| Spool valve is one of the basic structural forms of various control valves,and the flexible movement of the spool is the fundamental guarantee for the normal running of the control function of the valve.During the work process,the micron contaminated particles that follow the oil into the clearance of several microns to tens of microns may cause the spool clamping,friction and wear of motion pair,which will lead to the failure of the control function of the spool valve.Therefore,it is of great significance to study the trajectory of micron solid particles in the valve chamber and to deeply understand the transient characteristics of micron solid particles entering the clearance of spool valve for revealing the microscopic mechanism of spool clamping and developing highly reliable hydraulic control valves.In this paper,the spool valve is taken as the research object.The motion trajectory of micron spherical iron micron particles driven by liquid flow is simulated,and the transient process and probability of particles entering the clearance of spool valve are analyzed.The movement process of spherical particles in the enlarged two-dimensional model of the valve chamber and the clearance with pressure-equalizing groove is obtained by high-speed visualization experiments.The thesis is outlined as follows:At first,a two-dimensional valve chamber model with the micron scale clearance is established.The fluid-particle unidirectional coupling method is used to simulate the movement trajectory of micron spherical iron particles driven by steady-state liquid flow.The results show that the most micron particles in the oil move with the valve orifice flow;the ratio of the clearance height to the opening of the valve increases from 0.0067 to 0.4,and the probability of particles entering the clearance increases from 1% to 27%.When the opening of the valve decreases,especially in a small opening,the probability increases sharply.The greater pressure difference of valve orifice,the more particles enter the clearance.At the entrance of the valve clearance,the particles enter the clearance in a way that collide the wall slantingly and then rebound.Then,a two-dimensional clearance model of valve with a pressure-equalizing groove in micron scale was established to calculate the movement of spherical and square micron particles in the model by Fluid-solid coupling method.The results show that the particles are driven forward by oil in the clearance and pressure-equalizing groove,and accompanied by the rotation of the particles themselves.The rotation speed of the spherical particle is much lower than that of the square particle.The motion trajectory of the particles in the clearance fluctuates up and down,and the fluctuation amplitude of the trajectory of square particle is larger than that of spherical particle.Finally,according to the structure of the valve chamber,the two-dimensional enlarged models of the valve chamber and the clearance with pressure-equalizing groove are developed.The spherical iron particles with a diameter of 0.5 mm are used as tracer particles.A visualization experimental rig is built.The movement process of the particles released from the inlet channel and the movement process of the particles in the clearance model are recorded by using a high-speed camera.The experimental results show that the probability of particles entering the clearance at the inlet channel of the valve chamber is related to the position of the particles.When the particles enter the clearance,they collide with the clearance wall at the entrance of the clearance and rebound,and the particles follow the jet of the valve orifice after passing through the valve orifice.The corresponding simulation is carried out for the enlarged model experiment.It is found that the experimental results of the enlarged model are in good agreement with the simulation results through comparison,which means the validity of the simulation method,and further proves the reliability of the simulation results on the micron scale. |
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