University of California,
Sponsorhip: The Boeing Co.
We are investigating the aeroacoustics of ducted fans through a subscale experimental simulation, focusing on the conditions typical of a geared turbofan (GTF). The goal is to measure the directivity of the tones arising from rotor-stator interaction and their shielding by a barrier having the shape of the hybrid-wing-body airplane. The rotor, stator, and nacelle are fabricated using high-definition stereolithograpy, a process that enables unprecedented flexibiiy in designing/ re-designing these components at low cost. The rotor is powered by a brushless DC motor typically used on extreme-performance RC airplanes. The subscale simulation is to match the fan pressure ratio and rotor tip speed of a realistic GTF. This means running at very high power levels (50V x 150A), using lithium-polymer batteries, and fairly insane rotational speeds of ~60,000 RPM.
A predecessor of this effort, funded internally, examined the aeroacoustics of counter-rotating open rotors in isolation and in the presence of a shield.
Truong, A. and Papamoschou, D., "Aeroacoustic Testing of Open Rotors at Very Small Scale," AIAA-2013-0217, 51st AIAA Aerospace Sciences Meeting, Grapevine, TX, Jan. 7-10, 2013. (PDF)
Truong, A. and Papamoschou, D., "Experimental Simulation of Ducted Fan Acoustics at Very Small Scale," AIAA-2014-0718, 52st AIAA Aerospace Sciences Meeting, National Harbor, MD, Jan. 13-17, 2014. (PDF)
GTF model on test stand outside anechoic chamber.
Movie of inital RPM test (AVI, 16 Mb). Sensor indicated 58,000 RPM.
GTF rotor (70-mm dia.)
Counter-rotating open rotor experiment.
Rapid-prototyped propellers used in open-rotor tests.
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