Investigations on reduction of carbon monoxide -in spark ignition engine with catalytic converter with gasohol

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1 Eco. Env. & Cons. 16 (3): 2010; pp. ( ) EM International Investigations on reduction of carbon monoxide -in spark ignition engine with catalytic converter with gasohol M.V.S. Murali Krishna\ K. Kishor-2, A.V.S.S.K.S. Gupta 3, S. Narasimha Kumar 4 and D.N. Reddy Department of Mechanical Engineering, Chaitanya Bharathi Institute of Technology, Gandipet, Hyderabad , A.P., India 3 4 Department of Mechanical Engineering, J.N. T.U. College of Engineering, Kukatpally, Hyderabad , A.P., India ABSTRACT Investigations are carried out on a variable compression ratio, spark ignition engine run with gasohol ((20% ethanol and 80% gasoline by volume) for reducing carbon monoxide (CO) emissions in the exhaust with catalytic converter employing manganese ore as catalyst. The influence of parameters like void ratio, air injection, speed, load and temperature of air are studied. A microprocessor based CO analyzer is used for measurement of CO in the exhaust of the engine. The speed, the load and the temperature of air are observed to have strong influence on reduction of CO in the exhaust. Air injection and increase of temperature of air aided further reduction of CO.Gasohol decreased CO emissions considerably when compared to gasoline operation. Key words: Spark ignition engine; Alternate fuel; Ethanol, Emissions, Carbon monoxide, Catalytic converter, Air injection Introduction Carbon monoxide emitted (Usha Madhuri et al., 2003) from the exhaust of spark ignition (SI) engine due to incomplete combustion is highly poisonous pollutant and this pollutant is considerably high during idling and peak load operation of the engine. Breathing of CO causes (Khopkar, 1993; Fulekar, 1999) many health disorders. It also causes detrimental effects (Sharma, 1996) on animal and plant life besides environmental disorders. Hence Government of India has implemented stringent regulations for permissible CO levels in the exhaust of 2/ 4 stroke petrol engines. Of many methods available for reduction of CO, the one employing a catalytic converter (Vara Prasad et al. 1997, Murali Krishna et al. 2000) is found to be more effective in reducing CO emissions. Manganese ore is used as catalyst in the investigations to reduce CO emissions, as it is abundantly available at low price. With the injection of air into the converter and increase of the temperature of the air, the oxidation of CO is expected to improve in the presence of catalyst. In the context of depletion of fossil fuels, increase of pollution levels with fossil fuels and increase of fuel consumption with the increase of vehicle density due to advancement of civilization, the search for alternate and renewable fuels has become pertinent. Ethanol is considered as an alternate fuel for use in spark ignition (SI) engine (Obert, 1973) as the properties of ethanol are very close to those of gasoline. Octane number, which measures the ignition quality of SI engine fuels for ethanol, is higher in comparison with that of gasoline and hence no major modification in the engine is necessary if low quantities of ethanol blended with gasoline are used as a fuel in SI engine. Materials and Methods Fig. 1 shows the experimental set-up employed in the present investigation. It consists of a four- stroke, single-cylinder, water-cooled, petrol engine of brake

