In order to minimize hydrocarbon mass emissions for a spark ignited engine-catalyst system during the cold start condition in which most of the hydrocarbon mass emissions occur, we focus on the acceleration of hydrocarbon oxidation reactions in a gas phase and a catalyst.
In the present study, effects of the in-cylinder gas flow motion and the equivalence ratio on the reduction of cold hydrocarbon mass emissions have been widely investigated using three spark ignited engine systems. It is suggested that a swirl of intake gas flow motion and the lowering of equivalence ratio have a large effect on the improvement in in-cylinder oxidation reactivity by the mixing of unburned hydrocarbons with high temperature burned gas and also in catalytic reactivity by increasing the engine-out oxygen concentration. The cold hydrocarbon mass emissions under the developed engine control with a swirl and an equivalence ratio of 0.9 is about 30% lower than these under the conventional engine control with none of active gas flow motion and an equivalence ratio of 1.0.
�@