Dynamometer engine tests at steady-state conditions and a wear characteristics study were carried out on an indirect-injection diesel engine with palm oil diesel (POD) and its emulsions. The POD fuel was obtained in commercial form, and its emulsions were created by mixing POD fuel to contain 5 and 10% of water by volume. Variations in the engine's performance characteristics were determined from the results of steady-state tests carried out at fifteen selected torque-speed matrix points of the engine's performance map. The wear characteristics tests were performed by running the engine at half throttle setting for twenty hours for each fuel system. Then a desk-top comparison study was performed between the baseline fuel system of ordinary diesel (OD), POD, and its emulsions. Promising results have been obtained. Neither the lower cetane number of POD fuel nor its emulsification with water presented obstacles to the operation of the diesel engine during a series of steady-state engine tests and the twenty-hour endurance tests. Engine performance and fuel consumption for POD and its emulsions are comparable with those of OD fuel. Accumulations of wear metal debris in crank-case oil samples were lower with POD and its emulsions than with baseline OD fuel.JAOCS 72, 905-909 (1995).

The major drawback of vegetable oil fuels is their high viscosity. Various conventional approaches to reducing the viscosity of vegetable oils are studied theoretically and experimentally. An attempt to reduce the viscosity of the palm oil methyl esters (POME) by preheating the fuel was performed and a comparison on the basis of its projected chance of leading to ‘diesel-like’ combustion was also carried out with conventional diesel fuel. It was observed that by preheating the POME fuel above the conventional temperature, the engine performance, especially the brake power output and the exhaust emissions characteristics, is improved significantly, approaching diesellike' performance. This is mainly attributed to the fact that as the fuel is preheated the viscosity is reduced close to ordinary diesel (OD) fuel. This will result in improved spray and atomization characteristics. Torque, brake power, specific fuel consumption, exhaust emissions and brake thermal efficiencies were measured and calculated. The potential for improved engine performance and reduction in emissions levels was demonstrated.

Results of exhaust emissions and lube oil analysis of a diesel engine fuelled with Malaysian palm oil diesel (POD or palm oil methyl esters) and ordinary diesel (OD) emulsions containing 5 and 10 per cent of water by volume are compared with those obtained when 100 per cent POD and OD fuel were used. Very promising results have been obtained. Neither the lower cetane number of POD fuel nor its emulsification with water presented any obstacle to the operation of a diesel engine during steady state engine tests and the 20 hour endurance tests. Polymerization and carbon deposits on fuel injector nozzles were monitored. Engine performance and fuel consumption for POD and its emulsions are comparable with those of OD fuel. Accumulations of wear metal debris in crank-case oil samples were lower with POD and emulsified fuels compared with baseline OD fuel. Both OD and POD emulsions with 10 per cent water by volume show a promising tendency for wear resistance. The exhaust emissions for POD and emulsified fuels are found to be much cleaner, containing less CO, CO2, HC, NOx, SOx and smoke level. Power output is slightly reduced when using POD and emulsified fuels.

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