INVESTIGATION OF THE USE OF BEVELED NOZZLES FOR JET NOISE REDUCTION
Open Access
Author:
Senft, Maureen Elizabeth
Area of Honors:
Aerospace Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Dr. Dennis Mc Laughlin, Thesis Supervisor Dennis K Mclaughlin, Thesis Supervisor Robert Graham Melton, Thesis Honors Advisor Dr. George A Lesieutre, Faculty Reader
Keywords:
Beveled Nozzle Jet Noise
Abstract:
In recent years increasing population density near airports and military bases and the development of more powerful engines for military aircraft has prompted the serious consideration of noise reduction techniques for the aircraft. This paper reports on aeroacoustic experiments with laboratory size models of the engine exhaust nozzles. Specifically the study explores the effect on high-speed jet noise of beveled converging-diverging (CD) nozzles whose exit planes are oblique to the normal direction of the exit. The jets of small-scale nozzles with bevel angles of 24 and 35 degrees are compared to a baseline nozzle, each with a design Mach number of 1.65 and an area ratio of 1.295. Techniques such as schlieren and shadowgraph are used to visualize density gradients within the flow. With these flow visualization techniques the deflection of the plume in the case of the beveled nozzles is shown to be much smaller than the deflection found with supersonic jets exhausting from beveled purely converging nozzles. The acoustic data gathered presents a promising situation, with a noise reduction of approximately 3dB in the direction of the peak polar angle in the quadrant aligned with the long lip of the beveled nozzle.
