Numerical Investigation of Unsteady Flow Interactions in a Transonic Single Stage High Pressure Turbine

Understanding of the aerodynamic unsteady flow interactions is essential for improved performance of the modern turbomachines. The performance of a highly loaded transonic turbine is strongly influenced by the unsteady impact of stator trailing edge shock wave on the rotor. In this paper Three-Dimensional unsteady Navier-Stokes calculations of a single high pressure transonic turbine stage are presented. The numerical results predict the flow physics and the unsteady loss generation mechanisms fairly well in the transonic turbine stage. The flow domain is completely described by the velocity flow field and turbulent kinetic energy distribution at various planes behind the stator and rotor. Furthermore, the static pressure distribution at midspan helps to explain the stator-rotor interaction mechanism. The stator trailing edge shock wave impinges on the suction side of the passing rotor blades and reflected back intermittently thus setting up a periodic wake shedding phenomena. The reflected shocks interact with the boundary layer on the suction side of the stator near trailing edge and also on the rotor blade surface while transported through the rotor passage. The stator wakes are chopped by the passing rotor blades and convected through the rotor passage and thus influencing the rotor trailing edge flow. The unsteady pressure fluctuations showed that rotor suction side bears more fluctuations due to the accumulation of stator wakes on it. The understanding of unsteady flow physics and the loss generation mechanisms in turbomachinery will aid to develop methods to design highly efficient machines.