Patent Description:
Gas turbine engines (used in propulsion and power applications and broadly inclusive of turbojets, turboprops, turbofans, turboshafts, industrial gas turbines, and the like) include a variety of heat exchangers. Examples of gas turbine engine heat exchangers are found in: <CIT>, "HIGH TEMPERATURE PLATE FIN HEAT EXCHANGER"; <CIT>, "HEAT EXCHANGER BELL MOUTH INLET"; and <CIT>, "METHOD FOR MANUFACTURING A CURVED HEAT EXCHANGER USING WEDGE SHAPED SEGMENTS".

An exemplary positioning of such a heat exchanger provides for the transfer of thermal energy from a flow (heat donor flow) diverted from an engine core flow to a bypass flow (heat recipient flow). For example, air is often diverted from the compressor for purposes such as cooling the turbine or aircraft systems. However, the act of compression heats the air and reduces its cooling effectiveness. Accordingly, the diverted air may be cooled in the heat exchanger to render it more suitable for cooling or other purposes. One particular example draws the heat donor airflow from a diffuser case downstream of the last compressor stage upstream of the combustor. This donor flow transfers heat to a recipient flow which is a portion of the bypass flow. To this end, the heat exchanger may be positioned within a fan duct or other bypass duct. The cooled donor flow is then returned to the engine core (e.g., radially inward through struts) to pass radially inward of the gas path and then be passed rearward for turbine section cooling including the cooling of turbine blades and vanes. The heat exchanger may conform to the bypass duct. The bypass duct is generally annular. Thus, the heat exchanger may occupy a sector of the annulus up to the full annulus.

Other heat exchangers may carry different fluids and be in different locations. For example, instead of rejecting heat to an air flow in a bypass duct, other heat exchangers may absorb heat from a core flow (e.g., as in recuperator use).

<CIT>, "Curved plate/fin heater exchanger", shows attachment of a square wave form fin array to the side of a heat exchanger plate body. For radially-extending plates in a radial array, the wave amplitude progressively increases to accommodate a similar increase in inter-plate spacing.

<CIT> discloses a guide vane for a turbomachine fan.

<CIT> discloses single phase micro/mini channel heat exchangers for gas turbine intercooling.

<CIT> discloses a heat exchanger plate according to the preamble of claim <NUM>.

According to an aspect of the present invention, there is provided a heat exchanger plate in accordance with claim <NUM>.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include: the inlet plenum being adjacent the trailing edge; and the outlet plenum being adjacent the leading edge.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include: the inlet plenum tapering away from the proximal edge; and the outlet plenum tapering away from the proximal edge.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include: the plurality of legs being separated by dividing walls extending between a first interior face and a second interior face.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include: the first interior face and the second interior face having integral surface enhancements.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the integral surface enhancements being chevron arrays.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the integral surface enhancements being non-uniform between adjacent legs.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the dividing walls having turns at the inlet plenum.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the dividing wall turns being non-uniform between adjacent legs.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the dividing wall turns progressively decreasing in length away from the proximal edge.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the dividing walls lacking turns at the outlet plenum.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include cross-sectional area being non-uniform between adjacent legs.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include a straight portion length of the dividing walls being non-uniform between adjacent legs.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the first face and second face including heat transfer augmentation features.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include at least one of the first face and second face including fins.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the fins being formed by a metallic sheet corrugation secured to a substrate of the heat exchanger.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the heat exchanger plate comprising a cast substrate.

<FIG> shows a gas turbine engine heat exchanger <NUM> providing heat exchange between a first flowpath <NUM> and a second flowpath <NUM> and thus between their respective first and second fluid flows <NUM> and <NUM>. In the exemplary embodiment, the flowpaths <NUM>, <NUM> are gas flowpaths passing respective gas flows <NUM>, <NUM>. In the illustrated example, the first flow <NUM> enters and exits the heat exchanger <NUM> as a single piped flow and exits as a branched flow 910A/910B along branches 900A/900B; whereas the flow <NUM> is sector portion of an axial annular flow surrounding a central longitudinal axis <NUM> of the heat exchanger and associated engine. The exemplary view has components such as mounting hardware, deflectors/blockers, and structural brace hardware removed for purposes of illustration.

