WALL ELEMENTS FOR GAS TURBINE ENGINES
A double-wall structure for use in components in gas turbine engines that are exposed to high temperatures has a first wall spaced apart from a second wall. The first wall has a protrusion extending therefrom towards the second wall. The second wall has a cooling fluid orifice, or hole, through which cooling fluid is directed in use towards the protrusion. The protrusion extends across a significant percentage of the gap between the first and second walls. The cooling fluid removes heat from protrusion as it flows over it through convection, thereby cooling the first wall. The cooling fluid is also redirected so as to become more aligned with the first wall as it flows over the protrusion. In some cases, a trench is provided at the base of the protrusion. The cooling fluid causes a vortex to form in the trench, thereby further assisting cooling.
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This application is based upon and claims the benefit of priority from British Patent Application Number 1114745.1 filed 26 Aug. 2011, the entire contents of which are incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates to cooling in gas turbine engines, and in particular to cooling wall elements for use in wall structures of components, such as combustors and turbines, of gas turbine engines.
Combustors of gas turbine engines can be constructed with a double-wall (also known as a double-skin) structure. Typically, an annular combustor may have radially inner and outer walls, each having a double-wall structure. Other elements of a gas turbine engine that are exposed to high temperature can be similarly constructed with a double-wall structure. Such a double-wall structure has an external wall and an internal wall. In the case of a combustor, the internal wall is usually formed of a plurality of tiles or other similar wall elements. The internal wall has a surface that faces the hot fluid, for example the combustion fluids inside the combustion chamber.
2. Description of the Related Art
Conventional cooling methods involve passing cooling air through holes in the external wall such that it directly impinges on the internal wall. This may be referred to as impingement cooling. Further cooling may be provided through convection by passing the cooling air between the internal and external walls. Still further cooling may be provided by passing the cooling air out through holes in the internal wall to provide a cooling film on the surface of the internal wall that faces the hot fluid.
A significant amount of cooling airflow is used to cool such a double-wall structure using current methods. The airflow that is used for cooling could otherwise be used to provide thrust and thus to improve propulsive efficiency of the engine,
OBJECTS AND SUMMARY OF THE INVENTIONAn object of the present invention is therefore to provide an improved cooling arrangement to reduce the amount of cooling airflow required for a given level of cooling.
According to an aspect of the invention, there is provided a gas turbine engine component comprising a double-wall structure. The double-wall structure comprises: a first wall having a first surface and a second surface; and a second wall spaced apart from the first wall such that the second surface of the first wall faces the second wall, the second wall comprising at least one cooling fluid orifice configured to direct cooling fluid in the direction of the first wall. The double wall structure also comprises a protrusion extending from a base on the second surface of the first wall to a tip. The protrusion is located such that, in use, cooling fluid from a respective cooling fluid orifice is directed towards the tip thereof. The height of the protrusion above the second surface may be at least 25% of the distance between the first wall and the second wall.
In such an arrangement, the first surface (which may be referred to as the outer surface) of the first wall (which may be referred to as the internal wall) may, in use, be exposed to high temperatures, for example the inside of a combustor Providing a protrusion on the second surface (which may be referred to as the inner surface) of the first wall and directing cooling fluid towards and over it may increase the heat transfer away from the first wall. This may increase the efficiency of the cooling flow, and thus decrease the amount of cooling fluid required to obtain a desired amount of cooling.
The protrusion may have a generally tapered shape from the base to the tip. In use, the cooling fluid may be caused to diverge over the protrusion as it passes from the tip to the base. In this way, heat is transferred from the protrusion to the cooling fluid as it passes over the protrusion, and the direction of the cooling fluid can be changed in a controlled manner, for example so as to become more aligned with the surface from which the protrusion extends.
The double-wall structure may comprise a plurality of protrusions, each protrusion corresponding to a respective cooling fluid orifice. In use, substantially all cooling fluid that is directed towards the tip of any given protrusion may be from its corresponding respective cooling fluid orifice. This means that substantially all of the cooling fluid supplied to any given protrusion is from a single cooling fluid orifice. According to this aspect, though, each orifice may supply cooling fluid to more than one protrusion, such that the number of protrusions may be greater than the number of cooling fluid orifices.
