An experimental investigation of performance, combustion - NOPR

Indian Journal of Engineering & Materials Sciences Vol. 20, February 2013 pp. 42-50

An experimental investigation of performance, combustion and emission characteristics of mahua (Madhuca Indica) oil methyl ester on four-stroke direct injection diesel engine C Solaimuthua*, D Senthilkumarb & K K Ramasamya a

Department of Mechanical Engineering, Paavai Engineering College, Namakkal 637 018, India b Department of Mechanical Engineering, Sona College of Technology, Salem 636 005, India Received 3 August 2011; accepted 3 December 2012

This paper is mainly concerned with an experimental investigation to study the diesel engine performance, combustion and emission characteristics using mahua (Madhuca Indica) biodiesel (mahua oil methyl ester) and its blend in different volumetric proportions with diesel. To start with, the thermo-physical properties of all the fuel blends are evaluated. A four stroke tangentially vertical (TV) single cylinder direct injection (DI) diesel engine with eddy current dynamometer is used for the study under various load conditions. Combustion and emission characteristics for different blends are evaluated in running the engine under steady state conditions. Neat diesel is called B0 and neat (mahua oil methyl ester) biodiesel is called B100. From the experiments, it is seen that B25 gives almost the same brake thermal efficiency as B0 at full load condition, compared to other blends. The blend B0 and B25 give the lowest specific fuel consumption of 0.56 and 0.27 kg/kW.h at no load and full load as compared to all other blends. At no load B100 gives the lowest NOx emission which is 2.52% less compared to B0. Keywords: Neat diesel, Mahua oil, Mahua oil methyl ester, Neat biodiesel, Engine performance, Combustion, Emissions

The performance in fuel economy of internal combustion engines should not be considered in isolation, but also in the context of availability and long range use. Alternative fuels can be popular in countries that have very low indigenous crude oil supply compared to its demand. Further there must be enough surplus source of an alternative fuel and that too must be of renewable source. These circumstances can help justify the higher cost of an alternative fuel. More recently alternative fuels have become important because of the so-called, ‘zero point’. This is when the carbon dioxide emissions from a biomass fuel are balanced by the carbon dioxide that the crop would absorb during its growth. The literature on alternative fuels demonstrates that a diesel engine can be made to run virtually on any liquid fuel. However as diesel engines are invariably developed to run on conventional fuels of crude oil origin, then running the engine on alternative fuels can lead to operational difficulties. The different physical properties of alternative fuels lead to a different ignition delay and combustion performance. These differences can be reduced by running a diesel engine with a mixture of __________ *Corresponding author ([email protected])

an alternative fuel with diesel. However, this does not necessarily eliminate the durability problem. Vegetable oils are normally transesterified into biodiesel which can be blended with fossil diesel. Biodiesel can be produced by a two step acid-base process from raw mahua oil using methanol as reagent and H2SO4 and KOH as catalysts for acid and base reactions respectively. Equation (1) shows the chemical route of biodiesel production from raw mahua oil9.

… (1)

In recent years, a growing interest is evinced concerning renewable and alternative fuels. These fuels are bio-degradable and oxygenated and the examples include vegetable oils, their derivatives and their mixtures with diesel. Research on vegetable oils in diesel engine is in progress at least for over 100 years. However, due to availability of fossil

