COOLING SYSTEM

Abstract

A cooling system for an aircraft, including a heat exchanger for cooling a hot fluid with cooling air, an air intake for the supply of cooling air and a Coandă-effect air amplifier for the creation of a flow of cooling air.

Claims

1. A cooling system for an aircraft, comprising: a heat exchanger for cooling a hot fluid with cooling air, comprising: a cooling air inlet in fluid communication with a cooling air outlet and a hot fluid inlet in fluid communication with a hot fluid outlet by means of one or more hot fluid conduits, wherein the one or more hot fluid conduits are configured to transfer heat between a flow of hot fluid flowing between the hot fluid inlet and the hot fluid outlet, and a flow of cooling air flowing between the cooling air inlet and the cooling air outlet; an air intake configured to supply cooling air from outside of the cooling system to the heat exchanger, wherein the air intake is in fluid communication with the cooling air inlet of the heat exchanger; and a Coandă-effect air amplifier comprising an air amplifier inlet, an air amplifier outlet, a pressurized air inlet and a pressurized air outlet configured as a nozzle, the Coandă-effect air amplifier being configured to create a flow of cooling air between the air amplifier inlet and the air amplifier outlet induced by a stream of pressurized air injected through the nozzle, wherein the air amplifier inlet is in fluid communication with the cooling air outlet of the heat exchanger.

2. The cooling system according to claim 1, comprising a plurality of hot fluid conduits, wherein the plurality of hot fluid conduits are arranged in a tubular configuration defining a hollow interior volume, and wherein the cooling air flows between the hot fluid conduits and through the hollow interior volume of the tubular configuration of the hot fluid conduits.

3. The cooling system according to claim 1, wherein the one or more hot fluid conduits, the hot fluid inlet and the hot fluid outlet define at least part of a hot fluid circuit.

4. The cooling system according to claim 2, wherein the heat exchanger comprises a plurality of hot fluid circuits with corresponding hot fluid inlets and hot fluid outlets.

5. The cooling system according to claim 4, wherein the hot fluid circuits are arranged in different sectors of the tubular configuration.

6. The cooling system according to claim 4, wherein each hot fluid circuit is configured to transport a different hot fluid.

7. The cooling system according to claim 4, wherein a value of at least one dimension of a hot fluid conduit of a first hot fluid circuit is different from a value of the same dimension of a hot fluid conduit of a second hot fluid circuit.

8. A power unit for an aircraft, comprising an engine and a cooling system according to claim 1.

9. The power unit according to claim 8, further comprising a source of high pressure air configured to feed the pressurized air inlet of the Coandă-effect air amplifier.

10. The power unit according to claim 8, wherein one or more of the hot fluid inlets are in fluid communication with a hot fluid source of the engine.

11. The power unit according to claim 8, wherein the cooling system is housed in a compartment, and the engine is housed in a compartment separated from the compartment housing the cooling system.

12. An aircraft comprising a power unit according to claim 8.

13. The aircraft according to claim 12, wherein the power unit is positioned in an aft section of the aircraft.

14. The aircraft according to claim 13, wherein the cooling system is positioned in a housing with rails.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] These and other characteristics and advantages of the invention will become clearly understood in view of the detailed description of the invention which becomes apparent from a preferred embodiment of the invention, given just as an example and not being limited thereto, with reference to the drawings.

[0053] FIG. 1 shows an embodiment of the cooling system attached to the tail section of an aircraft.

[0054] FIG. 2 shows the cooling system partially extracted from its housing in the tail section of an aircraft.

[0055] FIG. 3 shows the cooling system attached to the tail section of an aircraft, with the fairing removed.

[0056] FIGS. 4a-4b show a section view of an embodiment of the power unit and of the cooling system.

[0057] FIG. 5 shows a schematic view of the power unit in the tail section of an aircraft.

[0058] FIG. 6 shows a partial section view of an embodiment of the cooling system.

[0059] FIG. 7 shows an aircraft with a cooling system according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] Due to the present invention, it is possible to increase the efficiency of a cooling system (14) of an aircraft (16) and at the same time reduce the dead weight of the aircraft (16). As an additional effect, the cooling system (14) comprises fewer moving parts, which simplifies the maintenance operations, reduces the production costs and increases the overall reliability of the cooling system (14).

[0061] FIG. 1 shows a preferred embodiment of the invention, wherein the cooling system (14) is used in combination with an engine (13), forming a power unit (15) assembly installed in an aircraft (16), preferably in its aft section, in or near the tail cone. The engine (13) of the power unit (15) can be an auxiliary power unit (APU) or any other type of engine. Also the engine (13) needs not be a thermal engine, and can be an electric motor as well.

