Spray vaporization in nonpremixed turbulent combustion modeling: a single droplet model

Abstract The injection of liquid fuel is a common procedure in turbulent combustion devices operating in the nonpremixed regime. Various numerical models may be found in the literature to calculate such turbulent flames, using either Reynolds averaged Navier-Stokes techniques (RANS) or large eddy simulation (LES). The typical inputs of nonpremixed turbulent combustion modeling are the mean and the fluctuations of the mixture fraction. In computational fluid dynamics codes, the mean source of mixture fraction may be provided by Euler-Lagrange spray modeling. However, the sources of fluctuations of mixture fraction due to vaporization require more closures. Direct numerical simulation (DNS) provides a way of estimating these sources and, using DNS of droplets evaporating in a turbulent flow, it is described how they play an important role in the time evolution of fuel/air mixing in a dilute spray. The statistical properties of the spray and of the scalar field are analyzed to propose a single droplet model (SDM) to evaluate these sources. SDM calculates mean values of the Eulerian source of fuel conditioned on the mixture fraction.