SOLAIMUTHU et al.: DIESEL ENGINE PERFORMANCE USING MAHUA BIODIESEL

diesel, in the last century the research on vegetable oil based engine fuels lost importance with time. In the present time due to the price hike of petroleum diesel, the research on biodiesel has again gained importance. Biodiesel is derived from vegetable oils such as corn, sunflower, karanja, cotton seed, neem, jatropha and madhuca indica (mahua), by a process called transesterification. Out of these vegetable oils, non-edible vegetable oils are preferred for engine applications in India. This study is focused on mahua biodiesel. Mahua biodiesel and its blend in different volumetric proportions with fossil diesel are used to study the performance, combustion and emission characteristics. Clark et al.1 concluded that soybean biodiesel gives higher specific fuel consumption and lower emissions except NOx than diesel. Kyle et al.2 found that as compared to diesel fuel, soybean methyl ester gives lower emissions of CO, HC, smoke density and NOx. Narayana Reddy and Ramesh3 investigated the performance and emissions of diesel with jatropha oil biodiesel fuel. They concluded that jatropha oil biodiesel gives similar performance and emissions as diesel when its injection timing is optimized. Venkatraman and Devaradjane4 investigated the performance and emission characteristics of diesel engine with pungam oil methyl ester (PME) diesel blends. They concluded that PME 20 could be used as alternative fuel for diesel engine with compression ratio of 19:1. Raslavicius et al.5 carried out investigation on a DI diesel engine to calculate ignition delay using equations derived by rearrangements of quasi-stationary (Q-S) combustion theory for n-octane droplet. They concluded that the rape seed methyl ester (B100) displays lower values of ignition delay than diesel (B0) fuel. Saravanan et al.6 carried out investigation on a DI diesel engine fuelled with pure mahua oil methyl ester (B100) and pure diesel (B0). They concluded that the B100 gives the lower emissions compared to B0. Raheman and Ghadge7 considered mahua biodiesel blended with fossil diesel and discussed extensively the engine performance obtained by blends with different volumetric ratios. They concluded that a blend of 20% biodiesel by volume with 80% diesel was more appropriate for their engine. Puhan et al.8 reported the biodiesel preparation and discussed its performance and emission characteristics of diesel engine with B0 and B100 fuel. They made the conclusion that the mahua oil methyl ester (B100) burn more efficiently

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than diesel (B0) and the emissions of B100 are lower than that of B0. Puhan et al.9 performed engine tests with mahua biodiesel in a naturally aspirated diesel engine. They used neat diesel and neat biodiesel. Emissions were measured and they have reported that the neat biodiesel (B100) is lower than that of neat diesel (B0). Puhan et al.10 further performed engine tests with mahua oil methyl ester and mahua oil ethyl ester in a direct injection diesel engine. They concluded that mahua oil methyl ester gives better results as compared with ethyl ester of mahua oil. Sundarraj et al.11 carried out an analysis of 1, 4 dioxine-ethanol-diesel blends on diesel engines with and without thermal barrier coating. They concluded that 70% diesel, 20% ethanol and 10% dioxane blend gives better performance and lower emissions. Sundarraj et al.12 further carried out an analysis of 1, 4 dioxine-ethanol-diesel blends on diesel engines. They concluded that 60% diesel, 30% ethanol and 10% dioxane by volume gives better performance and lower emissions without any engine modification. Kapilan et al.13 compared the performances of biodiesels derived from non edible (mahua oil) and edible oil (gingili oil) and concluded that the performance and emission parameters of non edible oil methyl ester (mahua oil methyl ester) is closer to the edible oil methyl ester (gingili oil methyl ester). Kapilan and Reddy14 evaluated the performance of mahua biodiesel as an alternative to the fossil diesel. They concluded that the mahua oil methyl ester gives the lower emissions than that of diesel fuel. Kapilan et al.15 studied the effect of injection time on the performance and emission of diesel engine with mahua methyl ester. They concluded that the B100 can be used as substitute fuel for diesel with advanced injection timing for better performance and lower emissions. Sharanappa Godiganur et al.16 reported the performance and emission parameters evaluated by mahua methyl ester and its different blends on diesel engine. Among the blends, the B20 was found to give better performance. Ramesha et al.17 carried out the experiments of the diesel engine by mahua oil methyl ester and its different blends with standard engine setup of the diesel engine. They suggested that the 20% of biodiesel blended with 80% of diesel (B20) gives lower emission and better combustion among the blends. They have also studied the B20 blend, with varying injection pressures. They concluded that the higher injection pressure gives lower NOx emission. Kale et al.18 performed engine tests with

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INDIAN J. ENG. MATER. SCI., FEBRUARY 2013

mahua oil in different volumetric proportions to evaluate the performance and emission parameters. They concluded that there is an increase in thermal efficiency of the engine with preheated mahua straight vegetable oil mixed with flow improvers. Dhananjaya et al.19 tested the diesel engine with B20 and B100 jatropha biodiesel and neat diesel with various injection pressures and injection timings. From the above review, it is observed that there is considerable interest in the biodiesel applications to study the performance, combustion and emission characteristics of a diesel engine without much modification. In this paper a detailed experimental investigation of four-stroke single cylinder tangentially vertical direct injection constant speed diesel engine with injection pressure of 250 bar and injection timing of 20° bTDC with eddy current dynamometer using B0, B25, B50, B75 and B100 as fuel is presented.

standard injection timing and injection pressure are 23° bTDC and 220 bar, respectively. The injection pressure has been increased to 250 bar and the injection timing has been retarded to 20° bTDC. Lower injection timing gives better combustion2. Smoke level is measured using standard AVL 437 smoke meter. AVL 444 digital gas analyzer is used for the measurement of exhaust emissions of HC, CO, CO2, O2 and NOx. The entire experiments have been carried out under a steady state condition of the engine.

