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When exposed to viscous heating, hydraulic valve orifices experience thermal deformation, which causes spool clamping and actuator disorder. Quantitative research on thermal deformation can help reveal the micro-mechanism of spool clamping. In this study, miniature thermocouples are embedded into a valve orifice with an opening size of 1 mm to measure temperature distribution. An optimization algorithm based on measurement data (M-OA) for the thermal deformation of the valve orifice is proposed. The temperature and thermal deformation of the valve orifice are calculated through Fluent and Workbench joint simulation, with the measurement data serving as boundary conditions. Results show that, for a valve orifice with a valve wall length of 18 mm, when the temperature of the sharp edge is at 60 °C, thermal deformation measures 7.7 μm via observation and 7.62803 μm via M-OA, indicating that the M-OA method is reliable. The results of the joint simulation can be accepted because measurements of temperature reached an accuracy rate of 95%, and that of deformation reached 82.7%. A large drop in pressure led to a rapid increase in temperature, causing serious thermal deformation of the valve orifice. With an inlet pressure of 3 MPa, the temperature of the sharp edge reached 72.9 °C within 110 min, and radial thermal deformation can reach 8.3 μm. Such deformation poses great risk of spool clamping for a spool valve of Φ36 mm.

Hydraulic electric motor-pump is an integrated hydraulic power unit, raising rotational speed will further increase its power density. However, gaseous cavitation at high speed is the primary problem to be solved. In the present study, a new but simple centrifugal pressurization structure that integrated with the hollow shaft of hydraulic electric motor-pump was proposed to increase the inlet pressure of conjugated straight-line internal gear pump, and then to suppress gaseous cavitation at high speed. The numerical simulation is the main means of this work to investigate the gaseous cavitation characteristics of high-speed hydraulic electric motor-pump. In addition, a common conjugated straight-line internal gear pump model was developed as a reference to evaluate the pressurization effect of centrifugal tubes in terms of gas volume fraction. The simulation results present that compared with the significant increase of the suction chamber pressure of conjugated straight-line internal gear pump due to increasing the inclined angle of centrifugal tubes, the blocking effect of its inside wall to the fluid flow can be ignored. Under the same gas volume fraction in rotating volume, the rotational speed of hydraulic electric motor-pump is much higher than conjugated straight-line internal gear pump due to the pressurization effect of centrifugal tubes. On the premise of no obvious gaseous cavitation of centrifugal tubes, the recommended speed of hydraulic electric motor-pump is up to 13,000 r/min.