Flame structures in the pressurized methane-air combustor

This study has been carried out in order to investigate the applicability of a pressurized and fuel-rich burner as a first stage combustor for a newly proposed chemical gas turbine system. The flammability limits, exhaust gas composition and the NO_x emission characteristics under the pressurized conditions of 1.1 - 4.1 MPa have been investigated in a model combustor. This paper focuses on the influence of pressure and F/A equivalence ratio on flame structures of pressurized combustion with methane and air to obtain detailed data for designing of fuel-rich combustor for gas turbine application. The flame under fuel-rich condition and pressure of 1 MPa showed underventilated structure like other atmospheric fuel-rich flames while the flame under pressure over 1.5 MPa had shapes as fuel-lean flame. The flame becomes longer as the pressure was increased under the fuel-lean condition, while under fuel-rich condition the influence of pressure on flame length was smaller in comparison with the flame under fuel-lean conditions. These results give an opportunity for developing smaller combustor under fuel-rich and pressurized condition compared to fuel-lean one. Numerical simulation has been done for defining the temperature profile in the model combustor using the k-ε turbulence model and three-step reaction model. The comparison between theoretical results and experimental data showed fair agreements.