MCP-B100 has been reported to have suitable biodiesel properties and a lower cold point of 13
C which make it suitable for cold weather conditions [15]. Viscosity plays an important role in the atomisation process of the fuel [33,34]. The relationship between the fuels viscosity and temperature is presented in Fig. 3. The viscosity curve trends for all the fuels are found comparable against the temperature. The viscosity is reduced when the temperature of the fuels are increased. MCP-B100 presented the highest viscosity values at the studied temperatures starting from

The data of the engine performance and exhaust gas emissions were analysed using IBM SPSS Statistics 19 software. Two-way ANOVA was performed to study the significance of the effect of the independent variables of fuel type (four levels) and the engine speed (five levels) on the dependent variables of the engine performance and exhaust gas emission parameters at significance level of p  0.05. An LSD post hoc test was performed to study the differences between the independent variables. The independent variables are brake power, torque, BSFC, thermal efficiency, exhaust gas temperature, CO, CO2, O2 and NOx.

Table 1 Chemical profile MCP-B100. Formula

FAME name

Relative content (%) From the supplier

N/A C15H30O2 C17H34O2 C18H36O2 C19H34O2 C19H36O2 C19H38O2 C20H38O2 C21H40O2 C21H42O2 N/A N/A N/A

Methyl tetradecanoate Hexadecanoic acid methyl ester Heptadecanoic acid methyl ester 9,12-Octadecadienoic acid methyl ester 9-Octadecenoic acid methyl ester Octadecanoic acid methyl ester 10-Nonadecenoic acid methyl ester 11-Eicosenioc acid methyl ester Eicosanoic acid methyl esteracid ester

1.3 12.80 0.9 17.40 60.80 2.8 0.3 0.4 0.4

Measured 3.10 e 13.64 4.45 70.48 0.0 e e 0.0 2.14 2.23 3.96

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Fig. 1. Engine set-up. 1 Engine. 2 Dynamometer. 3 Encoder. 4 Load valve. 5 Exhaust gas temperature. 6 Airflow meter. 7 Pressure transducer. 8 Wideband lambda sensor.

Fig. 2. Nozzle pattern tester. 1 nozzle in the Perspex box. 2 fuel pump. 3 high speed camera. 4 laptop. 5 pressure transducer. 6 data acquisition system.

Fig. 3. The relationship between the viscosity in (cP) and temperature (
C) for PD, MCP-B20, MCP-B50 and MCP-B100.

10.1 cP at 5
C and ending with 2.48 cP at 70
C. It can also be observed from the figure that increasing the proportion of MCP-

B100 in the blend, increase the viscosity. The percentage of the differences in the physical properties of MCP-B100 and its blends compared to those of PD are demonstrated in Fig. 4. The higher viscosity of the MCP-B100 (66.8%) compared with diesel is within the acceptable limit of biodiesel based on the ASTM standers. Fuel viscosity is directly proportionate to biodiesel chain length and degree of saturation. Fuel viscosity can be reduced by reducing the oxidation process and preventing the FAMEs to form free FAs. Higher viscosity affects the droplet size of the fuel, produces poor atomisation and changes the fuel penetration [35]. The viscosity of MCP-B100 has not negatively affected the engine performance due to the reduction in internal leakage within the fuel pump [23]. In addition, good nozzle spray pattern was obtained, with a wider spray angle of about 3
recorded for MCP-B100 compared to that of PD as presented in Fig. 5. Another positive factor demonstrated in Fig. 4 is the 2% higher cetane number of MCP-B100 compared to PD, which indicates better combustion quality with biodiesel compared to PD because of the chemical structure. Among all the fuel properties, the lower heating value and the cetane number appear to be the main affective factors in the engine performance and emissions. The CN in MCP-B100 is 52 which is slightly higher than 51 of PD. This is due to the FAMEs especially methyl oleate (9-octadecenoic acid methyl ester) C19H36O2 which relatively long chain that increase the CN. Improving one biodiesel property by using additives or modifying the fatty acid composition usually increases the problematic behaviour of another property. Knothe [36] reported that cetane numbers increase with increasing chain lengths and saturation level. On the other hand, increasing CN led to poor Cold flow. While Unsaturated FAs possess low cetane numbers and low oxidative stability, which is undesirable for a diesel fuel. The heat of combustion is the main factor responsible of higher BSFC with biodiesel compared to PD. The heating values per unit mass for MCP-B100, MCP-B50 and MCP-B20 were lower than those of the PD by 13.3%, 6.7% and 2.7%, respectively as shown in Fig. 4. The density of MCP-B100 was 4.5% higher than that of PD. If the same volume of fuel was injected into the combustion chamber, the higher density would offset the negative impact of the lower

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Fig. 4. The variation percentage in the fuels' physical properties compared with PD.

