Visualized Study On Flow Field And Pressure Pulsation Characteristics Of Valve

The flow inside the valve is complex,and there are many hydraulic phenomena that are not conducive to the safety of the system.The unsteady flow inside the valve will also cause the corresponding pulsating pressure phenomenon which will cause the vibration of the valve piping system and its equipment,and affect the safety of the system.The study on the characteristics of flow field and pulsating pressure inside the valve is helpful to reveal the law of flow and pulsating pressure inside the valve,provide guidance for the optimization of valve design,and have great significance for the safe operation of the valve.In this paper,the transparent plexiglass valve is used as the experimental body,the PVC pipe is used to design and build the PIV visualization experimental circuit,and the PIV optical system is designed.PIV system is mainly composed of continuous laser and continuous high-speed camera.In order to improve the accuracy of flow field measurement,the location of the valve was photographed in different areas,and the accuracy of flow field measurement reached millimeter level.The measurement scheme of fluctuating pressure is studied,and the experimental system for simultaneous measurement of flow field and fluctuating pressure is built.The flow field and fluctuating pressure characteristics in the valve with different flow rate and valve opening were studied.PIV post-processing algorithm is optimized based on python,GPU accelerated processing is realized based on CUDA computing platform,and PIV and pulsating pressure data post-processing software are developed based on optimization algorithm.The results show that: the single cross-correlation calculation method of traditional PIV algorithm is accelerated and improved.The method of multiple iterations is adopted,and the traditional single cross-correlation calculation method is compared with the optimized post-processing results.It is found that the maximum error of flow field calculation is less than 5%,which meets the requirements;the post-processing speed can be increased by eight times after GPU acceleration.Based on PIV technology the flow field experiment of the valve is carried out.The results show that different flow rates have no obvious effect on the flow field distribution of each position of the valve.The results show that there is a low-speed dead zone in the reverse arc region of the valve,and the flow condition in this region is not improved with the increase of flow rate,and the secondary flow appears under the action of large shear stress gradient and centrifugal force;there is a large-scale vortex structure caused by violent flow separation in the valve core position,and the vortex structure does not change with the increase of flow rate,and the vortex center position moves in a small range;changing the valve opening has no effect on the upstream flow of the valve inlet.The main flow at the outlet of the valve is concentrated on the upper wall,and there is a low-speed flow disorder in the middle of the upstream position of the outlet,and the flow condition does not improve with the increase of the flow rate.Different valve opening has no significant effect on the upstream flow field distribution;With the change of valve opening,the position of large-scale vortex structure in the valve core area changes,and the flow pattern is inconsistent with different full opening flow rate;With the decrease of the opening,the outlet mainstream position moves downward,the large-scale vortex structure appears at 25% opening,and the turbulent kinetic energy is the largest;when the opening is 15%,the flow congestion occurs,and there is no obvious mainstream stagnation;FFT and PSD analysis show that there is a natural frequency flow field characteristic frequency in the flow field,and the dominant frequency signal increases with the increase of the flow rate With the change of valve opening,no new characteristic frequency appears,and the main frequency amplitude of 25%opening is the largest,which is consistent with the flow field results.In this paper,the flow field and fluctuating pressure characteristics inside the valve are comprehensively studied and analyzed by means of experiment,which provides an important reference for the numerical calculation and optimization of valve vibration reduction and noise reduction design.