THERMAL BARRIER COATING AND TURBULENCE INTENSITY EFFECTS ON LEADING EDGE COOLING USING CONJUGATE HEAT TRANSFER ANALYSIS

Transcription

1 THERMAL BARRIER COATING AND TURBULENCE INTENSITY EFFECTS ON LEADING EDGE COOLING USING CONJUGATE HEAT TRANSFER ANALYSIS Prasert Prapamonthon, Huazhao Xu, Zhaoqing Ke, Wenshuo Yang and Jianhua Wang School of Engineering Science, University of Science and Technology of China, Hefei, China Received September 2016, Accepted January 2017 No. 16-CSME-112, E.I.C. Accession 3998 ABSTRACT This is a numerical study of thermal barrier coating (TBC) and turbulence on leading edge (LE) cooling of a guide vane. Numerical results were carried out using 3D CFD with conjugate heat transfer analysis. Important phenomena were revealed. (1) TBC is effective in the LE region especially when free stream turbulence (Tu) increases. (2) At each Tu, TBC near the hub of the vane provides the most effective protection and at the highest Tu, TBC improves overall cooling effectiveness there by about 25%. (3) Near the exits of film hole, TBC may have negative effect, because of heat transfer impedance from the solid structure into the mixing fluid between mainstream and cooling air emitted from film holes. Keywords: turbulence intensity; cooling effectiveness; thermal barrier coating. REVÊTEMENT ISOLANT THERMIQUE ET LES EFFETS DE L INTENSITÉ DE LA TURBULENCE SUR L ANALYSE DU TRANSFERT DE CHALEUR COMBINÉ AU REFROIDISSEMENT DU BORD D ATTAQUE RÉSUMÉ Nous présentons une analyse numérique du revêtement isolant thermique (TCB), et la turbulence sur le bord d attaque de l aube directrice (LE). Les analyses sont faites en utilisant CFD en 3D combiné avec le transfert de chaleur. Des phénomènes importants ont été constatés. (1) TBC est efficace dans la région du bord d attaque spécialement quand la turbulence du fluide libre augmente. (2) À chaque turbulence, TBC près du moyeu de l aube procure la protection la plus efficace, et au plus fort de la turbulence TBC améliore l efficacité totale du refroidissement de près de 25%. (3) Près de la sortie du trou du film, TBC peut avoir un effet négatif à cause de l impédance du transfert de chaleur de la structure solide dans le mélange entre le fluide et le courant dominant et l air refroidi disséminé par les trous. Mots-clés : intensité de la turbulence; efficacité du refroidissement; revêtement isolant thermique. Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

2 NOMENCLATURE c p, f specific heat capacity of fluid (J/kg K) c p,m specific heat capacity of solid (J/kg K) c p,t BC specific heat capacity of TBC (J/kg K) h heat transfer coefficient without TBC, at vane surface and mainstream (W/m 2 K) h T BC heat transfer coefficient with TBC, at TBC surface and mainstream (W/m 2 K) h difference between heat transfer coefficient without and with TBC (W/m 2 K) k f thermal conductivity of fluid (W/mK) k m thermal conductivity of solid (W/mK) k T BC thermal conductivity of TBC (W/m K) Ma Mach number P pressure (Pa) total pressure (Pa) P T P S static pressure (Pa) PR pressure ratio [PR = P T /P S ] q flux heat flux between solid and fluid interfaces (W/m 2 ) R percentage of metal temperature reduction (%) T metal surface temperature without TBC (K) T c,inlet inlet temperature of cooling air (K) T ref temperature at reference (709 K) T T BC metal surface temperature with TBC (K) T W local wall temperature (K) T inlet temperature of mainstream (K) T TBC surface temperature (K) Tu ) free-stream turbulence intensity (%) temperature gradient at interfaces (K/m) ( T n T w=0 difference between metal surface temperature without and with TBC (K) Greek symbols ρ f density of fluid (kg/m 3 ) ρ m density of solid (kg/m 3 ) ρ T BC density of TBC (kg/m 3 ) φ overall cooling effectiveness on metal surface without TBC φ T BC overall cooling effectiveness on metal surface with TBC φ difference between overall cooling effectiveness with and without TBC 1. INTRODUCTION An increment of thermal efficiency and power output of gas turbines can be achieved through increasing turbine inlet temperature (TIT). However, TIT is limited by the allowable temperatures of current materials. To maintain a reasonable operating life of gas-turbine airfoils, film cooling and thermal barrier coating (TBC) have been widely used in modern gas turbine engines. With advances in numerical simulations, the technique of computational fluid dynamics (CFD) with conjugate heat transfer (CHT) analysis has been widely applied in gas-turbine fields. Ni et al. [1, 2] and Mazur et al. [3] deemed that CHT analysis have the following three advantages, firstly, this analysis can provide not only a better understanding on the mixing process of cooling air with mainstream, but also the temperature variation within solid structures; secondly, the results obtained by this analysis are able to be easily incorporated into routine analysis of durability; lastly, CHT analysis can give a more accurate approximation of convective boundary conditions, in comparison with given isothermal 250 Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

