Reciprocating cryogenic liquid pump is the cryogenic liquid (such as liquid oxygen, liquid nitrogen, liquid argon) pressurized filling bottles or pipes to oxygen at low temperature equipment, with its simple structure, stable and reliable operation, safe and economical, low speed And other features by users of all ages. The suction valve and the discharge valve in the reciprocating hydraulic pump are at the heart of the pump. Therefore, the service life of the discharge valve is one of the important factors that affect the performance of the reciprocating pump. The basic requirements of the valve are: (1) a good seal when closed, no liquid stringing. (2) The opening and closing of the valve should be coordinated with the movement of the piston, otherwise the leakage of cryogenic liquid due to the hysteresis of the valve will reduce the volumetric efficiency of the pump. (3) require the valve to work smoothly, especially when the valve is closed, there is no serious impact phenomenon, the guide should be flexible, no stuck phenomenon. (4) cryogenic liquid flow through the valve, the resistance loss should be small. (5) Simple structure, better processing technology, easy maintenance. (6) to have sufficient strength and stiffness, wear resistance is better, longer life. A valve movement law According to the balance of the valve plate force and fluid mechanics Bernoulli equation and fluid flow through the valve gap (orifice) when the flow formula can be drawn valve lift hv, speed V and acceleration a and angle Φ relationship. It can be seen that the valve speed is positive and the acceleration is negative in the range of Φ from 0 to π / 2. When the valve is rising, it is a kind of slow motion. In the range of Φ equal to π / 2 to π, the valve flap descends, the valve speed is negative, and the acceleration is also negative, indicating that the valve flap is a kind of growth movement when it falls, which will strengthen the impact on the valve seat. Due to the fact that the valve is constantly moving during operation, there is a Weisterthal phenomenon in which the valve does not rise at the start of the discharge stroke. The hydraulic valve does not start to move until it lags behind the piston , In the discharge stroke at the end of the moment, the valve has not closed, stay at the height of the lift hmax, after a lag angle, the valve was closed. 2 types and structure of the valve There are many types of discharge valve, such as flat valve, ring valve, cone valve, spherical valve, but the opening and closing of the force, are relying on the valve before and after the liquid pressure difference to carry out . Now compare two typical structural forms.
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