Film Cooling with Surface Enhancements

Film cooling has been studied for many decades but the study of film cooling using surface enhancements is still relatively new. In this project numerical analysis has been carried out to find the film cooling performance of ramp, flow aligned blocker, and trench surface enhancements in comparison to the standard elliptical injection configuration. A comparative study of the effects of the blowing ratio has also been carried out for each surface enhancement configuration. In addition to calculating and discussing the centerline and laterally averaged film cooling effectiveness results, detailed analysis of the flow and temperature field of each configuration is also presented. In the end the laterally averaged film cooling effectiveness results suggested that flow aligned blockers would provide the greatest film cooling improvements with closer hole spacing.

Film Cooling with Surface Enhancements

10.32920/ryerson.14646696.v1 ◽

2021 ◽

Author(s):

Xavier Chang

Keyword(s):

Temperature Field ◽

Numerical Analysis ◽

Comparative Study ◽

Detailed Analysis ◽

Film Cooling ◽

Cooling Effectiveness ◽

Surface Enhancement ◽

Cooling Performance ◽

Investigations on the Influence of Rib Orientation Angle on Film Cooling Performance of Compound Holes

Volume 5C: Heat Transfer ◽

10.1115/gt2018-75794 ◽

2018 ◽

Author(s):

Lin Ye ◽

Cun-liang Liu ◽

Hai-yong Liu ◽

Hui-ren Zhu ◽

Jian-xia Luo

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Film Cooling ◽

Discharge Coefficient ◽

Orientation Angle ◽

Cooling Effectiveness ◽

Cooling Performance ◽

To investigate the effects of the inclined ribs on internal flow structure in film hole and the film cooling performance on outer surface, experimental and numerical studies are conducted on the effects of rib orientation angle on film cooling of compound cylindrical holes. Three coolant channel cases, including two ribbed cross-flow channels (135° and 45° angled ribs) and the plenum case, are studied under three blowing ratios (0.5, 1.0 and 2.0). 2D contours of film cooling effectiveness as well as heat transfer coefficient were measured by transient liquid crystal measurement technique (TLC). The steady RANS simulations with realizable k-ε turbulence model and enhanced wall treatment were performed. The results show that the spanwise width of film coverage is greatly influenced by the rib orientation angle. The spanwise width of the 45° rib case is obviously larger than that of the 135° rib case under lower blowing ratios. When the blowing ratio is 1.0, the area-averaged cooling effectiveness of the 135° rib case and the 45° rib case are higher than that of the plenum case by 38% and 107%, respectively. With the increase of blowing ratio, the film coverage difference between different rib orientation cases becomes smaller. The 45° rib case also produces higher heat transfer coefficient, which is higher than the 135° rib case by 3.4–8.7% within the studied blowing ratio range. Furthermore, the discharge coefficient of the 45° rib case is the lowest among the three cases. The helical motion of coolant flow is observed in the hole of 45° rib case. The jet divides into two parts after being blown out of the hole due to this motion, which induces strong velocity separation and loss. For the 135° rib case, the vortex in the upper half region of the secondary-flow channel rotates in the same direction with the hole inclination direction, which leads to the straight streamlines and thus results in lower loss and higher discharge coefficient.

Numerical Analysis of Film Cooling Effectiveness under Variable Blowing Ratio and Injection Angles

Proceedings of the 3rd World Congress on Momentum, Heat and Mass Transfer ◽

10.11159/enfht18.132 ◽

2018 ◽

Author(s):

Mohammed Al-Hemyari ◽

Mohammad O. Hamdan ◽

Mehmet F. Orhan

Keyword(s):

Numerical Analysis ◽

Film Cooling ◽

Cooling Effectiveness ◽

Experimental Investigation and Optimal Design on the Film Cooling Performance of Fan-Shaped Hole With Vortex Generator Fed by Crossflow

10.1115/gt2021-59144 ◽

2021 ◽

Author(s):

Jie Wang ◽

Chao Zhang ◽

Xuebin Liu ◽

Liming Song ◽

Jun Li ◽

...