Fig. 5. Nozzle test (a) PD (b) MCP-B100.

heating value of MCP-B100 and its blends which is given in mass units. The chain length and the level of unsaturation of the FAMEs directly affect the heat of combustion, for example long chain unsaturated compounds give the highest heat of combustion [36]. Oxidative stability of biodiesel is a complex process and a major technical issue facing biodiesel. The nature of the fatty acid chains, chain length and the level of unsaturation found in biodiesel influence its oxidative stability. Biodiesel in general, have an oxidative stability lower than PD which form acidity [37]. MCP-B100 oxidative stability of 12 h is higher than 3 and 6 h as minimum oxidative stability of biodiesel fuel based on the ASTM D6751 and ENG 14214 respectively [36]. The high value of the oxidative stability indicate longer-term biodiesel storage [38]. The oxidative stability can be reduced with using saturated FAMEs. However, it is recommended to be maintained high because reducing it will lead to producing free fatty acids that increase the viscosity and produces insoluble gums and sediments that plug the fuel filters [38,39]. Unsaturated FAME components significantly decrease the oxidative stability of the fuel [36].

3.2. Combustion characteristics Fig. 6 presents the relationship between the in-cylinder

pressure in bar and the crank angle at the engine speeds of 3670, 2900 and 2350 in degrees. The figure shows that increasing the load on the engine increased the maximum in-cylinder pressure to about 70 bar at 2900 and 2350 rpm. The in-cylinder pressure results in Fig. 6 indicate that there was an inverse relationship between the in-cylinder pressure and the percentage of MCP-B100 in the fuel. The maximum in-cylinder pressure was recorded with PD while the lowest values were recoded with MCP-B100 at the engine speeds of 3670, 2900 and 2350 rpm. This is consistent with the findings of An, Yang, Maghbouli, Li, Chou and Chua [20]. At the engine speed of 3670 rpm, the maximum drop in the in-cylinder pressure of 5.8% was found between the PD and MCP-B100. This finding is very close to the reduction in the in-cylinder pressure reported by An, Yang, Maghbouli, Li, Chou and Chua [20] who found a 5.8% reduction with biodiesel fuel compared to PD at 50% load. At the engine speeds of 2900 and 2350 rpm, the in-cylinder pressure showed very comparable results. The maximum drops in the incylinder pressure of 1.05%, 5.81% and 9.04% compared with PD were found at 2900 rpm with MCP-B20, MCP-B50 and MCP-B100, respectively due to the lower heating value. The reduction in the heating value of MCP-B100, as shown in Fig. 4 was 13.3%, which was higher than the reduction in the in-cylinder pressure due to the higher cetane number and the extra O2 in the MCP-B100 and its

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Fig. 6. In-cylinder pressure at engine speeds 3670, 2900 and 2350 rpm.

blends. The peak in-cylinder pressure occurred at ATDC for all the fuels, which agrees with Gumus [19] and Ozsezen, Canakci and Sayin [17] who found that the peak pressure occurred at 2.9e5.89
crank angle. 3.3. Engine performance and exhaust gas emission The summary of the ANOVA that presents the engine performance and exhaust gas emission parameters is given in Table 3. The results of the descriptive statistics and the LSD test are presented in Table 4. The percentage difference of the fuels as averaged results obtained from all the tested engine speeds is given in Fig. 7. The curves for the behaviour of each studied parameter for the different studied fuels at different engine speeds are presented and discussed separately in detail in the following subsections. 3.3.1. Brake power and torque As shown in Table 3, the engine brake power and torque were significantly affected by the type of fuel at the averaged engine speed. Similarly, the engine speed was found to have a highly significant effect on the engine brake power and torque regardless of the fuel type, whereas the interaction between the type of fuel and the engine speed was statistically insignificant. This means the trends of the brake power and torque were statistically the same when the fuel and the speed changed. Table 4 presents the post hoc LSD test showing the differences between the total brake power results produced when the engine was run with MCP-B100, MCPB50, MCP-B20 and PD. It can be observed from Table 4 that MCPB100 produced significantly less averaged brake power and torque than PD, whereas MCP-B20 produced averaged engine brake power and torque statistically the same as PD due to the lower percentage of microalgae in the fuel blend. MCP-B50 produced an average brake power and torque statistically similar to all fuels because it consist of 50% PD and 50% MCP-B100. Table 4 also shows that the average engine brake power and torque were reduced when the biodiesel percentage in the fuel increased. This is in a

