Aerothermal Simulations Comparisons of a Shaped-Hole Film Cooling Flow

Abstract

Film Cooling is a crucial technology for engine manufacturer to develop high-efficiency gas turbine engines by raising turbine entry temperature. A lot of cooling holes geometries have been studied in the past few years in tests, as well as numerical simulations. Shaped holes are nowadays a standard geometry for protecting the blades, given the performance improvement compared to cylindrical holes. Numerical correlation with physical tests is challenging due to the high sensitivity to thermal mixing and adequate boundary condition predictions. This paper is devoted to numerical simulation comparisons of the 777 shaped holes configuration of Pennsylvania State University, for an incompressible flow with a density ratio of 1.5, a blowing ratio of 1.5 and a free stream turbulence intensity of 0.5%. Two different simulations have been chosen: a state-of-the-art RANS simulation with k-e Realizable model computed with ANSYS Fluent and a high fidelity solver Lattice-Boltzmann Method computed with Simulia PowerFLOW. In order to improve the accuracy of numerical simulations against test results, this article deals with an aerothermal model of the complete test bench. This additional modeling allows to strongly improve thermal prediction and to understand initial discrepancies related to test bench environment. Results show that k-ε Realizable simulation provides a good prediction of average effectiveness, but local differences appear due to inherent RANS modeling limitations. On the other hand, LBM simulation provides excellent results for both aerodynamic and thermal quantities: tests results are very well reproduced.

Towards an Improved Description of Film-Cooling Heat Transfer Through Anisotropic RANS Modeling: A Combined LES/RANS Contribution

“…To better assess the relative performances of the different models, Figure 12 details the centerline effectiveness distributions for the different models. As already mentioned before, Simon et al [33] have shown that conductive effects not taken into account in the RANS and LES simulations are responsible for the most part of the discrepancy between LES and experiment. Therefore, RANS results are to be compared more to the LES evaluation than to experimental results, both of them assuming adiabatic boundary conditions.…”

“…For 𝑍/𝐷 = ±3 the effectiveness is zero for the LES, whereas it does not vanish in the experimental data (Figure 6). Simon et al [33] have shown that this discrepancy can be explained by the conductive heat transfer within the plate, not reproduced by the adiabatic wall boundary condition of the simulation. Note also that to investigate dynamic Reynolds-stress models, taking into account heat conduction within the plate would not be relevant.…”

Hybrid RANS-LES of Shaped Hole Film Cooling on an Adiabatic Flat Plate at Low Reynolds Number

“…Although limited research has been able to predict adiabatic effectiveness along the hole centerline, conventional Reynolds-averaged Navier-Stokes (RANS) turbulence models have been shown to be inadequate in capturing the lateral spreading of the jet in crossflow [4] [5] [6]. Recent work has also explored the use of a Lattice-Boltzmann solver to capture the turbulent flow physics for both adiabatic and conjugate heat transfer cases [7] [8]. With all things considered, some form of a scale-resolving simulation with a subgrid-scale model is desired in order to accurately predict the effectiveness of film cooling schemes.…”