Modeling Nonequilibrium Combustion Chemistry Using Constrained Equilibrium Flamelet Model for Kerosene Spray Flame

Numerical simulation employing different models is popularly used to predict spray combustion of liquid fuels. In the present work, we have compared the effects of three different combustion models, viz., eddy dissipation model, laminar flamelet model with detailed chemical reaction mechanism, and constrained equilibrium flamelet model, on the temperature, soot, and NO_x distributions in an axisymmetric combustor burning kerosene spray. Experiments have also been performed in a combustor of the same geometry to validate some predictions from the models. The constraint condition for the equilibrium flamelet model has been adopted by suitably accounting the effects of scalar dissipation rate on the prediction of scalar variables in a laminar flamelet and by considering the mixture fraction and scalar dissipation rate distributions in the combustor under test. It is found that the results predicted by the two flamelet models agree closely between them and also with the experiments. On the other hand, the eddy dissipation model predicts a much higher flame temperature, soot, and NO_x concentrations in the combustor. The results suggest the importance of chemistry in the prediction of the turbulent spray flame. It also suggests that with a proper choice of the constraint condition, the equilibrium flamelet model can address the nonequilibrium chemistry in the flame due to the high value of scalar dissipation rate.