good agreement with [20,22] due to the lower heating value of MCP-B100. The behaviour of the engine brake power and torque at different engine speeds using PD, MCP-B20, MCP-B50 and MCP-B100 is plotted in Fig. 8. The maximum brake power values at 3670 rpm for PD and MCP-B20 were insignificantly different from the brake power values found at 2900 rpm for the same fuels. The variation between fuels was clear at the engine speed of 3670 rpm for the brake power and torque. The maximum brake power values were found to be in the following order: PD (3.71 kW), MCP-B20 (3.51 kW), MCP-B50 (3.39 kW) and MCP-B100 (3.14 kW), with a reduction percentage of 5.39%, 8.63% and 15.36% for MCP-B20, MCP-B50 and MCP-B100, respectively compared to PD. The reason for the reduction was the lower heating value of the biodiesel fuel [17]. As shown in Fig. 4, the lower heating value of MCP-B20, MCPB50 and MCP-B100 was reduced by 2.7%, 6.7% and 13.3%, respectively. The reduction in the averaged brake power, as presented in Fig. 7 was only by 1.2%, 3.5% and 7.0%, respectively. The reduction was considerably less than expected because of the negative effect of the lower heating value of the biodiesel fuel. Various parameters such as the higher density and cetane number of the MCP-B100 and its blends compared to PD, reduces the negative impact of the lower heating value. The higher viscosity can contribute to reducing the fuel leakage in the fuel pump, which enhances engine power [23]. The brake power and torque were reduced by 7% and 4.9% when the engine was fuelled with MCP-B100 compared to PD, and the heating value was lower by 13.3%, which is in a good agreement with the findings of Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] who reported 6.3% less power € with microalgae biodiesel than PD. Ozener, Yüksek, Ergenç and € Ozkan [21] stated that the reduction in power was lower than the reduction in the heating value due to the extra fuel injected and the higher density. The power result is in agreement with Chokri, Ridha, Rachid and Jamel [22], who reported a reduction in the engine torque of about 5% with biodiesel from a waste vegetable oil

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Table 3 Summary of two-way ANOVA of the effect on the type of fuel, engine speed and the interaction between them on the engine performance and emission parameters. Source

Dependent variable

Degrees of freedom

Mean square

F

Sig.*

Fuel

Power Torque Efficiency BSFC EG Temp. CO CO2 O2 NOx Power Torque Efficiency BSFC EG Temp. CO CO2 O2 NOx Power Torque Efficiency BSFC EG Temp. CO CO2 O2 NOx

3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0

0.11 0.71 5.69 4783.1 2517.9 1.34 0.32 4.40 3200 17.61 228.77 920652.18 232661.7 212737.1 49.77 80.02 305.02 432460.5 0.06 0.37 4.03 1406.6 705.5 0.37 0.19 0.52 1413.2

3.86 2.75 1.66 6.74 2.74 8.08 1.49 9.45 3.11 643.67 883.56 259.97 327.61 231.72 300.13 369.23 654.32 420.08 1.30 1.43 1.18 1.98 0.77 2.25 0.89 1.11 1.373

0.02 0.05 0.19 0.00 0.05 0.00 0.23 0.00 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.19 0.33 0.05 0.68 0.03 0.56 0.37 0.214

Engine speed

Fuel  Engine speed

*Mean difference is significant if p  0.05.

