Simulation and experiment on the flow field in fit clearance for a large size spool valve

It is very important to design the fit clearance between the spool and pocket of a spool valve, because oversize clearance will bring large leakage through the fit clearance and undersize clearance will lead to hydraulic seizure of the spool, especially for a large size spool valve. In order to develop a large size spool valve for a high speed winch, based on computer simulation, this paper analyzed in detail maximum pressure differential in fit clearance at the two sides of eccentric spool with number of compensating grooves, then discussed the leakage through the fit clearance. According to the results of simulation, a large size spool valve with port diameter 60mm is designed and manufactured, the experiment shows that this large size spool valve acts reliably, the leakage through its fit clearance is very small as the results of simulation, and there is no spool seizure.