Non-propulsive turbomachine for a fuel conditioning system to supply an aircraft propulsion turboshaft engine and associated method

Abstract

A non-propulsive turbomachine (2) for an aircraft fuel conditioning system (Q) comprising: a first compressor (21) configured to supply a cabin air conditioning device (6) with a first pressurized airflow (A1p) via a circulation channel (31); a second compressor (22); a combustion chamber (23) configured to be supplied by a supply airflow (A) circulating in a supply channel (32) connecting to the second compressor (22); a single gas turbine (24) connected to the first compressor (21) and the second compressor (22) by a single turbomachine shaft (25); a bypass channel (33) connected to the circulation channel (31) and the supply channel (32); and a relief valve (4) mounted on the bypass channel (33) and configured to move between: a closed position and an open position, in which part of the first pressurized airflow (A1p) flows in the bypass channel (4).Figure from the summary: Figure 3.

Description

Title of the invention: Non-propulsive turbomachine for a fuel conditioning system to supply an aircraft propulsion turboshaft engine and associated method. Technical field

[0001] The present invention relates to the field of aircraft comprising propulsion systems powered by fuel stored in a cryogenic tank.

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, The invention relates to propulsion systems powered by fuel stored in a cryogenic tank.

[0007] It is known to store fuel, particularly hydrogen, in liquid form to limit the size and mass of aircraft tanks. For example, fuel is stored at a temperature of approximately -253 to -251°C (20 to 22 Kelvins) in a cryogenic tank on the aircraft.

[0008] In order to be injected into the combustion chamber of a turbomachine for example, the fuel must be conditioned, i.e. pressurized and heated, in order to allow optimal combustion.

[0009] In practice, the heating stage is energy-intensive and requires extracting heat from hot sources. Among the various technologies for heating liquid fuel, with reference to [Fig. 1], it is known to generate a heating gas flow AC by means of a non-propulsive turbomachine 102 supplied, on the one hand, by fuel Q from a cryogenic tank R and, on the other hand, by an airflow A. A non-propulsive turbomachine is a turbomachine that does not contribute to the aircraft's thrust. For this purpose, the non-propulsive turbomachine 102 comprises, successively, along the direction of airflow A, a compressor 121 comprising one or more stages, a combustion chamber 122, and a turbine 123 comprising one or more stages.During operation of the non-propulsive turbomachine 102, the compressor 121 compresses an incoming air stream A, which mixes with the fuel stream Q in the combustion chamber 122 to generate the heating gas stream AC. This generates mechanical energy via the turbine 123, which can drive the compressor 121 via a mechanical shaft 124. A heat exchanger 101 transfers heat from the heating gas stream AC to the liquid fuel stream Q, thus converting it to a gaseous state. The fuel stream Q is then ready for use in a combustion chamber CC of the aircraft engine M.

[0010] The non-propulsive turbomachine 102 is also connected to an electrical generator 103 configured to supply an electrical network of the aircraft. The non-propulsive turbomachine 102 thus generates electrical energy to power equipment of the aircraft.

[0011] In a known architecture, in order to optimize the aircraft's mass and limit the number of components, the non-propulsive turbomachine 102 is also connected to a cabin air conditioning system 104 (known to those skilled in the art by its English acronym "ECS" for "Environment Control System") to supply it with pressurized air. In practice, a pressurized airflow Ap is taken from the outlet of the compressor 121 of the non-propulsive turbomachine 102 and supplies the air conditioning system 104. The non-propulsive turbomachine 102 thus advantageously generates a flow of heating gas AC to heat the fuel Q, to generate electrical power to power various equipment and to provide a pressurized airflow Ap to the cabin air conditioning device 104.

[0012] However, to fulfill these three functions, such a non-propulsive turbomachine 102, generally with two shafts, is complex and significantly increases the mass and size of the conditioning system in which it is mounted.

[0013] In particular, to supply the air conditioning unit 104, the compressed air flow Ap must have a predefined pressure. Therefore, in this design, the compressor 121 is sized to generate a compressed air flow Ap at the expected pressure. In practice, the incoming air pressure varies depending on the aircraft's altitude, being higher at low altitudes than at high altitudes. Since the compressor 121 is sized to ensure that the expected pressure value is achieved regardless of the aircraft's altitude, it is designed at high altitudes, resulting in over-compression of the airflow at low altitudes. Such over-compression can lead to compressor surge, which can damage the non-propulsive turbomachine.

[0014] An immediate solution to reduce the risk of pumping would be to reduce the rotational speed of the mechanical shaft. However, to heat the fuel flow and / or power the electrical equipment, the non-propulsive turbomachine must generate a calibrated flow of heating gas, which requires a predetermined rotational speed. In other words, prior art non-propulsive turbomachines do not allow for an acceptable compromise to optimally fulfill all the aforementioned functions.