3 boundary conditions. Therefore, CHT analysis was used to predict cooling performances of turbine vanes in their works. Zhang et al. [4] used CHT analysis with thee turbulence models i.e. realizable k-ε, SST k-ω, and V2F models to study cooling performances of the guide vane reported by Timko [5] by comparing cooling effectiveness obtained by CHT analysis with adiabatic assumption. Their comparisons indicated that heat conduction predicted by CHT analysis uniformly promoted cooling performance. The usable experimental data of C3X and Mark II, two cooled vanes of NASA reported by Hylton et al. [6], have been widely used to validate numerical results obtained by CHT analysis. Yoshiara et al. [7] simulated the aero-thermal characteristics of C3X and Mark II using CHT analysis with Spalart-Allmaras, SST k-ω, and SST k-ω coupled with γ-re θ transition turbulence models. They found that the numerical results predicted by the three models gave quite good agreements with the experimental data. Zhang et al. [8] used CHT analysis with SST k-ω, SST & AGS, and SST & γ-re θ turbulence models to investigate the cooling characteristics of Mark II. They concluded that SST & γ-re θ model improved the prediction accuracies of temperature and heat transfer coefficients in the laminar zone near leading edge (LE). However, few studies have considered thermal resistance effect of TBC on the gas-turbine airfoils using CHT analysis thus far. In the previous studies, Bohn and Becker [9] investigated the effect of TBC on the aero-thermal characteristics of Mark II using CHT analysis with a turbulence model provided by Baldwin Lomax [10]. They found that the relative temperature on the external surface of the coated vane was higher than that of the uncoated vane about to 4.4%, and the maximum heat transfer coefficient occurring in the shock area on the suction side (SS) was reduced by TBC about 15%, but TBC could not reduce the heat flux into the whole vane. With the same simulation approach, Bohn and Tümmers [11] investigated the effects of TBC and cooling air mass flow on thermal stresses of Mark II coated with two layers of TBC, the top coating was ZrO 2 with a thickness of mm, and the bond coating was MCrAlY with a thickness of 0.06 mm. They declared that although TBC surface temperature rose, below TBC, the metal temperature was reduced and equalized simultaneously. Additionally, the influence of reduction in cooling air mass flow on the thermal stresses in the solid structure was significantly lower than the influence of TBC. Using CHT analysis with SST k-ω turbulence model, Alizadesh et al. [12] studied the effects of the thickness and thermal conductivity of TBC on a turbine blade. They concluded that adding a 0.2 mm of TBC thickness reduced the blade averaged and maximum temperatures of about 19 and 34 K, respectively. Moreover, the rise in thermal conductivity of TBC from 1 to 3 W/(mK) increased the blade averaged temperature about 10 K. As referred by Undapalli and Leylek [13], film cooling performances were influenced by many factors, such as configuration of film holes, adverse pressure gradient, boundary layer thickness and free stream turbulence. Among these factors, Boyle et al. [14] pointed out that turbulence intensity (Tu) and turbulence length scale could be physically significant. Mayhew et al. [15] predicted that Tu of real gas turbines was usually in a range of 10 20%. Ou and Han [16] experimentally investigated the effects of Tu on film effectiveness and heat transfer coefficient in the LE of a cylindrical leading edge model, at Tu = 0.75, 5.07, and 9.67%, and blowing ratios of 0.4, 0.8, and 1.2. They concluded that when Tu increased, heat transfer coefficient increased, and film effectiveness decreased, but at high blowing ratios, the effects of Tu were reduced. Besides, Ekkad et al. [17] studied film effectiveness and heat transfer coefficient of a cylindrical leading edge model using a transient liquid crystal technique. They found that at lower blowing ratios, a higher Tu might reduce film effectiveness, but this effect was not significant at higher blowing ratios. Ames [18, 19] experimentally investigated the influences of Tu (Tu = 1 12%) on cooling performances of C3X, and they found that the higher Tu evidently augmented the averaged heat transfer coefficient on the pressure side (PS), and reduced film effectiveness and quickened the dissipation of film effectiveness on SS. Thole et al. [20] investigated experimentally the heat transfer performances of a first stage nozzle guide vane at Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

