Laminar flamelet model prediction of NOx formation in a turbulent bluff-body combustor

A bluff-body combustor, with recirculation zone and simple boundary conditions, is ideal as a compromise for an industrial combustor for validating combustion models. This combustor, however, has proved to be very challenging to the combustion modellers in a number of previous studies. In the present study, an improved prediction has been reported through better representation of turbulence effect by Reynolds stress transport model and extended upstream computational domain. Thermo-chemical properties of the flame have been represented by a laminar flamelet model. A comparison among reduced chemical kinetic mechanism of Peters and detailed mechanisms of GRI 2.11, GRI 3.0, and San Diego has been studied under the laminar flamelet modelling framework. Computed results have been compared against the well-known experimental data of Sydney University bluff-body CH4/H-2 flame. Results show that the laminar flamelet model yields very good agreement with measurements for temperature and major species with all the reaction mechanisms. The GRI 2.11 performs better than the other reaction mechanisms in predicting minor species such as OH and pollutant NO. The agreement achieved for NO is particularly encouraging considering the simplified modelling formulation utilized for the kinetically controlled NO formation.