| Summary: | 碩士 === 國立中興大學 === 機械工程學系 === 86 === This study investigates the performance of sudden expansion
silencer with internal baffle-wall and connecting duct in
relation to some design parameters. Such parameters are the
length and the asymmetry of input and output ducts, the length
and height of the connecting duct as well as the porosity ratio.
The inflow frequency ranges from 10Hz to 120Hz. The evaluation
is based on the magnitude of pressure variation within and sound
level measurement downstream of the silencer . Frequency
responses of both pressure variation and the sound level are
coincident for frequency lower than 100Hz. However, deviation
arises for frequency higher than 100Hz because of the presence
of small scale eddy in the exhaust jet. Large porosity ratio can
eliminates the noise level at low frequency range. Noise
reduction is significant while the internal baffle-wall is
inserted. Besides, the longer the connecting duct, the more
reduction of the sound level. The height of the connecting duct
determines the passage of energy at lower frequency. Thus, small
height of the connecting duct can reduce effectively the sound
level at low frequency range, and vice versa. Furthermore,
longer inlet duct can increase the sound level at frequency
higher than 100Hz. On the other hand, the longer outlet duct
will decrease the resonant frequency of the flow tone inside the
silencer. In the limiting case of no tail duct, the resonant
frequency locates beyond 120Hz and the sound level is high
within 00z In gnraly, h betperormne o nis reutio ca e atane
ifthe veticl bfle-al i intlle isie teasymeti siener Beies,
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cn hlp olocteth reoantfreuncyofth flwton inie tesilencer
Hihporsiy ati an lsob faoabl torduc te oun eve atlow
frquecyrage.Keyword: suden xpnson iencr、aflewal Bconctig
duc、orsit ati
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