Keyword(s):

Reynolds Number ◽

Film Cooling ◽

Vortex Generator ◽

Optimized Design ◽

Combined Model ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Blowing Ratio ◽

Shaped Hole

Abstract Aiming at investigating the effects of crossflow and vortex generator on film cooling characteristics of fan-shaped hole, the film cooling performance was measured experimentally by infrared camera. The blowing ratio is fixed at 0.5 and 1.5. The Reynolds number of the mainstream based on the hole diameter remains at 7000 and the inlet Reynolds number of crossflow is 40000. The experimental results show that the film cooling performance becomes better when the blowing ratio increases from 0.5 to 1.5 for each model, and the film cooling performance becomes worse under the influence of crossflow. When the blowing ratio is 1.5, the area-averaged film cooling effectiveness of the fan-shaped hole model with vortex generator decreases by 16.6% because of the influence of crossflow. The combined model always performs better compared with the model without vortex generator under all working conditions. When the blowing ratio becomes 1.5, under the influence of crossflow, the area-averaged film cooling effectiveness of the combined model could increase by 14.8%, compared with the model without vortex generator. To further improve the film cooling performance, the global optimization algorithm based on the Kriging method and the CFD technology are coupled to optimize the combined model under crossflow condition at the high blowing ratio, and the optimized design is verified by experiments. The experimental results show that the area-averaged film cooling effectiveness of the optimized design increases by 17.8% compared with the reference model.

Effects of Blowing Ratio on Multiple Shallow Angle Film Cooling Holes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.225.49 ◽

2012 ◽

Vol 225 ◽

pp. 49-54 ◽

Cited By ~ 2

Author(s):

Kamil Abdullah ◽

Ken Ichi Funazaki

Keyword(s):

Temperature Field ◽

Surface Temperature ◽

Film Cooling ◽

Cooling Effectiveness ◽

Ir Camera ◽

Blowing Ratio ◽

Hole Configuration ◽

The Common ◽

Film Cooling Holes

This paper presents the investigation on the effects of the blowing ratio of multiple shallow angle film cooling holes. Multiple film cooling holes having a shallow hole angle (θ = 20°), arranged to perform in-line hole configuration has been considered in the present study. The investigation focuses on the effects of high blowing ratio of the film cooling effectiveness which have been carried out at ReD= 3100 and BR = 2.0, 3.0 and 4.0. The experiments make use of the IR camera in capturing the surface temperature to determine the film cooling effectiveness. The contours of the film cooling effectiveness distribution together with plots on laterally average film cooling effectiveness along the x/D are presented. The discussions have been made with a support of the temperature field captured at x/D = 3, 13, 23, and 33. The results clearly show the benefit of the employment of shallow hole angle (θ = 20°) at high blowing ratio which is much more superior in comparison to the common hole configuration (θ = 35°).

Enhancement of Film Cooling Performance at the Leading Edge of Turbine Blade

Volume 3: Heat Transfer, Parts A and B ◽

10.1115/gt2006-90321 ◽

2006 ◽

Cited By ~ 6

Author(s):

K.-S. Kim ◽

Youn J. Kim ◽

S.-M. Kim

Keyword(s):

Turbine Blade ◽

Film Cooling ◽

Density Ratio ◽

Leading Edge ◽

Cylindrical Body ◽

Spanwise Direction ◽

Cooling Effectiveness ◽

Cooling Performance ◽

To enhance the film cooling performance in the vicinity of the turbine blade leading edge, the flow characteristics of the film-cooled turbine blade have been investigated using a cylindrical body model. The inclination of the cooling holes is along the radius of the cylindrical wall and 20 deg relative to the spanwise direction. Mainstream Reynolds number based on the cylinder diameter was 1.01×105 and 0.69×105, and the mainstream turbulence intensities were about 0.2% in both Reynolds numbers. CO2 was used as coolant to simulate the effect of density ratio of coolant-to-mainstream. Furthermore, the effect of coolant flow rates was studied for various blowing ratios of 0.4, 0.7, 1.1, and 1.4, respectively. In experiment, spatially-resolved temperature distributions along the cylindrical body surface were visualized using infrared thermography (IRT) in conjunction with thermocouples, digital image processing, and in situ calibration procedures. This comparison shows the results generated to be reasonable and physically meaningful. The film cooling effectiveness of current measurement (0.29 mm × 0.33 min per pixel) presents high spatial and temperature resolutions compared to other studies. Results show that the blowing ratio has a strong effect on film cooling effectiveness and the coolant trajectory is sensitive to the blowing ratio. The local spanwise-averaged effectiveness can be improved by locating the first-row holes near the second-row holes.

