Andhra Pradesh , India 2 Associate Professor, Department of Mechanical Engineering, National Institute of Technology, Warangal

Transcription

1 Research Article PERFORMANCE CHARACTERISTICS OF A DIESEL ENGINE OPERATED ON BIODIESEL WITH EXHAUST GAS RECIRCULATION Donepudi Jagadish, 1 * Dr.Puli Ravi Kumar 2, Dr.K.Madhu Murthy 3 Address for Correspondence 1 Research Scholar, Department of Mechanical Engineering, National Institute of Technology, Warangal Andhra Pradesh , India 2 Associate Professor, Department of Mechanical Engineering, National Institute of Technology, Warangal Andhra Pradesh , India 3 Professor, Department of Mechanical Engineering, National Institute of Technology, Warangal Andhra Pradesh , India jagadish.donepudi@gmail.com ABSTRACT Biodiesel has been used as a renewable and potential fuel in diesel engines. Review of literature suggests biodiesel as a good alternate to diesel suffering with a drawback of an increase in nitrous oxide (NOx) emissions because biodiesel contains fuel nitrogen that leads to formation of NO, NO 2 during combustion. The present work is to study the effect of Exhaust Gas Recirculation (EGR) on the performance and emissions of a single cylinder naturally aspirated constant speed diesel engine. At first the performance of the engine was evaluated with the selected biodiesel (palm Stearin methyl ester). The EGR rate was varied between 0-20 percent. The emissions species measured were nitric oxide (NO), unburnt hydrocarbons (UHC), carbon monoxide (CO) etc. The results showed that EGR would be one option to reduce the nitrous oxide emissions, but with a rise in EGR rate the CO, UHC concentrations in the engine exhaust are increased. Better trade-off among HC, CO and NOx has been found with EGR rate of % with little loss in fuel economy. KEYWORDS Biodiesel, EGR, Nitrous Oxides 1. INTRODUCTION Energy security has become the primary concern many countries. The sustainable development of a country depends on the exploration of energy sources that are renewable and simple in implementation of these sources to mankind. Lots of research is needed to explore renewable energy sources, particularly bioenergy sources for transportation and power generation. They can compete better in the future along with conventional fuels and can reduce the dependency on fossil fuels. Vegetable oils have been the option for internal combustion engines since the time of Second World War. There have been many progressive investigations throughout the world for the usage of vegetable oil fuels. The modified form of vegetable oil that is biodiesel, has significantly achieved success for replacing diesel to some extent. Biodiesel is a renewable fuel substitute the term referred to ethyl or methyl esters that are produced from vegetable oils or animal fats. The potential advantage of biodiesel is that it is renewable. Its use would reduce dependence on the foreign petroleum. Many vegetable oils have been in use in different countries as raw materials for biodiesel production owing to its availability [1-8]. Soybean oil is commonly used in United States and rapeseed oil is used in many European countries for biodiesel production, whereas, coconut oil and palm oils are used in Malaysia for biodiesel production. Jatropha is the common feed stock used for making biodiesel in India and Africa. Transesterfication is the processes that convert the vegetable oils to correspond ethyl or methyl esters. Transesterfication referred to conversion of an organic acid ester into another ester of the same acid, this requires at least of three moles of alcohol per mole of vegetable oil to yield three moles of fatty acid ester and one mole of glycerol. The alcohols most frequently tried as reactants in the transesterfication process are ethanol, methanol and butanol. The catalysts used, are NaOH, NaOCH 3, and KOH etc. The selection of catalyst depends on molar ratio of the reactants and the presence of free fatty acids [9]. Based on previous studies some common facts about the usage of biodiesel can be made. Almost all the previous works showed that NOx emissions increased with biodiesel operation. And a rise in fuel consumption is noticed in majority of the cases, whereas hydrocarbon emissions, smoke and particulate matter were decreased. The engine

