In the field of fully mechanized coal mining equipment, the hydraulic valve used in the hydraulic support is an on/off directional valve. There are many problems caused by the valve such as large pressure shock and discontinuous flow control. Therefore, a novel two-position three-way hydraulic proportional valve suitable for high-pressure and large-flow conditions is proposed to overcome the above problems. The novel valve utilizes a two-stage structure and the displacement follow-up principle is adopted between the pilot stage and the main stage to meet proportional control. In this paper, a simulation model of the novel proportional valve was established after a simplified analysis of the structural principle. Its reliability and the feasibility of the design were verified by the test results under different working conditions. Then, the step response characteristics of the proportional valve under different strokes were predicted and analyzed. Nonlinear characteristics were presented, and the closing time was shorter than the opening time because of the influence of nonlinear flow force. Under different ramp signals, the displacement of the main inlet spool was always approximately equal to the displacement of the pilot stage. Then, the motion relationship between the pilot stage and the main stage was studied, and the influence of the structural parameters on the stability was analyzed.
An 800-L/min high-flow water cartridge poppet valve with the commonly used single feed channel was designed to meet the moving speed of the hydraulic powered roof support in the coal mine. Mathematical model was used to explore the dynamic displacement of the valve, and the experimental displacement was measured to verify the accuracy of the simulation value. However, an interesting phenomenon occurred that the experimental opening and closing time of the valve becomes longer and longer with the increase of flow, even vibration appears when the flow is up to 800 L/min, and the simulation error is also getting bigger. To find the reason and solutions, the computational fluid dynamics technology is used. It is discovered that the valve is subjected to radial imbalanced force that is not considered in the initial mathematical model, which leads to big simulation error at high flow condition. Then, the new mathematical model is proposed. The relative simulation error of the response time decreases to 11.7% from 33.3% in the opening process and decreases to 4.6% from 76.9% in the closing process at 800 L/min. A symmetrical dual channel is designed to improve the performance of the valve. The imbalanced force on the dual-channel valve is 63.9% lower than that of the original valve, and the corresponding opening and closing time decreases by 37.5% and 69%, respectively. Furthermore, a double channel valve with auxiliary passage is proposed for super high flow valves. The innovation of this study is correcting the mathematical model by considering the additional radial imbalanced force induced by the asymmetrical flow channel of the valve. It is of great help to successful design of the 800-L/min water directional valve. The case study systematically provides reference for design, failure analysis, and optimization of new products in fluid engineering.
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