Experimental study of lean premixed turbulent combustion in a scale gas turbine chamber

Abstract

Cylindrical combustion chambers, 1:7 model scale of a dry low NO x combustor devoted to 200 kW elec cogeneration plants, have been developed in order to understand instability phenomenon in lean premixed combustion occurring in low NO x gas turbine (LNGT). Dynamic measurements of chamber pressure and of CH ∗ emissions have been performed. CH ∗ emission images have also been measured. Spectrum with several frequencies have been observed. Frequencies which are common to pressure spectrum and CH ∗ emission spectrum are considered to be characteristic of combustion phenomenon. The magnitude of the 32 Hz low frequency increase abruptly when mixture ratio is decreased to values close to extinction, and CO emissions show the same behaviour. For high equivalence ratios, the magnitude of 133 Hz peak strongly increases while the magnitude of 530 Hz peak decreases. The effect of the injection position of primary dilution air has been studied. It is observed that primary dilution decreases flame size, and has an effect on the flame structure, on local combustion equivalence ratio, which induce effects on flame stability and on CO emissions.