2 390 Eco. Env. & Cons. 16 (3) : ts 1. Engine, 2.Eddy current dynamometer, 3. Loading arrangement, 4. Orifice meter, 5. U-tube water monometer, 6. Air box, 7. Fuel tank, 8. Three-way valve, 9. Burette, 10. Exhaust gas temperature indicator, 11 CO analyzer, 12. Air compressor, 13. Outlet jacket water temperature indicator, 14. Outlet jacket water flow meter, 15. Directional valve, 16. Rotometer, 17. Air chamber and 18. Catalyst chamber Fig. 1. Experimental Set Up power 3.0 kw at 3000 rpm. Engine is coupled to an eddy current dynamometer for measuring brake power of engine. There is a facility of varying compression ratio of the engine from 3 to 9 with change of the clearance volume with the adjustment of cylinder head, threaded to the cylinder of the engine. Engine speeds are varied from 2200 to 3000 rpm. A catalytic converter, the details of which are presented in Fig. 2 is fitted to the exhaust pipe of the engine. Provision is made to inject a definite quantity of air into the converter. The converter is filled with catalyst of varying void ratios (void ratio is defined as the volume occupied by the catalyst to that of the catalytic chamber) ranging from 0.1 to 1. The percentage of CO in the exhaust of the engine is measured with Netel Chromatograph CO analyzer. The sets of the exhaust gases are drawn at three locations one, immediately after the exhaust valve in the conventional engine, second, after the catalytic converter, and third with air injection into the converter. The quantity of air drawn from the compressor and injected into the converter is kept constant so that the backpressure do not increase and reverse flow is not created in the converter. There are six sets of the configurations used iri. the investigation for reducing CO in the exhaust of SI engine. i) Set.Pl CO emissions from the engine with pure gasoline as fuel without catalytic converter and air injection. ii) Set.P2- CO emissions from the engine with pure gasoline as fuel with catalytic converter. iii) Set- P3- CO emissions from the engine with pure gasoline as l.air chamber, 2. Inlet for air chamber from the engine, 3. Inlet for air chamber from the compressor, 4. Outlet for air chamber, 5. Catalytic chamber, 6. Outer cylinder 7. Intermediate-cylinder, 8. Inner-cylinder, 9. Outlet for exhaust gases, 10. Provision to depositthe catalyst and 11. Insulation. Fig. 2. Details of catalytic converter fuel with catalytic converter and air injection. iv) Set. Gl-CO emissions from the engine with gasohol as fuel without catalytic converter and without air injection. v) Set.G2-CO emissions from the engine with gasohol with catalytic converter. vi) Set.G3-CO emissions from the engine with blends of gasoline and ethanol as fuel with catalytic converter and air injection. Results and Discussion Fig. 3 presents the variation of CO emissions in the exhaust of the engine for Set. P2 and Set. G2 operation at the peak load operation of the engine at a speed of 3000 rpm with compression ratio of 9 with varying void ratios of catalyst. It can be observed Fig. 3. Variation of CO emissions with void ratio

3 KRISHNA ET AL 391 Table 1. Data of carbon monoxide (CO) emissions with gasoline operation and gasohol operation Void ratio- 0.7, Speed rpm, Compression ratio- 9:1 Load- Peak Load. Set Gasoline o:eeration (P) Gasohol operation (G) CO emissions Reduction of CO emissions % Reduction of % Reduction of (%) CO in comparison (%) CO in comparison CO in comparison with Set-1 with Set-1 with Set-1 with gasoline operation Gasohol- (80% Gasoline+ 20% ethanol by volume); Set.l- Without catalytic converter and without air injection; Set.2- With catalytic converter only; Set.3-With catalytic converter and air injection that the CO emissions reduced considerably with increasing void ratio for both the sets. However, it is clearly established that beyond the void ratio of 0.7, CO reduction is less for both cases due to reduction of surface/volume ratio and increase of backpressure on the engine. At void ratio 0.7, the reduction of CO is higher with gasohol when compared to that of gasoline as fuel-cracking reactions are eliminated with ethanol. Combustion of alcohol produced more water vapor than free carbon atoms as the molecular structure of ethanol contains lower value of the C/H of 0.33 (where C represents number of carbon atoms while H represents number of hydrogen atoms in the composition of the fuel) against 0.44 of gasoline. Fig.4 presents the percentage variation of CO emissions in the exhaust with speed of the engine at the peak load operation with compression ratio of 9 and at void ratio of 0.7 for different configurations of the engine. The reduction of CO increased as speed of the engine increased for all the configurations. Improved combustion with the increase of turbulence was the factor, which reduced CO emissions. It is noticed that at each speed the CO content in the exhaust decreased considerably with the use of converter, the effect being more pronounced with the air injection into the converter. Table 1 presents data of CO emissions with gasoline operation and gasohol operation at void ratio of 0.7, speed 3000rpm compression ratio 9:1 with different sets of the operation. Gasohol operation shows marginally higher percentage reduction of CO with different sets, compared to gasoline operation. Fig. 5 shows the variation of CO emissions in the exhaust with brake mean effective pressure (BMEP) of the engine at a speed of 3000 rpm with compression rai't o-g Ietl'l J..<\-~-. tv-v..se'i P1J... Gt l:_ 1. -.,.:93ii' 0] ti.... Fig. 4. Variation of CO emissions with speed of the engine Fig. 5. Variation of CO emissions with brake mean effective pressure of the engine

