Aerodynamic/heat transfer analysis of discrete site film-cooled turbine airfoils

Abstract

goal is the use of film-cooling, wherein a layer of relatively The overall objective of this study was to examine cool gas is iqjected near the metal surfaces to provide a the aerodynamics and heat transfer characteristics of dis-buffer layer between the hot gas and the protected sursite film-cooled turbine &rf0&. The ob-faces. As operational temperature lev& rise in modern jective was to attempt to predict the three-dimensional gas turbine engines, accurately controlling turbine coolflow about the C3X turbine -e m a d e with a lading ing flows presents one of the more difficult engineering edge showerhead film cooling arrangement. The moti-challenges in the overall turbomaehinery d e s b process. vation behind this work was to validate and assess the Turbine airfoil blade row flows are characterized by accuracy of present 3-D Navier-Stokes predictions for re-large temperature gradients, Ma& numbers ranging from ticf film-cooled airfoil heat transfer predictions through low subsonic (< 0.15) to the transonic range (> LO), and comparisons with experimental data. high levels of freestream turbulence with strong, small Calculations were performed using a Cartesian COOP scale interactions between surface boundary layer convecdinate system and taking advantage of the spanwise p e tive flows, diffusive transport, and turbulent shear transriodicity of the C3X geometry. The film cooling flow was port. Aerodynamic and thermal design techniques curmodeled as injection at discrete holes and was introduced rently available to turbine airfoil designers have deficieninto the blade passage through the use of separate mesh cies which do not permit a priori designs which meet systems and transpiration/iection boundary conditions. desired design goals without expensive experimental deThe grid generation for the C3X m a d e involved mod-velopment iterations. As such, the airfoil/eoolant flow eling the film cooling holes as discrete objects in a 3-D injection design (hole size, placement, shaping, etc) is ofmesh. Calculations were performed for the C3X at multi-ten based on experience and/or empirical databases. Inple operating points, both with and without coolhg holes c r d utilieationof computational fluid dynamics (CFD) activated. Predicted results were compared with experi-techniques in the design process for turbmomachinery airmental data.foils and flowpaths has naturally led to the use of these tools for predicting airfoil surface heat transfer and film + . , cooling effectiveness. Unfortunately, our lack of comprchensive turbulence models capable of accurately predict ing heat transfer in high Reynolds number turbulent flows The trend in thermodynamic design Of gas turbine en-has prevented widespread acceptance of CFD techdques in the heat design arena. The of CFD for details ofthe gas path/coolant flow interaction can be very useful for determining trends a better of

Film Cooling Modelling for Gas Turbine Nozzles and Blades: Validation and Application

“…Mangani et al [96] analysed the same geometry and experimental test point tested by Laskowski et al [94] for validating a procedure aimed to transform OpenFOAM Hall et al [97] conducted 2D simulations of the internal/film cooled 1988 C3X vane leading edge film cooling data of Hylton et al [89]. The simulations included the film cooling holes and plena and made use of span-wise periodic boundary conditions to minimize the problem size.…”

Improvement of a Turbulence Model for Conjugate Heat Transfer Simulation

“…Hylton et al [28,29] of the NASA Lewis Research Center conducted a series of heat transfer tests to provide a database for testing the prediction capabilities of analytical models [30,31]. Their investigations covered a wide range of operating conditions and geometries under simulated engine conditions.…”

Gas Turbine Engines: Turbines

“…In a pure streamwise injection case, a symmetric vortex system is established. In a numerical investigation of a showerhead cooling configuration by Hall, Topp and Delaney (1994), it was observed that effects caused by these vortex systems could lead to a cooling flow effectiveness degradation and lift-off of the cooling jet. Besides the negative impact on the cooling performance, the mixing out of the vortices with the main flow generates further aerodynamic losses.…”