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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.

Homogeneous charge compression ignition (HCCI) combustion is a hybrid concept of compression and spark ignition combustions. It is a promised solution to environmental and fuel economy concerns for internal combustion engines. In this mode of combustion, a lean premixed charge combusts simultaneously from multiple sites. Utilizing very lean mixtures, and the lack of any obvious flame propagation, considerably reduces in-cylinder NOx formation. In order to make the HCCI engine a feasible alternative to the SI and CI engines, several items must be elucidated. Control of the combustion timing is one of the most important of these items to be resolved. Combustion timing should be controlled in order that heat is released at the best time in the engine cycle. In this study, a Waukesha CFR single cylinder research engine with variable EGR was used to be operated in HCCI combustion mode fueled by natural gas and n-heptane.