On the Deposit-Induced Surface Ignition of Internal Combustion Engines

Abstract

The problem of deposit-induced surface ignition in internal combustion engines is studied analytically with perturbative method with respect to reaction term, to predict the quantitative criterion of ignition of the mixture. As the fuel has a higher concentration, a larger heat of reaction, a larger coefficient of reaction rate, or a smaller activation energy, the ignition resistance becomes greater. The large heat capacity of the mixture, the low temperature of inlet air, the low temperature at the surface of burning deposit and the high engine speed decreas the tendency towards the surface ignition. The combustion temperature of deposit is proportional to the square root of the ratio of the concentration diffusivity of oxygen to the thermal diffusivity of the material of deposit. In the case of turbulent motions of the mixture, the use of turbulent diffusivities could lead to a similar conclusion. As for the effect of engine speed, the heat associated with viscous motion of the mixture must be taken into consideration.