Study on energy loss, temperature distribution and clamping mechanism of K, U, and V-groove spools based on thermocouple measurement and thermo-fluid–solid coupling simulation

The fluid heating of valve orifice will cause energy loss, uneven temperature distribution, thermal deformation and spool clamping, which severely dampen the reliability of hydraulic system. This paper designed the temperature measurement device using the embedded tiny thermocouples for K, U, and V-groove spools, built the experimental system with thermal imaging function, and analyzed the heating mechanism and deformation characteristics of spools by simulation. The study demonstrated that the thermo-fluid–solid coupling simulations are in good agreement with the experimental results under 3 MPa. The K and U-groove-spools show better energy-saving performance than the V-groove-spool. The energy loss rate of V-groove-spool in small valve opening of 1 mm can reach 2815.3 J/kg, which is 25.43 times as much as large valve opening of 5 mm. The change of the valve opening will directly affect the temperature distribution of the spool and the local high temperatures are always produced on the top, bottom, and sharp edges of the groove, as well as the stem near the groove. In the case of inflow, when the valve opening is 3 mm, the temperature differences of K, U, and V-groove-spools reach the maximum of 9.8 °C, 7.4 °C, and 10.7 °C, respectively, which means the maximum temperature gradient of the spool is generated under a certain valve opening. Additionally, the mechanism of spool clamping under outflow is not similar to the inflow, the outflow is more likely to cause spool clamping, and the U-groove-spool also shows higher risk of spool clamping than the K and V-groove-spools.