Film Cooling With Compound Angle Holes: Heat Transfer

1994 ◽  
Author(s):  
Basav Sen ◽  
Donald L. Schmidt ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Momentum Flux ◽  
High Momentum ◽  
Transfer Rates ◽  
Compound Angle ◽  
Large Compound ◽  
The Heat Transfer Coefficient

Heat transfer coefficients have been measured for film cooling injection from a single row of holes laterally directed with a compound angle of 60°. Two hole configurations were tested, round holes and holes with a diffusing expansion at the exit. Streamwise directed round holes were also tested as a basis for comparison. All the holes were inclined at 35° with respect to the surface. The density ratio was 1.0, momentum flux ratios ranged from I = 0.16 to 3.9 and mass flux ratios from M = 0.4 to 2.0. Results are presented in terms of hf/h0, the ratio of film cooling heat transfer coefficient to the heat transfer coefficient for the undisturbed turbulent boundary layer at the same location. Results indicate that for the streamwise directed holes, the heat transfer rates are close to the levels that exist without injection. Similarly, at low momentum flux ratio, holes with a large compound angle had little effect on heat transfer rates. But at high momentum flux ratios, holes with a large compound angle had significantly increased heat transfer levels. The results were combined with adiabatic effectiveness results to evaluate the overall performance of the three geometries. It is shown that for evaluation of film cooling performance with compound angle injection, especially at high momentum flux ratios, it is critical to know the heat transfer coefficient, as the adiabatic effectiveness alone does not determine the performance. Compound angle injection at high momentum flux ratios gives higher effectiveness values than streamwise directed holes, but the higher heat transfer levels result in poorer overall performance.

Film Cooling With Compound Angle Holes: Heat Transfer

1996 ◽  
Vol 118 (4) ◽  
pp. 800-806 ◽  
Author(s):  
B. Sen ◽  
D. L. Schmidt ◽  
D. G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Momentum Flux ◽  
High Momentum ◽  
Transfer Rates ◽  
Compound Angle ◽  
Large Compound ◽  
The Heat Transfer Coefficient

Heat transfer coefficients have been measured for film cooling injection from a single row of holes laterally directed with a compound angle of 60 deg. Two hole configurations were tested, round holes and holes with a diffusing expansion at the exit. Streamwise-directed round holes were also tested as a basis for comparison. All the holes were inclined at 35 deg with respect to the surface. The density ratio was 1.0, momentum flux ratios ranged from I = 0.16 to 3.9, and mass flux ratios ranged from M = 0.4 to 2.0. Results are presented in terms of hf/ho, the ratio of film cooling heat transfer coefficient to the heat transfer coefficient for the undisturbed turbulent boundary layer at the same location. Results indicate that for the streamwise directed holes, the heat transfer rates are close to the levels that exist without injection. Similarly, at low momentum flux ratio, holes with a large compound angle had little effect on heat transfer rates. However, at high momentum flux ratios, holes with a large compound angle had significantly increased heat transfer levels. The results were combined with adiabatic effectiveness results to evaluate the overall performance of the three geometries. It is shown that for evaluation of film cooling performance with compound angle injection, especially at high momentum flux ratios, it is critical to know the heat transfer coefficient, as the adiabatic effectiveness alone does not determine the performance. Compound angle injection at high momentum flux ratios gives higher effectiveness values than streamwise-directed holes, but the higher heat transfer levels result in poorer overall performance.

Heat Transfer Coefficient Augmentation for a Shaped Film Cooling Hole at a Range of Compound Angles

2020 ◽  
pp. 1-30
Author(s):  
Shane Haydt ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Constant Heat Flux ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

Abstract Film cooling holes with shaped diffusers are used to efficiently deliver coolant to the surface of a gas turbine part to keep metal temperatures low. Reducing the heat flux into a component, relative to a case with no coolant injection, is the ultimate goal of film cooling. This reduction in heat flux is primarily achieved via a lower driving temperature at the wall for convection, represented by the adiabatic effectiveness. Another important consideration, however, is how the disturbance to the flowfield and thermal field caused by the injection of coolant augments the heat transfer coefficient. The present study examines the spatially-resolved heat transfer coefficient augmentation, measured using a constant heat flux foil and IR thermography, for a shaped film cooling hole at a range of compound angles. Results show that the heat transfer coefficient increases with compound angle and with blowing ratio. Due to the unique asymmetric flowfield of a compound angle hole, a significant amount of augmentation occurs to the side of the film cooling jet, where very little coolant is present. This causes local regions of increased heat flux, which is counter to the goal of film cooling. Heat transfer results are compared with adiabatic effectiveness and flowfield measurements from a previous study.

