Improved propulsion assembly for multi-engine aircraft

Abstract

A propulsion assembly (100) for an aircraft, in particular a multi-engine helicopter, comprising: at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; a main air circulation device (30) configured to drain air from the first engine (1) via a first drain channel (310) and / or from the second engine (2) via a second drain channel (320) to deliver air to the apparatus of the propulsion assembly (100); and a secondary air circulation device (40) configured to discharge air from the other of the first or second engines (1, 2) that is not operating in the standby mode when the first or second engines (1, 2) are operating in the standby mode, and to deliver the air to the one of the first or second engines (1, 2) that is operating in the standby mode.

Description

Technical Field

[0001] The present invention relates to the field of aircraft comprising at least two engines, such as turboshaft engines or turboprop engines, and for flying machines such as helicopters or twin-engine aircraft. In particular, the present invention relates to the thermal management of components of a propulsion assembly for a multi-engine, in particular twin-engine aircraft, and to a method for thermal management of such a propulsion assembly. Background Art

[0002] Most helicopters comprise two or more turbine engines, each comprising a gas turbine, the turbine engines being, for example, turboshaft engines or turboprop engines. This is particularly the case with twin-engine or multi-engine helicopters. Such aircraft allow operation in an economical mode known as "ECO" mode. ECO mode is an operating mode of a twin-engine architecture, generally corresponding to the cruise flight phase, in which one of the gas turbines is in standby mode, i.e. stopped (combustion chamber stopped or "off", able to drive the gas generator at a certain speed via an electric motor) or operating at an ultra-low idle speed (combustion chamber ignited or "on") at a very low speed, for example a speed lower than 40% of the nominal speed, while the other gas turbine provides the full power supply.

[0003] This mode allows to optimize the specific fuel consumption, which decreases with the power provided by the turbine engines. In fact, the specific fuel consumption of the turbine decreases with the power supplied, preferably with one turbine providing 100% of the power instead of each turbine providing 50% of the power. Document FR2967133A1 describes an example of the application of the ECO mode on a twin-engine helicopter.

[0004] However, depending on the operating climate conditions, the ECO mode may lead to conditions that favor the formation of ice in the air flow of an engine operating in standby mode (i.e. stopped or spinning at very low idle speed). Such an engine cannot feed itself to provide ice protection, and the temperature of its own parts or components can no longer prevent the appearance of ice. In addition, during operation in the ECO mode, when one of the two engines is stopped (combustion chamber "off"), the combustion chamber temperature of this engine will not allow a normal or rapid restart when necessary.

[0005] In twin-engine helicopters there are devices for circulating hot air, allowing to bleed hot air from one or both engines, coming from different positions in the hot air flow of these engines. To this end, these devices comprise, for each engine, a bleed passage having: a solenoid valve (or "shutoff valve", "SOV"), allowing to activate or deactivate the bleed of the engine in question; and a non-return valve, which serves to prevent the air from recirculating to the engine, thus preventing the transfer of air between the two engines.

[0006] Such hot air extraction is particularly suitable for pressurization or air conditioning. However, existing hot air circulation devices do not allow managing the above-mentioned problems, such as ice accumulation associated with the heating of components of an engine operating in standby mode. Therefore, a solution is needed that at least partially addresses the above-mentioned drawbacks. Summary of the invention

[0007] The present disclosure relates to a propulsion assembly for an aircraft, in particular a multi-engine helicopter, comprising: - at least one first engine and a second engine, configured to operate in at least one standby mode; - a main air circulation device configured to draw air from the first engine via a first draw channel and / or from the second engine via a second draw channel in order to convey the air to the device of the propulsion assembly; and - A secondary air circulation device configured to, when one of the first engine or the second engine is operating in at least one standby mode, bleed air from the other of the first engine or the second engine that is not operating in the standby mode, and deliver the air to the first engine or the second engine operating in the standby mode.

[0008] "Standby mode" refers to a mode in which the combustion chamber of the gas turbine of one of the engines is shut down, or the engine is running at an ultra-low idle speed. When it is running at an ultra-low idle speed, the combustion chamber is ignited and the rotating parts of the gas turbine rotate at a speed lower than 40% of the nominal speed. Therefore, it is understood that when the first engine is in standby mode, the second engine is not in standby mode but provides full power to the aircraft, and vice versa.

