Aerodynamic Design Of A Highly-Loaded Transonic Radial Steam Turbine

The boiler loading is usually limited by the area of the solar collectors in solar thermal power plants. Thus, the turbine selection is a problem due to the fact that for high efficiency the enthalpy drop should be as high as possible and the mass flow rate of the steam through the turbine becomes very small. In addition to its small size and compact structure, radial inflow turbines can also be of high efficiency, better than that of axial turbines, in the application cases with small flow rate and high enthalpy drop. With the progress of materials and manufacturing technology, radial inflow steam turbine is drawing increasing attention.A high-loaded radial inflow turbine with partial admission used in a MW class tower solar power plant is designed in this thesis. The turbine works at a high efficiency of86.97%when the mass flow and pressure ratio are2.33kg/s and3.36respectively. The aerodynamic design is combined by one-dimension aerodynamic method and three-dimension computational fluid dynamics (CFD) simulation. The effects of nozzle profile, distribution of blade’s β angle, number of blades on efficiency is researched by numerical simulations. The results show that the wedge-shape nozzle can take advantage of its chamfered part to make the steam to achieve the transonic speed, it also adapts very well to flow direction. The distribution of blade’s β angle has a great impact on the flow characteristic because it can effectively control the flow separation. Although increasing the number of blades can effectively reduce flow separation in blade passage, it increases friction loss between steam and blade, makes the flow path narrowing and thus reduces the mass flow rate. The numerical simulation results indicate that the radial inflow turbine meets the performance requirements. Unsteady computation is performed on partial admission model and the results are compared with full admission model. Finally, the stress analysis of the impeller is done using finite element (FE) code ANSYS and the results show that the titanium alloy TC4can meet the strength requirement.