Patent ID: 8156739

Claim:
An adiabatic expansion heat engine, comprising: a piston chamber; a power piston moveable within the piston chamber for running on a working fluid in a high pressure state receivable from a heating exchanger and for exhausting said working fluid in a low pressure state; and a fluid pump for transferring the working fluid in the low pressure state back to the high pressure state of the heating exchanger, the fluid pump comprising: a pump piston; and an expansion chamber and a pump chamber which are disposed on opposite sides of the pump piston, and which have varying volumes as the pump piston is moveable between the expansion chamber and the pump chamber; wherein the expansion chamber and the piston chamber are fluidly communicated to define together a working chamber for adiabatic expansion of the working fluid therein during a downstroke of the power piston; the working chamber is controllably, fluidly communicable with the pump chamber during an upstroke of the power piston for compressing the working fluid in the low pressure state into the pump chamber; and when the power piston is at or near a top dead center (TDC) thereof, both the working chamber and the pump chamber are controllably, fluidly communicable with the heating exchanger so that pressures on opposite sides of the pump piston are equalized by the working fluid in the high pressure state metering from the heating exchanger, thereby balancing out the resistance to the working fluid being pumped, by a pumping action of the pump piston, from the low pressure state of the pump chamber back to the high pressure state of the heating exchanger.