Numerical Investigation on the Spray Characteristics and Combustion Process in a DI Diesel Engine at Reduced Temperature Combustion Condition

In this paper, reduced temperature combustion has been investigated at high load condition of a direct injection diesel engine. A three dimensional CFD model for flow field, spray, spray-wall interactions, combustion and emissions formation processes have been used to carry out the computations. The combined effect of EGR temperature and EGR rate is analyzed to choose by consideration of engine performance. Then, the effect of injection timing and injection pressure is investigated to the improvement of mixture formation at high engine load condition. It reveals that combustion temperature is dramatically decreased by the increase of cold EGR to 25% rate. This characteristic influences on the increase of the liquid spray penetration and the decrease of indicated mean effective pressure (IMEP) and NOx emission associated with the increase of soot emission. Advance injection timing and high injection pressure together with applying 25% EGR lead to simultaneous reduction in NOx and soot formation compared with the base engine condition.