Fundamental motion relation of different solid phase shifters of pulse tube cryocooler

Abstract

Warm displacer type Stirling pulse tube cryocooler (SPTC) has demonstrated very promising benefits from its strong phase shifting and work recovery functions. Gas driving displacer (the passive displacer), linear motor driving displacer (the active displacer), and moving plug with orifice could be regarded as different operation modes of the general warm displacer. This work intends to fully understand the fundamental motion relation of different solid shifters for designing an effective warm displacer. Hence, starting from the basic momentum equations, the mechanism of the piston motion was studied theoretically, and the function of moving plug with orifice was mentioned in passing. It shows that the gas driving displacer can make the same optimal performance as the linear motor driving displacer does. In case of the mechanical problem of the displacer in the initial design, the gas driving displacer with orifice could be a backup to improve the performance of the SPTC. Based on the theoretical analysis and formula deduction, a simple simulation briefly displays the relationship between the displacer rod diameter ratio, displacer piston mass, and gas spring stiffness for a fixed micro SPTC. A general design method for the warm displacer was worked out eventually and could be extended to the linear compressor design.