Experimental and modeling investigation of the effect of air preheat on the formation of NOx in an RQL combustor

Abstract

The Rich-burn/Quick–mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of oxides of nitrogen (NO x ) in gas turbine systems. The success of this low-NO x combustor strategy is dependent upon the links between the formation of NO x , inlet air preheat temperature, and the mixing of the jet air and fuel-rich streams. Chemical equilibrium and kinetics modeling calculations and experiments were performed to further understand NO x emissions in an RQL combustor. The results indicate that as the temperature at the inlet to the mixing zone increases (due to preheating and/or operating conditions) the fuel-rich zone equivalence ratio must be increased to achieve minimum NO x formation in the primary zone of the combustor. The chemical kinetics model illustrates that there is sufficient residence time to produce NO x at concentrations that agree well with the NO x measurements. Air preheat was found to have very little effect on mixing, but preheating the air did increase NO x emissions significantly. By understanding the mechanisms governing NO x formation and the temperature dependence of key reactions in the RQL combustor, a strategy can be devised to further reduce NO x emissions using the RQL concept.