The Numerical Calculation And Noise Reduction Analysis Of VRD16Rotary Vane Vacuum Pump Aeroacoustics And Structural Vibration Noise

Due to the characteristics of the structure and working principle of rotary vane vacuum pump, vibration and noise is inevitable. Foreign manufacturers have long pay attention to the vibration damping and noise reduction, the noise of their products, generally lower than the domestic pump around10dB(A), domestic users have requirement to reduce the vibration and noise strongly in recent years, so it is necessary to study and control its vibration and noise.This thesis choose the vibration caused by slow rotor eccentricity and cavity radiation noise, exhaust noise, oil drip pan and valve retainer radiation noise of VRD16rotary vane vacuum pump to have numerical simulation analysis research and optimization design.By using multi-body dynamics and hydrodynamic lubrication method for coupling digital calculation of rotor system of VRD16rotary vane vacuum pump, inside the calculation, the oil film pressure mathematical model is analytic solution from short bearing theory of Capone, compare the axis motion parameters of coupling calculation and multi-body dynamics calculation, the coupling calculation is more coincident to the actual situation. The oil film pressure is larger when two shafts vertical lay up by comparing two systems of rotor, transform the oil film pressure by using the fourier method, and add it to the cavity, use the MPC coupling method to simulate the connection of bolt, use the FEM method to get the vibration response of cavity in frequency domain. Using least square method to match the oil film pressure and filter the high frequency vibration, from the fourier transform, it is not conform to the experimental data, so this thesis take the high frequency vibration into account to calculate the vibration of cavity. It is general coincident of the theoretical calculation data and experiment data by comparing the vibration response of cavity less than400Hz, this could indirect proof the accuracy of the theoretical calculation of the whole frequency domain. Because the frequency domain of the oil film pressure is wide, so it could motivate fourteen modals of the cavity and the cavity would be in large vibration. Use the vibration response of the cavity as the boundary conditions and the BEM method to calculate the radiation noise of the cavity. By changing the size of the oil film clearance to reduce the amplitude and the fluctuation, so that he cavity would be in low vibration.According to the structure of VRD16rotary vane vacuum pump, this thesis calculates the area of the compression cavity, inlet pressure and exhaust velocity and so on and use these parameters as the boundary conditions of the flow field analysis. Using the large eddy simulation method to calculate the flow field of the exhaust cavity of the VRD16rotary vane pump to get the pressure and velocity distribution. Transform the pressure on the wall of the exhaust cavity with fourier and generate the dipole noise source to calculate the far field noise of the exhaust cavity with FEM method and AML method in the LMS Virtual.Lab software. With the comparison of the high vacuum cavity and the low vacuum cavity, the air noise of the high vacuum cavity is obviously higher, but after2500Hz, the air noise in two cavities similar. Through the flow distribution analysis of the oil drip pan, the fluctuation of the wall would cause some vortex, so the flow pass of the oil drip pan is modified. The pressure fluctuation on the monitoring point is obviously reduced. Through the calculation of the modified flow pass, the average sound power level of field point in high vacuum cavity is reduced7.70dB, and6.92dB in low vacuum cavity, and the average sound pressure level of the Field_Point is reduced8.72dB and7.83dB. It is obviously reduced of the noise of high vacuum cavity from changing the structure to increase a exhaust port, and the average sound power level of field point is reduced31.62dB, the average sound pressure level of Field Point is reduced31.33dB.The vibration and the radiation noise of the oil drip pan and the valve retainer is calculated through fluid-solid coupling technology, the vibration amplitude and velocity is gradually reduced around a static value. So the vibration of the oil drip pan and the valve retainer is convergence, namely the oil drip pan and the valve retainer have static deformation on the pressure of air flow, so the vibration and radiation noise of the oil drip pan and valve retainer caused by air flow is not high.