Indian Journal of Engineering & Materials Sciences Vol. 18, June 2011, pp. 204-210 Comparative study of engine performance and exhaust emission characteristics of a single cylinder 4-stroke CI engine operated on the esters of hemp oil and neem oil S S Ragit a *, S K Mohapatra a & K Kundu b a Department of Mechanical Engineering, Thapar University, Patiala 147 004, India b Mechanical Engineering Research and Development organization, Ludhiana 141 006, India Received 6 October 2010; accepted 10 June 2011 In this study, the biodiesel produced from selected non-edible oils are prepared by a method of alkaline catalyzed transesterification. Esters of non-edible vegetable oils such as hemp oil and neem oil are potentially effective diesel substitute. The study is carried out to investigate the performance and emission characteristics of selected fuel in a stationary single cylinder, four stroke, naturally aspirated direct injection diesel engine and compare it with mineral diesel. The engine performances (thermal efficiency, brake specific fuel consumption, brake specific energy consumption, and exhaust gas temperature) whereas exhaust emissions (oxides of nitrogen, unburned hydrocarbon and smoke opacity) are evaluated. The experimental results in each case are compared with baseline data of mineral diesel. Significant improvements have been observed in the performance parameters of the engine as well as exhaust emissions. The results show a 45.07% reduction in NOx, 84.42% reduction in HC, 28.35% in smoke but brake thermal efficiency increased slightly (0.19%) at full load for hemp biodiesel, 6.06% reduction in NOx, 2.59% reduction in HC, 18.39% reduction in smoke at full load for neem biodiesel, respectively. The experimental study indicates that selected fuel can be used as a fuel in compression ignition engine without any engine modification. Keywords: Biodiesel, Fuel properties, Performance characteristics, Emission characteristics, Diesel Comparative analysis engine, Vegetable oil is one of the alternatives which can be used as fuel in automotive engines either in the form of straight vegetable oil, or in the form of ethyl or methyl ester. The energy needs of the world are increasing rapidly. The decrease in fossil fuels, emission pollution caused by them and increasing fuel prices make biomass energy sources more attractive. The increase in energy demand and decrease in oil reserves have been focused on biofuels. Biodiesel is a fuel that is manufactured from vegetable oils with the help of catalysts, and may be directly used in diesel vehicles with little or no modification. The biodiesel is reported to be sulfur-free, nontoxic, biodegradable oxygenated and renewable. And the characteristics of biodiesel are very close to diesel fuel 1,2. And some are better than diesel such as higher cetane number, no aromatics, almost no sulfur, and more than 10% oxygen by weight, which reduce the emission of carbon monoxide, unburned hydrocarbon, and volatile organic compounds 3,4. An experimental study *Corresponding author (Email:satish_ragit@yahoo.com) is carried out to evaluate and compare the use of cottonseed oil, soybean oil, sunflower oil and their corresponding methyl esters. It shows that all tested biodiesel or vegetable oil blends, can be used safely 5,6. An experimental study is also carried out to examine fuel properties, performance and emissions of different blends of methyl ester of pongamia, jatropha and neem in comparison to diesel fuel. The results indicated that diesel blends showed reasonable efficiencies, lower smoke, CO and HC 7. The vegetable oil esters from edible oils may not be the right option for their substitution in diesel engine due to the lack of self-sufficiency of edible oil production in India. Hence, attention has been diverted to test the suitability of non-edible vegetable oils for diesel engine. With the abundance of forest and tree-borne non-edible oils available in India, limited attempts have been made to use the ester of selected non-edible as the alternative fuels for diesel engine 8. In this experimental study, the biodiesel from different non-edible oils was produced by a method of alkaline-catalyzed transesterification. The objectives
RAGIT et al.: PERFORMANCE AND EXHAUST EMISSION CHARACTERISTICS OF CI ENGINE 205 of this experimental study are to assess performance and emission characteristics of a diesel engine when tested with selected fuels and compared with diesel as a reference fuel. Materials and Method The methyl esters of hemp oil and neem oil were supplied from Mechanical Engineering Research and Development Organization, Ludhiana and CI engine testing had been performed in I.C. Engine Laboratory, Thapar University, Patiala. Fuel properties The fuel properties of hemp and neem methyl ester and standard diesel are summarized in Table 1. Two methyl esters were compared with diesel fuel and optimized better alternative option for diesel fuel. Many researchers investigated fuel properties of different non-edible oils and its biodiesels and compared