AUTONOMOUS AIR CONDITIONING SYSTEM FOR AN AIRCRAFT

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of air conditioning in temperature and pressure for an aircraft cabin and relates more particularly to a self-powered air conditioning system. STATE OF PRIOR ART

[0002] Air conditioning is necessary in an aircraft to provide cabins with suitable pressure and temperature conditions. This air conditioning is achieved through a compression system.

[0003] The compression device can be powered by bleed air from propulsion engines or auxiliary power units.

[0004] However, in some aircraft, engine bleed air is either unavailable or cannot be used as a power source. In such cases, the compressor needs to be electrically powered, which can be done via the aircraft's electrical system. However, existing aircraft electrical systems use a relatively low-voltage alternating current of 115V, while the compressor requires a higher-voltage direct current of 540V. Powering the compressor from the aircraft's electrical system therefore necessitates numerous modifications to the existing system, both in terms of distribution architecture and the centralized electrical management system known as the electrical core. Such modifications are particularly demanding.

[0005] It is therefore desirable to overcome these drawbacks of the state of the art.

[0006] It is particularly desirable to provide a solution that allows the air conditioning compressor to be electrically powered without modifying the aircraft's existing electrical system, and in a simple manner. Furthermore, it is desirable to provide a solution that is easy to integrate into the aircraft.

[0007] US documents 2017 / 170494 A1, US 2009 / 211273 A1, US 2007 / 266695 A1 and US 2009 / 305092 A1 disclose prior art standalone air conditioning systems. DESCRIPTION OF THE INVENTION

[0008] One object of the present invention is to provide an autonomous air conditioning system for an aircraft, according to claim 1.

[0009] Thus, it is possible to perform cabin air conditioning autonomously, with a power supply provided by the autonomous air conditioning system itself, which avoids modifying a pre-existing electrical network of the aircraft.

[0010] According to a particular embodiment, the system further comprises a first heat exchanger carrying out a heat exchange between the compressed air supplied by the primary compressor and air taken from outside the aircraft, the first heat exchanger being located downstream of the primary compressor and upstream of the fuel cell assembly and the aircraft cabin.

[0011] According to a particular embodiment, the primary compressor is further supplied with mechanical energy by a first turbine, the first turbine receiving at input a third part of the compressed air supplied by the primary compressor and being located downstream of the first heat exchanger.

[0012] According to a particular embodiment, the system further comprises a secondary compressor, the secondary compressor being located between the primary compressor and the fuel cell assembly and compressing the second part of the compressed air supplied by the primary compressor.

[0013] According to a particular embodiment, the secondary compressor is supplied with mechanical energy by a second turbine, the second turbine receiving compressed air from the fuel cell assembly as input.

[0014] According to a particular embodiment, the system further comprises a second electric motor electrically powered by the electrical energy supplied by the fuel cell assembly, the second electric motor supplying mechanical energy to the secondary compressor.

[0015] According to a particular embodiment, the system further comprises a controller configured to implement an algorithm for regulating temperature, pressure and compressed air flow parameters and configured to send control instructions to active elements of the system ensuring control functions for compressed air flow, pressure and temperature.

[0016] According to a particular embodiment, the system further comprises a switch configured to connect electrically to the fuel cell assembly, and alternatively, a first electrical assembly and a second electrical assembly, the first electrical assembly being arranged to electrically supply the system, the second electrical assembly being arranged to electrically supply equipment external to the system and providing safety functions in the aircraft.

[0017] The invention also relates to an aircraft comprising such a self-contained air conditioning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of at least one exemplary embodiment, said description being made in relation to the accompanying drawings, among which: [ Fig. 1 ] schematically illustrates an aircraft with a self-contained air conditioning system; Fig. 2 ] schematically illustrates the autonomous air conditioning system according to a first embodiment; [ Fig. 3A ] schematically illustrates the autonomous air conditioning system according to a second embodiment; [ Fig. 3B ] schematically illustrates the autonomous air conditioning system according to a third embodiment; [ Fig. 4 ] schematically illustrates a controller for the autonomous air conditioning system and elements of the autonomous air conditioning system, and [ Fig. 5 ] schematically illustrates an example of the controller's hardware architecture. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0019] There Fig. 1 This schematically illustrates an aircraft 1 comprising at least one autonomous air conditioning system 100 (represented in Fig. 2 ). Aircraft 1 preferably includes two autonomous air conditioning systems 100.

