University of California, Irvine
Aeroacoustics Lab

TURBOFAN BLEED VALVE NOISE CHARACTERIZATION AND SUPPRESSION

Sponsorhip:  Parker Hannifin Corp.

A combined experimental and computational research effort investigated the noise sources of a pneumatic bleed valve used in turbofan engines and developed engineering solutions for attenuating those sources. The experimental effort employed 1/4-scale, rapid-prototyped valve designs which enabled the exploration of a large parameter space. Microphone array systems surveyed the sound and its sources, and Pitot surveys measured the mean velocity downstream of the valve. The numerical code solved the Reynolds-Averaged Navier Stokes (RANS) in both steady and unsteady modes. The research addressed the flow and acoustics of the valve without and with a muffler. The noise of the isolated valve consists of conventional jet noise with strong excess sound originating from the valve exit. The excess sound was traced to vortex shedding by support struts. Streamlining of the struts, aided by computational parametric studies, eliminated this noise component. The noise of the complete valve, with muffler attached, was attenuated by two principal means: using the streamlined struts and adding a honeycomb flow straightener to the muffler cavity. Proper installation of the honeycomb is critical for maximizing noise reduction. The resulting best design achieved a reduction of approximately 8 decibels in perceived noise level.

Publication:  Phong, V., Taghavi Nejad, S., Liu, F., and Papamoschou, D., "Noise Reduction of a Turbofan Bleed Valve," AIAA-2012-0681,  50th AIAA Aerospace Sciences Meeting, Nashville, TN, Jan. 9-12, 2012.  (PDF)

Patent application:  Papamoschou, D. and Liu, F., "Quiet Bleed Valve for Gas Turbine Engine".

turbofan_bleed_valve.JPG (49069 bytes)

Compressor bleed valves installed on a turbofan engine.  The valves can create significant noise, particularly on approach when the engine is at low power setting.

 

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Stereolithography model (1/4-scale) of intermediate pressure bleed valve (IPBV) tested at UCI.    Muffler is not attached.

ipbv_honeycomb.JPG (202883 bytes)

Muffler design developed at UCI, including honeycomb flow straightener (shown here with dome plate removed).

ipbv_cfd.jpg (69813 bytes)

Computational simulation of valve internal and external flows.

ipbv_optimal_design.JPG (24684 bytes)

Schematic of optimal design developed at UCI.

 

ipbv_noise_reduction.JPG (32611 bytes)

Changes in perceived noise level (PNL) at different nozzle pressure ratios (NPR) as a result of the design modifications developed at UCI.     Noise was reduced by approximately 8 decibels.

 

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