Experimental Investigations on Effects of Unsteady Wakes on the Secondary Flows in the Linear T106 Turbine Cascade

Abstract

The present work extends previous investigations on the secondary flows around a steady base flow to detailed time-averaged and time-resolved flow field measurements up- and downstream of a low pressure turbine (LPT) cascade. Unsteady inflow was generated by a moving bar system. The inlet conditions were determined using single hot wire anemometry and a pitot probe. Further detailed measurements of the three-dimensional flow field were carried out downstream of the cascade with triple hot wire anemometry, a conventional five hole pressure probe, and a dynamic pressure probe equipped with a single Kulite sensor. All measurements have been performed with and without moving bars. Cases with different Strouhal numbers and flow coefficients have been considered by varying the pitch of the moving bars between 40 mm and 80 mm and circumferential speed between 10m/s and 20m/s in order to investigate the influence of unsteady inflow in particular on the secondary flow field near the endwalls. It turned out that the effects of the incoming wakes are evident in the time-accurate data in terms of their interaction with secondary flow vortices. On a time-averaged basis, however, the influence of the incoming wakes on the secondary flow field turned out to be small for the small inlet boundary layer.