Axial force indentation or protrusion

摘要

A reciprocating piston/barrel assembly, through which a fluid is capable of flowing, includes a piston 10 having a pressure face 16 separated from a downstream 15 face by a side surface 17. A barrel has an interior wall surface 13 defining a bore that is sized to slidably receive the piston. The assembly includes means producing a pressure differential between an upstream volume A and downstream volume B. The side surface and/or interior wall surface include at least one surface irregularity - indentation and/or protrusion - of sufficient size to increase flow resistance. In fluid flowing between the side and wall surfaces. The speed of fluid flow between the side surface and wall surface is faster than the speed of the piston. The axial force on the piston is increased by an increased pressure differential across the piston and because a portion of the fluid flow momentum is imparted to the piston. The may be used in poppet valves to hasten the activation rate of the valve.