Optimal Arrangement of Combined-Hole for Improving Film Cooling Effectiveness

Volume 3B: Heat Transfer ◽

10.1115/gt2013-94561 ◽

2013 ◽

Cited By ~ 1

Author(s):

Chang Han ◽

Zhongran Chi ◽

Jing Ren ◽

Hongde Jiang

Keyword(s):

Film Cooling ◽

Optimal Arrangement ◽

Aerodynamic Parameter ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Blowing Ratio ◽

Lateral Distance ◽

Batch Simulation ◽

Compound Angle

Film cooling technique is widely used to protect the components from being destroyed by hot mainstream in a modern gas turbine. Combining round-holes is a promising way of improving film cooling effectiveness. A batch simulation of 75 cases focusing on the arrangements of combined-hole unit with two holes for improving film cooling performance are carried out in this work, and the influence of an aerodynamic parameter, blowing ratio, is considered as well. The lateral distance and compound-angle of the two holes have relative influence on the film cooling performance of a combined-hole unit. At a small lateral distance, the film cooling effectiveness increases significantly as compound-angle increases, whereas it deteriorates at a large distance and it is barely influenced by compound-angle at a medium lateral distance. Asymmetrical compound-angle is introduced aiming to balance the two branches of vortexes, but its film cooling performance is not as good as expected. The general film cooling effectiveness is in the position between that of the adjacent symmetrical compound-angle. Besides, the optimal arrangement of combined-hole unit for improving film cooling performance is relative to local aerodynamic parameter. The combination of the lateral distance of the two holes with their compound-angles for the highest film cooling effectiveness is different at different blowing ratios.

Flow Dynamics and Film Cooling Effectiveness on a Non-Axisymmetric Contour Endwall in a Two-Dimensional Cascade Passage

Volume 3: Heat Transfer, Parts A and B ◽

10.1115/gt2009-60236 ◽

2009 ◽

Cited By ~ 5

Author(s):

Gazi I. Mahmood ◽

Ross Gustafson ◽

Sumanta Acharya

Keyword(s):

Temperature Field ◽

Flow Field ◽

Film Cooling ◽

Free Stream ◽

Flow Behavior ◽

Three Dimensional ◽

Cooling Effectiveness ◽

Cooling Flow ◽

The measured flow field and temperature field near a three-dimensional asymmetric contour endwall employed in a linear blade cascade are presented with and without film-cooling flow on the endwall. Flow field temperature and Nusselt number distributions along the asymmetric endwall with wall heating and no film-cooling flow are also reported to show local high heat transfer region on the endwall and justify the locations of the coolant holes. Adiabatic film-cooling effectiveness along the endwall is then measured to indicate the local effects of the coolant jets. The near endwall flow field and temperature field provide the coolant flow behavior and the interaction of coolant jets with the boundary layer flow. Thus, the local film-cooling effectiveness can be explained with the coolant jet trajectories. The measurements are obtained at the Reynolds number of 2.30×105 based on blade actual chord and inlet velocity, coolant-to-free stream temperature ratio of 0.93, and coolant-to-free stream density ratio of 1.06. The cascade employs the hub side blade section and passage geometry of the first stage rotor of GE-E3 turbine engine. The contour endwall profile is employed on the bottom endwall only in the cascade. The blowing ratio of the film-cooling flow varies from 1.0 to 2.4 from 71 discrete cylindrical holes located in the contour endwall. The three-dimensional profile of the endwall varies in height in both the pitchwise and axial directions. The flow field is quantified with the streamwise vorticity and turbulent intensity, pitchwise static pressure difference, flow yaw angle, and pitchwise velocity. Both the flow field and temperature data indicate that the coolant jets cover more distance in the pitchwise and axial direction in the passage as the blowing ratio increases. Thus, the local and average film-cooling effectiveness increase with the blowing ratio.

