Research On Throttling Groove Thermal Characteristics Of U-Hydraulic Spool Valve

Hydraulic valve is one of key control components of the hydraulic system. As science and technology advances, the requirements for the performance of the hydraulic valve are constantly improving. Hydraulic valves control the oil pressure, flow and direction in the system. Under these conditions, the performance of the hydraulic system controlled by the hydraulic valve plays an important role in the stability of the system, hydraulic control accuracy and reliability of the device. Accordingly, the fault and the performance advantages or disadvantages of the hydraulic valve will directly affect the entire hydraulic system. However, in the process of using hydraulic valves in medium and high pressure system, often appears valve jam phenomenon, causing the system does not work.The main reason is due to throttling effects when fluid flows through the spool valve port, which causes the temperature increasing of the oil, the thermal expansion of the spool and the decreasing of the matching clearance of spool and body. The phenomenon of valve jamming has a huge iMPact on the performance of hydraulic system and valve, which will increases the frictional resistance on hydraulic components relative moving parts, causing slow movements lightly, seriously causing hydraulic components relative movement completely stuck. These results seriously threaten to the security and stability of hydraulic system.Unreasonable design of the hydraulic spool valve will severely reduce the service life of hydraulic valves.The thermal deformation caused by temperature changing at valve port will affect the spool and sleeve matching clearance.Therefore,it is very necessary and meaningful for ensuring the reliability of the hydraulic system that researching hydraulic slide valve’s thermal characteristics in medium and high pressure system.The optimal design of hydraulic valves is imminent in high pressure and large temperature changing.This paper is mainly devoted to the problem of U-shaped hydraulic spool valve’s throttling temperature rises causing spool jamming. Using the research methods which combining theoretical analysis and numerical simulation, this paper in-depth studies the influence situation of U-shaped hydraulic spool valve throttling temperature changes.When expecting to solve the hydraulic valve stuck problems, in the aspects of hydraulic valve designs can get some theoretical significance and practical value of research results and conclusionsThe main contents are as follows.(1) Established the mathematical model of the U-hydraulic spool valve’s thermal characteristics:According to the basic laws of the hydromechanics, thermodynamics and mechanics of materials, and considering the relationships of oil viscosity, pressure and temperature, a mathematical model of the U-hydraulic spool valve was established about the throttling thermal properties. This model responses the temperature rise of the viscous throttling phenomenon accurately.(2) Simulated the hydraulic spool valve oil’s thermal characteristics:Considering the influence of the annular flow, established the three-dimensional simulation model of the hydraulic spool valve by using CFX and meshed. And then imported this model into the FLUENT software and calculated. Obtained the oil’s mass flow about the spool valve with the different throttle notch and achieved the distribution of the pressures, velocities and fluid temperatures with difference fluid pressures and openings. Analyzed the results and layed the foundation for further research on the thermal characteristics of the slide valve.(3) Studied the temperature characteristics of the hydraulic spool valve:Established the three-dimensional steady-state thermal analysis model about U-shaped hydraulic spool valve.Imported the oil temperature calculation results into this model and calculated thermal conductivity analysis of the spool valve respectively. Got the corresponding temperature distribution of hydraulic spool and the valve body under different notch structures, openings and pressures.(4) Researched the Thermal deformation of the hydraulic spool valve:Established the structural analysis model of the U-hydraulic spool valves and imported the steady-state thermal analysis calculation results into this model. Respectively analyzed structure thermal deformation on the spool and valve body. Got the relationship of thermal deformation of hydraulic spool and the valve body with flow, notch structures, openings and pressures. Proposed the concept of saturation flow Q饱 and got that the maximum radial deformation position of the spool was the position of the saturation flow Q饱 nearby.(5) Analyzed the impact of hydraulic spool valve’s shape parameters and materials on thermal properties:Basing on the analysis of thermal expansion theory, studied the iMPact of different hydraulic valve body parameters and materials on throttling temperature thermal deformation. Researched the influence of fluid viscosity and solid material on the hydraulic valve temperature and deformation conditions.Obtained the main factors affecting the results of thermal deformation hydraulic spool valve.Provides a theoretical reference for the hydraulic spool valve design and material selection.(6) Considering the hydraulic spool valve throttling temperature rising phenomenon, builds an experimental platform for testing the temperature field of spool valve. The test results data,verifies the hydraulic spool valve fluid viscous heating mechanism and the correctness of the finite element simulation model.The thesis proposes research methods about thermal characteristics of hydraulic spool valve for U-shaped throttling groove, lays a great theoretical and technological basis for further thermal characteristics analysis of the hydraulic system and, provides some applied research basis to hydraulic spool valve design and material choice.