Patent ID: 12203708

DETAILED DESCRIPTION

FIG.1illustrates a gas turbine engine10of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan12through which ambient air is propelled, a compressor section14for pressurizing the air, a combustor16in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases around the engine axis11, and a turbine section18for extracting energy from the combustion gases.

The compressor14, fan12and turbine18have rotating components which can be mounted on one or more shafts. Bearings20are used to provide smooth relative rotation between a shaft and casing (non-rotating component), and/or between two shafts which rotate at different speeds. An oil lubrication system22including an oil pump24, sometimes referred to as a main pump, and a network of conduits and nozzles26, is provided to feed the bearings20with oil. Seals28are used to delimit bearing cavities32and contain the oil. A scavenge system30having cavities32, conduits34, and one or more scavenge pumps36, is used to recover the oil from the bearing cavities32, which can be in the form of an oil foam at that stage. The oil pump24typically draws the oil from an oil reservoir38, and a heat exchanger40, can be used in the return line to cool the oil with air or another fluid such as fuel, for instance.

Generally, the heat exchanger40can have two fluid circuits distinct from one another from the point of view of fluid circulation (i.e. the fluids do not mix within the heat exchanger) and one or more region where the two fluid circuits are placed in thermal exchange contact with one another, meaning that during operation, heat from the hotter one of the circulating fluids is transferred to the colder one of the circulating fluids across some form of structure which separates the fluid circuits from one another. Both cross-flow and concurrent flow configurations are possible. In the cross-flow configuration, the first fluid circulates in a direction opposite the direction of the second fluid, whereas in the concurrent flow configuration both fluids circulate in the same orientation. Different ones of these configurations can be preferable in different embodiments, and the choice is left to the designer of a specific embodiment.

FIGS.2A-2Dpresents a portion of an example heat exchanger40and more specifically a portion surrounding a heat transfer region42. As presented generally inFIG.2A, the heat exchanger40includes at least three components: a first housing44having an arm46, a second housing48having a sleeve50having a hollow tube open at both ends and configured for receiving the arm46, and an adapter52configured for being secured to the tip of the arm46, also referred to as the proximal end54of the arm. The arm46has a first, internal, fluid path for conveying a first fluid along the heat transfer region42. In this embodiment, a second fluid path if formed internally to the sleeve50, and externally to the arm46, otherwise said between the structure/wall of the sleeve50and the structure of the arm46, when the heat exchanger40is in the assembled configuration, such as shown inFIG.2B. Another adapter56can be integrated to the second housing48, in fluid flow communication with the hollow of the sleeve50/second fluid path. The first fluid path can form part of a first circuit including a first inlet and a first outlet (only one of which is shown inFIG.2B, associated to the adapter52), whereas the second fluid path can form part of a second circuit including a second inlet and a second outlet (only one of which is shown inFIG.2B, associated to the adapter56).

In this specification, the expression “proximal” will be used to refer to the region where the arm46protrudes from the sleeve50, and the expression “distal” can be used to refer to the other end58of the length of the arm46, to facilitate reference in the text below. Accordingly, the sleeve50can be said to have an internal cavity, or hollow, extending from a proximal opening at the proximal end, to a distal opening at the distal end, and configured to receive the arm therein.

In the illustrated embodiment, the proximal end54of the arm46, shown enlarged onFIG.2C, can have a larger conduit portion, which will be referred to as a “mouth”60herein, which manifolds into a plurality of internal passages62to favor heat transfer efficiency with the other fluid. Similarly, the arm46has a generally cylindrical outer face64into which a number of circumferentially interspaced lengthwise-oriented grooves66are formed, creating a plurality of outer passages of the second fluid path in the heat transfer region42. This latter plurality of passages can be referred to herein as the outer passages, though it will be understood that they are internal to the sleeve50, and in fact partially defined by the sleeve50. In this embodiment, and perhaps as best seen in FIG.2D, the grooves66/outer passages and many of the inner passages62(except the central one here) are circumferentially interspersed, which can be beneficial from the point of view of heat transfer efficiency.

Several reasons can motivate the use of an adapter52as a distinct component (seeFIG.2A) to be later assembled to the proximal end54of the arm66(seeFIG.2B). Indeed, in some embodiments, it can be preferred to manufacture the arm46by machining. In this case, one may need free lengthwise access to each one of the cross-sectional positions of the internal passages62from the proximal side of the arm46, to be able to drill each one of the internal passages along the length of the arm46. On the other hand, the adapter52can be provided with a port68and a coupler70which may prevent the desired access for the machining operation if it is not provided as a separate component to be later assembled. Moreover, in embodiments such as the one presented inFIG.2A to2D, the connector structure70, which can be required to satisfy fluid connection standards associated to the environment of use and/or for other considerations, may be transversally larger than the internal cross-sectional diameter of the sleeve50, and thereby prevent introduction of the arm46into the sleeve50if not provided as a separate component to be later assembled. Other restrictions specific to certain embodiments may also exist and motivate the use of an adapter as a distinct component.

