Rsearch On The Thermodynamic Characteristics Of Large Flow Water Pressure Proportional Relief Valve Based On CFD

Water pressure proportional relief valve used in hydroforming process can determine the pressure and flow rate of the system,and its performance will determine the working performance of the whole hydraulic system,thus affecting the forming quality of parts.During the operation of water pressure valve,water medium will produce cavitation and damage the solid structure surface such as spool.The viscous heating phenomenon of the fluid will cause the thermal expansion of valve sleeve and spool to make the fit gap larger or smaller,resulting in spool stuck or leakage increased,so it is necessary to study the working state of the water pressure valve.In this paper,two numerical simulation methods,CFD and FEM,are used to calculate and analyze the fluid flow characteristics and thermal deformation of spool and valve sleeve in two structural valve chambers under different working pressure difference,valve opening and fluid temperature.(1)The flow of fluid in the valve chamber follows hydrodynamics,while the temperature rise and deformation follow the thermodynamics and material mechanics.Based on these theories,the mechanism of fluid temperature rise is expounded,and the coupling mathematical model of flow field,heat transfer and deformation is established.(2)The simulation model of hydraulic valve is established.After dividing the grid and verifying its independence,the distribution of flow field pressure,velocity,cavitation and temperature under different working pressure difference and opening is obtained by CFD calculation.The research on these distribution shows: significant pressure drop occurs at conical valve port,which makes flow velocity increase and cavitation occur;the temperature rise of the fluid is greater in the structural change areas such as overflow hole of valve sleeve and groove bevel of spool.The change of working pressure difference and opening of valve port has an obvious effect on cavitation,and temperature rise of fluid also changes accordingly.(3)The thermal analysis and structural deformation analysis model of spool and valve sleeve under steady state are established.The temperature distribution of spool and valve sleeve and overall deformation caused by the thermal expansion of spool andvalve sleeve are obtained by loading calculation of coupling data.The change law of solid temperature distribution and thermal deformation under different working pressure difference and valve opening are studied by combining with flow field analysis.The research results show that the areas with higher solid temperature are concentrated on outlet side wall surface,and the areas with larger deformation are also concentrated on this.In addition,this paper focuses on the deformation law of the mating surface of spool and valve sleeve,and obtains the deformation change of the fitting by increasing the inlet fluid temperature,so as to estimate the maximum fluid temperature that the spool and sleeve can bear without being stuck.In this paper,the flow field and solid thermal deformation of water pressure proportional relief valve are analyzed and studied,which has a certain practical engineering significance.