Effects of air-fuel ratio on combustion and emissions of engine fueled with diesel/propane blends

The effects of air-fuel ratio on the combustion and emissions of a single-cylinder direct injection diesel engine fueled with diesel fuel and diesel/propane blends were investigated. The results show that the combustion duration decreases with the increase of air-fuel ratio and propane proportion; the peak cylinder pressure decreases with the increase of air-fuel ratio and increases with the increase of propane proportion, NO_x and smoke emissions decrease with the increase of air-fuel ratio, HC emission increases greatly with the decrease of air-fuel ratio at smaller air-fuel ratio, while it increases with the increase of air-fuel ratio at larger air-fuel ratio; CO emission increases with the decrease of air-fuel ratio at smaller air-fuel ratio, and it almost keeps constant at larger air-fuel ratio; CO, HC and smoke emissions can be reduced simultaneously, but NO_x emission increases when the engine is fueled with diesel/propane blend.