Experimental Procedure Experiments have been conducted on a four-stroke, single cylinder tangentially vertical direct injection diesel engine developing power output of 5.2 kW at 1500 rpm connected to a water cooled eddy current dynamometer. The schematic of the engine test set-up is shown in Fig. 1. Specifications of the engine are given in Table 1. The modified injection pressure of 250 bar and injection timing of 20° before Top Dead Centre (bTDC) is employed during the entire experiments for the engine under consideration. The

Table 1  Specification details of the engine Kirloskar Tangentially Vertical (TV) Vertical single cylinder, Direct injection (DI) diesel engine Bore × Stroke 87.5 mm ×110 mm Compression ratio 17.5:1 Speed 1500 rpm Rated brake power 5.2 kW Cooling system Water cooled Injection Pressure 220 bar (standard) Injection Pressure 250 bar (modified) Injection Timing 23° bTDC (standard) Injection Timing 20° bTDC (modified)

Thermo-physical properties of neat biodiesel and its diesel blends

Table 2 reports the values of neat diesel (B0) to neat biodiesel (mahua oil methyl ester-MOME) (B100). Using standard test facilities, thermo-physical properties of mahua biodiesel and its blend in various volumetric proportions with fossil diesel are evaluated. Mahua oil has lower calorific value but Make Type

Fig.1  Schematic diagram of the engine test set-up


higher density (Table 2), indicating that calorific value of mahua oil on a volumetric basis approaches the volumetric calorific value of diesel fuel. In the case of mahua oil, cetane number increases along with flash and fire point compared to neat diesel. Ratios of blends are as follows: B0 (neat diesel), B25 (25% mahua biodiesel and 75% diesel by vol), B50 (50% mahua biodiesel and 50% diesel by vol), B75 (75% mahua biodiesel and 25% diesel by vol) and B100 (neat mahua biodiesel). Specific gravity, acidity, kinematic viscosity, flash point, fire point and cloud point increases with the increase in biodiesel content. Significant increase in fire point shows that volatility of mixture with increased biodiesel content will decrease. Gross calorific value decreases as biodiesel content in mixture increases, due to oxygen in fuel and it requires more fuel to be burnt for a given heat release. Table 3 and 4 show the accuracy and uncertainty analysis of combustion and emission parameters of diesel engine. Experiments have been carried out under steady state conditions of the engine. Biodiesel production

Generally, vegetable oils contain fatty acids (palmitic, stearic, olenic, linoleic, lingnoceric, eicosenoic, arachidic and behenic). Of these mahua oil contains the saturated fatty acids palmitic (hexadecanoic acid) and stearic (octadecanoic acid) and the unsaturated acids oleic (octadec-9-enoic acid) Table 2  Properties of Mahua biodiesel and its diesel blends Properties Specific gravity Acidity

B0

B25*

B50

B75

B100

0.82

0.83

0.85

0.87

0.88

0.065

0.067

0.070

0.083

0.26

Kinematic viscosity at 40ºC, cSt

2.6

3.49

4.17

4.98

6.04

Flash point, ºC

65

71

78

112

170

Fire point, ºC

70

79

88

123

183

Cloud point, ºC

-15

4

8

11

13

Gross calorific value, kJ/kg Cetane number

45596

43976

43268

42523

41819

46

51.6

51.7

51.8

* B25 means 25% mahua biodiesel and 75% neat diesel.

