Book Description

This program was directed towards elements of combustor and turbine noise; the latter including turbine tone interaction with jet stream turbulence. Combustor (Core) Noise - Investigations were conducted to determine the variables affecting source strength, spectrum shape, and farfield directivity. This investigation include scale model tests to evaluate the effects of exhaust nozzle geometry on radiation patterns of low frequency noise. A full-scale combustor rig test was used to identify the controlling variables of combustor noise at the source. Two engine tests were run to validate the findings from the scale model tests and add to the overall data base of core noise measurements. The relationship between combustor source noise and emissions was studied and qualitative trends identified for advanced low emissions combustors. Turbine Noise - Studies were made of the attenuation of high frequency turbine noise by downstream blade rows, the broadband noise generation by turbines, and the controlling parameters for turbine tone/jet stream interaction. This included a turbine rig test in single and multistage configurations, along with a unique data acquisition system. Scale model tests were used to define the effect of the pertinent aero-acoustic parameters on turbine tone scattering by jet stream turbulence. The results of these investigations were used to improve the component prediction techniques derived under the Core Engine Noise Control Program (FAA-RD-74-125, III). These improved prediction techniques were used to predict the noise contribution of each source for high bypass turbofan engines representative of current and advanced technology. (Author).