4 Tu = 0.6 and 19.5%. Their results indicated that when Tu was at 19.5%, heat transfer coefficient achieved the largest value in stagnation region. Up to now, rarely has the use of numerical techniques with CHT analysis to investigate the combined effects of Tu and TBC on cooling performance of the gas-turbine airfoils been reported. The objective of this work is to study and provide a better understanding of the effects of Tu and TBC on surface temperature, heat transfer coefficient and overall cooling effectiveness in the LE region and its vicinity of a film-cooled turbine vane with a technical aspect of the numerical simulation using CHT analysis. Furthermore, this work can be practically applied by gas-turbine engineers to obtain better design of gas-turbine vanes and improvement of cooling performances in the LE region and its vicinity when the film-cooled vanes coated with TBC operate under real conditions with various Tus of hot gas from the combustion chamber. 2. THERMAL PARAMETERS Three important thermal parameters used in this work are as follows: (a) The heat transfer coefficient; it is defined by where h = T w = q flux T T w = ( ) k T f n w=0 (1) T T w { T, vane without TBC T T BC, vane with TBC a negative h means that q flux transfers from the vane surface to the mainstream, on the other hand when q flux transfers from the mainstream to the vane surface, h is positive. (b) Overall cooling effectiveness, this parameter is used to describe the normalized solid temperature under a wall with heat conduction. It is calculated by φ = T T w T T c,inlet (2) where { T, vane without TBC T w = T T BC, vane with TBC (c) The percentage of metal temperature reduction, this parameter is used to evaluate the ability of TBC to protect metal surfaces from the hot gas. This is defined by ( ) ( T R = 100% = 1 T ) TBC 100%. (3) T T Since T TBC is always lower than T, R is always positive. 3. VANE CONFIGURATION The film-cooled guide vane used in this work is adapted from Timko [5]. It is a slightly twisted vane with a span of 4 cm. There are 7 film-hole rows in the LE and its vicinity, as shown in Fig. 1a, two rows are placed on the LE (LE1 and LE2), two rows are located on the SS (SS1 and SS2), and three rows are positioned on 252 Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

