A Numerical Model for the Propagation of Partially-Premixed Gas Flames at Low-Mach Number

This paper describes an activity devoted to the study of the dynamics of the propagation of ames through gas mixtures initiated by localised ignition sources with reference to the development of a mathematical model and a numerical method specially devised to compute low Mach number situations The work is based on a primitive variable pseudo-compressible ow approach with a projection method to derive an elliptic equation for the perturbation pressure and is meant to be applicable even in presence of strong variations of the properties of the medium including density due to temperature and species variations Finite-rate combustion chemistry is taken into account The numerical solution of the model equations is conducted by means of an explicit formulation for the time-dependent balance equations and a direct band-matrix LU solver for the pressure elliptic equation The method proves very eective in that stability limitations are not tighter than those suggested by the request of a satisfactory description of these inherently transient phenomena. To illustrate the methodology transients of laminar methaneair ames were computed from the ignition of initial partially and fullypremixed conditions followed by the propagation of a flame front throughout the open end of a cylindrical pipe In the cases discussed the results provide interesting observations of the interaction of the flow with combustion.