Reduction of Unsteady Stator-Rotor Interaction by Trailing Edge Blowing Using MEMS Based Microvalves
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 spatiall...
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Virginia Tech
2014
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| Online Access: | http://hdl.handle.net/10919/31854 http://scholar.lib.vt.edu/theses/available/etd-042399-125728/ |
| Summary: | 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. === Master of Science |
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