| The valve plays an important role in the piping system such as opening and closing,non-return,adjustment,etc.Once the leakage occurs,the production device cannot work as usual,if the leakage problem is serious,heavy pollution will diffuse or cause fire or explosion which would lead to serious production accidents.There are two kinds of leaks in the valve: internal leakage and external leakage.Both types of leakage are accompanied by the noise.Whether the valve has leakage by detecting the valve noise can be checked on the spot,but this test has been in a qualitative detection state.In this paper,based on the problem of the internal leakage of the valve,the quantitative relationship between the noise outside the valve and the leakage is studied,and a calculation method for estimating the internal leakage of the valve through the noise outside the valve is proposed.The method can realize the non-destructive,on-line and semi-quantitative detection of the valve leakage,which has strong engineering application value.In this paper,on the basis of the nozzle which the diameter is 0.2mm,0.3mm,0.4mm,0.5mm,and 0.8mm,and the pressure is 0.1MPa,0.2MPa,0.3MPa,0.4MPa,0.5MPa,0.6MPa and 0.7MPa,the experiment on the small hole injection of the time domain audio signal.At he same time,the frequency characteristics of the noise under various working conditions are analyzed through the Fourier transform.The results show that the frequency of noise generated by small hole injection is affected by many parameters such as aperture,differential pressure,and flow velocity,but there are clear correlation characteristics among these parameters.Based on the experiments,the numerical characteristics of the flow field,velocity,pressure,and density fields generated by the small hole injection were studied by numerical simulation.The sound pressure level and power spectral density curve at monitoring points were obtained by large eddy simulation(LES)and aeroacoustic models.The calculation results show that the flow field,velocity,pressure,and density fields generated by small hole injection are unsteady physical fields,and the noise and frequency distribution are basically the same as those obtained by MATLAB in the experiment.In order to understand the law of the valve leakage noise field under actualconditions,different opening heights of valves are studied to simulate the leakage of the valve.FLUENT and the professional acoustic software LMS virtual lab are both used to simulate the flow field and sound field of the Z11T-16T-25 gate valve at different leak opening degrees to provide data support for the acoustical quantitative detection of the valve inner leakage gas in the later period.Taking into account the production site,the flow of fluid in the pipeline and the valve,and the detection of sound outside the valve.This paper studies the relationship between the exterior noise of the valve tube and the internal noise of the valve,and establishes the theoretical correspondence between the noise outside the valve and the noise and flow in the valve.In order to verify the reliability of the calculation method,experimental measurements were performed between the valve noise and the valve leakage using a valve flow test bench and an SDT270 ultrasonic leak detector.Finally,the experimental results are compared with the settlement results and the previous numerical simulation results.Within a certain error range,the three results are consistent.In addition,the simulation results obtained by injecting the small hole into the formula are calculated,and the mass flow rate results obtained from the frequency and noise are compared with the numerical simulation results.Although the results of the two comparisons are somewhat in error,they are roughly consistent,which can further prove the accuracy of the formula. |
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