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Investigations were carried out to evaluate the performance of a low heat rejection (LHR) diesel engine consisting of air gap insulated piston with 3-mm air gap, with superni (an alloy of nickel) crown, air gap insulated liner with superni insert and ceramic coated cylinder head with different operating conditions of crude jatropha oil (CJO) with varied injection timing and injector opening pressure . Performance parameters [brake thermal efficiency, exhaust gas temperature, coolant load and volumetric efficienc and exhaust emissions [smoke and oxides of nitroge were determined at various values of brake mean effective pressure (BMEP). Combustion characteristics [ peak pressure, time of occurrence of peak pressure and maximum rate of pressure ris of the engine were at peak load operation of the engine. Conventional engine (CE) showed deteriorated performance, while LHR engine showed improved performance with vegetable operation at recommended injection timing and pressure. The performance of both versions of the engine improved with advanced injection timing and higher injector opening pressure when compared with CE with pure diesel operation. Relatively, peak brake thermal efficiency increased by 14%, smoke levels decreased by 27% and NOx levels increased by 49% with vegetable oil operation on LHR engine at its optimum injection timing, when compared with pure diesel operation on CE at manufacturers recommended injection timing.

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Investigations were carried out to evaluate the performance of two stroke and four stroke of single cylinder, spark ignition (SI) engines having copper coated engine [CCE, copper-(thickness, 300 μ)] coated on piston crown and inner side of cylinder head] provided with catalytic converter with sponge iron as catalyst with methanol blended gasoline (80% gasoline and 20% methanol by volume) and compared with conventional engine (CE) with pure gasoline operation. Performance parameters — brake thermal efficiency (BTE), exhaust gas temperature (EGT), volumetric efficiency and exhaust emissions of carbon monoxide (CO) and un-burnt hydrocarbon (UBHC) were determined with different values of brake mean effective pressure (BMEP) of the engine and compared with one over the other of two stroke and four stroke SI engine with different versions of the engine. Formaldehyde and acetaldehyde emissions were measured by 2, 4 dinitrophenyl hydrazine (2,4 DNPH) method at peak load operation of CE and CCE of two-stroke and four-stroke SI engine. The engine was provided with catalytic converter with sponge iron as catalyst. There was provision for injection of air into the catalytic converter. Brake thermal efficiency increased with methanol blended gasoline with both versions of the engine. CCE showed improvement in the performance when compared with CE with both test fuels. Four-stroke engine decreased exhaust emissions effectively in comparison with two-stroke engine with both versions of the engine. Catalytic converter with air injection significantly reduced exhaust emissions with different test fuels on both configurations of the engine.

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