with diesel fuel to improve engine performance 9-14. Engine set-up Schematic diagram of computerized CI engine test rig is shown in Fig. 1. The engine tests were conducted on single cylinder, direct injection water cooled compression ignition engine. It studies characteristic fuel properties and experimental procedure adopted to evaluate performance of a 5.2 kw, diesel engine on the blends. The engine was always operated at a rated speed of 1500 rev/min. The engine was having a conventional fuel injection system. The engine had been provided with a hemispherical combustion chamber with overhead valves operated through push rods. Cooling of the engine was accomplished by circulating water through the jackets of the engine block and cylinder head. Five gas analyzer and Hartridge smoke meter were used for measuring NOx and smoke opacity. The five gas analyzer and smoke meter are shown in Figs 2 and 3, respectively. The technical specifications of NOx and smoke meter are shown in Table 2 and 3, respectively. The experimental data generated were calculated, presented through appropriate graphs. Performance and emission test was conducted on various biodiesel blends in order to optimize the blend concentration for small term usage in CI engines. This test was aimed at optimizing the concentration of ester in the biodiesel blends to be used for one hour engine operation. To achieve this, several blends of varying concentrations were prepared ranging from 0% to 100%. These blends Table 1 Fuel properties of hemp and neem methyl ester Properties HME NME Diesel ASTM D6751 EN 14214 Density (15 C), kg/ m 3 858 868 830-860-900 Viscosity (40 C ), cst 1.13 2.7 3.7 1.9-6.0 3.5-5.0 Flash point, C 47 76 60 >130 >101 Fire point, C 55 81 65 - Min 120 Cloud point, C -4 9-12 10-1 Pour point, C -17 2-16 -15 - Calorific value, MJ/kg 42.92 39.81 43 - - Fig. 1 Computerized CI engine test rig Fig. 2 AVL Five gas analyzer
206 INDIAN J ENG. MATER. SCI., JUNE 2011 were then subjected to performance and emission tests on the engine. The optimum blend was found out from the graph based on maximum thermal efficiency and other engine emission characteristics. Results and Discussion Fuel properties The experimental results indicated that the relative density of hemp methyl ester is slightly increased to that of diesel. The kinematic viscosities of diesel and hemp methyl ester were found as 2.6 and 1.13 cst at 40 C. Hemp methyl ester was observed the kinematic viscosity 56.54% less than that of diesel. The calorific value of diesel and Hemp methyl ester were found as 43, and 42.92 MJ/kg respectively. The calorific value of hemp methyl ester is decreased by 0.18% as compared to diesel fuel. The hemp methyl ester was found to have lower flash and fire point than those of diesel fuel. The results thus indicate that pour point of hemp methyl ester is higher than that of diesel whereas cloud point of hemp methyl ester is lower Fig. 3 AVL Hartridge Smoke meter than that of diesel. The relative density of neem methyl ester was observed 4.58% higher than that of diesel. The experimental results indicated that the relative density of neem methyl ester was slightly increased to that of diesel. The kinematic viscosity of diesel, and neem methyl ester were found as 3.7, and 2.7 cst at 40 C The results indicated that the neem methyl ester had the kinematic viscosity 3.846% more than that of diesel. The calorific value of diesel and neem methyl ester were found as 43 and 39.81 MJ/kg, respectively. The calorific value of neem methyl ester is decreased by 7.42% than that of diesel. The neem methyl ester was found to have higher flash and fire point than those of diesel. The result also reveals that the cloud and pour point of neem methyl ester are lower than those of diesel. CI Engine analysis Performance characteristics Brake thermal efficiency (BTE) Figures 4 and 5 show variation of brake thermal efficiency (BTE) with respect to brake mean effective pressure (BMEP) for different fuels. BMEP of a diesel engine directly relates to the brake power. Brake thermal efficiency of HME was observed 17.83% higher than that of diesel at part load condition but slightly increases at full load condition. Brake thermal efficiency of HME20 was observed 3.58% higher than that of Table 2 Technical specification of the 5-gas analyzer Measurement principal Voltage Power input Dimensions Weight Rated flow rate Minimum flow rate CO, HC, CO2- Infrared Measurement and O2 and NOx-Electrochemical measurement 195-253 V 150 W 360 mm 370 mm 220 mm 14 kg 360 L/h 180 L/h Table 3 Technical specifications of meter S.N. Parameter Details 1 Accuracy and reproducibility ±1%full scale reading 2 Measuring range 0 to 100% opacity in percentage, 0 to infinity absorption in m -1 3 Measurement chamber Effective length 0.430±0.005 4 Heating time 20 m minutes approximately 5 Light source Halogen bulb 12 V/ 5W 6 Measurement value indication Processor control LED, Display 4 15 mm 7 Detector Selenium photocell of 45 mm diameter 8 Colour temperature 3000±150 K 9 Temperature gauge Electric temperature measuring instrument 10 Power consumption 600 W 11 Weight 50 kg 12 Dimensions 570(width) 500(breadth) 1250 (height)