[0009] In the present disclosure, the terms "upstream" and "downstream" are considered according to the normal direction of the air flow in the different channels defined below. For example, in the first and second channels defined below, the "upstream-downstream" direction corresponds to the direction of travel from the launch point on the first engine or the second engine to the device of the propulsion assembly. Similarly, in the third channel defined below, the "upstream-downstream" direction corresponds to the direction of travel toward the injection point of the first engine or the second engine.

[0010] The main air circulation device is configured to introduce the air in the first engine and / or the second engine, that is, introduce the hot air of these engines, for example, flowing in the air flow at the combustion chamber. For this reason, the first engine is equipped with a first introduction channel, and the second engine is equipped with a second introduction channel.

[0011] Then, the first channel and the second channel can merge at the same time as the downstream channel merges, and the downstream channel can deliver the air discharged by the first engine and / or the second engine to the equipment of the propulsion assembly. Therefore, it can be understood that the amount of air delivered to the equipment via the downstream channel is the sum of the amount of air discharged from each of the first engine and the second engine.

[0012] The propulsion assembly equipment to which the air delivered from the main air cycle device is directed may be a pressurization device, an air conditioner, a part of the propulsion assembly to be cooled, a wing or a flap of the aircraft.

[0013] In addition to the main air circulation device, the propulsion assembly also includes a secondary air circulation device. Unlike the main device, this secondary device allows hot air flowing in the flow stream of one of the two engines to be transferred to the air flow stream of the other of the two engines. In other words, the secondary air circulation device allows air to be bleeded in the started engine (for example, the first engine), that is, the engine is not running in standby mode and providing full power, and to convey the bleed air to the engine running in standby mode (for example, the second engine).

[0014] Thus, when conditions are detected during cruising flight that could lead to ice formation on certain parts of the engine operating in standby mode, the hot air available in the started engine can be used by means of the secondary air circulation device, thereby limiting the formation of ice in the engine in standby mode. In addition, the injection of hot air into the combustion chamber of the engine operating in standby mode also makes it possible to keep said combustion chamber at a higher temperature, thereby making it easier and faster to start the engine when necessary, for example in the event of a malfunction of the started engine.

[0015] In some embodiments, the first discharge channel and the second discharge channel are configured to discharge from the first engine and the second engine at first discharge points of the first engine and the second engine, respectively, and the secondary air circulation device includes a third discharge channel, which is configured to discharge air from one of the first engine or the second engine at the second discharge point of the first engine or the second engine, and transport the air to an injection point of the other of the first engine or the second engine that is different from the first discharge point.

[0016] It should be noted that in the configuration of a twin-engine aircraft equipped with a hot air circulation device, the engines may be equipped with dual launch bosses. Therefore, the first launch point of each of the first engine and the second engine may be one of the two launch bosses. Similarly, the second launch point different from the first launch point and the injection point of the third launch point may be located on the other of the two launch bosses, respectively.

[0017] In other words, according to this embodiment, the secondary air circulation device is different from the primary air circulation device, and the second discharge point of the third discharge channel in one of the two engines and the injection point of the third discharge channel in the other of the two engines are different and preferably at a certain distance from the first discharge point of the primary air circulation device. Therefore, the hot air provided by the started engine can be used to limit the formation of ice in the engine in standby mode without modifying the existing primary air circulation device.

[0018] In certain embodiments, air is delivered to at least one injection point of a first engine or a second engine operating in standby mode, the injection point being located on a component of the engine, the component being one of a compressor, a combustion chamber, an inlet guide vane (or IGV), or an air intake.

[0019] In some embodiments, the first engine and the second engine include a compressor, and the second discharge point is arranged at the outlet of the compressor or between two stages of the compressor. The second discharge point can be positioned according to the required flow rate and / or air temperature.

[0020] In certain embodiments, the injection points are arranged to inject air into an intake of the first engine or the second engine, between stages of the compressor, or into a combustion chamber.

