The Research Of Temperature Rise By Throttling And Thermal Deformation Of Hydraulic Valve

Hydraulic valve is the key component in fluid transmission and control technology, which controls the fluid pressure, flow rate and flow direction, thus its properties have a decisive influence on the whole hydraulic system. Hydraulic spool valve and poppet valve are two kinds of the basic configurations. Due to the matching clearance of the spool and cover is small, there are problems such as clamping, abrasion and leakage during the process of using. In this thesis, theoretical analysis, numerical simulation and experimental study are used to nvestigate the changing of the performance of valve which caused by the temperature rise. A vibration reduction method is put forward to solve these problems. The numerical results showed that the temperature distribution of fluid and solid was nonuniform in the spool valve. The temperature of the jet flow closed to the solid wall was higher,and the temperature in the center of the jet was lower.In addition, the highest temperature are located on the solid wall near to the orifice and on the wall in valve chamber impacted by the jet. The maximum deformation in spool and valve body caused by the temperature rise could come up to several microns,and there was an overall bending deformation in the spool and valve body. These two types of deformation could directly lead to the phenomenon of spool clamping.The main content of this thesis:In chapter 1, the background and significance of this thesis is presented. The history and current research progress on temperature fluid and structure deformation of hydraulic valve are reviewed. Lastly, the main research subjects are presented.In chapter 2, the theory of temperature rise in fluid flow and the influence of temperature to the structure deformation are put forward. And the trending of the deformation in valve caused by the temperature change was discussed.In chapter 3,in deferent pressure, opening and valve port, Three-dimensional flow field,temperature field in spool valve with notches and without notches,valve cone and Damping hole was calculated by using software FLUENT and ANSYS, which obtained the pressure distribution, velocity distribution and temperature distribution. The results shows: The temperature of fluid was nonuniform in the spool valve. The temperature of the jet flow closed to the solid wall was higher, and the temperature in the center of the jet was lower. And the highest temperature is located on the solid wall nearest to the jet. This shows that fluid temperature rise is mainly caused by friction between each high speed fluid, low speed fluid and the wall.In chapter 4, Three-dimensional temperature field and thermal deformation of the spool and valve body were analyzed by software ANSYS. The boundary temperature of the fluid-structure interaction in fluid field analysis is applied as a plane load to the model of the spool and valve body, thereby solving the thermal field of the solid. The results shows: Temperature distribution on the body and spool is uneven and asymmetric, and the highest temperature is located on the solid wall near to the notch and on the wall in valve chamber impacted by the jet. The shape of notch and openings of valve have a substantial effect on temperature distribution in the valve.The thermal deformation of spool and valve body mainly reflected on local larger diameter of the spool and local smaller diameter of the body hole. The maximum deformation could come up to several microns, and there was an overall bending deformation in the spool and valve body. As a result, the deformation may lead to spool clamping.At the end, some conclusions in this thesis are summarized and the future research proposals are suggested.