Optimal design and tip leakage flow characteristics analysis of radial inflow turbine used in organic Rankine and vapor compression refrigeration system

As the core component of the ORC, the optimal design of the radial inflow turbine (RIT) is crucial for enhancing system performance. An improved 1-D mean-line optimization design model based on real gas physical properties of the RIT is proposed. Compared to conventional 1-D mean-line models, the proposed model integrates numerous critical aerodynamic and structural constraint conditions, reducing the uncertainty dimension of critical design parameters, and narrowing the range of values for the reaction degree and the velocity ratio. The three-dimensional flow characteristics and aerodynamic performance of the RIT are investigated through a three-dimensional computational fluid dynamics (CFD) analysis. The flow characteristics and loss mechanisms of tip leakage flow under various blade tip clearances are further investigated. The results indicate that the leakage flow through the tip clearance has a tremendous impact on the internal flow characteristics of the RIT and is a key factor leading to a substantial increase in flow losses. With an increase in relative blade tip clearance from 0 to 15.63%, the isentropic efficiency of the RIT gradually decreases from 88.57% to 80.32%. It is equivalent to an approximate 0.53% reduction in isentropic efficiency for every 1% increase in the relative tip clearance.