Noise Analysis And Noise Reduction Of Pulp Molding Vacuum System

The development of the concept of ecological civilization has brought great development prospects to the pulp moulding industry,but the paper film production line usually produces a lot of noise.Based on the current production situation,this paper mainly carries out noise analysis and noise reduction research on the vacuum system of the pulp production line.Firstly,the vacuum pump and vacuum system are modeled and analyzed by Inventor,then the flow field grid of the vacuum system is analyzed by Fluent to get the water phase contour in the working process of the water ring pump;secondly,according to the modal analysis of the structure grid of the vacuum system,the transient displacement response of the structure is obtained by using the flow field calculation results as the pressure boundary condition;thirdly,displacement response of the structure is obtained which establishes the acoustic boundary element mesh of the vacuum system in the LMS Virtual.Lab,imports the transient response results calculated by ANSYS,and obtains 1octave sound pressure level spectrum of six typical field points.The validity of the simulation model is verified by comparing with the field point experiment results.Next,a noise reduction scheme is added to the simulation model,and the feasibility is verified by simulation calculation.Finally,the effectiveness of the scheme is further verified by field point measurement of the noise reduction experiment.It has been found that the noise response of the separator is mainly concentrated in the low frequency bands of 31.5Hz and 65Hz;the noise of the water ring pump is mainly concentrated in the frequency bands of 500 Hz and 1000Hz;the sound pressure level of the field near the drainage outlet of the separator is the highest in all frequency bands,because there are not only the noise generated by the structural vibration of the shell ofthe water ring pump and the separator,but also the noise from the inner wall of the pipeline.Noise generated by a dipole source.Then,based on the simulation model,the noise reduction scheme of adding a section of rubber pipe to the separator drain pipe is put forward.Firstly,the noise reduction effect of the optimized scheme is calculated by computer simulation.It is found that the sound pressure level decreases in varying degrees in each frequency band,especially in 250 Hz and 500 Hz bands.Then the sound pressure level of the field points before and after optimization is measured by field point experiments.It is found that the results are basically consistent with the simulation results,which verifies the rationality of the noise reduction scheme.In addition,it is also known that the noise generated by the wall dipole source in the vacuum system pipeline is mainly in the frequency bands of 250 Hz and 500 Hz.