Study On Sound Structure And Flow Field Noise Of Twin Screw Air Compressor

Twin screw air compressor is a kind of power device widely used in the market.It is widely used in the fields of petroleum,chemical industry,refrigeration,mining machinery and new energy.In the development process of twin-screw air compressor,its performance and development direction are constantly improved and broken through.Due to its complex mechanical structure,narrow cavity and difficult machining of spiral surface,the research of scholars at home and abroad mainly focuses on the optimization of screw rotor profile,the analysis of structure and flow field characteristics and the optimization of rotor machining process,while the research on noise is relatively few.At present,the noise problem of twinscrew air compressor is becoming more and more prominent,especially the mechanical noise and flow field noise.Therefore,in order to make the twin-screw air compressor achieve the purpose of vibration and noise reduction,this paper analyzes the noise generation mechanism and distribution law of the twin-screw air compressor from two aspects of mechanical noise and flow field noise.The research work is as follows:（1）The mechanical noise analysis model is established.The mechanical noise analysis is divided into two parts: acoustic modal analysis and acoustic structure coupling analysis.By simulating the acoustic cavity resonance of the air compressor shell,the vibration modes of each order of acoustic modes are studied;On this basis,some characteristic positions of the shell are taken to analyze the sound pressure and the distribution law of sound pressure level under different characteristic frequencies.The results show that under the same characteristic frequency,the sound pressure at the inlet end,exhaust end,shaft end and shell surface changes from large to small.（2）The active noise caused by the radial vibration or unstable vibration of the rotor caused by the instability or rubbing of the rotor due to the misalignment of the bearings in the working process of twin screw air compressor is simulated.A coupled acoustic-structural simulation model is established to analyze the structural deformation and the distribution of sound pressure level on the shell surface under the combined action of structure and sound field.The distribution of sound pressure level on different planes and sections of the Shell,and the sound pressure level and deformation of the shell at different frequencies are studied.（3）Based on the flow field noise,the mechanism of flow field noise of twin-screw air compressor is analyzed.On this basis,the sound power level distribution law of twin-screw air compressor under specific working conditions is analyzed,and the noise distribution law of different parts of air compressor is obtained.The influence of the change of the volume between teeth on the noise is simulated by changing the top clearance and center distance of the twinscrew rotor of the air compressor.By changing the speed of male rotor to simulate the noise of air compressor under different working conditions,the distribution law of sound power level at different speeds is obtained.The research results can provide theoretical guidance for the design and noise reduction of twin-screw air compressor.