52.4

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and linoleic (9,12-octadecadienoic acid). The mahua oil is commercially available in the local market and used as the raw material. The fatty acid composition of mahua oil is given in Table 5. Equation (1) shows that the details of transesterification. Transesterification process is the reaction between a triglyceride and alcohol in the presence of a catalyst to produce glycerol and ester. To complete the transesterification process stiochiometrically, 3:1 molar ratio of alcohol to triglycerides is needed. However, in practice, higher ratio of alcohol to oil ratio is generally employed to obtain biodiesel of low viscosity and high conversion. Among all alcohols that can be used in the transesterification process are methanol, ethanol, proponal and butanol. Methanol and ethanol are widely used and especially methanol because of its low cost9. Vegetable oil is made to react with methanol in the presence of catalyst which produces mixture of alkyl ester and glycerol. This oil can be produced by a two step acid-base process. Mahua oil is transesterified using methanol as reagent and H2SO4 and KOH as catalysts, to yield biodiesel (mahua oil methyl ester). Table 3 – Accuracy details of the Gas analyzer and Smoke meter S. No 1 2 3 4 5

Model of the gas analyzer pollutant CO2 HC NOx Smoke meter Smoke intensity

AVL 444 di-gas analyser range 0-10 % volume 0-20000 HC 0-5000 ppm AVL 437 Smoke meter 0-100 opacity in %

Accuracy 0.01 ± 10 ppm ± 10 ppm

± 1% full scale reading

Table 4  Uncertainties of some measured and calculated parameters S. No 1 2 3 4 5

Parameter

Percentage uncertainties

NOx CO2 HC Kinematic viscosity SFC

± 0.1 ± 0.01 ± 0.1 ± 1.3% ± 1.5%

Table 5  Fatty acid composition of mahua oil Fatty acid

Formula

Structure

Weight (%)

Arachidic Linoleic Oleic Stearic Palmitic

C20H40O2 C18H32O2 C18H34O2 C18H36O2 C16H32O2

20:0 18:2 18:1 18:0 16:0

1.5 14.3 37.0 22.7 24.5


46 Results and Discussion Brake thermal efficiency

Figure 2 shows variation of brake thermal efficiency with respect to brake power for B100 to B0. As can be seen, B0 and B25 have almost the same maximum brake thermal efficiency of 14.9% and 29.5% for both the fuel at no load and full load condition, respectively. It may be noted that at all loads, B100 gives lower brake thermal efficiency. At no load and full load, the brake thermal efficiency for B100 is 7.41% and 6.39% is lower compared to B0 and B25 fuel. The same trend is observed for all blends of fuel. From Table 2, it is evident that calorific value of B0 is higher than that of B100. The Brake thermal efficiency depends on heating value and specific gravity. The combination of heating value and mass flow rate indicate energy input to the engine. This energy input to the engine in case of B50, B75 and B100 are more compared to neat diesel. This may be the reason to have lower brake thermal efficiency for all blends of fuel as compared with B0. The results are quite similar to what is reported in reference9.

consumption decreases with the increase in load for all blends of fuel. However, at each load B0 and B25 have the lowest specific fuel consumption and these increase with the blend value. This is due to comparatively higher viscosity and lower calorific value. This is due to increase in fuel quantity with increase in load which causes better utilisation of air leading to better combustion. At no load, diesel engines operate with very lean mixture. Heat release rate

Figure 4 shows variation of heat release rate with respect to crank angle for B100 to B0 at full load condition of the engine. From the figure, it is observed that the B0 gives maximum heat release rate of 115.42 kJ/m3deg followed by B25 (Table 6), the value of heat release rate is 110.76 kJ/m3deg whereas for B100 the value is 67.89 kJ/m3deg at zero degree crank angle at full load condition. This indicates better combustion for B0 fuel as compared to all other blends. However, as compared with B0, the percentage reduction in heat release rate for B100 is41.17% at zero degree crank angle. This is due to the

Specific fuel consumption

The variation in specific fuel consumption for B100 to B0 is shown in Fig. 3. From this figure, it is seen that the B0 and B25 give lowest specific fuel consumption of 0.56 and 0.27 kg/kW.h respectively for both the fuel at no load and full load. However, the B100 gives the highest specific fuel consumption of 0.62 and 0.31 kg/kW.h respectively at no load and full load. For B100, the percentage increase in specific fuel consumption at no load and full load is 11.29% and 16.42% respectively as compared to B0 and B25. The same trend is observed for all blends of fuel. From Table 2, it is seen that all the blends have lower calorific value compared to B0. Specific fuel

Fig. 2  Brake thermal efficiency versus brake power

Fig.3  Specific fuel consumption versus brake power

Fig.4  Heat release rate versus crank angle


reduction in calorific value for B100 as compared with B0. Lower injection timing gives better combustion. The results are quite similar to reported study2. Cylinder pressure

