Investigations on reduction of carbon monoxide -in

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Breathing of CO causes (Khopkar, 1993; Fulekar,. 1999) many .... Chemical pollution- a threat to hu- man life. Indian J of ... S.M. 1993. Environmental Pollution Analysis. ... Vara Prasad, C.M., Murali Krishna, M.V.S. and Prabhakar. Reddy, C.

Eco. Env. & Cons. 16 (3): 2010; pp. (389-393) [email protected] 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. Gupta3 , S. Narasimha Kumar4 and D.N. Reddy 1•2•4·Department of Mechanical

Engineering, Chaitanya Bharathi Institute of Technology, Gandipet, Hyderabad 500 075, A.P., India 3 •4 Department of Mechanical Engineering, J.N. T.U. College of Engineering, Kukatpally, Hyderabad-500072, 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 tempera-

ture 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

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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.PlCO 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- P3CO 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

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Table 1. Data of carbon monoxide (CO) emissions with gasoline operation and gasohol operation Void ratio- 0.7, Speed3000 rpm, Compression ratio- 9:1 Load- Peak Load. Gasoline o:eeration (P) Reduction of CO emissions (%) CO in comparison with Set-1

Set

3.75 2.25 1.5

1 2 3

40 60

CO emissions (%)

3.1 1.74 1.10

Gasohol operation (G) % Reduction of % Reduction of CO in comparison CO in comparison with Set-1 with Set-1 with gasoline operation 45 65

25 59 74

Gasohol- (80% Gasoline+ 20% ethanol by volume); Set.l- Without catalytic converter and without air injection; Set.2With 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 ra-

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