[0015] The invention thus aims to eliminate at least some of these drawbacks by providing a non-propulsive turbomachine that can simultaneously supply a fuel heating gas flow, electrical power to supply various aircraft equipment, and a pressurized air flow to supply a cabin air conditioning system, while having an optimized architecture. The invention particularly relates to a non-propulsive turbomachine whose operation is optimal and simplified, regardless of the air pressure entering the compression stage. PRESENTATION OF THE INVENTION

[0016] The invention relates to a non-propulsive turbomachine for a fuel conditioning system configured to supply an aircraft turboshaft engine with fuel from a cryogenic tank, the non-propulsive turbomachine comprising: • a first compressor configured to be supplied by a first ambient airflow and to generate a first pressurized airflow, the first pressurized airflow being configured at least in part to supply an aircraft cabin air conditioning device via a circulation channel, • a second compressor configured to be powered by a second ambient air stream and to generate a second pressurized air stream, • a combustion chamber configured to be supplied, on the one hand, by a fuel flow from the cryogenic tank, and, on the other hand, by a supply air flow circulating in a supply channel connecting the second compressor to the combustion chamber, the supply air flow comprising at least the second pressurized air flow, the combustion chamber being configured to generate a heat-laden exhaust gas flow, • a single gas turbine connected to both the first and second compressors by a single turbomachine shaft, the gas turbine being configured to be driven in rotation by the exhaust gas flow from the combustion chamber, and to drive both the first and second compressors simultaneously, • a bypass channel connected, on the one hand, to the circulation channel of the first pressurized air flow and, on the other hand, to the combustion chamber supply channel, and • a discharge valve mounted on the bypass channel, the discharge valve being configured to operate at least between: • a closed position in which the entire first pressurized airflow is configured to circulate within the circulation channel, so as to supply only the cabin air conditioning unit, and • an open position, in which part of the first pressurized airflow is configured to flow through the bypass channel, so as to increase the flow rate of the first airflow and lower the pressure difference between the inlet and outlet of the first compressor.

[0017] The non-propulsive turbomachine according to the invention makes it possible to supply the aircraft's cabin air conditioning system regardless of the pressure of the first pressurized airflow exiting the first compressor. When the pressure is too high, the relief valve is placed in the open position. Thus, the flow rate of the first airflow passing through the first compressor can advantageously increase, thereby reducing the pressure difference between the inlet and outlet of the first compressor. The risk of surge is advantageously limited and the long-term reliability of the non-propulsive turbomachine is ensured. Thus, at low altitudes, for example, when the first airflow passing through the first compressor (whose dimensions are predetermined) has a higher pressure, diverting a portion of the airflow makes it possible to increase the flow rate through the first compressor while supplying the air conditioning system with an airflow at the expected pressure.

[0018] The bypass channel associated with the discharge valve allows the non-propulsive turbomachine to fulfill at least one dual function by generating a flow of exhaust gas charged with heat (intended for example to heat the fuel flow from the cryogenic tank) and by supplying in parallel the cabin air conditioning device, while maintaining a limited footprint.

[0019] According to one aspect, the relief valve is configured to operate through a plurality of partially open positions between the closed and open positions, so as to adapt the flow rate of the first air stream. The pressure difference between the inlet and outlet of the first compressor is advantageously reduced adaptively as a function of the pressure of the first incoming air stream, and therefore of the first pressurized air stream. Thus, depending on the aircraft's altitude, for example, the flow rate of the first pressurized air stream is advantageously and continuously adjusted to supply the cabin air conditioning system with an air stream at optimal pressure.

[0020] In one embodiment, the relief valve is a control valve configured to operate at least between the open and closed positions depending on a pressure difference in the first airflow between an inlet and an outlet of the relief valve. When the pressure of the first airflow is too high at the outlet of the first compressor (corresponding to over-compression of the first compressor), the relief valve is thus configured to open under the effect of the pressure so as to discharge a portion of the first airflow. The relief valve is therefore said to be "passive".

[0021] According to one aspect, the discharge valve is in the form of a flap mounted in the bypass channel and comprising a return spring, configured to place the discharge valve by default in the closed position.

[0022] Alternatively, the non-propulsive turbomachine includes a control system for the wastegate valve. The control system comprises a device for measuring the pressure at the outlet of the first compressor and / or the aircraft altitude, and a computer connected to the measuring device and the wastegate valve and configured to control the wastegate valve based on the measured pressure and / or the determined altitude. Thus, when the pressure at the outlet of the first compressor is too high, the wastegate valve is advantageously controlled to increase The flow rate of the first air stream is reduced, and the pressure difference between the inlet and outlet of the first compressor is lowered. In other words, an excessive rise in pressure at the outlet of the first compressor is automatically detected, and any risk of damage to the non-propulsive turbomachine is eliminated.

[0023] In one embodiment, the measuring device is a pressure sensor mounted directly at the outlet of the first compressor, the computer being configured to receive a measurement from the measuring device and to control the discharge valve at least: • in the open position when the pressure measured by the measuring device is greater than or equal to a first predetermined pressure threshold, • in the closed position when the pressure measured by the measuring device is less than a second predetermined pressure threshold, less than or equal to the first predetermined pressure threshold.

[0024] This allows, by adding a simple sensor, to control the discharge valve directly according to the pressure of the first pressurized air flow at the outlet of the first compressor and to avoid any risk of over-compression which could lead to a risk of pumping.

[0025] In an alternative embodiment, the measuring device is an altimeter, the computer being configured to receive a measurement from the measuring device and to control the discharge valve at least: • in the open position when the altitude determined by the measuring device is below a first predetermined altitude threshold, so as to increase the flow rate of the first airflow circulating in the first compressor, • in the closed position when the altitude determined by the measuring device is greater than or equal to a second predetermined altitude threshold, greater than or equal to the first predetermined altitude threshold.

