Mixing-enhanced Combustion in the Circumstances of Diluted Combustion in Direct-injection Diesel Engines 2008-01-0009

Both in conventional diesel combustion and the low temperature combustion represented by PCCI and EGR-diluted combustion, high mixing rate at the whole combustion history is the key to achieve comparative clean and high-efficiency combustion. In this study, a newly developed combustion chamber, vortex-induced combustion chamber which can enhance middle and late cycle combustion is developed based on BUMP combustion chamber investigated in previous study. And then, the combustion and emission characteristics in the circumstances of diluted combustion are studied. For low oxygen concentration cases, heat release rate goes down and combustion efficiency decreases due to decreased mixing efficiency. The results of chamber design indicate complex structure of flow can be realized by special designed chamber geometry. The velocity difference in the interface of the vortexes will benefit to mixing of fuel and air, therefore combustion and emissions. Increase in the late-cycle mixing rate is a promising approach to achieve high efficiency power generation. However, thermal efficiency of low temperature combustion is still lower than that of conventional diesel combustion. The trade-off between emissions and thermal efficiency needs to be controlled carefully.