The double-wall structure may comprise a plurality of cooling fluid orifices, each cooling fluid orifice corresponding to a single respective protrusion. According to an aspect, substantially all cooling fluid from any given cooling fluid orifice may be directed towards its corresponding single respective protrusion. This means that substantially all of the cooling fluid supplied by any given cooling fluid orifice is supplied to a single protrusion. According to this aspect, each orifice may only supply cooling fluid to one protrusion, although each protrusion may be supplied with cooling fluid by more than one orifice, such that the number of protrusions may be less than the number of cooling fluid orifices.
The double-wall structure may comprise a trough. The trough may extend around at least a part of the perimeter of the base of each protrusion. The trough may be formed in the second surface of the first wall. Such a trough may help to further enhance heat transfer from the first wall to the cooling fluid, for example by causing a “scrubbing” vortex to be formed therein.
Each protrusion may have a major axis that is aligned with a major axis of a corresponding cooling fluid orifice. This can help to ensure that the cooling fluid is delivered from the cooling fluid orifice to the protrusion in the desired way.
Each protrusion may have a major axis that is parallel to and offset from a major axis of a corresponding cooling fluid orifice.
The or each protrusion may be axisymmetric about a major axis that is substantially normal to the second surface of the first wall, from which the protrusion extends.
Cross sections taken through the or each protrusion in any plane perpendicular to the major axis may be circular.
Each protrusion may skewed from base to tip in a direction that is parallel to the principal rotational axis of the gas turbine engine when assembled. The direction in which the protrusion is skewed may be the upstream direction of the fluid flow through the gas turbine engine when in use
In some embodiments, each protrusion may have a major axis that is parallel to the second surface of the first wall. In such embodiments, it may be particularly advantageous to have more than one cooling fluid orifice arranged to supply cooling fluid to a single protrusion, so as to ensure appropriate cooling fluid (in terms of, for example, flow rate and distribution) is directed to each protrusion.
The or each cooling fluid orifice may be a feed hole in the second wall. The cooling fluid may be cooling air, for example taken from a compressor, such as the high pressure compressor, or from a bypass flow or secondary flow. The cooling air may, in operation, flow along or around the surface of the second wall (which may be referred to as the external wall) that faces away from the first wall before passing through the feed hole.
The tip of the or each protrusion may extend at least partially into a respective feed hole in the second wall. This arrangement may help to provide the desired flow pattern over the protrusion(s).
Each protrusion may have a major longitudinal axis, and the spacing between neighbouring longitudinal axes may be at least 50% of the spacing between the first wall and the second wall. This feature may help to ensure that the protrusions are spaced to provide optimum heat transfer away from the first wall, for example as the cooling fluid flows along the surfaces of the protrusions. For example, it may reduce any impact of thermal boundary layers of neighbouring protrusions interacting with each other.
According to an aspect, there is provided a combustor comprising a gas turbine engine component comprising a double-wall structure as described herein. The first surface of the first wall may face the inside of the combustor. The double-wall structure may thus substantially reduce and/or minimize the amount of cooling air required to cool the combustor walls.
According to an aspect, there is provided an aerofoil comprising a gas turbine engine component comprising a double-wall structure according as described herein. In use, the first surface of the first wall may face a working fluid. This may substantially reduce and/or minimize the amount of cooling air required to cool such a component.
According to an aspect, there is provided a nozzle comprising a gas turbine engine component comprising a double-wall structure according as described herein.
According to an aspect, there is provided a method of manufacturing a gas turbine engine component comprising a double-wall structure as described herein, wherein at least the protrusions are manufactured using direct laser deposition. Such a manufacturing technique may, for example, assist in accurate alignment of features as required, for example alignment of the protrusions with the cooling fluid orifices.
According to an aspect, there is provided a method of cooling a double-wall structure, the double-wall structure having a first wall and a second wall, the second wall being spaced apart from the first wall. The method comprises providing a protrusion on a second surface of the first wall, the protrusion extending from a base in the direction of the second wall to a tip. The height of the protrusion above the second surface may be at least 25% of the (local minimum) distance between the first wall and the second wall. The method comprises supplying a cooling fluid flow to the protrusion from a respective cooling fluid orifice, the cooling fluid flow being directed towards the tip of the protrusion.
According to an aspect, there is provided a method of cooling a double-wall structure, the double-wall structure having a first wall and a second wall, the second wall being spaced apart from the first walk. The method comprises supplying a cooling fluid flow to a protrusion from a respective cooling fluid orifice. The protrusion is provided on a second surface of the first wall. The protrusion extends from a base in the direction of the second wall to a tip, the cooling fluid flow being directed towards the tip of the protrusion. The cooling fluid flows over the surface of the protrusion from the tip to the base, thereby removing heat from the protrusion.