5 Fig. 1. (a) Vane configuration; (b) its cross-section area at 52.5% midspan. Fig. 2. Temperature distributions along vane surface at midspan. the PS (PS1, PS2, and PS3). Each row has 12 film holes with an equal distance of 1 mm. All of the film holes are cylindrical with the same diameter of 0.48 mm, and the same angle of 45 as reported by Nasir et al. [21]. There are two cavities, aft and forward cavities in the vane to supply coolant. This numerical study focuses on the cooling performances in the LE and its vicinity limited within the region of 0 x/c0.4, 0 y/d 0.4, and 0 z/h 1, as shown in Fig COMPUTATIONAL PROCEDURES 4.1. Computational Strategy The commercial software, ANSYS ICEM V.15, is used to generate computational grids. To achieve a high quality, the entire calculation domain is decomposed into five blocks, i.e. mainstream, film hole, forward cavity, aft cavity, and solid vane. The grids in each block are hexahedral. O-grid is used to improve all grids near the surfaces to suffice for resolving fluid flow in boundary layer. To confirm the grid independence of numerical results, three strategies with grid elements of 4,834,244 (4.8M), 5,123,256 (5.1M), and 6,489,129 (6.4M) are tested. Figure 2 exhibits the metal surface temperature distributions along the vane s midspan. Most portions of the numerical results in 5.1M and 6.4M give acceptable agreements, and the highest difference is less than Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

6 Fig. 3. Computational grid. Table 1. Properties of TBC material. Property Value ρ TBC 5500 kg/m 3 c p,tbc 418 J/kgK 1.04 W/mK k TBC Table 2. Specific heat capacity and thermal conductivity of air and steel. Specific heat capacity (J/kg K) Thermal conductivity (W/m K) Air c p, f = T k f = T Steel c p,m = T k m = T 2%. Therefore, it is not necessary to further the elements, and it is reasonable to use the grid with 5.1M elements in the following calculations. Figure 3 shows some computational grids in mainstream, two cavities, film hole, and solid vane. The averaged and the minimum quality of the whole computational grid are about and 0.135, respectively Computational Setup The commercial software, FLUENT V.15, with SST k-ω turbulence model, the pressure-based segregated algorithm, and SIMPLE method are used in this work. The discretization scheme with second order accuracy is utilized in all fluid and solid regions. In order to increase the accuracy of the results, low-re corrections, compressibility effect, curvature correction, viscous heating, and production limiter are considered. Equations of mass, momentum and energy are solved within fluid domains, but in solid domain, only the energy equation based on Fourier s law is solved. Convergence criteria of the results are that the residual values of the scaled energy and continuity equations must be less than 10 6 and 10 3, respectively. To confirm the convergence, mass flow rate balance between all inlets and outlet, and residual histories of temperature at six monitor points on the vane surfaces are checked. The coupled wall option is applied at fluid-solid interfaces to ensure that the heat flux and temperature on both fluid and solid sides are equivalent. To combine the effect of TBC, TBC made of typical ZrO 2 with a thickness of mm is used, as referred by Halila et al. [22]. Due to the thin thickness of TBC, only 1D heat conduction equation is solved in TBC. It this study, a bond coat is not considered in all calculation, the bond coat is presumed to be a part of the vane surface with a relatively thin thickness. Consequently, it cannot have a major role in conductive heat transfer through the wall. The physical properties of TBC used in this study are listed in Table 1. Air with the ideal gas assumption is used as working media in the mainstream and coolant, the vane is made of steel with a density of 8055 kg/m 3, and the thermal properties of the air and steel within a temperature range from 339 to 1000 K are calculated by the equations given in Table Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

7 Table 3. Boundary conditions used in this work. Boundary Condition Mainstream inlet T = 709K, P T = kpa, Tu = 3.3, 10, and 20% Mainstream outlet Pressure-outlet, PR = 1.67 Forward cavity inlet T c,inlet = 339 K, P T = kpa Aft cavity inlet Mass flow rate, kg/s Fig. 4. Boundary conditions. Fig. 5. Mach number distributions along vane surface at midspan Boundary Conditions The experimental conditions reported by Timko [5] are used as the simulation conditions, as listed in Table 3. As shown in Fig. 4, periodic condition at two side surfaces, adiabatic and non-slip wall conditions at the top and bottom of the entire mainstream domain are used. Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

