Investigation on the Effects of Wake Rod to Film Cooling Hole Diameter Ratio in Unsteady Wake Studies

2011 ◽  
Author(s):  
Matthew Golsen ◽  
Mark Ricklick ◽  
Jay Kapat
Keyword(s):  
Film Cooling ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Unsteady Wake ◽  
Cooling Hole

Effects of an Embedded Vortex on Injectant From a Single Film-Cooling Hole in a Turbulent Boundary Layer

1990 ◽  
Vol 112 (3) ◽  
pp. 428-436 ◽  
Author(s):  
P. M. Ligrani ◽  
W. Williams
Keyword(s):  
Heat Transfer ◽  
Vortex Core ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Stream Velocity ◽  
Vortex Center ◽  
Injection Hole ◽  
Cooling Hole

Effects of embedded longitudinal vortices on heat transfer in turbulent boundary layers with injection from a single film-cooling hole are described. These results were obtained at a free-stream velocity of 10 m/s, with a film-cooling hole inclined 30 deg to the horizontal and a blowing ratio of about 0.50. The ratio of vortex core diameter to injection hole diameter was 1.58, and the ratio of circulation to injection velocity time hole diameter was about 3.16. Coolant distributions and spatially resolved heat transfer measurements indicate that injection hole centerlines must be at least 2.9–3.4 vortex core diameters away from the vortex center in the lateral direction to avoid significant alterations to wall heat transfer and distributions of film coolant. Under these circumstances, protection from film cooling is evident at least up to 55 hole diameters downstream of injection. When the injection hole is closer to the vortex center, secondary flows convect most injectant into the vortex upwash and thermal protection from film cooling is destroyed for streamwise locations from the injection hole greater than 17.5 hole diameters.

Enhanced Cooling Effectiveness in Full-Coverage Film Cooling System With Impingement Jets

2008 ◽  
Author(s):  
Sang Hyun Oh ◽  
Dong Hyun Lee ◽  
Kyung Min Kim ◽  
Moon Young Kim ◽  
Hyung Hee Cho
Keyword(s):  
Film Cooling ◽  
Cooling System ◽  
Hole Diameter ◽  
Cooling Effectiveness ◽  
Cooling Plate ◽  
Film Cooling Effectiveness ◽  
Impingement Jet ◽  
Full Coverage ◽  
Cooling Hole ◽  
Film Cooling Holes

An experimental investigation is conducted on the cooling effectiveness of full-coverage film cooled wall with impingement jets. Film cooling plate is made of stainless steel, thus the adiabatic film cooling effectiveness and the cooling effect of impingement jet underneath the film cooling plate are comprised in the cooling effectiveness. Infra-red camera is used to measure the temperature of film cooled surfaces. Experiments are conducted with different film cooling hole angles, such as 35° and 90°. Diameters of both film cooling holes and impinging jet holes are 5 mm. The jet Reynolds number base on the hole diameter (Red) ranges from 3,000 to 5,000 and equivalent blowing ratios (M) varies from 0.3 to 0.5, respectively. The distance between the injection plate and the film cooling plate is 1, 3 and 5 times of the hole diameter. The streamwise and spanwise hole spacing to the hole diameter ratio (p/d) are 3 for both the film cooling hole plate and the impingement jet hole plate. The 35° angled film cooling hole arrangement shows higher film cooling effectiveness than the 90° film cooling hole arrangement. As the blowing ratio increases, the cooling effectiveness is enhanced for both the 35° almost constant regardless of H/d, while H/d = 1 shows a minimum value for the angled film cooling hole.

Effects of Vortices With Different Circulations on Heat Transfer and Injectant Downstream of a Single Film-Cooling Hole in a Turbulent Boundary Layer

1990 ◽  
Author(s):  
P. M. Ligrani ◽  
C. S. Subramanian ◽  
D. W. Craig ◽  
P. Kaisuwan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Vortex Core ◽  
Film Cooling ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Injection Hole ◽  
Freestream Velocity ◽  
Cooling Hole