In an embodiment, the cooling fluid orifice is a hole in the second wall, and the method comprises supplying cooling fluid flow through the hole.
Embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which;
With reference to
The gas turbine engine 10 works in a conventional manner so that air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate pressure compressor 14 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high pressure compressor 14 where further compression takes place.
The compressed air exhausted from the high-pressure compressor 14 is directed into the combustion equipment 15 where it is mixed with fuel and the mixture corn busted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low-pressure turbines 16, 17, 18 before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines 16, 17, 18 respectively drive the high and intermediate pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.
This ducted gas turbine engine is one of many engines that the double-wall structure can be applied to and is not intended to be limiting. Purely by way of further example, other engines that the double-wall structure could be applied to include turbofan, turbojet, turboshaft, ramjet (and variants thereof) and nozzles thereof.
Referring to
The combustion process, which takes place within the chamber 20, naturally generates a large amount of heat. It is necessary therefore to arrange the inner and outer wall structures 21 and 22 such that they are capable of withstanding the heat.
Referring now to
The circumferentially extending edges 30 and 31 are spaced from the liner 27 to define therebetween a space 38 for the flow of cooling fluid in the form of cooling air. Conventional securing means (not shown) in the form of a plurality of threaded plugs extend from the base portions of the tiles 29A, 29B through apertures in the outer wall 27. Nuts are screwed onto the plugs to secure the tiles 29A, 29B to the external wall 27.
Feed holes 42 are provided in the liner 27 to permit air from the high pressure compressor 14 to pass into the space 38 as illustrated by the arrows 44. Air entering the space will pass forwards and backwards (with respect to the main airflow A through the engine) as illustrated by the arrows 46A and 46B. At the edges 30, 31 of the tiles 29A, 29B the air will pass over the inner surface 41 of an adjacent tile 29B. For forward flowing air 46B, the path is simply over the inner hot surface 41 of an adjacent downstream tile 29B which will be offset outwardly as illustrated in the figure. For backwards flowing cooling air 466, the air will turn 180° to pass in a downstream direction with the air from the adjacent upstream tile 29A, 29B.
This conventional configuration uses a significant amount of cooling airflow that could otherwise be used to improve propulsive efficiency of the engine. The point 48 at which the cooling air 44 entering through the feed holes 42 impinges on the inner surface 41 of the internal wall 28 may be a particular source of loss in the conventional configuration. For example turning the cooling flow through approximately 90 degrees at the point of impingement is relatively uncontrolled in the conventional configuration. This may lead to flow turbulence and/or loss in available cooling potential of the flow at the impingement point 48.
An object of the present invention is therefore to provide more efficient cooling of the internal wall 28. In particular, it is an object of the invention to better utilize the cooling air 44 entering through the feed holes 42.
Referring now to
The external wall 27 and feed hole 42 shown in
As shown in
In operation, cooling air 44 exits the feed hole 42 towards the tip 54 of the protrusion 50. The cooling air 44 may be bled from the HP compressor, for example from the exit of the compressor. Alternatively, the cooling air 44 may be provided by any other suitable source, such as a dedicated cooling feed. The cooling air 44 may be said to impinge on the tip 54 of the protrusion 50.