[0020] There Fig. 2 schematically illustrates the autonomous air conditioning system 100 according to a first embodiment. This figure, as well as the Figs. 3A et 3B Thick solid lines represent air ducts, thin solid lines represent pipes carrying a heat transfer fluid, dashed lines represent electrical connections, and doubled lines represent mechanical power transmissions. Dihydrogen 191 pipelines are represented by mixed lines.

[0021] The self-contained air conditioning system 100 includes a primary compressor 10 that receives ambient air as an inlet and supplies compressed air. The self-contained air conditioning system 100 also includes a first motor 11 that transmits mechanical energy to the primary compressor 10. In other words, the first motor 11 drives the components of the compressor 10 to obtain compressed air from ambient air. The first motor 11 is controlled by a first motor control unit 111 (or "Motor Control Unit" or MCU) which determines the power and rotational speed of the first motor 11. The self-contained air conditioning system 100 includes a first air intake device 8 for drawing in ambient air from outside the aircraft 1. The first air intake device 8 includes, for example, one or more scoops for drawing in ambient air from outside the aircraft 1.An air duct connects the first air intake device 8 to the primary compressor 10 in order to inject ambient air into the primary compressor 10.

[0022] A portion of the compressed air supplied by the primary compressor 10 is injected into a cabin 17 of the aircraft 1, either directly from the primary compressor 10 or after passing through a first heat exchanger 13, which cools the compressed air. A valve 171 regulates the flow rate of compressed air injected into the cabin 17. Pressure and temperature conditions suitable for human activity can thus be achieved in the cabin 17 of the aircraft 1.

[0023] The autonomous air conditioning system 100 further includes a fuel cell stack 16. The fuel cell stack 16 is supplied with air, which contains oxygen, and hydrogen, and provides electrical power. The hydrogen supply comes from a hydrogen tank 19 located in the aircraft 1. The hydrogen tank 19 may be part of the autonomous air conditioning system 100 and dedicated to the fuel cell stack 16. Alternatively, the hydrogen tank 19 is external to the autonomous air conditioning system 100 and is also used for other functions requiring a hydrogen supply, such as propelling the aircraft 1, thus minimizing the footprint of the autonomous air conditioning system 100.

[0024] The fuel cell assembly 16 is supplied with air by compressed air from the primary compressor 10. In other words, a second part of the compressed air supplied by the primary compressor 10 is injected into the fuel cell assembly 16. Thus, the primary compressor 10 jointly supplies compressed air to the cabin 17 and the fuel cell assembly 16.

[0025] The first air sampling device 8 is therefore used both to condition the cabin air 17 and to enable the operation of the fuel cell assembly 16. The use of a single first air sampling device 8 instead of two, one which would be dedicated to the air conditioning of the cabin 17 and one which would be dedicated to the operation of the fuel cells 16, makes it possible to reduce the drag of the aircraft 1.

[0026] The electrical energy supplied by the fuel cell assembly 16 is recovered in an electrical circuit 20 in order to be at least partially transmitted to the first engine 11 and the first engine control unit 111. The first engine 11 and the first control unit 111 are thus electrically powered by the fuel cell assembly 16 and therefore do not require electrical energy from a pre-existing electrical network of the aircraft 1. Thus, the air conditioning of the cabin 17 is carried out autonomously, which avoids modifying the pre-existing electrical network of the aircraft 1.

