Visualization Experiment of Single Particle Motion in Model of Spool Valve Clearance

Sensitive solid particles entering the spool valve clearance may cause friction of the motion pair, and even induce clamping of the spool valve, which seriously affects the reliability of hydraulic system. In order to reveal the micro-mechanism of spool valve clamping caused by sensitive particles, the motion characteristics of single particle in clearance of spool valve are investigated. According to the prototype of spool valve clearance with pressure-equalizing grooves, a magnified visualization model is built, and some regular cubic particles are produced. Using visualization experimental method, the instantaneous movement processes of several particles in the model flow field are recorded by high-speed camera. The results show that the particle rotates continuously when it move along the clearance flow field. It's also obtained that when several particles move into the magnified groove, their distance gradually decreases, and approach each other near the outlet of the groove, then they strike the groove wall. At this time, different motion trajectories appear, most of the particles gradually sink into the bottom of the groove, while others roll out of the groove and enter the clearance again.