An Eulerian-Eulerian-Lagrangian modeling of two-phase combustion

In simulating two-phase combustion, most Reynolds-averaged Navier-Stokes (RANS) simulation and large-eddy simulation (LES) used Eulerian-Lagrangian (E-L) modeling (Eulerian treatment of gas phase and Lagrangian treatment of particles/droplets) which needs much more computational time than the Eulerian-Eulerian (E-E) or two-fluid modeling. However, in the E-E modeling, the problem of how to reduce the computation time for poly-dispersed particles is encountered . To solve this problem, the present author proposed an Eulerian-Eulerian-Lagrangian (E-E-L) modeling of two-phase combustion for both RANS modeling and LES. The E-E-L modeling is an Eulerian treatment of gas phase and a combined Eulerian-Lagrangian treatment of particles/droplets, in which the particle velocity and concentration are solved by Eulerian modeling, and particle temperature and mass change due to reaction are solved by Lagrangian modeling. In this paper, a review is given for an E-E-L modeling of coal combustion, its application in RANS simulation and its possible application in LES. For E-E-L LES, an energy equation model of two-phase sub-grid scale (SGS) stresses accounting for the interaction between two-phase SGS stresses is suggested, and a second-order moment SGS (SOM-SGS) turbulence-chemistry model is adopted to simulate gas-phase reaction in two-phase combustion. These SGS models were separately assessed by comparison with experiments.{GRAPHIACAL ABSTRACT}