Results are presented which illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a single film-cooling hole in a turbulent boundary layer. Attention is focussed on the changes resulting as circulation magnitudes of the vortices are varied from 0.0 to 0.15 m**2/s. Mean temperature results are presented which show how injectant is distorted and redistributed by vortices, along with heat transfer measurements and mean velocity surveys. Injection hole diameter is 0.952 cm to give a ratio of vortex core diameter to hole diameter of about 1.5–1.6. The freestream velocity is maintained at 10 m/s, and the blowing ratio is approximately 0.5. The film-cooling hole is oriented 30 degrees with respect to the test surface. Stanton numbers are measured on a constant heat flux surface with a non-dimensional temperature parameter of about 1.5. Two different situations are studied: one where the injection hole is beneath the vortex downwash, and one where the injection hole is beneath the vortex upwash. For both cases, vortex centers pass well within 2.9 vortex core diameters of the centerline of the injection hole. To quantify the influences of the vortices on the injectant and local heat transfer, the parameter S is used, defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. When S is greater than 1.0–1.5, injectant is swept into the vortex upwash and above the vortex core by secondary flows, and Stanton number data show evidence of injectant beneath the vortex core and downwash near the wall for x/d only up to 33.6. For larger x/d, local Stanton numbers are augmented by the vortices by as much as 23 percent relative to film-cooled boundary layers with no vortices. When S is less than 1.0–1.5, some injectant remains near the wall beneath the vortex core and downwash where it continues to provide some thermal protection. In some cases, the protection provided by film cooling is augmented because of vortex secondary flows which cause extra injectant to accumulate near vortex upwash regions.

scholarly journals Small Diameter Film Cooling Hole Heat Transfer: The Influence of the Number of Holes

1989 ◽  
Author(s):  
G. E. Andrews ◽  
F. Bazdidi-Tehrani
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Film Cooling ◽  
Small Diameter ◽  
Diameter Ratio ◽  
Heat Transfer Correlation ◽  
Flow Acceleration ◽  
Overall Heat Transfer Coefficient ◽  
Cooling Hole ◽  
Air Passage

The overall surface averaged heat transfer was determined for air passing through arras of small diameter holes drilled at 90 through thin metal walls. The influence of the number of holes and hence of the pitch to diameter ratio, X/D, was investigated over the range 4.7 to 21 for a fixed hole size of 1.4 mm and hole L/D of 4.5. A transient cooling technique was used to determine the overall heat transfer coefficient for the cooling due to the air passage through the wall. It was shown that the dominant heat transfer was that on the hole approach surface area due to flow acceleration into the hole. The hole approach surface area was used in the heat transfer correlation. The results of the authors were combined with previous results for the variation of X/D at constant X to give a heat transfer correlation, independent of L/D.

Effects of Vortices With Different Circulations on Heat Transfer and Injectant Downstream of a Single Film-Cooling Hole in a Turbulent Boundary Layer

1991 ◽  
Vol 113 (3) ◽  
pp. 433-441 ◽  
Author(s):  
P. M. Ligrani ◽  
C. S. Subramanian ◽  
D. W. Craig ◽  
P. Kaisuwan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Vortex Core ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Injection Hole ◽  
Cooling Hole

Results are presented that illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a single film-cooling hole in a turbulent boundary layer. Attention is focused on the changes resulting as circulation magnitudes of the vortices are varied from 0.0 to 0.15 m2/s. Mean temperature results are presented that show how injectant is distorted and redistributed by vortices, along with heat transfer measurements and mean velocity surveys. Injection hole diameter is 0.952 cm to give a ratio of vortex core diameter to hole diameter of about 1.5–1.6. The free-stream velocity is maintained at 10 m/s, and the blowing ratio is approximately 0.5. The film-cooling hole is oriented 30 deg with respect to the test surface. Stanton numbers are measured on a constant heat flux surface with a nondimensional temperature parameter of about 1.5. Two different situations are studied: one where the injection hole is beneath the vortex downwash, and one where the injection hole is beneath the vortex upwash. For both cases, vortex centers pass well within 2.9 vortex core diameters of the centerline of the injection hole. To quantify the influences of the vortices on the injectant and local heat transfer, the parameter S is used, defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. When S is greater than 1.0–1.5, injectant is swept into the vortex upwash and above the vortex core by secondary flows, and Stanton number data show evidence of injectant beneath the vortex core and downwash near the wall for x/d only up to 33.6. For larger x/d, local Stanton numbers are augmented by the vortices by as much as 23 percent relative to film-cooled boundary layers with no vortices. When S is less than 1.0–1.5, some injectant remains near the wall beneath the vortex core and downwash where it continues to provide some thermal protection. In some cases, the protection provided by film cooling is augmented because of vortex secondary flows, which cause extra injectant to accumulate near vortex upwash regions.