The heat exchanger <NUM> has an inlet <NUM> and outlet 24A, 24B for the first flow. The exemplary inlet and outlet are, respectively, ports of an inlet manifold and an outlet manifold (discussed below). Exemplary manifolds are metallic (e.g., nickel-based superalloy). The inlet manifold and outlet manifold may each have a respective fitting <NUM>, 32A, 32B providing the associated port <NUM>, 24A, 24B. As is discussed further below, the inlet manifold and outlet manifold are coupled to heat exchanger plates of two exemplary plate (panel) arrays (banks) 40A, 40B. In the exemplary configuration, the single first flow inlet <NUM> is centrally between the banks open radially outward to receive an inward radial flow. Similarly, the two exemplary first flow outlets 24A, 24B are at circumferential outboard ends of the associated plate banks and are also open radially outward to discharge radially outward.

Each plate bank 40A, 40B comprises a circumferential array of plates (discussed further below). In the exemplary banks, the plates are parallel to each other. However, alternative banks may have the plates extending more exactly radially so as to diverge from each other in the outward radial direction.

In the exemplary embodiment, inner diameter (ID) edges of the plates mate to the manifolds and outer diameter (OD) edges of the plates of the banks are captured by respective shrouds <NUM>. The shrouds <NUM> each have a first circumferential end (end wall) <NUM> and a second circumferential end (end wall) <NUM> abutting terminal plates of the associated bank. The ends are joined by an outer diameter (OD) circumferential wall <NUM>. As discussed further below, the OD wall <NUM> has slots receiving associated projections of the plates to retain and register the plates. The shrouds thus bound duct sectors passing respective branches 902A, 902B of the second flow 912A, 912B along respective branches of the second flowpath <NUM>.

<FIG> shows the heat exchanger with shrouds further removed for purposes of illustration.

Each plate <NUM> comprises a body or substrate <NUM> (e.g., cast or additively manufactured alloy such as nickel-based superalloy) having a leading edge <NUM>, a trailing edge <NUM>, an inboard or inner diameter (ID) edge <NUM>, an outboard or outer diameter (OD) edge <NUM>, a first circumferential (generally circumferentially facing) face <NUM> and a second circumferential face <NUM>. The OD edge <NUM> may bear one or more (two shown) projections <NUM> which become captured by associated slots <NUM> (<FIG>) in the shroud OD wall <NUM> as noted above.

As is discussed below, one or both faces <NUM>, <NUM> may bear fin arrays <NUM>. Although fin arrays formed unitarily with the body or substrate are possible, the exemplary fins are separately formed (e.g., of folded sheetmetal - e.g., nickel-based superalloy) and secured to adjacent substrate(s) (generally see the '<NUM> patent). As is discussed further below, exemplary fins are square wave corrugations of even height/amplitude so that the plates are parallel with each inter-plate gap in each bank being spanned by a respective one fin array whose peaks are secured to one adjacent substrate and troughs to the other (discussed further below).

<FIG> shows further details of a single manifold unit <NUM> that forms both an inlet manifold <NUM> and an outlet manifold <NUM> of the heat exchanger. As is discussed further below, the outlet manifold <NUM> is fully split between sections respectively associated with the two banks 40A, 40B.

The manifold unit <NUM> comprises a main body <NUM> having a leading end <NUM>, a trailing end <NUM>, a first circumferential end <NUM>, a second circumferential end <NUM>, an inner diameter (ID) surface <NUM>, and an outer diameter (OD) surface <NUM>. The OD surface <NUM> has a plurality of mating features for receiving the associated plates (e.g., the ID edges <NUM> of the plate substrates). Exemplary features <NUM> are formed as full or partial sockets extending axially and having respective ports <NUM> and <NUM> for communicating with the plate interior (discussed further below). The exemplary features <NUM> have flat base surfaces that mate with the respective associated plate ID edge <NUM>. In the exemplary embodiment, the features <NUM> are progressively stepped along the manifold OD surface (e.g., flats stepped to form partial sockets open at one side) to allow the bank to better conform to and fill the duct segment while maintaining plate parallelism. In this example, stepping causes the shroud OD circumferential wall <NUM> to be convex outward to conform to the outer diameter boundary of the duct.

