GAS TURBINE ENGINE COMPONENT

Described is a gas turbine engine component (100), comprising a shell having an internal cavity for receiving a multi-part insert; a multi-part insert located within the cavity, wherein the multi-part insert comprises multiple separate parts assembled in an abutting relation with one another within the cavity to provide the multi-part insert; wherein the assembled insert includes at least one retention part, the retention part engaging with a wall of the cavity and at least one other insert part so as to retain the assembled insert within the cavity.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES OF THE INVENTION

With reference toFIG. 2, a ducted fan gas turbine engine incorporating the invention is generally indicated at10and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake11, a propulsive fan12, an intermediate pressure compressor13, a high-pressure compressor14, combustion equipment15, a high-pressure turbine16, and intermediate pressure turbine17, a low-pressure turbine18and a core engine exhaust nozzle19. A nacelle21generally surrounds the engine10and defines the intake11, a bypass duct22and a bypass exhaust nozzle23.

During operation, air entering the intake11is accelerated by the fan12to produce two air flows: a first air flow A into the intermediate pressure compressor13and a second air flow B which passes through the bypass duct22to provide propulsive thrust. The intermediate pressure compressor13compresses the air flow A directed into it before delivering that air to the high pressure compressor14where further compression takes place.

A first example of a component having an insert will be described with reference toFIGS. 3 and 4.FIG. 3shows cross sectional views of (a) a ceramic matrix composite (CMC) shell of a gas turbine engine component in the form of a nozzle guide vane (NGV) as found in the circled region labelled R inFIG. 2, and (b) front and rear inserts to the shell.FIG. 4shows a cross-sectional view of the aerofoil ofFIG. 3with the inserts fitted inside the shell and arrows indicating cooling air flows.

The NGV shell includes a divider wall203which divides the shell into a front cavity201at a leading edge region of the aerofoil and a rear cavity202at a trailing edge region of the aerofoil. A front insert210made by direct laser deposition (DLD) (a form of additive layer manufacturing) is located inside the front cavity210and a rear insert220also made by DLD is located inside the rear cavity202.

The CMC shell includes film cooling holes206located at a region of the suction side of the aerofoil closest to the leading edge. Film cooling holes206are also located along the pressure side of the aerofoil. A cooling flow outlet207is located at the trailing edge of the CMC shell, in fluid communication with the rear cavity, and may take the form of exit holes or slots.

Each of the DLD inserts210,220ofFIGS. 3 and 4has a tubular shape similar to the shape of the front and rear cavities so that the front insert210is located inside the front cavity201in a nested arrangement, and the rear insert220is located inside the rear cavity202in a nested arrangement. Each tubular insert defines a central flow channel211,212, and cooling air is bled out from each central flow channel to the inner surface of the shell via impingement holes216formed in the walls of the insert.

Each DLD insert210,220includes formations218,219which extend outwards from an outer surface of the insert to an inner surface of the shell to support the insert within the shell and guide cooling air around the inner surface of the shell. The formations include pin-fin formations218and chamber-forming formations219.

The rear insert220includes a sealing plate270located along the divider wall203of the shell to help prevent the flow of cooling air across the divider wall203.

The flow of cooling air will now be described with reference toFIG. 4. Large shaded arrows depict the flow of cooling air into the aerofoil, inboard311and outboard312flows entering the front cavity201, and a single inboard flow of cooling air313entering the rear cavity202. Where the flow is a dual feed (an inboard and outboard flow), the insert210preferably includes a baffle plate (not shown). The baffle plate reduces differential pressures caused by the dual feed, thereby reducing unwanted ‘blow through’ effects. The baffle plate can be formed as an integral part of the insert210, which advantageously reduces the part count and cost, and improves reliability.

The chamber-forming formations219form a plurality of chambers229between each insert and the inner surface of the shell200. Each chamber229is configured to receive cooling air from a flow channel211,212via impingement holes216, the pressure of the cooling air being lower in the chambers than in the flow channel. Cooling air from the chambers229is used to supply film cooling holes206. The formations219of the front insert of the aerofoil shown inFIG. 4form four chambers between the insert210and the inner surface of the shell200. A first chamber supplies cooling air to film cooling holes206on the suction side, a second chamber supplies cooling air to showerhead cooling holes206at the leading edge region of the pressure side, and third and fourth chambers supply cooling air to film cooling holes on the pressure side further away from the leading edge.