Numerical Analysis of Film-Cooling Performance and Optimization for a Novel Shaped Film-Cooling Hole

2012 ◽  
Author(s):  
Ki-Don Lee ◽  
Sun-Min Kim ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Density Ratio ◽  
Lateral Spreading ◽  
Diameter Ratio ◽  
The Novel ◽  
Cooling Performance ◽  
Cooling Hole ◽  
Shaped Hole ◽  
Film Cooling Holes

In the present work, a numerical study on a novel shaped film-cooling hole has been performed. The novel shaped hole is designed to enhance lateral spreading of coolant on the cooling surface. The film-cooling performance of the novel shaped hole is compared with the fan, laidback fan, and dumbbell shaped film-cooling holes at density ratio of 1.75 in the range of blowing ratio from 0.5 to 2.5. The optimization of the novel shaped hole has been carried out to increase film-cooling effectiveness with four design variables, i.e., lateral expansion of the diffuser, forward expansion angle of the hole, length to diameter ratio of the hole, and pitch to diameter ratio of the hole. To optimize the hole shape, the radial basis neural network model is constructed and sequential quadratic programming is used to find optimal point from the surrogate model. The novel shaped hole shows remarkably improved film-cooling performance in comparison with the other film-cooling holes. The novel shaped hole modified by the optimization gives enhanced performance in comparison with the reference geometry.

Effects of an Embedded Vortex on Injectant From a Single Film-Cooling Hole in a Turbulent Boundary Layer

1989 ◽  
Author(s):  
P. M. Ligrani ◽  
W. Williams
Keyword(s):  
Heat Transfer ◽  
Vortex Core ◽  
Film Cooling ◽  
Thermal Protection ◽  
Hole Diameter ◽  
Secondary Flows ◽  
Vortex Center ◽  
Injection Hole ◽  
Freestream Velocity ◽  
Cooling Hole

Effects of embedded longitudinal vortices on heat transfer in turbulent boundary layers with injection from a single film cooling hole are described. These results were obtained at a freestream velocity of 10 m/s, with a film cooling hole inclined 30 degrees to horizontal and a blowing ratio of about 0.50. The ratio of vortex core diameter to injection hole diameter was 2.14, and the ratio of circulation to injection velocity times hole diameter was about 2.8. Coolant distributions and spatially resolved heat transfer measurements indicate that injection hole centerlines must be a least 2.0–2.5 vortex core diameters away from the vortex center in the lateral direction to avoid significant alterations to wall heat transfer and distributions of film coolant. Under these circumstances, protection from film cooling is evident at least up to 55 hole diameters downstream of injection. When the injection hole is closer to the vortex center, secondary flows convect most injectant into the vortex upwash and thermal protection from film cooling is destroyed for streamwise locations from the injection hole greater than 17.5 hole diameters.

Film Cooling Effectiveness Due to Discrete Holes Within a Transverse Surface Slot

2002 ◽  
Author(s):  
Ronald S. Bunker
Keyword(s):  
Test Section ◽  
Film Cooling ◽  
Flow Direction ◽  
Wind Tunnel Test ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Spanwise Direction ◽  
Protective Film ◽  
Surface Geometry ◽  
Film Cooling Effectiveness

The goal of many turbine airfoil film cooling schemes is the achievement of a tangentially injected 2D layer of protective film over the surface. In common nomenclature, this is referred to as 2D slot film cooling, which can achieve adiabatic effectiveness levels approaching unity at the injection location. Since continuous and uninterrupted slots are not structurally feasible in the high pressure turbine components, other approximate film cooling geometries have been sought. The present study examines two film cooling geometries which are formed by the combination of internal discrete film holes feeding continuous 2D surface slots. Experiments have been performed within a flat plate wind tunnel test section, which includes an accelerating freestream condition to model the surface of a turbine airfoil. As suggested by the experiments of Wang et al. [1], a normal 2D surface slot is located transverse to the mainstream flow direction. The slot is fed by a row of discrete coolant supply holes oriented in the spanwise direction with inclination angle of 30-degrees, pitch-to-diameter ratio of 3.57, and length-to-diameter ratio of 5.7. The slot depth-to-hole diameter ratio is S/D of 3. Two such slots were tested, one with axial width-to-hole diameter ratio of 1.13, and the other with ratio of 1.5. Tests were conducted for supply hole blowing ratios of 0.75 to 4, density ratios of 1.8, and a freestream approach turbulence intensity of 4.5%. The holes-within-slot film effectiveness data are compared with both axial and radial film data, ie. S/D equal to zero, obtained in the same test section. The holes-in-slot geometries demonstrate two important characteristics, (1) a relative insensitivity of the adiabatic film effectiveness to blowing rate, and (2) no observed film blow-off at high blowing rates. In addition, a novel film cooling arrangement is demonstrated in which the surface slot is very shallow, forming a narrow trench with S/D of only 0.43. It is shown that this novel surface geometry yields the best film effectiveness of all cases tested.

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