Table 4 Descriptive statistics and LSD post hoc test summary for the engine performance at the averaged results obtained from the tested engine speeds. Performance variable

Brake power (kW) Torque (N$m) BSFC (g/kW$h) Efficiency (%)
EG Temp. ( C) CO (%) CO2 (%) O2 (%) NOx (ppm)

PD

MCP-B20

MCP-B50

MCP-B100

M

SD

M

SD

M

SD

M

SD

2.58a 9.04a 365.1a 24.50 450.6a 2.36a 7.56 7.73a 396.7a

1.11 4.01 108 6.35 119 2.00 2.33 4.68 185

2.55ab 9.06a 378.0ab 24.97 445.0ab 2.07b 7.51 8.05ab 387.0b

1.14 3.96 125 6.89 121 1.96 2.34 4.64 175

2.49ab 8.93ab 394.6bc 25.22 448.6a 1.95bc 7.50 8.26b 371.5b

1.11 4.00 144.2 7.01 125.1 1.76 2.40 4.55 179.6

2.40b 8.60b 402.3c 25.89 423.2b 1.70c 7.24 8.95c 367.4b

1.02 3.78 131 6.91 125 1.75 2.34 4.37 160

Means in the same row that do not share the same letter are significantly different at p < 0.05.

Fig. 7. The averaged engine performance and exhaust gas emissions percentage differences compared with PD when MCP-B100, MCP-B50 and MCP-B20 were used.

biodiesel blend, and is consistent with Haik, Selim and Abdulrehman [13]. The positive effect of O2 in the biodiesel structure is another factor that reduced the negative effect of the lower heating value. The O2 content in the biodiesel chemical composition was more effective at the full load condition (at rich combustion).

Consequently, the results of the brake power were comparable at low engine speeds (high load) for all the fuels. Another possible reason is the higher cetane number which indicates better ignition quality.

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Fig. 8. The relationship between engine speed (rpm) and engine BP (kW) for PD, MCP-B20, MCP-B50 and MCP-B100.

3.3.2. Brake specific fuel consumption (BSFC) and thermal efficiency Table 3 shows that the average BSFC and thermal efficiency recorded when the engine was fuelled with PD, MCP-B20, MCP-B50 and MCP-B100 were statistically different, whereas, the type of fuels insignificantly affected the average thermal efficiency. The
mez and Lo
pez [3], result agrees with Dorado, Ballesteros, Arnal, Go €
mez and Lo
pez [25] and Usta, Oztürk, Dorado, Ballesteros, Arnal, Go Can, Conkur, Nas, Con, Can and Topcu [23] who stated that the difference in the thermal efficiency of PD and B17.5 was insignificantly higher because of the lower heating value. Table 4 indicates that the average BSFC and the thermal efficiency were directly proportionate to the MCP-B100percentage in the fuel. It is clear from Table 4 that the PD presented the lowest value of average BSFC (365 g/kW.h), which was statistically the same as the average BSFC from MCP-B20, whereas the MCP-B100 gave the highest value of 401 g/kW.h, which was also insignificant compared to MCP-B50. MCP-B100 gave the highest thermal efficiency compared to PD and other blends due to the chemical and physical properties of MCP-B100 such as the higher cetane number, density and O2 content in the biodiesel structure. Fig. 7 presents the differences in the average BSFC and thermal efficiency using MCP-B100 compared to PD are 10.2% and 5.7, respectively. The differences resulted from the fuels' chemical and physical properties such as lower heating value, which means the engine was required to burn extra biodiesel fuel to reach the same brake power produced using PD [10,17,21,23,40]. The increase in BSFC with biodiesel from soybean ranged from 2% to 9% in a study € € conducted by Ozener, Yüksek, Ergenç and Ozkan [21] and was less than 8.5% with biodiesel from waste cooking olive oil compared to
mez and Lo
pez [25]. PD in a study by Dorado, Ballesteros, Arnal, Go The BSFC at each engine speed using different fuels is presented