The number of impingement holes216supplying a given chamber and the number of film cooling holes206fed by that chamber are selected so that each chamber is maintained at a different pressure. Cooling air can therefore be supplied to the film cooling holes206and the film cooling outlet207at pressures which match the local external pressure. The front flow channel211has an internal pressure level which is controlled to ensure adequate blowing rates through these film cooling holes, while maintaining a safe backflow pressure margin to prevent hot gas ingestion throughout the flight cycle.

A second example of a component having an insert will be described with reference toFIGS. 5,6and7.FIG. 5shows a nozzle guide vane300according to the second example,FIG. 6shows the cross-sectional view ofFIG. 5with arrows indicating cooling air flows, andFIG. 7shows a cross-sectional view of variant inserts for the nozzle guide vane ofFIGS. 5 and 6. The NGV has a CMC shell400, including a divider wall403which divides the shell into a front cavity at a leading edge region of the aerofoil and a rear cavity at a trailing edge region of the aerofoil. A front insert410made by DLD is located inside the front cavity and a rear insert420, also made by DLD, is located inside the rear cavity. Each insert410,420includes a sealing plate470to prevent the flow of cooling air across the divider wall403.

The front insert410of the aerofoil shown inFIGS. 5 and 6has formations, including a plate end419and pin-fins418, which extend from an insert plate440to the inner surface of the shell to support the insert within the front cavity of the shell, and thereby define a flow channel411at the pressure side of the front cavity between the front insert and the inner surface of the shell, and a chamber at the suction side of the front cavity between the front insert and the inner surface of the shell. The chamber on the suction side receives cooling air from the flow channel411via impingement holes416.

The rear insert420of the aerofoil shown inFIGS. 5 and 6has formations in the form of sealing walls475which extend outwardly from a central insert plate430, to the inner surface of the shell. There are four sealing walls475which, in addition to the sealing plate470, define a plurality of flow channels441,442,443in fluid communication with one another to form a multi-pass cooling arrangement.

InFIG. 6, large straight arrows512,513and514depict flows of cooling air into the aerofoil400. The multi-pass cooling arrangement includes, in flow series, a pair of parallel first pass chambers441(one on the pressure side and one on the suction side) corresponding to a first pass flow channel, a pair of parallel second pass chambers442(one on the pressure side and one on the suction side) corresponding to a second pass flow channel and a common third pass chamber443corresponding to a third pass flow channel. The third chamber is located at a trailing edge region of the rear cavity and feeds trailing edge discharge holes or slots407. The first pass chamber441on the pressure side supplies film cooling holes406on the pressure side of the NGV. Similarly, the second pass chamber442on the pressure side supplies film cooling holes406on the pressure side of the NGV.

Integral plates at end walls (not shown) create suitable bend geometries to guide cooling air from the first pass chambers441to the second pass chambers442and from the second pass chambers to the third chamber443in order that the chambers operate as the rearward flowing,3-pass cooling arrangement shown by the curved arrows.

FIG. 7shows variant front and rear inserts similar to those ofFIGS. 5 and 6but having additional trip strip formations460which lie along the inner surface of the shell. The trip strip formations are ladder-like in construction having a pair elongate parallel rails which provide support for a linear array of equally spaced trip strips or bars which run therebetween. The trip strips are set at a compound angle to the rails, Trip strips are known in the art and can locally enhance heat transfer to the cooling air.

Although not shown in the above Figures, formations defining a contra-flow cooling system can be incorporated into an insert, as an alternative or an addition to the cooling structures described above.

Any holes216,416in the insert can be formed during the DLD process so there is no need for subsequent machining of the inserts.

In addition, the DLD process facilitates modification and development of the insert design during the manufacturing process as no tooling changes are required. For example, features such as formations218,219,418,419,460,475may be altered slightly between the manufacture of different aerofoils100,400of a single engine10depending on the position of the respective aerofoils within the engine to give a relative increase or decrease in the cooling mass flow of the aerofoil.

FIG. 8shows cross-sectional views of (a) a ceramic matrix composite (CMC) shell800of a gas turbine engine component100in the form of a nozzle guide vane (NGV) found in the circled region labelled R inFIG. 2, and (b) front210and rear820inserts to the shell.

