Direct Numerical Simulation of Premixed Turbulent Combustion

Abstract

We consider the Direct Numerical Simulation (DNS) of a premixed flame in a turbulent flow. The combustion takes place in the flamelet regime. In this regime, the combustion takes place in a very thin layer, called the flame front. The position of the flame front is modelled by means of the G-equation, in which the flame front is represented by an isosurface G ₀ of a scalar field G(x, t). The flow is described by the Navier Stokes equations in the low Mach number limit, which allows for the inclusion of expansion effects due to the temperature increase by the combustion. The mean position of the flame is stabilised at a fixed position. This allows us to obtain proper statistics by means of time averaging.

The results show an increase in the turbulent flame speed with increasing turbulent intensity at the position of the flame front, which is in good agreement with experimental and theoretical data. The turbulent flame speed also shows a dependence of the expansion coefficient and increases with higher expansion rates.