Numerical simulation of a reversed flow small-scale combustor

A numerical study of a reversed flow small-scale combustor is reported. The combustion chamber is a closed end cylinder with the burner and the exhaust port mounted at the top of the combustor. Natural gas was used as a fuel and the combustion air was preheated to 600 K. Two distinct conditions, achieved by varying the air flow rate were analyzed, the first being a conventional lean combustion regime and the second corresponding to the flameless combustion regime. The numerical simulations were carried out using ANSYS Fluent 13.0. Turbulence was modeled using the realizable k–ε model. The performance of two different combustion models, namely the eddy dissipation concept (EDC) and the composition PDF (C-PDF) model, was compared. Detailed chemical mechanisms for natural gas were employed. The sensitivity of the results to the mesh size, number of stochastic particles in the C-PDF model, reaction mechanism and constants of the models was investigated. A good agreement between the predictions obtained using the EDC and the C-PDF model was found. However, both models underpredict the measured temperature in the vicinity of the centreline in the region close to the burner, i.e., combustion is delayed in comparison with the experimental data, for both operating conditions.