[0021] In certain embodiments, the third discharge passage includes a solenoid valve and a check valve.

[0022] The solenoid valve can be controlled by the control unit, allowing the air discharge in the started engine to be activated or deactivated. In addition, the non-return valve arranged downstream of the solenoid valve provides non-recirculation of air and prevents air from being delivered from the engine that has left the standby mode to the started engine. It can also be understood that this configuration is asymmetric and that only air delivery from the first engine (for example) to the second engine can occur, but not in the reverse direction. In other words, only the second engine is intended to run in standby mode. This configuration allows simplifying the start-up of the secondary air circulation device, requiring only the addition of a solenoid valve / non-return valve pair.

[0023] In certain embodiments, the secondary air circulation device includes a bypass device disposed on one of the first discharge passage or the second discharge passage.

[0024] According to this embodiment, the secondary air circulation device does not differ from the primary air circulation device, but is modified by the addition of a bypass device. Therefore, unlike the previously defined architecture, in this specific case, each engine does not need to include a double air discharge boss, since in the engine operating in standby mode, the discharge and injection of air can be done in the same position as in the primary circulation device. Alternatively, one of the two bosses can be blocked.

[0025] This allows obtaining the technical effects previously mentioned, in particular those relating to the anti-icing of engine components operating in standby mode, while simplifying the overall architecture of the propulsion assembly and in particular limiting the volumes involved in the air circulation device.

[0026] In certain embodiments, the bypass device is configured to allow air originating from one of the first engine or the second engine not operating in the standby mode to flow to the other of the first engine or the second engine operating in the standby mode while preventing air from flowing in the opposite direction.

[0027] In other words, the bypass device is configured to allow air to flow from the started engine to the engine running in the standby mode when necessary, and to prevent air from flowing in the opposite direction, that is, to the started engine when such flow occurs, especially when the engine running in the standby mode leaves the standby mode and returns to the nominal operating mode. Therefore, although the bypass device is arranged on the main circulation device, outside the ECO mode, air can be vented from both engines through the main circulation device, and in the ECO mode, air can be delivered from the started engine to the engine in the standby mode through the secondary circulation device.

[0028] In some embodiments, the first discharge channel and the second discharge channel include a solenoid valve and a check valve, and the bypass device includes a bypass channel having a solenoid valve, the first end of the bypass channel is connected to the first discharge channel or the second discharge channel downstream of the check valve of the first discharge channel or the second discharge channel.

[0029] It is understood that the first end of the bypass channel is connected to the first bypass channel (for example) downstream of the check valve, and the check valve itself is downstream of the solenoid valve of the first bypass channel in the air flow direction in the first bypass channel. Therefore, considering the presence of the check valve, air can flow to the first engine in standby mode only via the first lead-out channel, but can also flow to the first engine in standby mode via the bypass channel by opening the solenoid valve of the bypass channel.

[0030] In certain embodiments, the second end of the bypass channel is in communication with the first drain channel or the second drain channel between the solenoid valve and the check valve of the first drain channel or the second drain channel.

[0031] This configuration allows bypassing the check valve of the first drain passage (for example). Thus, via the solenoid valves opening the bypass passage and the first drain passage, respectively, air can flow from the started engine (the second engine in this example) via the bypass passage and then via the first drain passage to the engine in standby mode (the first engine in this example).

[0032] In certain embodiments, the first discharge channel and the second discharge channel are configured to discharge air from the first engine and the second engine at discharge points of the first engine and the second engine, respectively, and the bypass channel includes a check valve, which is installed opposite to the check valve of the first discharge channel or the second discharge channel, and the second end of the bypass channel is connected to the first discharge channel or the second discharge channel between the solenoid valve and the discharge point of the first discharge channel or the second discharge channel.

[0033] "Reverse installation" means that when air flows from the engine in standby mode in a first flow direction, it can flow in the first discharge passage (for example), but cannot flow in the bypass passage due to the presence of the check valve. Conversely, when air flows to the engine in standby mode in a second flow direction opposite to the first direction, it can flow in the bypass passage due to the presence of the check valve, but cannot flow in the first discharge passage.