[0027] The self-contained air conditioning system 100 includes the first heat exchanger 13 configured to exchange heat between warmer compressed air from the primary compressor 10 and cooler air drawn from outside the aircraft 1 by a second air intake device 9. The first heat exchanger 13 thus cools at least a portion of the compressed air from the primary compressor 10, as compression has caused an increase in air temperature. The first heat exchanger 13 is therefore located downstream of the primary compressor 10 and upstream of the fuel cell assembly 16.

[0028] At the outlet of the primary compressor 10, the portion of compressed air that is not injected directly into the cabin 17 circulates through the first heat exchanger 13 before being injected into the cabin 17. In this case, the first heat exchanger 13 is also located upstream of the cabin 17.

[0029] The autonomous air conditioning system 100 includes a diffuser 15 which allows the compressed air flow from the first heat exchanger 13 to the fuel cell assembly 16 on the one hand and to the cabin 17 and / or a first turbine 12 of the autonomous air conditioning system 100 on the other hand.

[0030] The first turbine 12 receives compressed air from the primary compressor 10, which is neither injected into the fuel cell assembly 16 nor into the cabin 17. The first turbine 12 expands the incoming compressed air to recover energy by reducing its pressure. The mechanical energy thus provided by the first turbine 12 is transmitted to the primary compressor 10, thereby increasing the compression efficiency of the compressed air. The air is then released into the atmosphere at the outlet of the first turbine 12.

[0031] The self-contained air conditioning system 100 further includes a cooling circuit 18 for cooling the fuel cell assembly 16 and the first engine 11. The cooling circuit 18 is a closed circuit and includes a pipe through which a heat transfer fluid circulates. The heat transfer fluid circulates successively through a cooling device (not shown) for the fuel cell assembly 16, through a cooling device (not shown) for the first engine 11, and through a second heat exchanger 14. The respective cooling devices for the fuel cell assembly 16 and the first engine 11 include, for example, cooling channels through which the heat transfer fluid flows, which act as heat exchangers and allow heat transfer from the fuel cell assembly 16, or the first engine 11 respectively, to the heat transfer fluid.The heat transfer fluid, heated by these heat transfers, then circulates in the second heat exchanger 14. This second heat exchanger 14 transfers heat from the heat transfer fluid to cooler air drawn from outside the aircraft 1 by the second air intake device 9 in order to cool the heat transfer fluid. The cooling circuit 18 may also include other components, such as a pump to activate the circulation of the heat transfer fluid and a heat transfer fluid reservoir.

[0032] Thus, the cooling of the fuel cell assembly 16 and the first engine 11 is shared by a single cooling circuit 18, which reduces the size, weight and cost of the autonomous air conditioning system 100.

[0033] In addition, the second air sampling device 9 is used both for the air conditioning of the cabin 17 and for the operation of the fuel cell assembly 16. The use of a single second air sampling device 9 instead of two thus makes it possible to reduce the drag of the aircraft 1.

[0034] According to an example embodiment, the first air sampling device 8 is a dynamic air inlet (“ram air inlet”) and the second air sampling device 9 is a scoop-type air inlet.

[0035] The autonomous air conditioning system 100 also includes a controller 40 (shown in Fig. 4 ) which allows control of elements of the autonomous system 100 and regulation of compressed air parameters, such as pressure, temperature, air flow injected into cabin 17 and air flow injected into the fuel cell assembly 16, in order to obtain compressed air suitable for the air conditioning of cabin 17 and the operation of the fuel cell assembly 16.

[0036] The autonomous air conditioning system 100 may also include a dehumidifier (not shown) located between the diffuser 15 and the first turbine 12, in order to reduce the amount of water present in the compressed air.

[0037] There Fig. 3A schematically illustrates the autonomous 100 air conditioning system according to a second embodiment.

[0038] According to the second embodiment, the autonomous air conditioning system 100 further comprises a secondary compressor 30 located between the diffuser 15 and the fuel cell assembly 16. The secondary compressor 30 allows the second part of the compressed air from the primary compressor 10 to be compressed in order to increase its pressure and thus obtain pressure conditions suitable for the operation of the fuel cell assembly 16. For example, the secondary compressor 30 allows the compressed air pressure to be increased from a pressure of about 0.8 bar to a pressure between 1.2 and 2 bar.

