An Effect of Cooled-EGR on Diesel Engine Performance Fueled with Coconut-oil Methyl Ester 2019-32-0618

The purpose of this study is to explore an effect of cooled-EGR on the diesel engine performance fueled with coconut-oil methyl ester (CME). The exhaust gas was cooled by the water at room temperature and was fed to the intake manifold, and the EGR rate was changed from 0 % to 30 % at every 10 %. The engine performances were measured at several EGR rates, fuel injection pressures and timings. Test fuels were CME and commercial diesel fuel. In the case of high EGR rate at which the compression ignition was deteriorated, the ignition timing of CME was always earlier than that of diesel fuel, therefore CME had good ignitability as compared with diesel fuel under EGR application. When the fuel injection pressure was increased at high EGR rate, the ignition delay was improved by the fuel atomization and air-fuel mixing effect. The COV of indicated mean effective pressure was not so influenced by the EGR rate for CME and diesel fuel and the brake thermal efficiency of CME was almost the same as that of diesel fuel at any EGR rates. At high EGR rate, NOx emission remarkably decreased and brake thermal efficiency slightly decreased, and THC, CO and smoke emissions were increased for both fuels. In any EGR rates, THC, CO and smoke emissions of CME was slightly lower than those of diesel fuel. Therefore, NOx emission was could be reduced by the cooled EGR when the CME was used, although CO, THC and smoke emissions increased.