Effects of Turbulence on NOx Emissions from Lean Perfectly-Premixed Combustion

Effect of turbulence on NOx emissions is studied for a perfectly-premixed combustor running on methane/air at the mixture inlet temperature of 495 K and the combustor pressure of 5 atm over a range of equivalence ratios (0.54--0.85). Turbulence level is varied by a factor of 2--3 by changing the length of a portion of channels in a perforated plate on which the flame is stabilized. Simultaneous PIV and OH-PLIF measurements are used to calculate the relevant turbulence parameters such as turbulence intensity and turbulence mixing time scales, and define the flame structure such as average flame height and hence flame zone residence time scales, respectively. Effect of turbulence level is found to have negligible effect on NOx emissions level. NOx emissions are predicted by using a partially-stirred reactor (PaSR) model in CHEMKIN-PRO package with the measured turbulence parameters as the input. The modeling results agree very well with the measured NO x emission level but show that it slightly increases with the increase of turbulence level.