RAGIT et al.: PERFORMANCE AND EXHAUST EMISSION CHARACTERISTICS OF CI ENGINE 207 diesel at part load condition but slightly increases at full load condition. It increased due to the reduction in heat loss and increase in power output with increase in load. In all cases, brake thermal efficiency showing increasing trend at all blends but not more than diesel. The maximum brake thermal efficiency obtained while using NME100, NME60 and NME20 were 16.53%, 15.16% and 12.8% respectively at part load whereas lower brake thermal efficiency obtained at NME80 and NME40 which were 5.86% and 9.7% respectively at part load. In case of full load, NME show decreasing trend with diesel fuel. Brake thermal efficiency of diesel is 15.37% and 36.89% at part load and full load, respectively. Specific fuel consumption (SFC) Figures 6 and 7 show variation of specific fuel consumption (SFC) with respect to brake mean effective pressure (BMEP) for different fuels. The brake specific fuel consumption of HME was found 6.42% lower than that of diesel at part load condition and 3.08% lower than that of diesel at full load condition. Brake Fig.6 Variation of specific fuel consumption with brake mean Fig.4 Variation of brake thermal efficiency with brake mean Fig.5 Variation of brake thermal efficiency with brake mean Fig. 7 Variation of specific fuel consumption with brake mean
208 INDIAN J ENG. MATER. SCI., JUNE 2011 specific fuel consumption of HME20 was found 1.28% lower than that of diesel at part load condition and 0.44% lower than that of diesel at full load condition. The brake specific fuel consumption is found to decrease with increase in brake mean effective pressure. This is due to the higher percentage increase in brake power with brake mean effective pressure as compared to the increase in fuel consumption. At part load, brake specific fuel consumption of NME100 was obtained 8.25% lower than that of diesel whereas brake specific fuel consumption of NME100 was observed 27.75% higher than that of diesel at full load. Finally, we concluded that it was showing decreasing trend at part load on one hand, it was showing increasing trend at full load. It is found that the calorific value of neem methyl ester is decreased by 7.42% than that of diesel. With increase in biodiesel percentage in the blends, the calorific value of fuel decreases. Hence, the specific fuel consumption of higher percentage of biodiesel in blends increase as compared to that of diesel. The specific fuel consumption of neem oil methyl ester is higher than that of diesel for full load. This is caused due to the combined effect of higher viscosity and high density of tested fuels. Exhaust gas temperature (EGT) Figures 8 and 9 show variation of exhaust gas temperature (EGT) with respect to brake mean effective pressure (BMEP) for different fuels. It increases at all load condition. HME shows 5.74% higher than that of diesel fuel at part load condition whereas it shows 12.78% higher than that of diesel fuel at full load condition. HME20 shows 1.15% higher than that of diesel fuel at part load condition whereas it shows 2.48% higher than that of diesel fuel at full load condition. It is observed that exhaust gas temperature increases with load because more fuel is burnt at higher loads to meet the power requirements. This may be due to the oxygen content of the fuel which improves combustion and thus may increase the exhaust gas temperature. Higher exhaust gas temperature may be because of better combustion of HME. When biodiesel concentration is increased, the exhaust gas temperature increases by small value. NME100 and its blend showing decreasing in nature at part load. The exhaust gas temperature of NME100 was obtained 6.83% lower than that of diesel at part load and it increases at full load by 14.44% than that of diesel. It shows increasing in trend at full load. Exhaust emission characteristics Oxides of nitrogen (NO x ) The variation of oxides of nitrogen (NO x ) with respect to brake mean effective pressure (BMEP) for different fuels as shown in Figs 10 and 11. It reduces at all loading. Oxides of nitrogen of HME was obtained 1.61% less than that of diesel at part load condition and 45.07% lower than that of diesel fuel at full load condition. Oxides of nitrogen of HME20 was obtained 0.32% less than that of diesel at part load condition and 9.01% lower than that of diesel fuel at full load condition. It shows effective result at full load Fig. 8 Variation of exhaust gas temperature with brake mean Fig. 9 Variation of exhaust gas temperature with brake mean