2 pretreatment can be the best method to reduce NOx emissions. The pre-treatment methods like Exhaust Gas Recirculation, Humid Air Induction, Water Injection in the cylinder can be effective methods to reduce the NOx emissions. The present study investigates the effect of EGR on engine performance. Residual gas contributions to the combustion process have been well established and, in many applications, manipulated for providing some engine-out emission control and altering overall engine performance. Exhaust gas recirculation (EGR) is a portion of spent exhaust that is reintroduced into the fresh intake charge upstream of the cylinder.(egr) quite popular in recent years as a successful means for reducing NO x emissions from both spark and compression ignition engines. Introduction of cooled exhaust gas into the combustion chamber results in dilution of the air charge by replacing O 2 with the non-reacting CO 2. Consequently, both the specific heat capacity of the in-cylinder gas mixture and the peak flame temperatures of the cycle are reduced. As a result, NO X emissions are reduced too, aided by the lower oxygen availability. However, smoke emissions increase since the soot oxidation process is diminished; the same holds true for HC and CO emissions. Dilution of intake air with exhaust gas increases the heat capacity of the charge, reducing the combustion temperature. Lower temperatures are also experienced in the combustion since the energy required heating the diluents. Many authors have reported the EGR can be effective technique in reducing NOx emissions [10-18]. 2. EXPERIMENTAL SETUP A naturally aspirated single cylinder diesel engine with D.C shunt dynamometer is selected for experimentation. Modifications are made to the original engine set up to work with option EGR. A heat exchanger is used to cool the exhaust gas while entering the inlet to maintain constant temperature (34 0 C) throughout, for all the EGR rates. Venturi pipe set up is made to create suction for the exhaust gas into the inlet pipe. Rotameters are used to measure the volume flow rates of inlet charge as well as exhaust gas to be re circulated. Table I gives the details of the experimental setup. Five gas analyser with make KANE-MAY used for the measurement of amounts of exhaust emissions. Smoke opacity has been measured with the help of AVL smoke meter. The emission concentrations are measured after engine has attained steady state for each set of readings. A schematic of experimental set up is shown in figure 1. Figure 1: Schematic of Experimental Setup

3 TABLE I: DETAILS OF ENGINE Engine manufacturer Engine Type Cooling Dynamometer Rated Power Bore/Stroke Kirloskar Oil Engines Limited, India Single cylinder, 4-stroke, naturally aspirated, direct injection, compression Ignition Water Cooled Eddy current type 3.7 kw at 1500 rpm 80/110 (mm) Compression ratio 16.5 Start of Fuel 26 0 BTDC Injection Nozzle Opening Pressure Cubic Capacity 180 bar Liters 3. EXPERIMENTAL METHODOLOGY Transesterfication of crude palm stearin is carried out to make palm stearin methyl ester. The catalyst used for the reaction is NaOH. The biodiesel is tested for the properties. Table II gives the fuel properties of palm stearin methyl ester. Biodiesel was blended with diesel on volume basis. The engine was then tested for performance and emissions with the selected fuel blends. Engine cooling water jacket temperature was kept constant at 55 0 C during entire engine operation and engine is maintained at constant speed of the engine 1500 rpm. Inlet air temperature is maintained constant at 34 0 C during all the periods of operation. The tests were conducted on the engine without EGR and with EGR and the performance parameters like BSFC, BTE and in-cylinder pressure tracks are compared. Different EGR rates are obtained by opening the valve of exhaust towards the heat exchanger and partially closing the exhaust valve. EGR rate is calculated by following expression (1). Equation (2) calculates EGR rate based on CO 2 concentration in the ambient air, exhaust gas and inlet charge [11]. It is observed that with increased EGR at naturally aspirated conditions there is slowing down of the combustion process due less amount of oxygen. From the figure 1 it can be observed that there are two openings for the inlet air to enter engine, as shown in the figure 1 as points 1 and 2.During normal operating conditions the engine sucks the air from both the openings. TABLE II: FUEL PROPERTIES OF DIESEL AND PSME Property Diesel PSME Density (kg/m 3 ) Kinematic Viscosity (cst) Heating Value(kJ/kg) 42,500 39,900 Cloud Point, 0 C 3 16 Pour Point, 0 C Flash Point, 0 C This provides smooth action of the engine to suck sufficient quantity of air. During EGR operation the opening 2 is closed so that fresh air and exhaust gas mixes in the venturi tube and enters the engine cylinder. Closing of valve 2 creates more suction near the venturi so that exhaust gas can be collected and mixed thoroughly with air.... (1)... (2) RESULTS AND DISCUSSION The variation of brake specific fuel consumption (BSFC) with load is shown in figure 2. Figure 2: Variation of BSFC versus load percentage for biodiesel-diesel blends Little amounts of biodiesel in diesel resulted in reduction of BSFC values, as B10, B20 showed fewer values of BSFC in comparison to diesel, and B100 shown higher values than that of diesel. The reason for more fuel consumption for pure biodiesel can be because of its lower heating value and higher viscosity. Brake thermal efficiency graph is shown in

