Integrated pumping and/or energy recovery system

Abstract

An energy-recovery pump or pumping system includes, in a double action embodiment, first and second cylinders wherein respective first and second pistons, mounted to a common reciprocating piston shaft, are mounted for reciprocating motion. A hydraulic pump drives the common piston shaft back and forth in accordance with a prescribed velocity profile that includes acceleration, constant velocity, and deceleration periods, as well as a short dwell time at the conclusion of each stroke during which the shaft and pistons remain stopped. Each piston divides each cylinder into first and second working volumes. Input and output valves connect a source of fluid with an output header through half of the working volumes in such a way that the fluid is received within whichever working volume is expanding and is pumped from whichever working volume is contracting, as the pistons move back and forth within their respective cylinders during a pump cycle. Energy recovery valves selectively connect a second fluid under pressure with whichever of the other half of the working volumes is expanding so that the pressure force associated with the second fluid assists in moving the respective piston during the appropriate portion of the pump cycle. The second fluid is discharged from the respective working volumes through discharge valves as such working volumes contract during the pump cycle. The energy recovery and discharge valves are switched from one position to another only when the pistons are stopped for the short dwell time at the end of a forward or backward stroke.