Large Eddy Simulation of turbulent reacting flows with conjugate heat transfer and radiative heat transfer

Abstract

Large Eddy Simulation (LES) is now an attractive and widely used model for predicting turbulent combustion that finds increasing use in studies of IC-engines, gas turbines, and dual-mode ramjet engines as well as in other applications. Several parameters, e.g. which subgrid turbulence model, reaction mechanism, and filtered reaction-rate model is used, determines the accuracy and robustness of the LES model, together with the choice of numerical methods and grids. Extensive studies are ongoing to further elucidate these issues, and to develop more accurate and robust models. However, most often are thermal-radiation and conjugate heat-transfer overlooked. This may be due to the challenges associated with the physics and modeling of thermal-radiation heat-transfer. Only a handful studies deal with this topic, suggesting that although the global effects in terms of power are small, the energy redistribution by thermal-radiation is important. Here, we apply finite-rate chemistry LES to a well-known bluff-body stabilized flame, for which experimental data is available to analyze the influence of thermal-radiation and conjugate heat-transfer on the flow/flame. Two thermal-radiation models, the P1 and fvDOM models, are used to examine the sensitivity of this modeling, and comparisons are made with experimental velocity, temperature and CO mass-fraction profiles, with and without conjugate heat-transfer. The results show that the LES results taking thermal-radiation and conjugate heat-transfer into account are in better agreement with the experimental data than the LES results not taking these effects into account. Also, the differences between the P1 and fvDOM models are small, but with the results using the fvDOM model in better agreement with the experimental data. The LES results are also used to elucidate the flow/flame physics, and the influence of thermal-radiation and conjugate heat-transfer that should not be overlooked in studies of turbulent combustion.