The distribution efficiency of the check valve directly affects the performance of the reciprocating pump. The flow coefficient is an important evaluation criterion for the flow capacity of the valve port, and it is of great significance to the design of the valve structure and even the control of cavitation. The traditional design uses flow coefficient as a fixed value, however, the flow state and flow coefficient will change during valve movement. In this study, a three-dimensional transient computational fluid dynamic model for high-pressure and large-flow reciprocating pump valve is established. The dynamic grid simulation method of coupling for the valves and plunger is innovatively proposed, and experimental verification was carried out. The flow state and pressure characteristics for the suction valve under high outlet pressure are analyzed, and the change rule of the suction coefficient is found. The research results show that the initial pressure of the plunger cavity prolongs the negative pressure duration of the plunger cavity when the valve is opened and increases the risk of cavitation of the valve. During the process from valve opening to maximum lift, the suction coefficient first increases and then decreases, and finally remains between 0.5 and 0.6. When the valve lift is large, two-stage throttling occurs, and the flow state will change from cylindrical jet on the lower surface of the valve disk to annular jet, which is beneficial to improve the suction coefficient.

In this article, a geometrical model of different microtextures is established for an axial piston pump valve plate. A finite differential method was used to solve the Reynolds equation for the oil film thickness and pressure, which were simulated under different microtextures. The influence of microtexture shape and structure on performance was studied and optimal parameters sought. Different convergence gaps are formed by different microtexture radii, and they produce different hydrodynamic effects. The lubrication characteristics of the valve plate are better when a microtexture is used and are influenced by the type of microtexture. We reached the following conclusions: (1) The lubrication characteristics of the valve plate are influenced by different microtexture parameters and can be improved by optimizing the microtexture parameters; (2) There is an optimal parameter combination when adding microtexture with three shapes (spherical, cylindrical and square) and the optimal dimensionless oil film pressure lubrication characteristics can be obtained; (3) The degree of improvement in the dimensionless oil film pressure lubrication characteristics was (listed from highest to lowest): micro-hemispherical texture > micro-cylindrical texture > micro-square texture.

This paper focuses on the contaminated friction of fit clearance between the spool and valve body to explore the influence principles of clamping stagnation phenomenon. From the perspective of surface morphology and size of particulates in the clearance, designing and manufacturing the valve body, rough spool, conical spool, and standard morphology spool, the test bench was built up and the curves of real-time contaminated friction in the movement of spools were obtained through experiments. The curves show that the contaminated frictions have a feature of pulsation; meanwhile, the stagnation-sensitive size of particulates is between 0.7 and 0.9 times that of clearance. Compared to the ideal morphology spool within the range of sensitive size, the contaminated fiction of rough spool is increased, whereas the lower limit of stagnation-sensitive size range of particulates on conical spool is decreased. The contaminated friction is gradually increased on cis-conical spool but increased first and then decreased on invert cone spool.

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.

The separation of bubbles in a gas–liquid cyclone is complicated. A combination of numerical simulation and visual experimentation was considered apt to reveal the microscopic mechanisms of bubble flow. First of all, cyclones with different structures were numerically simulated. The calculation results show that the larger the diameter of the exhaust port, the better the bubble flow effect. When the exhaust port diameter was 24 mm, the gas discharge efficiency was 8% higher than that with an exhaust port diameter of 16 mm. The sequence of the bubble flow effect of a four-structure cyclone was obtained, and the gas discharge efficiency of the cyclone with a rectangular inlet was 7% higher than that of the trapezoidal inlet. Finally, a visual experimental platform was built to compare the rectangular inlet cyclone and spiral inlet cyclone with the best bubble flow effect. In accordance with the simulation numerical calculations, the bubble flow effect of the rectangular inlet cyclone was better than that of the spiral and trapezoid inlet cyclones, and the rectangular inlet in the middle was better. This article provides a specific theory and experience to guide further research on the separation mechanism, flow field characteristics and structurally optimal design of gas–liquid cyclones.

The intrusion of micrometer-sensitive contaminant particles into the clearance of sliding valves within hydraulic fluids is one of the root causes of valve sticking and reliability issues in hydraulic systems. To reveal the transient process and characteristics of particle intrusion into the clearance process, this paper proposes a numerical method for fluid–particle one-way coupling and verifies it through experimentation. Furthermore, a numerical simulation of the motion trajectory of spherical iron particles inside the valve chamber was conducted in a two-dimensional flow model. It was discovered that in a steady-state flow field with a certain valve opening, micrometer-sized particles in the valve chamber’s hydraulic fluid mainly move with the valve flow stream, and the number of micron particles invading the slide valve clearance and the probability of invasion is related to the slide valve opening and differential pressure. When the slide valve opening decreases, especially in the small opening state, the probability of particles invading the slide valve clearance will increase dramatically, and the probability of invading the clearance is as high as 27% in a valve opening of 50 μm; the larger the pressure difference between the valve ports, the more the number of particles invading the slide valve clearance increases; the particles in the inlet of the slide valve clearance are more prone to invade the slide valve clearance, and invade in an inclined way, touching the wall and then bouncing back. These findings are of great value for the design of highly reliable hydraulic control valves and the understanding of the mechanism of slide valve stalls and provide an important scientific basis for the optimization and improvement in the reliability of hydraulic systems.