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The purpose of this study is to investigate the performance of
sudden expansionsilencer on the engine exhaust system and to
suggest a simple experimental method for this evaluation .
It is expected to simplify the evaluation processof sudden
expansion silencer and understand the feedback interaction
between the silencer and the upstream system. Qualitatively,
laser sheet flow visualization is employed to reveal the
instantaneous flow structure inside andat the exit of the
silencer. Furthermore, the fluctuating energy of the
velocity, the pressure and the sound level are related while the
inflow frequency range from 1 Hz to 120 Hz.
It is found that the frequency response of the fluctuating
energy of the velocity and pressure are closely linked to
the sound level measured downstreamof the exhaust system. This
suggests that the frequency response of the one-location
pressure measurement inside the silencer be a simple way that
can greatly reduce the time for evaluating the silencer. When
the flow is present,the silencer and its upstream system should
be thought as a unit to faithfully reveal the performance of the
whole system. Sound level
measured far downstream of the silencer includes the low
frequency flow tone induced inside the silencer and the high
frequency noise generated bythe exhaust jet flow. Therefore,
modification of the flow structure inside thesilencer will
change the low frequency flow tone, whereas the high frequency
noise level can be improved by manipulating the exhaust jet flow
structure.
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