Research On The Flow Noise And Radiation Acoustic Field Of The G-I Type Control Valve

With the wide application of control valve in electric power,petroleum,military and other fields,the study of its performance has become one of the key problems in industrial control system research field.In the work process,different cases can be achieved by changing the flow rate of control valve.High noise is generated by the flow instability,which is caused by the sudden change of system parameters.Therefore,control valve has always been a high noise source in the control system.At present,there is not the noise prediction standard of control valve generated by these key parts.Mostly the date associated with noise characteristics can be obtained by the experimental method.In this thesis,with the G-I type control valves as the research object,investigations of flow field and acoustic field for the valves are carried out,which can provide the reference for noise prediction and design of valve parts.In this thesis,the steady flow field and transient flow field are analyzed with the numerical simulation method.The steady flow field characteristics of control valves are studied with different opening degrees and pressure ratios.The relationship between the flow field distribution and various work conditions(pressure ratios and opening degrees)is obtained.The transition mechanism of flow pattern is acquired through the flow pattern analysis of control valve with different pressure ratios.Also the intrinsic links between the flow pattern transition and shock waves are explored.Through the transient flow field analysis,the information in time domain which can’t be obtained by the steady flow field analysis and is closely related to flow noise characteristics is captured.Therefore,the transient flow field analysis of control valve under the most severe condition of turbulence is performed to obtain the time-variant characteristics of flow field parameters.It can provide support for the calculation of inner acoustic field and radiation acoustic field of the control valve.Through the acoustic field analysis,the noise distribution characteristics of the inner acoustic field and the radiation acoustic field can be obtained.What’s more,the sound pressure level of the control valve can be calculated under different work conditions.Therefore,the acoustic field analysis can be an available method for the noise prediction of control valves.In this thesis,the flow noise in the control valve is calculated and the noise spectral characteristic of the feature points is analyzed.And the inner acoustic field of control valve is calculated and the distribution law of the inner acoustic field is analyzed by using acoustic boundary element method.Through the modal analysis of the control valve,the pressure pulsation frequencies which can cause valve resonance easily are determined.At the same time,the vibration noise induced by flow and the direct radiation noise are calculated respectively with the vibro-acoustic coupled method based on modal and direct calculation method.Then the main source of radiation noise is determined.By comparing the simulation results with experimental values,the reasonability and effectiveness of the current approach are validated.Finally,the optimization of valve structure is performed based on the above results and TRIZ theory.Then the analysis of flow field and acoustic field for the optimized control valve is carried out to verify the effectiveness of the improvement.