Patent Application
20200292173
The present invention relates to a heat shield that may be used in a gas turbine engine and in particular a cooling arrangement to improve cooling of the heat shield.
A heat shield is a component which protects another component such as a casing from the hot working gases in a combustor or a turbine of a gas turbine engine for example. The heat shield is exposed to very high temperatures, usually combustion gases, and to help resist the high temperatures the heat shield is provided with a cooling system. The cooling system receives pressurised air or coolant from a compressor and uses the air to impinge on the heat shield to remove heat therefrom and to form film cooling on the surface of the heat shield exposed to the hot working gases.
U.S. Pat. No. 9,145,789B2 discloses an impingement plate that is co-operable with a shroud assembly. The shroud assembly includes an outer shroud and plural inner shrouds with seals between the plural inner shrouds, respectively. The impingement plate includes a trailing edge portion, a leading edge portion and a mid portion between the trailing edge portion and the leading edge portion. A plurality of impingement holes are formed across an area of the impingement plate, and a cooling and damping section includes at least one channel that is shaped to accelerate cooling flow through the impingement plate.
EP2918780 discloses a component comprising a component wall that is arranged to flow a hot gas along the outer side. An impingement cooling wall having a number of grid-like arranged impingement cooling openings is spaced at an inner side opposite to the outer side. Several guide elements for guiding a cooling medium through the impingement cooling openings are arranged on the inner sides. The guide elements include a contour in a form of a curved droplet with a thinner end and a thicker end. Enhanced cooling is achieved. The cooling effect is increased, since the suction side is formed in the guide elements of the acceleration effect of the coolant flow. The unwanted cross-flows are reduced to adjacent impingement cooling openings.
US2014/0271105 discloses a segmented shroud ring that surrounds a circumferential array of blades of a gas turbine engine rotor. The shroud ring has a plurality of shroud segments disposed circumferentially one adjacent to another. The circumferentially adjacent shroud segments have confronting sides defining an inter-segment gap therebetween. The inter-segment gaps are sealed by a sealing band mounted to the radially outer surface of the segmented shroud ring so as to extend across the inter-segment gaps around the full circumference of the shroud ring. Impingement jet holes may be defined in the sealing band for cooling the shroud segments.
US2014/0116059 discloses a hot gas segment arrangement, especially for a combustion chamber of a gas turbine, that includes at least one hot gas segment, which is removably mounted on a carrier, and is subjected at its outside to hot gas and impingement-cooled at its inside. An impingement plate with a plurality of distributed impingement holes is arranged in a distance at the inside of the impingement plate. A cooling air supply means is provided for loading the impingement plate with pressurized cooling air in order to generate, through the impingement holes, jets of cooling air, which impinge on the inside of the hot gas segment. The cooling efficiency and lifetime are increased by the impingement plate being part of a closed receptacle, which is supplied with the pressurized cooling air, and by the receptacle with the impingement plate being mounted on the carrier independently of the hot gas segment.
U.S. Pat. No. 7,704,039B1 discloses a blade outer air seal (BOAS) for use in a gas turbine engine. The BOAS including a plurality of first diffusion and impingement cooling air cavities separated by stiffener ribs, each diffusion and impingement cavity being connected to a cooling air supply cavity through a first metering and impingement hole. Each diffusion and impingement cavity is connected to a plurality of trenched diffusion slots that open onto the surface of the BOAS and form a series of V-shaped slots. A plurality of second metering and impingement holes connect each slot to the respective first diffusion and impingement cavity. The trenched diffusion slots are angularly offset from a normal direction to the BOAS surface, and the second metering and impingement holes are offset at about 90 degrees from the slots so that both diffusion and impingement cooling occurs within the slots. The array of separated diffusion and impingement cavities and metering holes allow for the cooling flows and pressures to be regulated for each area of the BOAS.
U.S. Pat. No. 7,597,533B1 discloses a blade outer air seal (BOAS) used in a gas turbine engine. The BOAS including a metering plate with metering holes and an impingement plate with impingement holes, the metering plate and impingement plate forming a plurality of separate diffusion cavities forming a grid. A porous metallic plate is bonded to the underside of the impingement plate and has a plurality of cooling channels extending from the leading edge to the trailing edge of the BOAS. Cooling air from the blade ring carrier is metered through the metering holes and into the diffusion cavities, and then passes through a plurality of impingement holes and into a cooling channel, to be discharged out the trailing edge side of the BOAS. Inter-segment cooling holes also pass cooling air out to the sides of the BOAS.
