Design and performance analysis of an ORC transonic centrifugal turbine

摘要

The centrifugal turbine is a new type of turbine that has lots of benefits including high efficiency, simple structure, small volume, which can be used as small-to-medium turbine in industry and waste heat utilization. The transonic ORC turbine has quite larger size compares to the steam and gas turbine for the low acoustic velocity of organic fluids. As requirements for smaller and lighter weight components push turbines to more compact, closely coupled designs, a transonic nozzle is adopted to enhance the single-stage enthalpy drop of centrifugal turbine and reduce the stage number and size of turbine. By consulting aerodynamic design method, parameters of axial turbine and using R141b as working fluid, a transonic nozzle and the corresponding rotor cascade of centrifugal turbine are designed, in addition, the three-dimensional numerical simulation and performance analysis are conducted in this paper. The aerodynamic performance of the transonic centrifugal turbine stage was subsequently assessed by three-dimensional numerical simulations. Likewise, the flow characteristics analysis was carried out under design and off-design conditions. Results of numerical simulation indicate that the aerodynamic performance of the transonic centrifugal turbine stage is in conformity to the design requirement with reasonable flow field distribution, smooth streamline. The enthalpy drop of designed transonic nozzle is at least twice more than that a subsonic nozzle can achieve, which can greatly enhance turbines' load capacity and reduce the size of turbine. Meanwhile the off-design performance analysis shows that the transonic centrifugal turbine has wide stable operation range and strong load adaptability.