RESUMO
Diesel engines are playing a vital responsibility in the field of automobile, agriculture, construction, and power generation. In the present world, much research is going on in the field of renewable energy to replace conventional sources of energy. But it is not very easy to replace diesel engines with other sources due to the better power output and reliability. The emissions from CI engines are very harmful for human health and for the environment. The major emissions are smoke and NOx which need to be controlled in an effective manner. In this work, direct injection variable compression ratio CI engine was used in experimental investigations for determining the combustion characteristics for D-MXEE-NM blends at different compression ratios. By performance analysis and exhaust emission of engine at peak load, D-MXEE5-NM2.5 (diesel 92.5%, 2-methoxyethyl ether 5%, and nitromethane 2.5%) blend was identified as best blend among all tested fuel blends and pure diesel at normal compression ratio (17.5). Further, all considered fuels with different CR values at peak load were ranked by Entropy-VIKOR method. From the analysis, D-MXEE5-NM2.5 at CR 19.5 was found as best fuel blend (ranked first) among all fuel blends and different compression ratios considered with same experimental conditions. By comparison of best fuel blend D-MXEE5-NM2.5 (at advanced compression ratio 19.5) with diesel (at standard CR 17.5), emission decline (HC 66.66%, CO 70.00%, and smoke 16.09%) and performance improvement (decrement in BSFC 7.07% and increment in BTE 4.41%) were obtained significantly at peak load. However, negligible increment in NOx (3.58%) was observed.