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.

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.

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.

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.

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

1991 ◽  
Vol 113 (1) ◽  
pp. 79-90 ◽  
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 ◽  
Core Diameter ◽  
Film Cooling Holes

Results are presented that illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a row of film-cooling holes 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. Film-cooling holes are 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 middle injection hole is beneath the vortex downwash, and one where the middle injection hole is beneath the vortex upwash. For both cases, vortex centers pass within 2.9–3.4 vortex core diameters of the centerline of the middle injection hole. To quantify the influences of the vortices on the injectant, two new parameters are introduced. S is defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. S1 is similarly defined except vortex core diameter replaces injection hole diameter. The perturbation to film injectant and local heat transfer is determined by the magnitudes of S and S1. When S is greater than 1–1.5 or when S1 is greater than 0.7–1.0, 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 about 17.5. For larger x/d, local hot spots are present, and the vortices cause local Stanton numbers to be augmented by as much as 25 percent in the film-cooled boundary layers. When S and S1 are less than these values, 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 upwash regions.

Effects of a Reacting Cross-Stream on Turbine Film Cooling

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Wesly S. Anderson ◽  
Marc D. Polanka ◽  
Joseph Zelina ◽  
Dave S. Evans ◽  
Scott D. Stouffer ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Thermal Protection ◽  
Critical Role ◽  
Cylindrical Hole ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Secondary Combustion ◽  
Cooling Hole ◽  
Reactor Operating

Film cooling plays a critical role in providing effective thermal protection to components in modern gas turbine engines. A significant effort has been undertaken over the last 40 years to improve the distribution of coolant and to ensure that the airfoil is protected by this coolant from the hot gases in the freestream. This film, under conditions with high fuel-air ratios, may actually be detrimental to the underlying metal. The presence of unburned fuel from an upstream combustor may interact with this oxygen rich film coolant jet resulting in secondary combustion. The completion of the reactions can increase the gas temperature locally resulting in higher heat transfer to the airfoil directly along the path line of the film coolant jet. This secondary combustion could damage the turbine blade, resulting in costly repair, reduction in turbine life, or even engine failure. However, knowledge of film cooling in a reactive flow is very limited. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred reactor operating at high temperatures over a flat plate. Surface temperatures, heat flux, and heat transfer coefficients are calculated for a variety of reactor fuel-to-air ratios, cooling hole geometries, and blowing ratios. Emphasis is placed on the difference between a normal cylindrical hole, an inclined cylindrical hole, and a fan-shaped cooling hole. When both air and nitrogen are injected through the cooling holes, the changes in surface temperature can be directly correlated with the presence of the reaction. Photographs of the localized burning are presented to verify the extent and locations of the reaction.

Effects of Embedded Vortices on Injectant From Film Cooling Holes With Large Spanwise Spacing and Compound Angle Orientations in a Turbulent Boundary Layer

1994 ◽  
Vol 116 (4) ◽  
pp. 709-720 ◽  
Author(s):  
P. M. Ligrani ◽  
S. W. Mitchell
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Vortex Core ◽  
Film Cooling ◽  
Test Surface ◽  
Injection Hole ◽  
Plane Projection ◽  
Flow Vectors ◽  
Film Cooling Holes ◽  
Compound Angle

Experimental results are presented that describe the effects of embedded, longitudinal vortices on heat transfer and film injectant downstream of a single row of film cooling holes with compound angle orientations. Holes are spaced 7.8 hole diameters apart in the spanwise direction so that information is obtained on the interactions between the vortices and the injectant from a single hole. The compound angle holes are oriented so that their angles with respect to the test surface are 30 deg in a spanwise/normal plane projection, and 35 deg in a streamwise/normal plane projection. A blowing ratio of 0.5 is employed and the ratio of vortex core diameter to hole diameter is 1.6–1.67 just downstream of the injection holes (x/d=10.2). At the same location, vortex circulation magnitudes range from 0.15 m2/s to 0.18 m2/s. The most important conclusion is that local heat transfer and injectant distributions are strongly affected by the longitudinal embedded vortices, including their directions of rotation and their spanwise positions with respect to film injection holes. To obtain information on the latter, clockwise rotating vortices R0–R4 and counterclockwise rotating vortices L0–L4 are placed at different spanwise locations with respect to the central injection hole located on the spanwise centerline. With vortices R0–R4, the greatest disruption to the film is produced by the vortex whose downwash passes over the central hole (R0). With vortices L0–L4, the greatest disruption is produced by the vortices whose cores pass over the central hole (L1 and L2). To minimize such disruptions, vortex centers must pass at least 1.5 vortex core diameters away from an injection hole on the upwash sides of the vortices and 2.9 vortex core diameters away on the downwash sides of the vortices. Differences resulting from vortex rotation are due to secondary flow vectors, especially beneath vortex cores, which are in different directions with respect to the spanwise velocity components of injectant after it exits the holes. When secondary flow vectors near the wall are in the same direction as the spanwise components of the injectant velocity (vortices R0–R4), the film injectant is more readily swept beneath vortex cores and into vortex upwash regions than for the opposite situation in which near-wall secondary flow vectors are opposite to the spanwise components of the injectant velocity (vortices L0–L4). Consequently, higher Stanton numbers are generally present over larger portions of the test surface with vortices R0–R4 than with vortices L0–L4.