in Fig. 9. For the engine under load condition of maximum BSFC occurred at the lowest speed of 1770 rpm for MCP-B100. Similarly, Ozsezen, Canakci and Sayin [17] reported that B100 gave a higher BSFC at the lowest engine speed of 1000 rpm. At the engine speed of 3670 rpm when the maximum power was achieved, the lowest BSFC was recorded for all the fuels. At the same speed, the variations between PD and MCP-B100 blends were 4.5%, 7.4% and 18.0% for MCP-B20, MCP-B50 and MCP-100 respectively. The BSFC € increased as the load increased (lower engine speed). Usta, Oztürk, Can, Conkur, Nas, Con, Can and Topcu [23] reported similar findings. The BSFC from microalgae biodiesel was found to be higher than PD [10]. Fig. 9 displays that at engine speeds of 2900 rpm and below, the thermal efficiency of MCP-B100 and its blends was higher than the thermal efficiency of PD due to the oxygen content and higher cetane number. The maximum difference of 18.6% between MCPB100 and PD was evident at the engine speed of 2900 rpm. 3.3.3. Exhaust gas temperature Table 3 indicates that the effect of the fuel type and the effect of the engine speed on the exhaust gas temperature were statistically significant. Conversely, the interaction between the fuel type and the engine speed was statistically insignificant. Table 4 indicates that the exhaust temperature generated from MCP-B100 was significantly lower than PD and MCP-B50 and insignificantly less than MCP-B20 because of the lower heating value of MCP-B100. According to Fig. 7 the exhaust gas temperature of MCP-B100 was 6.1% lower than that of PD. The exhaust gas temperature of PD, MCP-B20, MCP-B50 and MCP-B100 at different engine speed is shown in Fig. 10. The exhaust gas temperature curves for all fuels increased with an increase in the engine speed reaching their respective peaks at engine speeds

Fig. 9. The relationship between engine speed (rpm) and BSFC (g/kW.h) and the engine thermal efficiency (%) for PD, MCP-B20, MCP-B50 and MCP-B100.

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Fig. 10. The relationship between engine speed (rpm) and exhaust gas temperature (
C) for PD, MCP-B20, MCP-B50 and MCP-B100.

between 2350 and 2900 rpm and then reducing gradually until reaching 3670 rpm. Beyond this speed, the exhaust gas temperatures dramatically dropped because of the no load applied on the engine at this speed. At the engine speed of 3670 rpm, the maximum reduction of about 61
C (12.4%) of the exhaust gas temperature for MCP-B100 below that for PD occurred. The reduction is very close to what was expected due to the lower heating value of the MCP-B100, which dropped by 13.3%. At the speed of 3670 rpm, the differences in the thermal efficiency between PD and MCP-B100 were comparable, which indicates that the reduction in the exhaust gas temperature was caused by the lower heating value. Overall, the averaged exhaust gas temperature declined by only about 6.1%. This is due to the enhanced combustion owing to the higher thermal efficiency with MCP-B100 because of the same factors explained previously. It can be concluded that the exhaust temperature was strongly related to the lower heating value of the fuels and the thermal efficiency. The increase in thermal efficiency with MCP-B100 and its blends decreased the reduction in the exhaust gas temperature because of the lower heating value. 3.3.4. Carbon monoxide (CO) and carbon dioxide (CO2) The ANOVA results in Table 3 demonstrate that the average CO level emitted using the studied fuels was very significant at the average results of the tested engine speed, whereas the CO2 was insignificantly affected by the type of the fuel. The engine speed also affected the average CO and CO2 emission very significantly. In
mez and Lo
pez a study performed by Dorado, Ballesteros, Arnal, Go [25], a statistical test using the unpaired t-test showed that CO emissions from olive oil biodiesel and PD were statistically significant. There was a significant interaction between the type of the fuel and the engine speed on the CO percentage. From Table 4 and Fig. 7, it can be observed that increasing the proportion of MCPB100 in the fuel decreased CO and CO2 emission. They also showed that MCP-B100 produced the lowest average value of CO (1.7%) and CO2 (7.24%) with a reduced percentage in comparison to PD by 28% and 4.2%, respectively. This agrees with the findings of An, Yang, Maghbouli, Li, Chou and Chua [20], Lin and Lin [24] and € € Ozener, Yüksek, Ergenç and Ozkan [21] that soybean biodiesel B100 produced 46% lower CO than PD due to the high O2 content in the biodiesel leading to more efficient combustion. The results of CO and CO2 emission at different engine speed for PD, MCP-B20, MCP-B50 and MCP-B100 are presented in Fig. 11. The figure indicates that the CO and CO2 percentage curves for all the fuels were relatively steady for engine speeds below 2320 rpm and