<FIG> further shows an integrally formed radial conduit <NUM> extending to the first flow inlet fitting <NUM> and respective integral conduits 108A, 108B extending to the respective first flow outlet fittings 32A, 32B. The exemplary conduit <NUM> protrudes radially from the main body OD surface <NUM>. The conduits 108A, 108B protrude circumferentially from the associated main body ends <NUM> and <NUM>, then turning radially outward at a bend.

<FIG> is a circumferential sectional view viewed radially outward. <FIG> shows the inlet manifold <NUM> as including a plenum <NUM> extending from the inlet port <NUM> to the ports <NUM>. The outlet manifold <NUM> comprises a pair of independent plenums 112A and 112B extending from the ports <NUM> of the associated array to the outlets 24A, 24B. <FIG> shows a dividing wall <NUM> extending partially outward into the conduit <NUM> to divide downstream sections of the plenum <NUM>. A dead space or buffer cavity <NUM> divides the inlet manifold from the outlet manifold and divides the two plenums of the outlet manifold to effectively form two outlet manifolds in a single piece or assembly.

An exemplary manifold unit <NUM> may be formed of a nickel-based superalloy such as via casting, additive manufacture, and/or machining. Particularly if additively manufactured, assembly of multiple pieces may be required (e.g., via brazing, welding, or diffusion bonding).

<FIG> is a sectional view through a panel in the heat exchanger taken along line <NUM>-<NUM> of <FIG>. Each plate has an interior providing an associated flowpath branch/leg from an inlet <NUM> of the plate to an outlet <NUM>. The exemplary inlets and outlets are along the ID edge <NUM> (e.g., on plugs protruding from a flat main portion of the ID edge and received in the respective ports <NUM> and <NUM>). The inlet <NUM> feeds an inlet plenum <NUM> adjacent/along the trailing edge while the outlet <NUM> is fed by a plenum <NUM> along the leading edge.

A generally radial array of flowpath legs (sublegs) <NUM> extend between the inlet plenum <NUM> and outlet plenum <NUM>. The adjacent flowpath legs <NUM> are separated from each other by wall structures <NUM>. Each wall structure <NUM> extends from a leading end <NUM> to a trailing end <NUM> (along the first flowpath). The exemplary wall structures may have gaps <NUM>. The gaps may provide pressure equalization and/or may be artifacts of a casting process wherein core legs forming the passageway legs <NUM> are held in alignment with each other by webs that in turn cast the gaps. The exemplary wall structures <NUM> are straight with the exception of guide turns <NUM> extending a short distance from the leading edge <NUM> to guide air from a generally radially outward flow within the plenum <NUM> and shift that air generally axially. Although the outlet plenum <NUM> may have similar turns, modeling shows these to be less advantageous at the outlet plenum. The wall structures <NUM> span between adjacent interior faces 174A, 174B (<FIG>).

The wall structures <NUM> may divide internal flows into smaller passages, thereby increasing surface area, more equally distributing, and/or accelerating internal flows. They may also tie the walls of the plate together to prevent ballooning under elevated temperatures and pressures.

The exemplary inlet plenum <NUM> converges in axial dimension from ID to OD or downstream along the first flowpath. Similarly, the exemplary outlet plenum <NUM> diverges in axial dimension from OD to ID or downstream along the first flowpath toward the outlet <NUM>. Such respective convergence and divergence may reduce internal losses and prevents separation of flow.

The interior of the plate may optionally include integral surface enhancement features. <FIG> shows exemplary features <NUM>/<NUM>' as chevron ribs, apex-upstream, within the flow passage legs <NUM>. An exemplary configuration places the ribs in rows with two rows in each passageway, each row bridging up the adjacent surface of the adjacent wall <NUM> and opposite ends of the ribs of each row interdigitating slightly. The chevron features serve as trip strips to locally increase the surface friction at the boundary layer (increasing the local heat transfer coefficient) and to develop a mixing vortex within each passage leg <NUM> (to more uniformly distribute thermal energy within the first flowpath). Furthermore, there are a multitude of integral surface enhancement features known in the art. Notable alternatives include trip strips (or turbulators) perpendicular to the flow or skewed at an angle. Ribs <NUM>' differ from the ribs <NUM> in that they have extended filleting.