[0034] Furthermore, the first end is connected to the first discharge channel (for example) between the solenoid valve and the discharge point of the first discharge channel, so that in ECO mode, air from the started engine can be injected into the engine in standby mode at the same point (discharge point) where air is discharged outside the ECO mode. This allows limiting modifications to the engine, thereby simplifying the architecture of the propulsion assembly.

[0035] In certain embodiments, the first discharge passage and the second discharge passage are configured to discharge air from the first engine and the second engine at discharge points of the first engine and the second engine, respectively, the bypass passage includes a check valve installed opposite to the check valve of the first discharge passage or the second discharge passage, and the second end of the bypass passage is configured to inject air into the first engine or the second engine operating in the standby mode at an injection point different from the discharge point.

[0036] The fact of arranging the second end of the discharge channel at an injection point of the engine in standby mode different from the discharge point, rather than on the first bypass channel (for example), allows free selection of the injection point depending on the area or engine component to be heated.

[0037] In certain embodiments, the bypass passage includes a restrictor disposed between the check valve and the injection point, the restrictor configured to adjust a flow rate of air flowing in the bypass passage.

[0038] The restrictor may be arranged downstream of the non-return valve of the bypass channel and may be an adjustable constriction of the bypass channel which allows the air flow injected into the engine in standby mode to be adjusted depending on the temperature of the zone or engine component to be heated. The restrictor may also be controlled by the control unit.

[0039] In some embodiments, the first discharge channel and the second discharge channel include a three-way valve and a check valve, the bypass device includes a bypass channel, the first end of the bypass channel is connected to the first discharge channel or the second discharge channel downstream of the check valve of the first discharge channel or the second discharge channel, the second end of the bypass channel is connected to the three-way valve, the three-way valve can move between a first position and a second position, the first position allows air to flow in the first discharge channel or the second discharge channel, but prevents air from flowing in the bypass channel, and the second position prevents air from flowing in the first discharge channel or the second discharge channel, but allows air to flow in the bypass channel.

[0040] The three-way valve can be controlled by the control unit and switched from the first position to the second position in the ECO mode. This configuration allows the structure of the bypass channel to be simplified without the need for a solenoid valve, requiring only a single valve (three-way valve).

[0041] In some embodiments, the first discharge channel and the second discharge channel include solenoid valves, and the bypass device includes a movable check valve arranged on the first discharge channel or the second discharge channel, and the movable check valve is movable between a first position and a second position, the first position allows air to flow in the first discharge channel or the second discharge channel along a first circulation direction, while preventing air from flowing in a second circulation direction opposite to the first direction, and the second position allows air to flow in the second circulation direction, while preventing air from flowing in the first circulation direction.

[0042] The movable check valve can be controlled by the control unit so as to pivot from the first position to the second position by itself in the ECO mode and outside the ECO mode. More precisely, outside the ECO mode, air can be discharged from the first engine (for example) while flowing in the first discharge channel, the movable check valve is in the first position, preventing air from returning to the engine. Conversely, in the ECO mode, the movable check valve is arranged in the second position so as to allow air from the started second engine to flow to the first engine in the standby mode, the second position also preventing air from returning to the second engine.

[0043] This configuration allows to dispense with the use of a bypass channel, thus further simplifying the architecture of the propulsion assembly. In this respect, it will be appreciated that, in ECO mode, the flow from the started engine to the engine in standby mode is allowed by the pressure difference existing between these engines and by the movable non-return valve arranged in its second position, and furthermore, the solenoid valve is open.

[0044] In some embodiments, the first discharge channel and the second discharge channel include solenoid valves, and the bypass device includes a blockable check valve arranged on the first discharge channel or the second discharge channel, and the blockable check valve is configured to be blocked in an open position, allowing air to flow in two circulation directions.

[0045] The blockable non-return valve can be controlled by the control unit so as to be blocked in an open position, thereby allowing air to flow in both circulation directions. More precisely, outside the ECO mode, air can be flowed in the first discharge channel while being discharged from the first engine (for example), the blockable non-return valve preventing air from returning to the engine. Conversely, in the ECO mode, the blockable non-return valve is blocked in an open position to allow air originating from the started second engine to flow to the first engine in standby mode.

