Orthogonal Decompostition Analysis and Optimization of Turbine Vane Endwall Horseshoe Vortex Dynamics and Heat Transfer
|Title||Orthogonal Decompostition Analysis and Optimization of Turbine Vane Endwall Horseshoe Vortex Dynamics and Heat Transfer|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||Schwanen, M, Duggleby, A, Fischer, PF|
horseshoe vortex, on a gas turbine endwall is investigated by using direct numerical simulation. This vortex is disruptive to the protective cooling layer because it drives hot combustion gases to the endwall surface. It exhibits significant dynamical motions that further increase the surface heat transfer. The dynamics of the horseshoe vortex must be characterized in a 3D time-resolved fashion in order to better understand their impact on heat transfer augmentation. In this paper, a first-stage high-pressure stator passage is examined by using spectral-element direct numerical simulation at a Reynolds number Re=U C/v = 10,000. Although this is lower than engine conditions, the vortex exhibits similar strong, aperiodic motions. A novel inflow generation technique is introduced to generate appropriate initial conditions, which are challenging especially for gas turbine engine flows that are characterized by high free-stream turbulence and large, integral-length scales. The inflow consists of a periodic solution of Taylor vortices that are convected over a square grid. The size of the vortices and grid spacing is used to control the integral-length scale, and the intensity of the vortices and upstream distance between the grid and vane is used to control the turbulence intensity. The vortex system is analyzed by using a time correlation-based orthogonal decomposition. The resulting basis functions are ranked with respect to their contribution to the turbulent heat flux. The endwall is then shaped to enhance the modes that reduce heat transfer, resulting in a lower overall heat transfer in the stagnation region.