Experimental Investigation on the Flat-Plate Film Cooling Enhancement Using the Vortex Generator Downstream for the Cylindrical Hole and Fan-Shaped Hole Configurations

Volume 5B: Heat Transfer ◽

10.1115/gt2019-90671 ◽

2019 ◽

Author(s):

Chao Zhang ◽

Jie Wang ◽

Xin Luo ◽

Liming Song ◽

Jun Li ◽

...

Keyword(s):

Film Cooling ◽

Vortex Generator ◽

Cylindrical Hole ◽

Combined Model ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Blowing Ratio ◽

Shaped Hole ◽

Hole Model

Abstract In our experiments, the film cooling performance of the configurations combined the different hole with the vortex generator was investigated experimentally, measured by the infrared camera. Four different configurations were studied at the blowing ratio varying at M = 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. In all cases, the Reynold number of the mainstream based on the hole diameter remained at Re = 8000, and the density ratio kept at DR = 1.7. Experimental results show that for the two models combining the cylindrical hole and fan-shaped hole with the vortex generator respectively, the film cooling performance becomes better when the blowing ratio increases from M = 0.5 to M = 2.0, and then decreases when the blowing ratio increases from M = 2.0 to M = 3.0. The model combining the fan-shaped hole with the vortex generator performs the best among the four models at each blowing ratio. Its film attachment holds the most extensive lateral distribution and its overall film cooling effectiveness could keep at a high level at a wide range of blowing ratios from M = 1.0 to M = 3.0. The combined model of the fan-shaped hole could improve the area-averaged film effectiveness at most 25.5% than that of the single hole model at M = 2.0. Moreover, the combined model of the cylindrical hole could improve the area-averaged film cooling effectiveness at most 431% than that of the single cylindrical hole model at M = 3.0.

Experimental Investigation of Film Cooling Performance on Blade Endwall with Diffusion Slot Holes and Stator-Rotor Purge Flow

Journal of Turbomachinery ◽

10.1115/1.4050120 ◽

2021 ◽

pp. 1-28

Author(s):

Zhi-Qiang Yu ◽

Jianjun Liu ◽

Chen Li ◽

Baitao An ◽

Guang-Yao Xu

Keyword(s):

Film Cooling ◽

Flow Direction ◽

Cross Flow ◽

Orientation Angle ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Pressure Surface ◽

Blowing Ratio ◽

Shaped Hole

Abstract This paper focuses on the influences of the discrete hole shape and layout on the blade endwall film cooling effectiveness. The diffusion slot hole was first applied to the blade endwall and compared with the fan-shaped hole. The effect of upstream purge slot injection on the film cooling performance of the discrete hole was also investigated. Experiments were performed in a linear cascade with a exit Reynolds number of 2.64×105. The film cooling effectiveness on the blade endwall were measured by the pressure sensitive paint technique. Results indicate that the diffusion slot hole significantly increases the film cooling effectiveness on the blade endwall compared to the fan-shaped hole, especially at high blowing ratio. The maximum relative increment of the cooling effectiveness is over 40%. The layout with the discrete holes arranged lining up with the tangent direction of the blade profile offset curves exhibits a comparable film cooling effectiveness with the layout with the discrete holes arranged according to the cross-flow direction. The film cooling effectiveness on the pressure surface corner is remarkably enhanced by deflecting the hole orientation angle towards the pressure surface. The combination of purge slot and diffusion slot holes supplies a full coverage film cooling for the entire blade endwall at coolant mass flow ratio of the purge slot of 1.5% and blowing ratio of 2.5. In addition, the slot injection leads to a non-negligible influence on the cooling performance of the discrete holes near the separation line.