[0046] In this particular case, flow from the started engine to the engine in standby mode is allowed in ECO mode by the pressure difference existing between these engines and the check valve blocked in the open position. This configuration allows the use of a pilot channel to be omitted, thus further simplifying the architecture of the propulsion assembly.

[0047] The present disclosure also relates to an aircraft, comprising a propulsion assembly according to any one of the aforementioned embodiments, wherein the aircraft is a multi-engine, in particular a twin-engine helicopter.

[0048] The present disclosure also relates to a thermal management method of a propulsion assembly according to any of the aforementioned embodiments, comprising: - detecting that one of the first engine or the second engine is operating in at least one standby mode; - measuring the temperature of at least one component of the first engine or the second engine operating in standby mode; and - If the measured temperature is less than or equal to a predetermined threshold, air is bled from the other of the first engine or the second engine that is not operating in the standby mode by means of the secondary air circulation device and delivered to the first engine or the second engine that is operating in the standby mode.

[0049] ECO mode means that one of the first engine or the second engine is in standby mode. Ice conditions may then occur in this engine. In order to detect such conditions, temperature sensors such as thermocouples may be arranged in the engine in standby mode, in particular on (one or more) components of the engine, or in the combustion chamber. These sensors may be connected to a control unit which determines whether at least one of these sensors registers a temperature below or equal to a predetermined threshold value, for example indicating the possibility of ice occurrence. In this case, the control unit commands the opening of the solenoid valve, or the three-way valve, or the movable check valve, or even the blockable check valve of the secondary air circulation device to allow air to flow from the started engine to the engine in standby mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention and its advantages will be better understood by reading the following detailed description of different embodiments of the invention given by way of non-limiting examples. This description makes reference to the attached pages of the drawings in which:

[0051] [ Figure 1 ] Figure 1 A cross-sectional view showing a propulsion assembly for a twin-engine aircraft according to a first embodiment of the present invention;

[0052] [ Figure 2 ] Figure 2 A cross-sectional view showing a propulsion assembly for a twin-engine aircraft according to a second embodiment of the present invention;

[0053] [ Figure 3 ] Figure 3 A first modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0054] [ Figure 4 ] Figure 4 A second modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0055] [ Figure 5 ] Figure 5 A third modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0056] [ Figure 6 ] Figure 6 A fourth modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0057] [ Figure 7 ] Figure 7 A fifth modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0058] [ Figure 8 ] Figure 8 A sixth modified example according to the second embodiment is shown. Figure 2 An isolated portion of a first discharge passage of a propulsion assembly;

[0059] [ Fig. 9 ] Fig. 9 The different steps of the method for thermal management of a propulsion assembly according to the invention are schematically illustrated. DETAILED DESCRIPTION

[0060] In the continuation of this manual, reference will be made to Figure 1 The architecture of a propulsion assembly 100 according to a first embodiment of the present invention is described.

[0061] Figure 1 A propulsion assembly 100 of a twin-engine aircraft is schematically shown, comprising a first turbine engine 1 and a second turbine engine 2, which drive a transmission member of a helicopter carrying a main propeller or rotor (not shown) in rotation. The turbine engines 1, 2 may be turboshaft engines or turboprop engines, and will be more simply referred to as the first engine 1 and the second engine 2, respectively, in the continuation of this specification. Although the propulsion assembly described in the continuation of this specification comprises two engines, this example is not restrictive, and the present invention is also applicable to the propulsion assembly of a multi-engine aircraft comprising more than two engines.

[0062] The first engine 1 and the second engine 2 are preferably identical and have identical features. Therefore, the following description relates to the first engine 1 and the second engine 2.

[0063] The first engine 1 and the second engine 2 each comprise a gas turbine 10, 20 having a gas generator 12, 22 and a free turbine 11, 21 capable of being driven in rotation by the air flow generated by the gas generator 12, 22. The free turbine 11, 21 is mounted on a shaft 13, 23 which transmits the rotational movement to a receiving member, such as a main rotor of a helicopter (not shown).

