| Engine is the heart of the aircraft, its performance and reliability directly affect the quality and safety of the aircraft. The enginecan produce unstable flow conditionunder certain conditions. Now, the most difficult problem is axial compressor blade nonsynchronous vibration phenomenon (NSV), this phenomenon causes compressor producing big noise and damaging easily. In the 1970s, many scientists believed that the phenomenon was due to the backflow between casing and the blade tip clearance, called blade tip clearance flow.This blade tip clearance flowimpacts on the adjacent bladewith the direction opposite the blade and then led to the bladenonsynchronous vibration. After the experimentstudy, many scientists believed that the vortex of blade tip clearance flowwas the cause of the blade nonsynchronous vibrationphenomenon.Through the studying and analysing of the related literatureson the free jet vortex shedding theory, this article has a deep understanding the knowledge of the jet vortex shedding, and study the mechanism of free jet vortex shedding. Determine the experimental model and the area of free jet vortex shedding. According to the experiment requirement,designed and manufactured asimulativesubsonic wind tunnel test bench, and conducted the free jet experimentby this test bench. During the experiment, B&K 4189 microphone was used to measure the sound pressureof free jet, and the frequency of vortex sheddingwasdetermined by the sound pressure frequency. Through data processing,verified and determined thecorrect measurement method of vortex shedding frequency. Then dividedthe free jet flow field into multiple layers, and measured the vortex shedding frequency on every layers, and outputedcloud chart. Observed theappearance, development and disappearance of free jet vortex shedding on every layers. Improvedthe design and setted up a subsonic wind tunnel test bench, combined the technical parameters of the originalwind tunnel and the guidance of professional books. |
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