[0062] FIGS. 4a and 4b show a section view of an embodiment of the cooling system (14), which is the element responsible for the cooling of the flow of hot fluid with the flow of cooling air.

[0063] The cooling system (14) comprises a heat exchanger (12), an external air intake (11) for the supply of cooling air from outside of the cooling system (14) to the heat exchanger (12), and a Coandă-effect air amplifier (7).

[0064] The heat exchanger (12), depicted in detail on FIG. 4b, accomplishes the transference of heat. It comprises a plurality of hot fluid conduits (3) arranged according to a tubular configuration and extending from a first end of the heat exchanger (12) to a second end of the heat exchanger (12), a cooling air inlet (1) which in the shown embodiment corresponds with the openings left between the hot fluid conduits (3), and the cooling air outlet (2) at the second end of the heat exchanger (12); additionally the heat exchanger (12) comprises a hot fluid inlet (4) and a hot fluid outlet (5) in fluid communication with the hot fluid conduits (3).

[0065] Like other conventional heat exchangers, the depicted heat exchanger (12) transfers heat between a hot fluid (either a gas or a liquid), flowing from hot fluid inlet (4) to the hot fluid outlet (5) through the hot fluid conduits (3), and a flow of cooling air, flowing from the cooling air inlet (1) to the cooling air outlet (2). The cooling air flows first between the hot fluid conduits (3), and then through the hollow interior volume created by the tubular configuration of the bundle or bundles of hot fluid conduits (3).

[0066] In this embodiment, the configuration is optimized for a higher mass flow rate of coolant (the cooling air) by means of a tubular configuration.

[0067] FIG. 6 shows the air amplifier (7) and the heat exchanger (12) with a partial section, showing the hot fluid inlet (4) at a first end of the heat exchanger (12), and the hot fluid outlet (5) at a second end of the heat exchanger (12), opposite to the first end. In this embodiment, both the hot fluid inlet (4) and the hot fluid outlet (5) have a chamber configuration, and are in fluid communication with the hot fluid conduits (3). As it is apparent from FIG. 6, in this embodiment, there is a large number of hot fluid conduits (3) and they have a small diameter in relation with the length of the hot fluid conduits (3). Also, each hot fluid conduit (3) is spaced from the neighboring hot fluid conduit (3) by a distance which is dependent on the intended performance of the heat exchanger (12), but must allow the passage of the cooling air between the hot fluid conduits (3); therefore, the plurality of these spacings form the cooling air inlet (1).

[0068] The tubular configuration of the hot fluid conduits (3) can also be observed, with rows of conduits (3) forming several circumferences positioned concentrically. This tubular configuration creates a hollow interior volume in the core of the heat exchanger (12), which is in communication with the air amplifier (7) by means of the cooling air outlet (2), at the second end of the heat exchanger (12). In a simple embodiment, all the hot fluid conduits (3) are part of a single hot fluid circuit (6); however, the embodiment of FIG. 6 comprises three hot fluid circuits (6) (not shown in this view), each of them with respective hot fluid inlets (4) and outlets (5), positioned on a sector of the tubular configuration; in this view, the depicted hot fluid circuit (6) takes a sector of roughly 120°.

[0069] One of the advantages of the embodiment with several hot fluid circuits (6) is the capability to cool down several hot fluids at the same time, for instance compressed air and lubricating oil. Since these two fluids have different physical properties, the heat transfer ratio is different for each fluid. Accordingly, the dimensions of the elements of the hot fluid circuits (6), comprising the hot fluid inlet (4), hot fluid outlet (5) and hot fluid conduits (3), are preferably designed depending on the specific physical properties of the fluid, such as density, heat capacity, viscosity, etc.

[0070] In a preferred embodiment, the heat exchanger (12) comprises three hot fluid circuits (6) for engine coolant liquid, generator oil and compressed air, with their corresponding inlets (4), outlets (5) and conduits (3).

[0071] Now turning to FIGS. 2 and 3, a specific embodiment of the external air intake (11) can be observed in the form of openings between stringers of a tail cone section in the portion immediately upstream of the cooling system (14) housing. The purpose of the external air intake (11) is establishing a fluid communication between the mass of air surrounding the aircraft (16), i.e., the external air, with the cooling air inlet (1). The external air intake (11) provides the majority of the cooling air, and it is advantageously open to the exterior of the aircraft (16) during the operation of the cooling system (14). An alternative embodiment (not shown in the figures) comprises a powered hatch or door closing an opening in the skin of the aircraft (16); the effective opening cross section of the external air intake (11) can thus be regulated like a valve, thereby controlling the amount of cooling air fed to the heat exchanger (12).

