Theoretical Analysis of Stratified, Two-Phase Wankel Engine Combustion

Abstract A one-dimensional model for the spark ignition two-phase, stratified Wankel engine combustion is presented. The injected liquid fuel is assumed to break up into droplets whose vaporization and motion are computed, together with the changes of the gas phase variables, by solving a coupled system of equations made up of an appropriately simplified form of the spray equation and the conservation equations for the gas phase. The model makes use of a Weber number/Reynolds number correlation for the computation of the initial drop radius, of Stokes' drag equation for the droplet motion, of a Ranz-Marshall type vaporization rate equation for the droplet vaporization, of a one-step second order reaction rate equation for the combustion of the gaseous fuel, of a turbulent diffusivity for heat and mass transfer, and of a McAdams type correlation for the wall heat transfer rate. Results are presented for a specific engine configuration. Although general conclusions cannot be derived, it would appear that th...