Large eddy simulation study on trailing edge cutback cooling with a whisker lip

Abstract

In this study, the whisker structure of a harbor seal is applied to the lip of a turbine blade's pressure-side cutback cooling unit. Three cases are studied in this paper, including a prototype, an elliptic lip and a whisker lip. Large Eddy Simulation is used to study the flow in the cutback cooling unit. Blowing ratios (BR) ranging from 0.6 to 1.1 are simulated. The results show that the elliptic lip and whisker lip can increase the film cooling effectiveness by 0.04 (BR = 0.8) to 0.08 (BR = 0.6) under different blowing ratios. The whisker lip can achieve the best cooling performance at the medium blowing ratio (BR = 0.7 - 0.9). The analysis shows that the elliptic lip and the whisker lip structure suppress the shedding vortex, reducing mixing between hot gas and coolant. Dynamic Mode Decomposition (DMD) reveals that the energy of the Kelvin-Helmholtz (K-H) instability of the elliptic lip and the whisker lip is reduced to 2.8% and 5.1%, respectively. The structure of the K-H mode of the elliptic lip and the whisker lip dissipates at the rear of the cutback surface. Therefore, the coverage effect of the coolant on the cutback surface is improved. The whisker lip makes the boundary layer converge to the valley before separation, reducing the mixing in the peak area, which improves the overall film cooling effectiveness.