[0026] This allows the relief valve to be controlled directly based on the aircraft's altitude, which affects the pressure of the air entering the first compressor and therefore the pressure of the first pressurized airflow. Thus, the non-propulsive turbomachine increases the flow rate of the first airflow at low altitudes and closes the relief valve at high altitudes when it is no longer needed. Preferably, the measuring device is directly integrated with the altimeter mounted in the aircraft's cockpit and used by the pilots, thereby eliminating the need for additional equipment.

[0027] According to a preferred aspect, the non-propulsive turbomachine includes a heat exchanger configured to reheat the fuel stream using calories transferred from the exhaust gas stream of the gas turbine. The heat exchanger allows to convert the fuel stream into a gaseous state so that it can be injected into the combustion chamber of the propulsion turbomachine. The non-propulsive turbomachine then generates a heat-laden exhaust gas stream to warm the fuel stream from the cryogenic tank and to power the cabin air conditioning system, thus reducing the size of the air conditioning system in which the non-propulsive turbomachine is mounted.

[0028] Preferably, the non-propulsive turbomachine includes an electric generator connected to the turbomachine shaft and configured to generate electrical power to supply the aircraft's electrical system. The non-propulsive turbomachine thus fulfills a triple function: supplying compressed air to the cabin air conditioning system, generating an exhaust gas flow to preheat the fuel flow, and generating electrical power, which contributes to the aircraft's decarbonization. Furthermore, when the relief valve is opened and a portion of the initial pressurized airflow is directed to the combustion chamber of the non-propulsive turbomachine, this initial pressurized airflow generates greater mechanical power and therefore a greater amount of electrical energy.

[0029] The invention also relates to a fuel conditioning system configured to supply at least one aircraft propulsion turboshaft engine, the conditioning system comprising: • a cryogenic reservoir, • a fuel circuit connected to the cryogenic tank and configured to be connected to the propulsion turboshaft engine, a fuel flow circulating in the fuel circuit, and • a non-propulsive turbomachine as described above, and • the cryogenic tank being configured to supply both the propulsive turbomachine and the combustion chamber of the non-propulsive turbomachine.

[0030] According to one aspect, the heat exchanger is mounted on the fuel circuit so as to heat the fuel stream from the cryogenic tank. The fuel stream is thus heated by the heat transferred from the exhaust gas stream of the non-propulsive turbomachine.

[0031] In one embodiment, the heat exchanger is configured to heat the fuel stream directly from the exhaust gas stream.

[0032] Alternatively, the heat exchanger is configured to heat the fuel stream indirectly from the exhaust gas stream, via a heat transfer fluid.

[0033] The invention also relates to an aircraft comprising at least one propulsion turboshaft engine and a conditioning system as described above, the fuel circulating in the fuel circuit supplying the propulsion turboshaft engine.

[0034] Finally, the invention relates to a method of operating the non-propulsive turbomachine as described above, the method comprising the steps of: • circulate an initial flow of air through the first compressor to supply at least one cabin air conditioning unit, • circulate a second airflow through the second compressor to supply the combustion chamber of the non-propulsive turbomachine, and • control the discharge valve so as to circulate part of the first airflow into the supply channel and increase the flow rate of the first airflow circulating in the first compressor. PRESENTATION OF THE FIGURES

[0035] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0036] Fig. 1 is a schematic representation of a conditioning system comprising a prior art non-propulsive turbomachine.

[0037] Figure 2 is a schematic representation of a conditioning system comprising a non-propulsive turbomachine according to a first embodiment of the invention.

[0038] Fig. 3 is a close-up view of the non-propulsive turbomachine of Fig. 2.

[0039] Figure 4 is a schematic representation of a conditioning system including a non-propulsive turbomachine according to a second embodiment of the invention.

[0040] It should be noted that the figures set out the invention in detail to implement the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0041] The invention relates to a non-propulsive turbomachine for an aircraft fuel SC conditioning system.

[0042] With reference to [Fig. 2], a fuel conditioning system SC is shown, configured to supply one or more aircraft engines, in particular a turboprop engine M, with fuel Q from a cryogenic tank. R. It goes without saying that the aircraft could include more than one cryogenic tank R, the conditioning system SC being thus connected to each cryogenic tank R.

[0043] The propulsion turboshaft engine M is configured to provide propulsion for the aircraft (i.e. thrust), in particular, by driving at least one propulsion element (not shown).

[0044] In this example, the fuel Q is dihydrogen, but the invention applies to other types of fuel, in particular fuels such as methane or liquefied natural gas.

[0045] In practice, the fuel Q is stored in the cryogenic tank R at cryogenic temperatures. For example, the fuel Q is stored in the cryogenic tank R at a temperature of approximately -253 to -251°C (20 to 22 Kelvin). At this temperature, the fuel Q is liquid. In order to be introduced into a combustion chamber of the propulsion turboshaft engine M, the fuel Q must be heated.

[0046] For this purpose, the aircraft includes an SC conditioning system configured to heat and pressurize the Q fuel.