FIG. 9shows a cross-sectional view of the aerofoil ofFIG. 8with the inserts fitted inside the shell and arrows indicating cooling air flows.

The shell800includes a divider wall803which divides the shell into a front cavity801at a leading edge region of the aerofoil and a rear cavity802at a trailing edge region of the aerofoil. The front insert810is located inside the front cavity801and the rear insert820is located inside the rear cavity802.

The CMC shell800includes exterior film cooling holes806located at the region of the suction side of the aerofoil closest to the leading edge. More exterior film cooling holes806are located along the pressure side of the aerofoil. The CMC shell800also includes exit holes or slots807at its trailing edge.

Each of the front and rear inserts includes a first wall811,821having first impingement holes813,823formed therein and a second wall812,822having second impingement holes814,824formed therein. For each insert, a fluid pathway815,825is formed between the first wall811,821and the second wall812,822.

The first impingement holes813,823lie opposite a first region833,843of the inner surface of the shell and the second impingement holes814,824lie opposite a second region834,844of the inner surface of the shell. The first and second regions of the aerofoil ofFIGS. 3 and 4are both located at the suction side of the aerofoil. For each insert, the fluid pathway is formed between the first region833,843and the inlets of the second impingement holes814,824to recycle cooling air which has been jetted onto the first region for jetting onto the second region.

The fluid pathway815of the front insert guides recycled cooling air in an upstream direction towards the leading edge so that, for the front cavity, the first region833is located further away from the leading edge of the aerofoil and the second region834is located closer to the leading edge of the aerofoil. The fluid pathway825of the rear insert guides recycled cooling air in a downstream direction so that, for the rear cavity, the first region843is located furthest away from the trailing edge of the aerofoil and the second region844is located closest to the trailing edge807of the aerofoil.

Heat transfer formations853are located at the first region833,843and the second region834,844. The heat transfer formations shown inFIGS. 3(b) and4are pin-fins.

In addition to the first wall821and second wall822, the rear insert820shown inFIGS. 3(b) and4includes a bank of pin-fins863which extend along the inside surface of the shell from the second region to the trailing edge. The rear insert also defines a plurality of chambers881,882at the pressure side of the rear cavity. The chambers are interconnected via internal passageways829so that they are in fluid communication with each other. Two chambers881,882are shown in the rear insert of the aerofoil ofFIGS. 3(b) and4.

Each insert810,820includes a sealing plate870which lies along the divider wall803of the CMC shell800to prevent a flow of cold air across the divider wall. The rear insert820also includes trip strip formations816which lie along the inner surface of the shell at the pressure side of the cavity to improve heat transfer to the cooling air at this location.

The flow of cooling air will now be described with reference toFIG. 9. Large shaded arrows depict the flow of cooling air into the aerofoil: inboard911and outboard912flows entering the front cavity801, and a single inboard flow of cooling air913entering the rear cavity802. Where the flow is a dual feed (an inboard and an outboard flow), the insert preferably includes a baffle plate (not shown). The baffle plate reduces differential pressures caused by the dual feed, therefore reducing unwanted ‘blow through’ effects. The baffle plate can be formed as an integral part of the insert which advantageously reduces the part count and cost and improves reliability.

In the front cavity801, the first wall811defines a front flow channel860at the pressure side of the cavity. Cooling air is distributed from this front flow channel to the inlets of the first impingement holes813for jetting onto the first region833. The front flow channel also supplies cooling air at a high pressure to film cooling holes806on the pressure side in the form of a leading edge showerhead cooling head arrangement. The front flow channel has an internal pressure level which is controlled to ensure adequate blowing rates through these cooling holes, while maintaining a safe backflow pressure margin to prevent hot gas ingestion throughout the flight cycle. Cooling air which has been recycled and jetted onto the second region834will have a reduced pressure compared to the cooling air supplied directly by the front flow channel and can therefore be used to feed exterior film cooling holes806on the suction side.