US2012/0063891A1 discloses a cooled component for a gas turbine, which by an outer side of a wall delimits hot gas passage of the gas turbine and on an inner side has a device for impingement cooling. The impingement cooling device can include a multiplicity of impingement cooling chambers which are arranged next to each other, operate in parallel, are covered by impingement cooling plates which are equipped with impingement cooling holes, and are impinged upon by cooling air during operation.
It remains an objective to provide improved cooling to gas turbine components which reduces temperature gradients, reduces absolute temperatures and minimises the use of cooling air.
To address the problems of known coating systems there is provided a heat shield for a gas turbine engine. The heat shield comprising a main body having a first surface and a second surface, the first surface being exposed to a hot working gas in use, a plurality of walls upstanding from the second surface, and an impingement plate. The impingement plate is attached to at least one wall of the plurality of walls and forms a chamber with the second surface and plurality of walls and comprises an array of impingement holes. At least one pair of divider walls comprising a first divider wall and a second divider wall formed within the chamber and extending between the impingement plate and the second surface. The first divider wall having a length that extends from a first wall of the plurality of walls towards a second wall, the second wall opposing the first wall, the second divider wall having a length that extends from the second wall towards the first wall. The first divider wall and second divider wall both extend such that they overlap one another viewed in a perpendicular direction to the first divider wall and/or second divider wall and the first divider wall and second divider wall are spaced apart with respect to the perpendicular direction. The overlap is greater than 0% and less than 80% of the chamber in the direction of the length of the first and/or second divider walls.
The first divider wall may be attached to the impingement plate or the second surface and/or the second divider wall is attached to the impingement plate or the second surface.
The first divider wall and the second divider wall may each extend between 10% and 90%, advantageously 15% and 85%, of the chamber in the direction of the length of the first and second divider walls.
The overlap is greater than 40% and less than 80% of the chamber in the direction of the length of the first and/or second divider walls.
The first divider wall and the second divider wall may be parallel to one another.
The first divider wall and the second divider wall may be angled with respect to one another.
The heat shield may comprise two pairs of divider walls.
One of the plurality of walls may be an upstream wall having lateral ends and one of the first divider wall and the second divider wall extend from the upstream wall, wherein the or each pair of divider walls are located within 30% of the length of the upstream wall from one or each of the lateral ends.
The at least one pair of divider walls may divide the chamber into at least a first lateral zone and a central zone, the array of impingement holes has at least a first set of impingement holes opening into the first lateral zone and a second set of impingement holes opening into the central zone, the first set of impingement holes has a different arrangement of impingement holes compared to the second set of impingement holes, the different arrangement of impingement holes provides a different cooling effect.
The plurality of walls has at least one lateral wall and the first lateral zone is located immediately adjacent to the lateral wall and the first lateral zone occupies up to 25% of the second surface within the chamber.
A second pair of divider walls may divide the chamber into a second lateral zone, the array of impingement holes has third set of impingement holes opening into second lateral zone, the third set of impingement holes has a different arrangement of impingement holes compared to at least the second set of impingement holes, the different arrangement of impingement holes provides a different cooling effect.
The different arrangements of impingement holes may comprise any one or more of the group comprising different density of impingement holes and different cross-sectional area of impingement holes.
The heat shield has a centre line, the at least one divider wall of at least one pair of divider walls is angled relative to the centre line, advantageously α is between +25° and −25°, more advantageously α is between +15° and −15° and most advantageously α is between +15° and 0°.
The first and/or second divider walls extend the full distance from the impingement plate to the second surface such that there are no gaps between the first and/or second divider walls and the impingement plate and/or the second surface.
The heat shield may be at least a part of any one or more of a component of a gas turbine engine and advantageously a circumferential segment or a blade outer air seal (BOAS), a shroud of a turbine system, a tile or a heat shield of a wall of the combustor system, a platform or shroud of a blade or vane.
The above mentioned attributes and other features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein
In operation of the gas turbine engine 10, air 24, which is taken in through the air inlet 12 is compressed by the compressor section 14 and delivered to the combustion section or burner section 16. The burner section 16 comprises a burner plenum 26, one or more combustion chambers 28 and at least one burner 30 fixed to each combustion chamber 28. The combustion chambers 28 and the burners 30 are located inside the burner plenum 26. The compressed air passing through the compressor 14 enters a diffuser 32 and is discharged from the diffuser 32 into the burner plenum 26 from where a portion of the air enters the burner 30 and is mixed with a gaseous and/or liquid fuel. The air/fuel mixture is then burned and the combustion gas 34 or working gas from the combustion is channelled through the combustion chamber 28 to the turbine section 18 via a transition duct 17.
