Effects of Equivalence Ratio and Temperature of CNG Premixture on Knock Limit in a Dual Fueled Diesel Engine

Homogeneously charged natural gas was burned in a diesel engine assisted by a small amount of gas oil injection. The effects of the equivalence ratio of natural gas, the intake temperature and the EGR rate on ignition of gas oil, the burning rate of natural gas and the knock limit were clarified experimentally. As results, a marked improvement in the trade-off between smoke and NOx was obtained maintaining a high thermal efficiency by a combination between the natural gas charge rate, the EGR rate, the intake preheating and the nozzle orifice size suitable at each engine load.