In the rear cavity802, the plurality of chambers881,882on the pressure side form a plurality of rear flow channels. Cooling air enters the first chamber881and is distributed therefrom to the inlets of the first impingement holes823for jetting onto the first region843. This first chamber also supplies cooling at a high pressure to exterior film cooling holes806on the pressure side of the aerofoil, as well as supplying cooling air to the second chamber882via internal passageways829. The second chamber supplies cooling air to the bed of pin-fins863as well as to further exterior film cooling holes806on the pressure side. Both chambers have internal pressure levels which are controlled to ensure adequate blowing rates through their cooling holes, while maintaining a safe backflow pressure margin to prevent hot gas ingestion throughout the flight cycle.

The CMC shell may be SiC—SiC and a protective coating may be applied to the outside and/or inside surfaces of the shell800to prevent environmental attack. The inserts810,820may be cast (e.g. using the lost wax process) and then machined (e.g. for hole drilling), or may be made using additive layer manufacturing such as direct laser deposition (also known as direct metal deposition). Additive layer manufacturing, and particularly direct laser deposition, enables all of the detailed features of the inserts to be manufactured in one procedure, including the impingement holes813,814,823,824. Further, it allows cooling schemes to be easily changed, without the need for re-tooling.

The gas turbine component of the present invention can be an NGV aerofoil, as described in detail in above, but can be any other gas turbine aerofoil, including a rotor blade. The gas turbine component may alternatively be an NGV platform, a shroud segment, or a shroud liner.

The inserts described above can be used instead of, or in combination with, sheet metal inserts.

Instead of forming each insert as a unitary body, as shown inFIGS. 3 to 9, another option is to form the inserts from two or more insert parts. This allows the inserts to be fitted into cavities where a receiving portion in which part of the insert would ideally be located is obstructed in some way such that a complete insert cannot be directly inserted. The obstruction in question may be provided by a wall of the cavity or by a protuberant feature which extends from one or between two walls of the cavity. An obstructed portion may be as viewed from outside the shell through an insertion aperture, or by a part of the insert having to enter the cavity along a first trajectory before being located in a receiving portion along a second trajectory which is different to the first trajectory. For example, an elongate insert part having a longitudinal axis may be inserted into the cavity with an axially extending trajectory, before being pushed laterally into a recess or an otherwise obscured portion of the cavity.

FIGS. 10a, and10bshow a perspective view of an aerofoil having a front insert1010which is a variant of the front insert ofFIGS. 5 and 6, and a rear insert1020which is a variant of the rear insert ofFIG. 7, the CMC shell1000being drawn as a transparent body.

Thus, inFIGS. 10aand10bthere is shown an aerofoil in the form of a vane similar to the NGV shown inFIG. 1. The aerofoil includes an elongate shell1000having internal front1001and rear1003cavities. The outer surface of the shell has a predetermined aerodynamic shape suitable for use as an NGV. As such, the aerofoil is distorted from a straight radially extending form and includes a chordal twist along its length. This distortion can be best seen inFIG. 10bwhere the first end1000aand second end1000bof the aerofoil are angularly offset from each other when viewed approximately along the longitudinal axis of the aerofoil1000. This means that the front1001and rear cavities which extends along the radial axis of the interior of the aerofoil1000have an irregular shape with obstructed portions when viewed from the first end along the longitudinal axis of the shell1000.

It will be appreciated that the distortion of the cavities is also affected by the internal profile of the shell walls which may be varied but will typically be determined by the weight and mechanical and thermal requirements of the aerofoil rather than the fit of an insert. In the described example, the walls of the shell have substantially uniform thickness.

The front cavity1001has a multi-part insert1010located therein, which, in the described example, is made up from two separate insert parts1010a,bassembled in an abutting relation to one another so as to provide the multi-part insert1010. The rear cavity1003also includes a multi-part insert1020having multiple separate insert parts1020a-f.The rear cavity insert1020is made up from two main body parts1020a,band several trip-strip insert parts1020c-fwhich abut and engage the main body portions1020bof the rear insert1020, and also the wall of the shell1000. Thus, the front insert1010is a multi-part insert formed from two insert parts1010a,band the rear insert1020is formed from six insert parts1020a-f.In each cavity, the last insert part to be installed locks the completed insert in place and ensures a tight fit between the insert and the shell1000while accommodating manufacturing tolerances.

