The Experimental Measurement And Analysis Of Scroll Vacuum Pump's Flow Noise

Dry scroll vacuum pump has some advantages such as the clean pump without oil,a wide range of work pressure,small volume,small vibration,low noise and so forth,which is used in many kinds of clean vacuum such as semiconductor manufacturing,pharmaceutical and other industries.Under the real working condition,dry scroll vacuum pump could face various complicated harsh venting ambient,such as corrosive gas,the gas with dust particle,the change of suction pressure and temperature.Noise and vibration is one of the indexes to measure the performance of vacuum pump,which means that the smaller of noisy,the better mechanical equipment.So it is important to research the mechanism of fluid noise producing and noise control measures of scroll vacuum pump.This thesis mainly aims at the problem of aerodynamic noise of dry scroll vacuum pump.The experiment tests the noise and exhaust flow of the existing two scroll vacuum pumps which have the same pumping and different manufacturers,and then analyzed the experimental results.Firstly,control the working condition of the pump.The pump inlet is connected to the vacuum container,change the valve opening to control the pump inlet pressure in 101 kPa,80 kPa,60 kPa,40 kPa,30 kPa,which corresponded to the the performance under the different load conditions.The experiment test exhaust flow field under the different pressure using PIV(Particle Image Velocity)and get exhaust velocity and velocity distribution of two pumps under different inlet pressure.Secondly,according to outlet pressure which is in the internal flow field simulation of scroll vacuum pump,the result is set as initial conditions and the experiment simulate the exhaust process,using CFD(Computational Fluid Dynamics)under the 101 kPa inlet pressure,which get the pressure of the exhaust velocity and the gas movement.Compared the simulation results and test results,the thesis analyze the influence of different structure of the pump to the exhaust flow.Finally,the experiment tests the noise of two pumps under the different work pressure according to the national standards.Following the standard,measure the A-weigh noise in eight different positions which is 1 meter away from the pump and get the noise of the pump under different working conditions.As the suction pressure reducing,2000Hz-7000Hz frequency range noise is reduced,but the noise under 2000Hz frequency will not be changed.The muffler will reduce the flow noise and the valid range is 101kPa-40kPa.The noise will increase when the suction pressure range is 10kPa to 30kPa and the noise frequency is mainly concentrated in about 300Hz.According to the national standards test the vibration,the scroll vacuum pump vibration is very small.The vibration is similar under different working conditions and the flow noise has nothing to do with vibration.