On unsteady premixed turbulent burning velocity prediction in internal combustion engines

Abstract

In this work, it is shown how to extend the turbulent burning velocity approximation by Peters [N. Peters, Turbulent Combustion, Cambridge University Press, 2000.] for premixed flames in the flamelet regime in order to account for instationary turbulent flame development. Such instationary flame development occurs in spark ignition engines. The burning velocity approximation is embedded into the level set concept [F.A. Williams, in: J. Buckmaster (Ed.), The Mathematics of Combustion, SIAM, Philadelphia, 1985, pp. 97–131; N. Peters, J. Fluid Mech. 384 (1999) 107–132.] for premixed flames that distinguishes between large scale and small scale turbulence. Based on that formulation, a spark ignition criterion for successful ignition of premixed flames is presented. This criterion is based on the competition of premixed turbulent flame propagation and global curvature effects. The turbulent flame brush thickness is employed as a measure for the evolution of the flame. The combustion model is validated against homogeneous charge engine experiments. The results show that initial flame propagation is well predicted, which indicates that the unsteady evolution of the premixed flame is well captured.