DESCRIPTION OF A HIGH-EFFICIENCY FLOATING-PISTON EXPANDER FOR A MINIATURE CRYOCOOLER

摘要

A cryogenic expander employing low-temperature helium is under development. This expander employs a floating piston operating between a warm variable volume and a cold variable volume to expand the working fluid. The piston's position is dynamically regulated through an active control routine that actuates electromechanical valves. These valves control helium flow in and out of the variable volumes. Throttling through the warm-end valves regulates the piston's velocity. The cold-end valves, operating at cryogenic temperatures, are of novel design to achieve system miniaturization and high efficiency at range of operating points.