Piston-type positive displacement machine with a pressure-adaptive piston-cylinder interface

A piston and cylinder assembly of a piston-type positive displacement machine, comprising:

• a cylinder having a uniform internal diameter;
• a cylindrical bushing press-fit against the inner surface of the cylinder and extending at least partially therein, the bushing comprising at least one circumferential groove formed on an outer surface of the bushing against the inner surface of the cylinder;
• a piston reciprocably disposed within the cylindrical bushing, generating a piston-bushing-cylinder interface, the piston and the bushing defining a diametrical clearance therebetween, the diametrical clearance defining a lubrication gap and a fluid-dynamic seal between the piston and the cylindrical bushing, creating fluid-dynamic buildup of pressure therebetween,
• the reciprocating action of the piston defines a cyclic motion including 1) a negative pressure phase wherein the piston is retracted from base of the cylinder thereby drawing in fluid from outside of the cylinder into the cylinder, and 2) a high-pressure phase in which the piston is pushed towards the base of the cylinder with fluid therein,
• a fluid channel between the at least one circumferential groove of the cylindrical bushing and a high pressure source.