When an adapter52is provided as a distinct component, the question arises as to how to establish a durable, reliable, low weight, low cost, leak-proof joint between the adapter52and the proximal end54of the arm46, and more specifically between the adapter52and the plurality of internal passages62. In some embodiments, not shown, it can be considered to use a plurality of distinct tubes to form the internal passages as opposed to machining. However, this may require forming individual weld joints between each end of each tube and some form of housing, which may not be satisfactory in some embodiments due to, for instance, the additional costs associated to the multiple weld joints including welding and inspection.

In an embodiment such as presented inFIG.2A-2D, it was preferred to establish the connection between the adapter52and the proximal end54of the arm with a single assembly step. In the illustrated, in addition to the individual internal passages62which can each individually be created along the length of the arm by drilling, a larger conduit portion which will be referred to as a mouth60, is also formed at the proximal end54of the arm46. The mouth60can also be machined by introducing a larger diameter machining tool into the proximal end54of the arm46, for instance. The mouth60can then manifold into the plurality of internal passages62. Moreover, outer passages66can be machined into the outer diameter64of the generally cylindrical geometry of the arm46by machining. In alternate embodiments, the cross-sectional shape of the arm can vary, and can be generally rectangular for instance, instead of circular.

In a cylindrical geometry, the mouth60can have a circular tip. The adapter can be provided with a first end72having generally the same geometry as the mouth60, such as, for this specific example, a cylindrical wall terminating at a circular tip (see cross-section ofFIG.2B), and the first end72of the adapter52can be welded to the circular tip of the mouth60. It will be understood, however, that in alternate embodiments, different approaches can be preferred, and it can be preferred to assemble the adapter to the proximal end of the arm by brazing, or even bolting flanges protruding transversally to the fluid path to one another, amongst other possible techniques.

As further shown inFIG.2D, the second adapter56can be transversally oriented and lead into the cavity formed between the sleeve50and the arm46. In this embodiment, the diameter of the cylindrical geometry of the arm can be smaller than the internal diameter of the sleeve to provide a spacing74between the arm46and the sleeve50in which the second fluid can circulate circumferentially in addition to circulating lengthwisely along the grooves66.

FIGS.3A and3Bpresent a first complete example embodiment of a heat exchanger140integrating the concepts presented above, and which can be used, for instance, as an air/oil heat exchanger. In this embodiment, the first fluid circuit178and the second fluid circuit180are both generally U-shaped and are close to coinciding in the heat transfer regions142,143. Indeed, while maintaining distinct passages from the fluid-circulation point of view, two distinct heat exchange regions142,143are provided in which heat can be transferred from the first fluid to the second fluid at a relatively high rate, across the structure of two, corresponding arms146,147engaged with respective sleeves150,151.

Indeed, the first housing144generally includes a first arm146and a second arm147, which can each individually, generally be constructed such as the arm46presented above. Both arms146,147are parallel and structurally interconnected by a structural member which will be referred to herein as a base182which has a first cavity184formed therein. The cavity184can be fluidly connected to the internal passages of both arms146,147, and act as a mixing chamber during operation, to further favor heat exchange efficiency along the second arm147, such as best seen inFIG.3B.

The heat exchanger140can further include both a first adapter152and a second adapter153, each one of the adapters being generally like adapter52and secured to the proximal end of a corresponding arm146,147.

The first fluid circuit178can thus extend from a port provided in the second adapter153, into a first inlet which can be in the form of a mouth161, can divide downstream of the mouth161into a first set of internal passages, recombine in the mixing chamber184, re-divide into a second set of internal passages extending along the second arm147, exit the internal passages into a first mouth160acting as a first outlet, and exit the heat exchanger140through a port in the first adapter152.

The two sleeves150,151can also be structurally interconnected by a transversal connecting segment186, which can alternately be referred to as a structural member, forming a distally-open channel in the second housing, the distally-open channel also fluidly connecting the hollows of the two sleeves150,151. A second mixing chamber188can be provided in the form of a spacing formed between the inner surface of the connecting segment186and the corresponding outer surface of the base182. Indeed, the base182and the channel can be configured for the distal opening of the channel to become closed by the base when in the assembled configuration such as shown inFIG.3B.

