In order to maintain the accurate and precise movement of the actuator of the hydraulic systems, it is necessary to guarantee smooth function of the fluid flow control valves. Concerning hydraulic valves, the spool type directional control valve has particular lock problem. The hydraulic lock occurs when uneven pressure distribution surrounding the spool in the clearance between spool and sleeve causes the spool to move sideways out of its centered position. And the contact between spool and sleeve causes to increase friction and eventually, the spool is blocked inside the sleeve. To reduce the possibility of hydraulic lock, peripheral grooves balancing uneven pressure distribution in the radial clearance is commonly applied to spool. Reynolds equation is commonly used to investigate the lubrication characteristics of the spool valve. However, some of assumptions used in Reynolds equation are not valid when cavitation occurs or fluid inertia is significant in spool valve. So, the study on the applicability and precision of Reynolds equation for spool valve analysis is needed. In this study, the differences between the results from Navier-Stokes equation and Reynolds equation are compared when the cavitation is considered. Frictional forces, lateral forces and leakage flow rate with various aspect ratio of groove are calculated. Besides, when the number of groove is increased, the forces and leakage flow rate are compared. Based on the comparison the applicability of Reynolds equation in calculating the spool valve is also discussed.

This content is only available via PDF.
You do not currently have access to this content.