<FIG> shows fin arrays <NUM> spanning the gaps between each adjacent plate substrate. The terminal plates in each array may similarly have fins spanning to the adjacent shroud <NUM> circumferential end <NUM>, <NUM>.

<FIG> shows a preassembly of a plate substrate and a single fin array. The exemplary plate has an array only on the second circumferential face <NUM> so that the first circumferential face <NUM> of the adjacent plate to the second side of that plate does not have a separate such fin array. The exemplary square wave nature (e.g., with rounded corners) of the fin array <NUM> (<FIG>) has a series of troughs <NUM> and peaks <NUM> with legs <NUM>, <NUM> extending between adjacent troughs and peaks. The legs thus form the ultimate fins. The exemplary troughs are attached to the second circumferential face <NUM> such as by welding, brazing, diffusion bonding, or the like. When a plate array is assembled, the peaks <NUM> will contact the adjacent first circumferential face <NUM> of the next plate substrate. To improve heat transfer, upon such assembly, there may be a diffusion bond, braze, or weld, securing the peaks <NUM> to such adjacent first circumferential face <NUM> (or the adjacent shroud wall). As noted above, where needed, a terminal plate in the plate bank may be initially fabricated with fin arrays <NUM> on both faces <NUM> and <NUM>. <FIG> also identifies the cross-sectional width Cw and the cross-sectional height CH of the passage leg <NUM>. These features are further discussed below.

As noted above, exemplary assembly techniques involve brazing the plates to the manifold unit <NUM>. In several exemplary techniques, the shroud(s) <NUM> are used as an assembly aid. In several examples, the shroud(s) <NUM>, manifold unit <NUM>, plate substrates <NUM>, and fin arrays <NUM> are separately formed. Ultimately, the shroud(s) are used to hold the associated plates to the manifold unit during further securing (e.g., brazing).

In one group of examples, the shrouds (e.g., bent and punched sheetmetal) are applied after the plates' substrates are temporarily mounted to the manifold. For example, finned plates may be preassembled by placing braze material (e.g., foil) between the relevant plate face(s) and the associated fin array(s). Each fin array may then be secured by one or more tack or resistance welds. Also, such a braze foil may be attached (e.g., tack or resistance welded) to a plate face that does not have its own fin array but will be brazed to the adjacent fin array of the adjacent plate.

The plates may then be preassembled to the manifold. For example, braze material may be applied to the manifold or the plates (e.g., braze paste applied to the features <NUM> or one or more foil sheets (e.g., precut to accommodate any plugs) applied to the features <NUM>). The braze paste or foil may extend to regions of the manifold that will ultimately mate with the shroud. For example, <FIG> shows each shroud end wall <NUM>, <NUM> including a base flange <NUM> along the surface <NUM> of the main body (<FIG>). Then the plate proximal edge portions may be inserted to the features <NUM> (e.g., with the plate plugs mating with the associated manifold ports) and held (loosely) by gravity and/or the mechanical interfitting.

The shroud end wall <NUM>, <NUM> inboard faces may receive braze material in similar fashion to the unfinned plate faces (e.g., tack welding of braze foil). The shroud may then be placed over the plate array and temporarily secured to the manifold. A temporary securing may involve tack welding of the flange <NUM> to the main body or may involve screws or other fasteners.

A clamping fixture (not shown - e.g., end plates joined by ratcheting bands or clamping screws) may be applied across the outboard faces of the shroud end walls <NUM>, <NUM> (e.g., before or after the temporary securing of the shroud to the manifold) and tightened to apply a pre-compression force across the array of plates. The clamped assembly may be transferred to a braze oven, heated to braze the various components to each other, and then removed and cooled.

