Research and Analysis of the Hysteresis Characteristics of a Large Flow Directional Valve

The 1000 L/min large flow hydraulic system for the hydraulic support used in a coal mine is currently a topic of great interest.The large flow directional valve is a key component for hydraulic systems, so the design of the 1000 L/min large flow directional valve is essential.The designed single-channel valve shows serious hysteresis characteristics in a 1000 L/min large flow condition, but it does not happen in a 16 L/ min small flow condition.Based on this phenomenon, the computational fluid dynamics (CFD) technology was used to simulate the flow in the valve.It was discovered that the single-channel caused unbalanced pressure in the annular region and on the surface of the valve spool, so the valve spool is subjected to great radial unbalanced force.Then a double-channel valve was designed to improve the pressure distribution.The simulated radial unbalanced force on the double-channel valve is 67.2% lower than that of the single-channel valve.The experimental results showed that the hysteresis characteristics also disappeared under the 1000 L/min large flow condition.Therefore, the conclusion can be drawn that the hysteresis characteristics of the single-channel valve is due to the radial unbalanced force caused by the unsymmetrical flow field.The results show that the maximum radial unbalanced force the valve spool can withstand is 170 N. Furthermore, symmetrical flow passages have to be taken into account in large flow conditions.This paper provides valuable references for the design of large flow valves.