Study on Flow Characteristics of Helium Turboexpander with a Novel Intake Structure

The cylindrical volute intake structure possesses some advantages including convenient processing, convenient installation uninstallation and high machining efficiency. The helium turboexpander with this novel intake structure in a superconducting cryogenic device is investigated deeply in this study. Based on the established mathematical model and the corresponding numerical computation methods, the whole flow passage internal flow of the helium turboexpander is numerically simulated. And then the distribution characteristics of total pressure, static pressure, static temperature, relative velocity and total enthalpy in the cylindrical volute, nozzle, impeller and diffuser are explored, and loss mechanism of the internal flow is analyzed. The results indicate that the novel cylindrical volute intake structure has obvious pre-rotation effect on the inlet flow field of the nozzle, and this intake structure has little loss. In addition, the expansion effect in downstream components including nozzle and impeller is obvious, and the flow field changes uniformly. The overall efficiency of the turboexpander is up to 84.8%, which indicates that it is reasonable that the novel cylindrical volute is used as the intake structure of turboexpander.