Scaled Demonstration of Fluid Insert Noise Reduction for Tactical Fighter Aircraft Engines

Abstract

This paper summarizes a university-industry cooperative project to develop a new method of noise reduction applicable to tactical fighter aircraft engines. There is an acute need for reduction of the noise produced during takeoff in aircraft carriers. This paper describes the fluid insert noise reduction technology, also referred to as “distributed blowing.” The method involves injection of air through the divergent wall of a converging–diverging nozzle to generate fluid inserts. Substantial noise reductions in small-scale experiments have been achieved for mixing noise in the maximum noise emission direction and in broadband shock-associated noise. This paper describes the extension of the methodology to moderate-scale experiments conducted in industry. Changes to the original small-scale design for use in the industry-scale model experiments are described. The experiments were conducted in the GE Aviation Cell 41 Laboratory, and noise reductions were achieved that were very similar to those obtained in the small-scale experiments. Changes to the operating parameters produced noise reductions that in some cases exceeded comparable small-scale results. Scaling the moderate-scale experiments to a full-scale aircraft produces reductions in the A-weighted spectral peak that exceed 7 dB in the direction of maximum noise emission.