Effects of a Reacting Cross-Stream on Turbine Film Cooling

2009 ◽  
Author(s):  
Wesly S. Anderson ◽  
Marc D. Polanka ◽  
Joseph Zelina ◽  
Dave S. Evans ◽  
Scott D. Stouffer ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Thermal Protection ◽  
Critical Role ◽  
Cylindrical Hole ◽  
Gas Temperature ◽  
Transfer Coefficients ◽  
Secondary Combustion ◽  
Cooling Hole ◽  
Reactor Operating

Film cooling plays a critical role in providing effective thermal protection to components in modern gas turbine engines. A significant effort has been undertaken over the last 40 years to improve the distribution of coolant and to ensure that the airfoil is protected by this coolant from the hot gases in the freestream. This film, under conditions with high fuel air ratios, may actually be detrimental to the underlying metal. The presence of unburned fuel from an upstream combustor may interact with this oxygen rich film coolant jet resulting in secondary combustion. The completion of the reactions can increase the gas temperature locally resulting in higher heat transfer to the airfoil directly along the path line of the film coolant jet. This secondary combustion could damage the turbine blade, resulting in costly repair, reduction in turbine life, or even engine failure. However, knowledge of film cooling in a reactive flow is very limited. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred reactor operating at high temperatures over a flat plate. Surface temperatures, heat flux, and heat transfer coefficients are calculated for a variety of reactor fuel-to-air ratios, cooling hole geometries, and blowing ratios. Emphasis is placed on the difference between a normal cylindrical hole, an inclined cylindrical hole, and a fan shaped cooling hole. When both air and nitrogen are injected through the cooling holes, the changes in surface temperature can be directly correlated to the presence of the reaction. Photographs of the localized burning are presented to verify the extent and locations of the reaction.

Effects of Embedded Vortices on Injectant From Film Cooling Holes With Large Spanwise Spacing and Compound Angle Orientations in a Turbulent Boundary Layer

1993 ◽  
Author(s):  
Phillip M. Ligrani ◽  
Stephen W. Mitchell
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Vortex Core ◽  
Film Cooling ◽  
Test Surface ◽  
Injection Hole ◽  
Plane Projection ◽  
Flow Vectors ◽  
Film Cooling Holes ◽  
Compound Angle

Experimental results are presented which describe the effects of embedded, longitudinal vortices on heat transfer and film injectant downstream of a single row of film cooling holes with compound angle orientations. Holes are spaced 7.8 hole diameters apart in the spanwise direction so that information is obtained on the interactions between the vortices and the injectant from a single hole. The compound angle holes are oriented so that their angles with respect to the test surface are 30 degrees in a spanwise/normal plane projection, and 35 degrees in a streamwise/normal plane projection. A blowing ratio of 0.5 is employed and the ratio of vortex core diameter to hole diameter is 1.6–1.67 just downstream of the injection holes (x/d=10.2). At the same location, vortex circulation magnitudes range from 0.15 m2/s to 0.18 m2/s. The most important conclusion is that local heat transfer and injectant distributions are strongly affected by the longitudinal embedded vortices, including their directions of rotation and their spanwise positions with respect to film injection holes. To obtain information on the latter, clockwise rotating vortices R0-R4 and counter-clockwise rotating vortices L0-L4 are placed at different spanwise locations with respect to the central injection hole located on the spanwise centerline. With vortices R0-R4, the greatest disruption to the film is produced by the vortex whose downwash passes over the central hole (R0). With vortices L0-L4, the greatest disruption is produced by the vortices whose cores pass over the central hole (L1 and L2). To minimize such disruptions, vortex centers must pass at least 1.5 vortex core diameters away from an injection hole on the upwash sides of the vortices and 2.9 vortex core diameters away on the downwash sides of the vortices. Differences resulting from vortex rotation are due to secondary flow vectors, especially beneath vortex cores, which are in different directions with respect to the spanwise velocity components of injectant after it exits the holes. When secondary flow vectors near the wail are in the same direction as the spanwise components of the injectant velocity (vortices R0-R4), the film injectant is more readily swept beneath vortex cores and into vortex upwash regions than for the opposite situation in which near-wall secondary flow vectors are opposite to the spanwise components of the injectant velocity (vortices L0-L4). Consequently, higher Stanton numbers are generally present over larger portions of the test surface with vortices R0-R4 than with vortices L0-L4.

Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System

2009 ◽  
Author(s):  
D. Jackson ◽  
P. Ireland ◽  
B. Cheong
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Cooling System ◽  
Detailed Comparison ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
3 Dimensional ◽  
Turbine Cooling ◽  
Cooling Hole ◽  
The Difference

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.

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