Research On Aerodynamic Noise And Structural Improvement Of Cage-type Throttle Valve

As a core component of ground throttle system,corbula type throttle valve is usually used in exploition in gas field with high pressure.High noise caused by natural gas with high pressure when passing through throttle valve will seriously affect regular work of gas field.In this paper,in order to slove problems caused by aerodynamic noise of throttle valve,numerical simulation is ued to study genreation principles and properties of aerodynamic noise,which fills blank zone in China on how to control noise of corbula type throttle valve and provides theorical backup on how to produce throttle valve with low noise.Firstly,three-dimensional model of fluid domain is established at first,a CFD software,fluent is used to do steady and transient simulations.Status of fluid when flowing through valve with different pressure ratios is gained by steady simulation.which provideds basic information of fluid domain at the same time.LES(Large Eddy Simulation)is done to study typical working conditions,Changing properities with time of fluid is gained during the process,the results of LES have more procise details of distributing properties of fluid domain.Producing principles of aerodynamic noise of valve is analyzed according to generation of vortex noise and jet noise,meanwhile,how shock wave noise affects fluid domain and sound domain,noise sources of valve is concluded,as a result,information of time domain is gained to analyse noise properties.Secondly,FW-H acoustic analogy method is used to conduct acoustic simulation,in order to get spectrum and power spectrum of noise in different areas of valve,distributing regulations and spreading characters is gained.The main contributing frequency of the jet noise and turbulence noise is concluded by studying on how working conditions and valve structures affect aerodynamic noise,the results also show that there is a distinct difference between spectrums of supersonic jets and subsonic jets.Meanwhile,workbench is applied to do structural modal analysis of valve pipe system,to find better modal structures for controlling aerodynamic noise of valve pipe system.Acoustic modal of valve's cavity is analyzed by Virtual.Lab,as a result,frequency of acoustic modal and modal amplitude is gained,meanwhile,the main modals for causing acoustic resonance gotten by associating with distributions of fluid field and sound field.Finally,a structural optimization of corbula type throttle valve is given based on studying conclusions of noise and generation of aerodynamic noise.The structural optimization changes the flow structure of valve,and it's effect on lowing down noise is analyzed from simulation of fluid field and sound field.As a result,supersonic jets are formed due to valve's throttling function lets a large part of pressure energy of fluid transfers into kinetic energy,mutual collisions and mixture among supersonic jets in corbula sharpen turbulent extent of fluid severely,resulting in different extent of structures of shock wave and turbulence,which is the core reason for producing aerodynamic noise.The aerodynamic noise of throttle valve is characterized with broad band,in the up stream of valve,the sound pressure level of different monitoring points barely change,yet sound pressure level of monitoring points in the downstream is more higher than that of upstream.Influence from jets noise weakens swiftly along the flowing direction of fluid,sound pressure level decreases and main noise frequency band moves towards low frequency band during this process.The fifth and the second order structural modes of the throttle valve are the dominant modes,and the dominant modes of the acoustic modes are the third and the seventh order of the acoustic modes.The flowing status of gas can be stablized by changing incident angle of throttle holes on corbula to reduce pulsing extent of fluid,which is proven to has a good noise reduction effect.