4 figure 3. There is a rise in thermal efficiency with B10, B20 when compared with pure diesel. B100 showed little lower values of BTE in comparison to diesel. BSFC variation with EGR rate at full load is shown in figure 4. With the rise in EGR rate there is, rise specific fuel consumption this is severe for higher EGR rates i.e. more than 20%. The engine was run with EGR at the cost of little fuel loss. quantity of nitrogen present in the fuel. Figure 5 gives the variation of NO with load. It is evident that as the load increases NO emissions increased, due to rise in temperature leads to more NO formation. Figure 3: BTE versus Load percentage for biodiesel-diesel blends Figure 5: NO emissions versus Load percentage The quantity of NO emissions is more with B100, and less for B10, B20 in the decreasing when compared with diesel. Higher amounts are generally observed with pure biodiesel, it would be severe for high speed engines. NOx emissions versus EGR rate at full load and half load on the engine is shown in figure 6 and 7. Figure 4: BSFC with different EGR rates at Full load ENGINE EMISSIONS Nitrous Oxides Nitrous oxide formation is a temperature dependant phenomenon along with residence time of fuel and air. Biodiesel combustion emits more NOx in comparison to diesel. The reason can be due to Figure 6: Variation of NO emissions with EGR rate The quantities of NO are considerably reduced with EGR rate. For 10% EGR rate the observed reduction of NOx emissions by %, %, 7.57% and13.18% with rise in fuel consumptions by 8.88 %, %, 37.51% and 27.62% for diesel, B10, B20

5 and B100 respectively when compared with no EGR as shown in figure 7. Carbon monoxides The nature of variation of Carbon monoxide with load is shown in figure 9. At part loads the engine is operated at higher air fuel ratios, these lean mixtures left unburnt leads to higher CO emissions. At higher loads rich mixtures leads to increase in CO formation. The effect of exhaust gas recirculation on CO emissions is shown in figure 10. CO emissions increases with EGR rate at a given load of engine operation. Figure 7: Variation of NO emissions with EGR rate The rise in fuel consumption values are not much high with 15 % EGR in comparison to 10% EGR. 15% EGR can be suggested to have more reduction in NOx. The best EGR rate can be selected keeping in consideration to UHC and fuel consumption values. Unburnt Hydrocarbons It was observed that as EGR rate increases a rise UHC emission occurred in the exhaust.uhc emissions are lower for biodiesel diesel blends and with pure biodiesel the quantities are much reduced in comparison to diesel for all the loads of engine operation. Effect of EGR is to increase the HC emissions in the exhaust. Pure diesel observed to be giving higher UHC emissions with EGR rate in comparison to biodiesel. Figure 9: Carbon monoxide emissions versus load percentage Figure 8: Variation of HC emissions with EGR rate Figure 10: Carbon monoxide emissions versus load percentage with different EGR rates Smoke Opacity Smoke opacity values are reduced for B10, B20 and B100 in comparison to pure diesel under normal working conditions of the engine, however the effect of EGR is to increase the smoke in the exhaust. With EGR rate there is a rise in smoke opacity values of

