Stochastic Model for Flame Propagation at Lean Ignition Limit of Spark Ignition Engines

Abstract

A phenomenological model simulating stratification of temperature and species concentration was developed to predict engine misfire. The model incorporates the coalescence dispersion model for finite rate mixing and the mass entrainment model for flame propagation. The fuel mixture in the combustion chamber is divided into equal mass particles, each having a thermodynamic state. A first order chemical rate reaction for the combustion of propane in air is used. A set of ordinary differential equations for the evolution of temperature and species concentration for each particle is formulated. A predictor corrector method was developed to solve the system of equations.

The model was tested extensively for the ignition limit. The effect of turbulence intensity, intake temperature, equivalence ratio and spark advance were investigated. An optimum level of turbulence intensity that enhances burn rate was observed. Increasing the intake temperature allows a higher optimum value of turbulence. Varying the spark advance combines the effect of intake temperature and turbulence intensity. When the spark advance is retarded, leaner mixture can be used.