Figure 5 shows variation of cylinder pressure with respect to crank angle for B100 to B0 at full load of the engine. From Table 7, it is seen that the peak pressure occurs at 8±1 degree crank angle for all blends of fuel at full load condition. The B0 gives maximum peak pressure of 62.493 bar as compared to other blends of fuel. However, B25 gives 62.485 bar of peak pressure at the same load. There is not much difference between B0 and B25. The delay period has been evaluated as 8±1 degree crank angle between the start of injection and the start of combustion during the process at full load condition. Therefore B25 seems to be the better option from the point of view of combustion as compared to other blends. From Table 2, it can be seen that the B25 has got higher caloric value as compared to other blends of fuel. But as compared to B0 it is only slightly lower. The percentage reduction of calorific value for B25 is 3.6% as compared with B0. This may be the reason for the slight reduction in the cylinder pressure for B25 as compared to B02.

increase in exhaust gas temperature is not much different from B0 at no load and full load conditions whereas for B100, the percentage increase in exhaust gas temperature is 6.17% and 0.55% respectively at no load and full load conditions. From the figure, it is also observed that as the load increases, the exhaust gas temperature also increases for all blends of fuel. This could be due to the increased heat losses of the higher blends, which is also evident from their lower brake thermal efficiencies as compared to neat diesel (B0)7. Oxygen concentration

The variation of oxygen concentration for B100 to B0 is shown in Fig. 7. The oxygen concentration decreases for B0 than that of other blends of fuel.

Exhaust gas temperature

Figure 6 shows variation of exhaust gas temperature with respect to brake power of B100 to B0. It is observed that the B0 gives lowest exhaust gas temperature of 180°C and 361°C respectively at no load and full load conditions, whereas the B25 gives slightly higher exhaust gas temperature of 181°C and 362°C as compared to all blends of fuel. The same trend is observed for all blends of fuel. For B25, the percentage

Fig.5  Cylinder pressure versus crank angle

Table 6  Heat release rate for different blends Crank angle, degree -30 0 30 60 90

B0

B25

B50

B75

B100

-4.957 115.422 18.391 11.039 0.53

-4.152 110.755 19.095 8.005 4.776

-5.066 105.239 19.516 8.666 0.864

-4.754 92.93 19.538 9.66 5.785

-3.346 67.897 18.914 11.54 1.031

Fig.6  Exhaust gas temperature versus brake power

Table 7  Cylinder pressure for different blends Crank angle, degree -180 -120 -60 0 8±1 60 120 180

B0

B25

B50

B75

B100

1.251 1.666 5.399 49.944 62.493 13.022 4.881 2.703

1.264 1.627 5.361 50.735 62.485 12.88 4.842 2.768

1.161 1.628 5.361 53.173 61.676 13.036 4.895 2.665

1.169 1.636 5.422 51.418 60.889 13.407 5.059 2.725

1.327 1.69 5.371 55.931 60.390 13.15 4.956 2.83

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Fig.7  Oxygen concentration versus brake power


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From the test results, it is seen that at no load and full load, the B0 gives lowest oxygen concentration of 15.9% and 9.1% by volume respectively, whereas the B25 gives almost the same oxygen concentration as that of B0. But B100 gives highest oxygen concentration of 16.2% and 9.4% by volume compared to all blends of fuel. The same trend is observed for other blends of fuel. As compared with B0, the percentage increase of oxygen concentration for B100 is 1.6% and 1.2% respectively at no load and full load conditions. From the results, it is evident that as load increases the oxygen concentration decreases. The oxygen concentration in the exhaust shows that there is comparatively poor utilization of air in the combustion chamber. In the case of ester based fuel, as it contains oxygen, the air fuel ratio requirement is lower compared to diesel fuel for complete combustion. At no load, the percentage increase in oxygen is higher than that of full load for B100 as compared to B0. Therefore, when the load increases, there is a decreasing trend of oxygen. It implies that B100 tends towards incomplete combustion during the operation10. Carbon dioxide

Figure 8 shows the variation of carbon dioxide with respect to brake power for B100 to B0. From the test results, it is seen that the neat diesel (B0) emits highest and B100 emits lowest CO2 emission for all loads compared to all other blends of fuel. The B25 gives almost the same as that of B0. Not much variation between B0 and B25 is found in terms of percentage variation in CO2. For B100 at full load and no load condition, the percentage reduction in CO2 is 58.82% and 34.88% respectively as compared with B0. The same trend is observed for all other blends of fuel. It seems that the B0 gives better combustion with highest CO2 emissions. The same is observed in oxygen concentration for B0 which is lower than that of other blends of fuel.

