Effects of compression ratio, blending ratio and engine speed on fuel cost, performance and exhaust emissions of a diesel engine fueled with bio-derived alternative fuels

Abstract

There are numerous studies on the effects of biodiesel-diesel fuel blends on the performance and emission characteristics of diesel engines at constant engine speeds and/or constant compression ratios. However, there is lack of studies on the investigation of the combined effects of engine speed, compression ratio and biodiesel content on both performance and exhaust emissions as well as fuel cost. Thislackhasmotivatedthe present study. Corn oil biodiesel (methyl ester) was produced by the transesterification method. Performance and emission characteristics of a single-cylinder water cooled diesel engine fueled with blends of diesel fuel (DF) and corn oil biodiesel were investigated by changing engine speed (1000–1600 rpm) at each compression ratio (ε = 17, 19 and 21). The test fuels were prepared on volume basis by the blending method and named B20, B40, and B60. Economic analysis was performed for each test fuel at different engine speeds and compression ratios. Firstly, it is found that the use of B20 and B40 at ε = 17 on average leads to an improvement in brake effective power, brake specific energy consumption and brake effective efficiency, compared to DF. However, on average, the use of B20, B40 and B60 at ε = 19 and 21 causes a decrease in brake effective power (by 6.5026 %) and brake effective efficiency (by 8.4650 %) while an increase in brake specific fuel consumption (by 18.2373 %) and brake specific energy consumption (by 9.4340 %), compared to DF. At each compression ratio, the biodiesel-diesel fuel blends producelower CO, HC and smoke but higher CO2and NOx emissions. As compression ratio is increased,brake effective power, brake effective efficiency, NOXand CO2increase while brake specific fuel consumption, brake specific energy consumption, CO, HC and smoke decrease for all test fuels. Moreover, the biodiesel-diesel fuel blends increasefuel cost in the range of 51.2862 %-213.8935 % on average, compared to DF. Finally, it is concluded that the increasing compression ratio is an effective method to reduce emissions and to improve performance.