To construct the vane with the assembled inserts1010,1020, the insert parts1010a,b,1020a-f,are placed within the respective cavities via an insertion aperture1050. The insertion aperture1050may be any suitable entrance to the cavity and may be covered and optionally sealed after the inserts1010,1020have been correctly located within the shell1000. In the described example, the insertion aperture1050is provided by the open end of the aerofoil and is as large as can be accommodated by the walls of the shell1000. It will be appreciated that some constructions of the component, particularly one which is cast for example, may only include a partial opening in the end of the aerofoil. Further, the insertion aperture may be defined by the walls of the shell, or a particular portion or zone of a larger opening.

Although the insertion aperture1050of the rear cavity1020is as large as can be accommodated, the irregular shape of the rear cavity1020means that the insertion of the assembled or unitary insert1010,1020into the cavity1020would not be possible. This is because an insert which is shaped to match and abut the internal walls of the cavity may be too large in parts to fit through the insertion aperture1050. Alternatively, the curvature or twist of the insert may prevent it from being inserted along the length of the cavity. Further, there may be features or recesses within the cavity which the insert must either go around or be placed within when being inserted. Thus, although the use of prior art inserts has provided some benefits, applications have been limited due to the restrictions placed on the inserts.

Providing a multi-part insert allows a first insert part to be loaded into the cavity via an insertion aperture and subsequently located into a receiving portion of the cavity. Thereafter, the second insert part, or retaining part, is passed into the cavity and engaged with the first insert part in an abutting manner. The retaining part may provide a biasing force which acts to urge the first insert part against a wall of the cavity so as to retain it there, or may be manufactured to have an interference fit with the first insert part so as to provide chock. Thus, there is provided an assembled insert within the cavity which cannot be withdrawn from the insertion aperture (or inserted if assembled outside of the shell), but which can be located against the wall of the shell.

In some embodiments, the resilient part may be the first or an intermediate part loaded into the cavity. In this instance, the loading of the resilient part will occur upon insertion of the last part which will act to put the resilient part in a stressed condition.

In the described example ofFIGS. 10aand10b, a receiving portion1060can be taken to the rearmost portion of the rear cavity1003in which the first insert part1010ais located. The insertion aperture1050can be taken to be at the first end1000bof the aerofoil toward the divider wall1004. Thus, the first insert part1020ais inserted into the rear cavity1003through the insertion aperture1050which is located at the wider end of the open ended aerofoil towards the divider wall1004and with a trajectory which is coincidental with the plane of the divider wall1004. Once in place, the first insert part1020acan be moved toward the rear of the cavity until the distal ends of partitioning walls1021abut the walls of the cavity. It will be appreciated that the trip strip formations1020cand1020dcan be mated to the first insert part before or after the insertion depending on the particular design, but it is envisaged that they are mated to the first main body insert part1020aprior to being loaded into the rear cavity1003. Next, the second main body insert part1020band third trip strip1020ecan be placed within the rear cavity1003via the insertion aperture1050and pushed home to provide a chock for retaining the first insert part1020ain place. The final insert part is the fourth trip strip1020fformation which is slid between a free end of a web of the first main insert part1020a,and a shoulder1005which protrudes into the rear cavity along the length of the divider wall1004where the divider wall meets the shell wall.

It will be noted fromFIG. 10b, that the shape of the rear cavity1003would prevent the insertion of the assembled insert1020into the cavity from the open end of the vane due to the variance in amount of the chordal twist required between the front and rear parts of the assembled insert.

The two insert parts1010a,bof the front cavity1001include a curved member1010awhich sealably contacts the interior of the leading edge of the aerofoil and extends around the suction side toward the divider wall1004. The second insert part1010bis in the form of a sealing plate1014which sealably abuts the divider wall1004. The sealing plate1014includes a short wall along its length which includes a rebate for receiving the corresponding free end of the first insert part1010a.

The first insert part1010ais made to be slightly flatter than required when in situ such that the free end is closer to the divider wall1004and inserting the second insert part1010burges the first part1010atowards the leading edge so as to provide the biasing force for retaining the assembled insert1010in place.

In order to provide a correct fit, the insert parts1010a,bare arranged to be held in an abutting relation with a resilient bias provided by one of the insert parts. The resilient bias in the case of the front cavity is provided by the fore insert part1010awhich is inserted after the sealing plate which is described above. The fore insert part may be oversized slightly with respect to the space in which it is designed to accommodate such that it must elastically deform during insertion.