Fig. 8  Carbon dioxide versus brake power

Carbon monoxide

The variation in CO for B100 to B0 is shown in Fig. 9. From the test results, it is evident that the B0 and B25 give lowest CO of 0.04% and 0.12% by volume at no load and full load conditions, whereas B100 gives highest CO of 0.05% and 0.22% by volume respectively. The percentage increase in CO for B100 is 20% and 45.45% at no load condition as compared with B0 and B25. The CO mainly depends upon the physical and chemical properties of the fuel. From Table 2, it can be seen that B0 properties are favorable to have lower CO as compared with B100. This is due to the oxygen content and cetane number of the blend. Since the methyl ester of mahua oil based fuel contains oxygen in the fuel itself and it acts as a lesser combustion promoter inside the cylinder. Smoke density

Figure 10 shows the variation of smoke density over the complete load range. It can be seen from Fig. 10 that for all blends including neat diesel the smoke density increases with load. This is to be expected, because in diesel engine which is a quality governed engine, the combustion depends upon the local air fuel ratio. Increase in load at constant speed is achieved by increasing the fuel quantity. It is

Fig.9  Carbon monoxide versus brake power

Fig.10  Smoke density versus brake power


evident that at no load, B25 has the lowest smoke density of 17.5 HSU, whereas B100 has the highest smoke density of 39.3. It is interesting to note that B25 emits lower smoke compared to neat diesel (B0). This may be due to the chemistry of fuel blend which may promise conducive atmosphere for lower smoke density for B25 compared to B0. From Table 2 it is evident that specific gravity change for B25 compared to B0 is quite small (0.82 to 0.83) and fire point increase is less than 10°C. Further there is good increase (46 to 51.6) in cetane number between B0 and B25. Probably this is the reason for the decrease in smoke density at no load. Further at no load, the engine is operating at very lean mixture. As the load is increased from no load to 75% there is only gradual increase in smoke density. However, the smoke density for B25 is lower than B0 over their load range for the reasons explained above B75 and B100 are almost bunching together in this load range due to the fire point which is greater than 100°C. It can also be seen from Fig. 10, as the load increases from 75 to 100%, there is a steep rise in the smoke density for all the blends, as well as neat diesel. This is to be expected because more fuel is injected into the engine to take care of the load. As the engine is running at constant speed of 1500 rpm, there is less time for complete combustion to take place which can cause an increase in smoke density.

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with B100. At full load condition, for B0 the percentage reduction in HC is 9.72% as compared with B100. However, the B75 blend gives better reduction in HC as compared with B0, B25, B50 and B100 at full load condition. The percentage reduction in HC for B75 is 6.94% as compared with B0 fuel at full load condition of the engine whereas at no load the percentage reduction in HC is zero as compared to B0 fuel. This may be due to the viscosity and surface tension that affects the penetration rate, maximum penetration and droplet size of the fuel, which in turn affects the mixing of fuel and air. Cetane number of the fuel also plays a vital role in ignition process. From Table 2, it can be seen that the cetane number of B100 is higher than that of B0 (46 to 52.4). Therefore the B0 emits more hydrocarbon than that of B10010. Oxides of nitrogen

The variation in hydrocarbon for B100 to B0 is shown in Fig. 11. The hydrocarbon decreases for B100 and B75 than that of B0 fuel at full load condition of the engine. From the test results, it is observed that there is a small difference of 0.01 in HC (g/kW.h) for B100 and B0 fuel at no load condition. At no load condition, the percentage reduction in HC is 4.35% at no load condition for B0 as compared

The variation in NOx for B100 to B0 is shown in Fig. 12. It is evident that the maximum NOx (g/kW.h) is 3.02 for B100 whereas for B0 is 2.818 at no load. At full load, the maximum NOx of 0.422 for B100 whereas for B0 it is 0.355. The variation in NOx at full load is higher at no load condition of B100 as compared with B0 fuel. At full load, the percentage reduction in NOx for B100 is 8.51% as compared with B0 whereas at no load the variation in NOx is 2.52%. However, the B75 blend gives better reduction in NOx as compared with B0, B25, B50 and B100 at full load condition. The percentage reduction in NOx for B75 is 10.76% as compared to B0 fuel at full load condition of the engine whereas at no load, the percentage reduction in NOx is 3.01% for B75. The percentage reduction in NOx for B100 is 0.94% as compared to B75 fuel. This is due to decrease in exhaust gas temperature. It is well known that vegetable based fuel contains a small amount of nitrogen. This contributes towards the NOx production8.

