Preliminary design and CFD analysis of a radial inflow turbine and the turbine seal for an organic Rankine cycle using zeotropic mixture

Zeotropic mixtures exhibit great potential for further investigation of organic Rankine cycle (ORC) in the field of low temperature heat utilization because of the characteristics of varying temperature evaporation in two-phase region. However, few studies are contributed to the design of zeotropic mixture turbine and turbine seal. In this paper, the system optimization of ORC by means of genetic algorithm is conducted for different mixtures to obtain the optimal mixture working fluid and initial design parameters of turbine. The thermal design of the mixture ORC radial inflow turbine is carried out, and the CFD simulation is performed to investigate the three-dimensional flow characteristic of the designed turbine. Meanwhile, the helical groove seal of the turbine shaft is designed and analyzed through CFD method. Results show that the mixture ORC radial inflow turbine is well designed with an isentropic efficiency of 83.71%, and CFD results basically match with the thermal design results. What's more, the CFD simulation result for the differential pressure of the helical groove seal has an only −5.83% deviation compared with the designed one, and the helical groove seal is well designed with desirable sealing performance.