The effect of acoustic oscillations on fuel-oxidant mixing is ana?lyzed for acoustic conditions commonly found in screeching and screaming combustors. Transverse acoustic fields in cylindrical ducts are described in terms of pressure fluctuation, particle velocity, and oscillation frequency. The effect of such acoustic fields on the fuel-oxidant mixing downstream from point sources of injection is treated theoretically to obtain expressions relating the fuel-oxidant ratio to the parameters of the stream and the acoustic field. Numerical solutions of these relations are made to illustrate the effect of sound-pressure level, oscillation frequency, stream velocity, and turbulence level. The results of this analysis show that, for moderate screech or scream levels, the fuel-oxidant mixing wake is given a transverse oscillatory motion of consider?able magnitude and that the fuel-oxidant ratio undergoes large cyclic fluctuations which are in phase with the pressure fluctuations of the acoustic field. A number, of possible mechanisms contributing to screech and scream in various combustor configurations are proposed, and methods for their control are suggested.
展开▼
