Title page for ETD etd-042399-125728


Type of Document Master's Thesis
Author Rao, Nikhil M
URN etd-042399-125728
Title Reduction of Unsteady Stator-Rotor Interaction by Trailing Edge Blowing Using MEMS Based Microvalves
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Ng, Fai Committee Chair
Burdisso, Ricardo A. Committee Member
Dancey, Clinton L. Committee Member
Keywords
  • Trailing Edge Blowing
  • Noise
  • Aeroacoustics
  • Turbomachinery
  • MEMS.
Date of Defense 1999-04-16
Availability unrestricted
Abstract
This research performs an experimental study of a

trailing edge blowing system that can adapt to

variations in flow parameters and reduce the

unsteady stator-rotor interaction at all engine

operating conditions. The fan rotor of a 1/14

scale turbofan propulsion simulator is subjected

to spatially periodic, circumferential inlet flow

distortions. The distortions are generated by four

struts that support a centerbody in the inlet

mounted onto the simulator. To reduce the unsteady

effects of the strut wakes on the rotor blades,

the wake is re-energized by injecting mass from

the trailing edge of the strut. Each strut is

provided with discrete blowing holes that open

out through the strut trailing edge. Each blowing

hole is connected to a MEMS based microvalve,

which controls the blowing rate of the hole.

The microvalve is actuated by a signal voltage,

generated by a PID controller that accepts free

stream and wake axial flow velocities as inputs

and minimzes their difference. To quantify the

effectiveness of trailing edge blowing the

far-field noise is measured in an anechoic

chamber. The experiments are performed for two

simulator test speeds, 29,500 rpm and 40,000 rpm,

with and without trailing edge blowing. The

maximum reduction recorded at 29,500 rpm is

8.2 dB, and at 40,000 rpm is 7.3 dB. Reductions

of 2.9 dB and greater are observed at the first

five harmonics of the blade passing frequency.

The sound power level at the blade passing

frequency, calculated from measured far-field

directivity, is reduced by 4.4 dB at 29,500 rpm

and by 2.9 dB at 40,000 rpm. The feasibility and

advantage of active control is demonstrated by the

ability of the system to respond to a step change

in the inlet flow velocity, and achieve optimum

wake filling in approximately 8 seconds.

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