Analysis of the Pollutant Formation in the FLOX® Combustion

FLOX®, or flameless combustion is characterized by ultralow NOx emissions. Therefore the potential for its implementation in gas turbine combustors is investigated in recent research activities. The major concern of the present paper is the numerical simulation of flow and combustion in a FLOX®-combustor [Wünning, J. A., and Wünning, J. G., 1997, “Progress in Energy and Combustion Science,” 23, pp. 81–94; Patent EP 0463218] at high pressure operating conditions with emphasis on the pollutant formation. FLOX®-combustion is a highly turbulent and high-velocity combustion process, which is strongly dominated by turbulent mixing and chemical nonequilibrium effects. By this means the thermal nitric oxide formation is reduced to a minimum, because even in the nonpremixed case the maximum combustion temperature does not or rather slightly exceeds the adiabatic flame temperature of the global mixture due to almost perfectly mixed reactants prior to combustion. In a turbulent flow, the key aspects of a combustion model are twofold: (i) chemistry and (ii) turbulence/chemistry interaction. In the FLOX®-combustion we find that both physical mechanisms are of equal importance. Throughout our simulations we use the complex finite rate chemistry scheme GRI3.0 for methane and a simple partially stirred reactor (PaSR) model to account for the turbulence effect on the combustion. The computational results agree well with experimental data obtained in DLR test facilities. For a pressure level of 20 bar, a burner load of 417 kW and an air to fuel ratio of λ=2.16 computational results are presented and compared with experimental data.