Date of Award

Summer 1999

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Howard V. L. Patrick

Committee Member

Yechiel J. Crispin

Committee Member

Don Higdon

Abstract

In recent years increased public awareness has made the reduction of environmental noise pollution a top priority for the aviation industry. Utilizing current technology, this study examines the reduction of noise generated by two bladed general aviation propellers, through design. The Aircraft Noise Prediction Program - Propeller Analysis System (ANOPP-PAS) is used to predict the noise and performance characteristics for an industry typical reference propeller as well as for the final quiet and efficient design.

This investigation is based on the use of a 200 hp engine rotating a 76 inch propeller. Typically, such a propeller would be rotated at 2700 rpm; however, the quiet propeller is designed to operate at 2400 rpm. This rotational velocity reduction is incorporated in order to decrease the rotational tip speed thereby preventing the formation of undesirable shocks at the tip. The reference propeller spinning at 2400 rpm achieves a 9 dB reduction in far field OASPL and a 9.6 (14 dBA) reduction in near field OASPL when compared to the reference propeller spinning at 2700 rpm. It should be noted that the values at 2700 rpm are under predicted by 3-10 dB due to a known ANOPP shortfall in shock wave noise prediction.

Blade twist distribution, tip shape, airfoil design, and blade sweep were all modified and examined through parametric study to further quiet the design and maintain desirable performance characteristics. These modifications produced additional reduction of 1.1 dB (3.6 dBA) reduction in far-field OASPL. Near-field noise characteristics were reduced by 17 dB (2.3 dBA). The final quiet design is achieved with a 1% increase in performance.

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