Influence of Compound Angle on Adiabatic Film Cooling Effectiveness and Heat Transfer Coefficient for a Row of Shaped Film Cooling Holes

2005 ◽  
Author(s):  
Dennis Brauckmann ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Test Plate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

The measurement of adiabatic film cooling effectiveness data and heat transfer coefficient data for a row of fanshaped film cooling holes at different compound angles is presented in this paper. The measurements are performed at engine-like temperature ratios in a hot gas test facility on a flat test plate. For the film cooling geometry, a row of five laidback-fanshaped holes was used. The temperature distribution on the flat plate is measured using infrared-thermography (IR). Steady state measurements are used to obtain the film cooling effectiveness. For the determination of the heat transfer coefficient ratio with and without film cooling on the test plate, a transient measurement technique is applied. Results for both the adiabatic film cooling effectiveness and the heat transfer coefficient ratio are given. The influence of different blowing ratios on the injection with compound angles of 0°, 30° and 45° will be discussed. From this study, the increasing compound angle showed only small effects on the pitch-wise lateral averaged adiabatic film cooling effectiveness but increased the heat transfer on the film cooled flat plate with coolant injection.

Heat Transfer Coefficient Augmentation for a Shaped Film Cooling Hole at a Range of Compound Angles

2019 ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Constant Heat Flux ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

Abstract Shaped film cooling holes are used to efficiently deliver coolant to the surface of a gas turbine part to keep metal temperatures low. The ultimate goal of film cooling is to reduce the heat flux into a component, relative to a case with no coolant injection. This reduction in heat flux is primarily achieved via a lower driving temperature at the wall for convection, represented by the adiabatic effectiveness. Another important consideration, however, is how the disturbance to the flowfield and thermal field caused by the injection of coolant augments the heat transfer coefficient. The present study examines the spatially-resolved heat transfer coefficient augmentation for a shaped film cooling hole at a range of compound angles, using a constant heat flux foil and IR thermography. Results show that the heat transfer coefficient increases with compound angle and with blowing ratio. Due to the unique asymmetric flowfield of a compound angle hole, a significant amount of augmentation occurs to the side of the film cooling jet, where very little coolant is present. This causes local regions of increased heat flux, which is counter to the goal of film cooling. Heat transfer results are compared with adiabatic effectiveness and flowfield measurements from a previous study.

Film Cooling Heat Transfer: Shaped and Compound Angle Hole Injection

1998 ◽  
Author(s):  
David J. Seager ◽  
James A. Liburdy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Hole Shaping ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

To further understand the effect of compound angle holes and hole shaping on film cooling, detailed heat transfer measurements were obtained using a hue based thermochromic liquid crystal method. This technique is fully described based on its development for film cooling applications. The data were analyzed to determine both the full surface adiabatic effectiveness and the heat transfer coefficient. The compound angles that are presented consist of holes aligned at 0° (streamwise) and 45° to the main cross flow direction. Hole shaping variations from the traditional cylindrically shaped hole include forward diffused and laterally diffused hole configurations. The length to diameter ratio (L/D) was 4.0, the pitch to diameter ratio (P/D) was 3.0, and the inclination angle (α) was 35°. A density ratio (DR) of 1.55 was obtained for all tests using carbon dioxide as the injection fluid into an air stream. For each set of conditions the blowing ratio (M) was varied to be 0.88, 1.25, and 1.88. Adiabatic effectiveness was obtained using a steady state test, while an active heating surface (constant, uniform heat flux) was used to determine the heat transfer coefficient using a transient method.

scholarly journals Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

1997 ◽  
Author(s):  
Vijay K. Garg ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computer Time ◽  
Suction Surface ◽  
The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

Freestream Flow Effects on Film Effectiveness and Heat Transfer Coefficient Augmentation for Compound Angle Shaped Holes

2017 ◽  
Author(s):  
Joshua B. Anderson ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Gas Turbines ◽  
Boundary Layer Thickness ◽  
Adiabatic Effectiveness ◽  
Compound Angle

The use of compound-angled shaped film cooling holes in gas turbines provides a method for cooling regions of extreme curvature on turbine blades or vanes. These configurations have received surprisingly little attention in the film cooling literature. In this study, a row of laid-back fanshaped holes based on an open-literature design, were oriented at a 45-degree compound angle to the approaching freestream flow. In this study, the influence of the approach flow boundary layer thickness and character were experimentally investigated. A trip wire and turbulence generator were used to vary the boundary layer thickness and freestream conditions from a thin laminar boundary layer flow to a fully turbulent boundary layer and freestream at the hole breakout location. Steady-state adiabatic effectiveness and heat transfer coefficient augmentation were measured using high-resolution IR thermography, which allowed the use of an elevated density ratio of DR = 1.20. The results show adiabatic effectiveness was generally lower than for axially-oriented holes of the same geometry, and that boundary layer thickness was an important parameter in predicting effectiveness of the holes. Heat transfer coefficient augmentation was highly dependent on the freestream turbulence levels as well as boundary layer thickness, and significant spatial variations were observed.