[0047] Still referring to [Fig.2], the conditioning system SC includes a fuel circuit 1 (represented by closely spaced dashed lines) connected at the inlet to the cryogenic tank R and at the outlet to the combustion chamber of the propulsion turboshaft engine M. In this example, the conditioning system SC also includes a mechanical pump P, preferably high pressure, configured to circulate a fuel flow Q from upstream to downstream in the fuel circuit 1.

[0048] According to one aspect, the SC conditioning system comprises a non-propulsive turbomachine 2 configured to supply a cabin air conditioning system 6 of the aircraft. The non-propulsive turbomachine 2 does not provide thrust for the aircraft and does not have a propulsion component. In practice, the non-propulsive turbomachine 2 is preferably also configured to both supply the energy requirements of the various aircraft equipment (e.g., air conditioning, power supply for flight control or entertainment systems, etc.) and generate a heat-laden gas stream configured to warm the fuel stream Q, as will be described in more detail later.

[0049] With reference to figures 2 and 3, the non-propulsive turbomachine 2 comprises a first compressor 21, a second compressor 22 and a single gas turbine 24 connected together by a single turbomachine shaft 25.

[0050] The first compressor 21 is configured to be supplied by a first ambient airflow Al, from an air intake external to the aircraft, and to generate a first pressurized airflow Alp. The first pressurized airflow Alp is configured at least in part to supply the aircraft cabin air conditioning system 6 via a circulation channel 31 shown in [Fig.3].

[0051] According to one aspect, the first compressor 21 is sized so that the first pressurized airflow Alp has a predetermined pressure to supply the cabin air conditioning unit 6. In this example, the predetermined pressure is between 2 and 4 bar (between 2 x 10⁵ and 4 x 10⁵ Pa). In particular, the first compressor 21 is sized to achieve the predetermined pressure value of the first pressurized airflow Alp when the pressure of the first airflow Al (at the inlet of the first compressor 21) is on the order of 0.2 bar (2 x 10⁴ Pa), corresponding to atmospheric air pressure when the aircraft is at high altitude, i.e., approximately 12,000 m (40,000 ft), corresponding to the average cruising altitude of an aircraft.

[0052] In this example, the first compressor 21 has a compression ratio of approximately 9 to 15, corresponding to the compression ratio required to achieve 2 to 4 bar (2 x 10⁵ to 4 x 10⁵ Pa) from an airflow at a pressure of approximately 0.2 bar (2 x 10⁴ Pa). Preferably, the first compressor 21 comprises two centrifugal compression stages to achieve such a compression ratio, but it is understood that the number of stages could be different. The first compressor 21 could alternatively comprise an assembly of axial compressors / rectifiers and / or centrifugal compressors.

[0053] The second compressor 22 is configured to be supplied by a second ambient airflow A2, from an external air inlet of the aircraft, and to generate a second pressurized airflow A2p. The second pressurized airflow A2p is configured to supply a combustion chamber 23 of the non-propulsive turbomachine 2 via a supply channel 32 shown in [Fig. 3].

[0054] According to one aspect, the second compressor 22 is sized to supply the combustion chamber 23 with a second pressurized airflow A2p having a pressure between 0.75 and 4 bar (7.5 x 0.4 and 4 x 0.4 Pa). In this example, the second compressor 22 has a compression ratio of approximately 3 to 4. In this example, the second compressor 22 comprises a single centrifugal compression stage to enable it to achieve the compression ratio defined above. It is understood that the second compressor 22 could alternatively comprise an assembly of axial compressors / rectifiers.

[0055] With further reference to [Fig. 3], the combustion chamber 23 is configured to be supplied, on the one hand, by a fuel flow Q from the cryogenic tank R, and, on the other hand, by a supply air flow A circulating in the supply channel 32 connecting the second compressor 22 to the combustion chamber. 23. In other words, the cryogenic tank R supplies in parallel the propulsion turbomachine M, with a first fuel flow Q1, and the combustion chamber 23 of the non-propulsive turbomachine 2 with a second fuel flow Q2.

[0056] The supply airflow A of the combustion chamber 23 comprises at least the second pressurized airflow A2p. In practice, according to one aspect of the invention, the supply airflow A may also comprise a portion of the first pressurized airflow Alp, as will be described in more detail later. With reference to [Fig. 3], the combustion chamber 23 is configured to generate a heat-laden exhaust gas flow AE.

[0057] As described previously, the non-propulsive turbomachine 2 comprises a single gas turbine 24 connected to both the first compressor 21 and the second compressor 22 by a single turbomachine shaft 25. The gas turbine 24 is configured to be driven in rotation by the exhaust gas flow AE from the combustion chamber 23, and to simultaneously drive in rotation the first compressor 21 and the second compressor 22. Such a non-propulsive turbomachine 2, having a single turbomachine shaft 25 to connect the first compressor 21, the second compressor 22 and the single gas turbine 24, is advantageously simpler, lighter and more compact.

