Author                                                                                                                              
 


Chen Li

Aerospace Engineering,
Mechanical Engineering

Chen Li has always been fascinated with fluid dynamics and was excited by the opportunity to look into the acoustics of geared turbofans. By working on a small rotor, he was able to test a number of innovative sound-suppressing techniques without the expense and space a full-scale rotor would require. For Chen, the most satisfying part of his research was the opportunity to work, as an undergraduate, on a project at the forefront of aerospace engineering along with people who shared his passion for their work. Chen is now pursuing an M.S. in Aerospace Engineering.triangle.gif (504 bytes)

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Abstract                                                                                                                           
 

This study relates to the acoustic simulation of a realistic geared turbofan (GTF) engine, using a very-small-scale GTF from UC Irvine’s Aeroacoustics Lab. The paper describes the theoretical modeling for duct acoustics of rotor-stator-interaction (RSI) inside an infinite, hard-walled annular duct with inviscid moving medium. RSI generally refers to the rotor wake interacting with the downstream stator, which then directly relates to noise emission. Bessel functions are used to compute pressure perturbations. The periodicity of the flow field is related to the specific azimuthal periodicity of the rotor, which provides the theoretical cut-off (on) criterion. Their respective acoustic properties agree rather firmly with the theoretical sound pressure level spectra plotted from actual acoustic testing This paper is collaborated with the Aeroacoustics Lab's attempt to verify the feasibility of using small scale, stereolithographic-fabricated propellers to simulate the acoustic performance of realistic ducted fans. The developed substitute for large experimental setups could bring down experimental costs considerably and increase variation of the rotor for more innovative design. The simulator accurately reproduces the tonal noises at discreet blade passing frequencies. In the case of low-polar-angle acoustic waves, the theory successfully predicts the cut-off (on) scenarios for the first two blade-passing tones.triangle.gif (504 bytes)

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Faculty Mentor                                                                                                                
 

Dimitri Papamoschou

Henry Samueli School
of Engineering
 

The future of commercial aircraft propulsion involves turbines driving very large fans, which are essentially propellers enclosed in a duct. The so-called high-bypass turbofan engines emit distinct noise signatures that need to be attenuated for future aircraft to be extremely quiet so that they are barely perceptible to communities near airports. The paper by Mr. Chen Li explains some of the mathematics behind this noise generation. Even though the math level is above that typically taught in our undergraduate courses, a motivated undergrad like Mr. Li is able to handle the challenges and learn about the richness and beauty of things like Bessel functions. I think he had fun with it, and I hope that more undergrads will be intrigued and learn about these mathematical concepts.triangle.gif (504 bytes)

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