Effects of Intake Temperature and Excessive Air Coefficient on Combustion Characteristics and Emissions of HCCI Combustion

The combustion of homogeneous charge compression ignition (HCCI) fuelled with ethanol, methanol and gasoline was achieved on a modified CT2100Q engine by heating the intake air. The effects of intake temperature and mixture concentration on HCCI combustion characteristics and emissions were analyzed in this paper. The results indicate that with the increase of intake temperature, the in-cylinder peak pressure significantly increases and the crank angle corresponding to it gets a visible advance. But for gasoline, the changing trend is a little different. The emissions of HC and CO both decrease and NOx emission for gasoline slightly increases with the increase of intake temperature. As the mixture concentration increases, the in-cylinder peak pressure increases and the crank angle corresponding to it slightly advances. The emissions of HC and CO both increase with the increase of excessive air coefficient (λ). Methanol has the minimum HC emission among the three fuels. NOx emission is very low for the three fuels, and when the excessive air coefficient is larger than 2.5, NOx emission becomes zero.