Abstract: The sealing characteristics of the piston and cylinder in the SC-86 H high-energy liquid-jet hammer were studied based on computational fluid dynamics (CFD) analysis and laboratory tests. The effect on the leakage between the front chamber and rear chamber of the liquid-jet hammer were analyzed from the aspects of sealing length, annular gap, reciprocating motion velocity, angular velocity of the piston and the pitch and radius of the spiral groove on the outside surface of the piston. Results showed that little influence on the performance of the liquid-jet hammer was caused by the varying of sealing length, annular gap, angular velocity of the piston and the pitch of the spiral groove on the outside surface of the piston; The leakage between the front chamber and rear chamber is nearly proportional to the reciprocating motion velocity of the piston; While the radius of the spiral groove increased, the leakage increased remarkably; At the beginning of the forward and backward strokes, as the reciprocating velocity of the piston was quite slow, the leakage occupied a large proportion of the total liquid flow into the front chamber and rear chamber, instantaneously, the accelerated motion of the piston was influenced, especially when the diameter of the piston rod was larger to some extent, the piston would not be able to move backward easily, the performance of the liquid-jet hammer will got worse and even was unable to work.

Key words: computational fluid dynamics(CFD), high-energy liquid-jet hammer, piston, cylinder, leakage