6 the exhaust. As the PM emissions are directly linked with smoke formation, it can be attributed that PM emissions are more with EGR. Smoke opacity variation with EGR at a given load is shown in figure 11. Figure 11: Smoke Opacity values versus EGR rate Exhaust Gas Temperature The temperature has the effect on engine emissions formation. The exhaust gas temperature can be useful in analyzing the genesis of combustion. Exhaust gas temperature versus EGR rate at full load is shown in figure 12. Temperatures generally increase with load, however with the rise in EGR rate the temperature values are decreased showing the effects of charge dilution. Figure 12: Exhaust gas temperature versus EGR rate for biodiesel-diesel blends CONCLUSIONS 1. Brake Specific fuel consumption increases for pure biodiesel, and decreased for B10, B20 in comparison to diesel. The main cause of the increase in BSFC values for pure biodiesel its high value of viscosity when compared with diesel. 2. Effect of EGR is to increase the fuel consumption of the engine. Unburnt hydrocarbon emissions seem to reduce with biodiesel-diesel blends and with pure biodiesel, however with EGR the hydrocarbon emissions increased. With increase in EGR rate the carbon monoxide emissions also increased. 3. Nitrous oxide emissions are considerably reduced with the rise in EGR rate. When the engine is operated with biodiesel EGR would be best pre treatment method to reduce the NOx emissions at the cost of little fuel penalty. 4. Smoke opacity increases with EGR rate this is indication of an increase in soot and PM emissions. Exhaust gas temperature reduces with EGR rate because of charge dilution that causes less oxidation of the charge leads to lower combustion temperatures % would be the best EGR rate for the selected engine with consideration of trade-off between NOx and HC emissions and lower fuel penalty for the engine operation. ACKNOWLEDGEMENT The authors are highly grateful to the staff at I.C.Engines laboratory department of mechanical engineering, NITW and department of chemical engineering, NITW for providing the test facilities. REFERENCES [1] Ma.F., and Hanna,M.A., 1999, Biodiesel production: a review, Journal of Bioresource Technology, vol.70, pp [2] Ramadhas,A.S., Jayaraj,S., and Muraleedharan.C., 2005, Biodiesel production from high FFA rubber seed oil, Journal of Fuel,vol. 84, pp [3] Fukud,H., Kondo,A., and Noda,H., 2001, Biodiesel fuel production by transesterfication of oils, Journal of Bioscience and Bioengineering, vol.92,pp [4] Tiwari,A.K., Kumar,A., and Raheman,H., 2007, Biodiesel production from jatropha oil (Jatropha curcas) with high free fatty acids: an optimized process, Journal of Biomass and Bioenergy,vol.31,pp [5] Ghadge,S.V., and Raheman,H., 2005, Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids, Journal of Biomass and Bioenergy, vol.28,pp [6] Karmee,S.K., and Chadha,A., 2005, Preparation of biodiesel from crude oil of Pongamia pinnata, Journal of Bioresource Technology,vol. 96,pp

7 [7] Wang,Y., Ou,S., Liu,P., and Zhang,Z., 2007, Preparation of biodiesel from waste cooking oil via two-step catalyzed process, Journal of Energy Conservation Management, vol. 48,pp [8] Agrawal,A.K., 2007, Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engine, Progress in Energy and Combustion Science, vol.33, pp [9] Sharma,Y.C., Singh,B., and Upadhyay,S.N., 2007, Advancements in development and characterization of biodiesel: A review, Journal of Fuel, vol.87, pp , [10] Hribernik,A., and Samec,N., 2004, Effect of Exhaust Gas Recirculation on Diesel Combustion, Journal KONES Internal Combustion,Engines,vol.11,No.1-2, [11] Agrawal,A.K., Singh,S., Sinha,S., and Shukla,M.K., 2004, Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines, Sadhana, vol.29, Part 3, pp [12] Mahla,S.K., Das,L.M., and Babu,M.K.G., Effect of cooled EGR on performance and exhaust emission characteristics of biodiesel fuelled engine, Proceedings of the Third International Conference on Thermal Engineering: Theory and Applications, Amman, Jordan, [13] Sasaki,M., Kishi,Y., Hyuga,T., Okazaki,K., Tanaka,M., and Kurihara,I., 1997, Effect of EGR on Diesel Engine Oil, and its Counter measures, SAE Paper No [14] Pradeep,V., and Sharma,R.P., Use of Hot EGR for NOx control in a compression ignition engine fuelled with biodiesel from Jatropha oil, Journal of Renewable Energy, vol.32, pp , [15] Wagner,R.M., Green,J.B., Storey,J.M., and Daw,C.S., Extending Exhaust Gas Recirculation Limits in Diesel Engines, Oak Ridge National, Laboratory,TN. Paper. No gov/~webworks/cpr/pres/106938_.pdf [16] Kreso,A.M., Johnson,J.H., Gratz,L.D., Bagley,S.T., and Leddy,D,G.,1988, A Study of the Effects of Exhaust Gas Recirculation on Heavy Duty Diesel Engine Emissions, SAE Paper No [17] Simoson,C., and Wagner,J., 2008, Effect of Cooled EGR on Small Displacement Diesel Engine: A Reduced Order Dynamic Modeling and Experimental Study, ASME Journal of Energy Resource and Technology, vol.130, pp [18] Saravanan.N., Nagarajan,G., Kalaiselvan,K.M., and Dhanasekaran,C., 2008, An experimental Investigation of hydrogen as dual fuel for diesel engine system with Exhaust Gas Recirculation Technique, Renewable Energy, vol.33, pp