[0064] The gas generator 12, 22 comprises a rotating shaft 14, 24 and a combustion chamber 17, 27, on which a compressor 15, 25 and a turbine 16, 26 are mounted, and the combustion chamber 17, 27 is axially arranged between the compressor 15, 25 and the turbine 16, 26, so that the gas generator 12, 22 is considered to be in the axial direction of the rotating shaft 14, 24. The gas turbine 10, 20 has a housing 18, 28 provided with an air inlet 19, 29, through which fresh air enters the gas generator 12, 22. After being introduced into the housing of the gas generator 12, 22, the fresh air is compressed by the compressor 15, 25 and then discharged into the air intake of the combustion chamber 17, 27, where it is mixed with fuel. The combustion occurring in the combustion chamber 17, 27 causes the combustion gases to flow out to the turbine 16, 26 at high speed, which has the effect of driving the shaft 14, 24 of the gas generator 12, 22 in rotation and thus driving the compressor 15, 25 in rotation. The rotation speed of the shaft 14 , 24 of the gas generator 12 , 22 is determined by the flow rate of the fuel entering the combustion chamber 17 , 27 .

[0065] Although the turbines 16, 26 extract kinetic energy, the gas stream leaving the gas generator still has significant kinetic energy. Figure 1As can be appreciated, the gas flow F is directed to the free turbine 11 , 21 , which has the effect of causing the free turbine 11 , 21 to expand, thereby driving the turbine wheel and shaft 13 , 23 in rotation.

[0066] The propulsion assembly 100 also includes a main air circulation device 30, which allows hot air flowing in the air flow of the first engine 1 and / or the second engine 2 to be introduced to convey this hot air to equipment (not shown) of the propulsion assembly 100, which may be a pressurization device, an air conditioner, a part to be cooled of the propulsion assembly, a wing or a flap of the aircraft.

[0067] To this end, the main air circulation device 30 includes a first discharge passage 310 for discharge from the first engine 1 and a second discharge passage 320 for discharge from the second engine 2. Then, the first discharge passage 310 and the second discharge passage 320 merge at a branch, and a downstream passage 330 extends from the branch to the device of the propulsion assembly 100.

[0068] Furthermore, it should be noted that the terms "upstream" and "downstream" are considered along the normal flow direction of the air in the different channels, which flow direction is also determined by Figure 1 and the arrows in the following figures.

[0069] The hot air discharge from the first engine 1 through the first discharge passage 310 occurs at a first discharge point 313 arranged, for example, facing the combustion chamber 17. Similarly, the hot air discharge from the second engine 2 through the second discharge passage 320 occurs at a first discharge point 323 arranged, for example, facing the combustion chamber 27.

[0070] In order to allow such a release, the first passage 310 and the second passage 320 respectively include solenoid valves 311, 321 and check valves 312, 322 arranged downstream of the solenoid valves 311, 321. It should be noted that the solenoid valves 311, 321 and the three-way valves or movable and blockable check valves described in the sequel of this specification can be controlled by a control unit (not shown), which can be a "FADEC (Full Authority Digital Engine Control)".

[0071] Therefore, the solenoid valves 311, 321 can be controlled independently of each other so as to be able to respectively radiate hot air flow rates q1 and q2 from the first engine 1 and / or the second engine 2. Therefore, the total hot air flow rate q flowing to the propulsion assembly device in the downstream channel 330 is t is the sum of the flow rates q1 and q2 flowing in the first discharge channel 310 and the second discharge channel 320, that is, q t =q1+q2.

[0072] Furthermore, this dual engine architecture allows an economical operating mode, referred to in the sequel to this specification as "ECO" mode, in which one of the two engines is operated in standby mode, i.e. stopped (combustion chamber "off") or spinning at an ultra-low idle speed (e.g., less than 40% of nominal speed), while the other engine provides full power. Figure 1 In the first embodiment described, the engine operating in standby mode is the second engine 2, with the first engine 1 providing all the power. However, this example is not limiting; the configuration can be reversed without departing from the scope of the invention.