8 Fig. 6. Temperature distributions at three Tus Validation of Numerical Method To validate numerical method, the experimental data obtained by Timko [5] at PR = 1.67 are used. CHT simulation is carried out by SST k-ω turbulence model. Figure 5 presents a comparison between Mach number (Ma) distributions along the vane s midspan predicted by the numerical method against the Ma obtained by the experimental approach. It is clear, on the PS in the region 0.4 < x/c < 0, and on the SS in the region 0 < x/c < 0.05, the numerical results exhibit a very good agreement with the experimental data. On the SS, after x/c = 0.04, the 256 Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

9 Fig. 7. Contours of T at three Tus. difference between experimental and numerical results increases with the maximum averaged error about 10%. This validation seems reasonable and acceptable. Therefore, in the following simulations, CHT analysis with SST k-ω turbulence model at PR = 1.67 is used. 5. RESULTS AND DISCUSSIONS 5.1. Effects of TBC and Tu on Temperature Distributions Figure 6 presents temperature distributions over TBC surface (T ), on the metal surface without TBC(T ), and on the metal surface with TBC (T TBC ) at three Tus. From the three series of Fig. 6, one can find the following three important phenomena: (1) At the same Tu,T is always the highest, and T TBC is always lower than T, and T countor is quite different from T countor, but T countor is similar to the temperature distribution obtained by adiabatic assumption in our past work [23]. This phenomenon is reasonable because the very large thermal resistance of TBC blocks heat flux transferring into the solid structure. (2) At each Tu, the maximum temperatures of T,T and T TBC always happen in the tip region of the vane because this region is the hardest region to be cooled by cooling air. (3) When Tu increases, the regions with higher temperatures, especially near stagnation line, extends significantly. The reason for this pheomenon is that it is more difficult to cool these regions by cooling air when the level of Tu is elevated. For distinguishing the real TBC effect, Figs. 7a c are used, which show the temperature differences, T = T T TBC, at three Tus. From these figures, one can find two important phenomena: (1) T is always greater than zero. It means that TBC plays a positive role of thermal protection. Furthermore, the maximum T happens near the hub region of the vane, namely the maximum T is about 36, 38 and 42 K at Tu = 3.3, 10, and 20%, respectively. This is expected because the hub region is closest to the coolant inlet of the forward cavity, which has the lowest temperature. (2) With increasing in Tu, this positive role is more significant. Figure 8 exhibits a quantitative comparison of TBC effect in term of the percentage of temperature reduction, R, at 52.5% span. From this figure, one can find that at each Tu,R decreases in streamwise direction, and R gradually decreases after PS3, but drastically decreases after SS2. When Tu increases, R increases in general, and the increment of R in the region from PS3 to stagnation line is larger than that in the region from SS2 to stagnation line. This can be explained by the fact that the increase in T and T TBC in the region from PS3 to stagnation line is more serious than that in the region from SS2 to stagnation line, as shown in Fig. 9. Additionally, R can achieve the highest value about 6.8% at Tu = 20% and about 5.8% at Tu = 3.3% near stagnation line. Therefore, the TBC technique is effective in LE, and the thermally protective effect on the PS is better than that on SS, especially near stagnation line and at higher Tus. Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

10 Fig. 8. Distribution of R at 52.5% span. Fig. 9. Effects of Tu on T and T TBC at 52.5% span Effects of TBC and Tu on Heat Transfer Coefficient Figure 10 illustrates distributions of heat transfer coefficients on the metal surface without TBC(h) and over TBC surface (h TBC ) at three Tus. It is clear that at the same Tu,h and h TBC are similar in general, but most h TBC are lower than h. The relatively higher h and h TBC exist in LE, as marked as region 1. The highest h and h TBC appear near the tip and the hub of the vane, as indicated in regions 2 and 3, respectively. This is reasonable because these regions are hardly cooled by the cooling air ejected from film holes. When Tu increases, h enlarges much more rapidly than h TBC in the three regions. This can be explained by the fact that in these regions the boundary layer is very thin and the cooling air ejected from film holes is hardly to form an effective coverage film at higher Tus. Therefore, TBC can play an important role to reduce the effect of Tu through its very large thermal resistance. Figure 11 shows a comparison between h and h TBC distributions from LE2 to SS2, at Tu = 10%, as marked as region X in Figs. 10b and 10e. The difference between h and h TBC conspicuously appears near 258 Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