[0072] The Coandă-effect air amplifier (7), or simply air amplifier (7), is a device which exploits the benefits of the Coandă-effect for creating a greater mass flow, or inducted fluid flow, with a smaller, high velocity stream of fluid, in this case air; FIG. 4b shows an embodiment of the air amplifier (7), comprising a nozzle (8) for injecting a high pressure (or velocity, depending on the degree of expansion) air stream over a Coandă-effect profile (9). Although the shape of the Coandă-effect profile (9) depends on the design requirements and parameters, in most cases it has a slightly curved, convex profile from the point of view of the stream. The high pressure air stream is projected over the profile (9), roughly in a tangent direction in respect of the surface of the profile (9), such that the stream is deflected towards the surface of the profile (9) following its curvature, generating a region of low pressure on the surface of the profile (9); as a result, the surrounding air is thrusted towards the surface of the profile (9), either creating a flow of air or accelerating an existing flow.

[0073] The high pressure stream injected over the Coandă-effect profile (9) is generated by feeding high pressure air in a chamber (10) with a closed configuration, and projecting it over the profile (9) through a nozzle (8) with a closed configuration as well. Again, the specific shape of the nozzle (8) (such as the area and shape of the opening) depends on the particular design requirements and parameters. In any case, the nozzle (8) is favorably positioned upstream of the profile (9), so as to make use of the whole surface of the profile (9).

[0074] A preferred configuration of the Coandă-effect profile (9), as happens with the heat exchanger (12), is a tubular configuration, preferably substantially cylindrical. This configuration allows for the creation of a flow within the Coandă-effect air amplifier (7), avoiding external disturbances of the flow. Also the profile (9) is preferably positioned downstream of the nozzle (8); in order to work properly, the profile (9) should be arranged with its curved part extending chord-wise, and the profile extending in the span direction such that it forms a closed surface.

[0075] The chamber (10) is roughly configured as a torus, with one or more inlet openings for feeding compressed air, and an outlet opening formed by the nozzle (8). Preferably, the nozzle (8) extends uninterrupted along the whole perimeter of the air amplifier (7), but it can be split for structural or constructional reasons.

[0076] FIGS. 1 and 5 show an embodiment of the power unit (15), defined as the assembly of an engine (13) and a cooling system (14) as described above.

[0077] In most cases, the cooling system (14) will be dedicated to the cooling of the engine (13), and for convenience, it should be positioned near the engine (13). Thus, if the engine (13) is a gas turbine APU, hot fluids from the engine (13) such as lubricating oil from the generator and water coolant, can be extracted by means of conduits, and fed to corresponding hot fluid circuits (6) of the heat exchanger (12). Additionally, high pressure from the compressor stage of the engine (13) can be cooled down before entering a combustor.

[0078] Most engines, even electric motors, produce waste heat; if this waste heat reaches the heat exchanger (12) by heat conduction or increases the temperature of the cooling air, the efficiency of the cooling system (14) may be reduced significantly. Therefore, it is beneficial to have the engine (13) housed in a different space to the cooling system (14), for example as shown in FIGS. 1 and 5, by housing the engine (13) in a separate compartment; or in a simpler configuration, not depicted in the figures, splitting the housing of the power unit (15) with an isolated bulkhead.

[0079] The flexibility of the cooling system (14) allows for the installation of the sources of hot fluids at a distant location; for instance, the cooling system (14) can be placed in the aft section of the aircraft (16) while the engine (13) can be positioned in a middle section of the aircraft (16), owing to a better balance of the aircraft (16), room availability, etc.

[0080] In a preferred embodiment, as shown in FIGS. 1 and 2, the whole assembly of the power unit (15) is introduced in the aircraft (16); an advantageous position for the cooling system (14) is the tail cone of the aircraft (16), where the exhaust flow of the cooling air (at this stage warm) would be less disturbing for the operation of the aircraft (16). Also, the tail cone is a section of the aircraft (16) which is not well suited for the storage of cargo, and can be better used in this way.

[0081] In the same embodiment of FIGS. 1 and 2, the cooling system (14) is configured as a package or cartridge, with standardized dimensions; preferably, the configuration of the cartridge is such that it can be introduced in the APU bay. To that end, the cooling system (14) cartridge may comprise guiding slots matching with existing APU guiding rails.

[0082] FIG. 7 shows an aircraft (16) with a cooling system (14) as described above, positioned at the aft section of the aircraft (16).

[0083] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.