Experimental Measurements and Numerical Investigations on the Aerodynamic Performance and Internal Flow Fields of Tangential Admission Volutes for Steam Turbines

Steam turbines are applied in production plants characterized by very large injections of steam. For this reason, the design and optimization of the admission are fundamentals to obtain an adequate level of turbine efficiency and ensure uniform flow at the inlet of the low pressure stages downstream the injection. In conjunction with a flexible operation and partial load conditions, it is important to estimate the losses appearing at those admissions sufficiently. The aerodynamic performance and flow field of the individual tangential admission volute and tangential admission volute coupled with the downstream vanes were experimentally measured and numerically simulated in this paper. The total pressure loss, outlet flow angle and mass flow rate of the individual tangential admission volute at three different outlet Mach numbers and tangential admission volute coupled with the downstream vanes at four different inlet total pressures were measured. The flow field of the experimental tangential admission volute for the steam turbine was numerically investigated using threedimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulence model. The numerical aerodynamic parameters of the tangential admission volute were in good agreement with the experimental data. The accuracy of the presented numerical method was validated. The flow field and aerodynamic parameters of tangential admission volute coupled with the downstream vanes were discussed under different inlet total pressure flow conditions. Then, three volute cases with different transverse distance were designed to investigate the influence of different outlet airflow angles on the aerodynamic performance of the downstream vanes. Results show that the outlet airflow angle of the individual tangential admission volute and tangential admission volute coupled with the downstream vanes usually keep constants when the inlet total pressure is increases. The averaged outlet airflow angle of the individual tangential admission volute and tangential admission volute coupled with the downstream vanes equal 152.0° and 166.6°, respectively. Comparing with the individual tangential admission volute, the outlet airflow angle of the tangential admission volute coupled with the downstream vanes is more uniform. The total pressure loss and mass flow rate of the individual tangential admission volute and tangential admission volute coupled with the downstream vanes increase with the inlet total pressure. With the increase of the inlet total pressure, the total pressure loss coefficient of the individual tangential admission volute increases from 0.73% to 1.64%. In the same case, the total pressure loss of the tangential admission volute coupled with the downstream stator vane increases from 0.82% to 2.66%. The average airflow angle of the volute increases with the increase of the transverse distance. With the increase of the transverse distance, the total pressure loss coefficient of the volute increases and the total pressure loss coefficient of the vanes decreases. At the same time, the total pressure loss coefficient of the whole model decreases at first and then increases. The present work provides the reference for the design and performance analysis of the tangential admission volute for the steam turbines.