The second fluid circuit180can extend from a port provided in a second inlet to communicate with the spacing formed between the first arm146and the first sleeve150, and the lengthwise outer passages formed in the first arm146, extend along the length of the first arm146, communicate with the second mixing chamber188and then with the spacing formed between the second arm147and the second sleeve151, extend along the length of the second arm147, and to a transversally-oriented second outlet and more specifically across a port thereof. The latter presents a concurrent-flow configuration. For establishing a cross-flow configuration, the second inlet and second outlet can be interchanged, for instance, or the first inlet and the first outlet can be interchanged.

The first cavity184can also be machined in the base by introducing a drilling tool transversally into the base, and the hole can then be closed by a plug190, which can be secured in place in a watertight fashion by brazing or welding for instance.

In an alternate embodiment shown inFIG.3C, the first cavity185can be machined by milling a groove into the bottom of the base, for instance, and the groove can then be closed by capping, e.g. by welding a cap191onto the distal end of the base.

Returning toFIG.3B, the proximal ends154,155of the arms146,147can have an outer diameter designed to closely fit the internal diameter of the proximal ends of the sleeves150,151to form a close fit, and a watertight seal can be established between the corresponding peripheries by brazing, to name one example. Similarly, the connecting segment186of the second housing148and the base182of the first housing144can be shaped with a common periphery, allowing them to snugly engage and closely fit with one another, and a watertight seal can be established around the periphery by brazing, to name one example. In this example, the common periphery between the inner surface of the connecting segment186and the outer surface of the base182is obround, with two semi-circular features each at a corresponding transversal end, and a straight segment therebetween, though it will be understood that various other shapes can achieve a suitable result.

In this example, the adapters152,153,156,157are provided with a coupler70, which is configured for connecting with another component of the gas turbine engine. The coupler70has a broadened cross-section with a central aperture serving as a port, and two additional apertures. The coupler70can be configured to establish a watertight connection with a similar coupler feature of another device or conduit, and be secured to it by engaging bolts or the like into the two additional apertures, with a seal sandwiched between the abutting planar faces of the couplers.

FIGS.4A and4Bpresent a second complete example embodiment of a heat exchanger240integrating the concepts presented above. In this embodiment, the first and second fluid circuits278,280are both generally linear and generally coincide, though the second fluid circuit280may be said to have a widened U shape due to its transversally oriented inlet and outlet. Indeed, while maintaining distinct passages from the fluid-circulation point of view, a common heat exchange region242is provided in which heat can be transferred from the first fluid to the second fluid at a relatively high rate, across the structure of the arm.

The heat exchanger240can further include both a first adapter252and a second adapter253, the first adapter252being secured to the proximal end254of the arm246, and the second adapter253being secured to the distal end255of the arm246. In another embodiment, not shown, it can be preferred to include only a first adapter as an initially separate component later assembled to the arm, and to machine the second adapter integrally with the other machining operations performed on the arm, as even if the connector is wider than the internal cross-sectional area of the sleeve, the second adapter does not need to be engaged into the internal area of the sleeve at any time, only the proximal end of the arm is engaged at assembly, until it protrudes from the proximal end of the sleeve. However, in the illustrated embodiment, there was a challenge in forming an internal cavity similar to the mouth160to fluidly combine the individual flows of the internal passages, and for this reason, it was preferred to use a second adapter distinct from the initial structure of the arm, to form a second mouth161, and to later weld the second adapter253to the corresponding mouth161.

It was found that achieving multiple inner passages with low number of pieces can help in limiting the amount of weld/braze joints and thereby limit the number of NDT inspection points and potential failure points between circuits. It can provide satisfactory heat transfer efficiency by providing greater surface area between air and oil.

In some specific embodiments, a mixing chamber can be provided for both air and oil to facilitate the u-shaped design and keep the unit compact in length. The mixing chambers can help to prevent the fluids from reaching uniform temperature and velocities as they travel along the passages. The fluids can be forced to exit the passages into the mixing chambers and then re-enter the second set of passages as they travel up the second heat exchanger leg. The heat exchanger, which can be an oil cooler, can have 2 primary machined bodies—one for oil and one for air. By having only 2 bodies, the joints to seal and inspect can be minimized. The 2 parts can be brazed together at both ends to separate the fluids and allow for x-ray inspection. End caps, or end adapters, can be welded on the air side to allow connection of feed tubes. The air body can be kept as a single contiguous part with multiple air passages by gun-drilling or EDMing small holes down the lengths of the cooler legs. Maximum exposure to the oil for cooling can be provided by milled (or EDMed) channels between the drilled passages. Keeping all of the passages in a single body can allow for a single joint between the air and oil bodies as opposed to alternate embodiments using multiple tubes housed in a surrounding body. Indeed, multiple joints may be required to join multiple tubes and may make inspection of the joints by x-ray impossible, which may be undesired.

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.