Abstract
KEYWORDS:
Stratified -charge, GDI engine, LPG engine, two-zone model
ABSTRACT:
Three-zone model was established to calculate the stratified-charge combustion process of LPG direct injection spark ignition engine. This model has been developed on the basis of the two-zone model for gasoline engine by adding diffusion jet model. Thus the local mixture concentration and burning velocity are changed due to time and space in combustion chamber.
The space in combustion chamber can be divided in three parts. The most important region is reaction zone which is limited by two constant mixture fraction curves. The combustion temperature is Tc. The space behind the reaction zone is burned product that is homogeneous with temperature Tp. Before the reaction zone is unburned gas that has nonhomogenous fraction but homogenous temperature Tm. The pressure p is identical in whole of combustion chamber. Thus, there are 4 unknowns (Tc, Tp, Tm, p) at each crankshaft position corresponding to 4 partial derivative equations, these are the first law of thermodynamics applying for the whole combustion chamber, the perfect gas equation applying separately for each zones.
The accuracy of this model is validated by experimental data obtained in LPG direct injection engine.