Acoustical detection of obstructions in a pipe with a temperature gradient
Exhaust pipes of furnaces and similar equipment (e.g. for gasification) may get clogged up by deposition of sticky particles (ashes, tar, soot) carried by the gas mixture. The possibility of detecting the presence of such an obstruction by the reflection of an acoustic wave is investigated by a mathematical model. An important part of the problem is the considerable temperature variation along the pipe. It is argued that the high frequency components of the wave may be not reliable because of refraction and spurious reflection effects caused by this temperature gradient. Therefore, the reflection of low-frequency (one mode propagating) waves is investigated. It appears that the reflection becomes significant for a blockage area of more than 50%.
KeywordsSound Speed Strouhal Number Sound Field Modal Expansion Exhaust Pipe
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