4 392 Eco. Env. & Cons. 16 (3): o lo 10 -a:~.,.., M to o 10.Au Bow -~~t Fig. 6. Variation of the CO emissions with air flow rate tio of 9 and at void ratio of 0.7. CO emissions were observed to be increased at part load and at full load and decreased at middle load for all sets. Nedunchezhian (Nedunchezhian et al., 2000) reported the same trend with spark ignition engine with gasoline on the emissions of CO. At the same time it could be noticed that sufficiently large reduction of CO is achieved with the use of converter and air injection further decreased the CO emissions in the exhaust at all loads with all the above sets. Gasohol decreased CO emissions considerably when compared to pure gasoline in all cases of investigations. Fig.6 presents the variation of CO emissions with airflow rate at peak load operation of the engine, at void ratio of 0.7, at speed of 3000 rpm, with compression ratio 9:1 with the sets P~3 and G-3. CO emissions are found to be lower when injected air quantity is 60 1/min for conventional engine with gasoline as fuel, while it is 40 1/min for copper coated engine with gasohol. Fig.7 shows the variation of CO emissions with temperature of injected air at peak load operation of the engine, at void ratio of 0.7, at speed of 3000 rpm and with compression ratio of 9:1 with the sets G-3 and P-3. In the same figure the data of set P-.1 and set G-1 are also. shown for the comparison purpose. When the temperature of air is at 350 C, the percentage of CO in the exhaust of the engine is found to be lower for the set P3, while it was at 370 C for the set G-3. The temperature of exhaust gas is lower with alcohol operation and hence higher temperature is required Fig. 7. Variation of CO emissions with the temperature of air injected for oxidation reaction for alcohol operation when compared to gasoline operation. Conclusions The void ratio of 0.7 is found to be the optimum for both sets P.2 and G.2. CO content decreased with increasing speed in each of the configurations of the converter. Percentage of CO increased at part and peak loads of the engine. Gasohol operation showed higher percentage of reduction of CO in all sets in comparison with pure gasoline operation. Catalytic converter with air injection reduced CO emissions considerably in both cases of gasoline and gasohol operation. Acknowledgments Authors thank authorities of Chaitanya Bharathi Institute of Technology, Hyderabad for facilities provided. The financial assistance of Andhra Pradesh Council of Science and Technology (APCOST), Hyderabad is gratefully acknowledged. References Fulekar, M. H Chemical pollution- a threat to human life. Indian J of Env. Prot. 1(3): Khopkar, S.M Environmental Pollution Analysis. New Age International (P) Ltd, Publishers, New Delhi. Luo, M. F. and Zheng, X.M CO oxidation activity

5 KRISHNA ET AL and TPR characteristics of Ce0 2 -supported manganese oxide catalyst. Indian J. Chern. 38(1): Murali Krishna, M.V.S., Vara Prasad, C.M. and Ch.V.Ramana Reddy Studies on control of carbon monoxide emissions in spark ignition engine using catalytic converter. Ecol., Env.& Conser., 6(4): Nedunchezhian, N. and Dhandapani, S Experimental investigation of cyclic variation of combustion parameters in a catalytically activated two-stroke SI engine combustion chamber. Eng., Today, 2(1): Obert, E.F Internal combustion engines and air pollution, Harper and Raw Publications, New York, Sharma, B.K Engineering Chemistry, Pragathi Prakashan (P) Ltd., Meerut. Usha Madhuri, T., Srinivas, T. and Ramakrishna, K A study on automobile exhaust pollution with regard to carbon monoxide emissions. Nature, Env.& Poll., Tech., 2(4): Vara Prasad, C.M., Murali Krishna, M.V.S. and Prabhakar Reddy, C Reductions of 'CO' in petrol engine exhaust using catalytic converter. Fifteenth National Conference on IC Engines and Combustion. College of Engineering, Gindi, Anna University, Chennai. Proceedings, pp

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