11 Fig. 10. Contours of (a c) h and (d f) htbc at three Tus. Fig. 11. Contours of region X in Figs. 10b and 10e at Tu = 10%. the exits of film hole LE1, SS1, and SS2, i.e. h and htbc are negative, but h is lower than htbc. This phenomenon may be explained by the fact that on the surface with TBC, the thermal load transferring from the solid vane into cooling air-mainstream mixing fluid in these regions are reduced by the lower thermal conductivity of TBC. This phenomenon can be more explained by Fig. 12, which presents the differences between h and htbc, h = h htbc, at three Tus. A positive value of h means that TBC blocks the heat flux from mainstream Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

12 Fig. 12. Effect of TBC on h at three Tus. Fig. 13. Contours of (a c) φ and (d f) φtbc at three Tus. entering the vane structure, and TBC plays a positive role; whereas a negative value means that TBC blocks the heat releasing from solid vane into the mixing fluid of cooling air and mainstream, at this time TBC plays an opposite role. From Fig. 12, one can observe that for all Tus, h is positive in most regions, but near the exits of film hole LE1, SS1, and SS2, is negative. Therefore, although TBC technique is effective in the LE region, TBC can block the heat releasing from solid structure into the mixing fluid close to the exits of film holes, this is a negative effect. This remarkable difference can be also observed at Tu = 3.3 and 20%. 260 Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

13 Fig. 14. Effects of TBC on φ at three Tus Effects of TBC and Tu on Overall Cooling Effectiveness Figure 13 shows contours of overall cooling effectiveness on the metal surface of the vane without TBC(φ) and with TBC(φ TBC ) at the three Tus. At the same Tu, it is clear that φ is always lower than φ TBC because T TBC is always lower than T. Generally, φ and φ TBC decrease with an increase in Tu, and the reduction of φ is more than that of φ TBC. Figure 14 illustrates the effect of TBC and Tu on the increment of overall cooling effectiveness, φ = φ TBC φ, at the three Tus. It is clear that when Tu increases, the increment of φ rises. The maximum φ exists at the hub of the vane, where φ can reach a value of 0.11 or the reduction of the metal surface temperature is about K at Tu = 20%. This phenomenon indicates that TBC can increase overall cooling effectiveness about 25% at the hub of the vane near the LE at the highest Tu. 6. CONCLUSIONS This paper presents a numerical investigation on the cooling performances in the LE and its vicinity of a film cooled vane with TBC at three Tus using 3D CFD technique with CHT analysis in FLUENT V.15. Only 1D heat conduction in TBC is considered because the thickness of TBC is very thin. Through the discussion and analysis of numerical results, the following conclusions can be drawn: 1. TBC is effective in the LE and its vicinity, especially when the level of Tu of the mainstream increases. 2. At each Tu, TBC at the region near the hub of the vane gives the most effective thermal protection against thermal load. 3. At the highest Tu, TBC can reduce the metal surface temperature at the region near the hub about K, this leads to the improvement of overall cooling effectiveness at that region about 25%. 4. In the vicinity of the LE, the ability of TBC on the PS is better than that on the SS, this phenomenon is clearer at higher Tus. 5. Near the exits of film holes, TBC may play a negative effect, because TBC may block the heat releasing from solid structure to the mixing fluid between cooling air and mainstream. Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2,

