The effects of pilot injection timing

pilot injection quantity

injection pressure and main injection timing on thepartial premixed charge compression ignition (PPCCI) combustion and emissions of a six cylinders

electronically controlled common rail dimethyl ether (DME) engine were investigated. Results show that

with the advance of the pilot injection timing

the peak cylinder pressure is reduced

and the combustion heat release is changed from the two stage mode to the three stage mode of PPCCI; in addition

NOx emission is reduced

and HC and CO emissions are increased. With the increase of pilot injection quantity

the peak cylinder pressure and the reaction rates of cool flame and thermal flame of the PCCI are increased

HC and CO emissions are also increased

while NOx emission is decreased. With the decrease of injection pressure

the peak value of heat release rate of the PCCI is increased and the start of the main injection diffusion combustion is delayed

the peak heat release rate of the main injection diffusion is significantly reduced; furthermore

NOx emission is significantly decreased while HC and CO emissions are increased dramatically. With the delay of the main injection timing

there is little change in the PCCI

the start of the main injection diffusion combustion is delayed significantly

the peak pressure and the peak heat release rate are decreased; moreover

NOx emission is significantly decreased while HC and CO emissions are increased.