RESONANT FREE-PISTON STIRLING ENGINE HAVING VIRTUAL ROD DISPLACER AND DISPLACER LINEAR ELECTRODYNAMIC MACHINE CONTROL OF DISPLACER DRIVE/DAMPING

摘要

A new and improved resonant free-piston Stirling engine and method of operation employing a novel virtual rod displacer is described. The engine has a reciprocal movable displacer that is exposed to a working gas pressure wave periodically produced within the Stirling engine to drive a working member (power piston) from which work is derived by the engine. A rod is secured to and reciprocally moves with the displacer within the Stirling engine and has a rod piston area formed on the end of the rod remote from the displacer with the rod piston area also being subjected to the working gas periodic pressure wave. Suitable support bearings are designed within the Stirling engine housing for reciprocatingly supporting the displacer and rod assembly within the Stirling engine with a set of opposed acting gas springs being provided to act on the displacer end and rod assembly area end of the displacer and rod assembly so that a spring-mass system is formed having a natural frequency of oscillation substantially the same as the desired frequency of operation of the Stirling engine. One end of the displacer is designed to have a greater effective area acted upon by the gas contained within the engine than the effective area of the opposite end whereby the unbalanced areas of the opposing displacer ends create a differential force when acted upon by a periodic pressure wave, causing reciprocating motion of the displacer and virtual rod assembly. In the preferred embodiment a displacer electrodynamic machine is provided for selectively driving or loading the displacer and rod assembly to thereby control the stroke and/or phase angle at which the displacer and rod assembly move relative to the output power piston or work member.