A pump includes a stationary pump housing having a central longitudinal axis
and
a housing chamber, a rotating pump shaft extending through the pump housing and
into the housing chamber, a rotating barrel fixed to the pump shaft and including
a plurality of pump chambers, and a plurality of rotating and reciprocating pump
pistons. Each pump piston is at least partially contained within a respective pump
chamber. A fluid delivery control assembly is provided to selectively vary the
amount of fluid delivered by the pump. At least one pressurized fluid pool is located
between a portion of the rotating barrel and a portion of the pump housing. The
pressurized fluid pool may be located along an end surface of the rotating barrel
and/or along a side of the rotating barrel.
