1. For gas dynamic noise, the main area where the aerodynamic noise is generated is in the recovery zone immediately downstream of the shrinkage where the flow conditions are chaotic, completely irregular and discontinuous, with intense turbulence And mixed effect. The solution is to reduce the flow rate and reduce the turbulence effect. a) Multi-orifice throttling method. The acoustical power of a single-channel throttling member increases as a function of square of area. An area change of 1 × will result in a corresponding 6 dB change in the sound power level. Also, when the number of independent noise sources changes by a factor of 1, the sound power level will only change by 3 dB. The total noise reduction can be deduced from the comparison of many small throttles with one or a few large throttles, with no more than the sum of the noise generated by each injection. On the other hand, due to the high frequency of pinhole jet noise, the sensitivity of the human ear to high frequency noise is reduced at a relatively low frequency, ie the A-weighted sound pressure level is decibel low, whereas the general sound pressure level quantization of noise is weighted by A Unit dbA. Together, they reduce the A-weighted sound pressure level of the total noise. b) multi-stage decompression. This method uses multi-stage spool, cascading step by step with the step-down, the pressure drop spread, the orifice turbulence effect weakened. Gas medium can use the labyrinth spool, but the flow channel can not be too large, otherwise there is no multi-level effect on the gas medium. c) Tandem muffler. Silencer is a kind of diffuser with many small holes. It not only applies the principle of porous noise reduction but also increases the diameter of the downstream pipe and reduces the outlet flow rate. Muffler installed in the pipeline downstream of the valve. 2, the noise caused by mechanical vibration can only be solved by improving the structural design of the valve itself, such as increasing the diameter of the guide rod and reducing the gap to limit the lateral vibration, or to better limit the lateral vibration of the sleeve-oriented, but also More targeted response to specific conditions Design the body to avoid the resonance frequency band.
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