14 ACKNOWLEDGMENTS The research is supported by the Natural Science Foundation of China (contract no ). The first author is grateful to Chinese Academy of Sciences and World Academy of Sciences for the CAS-TWAS President s Fellowship Programme to support his PhD study and research at the University of Science and Technology of China. REFERENCES 1. Ni, R.H., Humber, W., Fan, G., Johnson, P.D., Downs, J., Clark, J.P. and Koch, J.P., Conjugate heat transfer analysis of a film-cooled turbine vane, in Proceedings of ASME Turbo Expo 2011: Turbine Technical Conference and Exposition, Vancouver, British Columbia, Canada, GT , June 6 10, Ni, R.H., Humber, W., Fan G., Clark, J.P., Anthony, R.J. and Johnson, J.J., Comparison of prediction from conjugate heat transfer analysis of a film-cooled turbine vane to experimental data, in Proceedings of ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, San Antonio, Texas, USA, GT , June 3 7, Mazur, Z., Hernandez-Rossette, A., Garcia-Illescas, R. and Luna-Ramirez, A., Analysis of conjugate heat transfer of a gas turbine first stage nozzle, Applied Thermal Engineering, Vol. 26, pp , Zhang, Q.B., Xu, H.Z., Wang, J.H., Li G., Wang, L., Wu, X.Y. and Ma, S.Y., Evaluation of CFD predictions using different turbulence models on a film cooled guide vane under experimental conditions, in Proceedings of ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, Montreal, Canada, GT , June 15 19, Timko, L.P., Energy efficient engine high pressure turbine component test performance report, NASA Lewis Research Center, NASA CR , Hylton, L.D., Mihelc, M.S., Turner, E.R., Nealy, D.A. and York, R.E., Analytical and experimental evaluation of the heat transfer distribution over the surface of turbine vanes, NASA Lewis Research Center, NASA CR , Yoshiara, T., Sasaki, D. and Nakahashi, K., Conjugate heat transfer simulation of cooled turbine blades using unstructured-mesh CFD solver, in Proceedings of AIAA 49th Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2011, Orlando, Florida, USA, AIAA , January 4 7, Zhang, H.J., Zou, Z.P., Li, Y., Ye, J. and Song, S.H., Conjugate heat transfer investigations of turbine vane based on transition models, Chinese Journal of Aeronautics, Vol. 26, No. 4, pp , Bohn, D.E. and Becker, V.J., A conjugate 3-D flow and heat transfer analysis of a thermal barrier cooled turbine guide vane, in Proceedings of ASME Turbo Expo 1998: The International Gas Turbine & Aeroengine Congress & Exhibition, 98-GT-89, Baldwin, B.S. and Lomax, H., Thin layer approximation and algebraic model for separated turbulent flows, in Proceedings of AIAA 16th Aerospace Sciences Meeting 1978, Huntsville, Alabama, USA, AIAA78 257, January 16 18, Bohn, D.E. and Tümmers, C., Numerical 3-D conjugate flow and heat transfer investigation of a transonic convection-cooled thermal barrier coated turbine guide vane with reduced cooling fluid mass flow, in Proceedings of ASME Turbo Expo 2003: Turbine Technical Conference and Exposition, Atlanta, Georgia, USA, GT , June 16 19, Alizadeh, M., Izadi, A. and Fathi, A., Sensitivity analysis on turbine blade temperature distribution using conjugate heat transfer simulation, ASME Journal of Turbomachinery, Vol. 136, pp , Undapalli, S. and Leylek, J.H., Ability of a popular turbulence model to capture curvature effects: a film cooling test case, in Proceedings of ASME Turbo Expo 2003: Turbine Technical Conference and Exposition, Atlanta, Georgia, USA, GT , June 16 19, Boyle, R.J., Ames, F.E. and Giel, P.W., Predictions for the effects of free stream turbulence on turbine blade heat transfer, in Proceedings of ASME Turbo Expo 2004: Turbine Technical Conference and Exposition, Vienna, Austria, GT , June 14 17, Mayhew, J.E., Baughn, J.W. and Byerley, A.R., The effect of freestream turbulence on film cooling adiabatic effectiveness, in Proceedings of ASME Turbo Expo 2002: Turbine Technical Conference and Exposition, Amsterdam, The Netherlands, GT , June 3 6, Transactions of the Canadian Society for Mechanical Engineering, Vol. 41, No. 2, 2017

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