Effects of operating parameters on mode transition between low-temperature combustion and conventional combustion in a light-duty diesel engine

An experimental study on the mode transition between low-temperature combustion and conventional combustion was carried out in a light-duty diesel engine. The characteristics of combustion mode transition with various operating parameters, including rate of exhaust gas recirculation change, residual gas, exhaust gas recirculation path length, fuel injection pressure and engine speed, were analysed based on the in-cylinder pressure and hydrocarbon emission of each cycle. In the case of mode transition from low-temperature combustion to conventional combustion, rapid decreases in indicated mean effective pressure and hydrocarbon emission occurred due to the improper injection timing and the decrease of the exhaust gas recirculation rate. On the other hand, indicated mean effective pressure and hydrocarbon emission changed slowly during mode transition from conventional combustion to low-temperature combustion owing to the thermal effect of hot residual gas from conventional combustion. Faster mode transition could be achieved by the use of a shorter exhaust gas recirculation path. Although the trends of mode transition in terms of indicated mean effective pressure were similar, the noise levels, as represented by the maximum pressure rise rate, and hydrocarbon emissions were significantly affected by residual gas, fuel injection pressure and engine speed. In addition, smooth combustion mode transition could be achieved by cycle-by-cycle injection modulation without rapid changes of indicated mean effective pressure and maximum pressure rise rate.