Study On Flow Field And Acoustic Characteristics Of Valve Gas Leakage

Industrial valves are widely used in various fields of the national economy,and the problem of valve gas leakage is a common problem in various fields,especially in petrochemical,nuclear power and other fields.Generally,the normally closed valves play the role of isolating media.When gas leakage occurs,light ones pollute downstream media,resulting in economic consumption,and heavy ones cause accidents such as explosion,fire,casualties and other production accidents,resulting in irreparable losses.Therefore,the practical study of valve gas leakage is of great significance of energy saving,emission reduction and safe operation in various fields of national economy.Aiming at the problem of internal leakage of valve in industry,this paper would take DN25 ball valve and globe valve as the research object,combine numerical calculation,experimental verification and theoretical calculation to carry out the following specific research:(1)The background and significance of the research,the importance of industrial process control valves in national economy and the hazards caused by gas leakage of valves were introduced.The necessity of quantitatively detecting gas leakage of valves by using new method was proposed.The research status of numerical calculation methods of multi-physical field coupling was expounded.It was determined that the acoustic-fluid-structure coupling method was used to study the gas leakage of valves in this project.(2)The basic theory of numerical calculation was introduced,which laid a foundation for numerical calculation of flow field and sound field in this paper.Comparing the numerical calculation with the experiment,the optimum position of the monitoring point based on the minimum error was determined.(3)CFD software was used to calculate the flow rate and flow resistance coefficient of the valve to verify the accuracy of the simplified model.The flow field of valve with gas leakage was numerically simulated.The steady and transient flow field characteristics of valve gas leakage with different leakage clearances and pressure ratios were studied.The leakage rate and sound sources excitation information was obtained by numerical calculation.The sound source excitation information was obtained to support the research of valve gas leakage sound field.(4)The sound field of the valve when gas leakage occurs was calculated numerically by using the acoustic software LMS Virtual.Lab,and the distribution law of the sound field radiated outside the valve system was obtained.The frequency spectrum law,total sound pressure level and amplitude distribution law and size of different leakage clearance and pressure ratio were compared and studied to provide data support for numerical fitting.(5)Acoustic tests for valve gas leakage was carried out by means of valve experimental gas path system,and the reliability of numerical calculation was verified by comparing the results of numerical calculation and theoretical calculation.The fitting formula for quantitative calculation was deduced,and the data obtained from numerical calculation was used to fit the numerical value,thus completing the quantitative research of gas leakage rate.(6)Through the above research,the numerical calculation method used in this paper could provide certain data support and reference for the acoustic detection technology of valve gas leakage,provide new research methods and ideas for on-line detection of valve gas leakage and quantification of valve leakage,and also provide certain data support for quantitative research between valve gas leakage and acoustic detection.