Experimental and Numerical Study of Partial Admission Effect on Flow Distribution in Supersonic Turbine Axial-Gap

In high-pressure axial turbines، when the fluid mass flow is low، the supersonic blades are being used to obtain a high specific work output. To prevent losses due to low blade aspect ratio، the turbine is used in partial admission conditions. The turbine stator is a group of convergence-divergence nozzles that provides the supersonic flow. The design of these nozzles is important، because there is a direct relationship between the degree of partial admission and nozzle design parameters. The turbine efficiency is highly dependent on partial admission degree. To assess، in first step، an evaluation was carried out using an appropriate turbine efficiency correlation; then، a three-dimensional numerical analysis was implemented، and finally a series of experimental tests were carried out to validate the above assessments. The experimental results showed a good agreement with 1D and 3D numerical predicted results of turbine performance. The results showed that even small changes in the nozzle geometric parameters and partial admission degree، have a significant impact on the turbine performance and the flow distribution in the axial gap.