关键词: 二氧化碳, 跨临界制冷循环, 膨胀机, 自然工质, 并联机械手, 非均匀有理B样条, 轨迹规划, 振动

Abstract: The efficiency of CO2 refrigeration system is lower than that of traditional refrigeration systems using synthetic refrigerants. The expander can reduce energy losses in the expansion process, so the transcritical cycle with expander is adopted in order to improve the COP of the CO2 refrigeration cycle. In view of the current problems in the expander, a new two-rotor rolling piston expander used in transcritical CO2 refrigeration cycle is designed. This expander needs no special suction control equipment, whose first-stage cylinder connects with the suction pipe, and whose second-stage cylinder connects with the exhaust pipe, expansion space is formed between two cylinders. Theoretical analysis and design calculation of expander operation process are carried out to obtain the main structural parameters, and force and moment are calculated. Analytical result shows that the total moment of the first-stage rotor is always of a positive value in the expansion process and the total moment of the two rotors becomes negative when the expansion is about to end. The driving moment of the second-stage rotor is greater than that of the first-stage rotor before θ2, and after that the driving moment of the first stage rotor is greater.

Key words: Carbon dioxide, Expander, Natural working fluid, Transcrtical refrigeration cycle, Non-uniform rational B-spline, Parallel robot, Trajectory planning, Vibration