Numerical Study on Combustion Process in Three-Dimensional Inhomogeneous Concentration and Temperature Fields of Methane-Air Mixture

Abstract

The spray combustion is applied to various practical combustors such as a diesel engine, a gas turbine, etc. However, the spray combustion is the very complicated, unsteady and inhomogeneous physicochemical phenomenon composed of preheating, evaporation, mixing, ignition, combustion and quenching, etc. Chiu et al. considered the spray combustion field with the concept of group combustion, and proposed that the group combustion can be classified into four modes in terms of group combustion number. In this paper, we examined to improve Chiu's group combustion mode using the numerical analysis on gas phase combustion process in three-dimensional inhomogeneous concentration and temperature fields of methane-air mixture. We arranged many fuel points using random variables instead of fuel droplets, and changed the initial equivalence ratio and fuel point diameter. We obtained the following results; 1) The group combustion is classified into five modes in terms of the initial equivalence ratio and fuel point diameter. 2) The ignition occurs in each fuel point when the mixture gas is lean, while the ignition occurs in the area with fuel point closely spaced when the mixture gas is rich. 3) "The initial equivalence ratio / fuel point diameter" is the appropriate parameter of the group combustion of gas phase.