This exemplary gas turbine engine 10 has a cannular combustor section arrangement 16, which is constituted by an annular array of combustor cans 19 each having the burner 30 and the combustion chamber 28, the transition duct 17 has a generally circular inlet that interfaces with the combustor chamber 28 and an outlet in the form of an annular segment. An annular array of transition duct outlets form an annulus for channeling the combustion gases to the turbine 18. In other examples, the combustor section 16 may be an annular combustor as known in the art.
The turbine section 18 comprises a number of blade carrying discs 36 attached to the shaft 22. In the present example, two discs 36 each carry an annular array of turbine blades 38. However, the number of blade carrying discs could be different, i.e. only one disc or more than two discs. In addition, guiding vanes 40, which are fixed to a stator 42 of the gas turbine engine 10, are disposed between the stages of annular arrays of turbine blades 38. Between the exit of the combustion chamber 28 and the leading turbine blades 38 inlet guiding vanes 44 are provided and turn the flow of working gas onto the turbine blades 38.
The combustion gas from the combustion chamber 28 enters the turbine section 18 and drives the turbine blades 38 which in turn rotate the shaft 22. The guiding vanes 40, 44 serve to optimise the angle of the combustion or working gas on the turbine blades 38.
The turbine section 18 drives the compressor section 14. The compressor section 14 comprises an axial series of vane stages 46 and rotor blade stages 48. The rotor blade stages 48 comprise a rotor disc supporting an annular array of blades. The compressor section 14 also comprises a casing 50 that surrounds the rotor stages and supports the vane stages 46. The guide vane stages include an annular array of radially extending vanes that are mounted to the casing 50. The vanes are provided to present gas flow at an optimal angle for the blades at a given engine operational point. Some of the guide vane stages have variable vanes, where the angle of the vanes, about their own longitudinal axis, can be adjusted for angle according to air flow characteristics that can occur at different engine operations conditions.
The casing 50 defines a radially outer surface 52 of the passage 56 of the compressor 14. A radially inner surface 54 of the passage 56 is at least partly defined by a rotor drum 53 of the rotor which is partly defined by the annular array of blades 48.
The turbine section 18 further comprises a casing 58 and an annular array of heat shields 60 mounted to the casing 58 and partly defining a working gas path through the turbine section. The heat shields 60 are mounted radially outwardly of the rotor blades 38. In other gas turbine engines, the heat shields 60 may be mounted between annular arrays of rotor blades 38 and/or may be mounted on the radially inner casing 56.
The present invention is described with reference to the above exemplary turbine engine having a single shaft or spool connecting a single, multi-stage compressor and a single, one or more stage turbine. However, it should be appreciated that the present invention is equally applicable to two or three shaft engines and which can be used for industrial, aero or marine applications.
The terms upstream and downstream refer to the flow direction of the airflow and/or working gas flow through the engine unless otherwise stated. The terms forward and rearward refer to the general flow of gas through the engine. The terms axial, radial and circumferential are made with reference to the rotational axis 20 of the engine.
The term ‘heat shield’ is used to denote not only a heat shield as described herein, but also components such as —a circumferential segment or a blade outer air seal (BOAS) or a shroud of a turbine system 18 of the gas turbine engine 10, —a tile or a heat shield of a wall 54 of the combustor system 16 of a gas turbine engine 10, —a platform or shroud of a blade or vane 38, 44 of the gas turbine engine 10. When applied to a blade or vane either or both the radially inner and radially outer platform or shroud may incorporate the present heat shield configuration. The heat shield is described below with reference to a radially outer circumferential segment of a turbine that defines part of the working gas washed surface. Where the heat shield is applied to a radially inner platform or other component the terms radially inner and radially outer may be transposed.
