Aerodynamics Design Of A Transonic Radial Inflow Stream Turbine

Compared with axial turbine, the characteristic of the radial inflow turbine is that Coriolis force generating additional lossless work. Thus, the output power of a single stage of radial inflow turbine can be greater than that of a stage of axial turbine. With the tight structure and the simple production craft, radial inflow turbine could also be of higher efficiency than that of an axial stage, especially in the case of small flow rate. Aerodynamics design of a 300kW transonic radial inflow steam turbine is discussed in this thesis, which combined one-dimensional aerodynamic method of the radial inflow turbine with the state-of-art three-dimensional CFD numerical simulation. The enthalpy drop of the designed stage is 248.5kJ, and the pressure ratio is 4.17.In order to achieve higher efficiency, a small reaction degree is selected, so supersonic flow fields appeared in the stator cascade, the designed absolute Mach number at the stator outlet is 1.35.In this thesis, the stator is continuously reducing blade. Research indicates that: Although the stator is continuously reducing blade, high efficiency can be reached under supersonic condition. However, the expansion ability of the continuously reducing blade is limited. When the Mach number at the stator outlet achieves the certain value, the expansion ability of the continuously reducing blade is run out. If we continuously increase the enthalpy drop, flow loss will be more evident. Under this condition, supersonic guide vanes should be adopted.The impeller blade number and the Arc-curvature of the impeller blade have important impact on flow efficiency and characteristics. They all have an optimal value respectively. Furthermore, the radial inflow impeller with long-short blades is discussed in this thesis. Emphasis is focused on the effect of the short blade length and position on the flow and characteristics of the stage. The results from the study show that: To the high load and transonic turbine, the radial inflow impeller with long-short blades can effectively improve the flow field characteristics and output power; the efficiency is highest when the length ratio of the short blade to the long blade is between 0.6 and 0.65; the efficiency is highest when the position of short blade is close to the pressure-side of the long blade.