DOI: 10.1615/ICHMT.2008.CHT
ISBN Print: 978-1-56700-253-9
ISSN: 2578-5486
ESTIMATE OF THE SUBGRID VARIANCE OF THE MIXTURE FRACTION IN SPRAY TURBULENT COMBUSTION
RÉSUMÉ
Many industrial devices operate with turbulent combustion of an evaporating liquid phase. Progress in the design of such systems strongly relies on the accurate control of whole of the processes, starting from the injection of liquid fuel, evaporation and combustion. Depending on the chamber's geometry, the spray injection conditions and the mixing phenomena, various combustion regimes and flame structures may be observed, starting from premixed flames up to diffusion flames. However, partially premixed combustion is generally observed because of the triple interactions between spray, turbulence and combustion. The modeling of such chambers, involving the combustion of a two-phase flow or of a gaseous mixture released by the evaporation of a spray, is of primary importance to improve the output of the device considered and to predict pollutant formation while still maintaining a reasonable development cost. In this work we study the evolution of subgrid variance of mixture fraction and progress variable for the simulation of a spray turbulent combustion. We analyze the various terms of the equations, including the mass source terms due to the droplets evaporation. The coupling between the mixture fraction and progress variable equations and the propagating front flame is then analyzed. To do so a DNS of evaporating spray was carried out. The carrier phase is fully resolved; on the other hand a Lagrangian model was used for the dispersed phase.