工质与叶轮传热对超临界二氧化碳向心透平气动性能与流动特性的作用机制

In ordcr to investigate the action mechanism of heat transfer between working medium and impeller on aerodynamic Performance and flow characteristics of radial inflow turbines with supercritical carbon dioxide, the three-dimensional numerical Simulation of flow and heat transfer in main flow and wheel back clearance of a turbinc is carricd out by solving the Reynolds-averaged Navier-Stokes equations. Based on the geometrical model of a radial inflow turbine with supercritical carbon dioxide with a cyclc Output of 150 kW, the effects of heat transfer between working medium and impeller on turbine aerodynamic Performance, windagc loss in wheel back clearance and flow characteristics in seal clearance arc comparativcly studied using conjugate heat transfer method. The results show that under conjugate heat transfer condition, both the turbine shaft power and the isentropic efficiency generally decrease, whcrc there is a minimum reduction with the temperature variations at the shaft. The pressure side vortcx at the rotor blade leading cdge and the leakage vortex at the tip clearance can strcngthcn hcat transfcr bctwccn the main flow and the impcllcr, and the high temperature zonc locally appcars at the rotor blade leading edge and the blade root with a ccrtain temperature gradient. At the same time the temperature difference between the pressure side and the suetion side of the rotor is decreased. Undcr the cooling effect of low impcllcr wall temperature, the fluid temperature in whccl back clearance under conjugate hear transfer condition has a reduction, leading to a risc in density. The leakage of the seal increases approximately by 0. 92% and the windagc loss of the wheel back goes up about 12. 29% when the outlet pressure of the wheel back seal is 2 MPa. Compared with the adiabatic condition, the temperature of the working medium in the region of the whccl back seal decreases by 20 °C at the inlct and rises to 45 °C at the seal outlet.