The present heat shield 60 will now be described with reference to
Referring to
The heat shield 60 has a main body 61, a leading edge 62, a trailing edge 64 and to the left and to the right lateral edges 66, 68 respectively. When installed in a gas turbine engine immediately and circumferentially adjacent heat shields 60 may abut or be in close proximity to one another such that one left lateral edge 66 is facing one right lateral edge 68 and a gap may exist therebetween. The heat shield 60 has a first surface or gas washed surface 70, which is also a radially inner surface and that partly defines the radially outer gas washed surface of the gas path in the turbine section 18. The gas washed surface 70 may also be referred to as the hot side, that being subject to the hot working gases flowing through the gas path. The heat shield 60 has a second surface or cold side or surface 72 which is a radially outer surface relative to the hot gas flow.
The heat shield 60 is mounted to the casing 58 by a front hook or hanger 74 and a rear hook or hanger 76. The front hook 74 and the rear hook 76 engage with corresponding features on the casing 50. Other or additional securing means for securing the heat shield to the casing 50 or other supporting structure may be provided as known in the art.
The heat shield 60 has a centre-line 21 which when viewed radially inwardly towards the rotational axis 20 of the gas turbine 10 is parallel to the rotational axis 20. The heat shield 60 is generally symmetrical about its centre-line 21. The heat shield 60 is generally arcuate when viewed in
The heat shield 60 has lateral walls 78, 80 and hook walls 82, 84. The hook walls 82, 84 are part of the front hook 74 and rear hook 76 respectively. The lateral walls 78, 80 and the hook walls 82, 84 are referred to generally as ‘walls’, thus the heat shield 60 has a plurality of walls and which are upstanding from the second surface 72.
The heat shield 60 further comprises an impingement plate 86. The impingement plate 86 comprises an array of impingement holes 90. In this exemplary embodiment, the impingement plate 86 is located on the cold side 72 of the heat shield 60 or radially outwardly of the heat shield 60. The impingement plate 86 is generally situated and sized to cover over most of the second surface 72, bounded by the walls 78, 80, 82, 84 a distance such that impingement jets of cooling fluid impinge on the second surface 72 in an optimal manner. The impingement plate 86 is attached to and advantageously is located on top of at least one wall 78, 80, 82, 84 and which is advantageously one or both of the lateral walls 78 and 80. The impingement plate 86, the walls 78, 80, 74, 76 and the second surface 72 form a chamber 88. The impingement plate 86 is braised or welded on to the walls 78, 80, 82, 84 of the heat shield 60 although other arrangements to attach or methods of attaching are possible. Ideally, the impingement plate 86 is sealed against the walls 78, 80, 82, 84 to prevent egress of the coolant from the chamber and which could adversely affect the pressure of the coolant and therefore where it is desired to flow.
The heat shield 60 further comprises at least one pair of divider walls 92, 94 comprising a first divider wall 92 and a second divider wall 94 formed within the chamber 88 and extending between the impingement plate 86 and the second surface 72. As seen in
Alternatively, the divider walls 92, 94 are integrally formed or manufactured with the impingement plate 86 by casting, additive manufacturing or other technique. Integrally forming at least one of the divider walls 92, 94 with the impingement plate 86 would allow simple and be easy modifications to the configuration of the divider walls to be tested to find the best configuration, in other words impingement plates 86 with different divider wall configurations may be manufactured cheaply yet applied to the same base design of heat shield. Further, where the heat shield is used in gas turbine engines with different power ratings, impingement plates having different divider wall configurations can be easily implemented. In addition to the different divider wall configurations the impingement hole sizes and/or locations and/or densities can be easily adjusted for different applications including engine upgrades where combustion gas temperatures are higher.
The first and/or second divider walls 92, 94 extend the full distance from the impingement plate 86 to the second surface or vice versa such that there are no gaps between the first and/or second divider walls 92, 94 and the impingement plate 86 and/or the second surface 72. Therefore, it is intended that there are no gaps for coolant over the divider walls 92, 94 and instead only around the free ends of the divider walls 92, 94.
The first divider wall 92 is located laterally or circumferentially outside the second divider wall 94, that is to say it is located further away from the centre-line 21 than the second divider wall 94 or nearer the lateral edges 66, 68 than the second divider wall 94. The first divider wall 92 has a length that extends from a first wall 74 of the plurality of walls towards a second wall 76, but does not touch the second wall 76. The second wall 76 opposes the first wall 74 across the chamber 88. The second divider wall 94 has a length that extends from the second wall 76 towards the first wall 74. In this example, the first wall is part of the front hook 74 and the second wall is part of the rear hook 76. It should be noted that the first wall and the second wall are not required to be part of a hook feature, but in this example it is convenient that they are.