[0058] In a preferred embodiment, with reference to [Fig. 2], the non-propulsive turbomachine 2 includes a heat exchanger 7 configured to heat the first fuel stream Ql circulating in the fuel circuit 1 using calories transferred by the exhaust gas stream AE circulating in the gas turbine 24. The exhaust gas stream AE thus vaporizes the first fuel stream Ql before its injection into the combustion chamber of the propulsion turbomachine M. In one embodiment, the heat exchanger 7 is mounted on the fuel circuit 1. Alternatively (not shown), the conditioning system SC includes a heat transfer fluid circuit mounted between the exhaust gas stream AE and the fuel circuit 1, so as to heat the fuel stream Q indirectly.This allows the use of a non-reactive heat transfer fluid and avoids the risk of contact between an oxidizing fluid and the fuel flow Q in the event of a failure of the heat exchanger 7 for example.

[0059] In practice, with reference to [Fig.4], the heat exchanger 7 is preferably configured to heat both the first fuel flow Q1 supplying the combustion chamber of the propulsion turbomachine M and the second fuel flow Q2 supplying the combustion chamber 23 of the non-propulsive turbomachine 2. A single heat exchanger 7 thus allows the fuel flow Q to be brought to a gaseous state before it separates to supply in parallel the propulsion turbomachine M and the non-propulsive turbomachine 2.

[0060] In a preferred embodiment, the non-propulsive turbomachine 2 includes an electric generator 8 connected to the turbomachine shaft 25 and configured to generate electrical power to supply an aircraft electrical system. The electric generator 8 can, for example, power the aircraft's equipment when it is on the ground.

[0061] The non-propulsive turbomachine 2 is thus configured both to generate an exhaust gas flow AE to heat the fuel flow Q from the cryogenic tank R, electrical energy via the electric generator 8 to power an electrical network of the aircraft, and a compressed air flow Alp to power the cabin air conditioning device 6 of the aircraft.

[0062] For this purpose, according to one aspect of the invention, with reference to [Fig.3], the non-propulsive turbomachine 2 comprises a bypass channel 33 and a discharge valve 4.

[0063] The bypass channel 33 is connected, on the one hand, to the circulation channel 31 of the first pressurized airflow Alp and, on the other hand, to the supply channel 32 of the combustion chamber 23. The bypass channel 33 is thus configured to divert a part of the first pressurized airflow Alp from the first compressor 21 and to convey it to the combustion chamber 23 of the non-propulsive turbomachine 2.

[0064] The discharge valve 4 is mounted on the bypass channel 33 and is configured to operate at least between: • an open position PI (shown in Figures 2 and 3) in which part of the first pressurized airflow Alp flows through the bypass channel 33 towards the combustion chamber 23, and • a closed position PO (represented in [Fig.4]) in which the entire first pressurized airflow Alp flows through the circulation channel 31, up to the cabin air conditioning device 6.

[0065] In practice, the discharge valve 4 is preferably a control valve configured to evolve according to a plurality of partially open positions between the open position PI (corresponding to a complete opening of the discharge valve 4), and the closed position PO, so as to adapt the flow rate of the first pressurized air stream Alp according to the pressure of the first air stream Al circulating in the first compressor 21, as will be described in more detail later.

[0066] Thus, when the discharge valve 4 is in the open position PI, the first pressurized airflow Alp circulates partly in the circulation channel 31 to the cabin air conditioning device 6, and partly in the bypass channel 33. This makes it possible to increase the flow rate of the first airflow Al and thus to lower the pressure difference between the inlet and outlet of the first compressor 21. The risks of pumping of the first compressor 21 are advantageously limited.

[0067] In one embodiment, the relief valve 4 is a passive device configured to move through a plurality of partially open positions between the open position PI and the closed position PO, depending on the pressure difference between an inlet and an outlet of the relief valve 4. Thus, when the first pressurized airflow is over-compressed and its pressure is too high at the outlet of the first compressor 21, the pressure at the inlet of the relief valve 4 is greater than the outlet pressure, and the relief valve 4 opens, thereby increasing the flow rate of the first pressurized airflow Alp. The relief valve 4 is then, for example, a flap mounted in the bypass channel 33 and hinged by means of a spring to allow (depending on different cross-sections of airflow) or prevent the passage of the first pressurized airflow Alp.The spring allows the discharge valve 4 to be placed by default in the closed position PO.

[0068] In an alternative embodiment, with reference to [Fig.3], in order to control the opening and closing of the discharge valve 4, the non-propulsive turbomachine 2 includes a control system 5 connected electrically (by wire or wireless means) to the discharge valve 4.

[0069] In practice, the control system 5 comprises a measuring device 50 for the pressure at the outlet of the first compressor 21 and / or the aircraft altitude, and a computer 9, configured to receive a measurement from the measuring device 50 and to control the relief valve 4 according to the measured pressure or altitude. For this purpose, the computer 9 is connected, in this example, by a data network, on the one hand to the measuring device 50, and, on the other hand, to the relief valve 4.

[0070] In a first embodiment, shown in [Fig. 3], the measuring device 50 is a pressure sensor mounted directly at the outlet of the first compressor 21. The computer 9 is then configured to receive a pressure measurement from the measuring device 50 and to control at least the relief valve 4: • in the open position PI when the pressure measured by the measuring device 50 is greater than or equal to a first predetermined pressure threshold, and • in the closed position PO when the pressure measured by the measuring device 50 is less than a second predetermined pressure threshold, the second predetermined pressure threshold being less than or equal to the first predetermined pressure threshold.

