NOx formation in premixed turbulent flames

NO x formation has been studied in lean, premixed, turbulent flames stabilized by perforated plates. The burner pressure was atmospheric, but other parameters were representative of gas turbine operating conditions. Prevaporized Jet A fuel was injected into preheated unvitiated air and thoroughly mixed prior to combustion. Mixture inlet temperature was 750°K and total residence times were approximately 4 msec. NO x , CO, CO 2 and hydrocarbon levels were measured along the jet and recirculation zone axes. Results show a very rapid increase in NO x in the reaction zone which cannot be accounted for by O-atom radical overshoot. Post-flame zone NO x formation rates agree with the predictions of equilibrium theory. The relative contribution of “prompt NO x ” to the final NO x levels increases with decreasing equivalence ratio. The rate of NO x formation in the reaction zone is found to be higher than in laminar flames. Turbulent transport processes are believed to be the dominant effect. NO x formation via nitrous oxide intermediate does not appear to be important under the present experimental conditions. Large amplitude temperature oscillations observed in turbulent premixed flames were found not to affect NO x formation rates.