[0039] The secondary compressor 30 is thus installed in series with the primary compressor 10, on an air injection line to the fuel cell assembly 16. Since the amount of air required to supply the fuel cell assembly 16 is small compared to the amount of air required for cabin conditioning 17, the secondary compressor 30 is smaller than the primary compressor 10. Furthermore, the volume of the primary compressor 10 is equivalent to that of a compressor used solely for cabin conditioning 17. Thus, installing the secondary compressor 30 in series reduces the weight and size of the self-contained air conditioning system 100 compared to an installation using a dedicated compressor for the fuel cell assembly 16, which would draw air from outside the aircraft.This improves the efficiency of the compressed air supply.

[0040] According to the second embodiment, the self-contained air conditioning system 100 further comprises a second turbine 32. The second turbine 32 receives air from the fuel cell assembly 16 and expands said air to recover energy. The energy supplied by the second turbine 32 is transmitted to the secondary compressor 30 and provides power to the secondary compressor 30.

[0041] There Fig. 3B schematically illustrates the autonomous 100 air conditioning system according to a third embodiment.

[0042] According to the third embodiment, the self-contained air conditioning system 100 comprises the secondary compressor 30 and the second turbine 32 described previously in relation to the Fig. 3A and further includes a second motor 31 and a second motor control unit 311 for controlling the second motor 31. The second motor 31 transmits mechanical energy to the secondary compressor 30, which is added to the energy transmitted by the second turbine 32. This makes it possible to obtain sufficient energy supply to the secondary compressor 30 to obtain an air pressure suitable for the operation of the fuel cell assembly 16 when the energy recovery enabled by the second turbine 32 is not sufficient.

[0043] The second engine 31 and the second engine control unit 311 are electrically powered by the electrical circuit 20, in other words by electricity supplied by the fuel cell assembly 16. The second engine 31 and the second engine control unit 311 therefore do not require electrical power from the pre-existing electrical network of the aircraft 1.

[0044] The self-contained air conditioning system 100, according to the second and third embodiments, may further include a third heat exchanger (not shown) for transferring heat from the air exiting the fuel cell assembly 16 to the compressed air entering the fuel cell assembly, thereby preheating the air entering the fuel cell assembly. The third heat exchanger is therefore located on an air inlet duct of the fuel cell assembly 16, downstream of the secondary compressor 30, and on an air outlet duct of the fuel cell assembly 16, upstream of the second turbine 32.

[0045] There Fig. 4 schematically illustrates a controller 40 of the autonomous air conditioning system 100 and other elements of the autonomous air conditioning system 100.

[0046] The controller 40 controls elements of the autonomous air conditioning system 100, known as active elements, by transmitting control instructions via communication links shown on the Fig. 4 by continuous arrows. The broken lines represent on the Fig. 4 electrical connections.

[0047] The active elements controlled by the controller 40 perform functions necessary for the operation of the autonomous air conditioning system 100, such as air compression, fluid flow management, thermal management of fluids or devices, and air humidity management. The active elements thus allow for the variation of parameters such as the flow rate, pressure, and temperature of the compressed air. According to an embodiment shown in Fig. 4 , the controller 40 controls the second air sampling device 9, the first motor control unit 111, the second motor control unit 311 when it exists, the valve 171, the fuel cell assembly 16 comprising air and hydrogen flow control valves.

[0048] Instructions sent by the controller 40 to the first motor control unit 111 allow, for example, the power or speed of the motor to be adjusted, in order to vary the pressure and temperature of compressed air at the outlet of the first compressor 10.

[0049] Instructions sent by the controller 40 to the second air sampling device 9 allow, for example, the incoming air flow rate to be modified, in order to vary the temperature of the heat transfer fluid and to vary the temperature of the compressed air at the outlet of the first heat exchanger 13.

