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  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 171 PERFORMANCE EVALUATION OF A LOW HEAT REJECTION DIESEL ENGINE WITH COTTON SEED BIODIESEL Dr. V. NAGA PRASAD NAIDU1 , Prof. V. PANDU RANGADU2 1 (Principal,Intellectual Institute of Technology,Ananthapuramu, A.P,ndia,nagveluri@gmail.com) 2 (Prof. in Mech Engg., JNTUCEA, Ananthapuramu, A.P, India, pandurangaduv@yahoo.com) ABSTRACT In recent years the search for alternative fuels has become inevitable due to fast depletion of fuels and huge demand for diesel in transport, power and agricultural sectors. One of the best alternatives is Biodiesels obtained from Vegetable oils. Due to the lower temperatures and pressures in the normal diesel engines, the burning of the vegetable oils is not complete, the low heating value and high viscosity of Biodiesels causes to reduce efficiency of the engine. The low heat rejection (LHR) diesel engine is only solution to overcome these problems. In the present work Investigations are carried out to evaluate the performance and emissions characteristics of a low heat rejection (LHR) diesel engine consisting of an air gap insulated piston with Cotton seed biodiesel. The air gap between the piston crown and piston skirt is varied from 1mm to 2.5mm to find best one at which the performance and emission characteristics are good. An increase in engine power, decrease in specific fuel consumption and significant improvements in exhaust emissions were found at 2mm air gap in the piston as compared with other air gaps. Keywords: Cotton Seed Bio Diesel, Low Heat Rejection Engine, Emissions, Hydro Carbons, Air Gap Piston. I. INTRODUCTION In the scenario of increasing energy demand, the escalating petroleum prices and depleting of fossil fuel reserves has triggered to search for an alternative fuels. Vegetable oils can be an important alternative to the diesel oil, since they are renewable and can be produced in rural areas1 . The inventor of diesel engine Rudolpf diesel predicted that the plant based oils are widely used to operate diesel engine. The bio diesel has great potentials as alternative diesel fuel2 . But use of pure bio diesel can cause numerous engine related problem such as injector choking, piston deposit formation and piston ring sticking due to higher viscosity and low volatility of bio diesel3 . Transesterification4 of INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 2, February (2014), pp. 171-179 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2014): 3.8231 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 172 bio diesel provides a significant reduction in viscosity, thereby enhancing their physical and chemical properties and improve the engine performance. Due to the lower temperatures and pressures in the normal diesel engines, the burning of the vegetable oils is not complete. The drop in efficiency is due to its low heating value and high viscosity. It is well known fact that about 35% of heat generated5 is lost in to the surroundings of the combustion chamber, most heat transfer happens through the piston. If these losses be controlled, the thermal potency of the engine may be more increased. Hence in order to reduce the heat transfer through the piston in the present experimental work an air gap insulated engine (AGIE) is developed which cut back the heat losses from the piston crown to the piston skirt. This increases the heat in the chamber and heats the incoming fresh charge. So that combustion is complete and thermal potency is improved. In the present work Investigations are carried out to evaluate the performance and emissions characteristics of a low heat rejection (LHR) diesel engine consisting of an air gap insulated piston with Cotton seed Biodiesel. The air gap between the piston crown and piston skirt is varied from 1mm to 2.5mm to find best one at which the performance and emission characteristics are good. II. DEVELOPMENT OF AIR GAP INSULATED PISTON The aim of insulating the piston is to reduce the rate of heat transfer from the crown to skirt as much as possible. Further, the insulated piston is to be similar to the original piston with respect to dimensions and the shape of combustion chamber. So in the present work the piston with air-gap insulation is used. III. TECHNICAL SPECIFICATIONS OF THE ENGINE In this work experiments were conducted on 4 stroke, single cylinder, C.I engine (Kirloskar Oil Engineers Ltd., India) of maximum power-3.68 KW with AVL smoke meter and Delta 1600 S gas analyser. Air-Gap Insulated Piston