[0071] In practice, in this example, the calculator 9 is configured to control, for example, a percentage of opening of the discharge valve 4 as a function of the measured pressure, so as to adapt the flow rate of the first pressurized airflow Alp.

[0072] Thus, if the pressure at the outlet of the first compressor 21 is too high, the relief valve 4 is opened, thereby increasing the flow rate and thus reducing the pressure. Any risk of over-compression and therefore of pumping is advantageously eliminated. In this example, the first predetermined pressure threshold is in the range of 3.75 to 5.5 bar (3.75 x 10⁵ to 5.5 x 10⁵ Pa). Similarly, in this example, the second predetermined pressure threshold is in the range of 2.5 to 4 bar (2.5 x 10⁵ to 4 x 10⁵ Pa). In this example, when the pressure of the first pressurized air flow Alp at the outlet of the first compressor 21 is between the first and second pressure thresholds, the relief valve 4 is preferably partially open. In practice, in this example, the computer 9 is configured to determine a percentage opening of the relief valve 4 as a function of the measured pressure.

[0073] In a second embodiment (not shown), the measuring device 50 is an altimeter mounted on the aircraft in the vicinity or not of the non-propulsive turbomachine 2. The altimeter could alternatively correspond to an altimeter already mounted in the cockpit of the aircraft to allow piloting the aircraft.

[0074] The computer 9 is then configured to receive an altitude measurement from the measuring device 50 and to control the discharge valve 4 at least: • in the open position PI when the altitude determined by the measuring device 50 is below a first predetermined altitude threshold, and • in the closed position PO when the altitude determined by the measuring device 50 is greater than or equal to a second predetermined altitude threshold, greater than or equal to the first predetermined altitude threshold.

[0075] In practice, in this example, the computer 9 is configured to control, for example, a percentage of opening of the relief valve 4 as a function of the aircraft's attitude, so as to adapt the flow rate of the first pressurized air stream Alp. Thus, regardless of the aircraft's attitude and therefore the pressure of the air stream entering the first compressor 21, the pressure of the air stream supplying the cabin air conditioning unit 6 is adapted and optimal.

[0076] In this example, the first predetermined altitude threshold is on the order of 1000. In other words, at low altitude (for example when the aircraft is on the ground), the opening of the discharge valve 4 allows the flow rate of the first air stream Al to increase in order to ensure that a limit pressure is not exceeded at the outlet of the first compressor 21 despite its compression ratio being sized at high altitude so that the first pressurized air stream Alp reaches 2 to 4 bar (between 2xl05 and 4xl05 Pa) in the cabin air conditioning device 6.

[0077] Similarly, in this example, the second predetermined altitude threshold is between 6000 and 8500m. In other words, at high altitude, the pressure of the first airflow Al entering the first compressor 21 allows the first pressurized airflow Alp to have the expected pressure at the outlet of the first compressor 21 in the cabin air conditioning device 6. At this altitude, the relief valve 4 is therefore configured to be closed, since it is no longer necessary to increase the flow rate of the first airflow Al.

[0078] When the measured altitude is between the first predetermined altitude threshold and the second predetermined altitude threshold, the relief valve 4 is preferably partially open. In practice, in this example, the computer 9 is configured to determine a percentage opening of the relief valve 4 as a function of the measured altitude, so as to adjust the flow rate of the first air stream Al passing through the first compressor 21 and thus adjust its pressure at the outlet of the first compressor 21.

[0079] In one embodiment, the non-propulsive turbomachine 2 includes a control valve (not shown) mounted on the circulation channel 31 and configured to regulate the flow of the first pressurized air stream Alp, so as to ensure that it reaches the expected pressure at the inlet of the cabin air conditioning device 6.

[0080] The non-propulsive turbomachine 2 according to the invention makes it possible to supply the cabin air conditioning device 6 with a first pressurized airflow Alp from the first compressor 21 at the expected pressure regardless of the aircraft's altitude.

[0081] A method of operating the non-propulsive turbomachine 2 will now be described with reference to Figures 2 to 4. In this example, the non-propulsive turbomachine 2 comprises an electric generator 8 connected to the turbomachine shaft 25 and a heat exchanger 7 mounted on the fuel circuit 1. The non-propulsive turbomachine 2 includes a pressure sensor-type measuring device 50 mounted on the circulation channel 31 at the outlet of the first compressor 21. It is understood that the method operates analogously for an altimeter-type measuring device 50. The relief valve 4 is initially in the closed position PO and no airflow circulates in the bypass channel 33, as shown in [Fig. 4].

[0082] The aircraft is initially at a low altitude, for example on the ground, before takeoff. The non-propulsive turbomachine 2 is activated and a first airflow A1 is introduced into the first compressor 21, while a second airflow A2 is introduced in parallel into the second compressor 22. From the outlet of the first compressor 21, a first pressurized airflow A1 flows through the circulation channel 31 to the cabin air conditioning unit 6 to supply it. From the outlet of the second compressor 22, a second pressurized airflow A2p flows in the supply channel 32 to the combustion chamber 23 to supply it with air.