In other examples, the shrouds may act as a fixture to which the plates' substrates are pre-mounted (e.g., put in place with the shroud slots receiving the plate projections and secured via brazing). The plates may have the fin arrays already preassembled or the fin arrays and braze foils may then be inserted between plate substrates and between the terminal plate substrates and the shroud end walls. Optionally, the clamping fixture may then be applied. This preassembled combination may then be mated to the manifold unit with the respective plate proximal edges mating with the sockets <NUM> and the plate plugs mating with the associated manifold ports. Braze material (e.g., foil placed along the sockets <NUM>) may be included in the assembly or braze material may subsequently be added.

The mating may contact the shroud(s) <NUM> and the manifold unit <NUM>. The shroud may be temporarily secured such as in the prior example. As with the plates, braze foil may be pre-sandwiched between the flanges and the main body or braze material may be subsequently introduced. With the shroud(s) thus holding the plates in place, the braze process may be conducted (e.g., via heating the assembly in a furnace and melting the braze foils or by locally brazing).

Such processes may have one or more advantages. For example, it may mitigate the build-up of tolerances between adjacent components, creating narrow braze joints, and thereby improving fin-to substrate bonding.

Additionally, the shroud <NUM> may help protect the terminal fin arrays (at the ends of each plate array) from damage during installation of the heat exchanger to the engine, during engine operation, and during engine maintenance. The fin arrays may be constructed of thin material (≤<NUM> inch thick) and are thus relatively fragile.

Furthermore, in use, the shrouds may help maintain consistent flow near the distal edge of the plates and at the terminal fin arrays (at the ends of each plate array). The shroud constrains the second flow stream within the fin arrays, which would otherwise escape through the open ended channels.

Such shrouds may be used with other panel arrangements. They may be used with non-parallel plates or with plates extending radially inward from a concave arcuate surface (in which case, the circumferential OD wall <NUM> would become a circumferential inner diameter (ID) wall).

Further shroud variations may integrate damping features allowing relative movement of plates to be frictionally damped. Examples are given in <CIT>, and entitled "Aircraft Heat Exchanger Panel Array Interconnection".

<FIG> shows a plate <NUM> which may be otherwise similar to the plate <NUM> but which adds reinforcement walls <NUM> joining the opposite faces 174A and 174B in the inlet plenum <NUM> and outlet plenum <NUM>. The exemplary walls are in parallel pairs laterally spaced apart near the associated inlet <NUM> or outlet <NUM> and help structurally reinforce the casting.

<FIG> also shows several other geometric considerations according to the present invention covered by the claims. Wall <NUM> straight portion length LW and on-center spacing Sw are shown. An angle θLE of the leading edge relative to the downstream direction and an angle θTE of the trailing edge relative to the downstream direction are shown. Plate root length L<NUM> and plate tip length L<NUM> are shown.

θLE is essentially <NUM>° (e.g., <NUM>°-<NUM>°). This helps equally distribute oncoming flow <NUM> radially. An angled leading edge would result in redirection of oncoming flow towards the lagging end (ID or OD) of the leading edge.

θTE is greater than <NUM>° (e.g., <NUM>°-<NUM>°). This is desirable, because the associated taper in length will increase the natural frequency of the panel and reduce the susceptibility to rapid high cycle vibrations. The precise value may be a result of the design choices made for the internal casting core configuration regarding the taper of the inlet plenum <NUM> and outlet plenum <NUM>, as well as the uniformity of the straight portion length Lw.

The configuration of the panel can cause unequal pressure distributions among the different passage legs <NUM> of the wall structure <NUM>, resulting in flow being biased towards the passages near the root. Several options exist to vary the flow resistance among the passage legs <NUM> and equalize the flow. Firstly, the size, pitch, and/or quantity of trip-strips <NUM>/<NUM>' may be non-uniform. This may even go so far as to leave a portion of the length LW to be without trip strips while another has (e.g., <FIG> discussed below). The second option is to progressively reduce the passage length LW near the tip of the panel (<FIG>). The third option is to reduce the cross-sectional area of the passages near the root. This can include variations of the on-center spacing Sw (plate/panel <NUM> of <FIG>) and/or passage width Cw (<FIG>) that are uniform along the length Lw, as well as a local variation in Cw or passage height CH along the length LW. An exemplary change is of about <NUM>% in cross-sectional area from each leg to the next. For essentially constant CH, this means a corresponding <NUM>% change in Cw. More broadly, an average change is from <NUM>% to <NUM>% or <NUM>% to <NUM>%. or <NUM>% to <NUM>%. Exemplary net spacing change may be <NUM>% to <NUM>% or <NUM>% to <NUM>%. A local method for varying the cross-sectional area can be accomplished by utilizing the length of guide turns <NUM>. Longer guide turns <NUM> near the proximal edge <NUM> relative to the distal edge <NUM> will divert flow to the distal edge.

