Interaction mechanisms of shock waves with the boundary layer and wakes in a highly-loaded NGV using hybrid RANS/LES

Accurate predictions of Shock Waves and Boundary Layer Interaction(SWBLI)and strong Shock Waves and Wake Vortices Interaction(SWWVI)in a highly-loaded turbine propose challenges to the currently widely used Reynolds-Averaged Navier-Stokes(RANS)model.In this work,the SWBLI and the SWWVI in a highly-loaded Nozzle Guide Vane(NGV)are studied using a hybrid RANS/LES strategy.The Turbulence Kinetic Energy(TKE)budget and the Proper Orthogonal Decomposition(POD)method are used to analyze flow mechanisms.Results show that this hybrid RANS/LES method can obtain detailed flow structures for flow mechanisms analysis.Strong shock waves induce boundary layer separation,while the presence of a separation bubble can in turn lead to a Mach reflection phenomenon.The shock waves cause trailing-edge vortices to break clearly,and the wakes,in turn,can change the shocks intensity and direction.Furthermore,the Entropy Generation Rate(EGR)is used to analyze the irreversible loss.It turns out that the SWWVI can reduce the flow field loss.There are several weak shock waves in the NGV flow field,which can increase the irreversible loss.This work offers flow mechanisms analysis and presents the EGR distribution in SWBLI and SWWVI areas in a transonic turbine blade.

Effect of inlet rotating swirl on endwall film cooling for two representative hole arrangements

The swirl generator is widely used in lean-burn combustor to guarantee flame stability and reduce NOxemissions. Thus, the non-uniformities induced by the swirler would affect and damage film-cooling effectiveness on the turbine components, even blow-off coolant coverage, to some certain extent. The arrangement of film-cooling holes was normally designed to be perpendicular to the axial direction and in standard straight row. In this work we experimentally studied the effects of inlet swirl and mass flow ratio on traditional film cooling holes arrangement and a new arrangement pattern whose holes are located along the isobars. Results indicated that the swirl perturbation would damage film coverage. The film-cooling effect of endwall on which the holes are along the isobars, is invariably more promising than that of endwall on which hole arrangement is perpendicular to axial with the same mass flow of coolant, whether the inlet conditions is uniform or not.

Adjoint boundary sensitivity method to assess the effect of nonuniform boundary conditions

The performance of turbomachinery is largely affected by the nonuniform boundary conditions caused by the coupling between neighboring parts,such as the inlet distortion and hot streak.Existing works study this problem by comparing the flow fields with uniform and nonuniform boundary conditions,which is cost extensive.In this work a new and efficient method is developed by computing the sensitivities of arbitrary performance metric relative to the boundary conditions and this method quantitatively describes how the disturbance on the boundary surface affects the performance.The adjoint method popular in the design optimization is extended to current field for the efficient computation of the sensitivity.The extra cost is independent of the number of parameters describing the nonuniform distribution.Accuracy of the adjoint boundary sensitivity is validated against analytical results for a converging–diverging nozzle case.Its applications in a representative case are detailed and discussed in this paper.Current method provides a new tool,also direct guides to minimize the negative effect and improve the performance utilizing the adjoint boundary sensitivity.