Control strategy of mode transition between low-temperature combustion and conventional combustion in a light-duty diesel engine

Abstract

Combustion mode transition between low temperature combustion (LTC) and conventional combustion was carried out in a light duty diesel engine. The characteristics of combustion mode transition with various operating parameters including exhaust gas recirculation (EGR) rate changing, EGR path length, engine speed and EGR control system were investigated based on the in-cylinder pressure of each cycle. When the combustion mode transition from low-temperature combustion to conventional combustion occurred, indicated mean effective pressure and hydrocarbon emission were rapidly decreased because of non-optimized injection timing and EGR rate. On the other hand, indicated mean effective pressure and hydrocarbon emission were not changed significantly for the mode transition from conventional combustion to low-temperature combustion. Faster mode transition was obtained with shorter exhaust gas recirculation path. The noise level, as represented by the maximum pressure rise rate, and hydrocarbon emission were significantly influenced by residual gas, fuel injection pressure and engine speed. For the smooth mode transition, injection strategy was modulated by cycle-by-cycle. Injection timing and injection quantity were varied and pilot injection strategy was introduced to attenuate rapid changes of indicated mean effective pressure and maximum pressure rise rate.