<FIG> shows a plate/panel <NUM> with further exemplary leg-to-leg variations in integral surface enhancements. A first variation is that the height and the width (WR of <FIG>) vary from leg-to-leg, generally progressively decreasing stepwise from the proximal edge <NUM> toward the distal edge <NUM>. For example, multiple adjacent groups of the legs may have the same ribs. An exemplary progressive decrease in height and width is <NUM>% (more broadly, <NUM>% to <NUM>% of the height and width of the largest ribs). This change may function to provide less backpressure in the passage legs <NUM> near the distal edge <NUM>. This backpressure reduction functions to compensate for the uneven pressure distribution noted above and to help provide adequate flow near the distal edge.

A further illustrated change which may exist independently is the local absence of ribs in select areas of select legs. In particular, the exemplary embodiment shows the outermost few legs as lacking ribs along downstream portions. The length of the ribless area progressively increases within this group. This may function to provide less backpressure in the passage legs <NUM> near the distal edge <NUM>.

<FIG> and <FIG> show further aspects of possible use of the dead space or buffer cavity <NUM> for cooling. <FIG> shows the main body <NUM> ID surface <NUM> as having a gap <NUM> between sections 96A and 96B that are intact cylindrical or frustoconical sections inboard of the respective associated panel banks. This divides a main body into respective sections associated with the panel banks. Each of the main body sections has an inner diameter port 410A, 410B to an associated branch passageway 115A, 115B of the buffer cavity. The branches extend to respective outlets 412A, 412B along the circumferential ends <NUM> and <NUM>, respectively. In operation, circumferentially and radially-extending blocker/baffle structures (not shown) aside the heat exchanger ends <NUM>, <NUM> (e.g., attached to mounts <NUM>) forward/upstream of the ports 412A, 412B may create low pressure zones at the ports 412A, 412B to draw the flow through the branches. Additional inlet scoop or other features (not shown) may help drive flow.

<FIG> and <FIG> more schematically show an alternate heat exchanger <NUM> which may use any of the aforementioned plates/panels. The exemplary heat exchanger has a single inlet <NUM> and a single outlet <NUM> for the first flow <NUM>. As with the heat exchanger <NUM>, these are on respective fittings <NUM>, <NUM>. As with the exemplary heat exchanger <NUM>, a single manifold structure <NUM> provides the inlet manifold <NUM> and outlet manifold <NUM> and their associated plenums <NUM> and <NUM>. The structure <NUM> has a main body <NUM> having a leading end <NUM>, a trailing end <NUM>, a first circumferential end <NUM>, a second circumferential end <NUM>, an ID surface <NUM>, and an OD surface <NUM>. In this example, the ID surface <NUM> is concave circumferentially and the OD surface <NUM> is convex so that the manifold structure <NUM> is an outer diameter (OD) manifold from which the plates/panels <NUM> extend radially inward. In this particular example, the plates extend radially inward converging towards their distal edges <NUM> (<FIG>). In alternative embodiments, the plates may be parallel to each other as in the exemplary heat exchanger <NUM>.

A further difference of the exemplary heat exchanger <NUM> versus the exemplary heat exchanger <NUM> is that the inlet port and outlet port both are along conduits <NUM>, <NUM> extending from one of the main body <NUM> circumferential ends. In the illustrated example, they extend from the same end although a further opposite end example is discussed below. In the illustrated example, the plenums <NUM>, <NUM> still taper away from the associated conduit <NUM>, <NUM>. In this embodiment, the tapering allows a dead space <NUM> to be formed between facing walls of the plenums with the dead space diverging away from the circumferential end bearing the conduits.

