Diaphragm valves not only have simple structure, good sealing and small pressure loss, but also have the characteristics of corrosion resistance, impact resistance and wear resistance that traditional hydraulic valves do not have, so they are widely used in ultra-pure media fluid control systems (such as information technology, biomedical and new energy technology, etc.).Ultra-pure water diaphragm valve can not only achieve simple opening and closing function, but also achieve accurate flow control in the form of proportional valve. Its reliability, life and flow control stability have an important impact on the performance of the entire ultra-pure water fluid control system. Therefore, it is of great significance to study the relationship between diaphragm lifting height and flow and pressure of diaphragm valve.

Since the 1980s, how to use diaphragm valves to achieve ultra-pure water flow stability control has appeared as a new topic in the international field of vision. Scholars have conducted research on improving the service life of diaphragm valves, improving the accuracy of valve flow control and studying different driving methods.

In order to reduce the diaphragm stress and prolong the service life of the diaphragm valve, IRAJGashgaee et al. [3] made a hole in the connecting end of the piston and diaphragm, and pressed the diaphragm by means of air pressure, which could make the diaphragm close, reduce the generation of bubbles, and reduce the stress on the diaphragm. Compared with the valve stem before the improvement, the diaphragm would be subjected to centralized force. After the improvement, the life of the diaphragm is obviously improved. MLLER, FRITZ [4] designed an auxiliary pressure plate made of PFA(soluble polytetrafluroethylene) during the opening and closing process of diaphragm valve, and coated the direct contact area between the pressure plate and diaphragm with a very low friction coefficient to reduce the friction between the diaphragm and the pressure plate during the relative movement of the diaphragm valve. Thus, the elastic material of the diaphragm is prevented from local over-stretching, reducing the loss of particles caused by friction, and extending the service life.

In terms of the improvement of diaphragm valve driving mode, LEYS John et al. [8] designed a creep compensation mechanism. With the creep compensation mechanism, it is only necessary to keep the lower base and the upper cover to keep the long slide rod joint, which can shrink the axial length to a smaller axial length, not only slow down the creep, but also compensate the creep that has occurred. Limit the maximum displacement of the stem during rotation. PRATT Wayne L. Et al. [9] adopt double diaphragm to control opening and closing, and specially design a small convex on the shaft shoulder of the outer part of the diaphragm. This design is not only conducive to sealing, but also requires no additional sealing ring to seal, and the combination of small thrust bearing and spring is used to control the deformation and return of the diaphragm.

To sum up, researchers have conducted a lot of research on improving the stress state and tightness of the diaphragm, and improving the life and reliability of the diaphragm, but there are few studies on the driving mode and the flow characteristics of the diaphragm valve port. Therefore, the fluid-structure coupling method is used in this study to study the flow characteristics of diaphragm valves under different driving modes, and the research results have guiding significance for the accurate flow control of proportional diaphragm valves.