Study On The Flow Force Of Four-Way Rotary Spool Valve

Hydraulic valve is one of the most important component element in hydraulic system, whose performance determines the Security, reliability, accuracy and stability of hydraulic system. When the fluid flows through the hydraulic valve, the valve spool will get the reacting force, named the flow force, leading by the change in fluid flow direction and velocity. Flow force have significant effects on the operating force in valve to make the relationship between the input signal and valve spool displacement uncertain. It is also possible to cause the self-excited vibration of valve by flow force, resulting to damage the reliability and stability of hydraulic system. Especially in the condition of high pressure, large flow rate and high direction-changing frequency, flow force will have great effects on the controllability of valve and influence hydraulic system. That is why the flow force is an important factor to be considered in valve design and control. And also the flow force calculation equation is one of the basic equations to analyses hydraulic system characteristics. With a comprehensive analysis of the flow force research status in valve at home and abroad, up to present, the research on the flow force is focused in the fields of slide valve and poppet valve. However, it is very rare in rotary spool valve.This issue is the sub-topic of the project, named technology of rotation-spool-type high-power electrohydraulic vibrator, with the national natural science foundation support. In this issue, the new rotary spool valve is designed to realize high frequency vibration. And then the dynamic and static characteristics of the new rotary spool valve is researched to find out how and what it influences waveform, amplitude and frequency of electrohydraulic vibration system. Also the flow force, which influence the control characteristic of the rotary spool valve, is simulated and theoretically analyzed. In addition, the comprehensive test platform for the flow force measurement of rotary spool valve is designed and set up to carry out the experiment research. According to the relationships between different shape of opening face, different opening size, pressure and flow rate in rotary spool valve with flow force, summarize the influencing factors in rotary spool valve of flow force and gain the theoretical calculation formula for flow force in rotary spool valve. It can consummate the design criteria for the new type electro-hydraulic vibration system, and also provide theoretical guidance and design basis for development, design and research of such electrohydraulic vibration system.The main research works are as follows.1. The rotary spool valve is designed for new electrohydraulic vibration system by SolidWorks. The structure and working principle is introduced. How the new electrohydraulic vibration system has the advantage of high vibration frequency, step-less adjustable amplitude and controllable waveform through the change of structural parameters and operative parameters in rotary spool valve.2. The flow field in the rotary spool valve is simulated by Fluent. The dynamic and static characteristics of the flow field in the rotary spool valve is researched under the different structural parameters (e.g. the shape of opening face, the size of opening and the number of opening faces) and the different operative parameters (e.g. pressure, flow rate, and rotary speed). According to the simulation result, the influence on the flow coefficient, efflux angle and steady flow force by the different structural parameters and operative parameters in rotary spool valve is analyzed.3. According to the analyses of the flow simulation, the primary throttling and secondary throttling in the rotary spool valve are first proposed. And according to the characteristics of the primary throttling and secondary throttling, the theoretical calculation model of the equivalent flow area is derivatived under the condition of different shape of opening face and different size of opening. Finally, the theoretical calculation models of the steady flow force is established. The influence factors is analyzed according to the theoretical calculation model and the simulation result. Also the reasons for the difference between the theoretical calculation model and the simulation result is analyzed.4. The comprehensive test platform for flow force measurement is designed and set up. According to the data of pressure and flow rate, the flow coefficient is verificated by experiment. Also the flow force is verificated by experiment under the different structural parameters (e.g. the shape of opening face, the size of opening and the number of opening faces) and the different operative parameters (e.g. pressure, flow rate, and rotary speed).