[0050] Instructions sent by controller 40 to valve 171 allow the compressed air flow rate to be adjusted at the inlet of cabin 17.

[0051] Instructions sent by the controller 40 to the second motor control unit 311 allow, for example, the power or speed of the second motor 31 to be adjusted, in order to vary the pressure and temperature of compressed air entering the fuel cell assembly 16.

[0052] Instructions sent by the controller 40 to the fuel cell assembly 16 allow, for example, the air flow entering the fuel cell assembly 16 and / or the hydrogen flow entering the fuel cell assembly 16 to be modified, for example via valves (not shown).

[0053] The controller 40 is also capable of implementing a regulation algorithm for one or more predefined parameters such as the pressure and temperature of compressed air injected into the cabin 17, the pressure and temperature of compressed air injected into the fuel cell assembly 16, the flow rate of compressed air injected into the cabin 17, the flow rate of compressed air injected into the fuel cell assembly 16 or the electrical power supplied by the fuel cell assembly 16. For this, the controller 40 receives information from sensors, such as pressure, temperature or flow sensors located for example on air lines at the inlet of the cabin 17 and at the inlet of the fuel cell assembly 16 or electrical power sensors.The implementation of a regulation algorithm by the controller 40 involves processing data from said sensors and sending control instructions to the active elements of the autonomous air conditioning system 100.

[0054] The controller 40 is electrically powered by the fuel cell assembly 16. The electrical circuit 20 includes a voltage converter 41 which provides the controller 40 with a low voltage direct current, for example 28V.

[0055] According to one embodiment, the electrical circuit 20 further includes a switch 46. The switch 46 can electrically connect the electrical circuit 20 connected to the fuel cell assembly 16, either to a first electrical assembly 201 supplying the autonomous air conditioning system 100, or to a second electrical assembly 420 supplying priority electrical loads 423. The first electrical assembly 201 includes electrical connections providing power to the first and second motor control units 111, 311, the first and second motors 11, 31, the controller 40 and may further include electrical connections providing power to valves, for example valve 171.

[0056] The second electrical assembly 420 supplies power to the priority electrical loads 423. A converter 422 is used to obtain alternating current at a voltage suitable for these priority electrical loads 423. The priority electrical loads 423 are external devices to the autonomous air conditioning system 100 and manage safety functions, thus ensuring the safety of the aircraft 1 and its passengers. For example, the priority electrical loads 423 are devices used to pilot the aircraft 1 or to control the aircraft 1's altitude.

[0057] Switch 46 is controlled by a control unit (not shown). When an emergency situation is detected, for example upon receiving an alarm, the control unit sends a switching instruction to switch 46 to shut off the power supply to the autonomous air conditioning system 100 and to supply power to the priority electrical loads 423. Conversely, when the control unit detects the end of an emergency situation, it sends a switching instruction to switch 46 to shut off the power supply to the priority electrical loads 423 and to restore power to the autonomous air conditioning system 100.

[0058] Thus, the fuel cell assembly 16 of the autonomous air conditioning system 100 can be used as an emergency power source. Furthermore, this emergency power source can be available within a very short time corresponding to the switching time, for example, less than one second, since the fuel cell assembly 16 is already operating when an emergency situation is detected by the control unit of the switch 46.

[0059] According to one embodiment, the aircraft 1 comprises two self-contained air conditioning systems 100, each with a switch 46, and a control unit common to both switches 46. When an emergency situation is detected, the common control unit maintains power to the air conditioning functions of one of the two self-contained air conditioning systems 100 and sends a switching instruction to the switch 46 of the other self-contained air conditioning system 100 to supply power to the priority electrical loads 423. Thus, it is possible to ensure the safety functions of the priority electrical loads 423 while simultaneously providing air conditioning to the cabin 17.