[0083] In a first step El, the measuring device 50, of the pressure sensor type, measures a pressure value of the first pressurized airflow Alp at the outlet of the first compressor 21. The measuring device 50 then sends this measurement to the computer 9, which compares it with a first predetermined pressure threshold. In this example, the first predetermined pressure threshold is between 3.75 and 5.5 bar (3.75 x 0.5 to 5.5 x 0.5 Pa), corresponding to the pressure of the first pressurized airflow Alp exiting the first compressor 21 for a first incoming airflow Al at a pressure between 0.9 and 1 bar (corresponding to the air pressure between 0 and 1000 m altitude). Because of the low altitude of the aircraft, and therefore the inlet pressure of the first airflow Al associated with the predetermined compression ratio of the first compressor 21, the computer 9 detects that the measured pressure is higher than the first predetermined pressure threshold.

[0084] The computer 9 then commands, in a second step E2, the positioning of the discharge valve 4 in the open position PI, so as to allow the circulation of a portion of the first pressurized airflow Alp in the bypass channel 33, as shown in [Fig. 3]. The flow rate of the first airflow Al circulating in the first compressor 21 is then increased and the pressure difference between the inlet and outlet of the first compressor 21 is lowered.

[0085] In a third stage E3, the first pressurized airflow Alp is divided at the outlet of the first compressor 21 into: • a portion circulating in the bypass channel 33 to join the feed channel 32 of the combustion chamber 23 of the non-propulsive turbomachine 2, in which it mixes with the second pressurized air stream A2p from the second compressor 22, and • a portion circulating in the circulation channel 31 to supply the cabin air conditioning device 6.

[0086] The computer 9 controls the opening of the discharge valve 4, so as to control the flow of the first pressurized air flow Alp to ensure that the expected pressure is reached at the inlet of the cabin air conditioning device 6, in this example 2 to 4 bar (between 2x105 and 4x105 Pa).

[0087] The combustion chamber 23 then generates an exhaust gas flow AE which drives the gas turbine 24 into rotation, driving the turbomachine shaft 25 and the two compressors 21, 22.

[0088] In a fourth stage E4, with reference to [Fig. 4], the exhaust gases AE pass through the heat exchanger 7, in which they exchange heat with the Fuel flow Q circulating in fuel circuit 1. When heated and in a gaseous state, the first fuel flow Q1 feeds the combustion chamber of the propulsion turbomachine M and the second fuel flow Q2 feeds the combustion chamber 23 of the non-propulsive turbomachine 2. In parallel, the turbomachine shaft 25 drives the electric generator 8 to generate electrical power and supply an electrical network of the aircraft.

[0089] The non-propulsive turbomachine 2 is thus advantageously capable of generating a flow of heat-laden gas to warm the fuel flow Q from a cryogenic tank R, electrical energy to power a plurality of aircraft equipment and an air flow at the optimal pressure to power the aircraft cabin air conditioning system 6.

[0090] When the aircraft takes off and the altitude increases, the air pressure at the inlet of the first compressor 21 decreases, as does the pressure at the outlet.

[0091] The measuring device 50, of the pressure sensor type, preferably measures recurrently the pressure of the first pressurized airflow Alp at the outlet of the first compressor 21 and sends the measurement to the computer 9 which compares it, in this example, with the first predetermined pressure threshold and the second predetermined pressure threshold.

[0092] Preferably, the computer 9 controls the relief valve 4 so as to close it progressively to obtain an airflow at the expected pressure to supply the cabin air conditioning unit 6 during the aircraft's climb, regardless of the altitude. In this example, the partially open position of the relief valve 4 is modified and adapted to the pressure of the first incoming airflow A1, when the aircraft is at an altitude between 1000 m and 8000 m.

[0093] In a fifth step E5, when the measured pressure is below the second predetermined pressure threshold, the risk of over-compression is eliminated and the computer 9 controls the relief valve 4, so as to position it in the closed position PO. The circulation of the first pressurized air flow Alp in the bypass channel 33 is then stopped.

[0094] At high altitude, the first compressor 21 supplies only the cabin air conditioning device 6 and the second compressor 22 supplies only the combustion chamber 23, so as to generate the exhaust gas flow AE to drive the gas turbine 34 into rotation and heat the fuel flow Q in the heat exchanger 7.

[0095] Advantageously, the non-propulsive turbomachine according to the invention makes it possible to fulfill the functions of supplying air to the cabin air conditioning system, generating electrical power and heating the fuel flow. regardless of the aircraft's altitude and without risking the occurrence of a pumping phenomenon in the compressors.