The first divider wall 92 and second divider wall 94 both extend such that there is no clear line of sight in a perpendicular direction, indicated by arrow 96, to the first divider wall 92 and/or second divider wall 94. Thus in one extreme example (
The first divider wall 92 and the second divider wall 94 are parallel to one another as shown in
The or each pair of divider walls 92, 94 are located within 30% of the (circumferential) length of the upstream wall 74 from a respective lateral edge or end 66, 68. In other words one pair of divider walls 92, 94 is located within 30% of the (circumferential) length of the upstream wall 74 from the left hand lateral end 66 and the other pair of divider walls 92, 94 is located within 30% of the (circumferential) length of the upstream wall 74 from the right hand lateral end 68.
The first divider wall 92 of at least one pair of divider walls is angled a relative to the centre line 21. In
Referring to
Lateral gaps that extend axially exists between circumferentially adjacent heat shields 60 and a circumferential gap exists between the trailing edge 64 and other immediately downstream adjacent structure. These gaps can allow ingestion of hot working gases which is not desirable and would otherwise lead to thermal degradation of the heat shield 60. Gas pressure in the lateral gaps can often be higher than the gas pressure in the circumferential gap. To prevent ingestion of hot gases into these gaps coolant is supplied to the gaps via the cooling holes 100A, B, C. In addition, the coolant passing through the cooling holes 100A, B, C also cools the material of the heat shield 60. Often there are different requirements for sealing the gaps and cooling of the lateral sides and trailing edge regions. For the examples in
In addition to the cooling holes 100, further cooling of the heat shield 60 is achieved by impingement cooling jets formed by the coolant passing through the impingement plate's 86 impingement holes 90. A coolant supply provides pressurised coolant radially outwardly of the impingement plate 86. Coolant passes through the impingement holes 90 and impinges on the second surface 72 of the main body of the heat shield 60, thereby removing heat from the material of the heat shield 60. The impingement holes 90 are arranged to provide sufficient cooling to parts of the second surface 72 so that a more constant temperature gradient is achieved over the heat shield 60. A more constant temperature gradient reduces thermal stresses and increases the life of the component. In addition, the impingement cooling will reduce the absolute temperature of the component thereby reducing oxidation and therefore thermal degradation.
As described earlier the chamber 88 is divided into three zones, lateral zones 102, 104 and central zone 106. The density of the impingement holes 90A, 90B feeding coolant directly into lateral zones 102, 104 are greater than the density of impingement holes 90C that feed directly into the central zones 106. As mentioned above the impingement holes 90 that feed coolant directly into the lateral chambers 102, 104 may be greater in diameter instead or as well as having a greater density that the impingement holes 90C. The coolant flow, which is directed through the impingement cooling holes 90C into the central zone or chamber 106, may increase the pressure in the lateral zones or chambers 102, 104 by overflowing with coolant the trailing edge holes 100 in the lateral zones or chambers 102, 104. The reduced mass flow of coolant flowing through the impinging holes 90A, 90B which feed directly into the lateral chambers 102,104 decreases the pressure drops along the lateral holes 100A, 100B and will increase the pressure of the coolant. In this way the lateral holes 100A, 100B are suitably pressurised to prevent hot gas ingestion. In particular the coolant flow through the impingement holes 90A, 90B in the lateral chambers 102, 104 is constrained in the lateral chamber 102, 104 and is directed to flow through the lateral holes 100 by increasing the mass flow in the lateral chambers 102,104.
The lateral zones 102, 104 and the central zones 106 are separated by the pairs of divider walls 92, 94. As mentioned previously the divider walls 92, 94 of each pair are spaced apart a distance 97 to allow an amount of coolant to flow from one zone to another, thus there is some distribution of pressure which is advantageous particularly during transient operating conditions to better balance the cooling requirements with the working gas temperatures variations.
Impingement holes 90 may be provided between the divider walls 92, 94 to allow an impingement jet to impingement on the surface 72 between the divider walls 92, 94. The amount of coolant allowed to flow through these impingement holes may be designed further reduce or minimise the temperature gradient across the heat shield 60 and to assist in pressurizing the lateral and or central chambers accordingly.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1720121.1 | Dec 2017 | GB | national |
This application is the US National Stage of International Application No. PCT/EP2018/079954 filed 1 Nov. 2018, and claims the benefit thereof. The International Application claims the benefit of United Kingdom Application No. GB 1720121.1 filed 4 Dec. 2017. All of the applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/079954 | 11/1/2018 | WO | 00 |
