Abstract
This work presents a numerical investigation of the combined effects of thermal barrier coating (TBC) with mainstream turbulence intensity (Tu) on a modified vane of the real film-cooled nozzle guide vane (NGV) reported by Timko (NASA CR-168289). Using a 3D conjugate heat transfer (CHT) analysis, the NGVs with and without TBC are simulated at three Tus (Tu = 3.3%, 10% and 20%). The overall cooling effectiveness, TBC effectiveness and heat transfer coefficient are analyzed and discussed. The results indicate the following three interesting phenomena: (1) TBC on the pressure side (PS) is more effective than that on the suction side (SS) due to a fewer number of film holes on the SS; (2) for all three Tus, the variation trends of the overall cooling effectiveness are similar, and TBC plays the positive and negative roles in heat flux at the same time, and significantly increases the overall cooling effectiveness in regions cooled ineffectively by cooling air; (3) when Tu increases, the TBC effect is more significant, for example, at the highest Tu (Tu = 20%) the overall cooling effectiveness can increase as much as 24% in the film cooling ineffective regions, but near the trailing edge (TE) and the exits and downstream of film holes on the SS, this phenomenon is slight.
Highlights
It is well-known that internal convection and impingement cooling, film cooling, and thermal barrier coatings (TBCs) are major techniques, which are widely used to protect gas-turbine airfoils from high turbine inlet temperatures (TITs) and achieve the maximum thermal efficiency in state-of the-art gas turbine engines
The convergence of the attentively results aretothat the the residual magnitudes energy and criteria of theequations results are thatreduce the residual magnitudes of energy and continuity equations must reduce continuity must to the levels of 10−6 and the converged are of substantiated by−3proving the balance of mass rates at results all inletsare and outlets, and by to results the levels
TBC are at the exits of the film that at the same turbulence intensity (Tu), is higher than φ, because is always lower than holes, and theof highest φTBC are found at the same position, i.e., x/C = 0.38 on the suction side (SS)
Summary
It is well-known that internal convection and impingement cooling, film cooling, and thermal barrier coatings (TBCs) are major techniques, which are widely used to protect gas-turbine airfoils from high turbine inlet temperatures (TITs) and achieve the maximum thermal efficiency in state-of the-art gas turbine engines. The effects of Tu on the film cooling performance and heat transfer coefficient of turbine airfoils, cylindrical leading edge and flat plate models have been experimentally and numerically investigated by previous researches [3,4,5,6,7,8]. To prolong and give good service to the turbine airfoils, TBC has been widely utilized in gas turbine designs as a thermal insulator between hot mainstream and metal surfaces. The insulating thermal capabilities of TBC are affected by many factors, such as porosity, thickness, thermal conductivity, and phase stability of the TBC material as well as the TIT and Tu of hot gas as reported by researches [9,10,11,12,13,14]
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