Research On Dynamic Characteristics Of Cartridged Sequence Valve & Cartridged Check Valve

Cartridged valves are new-style hydraulic control elements applied to pressure control, flow control, directional control and proportional control system. The working principle is based on the concept that hydraulic control valve's port can be classified into fixed, changeable or controllable damping. Cartridged valve consists of insert element, forer-runner element ,insert mass and cover slab, all of which are highly generalized, standardized and modularized. Possessing the advantages as fast response, little leakage, simple structure, large-flow ability, reliability , good integration and small flow resistance, cartridged valve has been widely adopted to plastic machinery, metal forming machinery, casting machinery, metallurgy, machine tool, automobile and shipbuilding, etc.Based on research reported both home and abroad, the development, application and tendency of cartridge control technology were discussed and as well, the typical structure and working performance of two-way cartridge valve were studied. By port flow characteristic and kinematics analysis, the mathematical model of mechanics balance equation and flow balance equation was established. The influences of parameters such as orifice diameter, spring stiffness, inlet flow rate on the pressure recovery were explored by means of experiments and stimulation respectively. To study the stability of cartridged check valve under large flow, standard k～εand RNG k～εturbulent model is established. Comparing standard k～εmodel with RNG k～εmodel, a conclusion was got that RNG k～εturbulent model was more suitable in high strain and high curved streamline flow field. The distribution characteristic of pressure and velocity was simulated, whose result shows that negative pressure, results from spiral vortex formed at the outlet of valve, causes air to separate from oil and move into control chamber. Hence the orifice fails to take choking effect, and the spool of cartridge check valve is likely to oscillate. Relocating the oil entry point of control chamber was an effective solution to pressure oscillation. In the end, the experimental result that influences of spring stiffness on characteristic of pressure difference were analyzed with inlet flow rate changing.In chapter 1, the development, application and tendency of cartridge control technology were discussed and summarized. And then, the significance and main contents of the research were described briefly.In chapter 2, taking VICKERS' and Rexroth's products as example, typical structure and characteristics of two-way cartridge valve such as directional control valve,one-way valve,relief valve,sequence valve,flow-control valve were analyzed.In chapter 3, the fundamental structure of cartridge sequence valve was introduced; the mathematical models of cartridge valve were established based on the theory of control engineering, hydromechanics and kinematics. With AMEsim software etc., simulation was done in case that the load of the valve outlet lost suddenly, and variations of valve spool displacement, valve spool control chamber pressure and valve inlet pressure during valve inlet pressure recovery process were simulated. Furthermore, experiment on pressure recovery process under different conditions were accomplished, and the influences of parameters such as orifice diameter,spring stiffness,inlet flow rate on the pressure recovery were investigated.In chapter 4, based on the theory of control engineering, hydromechanics and kinematics, a RNG k～εturbulent model which suits to flow characteristic of cartridged check valve was established and two types of model of closed wall function were introduced. By Fluent flow-field analysis software ,the distribution characteristic of pressure and velocity was simulated, which well explained the phenomenon that cartridged check valve' spool ape to oscillate under large-flow , The result shows that negative pressure, results from spiral vortex formed at the outlet of valve, causes air to separate from oil and move into control chamber. Hence the orifice fails to take choking effect, and the spool of cartridge check valve is likely to oscillate. Relocating the oil entry point of control chamber was an effective solution to pressure oscillation, which is confirmed by both theory and engineering practice.In chapter 5, all achievements of the dissertation are summarized and further research work is put forward.