Evaluation of Combustion, Performance and Emission of a Direct Injection Compression Ignition (DICI) Engine Running on a Diesel-Syngas blend

Abstract

The world energy need is primarily met by fossil fuel such as coal and petroleum oil. Theseareutilisedinelectricitygeneration,industrialheatingandtransportation. However,continuedutilisationoffossilfuelssuchascoalisadverselyaffected by their depletion and impact on health and the environment. For coal to be a source of clean energy, it need to be gasified to produce syngas which burns with less harmful emission and pollution than solid coal. Studies on syngas from coal and its use as an alternative to petroleum fuels in internal combustion engines are limited. This is possibly due to the reported low power output of engines fuelled by syngas even though it has proved to have high anti-knock property. The present study is therefore an endeavour to provide a solution to this major drawback of dual fuel engines. This research involved study of the performance and emissions parameters of compression ignition engine fuelled by blends of syngas-diesel. Syngas was used as the primary fuel and diesel as the pilot fuel, both applied in varying proportions. Measurement, test and analyses were conducted by varying syngas volume flowrate, compression ratios, the quantity of diesel supplied, ignition timing, engine load and speed. The air intake system of theenginewasmodifiedtoallowforhomogeneousmixingofairandsyngasbefore supplying the mixture to the combustion chamber. Eddy-current dynamometer, engine data acquisition system were used to carry out measurements and the gas analyser to determine emission in the engine exhaust gases. Tests showed that the best results were: brake specific fuel consumption; 0.75 kg/kwh, brake thermal efficiency; 13.05% and emissions of NOx at 31.8 ppm; CO2, 0.94% and particulate matter; 4.6%. All realised at the compression ratio of 18, advance injection timing of 27.4◦ bTDC, at speed of 1500 rpm and syngas volume flowrate of 100%. These results indicate that the fuel consumption improved almost five folds, power output decreased by about 32% and emissions of NOx, CO2, particulate matter decreased by 24.3%, 26.5% and 32% respectively and HC emission increased by 31.4% from 58.75% when compared to engine when operated on

single fuel mode of diesel. Overall, the study demonstrated that improvement of performance and reduction of emissions of dual-fuel engines through compression ratios and fuel injection timing adjustments are possible.