Side Air-Jet Modulation for Control of Heat Release and Pattern Factor

The effect of a forced dilution air jet introduced through the combustor shell, on the air-fuel mixing in the combustion chamber has been investigated. Thermocouple based temperature measurements have been made at a number of forcing frequencies in the range of 100-1100Hz and blowing ratios in the range of 10-15. The open-loop integral flame response to forcing has also been acquired by recording pressure and heat release spectra. A CH-radical imaging technique is used to provide spatially- and temporally- resolved information about the heat release behavior. The results exhibit that the mean temperature field inside the main reaction zone can significantly be altered as a consequence of air jet modulation. The most significant effects are observed by forcing at vertical locations that are close to the dump plane. Enhancements in temperature of the order of 100-200 degrees C, and reduction in pattern factor of the order of 10% (e.g., from 1.13 to 1.03) were observed, with the lowest pattern factors achieved at the lowest forcing frequency of 100 Hz.