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 173 IV. MATERIAL & METHODS In the present work tests were conducted on LHR diesel engine consisting of air gap insulated piston with cotton seed Bio Diesel to evaluate performance and emission characteristics. Cotton has long been known as nature's unique food and fiber plant. It produces both food for man and feed for animals in addition to a highly versatile fiber for clothing, home furnishings and industrial uses. Cottonseed oil has a ratio of 2: 1 of poly n saturated to saturated fatty acids and generally consists of 65-70% unsaturated fatty acids including 18-24% monounsaturated (ole ic) and 42-52% polyunsaturated (linoleic) and 26-35% saturated (palmitic and stearic)6 . The various properties of the cotton seed bio diesel7 is presented in table 1. TABLE I PROPERTIES OF FUEL USED Properties Cotton seed Diesel Density (kg/m3) 874 830 Calorific Value (kJ/Kg) 40000.32 43000 Viscosity @400C(cSt) 4 2.75 Cetan Number 51.2-55 45 Flash Point (o C) 70-110 74 V. RESULTS AND DISCUSSIONS 1. BRAKE THERMAL EFFICIENCY The brake thermal efficiency variation with power output for different amount of air gaps between crown and skirt is illustrated in figure 1. The thermal efficiency depends on the amount of heat produced in the combustion chamber. It further depends upon the amount of fuel present in the chamber, mixture strength and amount of heat given to the charge before combustion. If the charge is preheated before the combustion, fuel vaporization is faster; the fuel will undergo complete combustion and hence increase in the thermal efficiency. Figure1. Variation of Brake thermal Efficiency with power output 0 5 10 15 20 25 30 35 0 1 2 3 4 Brakethermalefficiency(%) Brake Power (kW) 1mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 174 The air gap between crown and skirt acts as an insulator to the heat and that will be given the incoming charge for the combustion. This heat transfer increases with the amount of air gap up to 2mm and thereafter it will decrease. This is because of reduction in the material thickness between crown center and skirt. The brake thermal potency increases with the load. The efficiency of cotton seed oil at 2 mm air gap is 30.5% and for at 1 mm air gap it is 28.8%. The thermal efficiencies at 1.5 mm and 2.5 mm are in between the efficiencies of 1 mm and 2 mm. 2. BRAKE SPECIFIC FUEL CONSUMPTION The figure 2 illustrates the variation of brake specific fuel consumption (BSFC) with power output. The BSFC mainly depends upon the homogeneous mixture formation and complete combustion of the fuel. Due to the cotton seed oil’s higher viscosity it requires higher temperatures for the fuel evaporation in the chamber. With the vaporization of the fuel, the charge becomes homogeneous and further the combustion will complete. Because of the air insulation between crown and skirt the temperature in the combustion chamber increases up to 2 mm air gap and after that it decreases due to the reduction in the material thickness which allows the heat to the skirt. Figure 2: Variation of brake specific fuel consumption with power output At the rated load the BSFC for 1 mm air gap is 0.32 kg/kW.hr. At 1.5 mm and 2 mm air gap it is 14% and 18.75% higher and at 2.5 mm air gap it is 3.12% less than that. 3. EXHAUST GAS TEMPERATURE The variation of exhaust gas temperatures with power output is illustrated in the figure 3. The exhaust gas temperature in the combustion chamber depends on the combustion quality and viscosity of the fuel injected. Further the combustion efficiency depends on the mixture strength in turn the evaporation rate of the fuel. Due to the higher viscosity the vegetable oil evaporation increases with the temperature availability in the chamber and further the combustion. In the LHR diesel engine the air acts as an insulator for the heat transfer and retains the heat in the combustion chamber and further aids for the combustion. The exhaust gas temperature of cotton seed oil for the 1mm air gap at rated load is 2650C and at 2mm air gap it is 9.43% higher than that. The exhaust temperatures at the remaining air gaps are in between these two. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1 2 3 4 BrakeSpecificFuel Consumption(kg/kW-hr) Brake Power (kW) 1 mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 175 Figure 3: Variation of Exhaust gas temperatures with power output 4. VOLUMETRIC EFFICIENCY The variation of volumetric efficiency with power output is illustrated in figure 4. The volumetric efficiency of the engine mainly depends on the combustion chamber temperatures. With the increase in the chamber temperatures the charge temperature increases and this reduces the mass of air and thus less amount of air enters the engine. This reduces the power output. At the rated load for 1 mm air gap the volumetric efficiency is 80.5% and this is dropped by 2% with 2 mm air gap. The efficiency at the remaining air gaps are in between 1 mm air gap and 2 mm air gap. As the temperatures in the chamber increases with the air gap, the volumetric efficiency dropped . Figure 4: Variation of the volumetric efficiency with power output 74 76 78 80 82 84 86 0 1 2 3 4 VolumetricEfficiency(%) Brake Power (kW) 1 mmair gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap 0 100 200 300 400 0 1 2 3 4 ExhaustGasTemperture(0C) Brake Power (kW) 1 mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 176 5. SMOKE DENSITY Figure 5 shows the variation of smoke densities with the power output. The mixing of the fuel with the air in the diesel engine is varied from region to region of the combustion chamber. The smoke in the diesel engine is due to the unburnt liquid particles of fuel or lubricating oil and further it creates partial combustion. The smoke and soot form on the chamber walls due to the incomplete burning of the fuel droplets in the chamber. With the increase in the load more amount of fuel is injected in to the combustion chamber and increases the unburned fuel droplets on the chamber walls. This is more in the rich regions of the combustion chamber. As the cotton seed oil consists of inherent oxygen, it is distributed during the combustion process and enhances the combustion efficiency and reduces the smoke formation. Though more oxygen is presented at higher loads the time available for the atomization is less, further the fuel droplets are larger in size and increase the smoke densities. This formation can be reduced with the complete combustion of the fuel i.e with the higher temperatures in the chamber. In the LHR diesel engine the temperatures in the chamber increases with the air gap and the drops the smoke emissions. The smoke emission for 1 mm air gap at the rated load is 0.52 bosch. Similarly the smoke emissions at the remaining air gaps are 3.85%, 7.69%, and 5.77% lesser than 1 mm air gap. Figure 5: Variation of smoke density with power output 6. HYDROCARBON EMISSIONS (HC EMISSIONS) The hydrocarbon emissions variation with power output is illustrated in figure 6. The HC emissions mainly depend on the fuel atomization and presence of oxygen for the combustion. 0 0.2 0.4 0.6 0.8 0 1 2 3 4 Smokedensity(bosch) Brake Power (kW) 1 mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 177 Figure 6: variation of hydrocarbon emissions with power output Further the improper burning of the fuel and lubricating oil are the other main sources for the emissions. It is observed that at lesser loads less fuel will be injected and the available higher oxygen makes the charge rich and further enhances the combustion and reduces the emissions. These emissions reduce with the higher temperatures in the chamber. This combustion chamber temperature increases with the air insulation between crown and skirt of the piston. The hydrocarbon emissions for 1 mm air gap at the rated load are 645 ppm. The emissions for the remaining air gaps are 1.24%, 2.95% and 1.70% lesser than 1 mm air gap. This is attributed to the higher temperatures in the combustion chamber. 7. CARBON MONOXIDE EMISSIONS (CO EMISSIONS) The figure 7 shows the variation of carbon monoxide emissions with power output. With the higher temperatures in the Air gap insulated engine the combustion improves and further the oxidation of carbon monoxide is also improved. Hence the CO emission in the Figure 7: Variation of CO Emissions with Power output 300 400 500 600 700 800 900 0 1 2 3 4 HydroCarbonEmissions(ppm) Brake Power (kW) 1mm air gap 1.5 mm air gap 2mm air gap 2.5 mm air gap 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1 2 3 4 COemissions(%volume) Brake Power (kW) 1 mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 178 Exhaust drops drastically. At the lower