The protrusion 50 of the embodiment shown in
An additional or alternative improvement in cooling may result from the protrusion 50 acting to redirect the cooling flow 44 in a controlled manner. For example, the protrusion 50 may redirect the flow from a direction 44 that is substantially perpendicular to the internal wall 28 to a direction that is substantially parallel to the internal wall 28 (which may be referred to as a lateral direction) in a controlled (and thus more efficient) manner. This may be a feature of all embodiments, but may be particularly advantageous with regard to the embodiment shown in
The
Returning to the embodiment shown in
The trough 60 may act to further improve heat transfer from the internal wall 28 to the cooling air. As shown in
The cross section of the trough 60 is shown in the embodiment of
To aid the description, the embodiment shown in
Other shapes of protrusion are also in accordance with embodiments. For example other axisymmetric shapes may be used for the protrusion 50. Alternatively, shapes with 2, 3, 4, 5 or more than 5 axes of symmetry may be used. Alternatively still, elongate shapes which have a major axis aligned with the inner surface 41 of the internal wall 28 may be used. Such an elongate shape may have a cross-section in the plane of that of
Other cross-sectional shapes (in the plane shown in
An example of an alternative shape of protrusion 50 is shown in
In this case, the protrusion 50 may be shaped such that, in cross section in a plane perpendicular to the internal wall 28 and parallel to the axial direction (i.e. in the cross section shown in
Any suitable shape could be used for the cross sections taken perpendicular to the (local) surface normal of the inner surface 41 for the skewed protrusion 50 shown in
Skewing the protrusion 50, for example in the manner illustrated in
In an embodiment the protrusion 50 may be offset from the feed hole 42. In the
The protrusion 50 is shown in
Offsetting the protrusion 50 from the feed hole 42 may help to further improve cooling of the internal wall 28. For example, it may help to encourage uniform flow rates around the surface of the protrusion 50, as shown by the arrows 51A, 51B in
Returning to the embodiment of
In some embodiments, the tip 54 of the protrusion 50 may lie below the internal wall 27, such that the distance h is less than the distance w. In other embodiments, the tip 54 of the protrusion 50 may lie above the internal wall 27. According to the invention, the distance h is at least 25% of the distance w. In an embodiment, the distance h is in the range of from 25% to 200% of the distance w. In an embodiment, the distance h is in the range of from 50% to 150% of the distance w. In an embodiment, the distance h is in the range of from 75% to 125% of the distance w. In an embodiment, the distance h is in the range of from 85% to 115% of the distance w. In an embodiment, the distance h is in the range of from 95% to 105% of the distance w, for example around 100%. In an embodiment, the ratio of the distance h to the distance w is chosen to be any value that ensures that the tip 54 lies within the hole 42.
The width a of the base 52 of the protrusion shown in
As can be seen from
The feed holes 42 (which may also be referred to as cooling fluid orifices 42) in the described embodiment are circular. The axis of each of the feed holes 42 is aligned with the axis 200 of the protrusion 50. In other embodiments, the feed holes 42 may not be circular. For example, the feed hole 42 may be elongate (for example rectangular or oval), or square. The shape of the feed holes 42 may correspond to the shape of the protrusions 50 towards the tip 54 Thus, for example, in an embodiment with elongate protrusions 50 that have a major (longitudinal) axis extending parallel to the internal wall 28, the feed holes may have a rectangular or oval shape.
In the embodiments shown in
In alternative embodiments, the number of feed holes 42 may not be equal to the number of protrusions 50. For example, each feed hole 42 may provide cooling air to more than one protrusion 50. In this case, the number of protrusions 50 may be greater than the number of feed holes 42. In other embodiments, each protrusion 50 may receive cooling air from more than one feed hole 42. In this case, the number of protrusions 50 may be less than the number of feed holes 42. By way of non-limitative example, the ratio of the number of feed holes 42 to the number of protrusions 50 may be greater than 10:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or less than 1:10.
In aspects other than those in relation to the protrusion(s) 50 and feed hole(s) 42, the double-wall structure of the present invention may be similar to conventional arrangements, such as that shown in
In operation, these holes 80 enable cooling air to pass from the inner surface 41 of the internal wall 28 to the outer surface 39 that faces the hot gases. The effusion cooling holes may thus operate in a conventional manner, i.e. to create a film of relatively cool air on the outer surface 39 of the internal wall 28. In an embodiment of the present invention, the cooling air that passes through the effusion cooling holes 80 may have passed through the feed hole(s) 42 and over the protrusion(s) 50 before passing through the effusion cooling holes 80.
In embodiments including effusion cooling holes 80, the axis of the effusion cooling holes 80 may be perpendicular to the plane (or the local plane) of the internal wall 28, as shown in
In an embodiment of the invention, the internal wall 28 may be formed of discrete wall elements in the form of tile, in a similar general configuration to the tiles 29A and 29B described above in relation to
In the embodiment described herein in relation to
The present invention has been described herein in relation to a double-wall structure for a combustor in a gas turbine engine. However, it will be appreciated that the described double-wall structure could be applied to any suitable component. For example, the double-wall structure could be applied to any component in a gas turbine engine that requires cooling, for example due to being exposed to a hot working fluid. The described double-wall structure 100 could, for example, be used in a turbine vane, blade, or shroud, or in any aerofoil component that is exposed to high temperature fluid.
It will be appreciated that many alternative configurations and/or arrangements of the double wall structure 100 and components/parts thereof other than those described herein may fall within the scope of the invention. For example, alternative arrangements of protrusion 50 and/or trough 60 may fall within the scope of the invention. Furthermore, any feature described and/or claimed herein may be combined with any other compatible feature described in relation to the same or another embodiment.