Claims

1. Demands Non-propulsive turbomachine (2) for a fuel conditioning system (SC) (Q) configured to supply an aircraft turboshaft engine (M) with fuel (Q) from a cryogenic tank (R), the non-propulsive turbomachine (2) comprising: • a first compressor (21) configured to be supplied by a first ambient airflow (Al) and to generate a first pressurized airflow (Alp), the first pressurized airflow (Alp) being configured at least in part to supply a cabin air conditioning device (6) of the aircraft via a circulation channel (31), • a second compressor (22) configured to be supplied by a second ambient air stream (A2) and to generate a second pressurized air stream (A2p), • a combustion chamber (23) configured to be supplied, on the one hand, by a fuel stream (Q2) from the cryogenic tank (R), and, on the other hand, by a feed air stream (A) circulating in a feed channel (32) connecting the second compressor (22) to the combustion chamber (23), the feed air stream (A) comprising at least the second pressurized air stream (A2p), the combustion chamber (23) being configured to generate a heat-laden exhaust gas stream (AE), • a single gas turbine (24) connected to both the first compressor (21) and the second compressor (22) by a single turbomachine shaft (25), the gas turbine (24) being configured to be driven in rotation by the exhaust gas flow (AE) from the combustion chamber (23), and to drive simultaneously the first compressor (21) and the second compressor (22), • a bypass channel (33) connected, on the one hand, to the circulation channel (31) of the first pressurized air flow (Alp) and, on the other hand, to the supply channel (32) of the combustion chamber (23), and • a relief valve (4) mounted on the bypass channel (33), the relief valve (4) being configured to move at least between: • a closed position (PO) in which the entire first pressurized airflow (Alp) is configured to flow in the circulation channel (31), so as to supply only the cabin air conditioning device (6), and • an open position (PI), in which part of the first pressurized airflow (Alp) is configured to flow in the bypass channel (4), so as to increase the flow rate of the first airflow (Al) and lower the pressure difference between the inlet and outlet of the first compressor (21).

2. Non-propulsive turbomachine (2) according to claim 1, wherein the discharge valve (4) is configured to move through a plurality of partially open positions between the closed position (PO) and the open position (PI), so as to adapt the flow rate of the first air stream (Al).

3. Non-propulsive turbomachine (2) according to any one of claims 1 to 2, wherein the discharge valve (4) is a control valve configured to move at least between the open position (PI) and the closed position (PO) as a function of a pressure difference of the first airflow (Al) between an inlet and an outlet of the discharge valve (4).

4. Non-propulsive turbomachine (2) according to any one of claims 1 to 3, wherein the non-propulsive turbomachine (2) comprises a control system (5) for the discharge valve (4), the control system (5) comprising a measuring device (50) for the pressure at the outlet of the first compressor (21) and / or the altitude of the aircraft, and a computer (9) connected to the measuring device (50) and to the discharge valve (4) and configured to control the discharge valve (4) according to the measured pressure and / or the determined altitude.

5. Non-propulsive turbomachine (2) according to claim 4, wherein the measuring device (50) is a pressure sensor mounted directly at the outlet of the first compressor (21), the computer (9) being configured to receive a measurement from the measuring device (50) and to control the discharge valve (4) at least: • in the open position (PI) when the pressure measured by the measuring device (50) is greater than or equal to a first predetermined pressure threshold, • in the closed position (PO) when the pressure measured by the measuring device (50) is less than a second predetermined pressure threshold, less than or equal to the first predetermined pressure threshold.

6. Non-propulsive turbomachine (2) according to claim 4, wherein the measuring device (50) is an altimeter, the computer (9) being configured to receive a measurement from the measuring device (50) and to control the discharge valve (4) at least: • in the open position (PI) when the altitude determined by the measuring device (50) is less than a first predetermined altitude threshold, so as to increase the flow rate of the first air stream (Al) circulating in the first compressor (21), • in the closed position (PO) when the altitude determined by the measuring device (50) is greater than or equal to a second predetermined altitude threshold, greater than or equal to the first predetermined altitude threshold.

7. Non-propulsive turbomachine (2) according to any one of claims 1 to 6, wherein the non-propulsive turbomachine (2) comprises a heat exchanger (7) configured to reheat the fuel stream (Q) from calories transferred by the exhaust gas stream (AE) of the gas turbine (24).

8. Non-propulsive turbomachine (2) according to any one of claims 1 to 7, wherein the non-propulsive turbomachine (2) comprises an electric generator (8) connected to the turbomachine shaft (25) and configured to generate electrical power to supply an aircraft electrical network.

9. Fuel conditioning system (SC) configured to supply at least one aircraft propulsion turboshaft engine (M), the conditioning system (SC) comprising: • a cryogenic tank (R), • a fuel circuit (1) connected to the cryogenic tank (R) and configured to be connected to the propulsion turboshaft engine (M), a fuel flow (Q) circulating in the fuel circuit (1), and • a non-propulsive turbomachine (2) according to any one of claims 1 to 8, • the cryogenic tank (R) being configured to supply both the propulsion turboshaft engine (M) and the combustion chamber (23) of the non-propulsive turbomachine (2).

10. Conditioning system (SC) according to claim 9 combined with claim 7, wherein the heat exchanger (7) is mounted on the fuel circuit (1) so as to warm the fuel stream (Q) from the cryogenic tank (R).

11. Aircraft comprising at least one propulsion turboshaft engine (M) and a conditioning system (SC) according to any one of claims 9 to 10, the fuel (Q) circulating in the fuel circuit (1) supplying the propulsion turboshaft engine (M).

12. A method of operating the non-propulsive turbomachine (2) according to any one of claims 1 to 8, the method comprising the steps of: • circulating a first airflow (A1) in the first compressor (21) to supply at least one cabin air conditioning device (6), • circulating a second airflow (A2) in the second compressor (22) to supply the combustion chamber (23) of the non-propulsive turbomachine (2), and • controlling the discharge valve (4) so ​​as to circulate a portion of the first airflow (A1) in the supply channel (33) and increase the flow rate of the first airflow (A1) circulating in the first compressor (21).

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