An improved structure was suggested by introducing high pressure gas into the vane slots to ensure the contact between the vane tip and the cylinder wall in a rotary vane expander. The theoretical analyses and calculations were performed to obtain the optimum parameters of the improved structure. The experiments were conducted on the improved expander prototype with and without introducing high pressure gas under the same working conditions to explore the influence of the improved structure on the vane movement and thermodynamic process of the expander. The results show that the expander with the improved structure could run steadily in a trans-critical CO

2

refrigeration system. The contact between the vane tip and the cylinder wall improved well and the leakage between each chambers decreased. The maximum work output was 682 W

and the maximum volumetric efficiency was 35.1%

and the maximum isentropic efficiency reached 49.8% when the rotate speed was 1 200 r/min.