RAGIT et al.: PERFORMANCE AND EXHAUST EMISSION CHARACTERISTICS OF CI ENGINE 209 condition. It can be seen that NO X emission was a direct function of engine power output. This trend was occurred as NO X formation is a temperature dependent phenomenon. NO X emission of NME100 and its blend show decreasing trend with diesel fuel at full load condition but it increases at part load. NME100 lowers by 3.22% and 6.06% at part load and full load conditions, respectively. Unburned hydrocarbon (UBHC) The variation of unburned hydrocarbon (UBHC) with brake mean effective pressure (BMEP) for different fuels is shown in Figs 12 and 13. It was showing decreasing trend with diesel fuel at all load condition. HME decreases 50.87% than that of diesel at part load condition whereas it again reduces 84.42% than that of diesel fuel at full load condition. HME20 decreases 10.17% than that of diesel at part load condition whereas it again reduces 16.88% than that of diesel fuel at full load condition. NME100 and its blend show decreasing trend at all load conditions. It lowers by 5.26% and 2.59% with diesel fuel at part and full load respectively. Smoke opacity (SO) The variation of smoke opacity (SO) with brake mean effective pressure (BMEP) for different fuels is shown in Figs 14 and 15. It increases at part load condition. However, it reduces at full load condition. HME increases by 89.18% than that of diesel fuel at part load condition whereas it lowers by 28.35% than that of diesel fuel at full load condition. HME20 increases by 17.83% than that of diesel fuel at part load condition whereas it lowers by 5.67% than that of diesel fuel at full load condition. As smoke is low then better combustion of ester/oil takes place. It decreased due Fig. 12 Variation of unburned hydrocarbon with brake mean Fig. 10 Variation of oxides of nitrogen with brake mean Fig. 11 Variation of oxides of nitrogen with brake mean Fig. 13 Variation of unburned hydrocarbon with brake mean
210 INDIAN J ENG. MATER. SCI., JUNE 2011. Fig. 14 Variation of smoke opacity with brake mean effective pressure for neem methyl ester and its respective blends Fig. 15 Variation of smoke opacity with brake mean effective pressure for neem methyl ester and its respective blends to preheating. This may be due to the reduction in viscosity and subsequent improvement in spray, fuel-air mixing and combustion characteristics by preheating. NME100 and its blend revealed that it increases with high percentage at part load and it decreases at full load condition. It lowers by 18.39% than that of diesel fuel at full load. It is mainly due to emission of heavier molecules of hydrocarbon and particulates. As smoke is low then better combustion of tested fuel takes place. Conclusions Relative densities and calorific values of both methyl ester show slightly increasing trend and slightly decreasing trend with respect to diesel fuel. Hemp methyl ester shows excellent kinematic viscosity as compared to neem methyl ester and diesel fuel. Neem methyl ester reveals high flash and fire point whereas hemp methyl ester reveals good cold flow properties as compared to diesel fuel. The brake thermal efficiencies of both methyl ester indicates increasing trend at all loads. In case of specific fuel consumption, both methyl esters show slightly decrease in nature but hemp methyl ester reveals good results than neem methyl ester and diesel in case of exhaust gas temperature. In relation with emission characteristics, hemp methyl ester shows good results than neem methyl ester in the view of oxides of nitrogen and unburned hydrocarbon at all loads. However, both methyl esters reveal slightly increasing trend at all loads. The present studies reveal that methyl ester of hemp oil could be a good option as alternative fuel without any engine modification. Acknowledgement The authors are thankful to Thapar University, Patiala for providing C.I. Engine testing and fuel testing facilities. Nomenclature NO x = oxides of nitrogen UBHC = unburned hydrocarbons SO = smoke opacity EGT = exhaust gas temperature SFC = specific fuel consumption BTE = brake thermal efficiency BMEP = brake mean effective pressure HME100 = 100% hemp methyl ester and 0% Diesel NME100 =100% neem methyl ester and 0% Diesel HME20 = 20% hemp methyl ester and 80% Diesel NME20 = 20% neem methyl ester and 80% Diesel References 1 Chang D Y Z, Gerpen J H V & Lee I, JAOCS, 73 (1996) 1549-1555. 2 Freedman B & Pryde E H, ASAE Publ, 4-82 (1982) 117-122. 3 Labeckas G & Slavinskas S, Energy Convers Manage, 47 (2006)1954-1967. 4 Schumacher L G, Borgelt S C & Fosseen D, Bioresource Technol, 57 (1996) 31-36. 5 Rakopoulos D C, Antonopoulos A K & Rakopoulos C D, Energy Convers Manage, 47 (2006) 3272-3287. 6 Rakopoulos D C, Rakopoulos C D & Hountalas T D, Fuel, 87 (2008) 147-157. 7 Venkateswara Rao T, Prabhakar Rao G & Hema Chandra Reddy K, Jordan J Mech Ind Eng, 2 (2008) 117-122. 8 Bhatt Y C, Use of some non-edible vegetable oils as a source of energy for CI engines, Ph.D. Thesis, IIT, Kharagpur, 1987. 9 Foidl N & Foidl G, Hackel S, Bioresource Technol, 58 (1996) 77-82. 10 Fukuda H, Kondo A & Noda H, J Biosci Bioeng, 92 (5) (2001) 405-416. 11 Karmee S & Chadha A, Bioresource Technol, 96 (2005) 1425-1429. 12 Antolin G & Briceno F, Bioresource Technol, 83 (2002) 111-114. 13 Meher L & Naik S, Bioresource Technol, 97 (2006) 1392-1397. 14 Ramadhas A & Jayaraj S, Fuel, 84 (2005) 335-340.