One relevant aspect of the exemplary heat exchanger main body <NUM> is that when formed as a cylindrical section (e.g., not frustoconical) two identical such main bodies may be assembled end-to-end so that their respective ports are at opposite ends of the assembly. Relative front-to-back symmetry of the main body allows the plates of one main body to be installed opposite those of the other main body (relative to the main body) so that all plates face the same direction along the second flowpath <NUM>.

In yet a further variation of a heat exchanger <NUM> (<FIG>) based on the heat exchanger <NUM> discussed above, the conduits <NUM> and <NUM> may be on opposite circumferential ends so that the dead space <NUM> extends diagonally across the main body similar to the buffer cavity <NUM> of heat exchanger <NUM>.

<FIG> schematically shows a gas turbine engine <NUM> as a turbofan engine having a centerline or central longitudinal axis <NUM> and extending from an upstream end at an inlet <NUM> to a downstream end at an outlet <NUM>. The exemplary engine schematically includes a core flowpath <NUM> passing a core flow <NUM> and a bypass flowpath <NUM> passing a bypass flow <NUM>. The core flow and bypass flow are initially formed by respective portions of a combined inlet airflow <NUM> divided at a splitter <NUM>.

A core case or other structure <NUM> divides the core flowpath from the bypass flowpath. The bypass flowpath is, in turn, surrounded by an outer case <NUM> which, depending upon implementation, may be a fan case. From upstream to downstream, the engine includes a fan section <NUM> having one or more fan blade stages, a compressor <NUM> having one or more sections each having one or more blade stages, a combustor <NUM> (e.g., annular, can-type, or reverse flow), and a turbine <NUM> again having one or more sections each having one or more blade stages. For example, many so-called two-spool engines have two compressor sections and two turbine sections with each turbine section driving a respective associated compressor section and a lower pressure downstream turbine section also driving the fan (optionally via a gear reduction). Yet other arrangements are possible.

<FIG> shows the heat exchanger <NUM> (or other heat exchanger above) positioned in the bypass flowpath so that a portion of the bypass flowpath <NUM> becomes the second flowpath <NUM> and a portion of the bypass flow <NUM> becomes the second airflow <NUM>.

The exemplary first airflow <NUM> is drawn as a compressed bleed flow from a diffuser case <NUM> between the compressor <NUM> and combustor <NUM> and returned radially inwardly back through the core flowpath <NUM> via struts <NUM>. Thus, the flowpath <NUM> is a bleed flowpath branching from the core flowpath.

Claim 1:
A heat exchanger plate (<NUM>; <NUM>; <NUM>; <NUM>) for a heat exchanger (<NUM>; <NUM>; <NUM>) of a gas turbine engine (<NUM>) for providing heat transfer between a first flow (<NUM>) along a first flowpath (<NUM>) and a second flow (<NUM>) along a second flowpath (<NUM>), the heat exchanger plate (<NUM>; <NUM>; <NUM>; <NUM>) comprising:
a first face (<NUM>) and a second face (<NUM>) opposite the first face (<NUM>);
a leading edge (<NUM>) along the second flowpath (<NUM>) and a trailing edge (<NUM>) along the second flowpath (<NUM>);
a proximal edge (<NUM>) having at least one inlet port (<NUM>) along the first flowpath (<NUM>) and at least one outlet port (<NUM>) along the first flowpath (<NUM>); and
at least one passageway along the first flowpath (<NUM>),
wherein the at least one passageway comprises:
an inlet plenum (<NUM>) extending from the at least one inlet port (<NUM>) of the plate (<NUM>; <NUM>; <NUM>; <NUM>);
an outlet plenum (<NUM>) extending to the at least one outlet port (<NUM>) of the plate (<NUM>; <NUM>; <NUM>; <NUM>); and
a plurality of legs (<NUM>) fluidically in parallel between the inlet plenum (<NUM>) and the outlet plenum (<NUM>),
characterised in that:
the leading edge (<NUM>) is <NUM>° to <NUM>° off the proximal edge (<NUM>); and
the trailing edge (<NUM>) is more than <NUM>° off the proximal edge (<NUM>) in exterior angle so that a length decreases from the proximal edge (<NUM>) to a distal edge (<NUM>).