Study on CO2 expander in CO2 transcritical cycles

More and more attention is paid to the CO2 expander to recover the expanding power and improve the cycle efficiency. The CO2 expanding process was analyzed taking a typical case as an example. As a result, expansion work has been divided into two parts: one is the work done mainly by pressure potential energy without phase change, the other is the work done mainly by volume expansion of two-phase fluid. According to the process, the ideal expander requirement is given. The difficulties in CO2 expander technology are raised and the research direction and solving problem methods are put forward. In addition, our research plan in three steps is provided. The arts state Of CO2 expander technology is analyzed. Furthermore, many types of expander are compared from the view points of leakage, vibration, noise, cost, size and efficiency. As a result, we chose rolling piston first to develop due to its low cost, wide application, and middle efficiency.