Fig.11  Hydrocarbon versus brake power

Fig.12  Oxides of nitrogen versus brake power

Hydrocarbon

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Conclusions From this study, it is concluded that the B0 and B25 give, optimum performance, whereas B100 and B75 give the lower emissions of HC and NOx. Finally, it is concluded that B25 could be used as a viable alternative fuel to operate four-stroke tangentially vertical single cylinder direct injection diesel engine with injection pressure of 250 bar and injection timing of 20° bTDC, thereby saving 25% of the precious fossil diesel fuel. References 1 Clark S J, Wanger L, Schrock M D & Piennaar P G, J Am Oil Chem Soc, 61 (1984) 1632-1637. 2 Scholl K W & Sorenson S C, SAE 930934, 1993. 3 Narayana Reddy J & Ramesh A, Int J Green Energy, Energy Environ, 1(3) ( 2010) 1-6. 4 Venkatraman M & Devaradjane G, Int J Green Energy, Energy Environ, 1(3) (2010) 7-12. 5 Raslavicius, Laurencas, Bazaras & Zilvinas, Indian J Eng Mater Sci, 17 (4) (2010) 243-250. 6 Saravanan N, Nagarajan G & Puhan S, Biomass Bioenergy, 34 (2010) 838-843. 7 Raheman H & Ghadge S V, Fuel, 86 (2007) 2568-2573. 8 Puhan S, Vedaraman N, Sankaranarayanan G, Boppana V & Ram B, Renewable Energy, 30 (2005) 1269-1278. 9 Puhan S, Vedaraman N, Boppana V, Ram B, Sankaranarayanan G & Jeychandran K, Biomass Bioenergy, 28 (2005) 87-93. 10 Sukumar Puhan, Nagarajan G, Vedaraman N & Ramabramhnam, Int J Green Energy, 4 (2007) 89-104.

11 Sundarraj C, Arul S, Sendilvelan S & Saravanan C G, Thermal Sci, 14 (2010) 979-988. 12 Sundarraj C, Arul S, Sendilvelan S & Saravanan C G, Int J Eng Res Ind Appl, 2 (2009) 197-208. 13 Kapilan N N, Reddy R P & Anjuri E R, Thermal Sci, 12 (2008) 151-156. 14 Kapilan N & Reddy R P, J Am Oil Chem Soc, 85 (2008) 185-188. 15 Kapilan N, Ashok babu T P & Rana Pratap Reddy, Effect of injection time on performance and emissions of mahua biodiesel operated diesel engine, presented at XXI Nat Conf on I.C. Engines and Combustion, Bapuji Institute of Eng & Tech, Karnataka, India, 2009. 16 Sharanappa Godiganur, Ch. Suryanarayana Murthy & Rana Pratap Reddy, Diesel engine emissions and performance from blends of mahua methyl ester and diesel, presented at XXI Nat Conf on I.C. Engines and Combustion, Bapuji Institute of Eng & Tech, Karnataka, India, 2009. 17 Ramesha D K, Premakumara G, Manjunatha M C & Honne gowda, A study on effective use of mahua methyl ester as alternative to diesel, presented at XXI Nat Conf on I.C. Engines and Combustion, Bapuji Institute of Eng & Tech, Karnataka, India, 2009. 18 Kale N W, Deshpande N V & Bhale P V, Performance and emission study of mahua (Madhuca indica) straight vegetable oil in a naturally as pirated direct injection diesel engine, presented at XXI Nat Conf on I.C. Engines and Combustion, Bapuji Institute of Eng & Tech, Karnataka, India, 2009. 19 Dhananjaya D A, Sudhi C V & Mohanan P, Int J Mech Mater Eng, 4 (3) (2009) 220-231. 20 Ganesan V, Internal Combustion Engines, 3rd ed (Tata Mcgraw Hill, India), 2000. 21 Heywood J B, Internal Combustion Engine Fundamentals, (McGraw Hill, USA), 1988.