[0060] There Fig. 5schematically illustrates an example of the hardware architecture of the controller 40. The controller 40 then comprises, connected by a communication bus 510: a processor or CPU (“Central Processing Unit”) 501; a RAM (“Random Access Memory”) 502; a ROM (“Read Only Memory”) 503; a storage unit or a storage media reader, such as a HDD (“Hard Disk Drive”) 504; and an interface 505 allowing communication with the active elements of the autonomous air conditioning system 100 and with sensors installed in the autonomous air conditioning system 100.

[0061] The processor 501 is capable of executing instructions loaded into RAM 502 from ROM 503, external memory (not shown), storage media, or a communication network. When controller 40 is powered on, the processor 501 can read instructions from RAM 502 and execute them. These instructions form a computer program, causing the processor 501 to implement all or part of the algorithms and steps described here in relation to controller 40.

[0062] Thus, all or part of the algorithms and steps described here in relation to controller 40 can be implemented in software form by executing a set of instructions by a programmable machine, such as a DSP (Digital Signal Processor) or a microcontroller, or in hardware form by a dedicated machine or component, such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit). In general, therefore, controller 40 includes electronic circuitry adapted and configured to implement the algorithms and steps described here in relation to controller 40.

Claims

1. Autonomous air-conditioning system (100) for an aircraft (1), comprising: - a primary compressor (10) compressing air bled from outside the aircraft (1) and supplying compressed air, a first part of said compressed air being injected into a cabin (17) of the aircraft so as to condition the air in the cabin (17) in terms of pressure and temperature, - a first electric motor (11) supplying mechanical energy to the primary compressor (10), the system (100) further comprising a fuel cell stack (16) supplied with air from a second part of the compressed air supplied by the primary compressor (10), the fuel cell stack (16) supplying electrical power to the first electric motor (10), the system (100) being characterized in that it further comprises a closed cooling circuit (18) in which a heat transfer fluid circulates, the cooling circuit (18) being arranged to cool the fuel cell stack (16) and the first electric motor (11) and being furthermore arranged to allow exchange of heat between air bled from outside the aircraft (1) and the heat transfer fluid so as to cool the heat transfer fluid.

2. System (100) according to Claim 1, further comprising a first heat exchanger (13) effecting an exchange of heat between the compressed air supplied by the primary compressor (10) and air bled from outside the aircraft (1), the first heat exchanger (13) being located downstream of the primary compressor (10) and upstream of the fuel cell stack (16) and of the aircraft cabin (17).

3. System (100) according to Claim 2, wherein the primary compressor (10) is further supplied with mechanical energy by a first turbine (12), the first turbine (12) receiving at its inlet a third part of the compressed air supplied by the primary compressor (10) and being located downstream of the first heat exchanger (13).

4. System (100) according to any one of Claims 1 to 3, further comprising a secondary compressor (30), the secondary compressor (30) being located between the primary compressor (10) and the fuel cell stack (16) and compressing the second part of the compressed air supplied by the primary compressor (10).

5. System (100) according to the preceding claim, wherein the secondary compressor (30) is supplied with mechanical energy by a second turbine (32), the second turbine (32) receiving at its inlet compressed air coming from the fuel cell stack (16).

6. System (100) according to the preceding claim, further comprising a second electric motor (31) electrically powered by the electrical energy provided by the fuel cell stack (16), the second electric motor (31) providing mechanical energy to the secondary compressor (30).

7. System (100) according to any one of Claims 1 to 6, further comprising a controller (40) configured to implement a control algorithm for regulating compressed-air temperature, pressure and flow-rate parameters and configured to send control commands to active elements (9, 111, 311, 171, 16) of the system providing compressed-air temperature, pressure and flow-rate control functions.

8. System (100) according to any one of Claims 1 to 7 further comprising a switch (46) configured to connect to the fuel cell stack (16), electrically and alternately, a first electrical assembly (201) and a second electrical assembly (401), the first electrical assembly (201) being arranged to supply electrical power to the system (100), the second electrical assembly (401) being arranged to supply electrical power to equipment (423) external to the system and performing safety functions in the aircraft.

9. Aircraft (1) comprising at least one autonomous air-conditioning system (100) according to any one of Claims 1 to 8.