Research on Noise Generated by Ducted Air-Fuel Combustion Systems.
Annual rept. no. 2, 1 Mar 72-28 Feb 73,
PRINCETON UNIV N J DEPT OF AEROSPACE AND MECHANICAL SCIENCES
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A two-pronged approach to the study of noise generation by combustion in a confined flow system, similar to a jet engine configuration, is described. One aspect deals with the mechanisms of noise generation by combustion the other aspect deals with the effect of confinement on the noise generation and radiating properties of an unsteady solid-body-flow interaction. The mechanisms of noise generation by combustion are being studied analytically. It is noted that the steady flame structure determine the basic thermodynamic properties such as the sound speed and distribution of heat release, which affect amplification, dispersion and propagation of sound. The non-steady flame characteristics are responsible for noise generation the turbulent scale, period and intensity affect the burning rate and heat release rate. The overall noise generation character is a superposition of the steady and non-steady acoustic characteristics. In studies with ducted and non-ducted sources, it is found that the interaction between the duct and the noise source can enhance the noise generation potential of the source region. The noise due to unsteady flow over small struts inside a duct is found to overwhelm the free jet noise up to speeds in excess of 1000 ftsec. Author
- Jet and Gas Turbine Engines