Effects of Free-Stream Turbulence and Surface Roughness on Film Cooling

1996 ◽  
Author(s):  
Donald L. Schmidt ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Momentum Flux ◽  
Free Stream ◽  
Cooling Performance ◽  
Free Stream Turbulence ◽  
Adiabatic Effectiveness

A flat plate test section was used to study how high free-stream turbulence with large turbulence length scales, representative of the turbine environment, affect the film cooling adiabatic effectiveness and heat transfer coefficient for a round hole film cooling geometry. This study also examined cooling performance with combined high free-stream turbulence and a rough surface which simulated the roughness representative of an in-service turbine. The injection was from a single row of film cooling holes with injection angle of 30°. The density ratio of the injectant to the mainstream was 2.0 for the adiabatic effectiveness tests, and 1.0 for the heat transfer coefficient tests. Streamwise and lateral distributions of adiabatic effectiveness and heat transfer coefficients were obtained at locations from 2 to 90 hole diameters downstream. At small to moderate momentum flux ratios, which would normally be considered optimum blowing conditions, high free-stream turbulence dramatically decreased adiabatic effectiveness. However, at large momentum flux ratios, conditions for which the film cooling jet would normally be detached, high free-stream turbulence caused an increase in adiabatic effectiveness. The combination of high free-stream turbulence with surface roughness resulted in an increase in adiabatic effectiveness relative to the smooth wall with high free-stream turbulence. Heat transfer rates were relatively unaffected by a film cooling injection. The key result from this study was a substantial increase in the momentum flux ratios for maximum film cooling performance which occurred for high free-stream turbulence and surface roughness conditions which are more representative of actual turbine conditions.

Investigation on the Leading Edge Film Cooling of Counter-Inclined Cylindrical and Laid-Back Holes With and Without Impingement: Part II — Heat Transfer Coefficient

2018 ◽  
Author(s):  
Rui-dong Wang ◽  
Cun-liang Liu ◽  
Hai-yong Liu ◽  
Hui-ren Zhu ◽  
Qi-ling Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
The Heat Transfer Coefficient ◽  
Tube Structure

Heat transfer of the counter-inclined cylindrical and laid-back holes with and without impingement on the turbine vane leading edge model are investigated in this paper. To obtain the film cooling effectiveness and heat transfer coefficient, transient temperature measurement technique on complete surface based on double thermochromic liquid crystals is used in this research. A semi-cylinder model is used to model the vane leading edge which is arranged with two rows of holes. Four test models are measured under four blowing ratios including cylindrical film holes with and without impingement tube structure, laid-back film holes with and without impingement tube structure. This is the second part of a two-part paper, the first part paper GT2018-76061 focuses on film cooling effectiveness and this study will focus on heat transfer. Contours of surface heat transfer coefficient and laterally averaged result are presented in this paper. The result shows that the heat transfer coefficient on the surface of the leading edge is enhanced with the increase of blowing ratio for same structure. The shape of the high heat transfer coefficient region gradually inclines to span-wise direction as the blowing ratio increases. Heat transfer coefficient in the region where the jet core flows through is relatively lower, while in the jet edge region the heat transfer coefficient is relatively higher. Compared with cylindrical hole, laid-back holes give higher heat transfer coefficient. Meanwhile, the introduction of impingement also makes heat transfer coefficient higher compared with cross flow air intake. It is found that the heat transfer of the combination of laid-back hole and impingement tube can be very high under large blowing ratio which should get attention in the design process.

Heat Transfer Measurements Downstream of Trenched Film Cooling Holes Using a Novel Optical Two-Layer Measurement Technique

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Peter Schreivogel ◽  
Michael Pfitzner
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Slight Reduction ◽  
Superposition Method ◽  
Cooling Effectiveness ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

A new approach for steady-state heat transfer measurements is proposed. Temperature distributions are measured at the surface and a defined depth inside the wall to provide boundary conditions for a three-dimensional heat flux calculation. The practical application of the technique is demonstrated by employing a superposition method to measure heat transfer and film cooling effectiveness downstream of two different 0.75D deep narrow trench geometries and cylindrical holes. Compared to the cylindrical holes, both trench geometries lead to an augmentation of the heat transfer coefficient supposedly caused by the highly turbulent attached cooling film emanating from the trenches. Areas of high heat transfer are visible, where recirculation bubbles or large amounts of coolant are expected. Increasing the density ratio from 1.33 to 1.60 led to a slight reduction of the heat transfer coefficient and an increased cooling effectiveness. Both trenches provide a net heat flux reduction (NHFR) superior to that of cylindrical holes, especially at the highest momentum flux ratios.

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