The elastic deformation is such that the part is sufficiently stressed so as to provide the resilient bias between a wall of the cavity and sealing plate. Alternatively, the insert part may be made so as to be partly collapsible or compressible so that the shape of the part is altered to allow it to be inserted. In order to provide the collapsibility and compressibility, the insert part may be made to size for the cavity before being plastically deformed prior to insertion of the part.

The insert parts can incorporate rebates or other features to allow them to be secured in an abutting relation and to provide opposing surfaces for the retention of the parts via the resilient bias. Hence, as seen inFIG. 10b, the sealing plate insert part1010bin the front cavity1001and the free ends of the first and second main body parts in the rear cavity1003include rebates for receiving corresponding parts of abutting insert parts. Further, the rails of trip-strip insert parts1020c-finclude protuberant lips which engage with corresponding rebates in the main body portions.

It will be noted that the shell is constructed from a CMC material and as such has smooth outer and inner walls, principally due to the difficulties of forming discrete features in a CMC material. However, this may not always be the case, and the inserts are applicable to other non-CMC constructed shells.

FIGS. 11aand11bprovide another example in which the rear insert1120comprises three insert parts1120a-c.The first insert part1120bis V-shaped part having two plate-like members1121aand1121bwhich are joined at a hinged portion1121c.The free ends of the members1121a,b(or arms) are tapered from the first end to the second end so as to provide a smaller sectional area at the first end so that it can be manoeuvred more readily into the insertion aperture1150, and to provide a generally wedge shaped insert part. The second1120band third1120cinsert parts join along a mid-line of the sealing plate and form a wedge shaped part in unison which provides a chock for the first part1120awhen the insert parts1120are assembled into a complete insert. It will be appreciated that the second and third parts are inserted from the opposite end of the cavity through a second insertion aperture1152.

The V-shaped first insert part1120ais fabricated such that the angle between the arms is greater than angle between the corresponding portions of the rear cavity. Thus, to insert the part, the arms are forceably moved together so as to elastically stress the hinge portion as it is passed through the insertion aperture. Once inside the cavity, the insert part can be pushed into the receiving portion1160with the resilient bias of the arms retaining the part in place.

The front cavity multi-part insert1010includes three parts1010a-c.Here, the first insert part1010aextends from the divider wall1004toward the leading edge against the pressure surface of the front cavity1001. The second part1010babuts the free end of the first insert part1010awhich is local to the leading edge and extends around the suction surface toward the suction surface. The third insert1010cis generally L shaped with rebates provided on the free ends of long and short members. The rebates provide a flange which resides on the inside of the free ends of the corresponding ends of the first and second insert parts. The arms are joined at a hinge portion.

The first1010aand second1010binsert parts are made to fit in a neutral or stress-free state within the front cavity1001whilst abutting the walls of the shell1000. The third L-shaped insert part is fabricated to have a larger angle than required such that the hinge portion elastically deformed upon insertion so as to provide a restoring force to bias against the free ends of the first and second insert parts against the wall of the cavity via the rebated portions.

A further example is shown inFIGS. 12aand12bwhich corresponds to the component described inFIGS. 8 and 9above, but with multiple insert parts in the front1201and rear cavities1203. Hence, the front1210and rear1220inserts each include two insert parts1210a,b,1220a,b,having similar features to those described above in relation toFIGS. 10ato11b. In this instance, the front cavity1201has a first insert part1210awhich is inserted first and provides the resilient bias once the sealing part is inserted. The rear cavity1203has a first insert part1220awhich is inserted into the rear cavity via the insertion aperture1250along a first trajectory before being pushed rearward into the trailing edge which it is located in its corresponding receiving portion1260. The second insert1220bprovides the sealing plate and a portion of wall which defines a cooling chamber with the cavity wall. The wall is connected to the sealing plate via a hinge portion which provides the resilient bias for retaining the first insert part in place.

In addition to the above, it is possible in some embodiments that multiple insert parts can be fitted inside one another so that a single shell cavity includes an insert formed from two or more nested insert parts. Each insert shown inFIGS. 3 and 4seals its cavity, as well as providing formations to support the insert and guide cooling air around the inner surface of the shell. If two nested insert parts are used in a cavity, the outer of the two insert parts can provide the formations, and the inner of the two insert parts can be configured to balloon under the pressure of the inboard and/or outboard flows of cooling air to provide a sealing load.