Patent ID: 7726129

Claim:
An engine comprising: a first positive displacement machine; a second positive displacement machine; an inlet duct connected to the first positive displacement machine; an intermediate duct connected between the first and second positive displacement machines; an outlet duct connected to the second positive displacement machine; a heater for raising the temperature and pressure of a gaseous working fluid in the intermediate duct; and a kinematic connection between the first and second positive displacement machines; the arrangement being such that, in operation of the engine, the first positive displacement machine causes a volume of the working fluid to flow through the intermediate duct to the second positive displacement machine, the heated and pressurized volume of working fluid drives the second positive displacement machine, and the second positive displacement machine drives the first positive displacement machine via the kinematic connection; the positive displacement machines including at least one orbiting piston, wherein the heater causes the working fluid pressure to rise equally in the first and second positive displacement machines, such that substantially no energy is required in the transfer of working fluid from the first positive displacement machine to the second positive displacement machine.