then the CO emission declined with increasing the engine speed, while the CO2 increased reaching the maximum at 2900 rpm and then dropped. The maximum CO variation of 69.4% between the fuels is found at 2900 rpm between PD and MCP-B100. The reason is at 2900 rpm, the maximum increase in the thermal efficiency with MCP-B100 was recorded and the engine was running lean associated with relatively lower BSFC. This indicates better combustion with biodiesel because of the extra O2 in the biodiesel and the higher cetane number, which is higher in MCP-B100 by 2%, as shown in Fig. 4. The reduction in the CO level at high engine speeds can be linked to the higher lambda values and O2 availability which increased the airefuel ratio thus helped convert the CO to CO2 [21]. The reduction in the CO level is due to the chemical profile of the MCP-B100 which contain high percentages of methyl oleate (9octadecenoic acid methyl ester) and methyl palmitate (hexadecanoic acid methyl ester). Knothe [36] Reported a reduction in CO level with methyl oleate and methyl palmitate by 49.0% and 43.1% respectively compared to PD. The long chain of methyl oleate C19H36O2 is responsible of reducing CO emissions due to the reverse relationship between the chain length and CO emission [36]. Fig. 11 presents the maximum variation of 15.89% in CO2 level between PD and MCP-B100 at engine speed of 3700 rpm. It can also be observed that at engine speeds below 2350 rpm, when the load increased MCP-B100 and its blends produced insignificantly higher CO2 compared to PD. It is due to the high load that makes the airefuel ratio close to the stoichiometric or even a richer mixture. The availability of the O2 in MCP-B100 and its blends is associated with the increase in the time for reaction (due to the low engine speed) slightly enhancing the combustion and allowing more CO to be converted to CO2. A similar finding and justification were proposed € € by Ozener, Yüksek, Ergenç and Ozkan [21]. 3.3.5. Oxygen (O2) The results of the O2% from all the fuels at the average of the overall tests were statistically the same due to the high variation between the different runs using the same fuel. This is clear by the high standard deviations presented in Tables 3 and 4. Nevertheless, Table 4 demonstrates a direct relationship between the MCP-B100% in the fuels and the O2 level in the exhaust because of the extra O2 in the MCP-B100 chemical structure which contributed to increasing O2 level in the exhaust. Fig. 7 displays an increase in O2 levels in the exhaust gas emissions by 4.1%, 6.9% and 15.8% when MCP-B20, MCP-B50 and MCP-B100 were used, respectively, compared to PD. This is in a strong agreement with the findings of
mez and Lo
pez [25] that indicated Dorado, Ballesteros, Arnal, Go that biodiesel fuel from olive oil produced 17.6% higher O2 than PD. Fig. 12 shows the O2 level in the exhaust gas emissions versus the engine speed using PD, MCP-B20, MCP-B50 and MCP-B100 fuels. It is clear that increasing the engine speed (by reducing the load on the engine) raised the O2 level in the exhaust. Increasing the load on the engine required extra O2 to reach a complete combustion. 3.3.6. Nitrogen oxides (NOx) The ANOVA results in Table 3 indicate that the NOx emission is statistically varied when the fuel was changed. This finding is consistent with an unpaired t-test performed by Dorado, Balles
mez and Lo
pez [25] that shows the difference in NO teros, Arnal, Go emission from olive oil biodiesel and PD was very significant. The NOx results were also significantly different between the tested speeds. The interaction between the fuel type and the engine speed as shown in Table 3 was insignificant. Table 4 presents a comparison of the means of the fuels tested and depicts that the NOx level increased with increasing the percentage of MCP-B100 in the fuel. The table indicates that MCP-B20, MCP-B50 and MCP-B100

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699

Fig. 11. The relationship between engine speed (rpm) and CO (%) and CO2 (%) for PD, MCP-B20, MCP-B50 and MCP-B100.

Fig. 12. The relationship between engine speed (rpm) and O2 (%) for PD, MCP-B20, MCP-B50 and MCP-B100.

statistically produced similar results with all producing statistically lower NOx than PD. In the overall test, PD emitted an average NOx of 396.7 ppm, which was about 7.4% higher than MCP-B100 owing to the higher cetane number for the biodiesel that decreased the NOx emission [41]. The reduction was also caused by the lower exhaust temperature [20] that was recorded with MCP-B100 and its blends as previously mentioned. Fig. 13 presents the results of NOx emission produced from PD, MCP-B20, MCP-B50 and MCP-B100 verses engine speed. The figure

Fig. 13. The relationship between engine speed (rpm) and NOx (ppm) for PD, MCP-B20, MCP-B50 and MCP-B100.

