Research On The Dynamic Characteristics Of The Large Flow And High-water Based Directional Valve

The electro-hydraulic control system of the hydraulic support is an important symbol of the advanced mining technology. The large flow electro-hydraulic directional valve is one of the key components of the system. The reliability of the valve is directly related to the safety and efficiency of the production. The advanced design tools and the corresponding technology are not recognized by the domestic researchers, so the basic research is very weak, such as the shock and vibration mechanism, the influence and factors haven’t been revealed through theoretical analysis or experimental research. Mostly the problem is solved with experience. However, there is a great need to increase the flow and pressure of the hydraulic system with the development of the mining technology, therefore, it is necessary to carry out the basic theoretical research of the high pressure and large flow high-water based directional valve, in order to provide effective methods and theories when the new valves are designed.Firstly the research works of the counterparts are reviewed. The features and development trend of the directional valve used on the hydraulic roof support are analyzed combined the mining technology. In addition, the existing failure phenomina are also analyzed, so the key technical issues of the directional valve are summarized.The conventional integrated cartridge valve is a single-channel valve, which is easy to subject to the radial unbalanced force. The CFD technology is applied to study the mechanism of producing radial unbalanced force on the valve spool, the relationship between the radial unbalanced force and the flow is also revealed. A predition is presented that the hysteresis characteristics may occur on the valve under large flow conditions. Then a double-channel structure is proposed. The simulation results indicate that the unbalanced force on the double-channel valve is much lower than that on the single-channel valve. The experimental tests are carried out under small flow condition and large flow condition. Results show that the single-channel valve shows great hysteresis characteristics under the large flow condition but the double-channel valve does not. However, there is no difference between the two valves under small flow condition. Accordingly, the prediction is verified correctly. What’s more, the threshold of the radial unbalanced force the valve spool can withstand is confirmed by the combination of simulation results and experimental resuluts.For the fracture phenomenon of the valve, the multi-disciplinary system simulation software AMESim and the mechanical impact stress analysis software ANSYS/LS-DYNA are combined together to research the mechanical shock characteristics of the valve sleeve. The effects of the valve structure and the constrained form toward the stress wave progation are also investigated. Results indicated that the valve failure is due to the fatigue, the stress amplitude of the valve sleeve can decrease greatly by decreasing the buffer damp diameter. The integrated structure has a better ability to withstand the impact loads. The mechanical shock occupies a large propotion in all the shock properties in these large flow valves, so it can not be ignored in large flow hydraulic systems.For the low viscosity characteristics of the high-water based fluid, the design principle of the internal velocity of the valve is determined. The CFD technology and the visualization technology are used to simulate the fuid flow characteristics inside the valve. The vortexes and cavitation are identified. Then, the radial holes and the axial flow passage are optimized. Two control volumes are used to derive the flow force formula, which is corrected according to the CFD simulation results in order to lay the foundation for the dynamic modeling of the directional valve. The mathematic model of the valve is established and the block diagram is applied to study the dynamic characteristics of the valve. The effects of the mechanical stop, the spring constant, the control diameter of the main valve, the outlet pressure and the flow toward the dynamic characteristics are researched, so the suitable values of these parameters are determined and verified by the experimental tests.The structure and the proportional control method for the large flow directional valve used on the hydraulic roof support are discussed preliminarily. In this paper, the displacement-electrical feedback scheme is used and the C-type hydraulic half-bridge is applied as the pilot valve to control the pressure of the control volume of the main control valve. Then the effects of the valve opening time, the form of the valve displacement curve and the form of the valve port toward the hydraulic shock are investigated.In this paper, the computational fluid dynamics, mechanical dynamics theory, multi-disciplinary system simulation methods and the modern testing techniques are used. The mechanical shock and vibration characteristics and the hysteresis characteristics of the large flow valve are researched combined the theoretical calculation, simulation and experiments. The values of the key parameters are optimized and the 1000L/min large flow directional valve is successfully developed.