Abstract
HCCI combustion characteristics of mixed fuels with different oxidation mechanisms, toluene/DME, were experimentally and numerically analyzed. Engine test shows that the operating range of toluene/DME HCCI expands to higher load ψ0.77 in total equivalence ratio and BMEP of 0.59MPa, when DME quantity is kept to ψ=0.1, the minimum requirements for ignition. An elementally reaction model for toluene/DME oxidation was developed based on Emdee's toluene oxidation scheme and Curran's DME2000 scheme in order to investigate the influence of coexisting other components with different oxidation mechanisms on reaction process. Numerical analysis shows that toluene starts to be oxidized at a low temperature which single toluene would not react, and in this temperature region toluene oxidation is totally controlled by OH supplied from DME low temperature mechanism. The subsequent excursive hot fame reaction is lowered because toluene oxidation proceeds in stages depending on a temperature rise.