shows that the curves trend of all fuels were relatively similar. The maximum results of the NOx were observed with the speeds of 2900 and 3670 rpm. At the maximum output power (3670 rpm), the maximum difference between PD and MCP-B100 was recorded to be about 16.4. This reduction and the reduction in the averaged NOx emission of 7.4% are lower than the reduction reported by Wahlen, Morgan, McCurdy, Willis, Morgan, Dye, Bugbee, Wood and Seefeldt [10] who found that the NOx emission with biodiesel from microalgae (Chaetoceros gracilis) was reduced by 24% compared to PD under no load condition. The reduction is also lower than that reported by Chokri, Ridha, Rachid and Jamel [22] who found that for every 10% increase in the biodiesel percentage in the fuel, a reduction of 2% in the NOx was found. The main factors affecting the NOx were the exhaust gas temperature, the O2 content, CN and biodiesel chemical structure. Given that the average reduction in the exhaust gas temperature with MCP-B100 was 6.1% compared to PD, the reduction of the averaged NOx by 7.4% was expected. The chemical structure of the MCP-B100 of containing Hexadecanoic acid methyl ester and 9-Octadecenoic acid methyl ester are responsible of increasing the CN and then the NOx. The NOx emissions can be relatively reduced by increasing CN through increasing saturation of the fatty ester chain and chain length [36].

3.3.7. Particulate matter (PM) Combustion process is the main source of PM emission from diesel fuel. The PM can be predicted from the chemical structure of the MCP-B100 and references. Table 1 showed that the major FAMEs of MCP-B100, more than 84% from the (measured profile), are methyl oleate (9-octadecenoic acid methyl ester) and methyl palmitate (hexadecanoic acid methyl ester). Methyl oleate and methyl palmitate produce less PM than PD by about 72.9 and 81.9 respectively [36]. The reduction of 72.7 in PM was achieved when methyl oleate technical grade 77% was used. Similarly, MCP-B100 consist of 70.48% of the same ester. This can be strong evidence to predict a reduction in PM when MCP-B100 and its blends are used as alternative fuel. The hexadecanoic acid which is 12.8% of MCP-B100 would be prime components of PD, therefore, the rest of fatty acids in MCP-B100 are proposed to reduce the PM [36]. Rahman [42] reported that PM can increase by increasing the biodiesel carbon chain length, while higher degree of unsaturation increases the PM to certain levels which slightly reduces the PM. The O2 content in the fuel reduce the PM emissions. Therefore the MCP100 is proposed to produce less PM than PD. Satputaley, Zodpe and Deshpande [16] found that MCP produce less smoke opacity than PD. Hence, further study on PM and PN from MCP-B100 and its blends at various operating conditions is required.

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4. Conclusions This paper presented the process of preparing and characterising the physical properties of MCP-B100 and its blends with PD. The fuels' density, viscosity, heating value and spray pattern were measured. The engine performance and the exhaust gas emission were evaluated using PD, MCP-B20, MCP-B50 and MCP-B100 under different operating conditions. The results can be summarised as follows:

[10]

[11]

[12]

1. MCP-B100 and its blends are potential alternatives and its fuel properties are comparable with PD. MCP-B100 and its blends with PD can be used in diesel engines with minimal engine modification. 2. The heating value of MCP-B100 was found to be lower than the heating value of PD by 13.3%. However, the overall reduction in the engine torque and power with MCP-B100 was only 4.9% and 7.0%, respectively. This result indicates better combustion with MCP-B100 and its blends. MCP-B100 viscosity which is higher than that of PD by 66.8%, had a positive effect on the engine's performance characteristics due to its higher cetane number (2% higher than that of PD). The density of MCP-B100 (higher than that of PD by 4.5%) was another factor that compensated the reduction in engine performance as a result of the lower heating value. Chemical properties such as the extra O2 in MCP-B100 contributed to the relative increase in engine efficiency compared to PD. 3. The statistical analyses showed that the effect of the fuel type was statistically significant at p  0.05 with brake power, torque, BSFC, exhaust gas temperature, CO, O2 and NOx. However, other parameters were insignificantly affected by the type of fuel used in the test. 4. MCP-B100 showed a reduction of 7.0%, 4.9%, 6.1%, 28%, 4.2% and 7.4% of the parameters of brake power, torque, exhaust gas temperature, CO, CO2 and NOx, respectively. 5. MCP-B100 showed an increase by 10.2%, 5.7%, and 15.8% of the parameters of BSFC, thermal efficiency and O2, respectively.

[13] [14] [15]

[16]

[17]

[18]

[19]

[20]

[21]

[22]

[23]

[24]

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