loads due to the rich mixture formation more oxygen will be present and hence the CO converts into CO2 and thus CO emissions plunged. As the load is increased fuel injected increases and consequently CO emissions are also increased. These emissions are remunerated with the higher temperatures in the chamber and inherent oxygen in the cotton seed oil. At the rated load the emissions for the 1 mm air gap is 0.55 % vol. Similarly the emissions for 1.5 mm, 2 mm and 2.5 mm air gap are 5.45%, 9.09% and 3.64% lesser than that. 8. NITROGENOXIDE EMISSIONS The variation of NOx emissions with power output is illustrated in figure 8. In general the nitrogen gas is dormant at the inferior temperature and is dynamic at the elevated temperatures of the combustion chamber. This is further responsive to the oxygen content and reacts with that at higher temperature and forms NOx emissions. At lower loads more oxygen will be available for the combustion and emissions will be increased but it is compensated by lower temperatures in the chamber. Figure 9: Variation of NOx emissions with power output Further as the load Increases in the LHR diesel engine the combustion chamber temperature will also increase and the formation of NOx emissions will also increase. This is further enhanced by the inherent oxygen present in the cotton seed oil. The NOx emission for cotton seed oil at rated load for 1 mm air gap is 630 ppm. The emissions are 1.6%, 3.97% and 2.38% higher at 1.5 mm, 2 mm and 2.5 mm air gap than 1mm air gap. 400 450 500 550 600 650 700 750 0 1 2 3 4 NOxEmissions(ppm) Brake Power (kW) 1 mm air gap 1.5 mm air gap 2 mm air gap 2.5 mm air gap
  • International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 2, February (2014), pp. 171-179, © IAEME 179 VI. CONCLUSIONS The following conclusions are drawn based on the experimental results of the above work: With the air insulation between piston crown and skirt the temperature in the combustion chamber increases. This further enhances the brake thermal efficiency . The air insulation reduces the heat transfer through the piston and in turn in the increases exhaust gas temperature. The volumetric efficiency dropped in the engine and is attributed to the higher temperature in the combustion chamber. This can be further compensated by the turbo charging of the engine The Hydrocarbon emissions and CO emissions are less with the air gap insulated engine due to the complete combustion of the fuel with elevated temperature in the chamber With the higher temperatures in the chamber and inherent oxygen in the cotton seed oil the NOx emissions is increased. It is concluded that out of the four different air gaps between piston crown and skirt tested in LHR diesel engine, 2 mm air gap is best for the cotton seed oil which illustrated the best in terms of efficiency and emissions. VII. ACKNOWLEDGMENT Authors thank authorities of Intellectual Institute of Technology and Intell Engineering College Anantapuramu, AP, India for providing facilities for carrying out research work. REFERENCES [1] Cummins, C., Lyle, Jr. (1993). Diesel's Engine, Volume 1: From Conception to 1918.Wilsonville, OR, USA: Carnot Press, ISBN 978-0-917308-03-1. [2] Agarwal A.K and Das L.M, Bio diesel development and characterization for use as a fuel in CI engine, Transaction of ASME 2001-123, 440- 447 [3] Bari, S., Lim, T.H., Yu, C.W. (2002). Effect of preheating of crude palm oil on injection system. [4] Transestrification of vegetable oils: A review, J.Braz.chem, soc vol 9,no1,199-210 1998. [5] Internal combustion engines by Prof. V Ganesan, chapter-12, heat rejection and cooling page no 363. [6] Adelola and Andrew, International Journal of Basic & Applied Science Vol 1, 02 Oct 2012. [7] Report of the committee on Development of Bio fuels-Planning Commission, Govt of India. [8] Shaik Magbul Hussain, Dr.B. Sudheer Prem Kumar and Dr.K .Vijaya Kumar Reddy, “Biogas –Diesel Dual Fuel Engine Exhaust Gas Emissions”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 3, 2013, pp. 211 - 216, ISSN Print: 0976-6480, ISSN Online: 0976-6499. [9] Mahesh P. Joshi and Dr. Abhay A. Pawar, “Experimental Study of Performance-Emission Characteristics of CI Engine Fuelled with Cotton Seed Oil Methyl Ester Biodiesel and Optimization of Engine Operating Parameters”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 1, 2013, pp. 185 - 202, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.