Claims
1-17. (canceled)
18. A gas turbine engine component comprising a double-wall structure, the double-wall structure comprising:
- a first wall having a first surface and a second surface;
- a second wall spaced apart from the first wall such that the second surface of the first wall faces the second wall, the second wall comprising at least one cooling fluid orifice configured to direct cooling fluid in the direction of the first wall; and
- a protrusion extending from a base on the second surface of the first wall to a tip, wherein:
- the protrusion is located such that, in use, cooling fluid from a respective cooling fluid orifice is directed towards the tip thereof; and
- the height of the protrusion above the second surface is at least 25% of the distance between the first wall and the second wall.
19. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein the protrusion has a generally tapered shape from the base to the tip such that, in use, the cooling fluid is caused to diverge over the protrusion as it passes from the tip to the base.
20. A gas turbine engine component comprising a double-wall structure according to claim 18, the double-wall structure comprising a plurality of protrusions, each protrusion corresponding to a respective cooling fluid orifice such that, in use, substantially all cooling fluid that is directed towards the tip of any given protrusion is from its corresponding respective cooling fluid orifice.
21. A gas turbine engine component comprising a double-wall structure according to claim 18, the double-wall structure comprising a plurality of cooling fluid orifices, each cooling fluid orifice corresponding to a single respective protrusion such that, in use, substantially all cooling fluid from any given cooling fluid orifice is directed towards its corresponding single respective protrusion.
22. A gas turbine engine component comprising a double-wall structure according to claim 18, further comprising a trough extending around at least a part of the perimeter of the base of each protrusion, the trough being formed in the second surface of the first wall.
23. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein each protrusion has a major axis that is aligned with a major axis of a corresponding cooling fluid orifice.
24. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein each protrusion has a major axis that is parallel to and offset from a major axis of a corresponding cooling fluid orifice.
25. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein the or each protrusion is axisymmetric about a major axis that is substantially normal to the second surface of the first wall, from which the protrusion extends.
26. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein each protrusion is skewed from base to tip in a direction that is parallel to a principal rotational axis of the gas turbine engine when assembled, and in the upstream direction of the fluid flow through the gas turbine engine when in use.
27. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein cross sections taken through the or each protrusion in any plane perpendicular to the major axis are circular.
28. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein each protrusion has a major axis that is parallel to the second surface of the first wall.
29. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein the or each cooling fluid orifice is a feed hole in the second wall.
30. A gas turbine engine component comprising a double-wall structure according to claim 29, wherein the tip of the or each protrusion extends at least partially into a respective feed hole in the second wall.
31. A gas turbine engine component comprising a double-wall structure according to claim 18, wherein each protrusion has a major longitudinal axis, the spacing between neighbouring longitudinal axes being at least 50% of the spacing between the first wall and the second wall.
32. A combustor, an aerofoil, or a nozzle comprising a double-wall structure, the double-wall structure comprising:
- a first wall having a first surface and a second surface;
- a second wall spaced apart from the first wall such that the second surface of the first wall faces the second wall, the second wall comprising at least one cooling fluid orifice configured to direct cooling fluid in the direction of the first wall; and
- a protrusion extending from a base on the second surface of the first wall to a tip, wherein:
- the protrusion is located such that, in use, cooling fluid from a respective cooling fluid orifice is directed towards the tip thereof; and
- the height of the protrusion above the second surface is at least 25% of the distance between the first wall and the second wall.
33. A method of cooling a double-wall structure the double-wall structure having a first wall and a second wall, the second wall being spaced apart from the first wall, the method comprising:
- supplying a cooling fluid flow to a protrusion from a respective cooling fluid orifice, the protrusion being provided on a second surface of the first wall, the protrusion extending from a base in the direction of the second wall to a tip, the cooling fluid flow being directed towards the tip of the protrusion, wherein:
- the cooling fluid flows over the surface of the protrusion from the tip to the base, thereby removing heat from the protrusion.
34. A method according to claim 33 wherein the cooling fluid orifice is a hole in the second wall, and the method comprises supplying cooling fluid flow through the hole.
Type: Application
Filed: Aug 15, 2012
Publication Date: Feb 28, 2013
Applicant: ROLLS-ROYCE PLC (London)
Inventor: Jonathan M. GREGORY (Cheltenham)
Application Number: 13/586,524
International Classification: F23R 3/00 (20060101); F28D 15/00 (20060101);