Optical probe for measuring the extent of air and fuel mixing in lean premixed combustors and the effect of air and fuel mixing on combustor performance

This Thesis describes the development and implementation of an optical technique for measuring the extent of air and fuel uniformity (both spatially and temporally at the exit of a premixer). The optical probes described can be inserted into the combustor premixer through the combustion liner. The techniques described here bridge the gap between sampling probe techniques for measuring spatial uniformity and non-intrusive (but difficult to apply) laser based techniques for measuring both spatial and temporal uniformity.;The light from the 3.39 ;The first optical probe described utilizes fiber optics to guide light to and from a measurement probe volume. This technique was used to determine the extent of air and fuel uniformity leaving a premixer for a lean premixed combustor. The optical probe was capable of measuring small changes in air and fuel uniformity and these changes led to a large increase in nitrogen oxides (NO;A second version of the optical probe was used to measure the effect that pressure oscillations, originating in the combustion chamber, have on the fuel-air mixing. A line of sight absorption technique was used to measure the fuel concentration fluctuations near the exit of a lean premixed sudden expansion combustor. Larger fuel fluctuations occurred when combustion was occurring in the combustion chamber. Air and fuel temporal uniformity had a profound effect on the magnitude of the pressure oscillations.;A third version of the optical probe was a variation of the common suction probe. In this case, instead of the sampled gas being directed into a hydrocarbon analyzer, the sample is passed through a small gas cell through which the 3.39...