The pulse tube refrigerator(PTR)is a promising small-scale cryocooler.This paper first briefly introduces the history of the pulse tube refrigerator.It has pointed out that technology improvements and theoretical developments of the pulse tube refrigerator closely relate with the internal streaming effects.Then the discovering history and classification of the streaming or DC(direct current)flow effect are summarized.It proposes for the first time that the physical significance of the streaming contains the driving mechanisms and the transport mechanisms.It demonstrates that the driving mechanisms are the asymmetry of fluid flow and temperature while the transport mechanisms are a loop or vorticity,which transmits nonlinear dissipations.The important advancements have been made over the past two decades all over the world in research of streaming of the pulse tube refrigerator including Gedeon DC flow,Rayleigh streaming,the third type of DC flow and the regenerator circulation.With regard to Gedeon DC flow,theoretical and experimental analyses have been made and different suppression methods are summarized.In the aspect of Rayleigh streaming,it mainly focuses on the analytical solution of the second-order mass flow and the research of tapered pulse tubes.In particular,limited research on the third type of DC flow and regenerator circulation is presented.The experimental measurement techniques of streaming also are summarized.Finally,this paper briefly discusses the key scientific and technical issues of the current research,and foretells the future development trends of streaming research in PTR.