[0073] During operation in the ECO mode, the solenoid valve 321 of the second engine is closed, so the air flow q2 supplied by the second engine 2 is zero, that is, q2=0, so q t =q1. In this configuration, during cruising flight, it is likely that ice will appear on the components of the second engine 2. Furthermore, the low temperature inside the combustion chamber 27 does not allow easy and quick starting of the second engine 2 when necessary.

[0074] It should be noted that these conditions, referred to as icing flight conditions or the necessity of heating the combustion chamber 27 , can be determined by sensors (not shown), such as thermocouples, arranged in the second engine 2 and connected to the control unit.

[0075] In order to limit the drawbacks associated with these conditions, the propulsion assembly 100 is equipped with secondary air flow means 40 comprising, according to a first embodiment, a third discharge channel 410 connecting the first engine 1 to the second engine 2 .

[0076] Specifically, the third discharge channel 410 is configured to discharge hot air from the first engine 1 via a second discharge point 413 different from the first discharge point 313. The first engine 1 may, for example, include two discharge bosses, the first discharge point 313 is connected to one of the two bosses, and the second discharge point 413 is connected to the other of the two bosses.

[0077] In addition, the third discharge channel 410 is configured to carry hot air and inject the hot air into the second engine 2 via an injection point 414 different from the first discharge point 323 of the second engine 2. For example, the second engine 2 may include two discharge bosses in the same manner as the first engine 1, the first discharge point 323 being connected to one of the two bosses, and the injection point 414 being connected to the other of the two bosses.

[0078] The discharge position of the second discharge point 413 and the injection position of the injection point 414 can be determined according to the requirements of anti-icing or maintaining the temperature of the second engine 2 components, and therefore can also be determined according to the requirements of temperature and / or air flow rate.

[0079] Specifically, the selection of the position of the second discharge point 413 may be determined by considering the optimal value between the energy demand required to heat the second engine 2 in the standby mode and the impact on the performance of the started first engine 1. Therefore, the air discharged from the first engine may occur at the outlet of the compressor 15, between several stages of the compressor 15, or at the combustion chamber 17. In addition, as Figure 1 As shown, the air can be injected into the second engine 2 via an air circuit present in the pre-rotation blades, between the stages of the compressor 25 , or around the combustion chamber 27 via its casing, at the air inlet 29 .

[0080] In order to allow the air flow rate q1' to be transmitted from the first engine 1 to the second engine 2, the third discharge passage 410 is equipped with a solenoid valve 411, and a check valve 412 is equipped downstream of the solenoid valve 411, and the check valve is located in the flow direction of the air in the third passage 410 from the first engine 1 to the second engine 2, as shown in FIG. Figure 1 Therefore, in the ECO mode, when the main air circulation device 30 supplies air at a flow rate q t =q1, the started first engine 1 supplies a total air flow rate q1+q1′ distributed between the primary air flow device 30 and the secondary air flow device 40.

[0081] It should be noted that in standby mode, the amount of air directed and injected into the second engine 2 by the secondary air circulation device 40 may depend on external conditions and / or icing conditions and / or thermal conditions of the second engine 2; or other parameters may be related to the need to optimize the air flow. The flow rate may be managed via the angular position of the solenoid valve 411 controlled by the control unit.

[0082] In the continuation of this manual, reference will be made to Figures 2 to 8 The architecture of a propulsion assembly 100 according to a second embodiment of the present invention is described. The features associated with the first engine 1 and the second engine 2 are the same as those of the first embodiment and will not be repeated.

[0083] According to the second embodiment, the secondary air circulation device 40 is arranged on the main air circulation device 30, which involves modification of the main air circulation device. However, it should be noted that the main air circulation device 30 according to the second embodiment further includes a first discharge passage 310, a second discharge passage 320 and a downstream passage 330. The first discharge points 313 and 323 may also be the same as those in the first embodiment.

[0084] In the second embodiment, the engine running in the standby mode is the first engine 1, and the second engine 2 provides all the power. However, this example is not restrictive, and the configuration can be interchanged without departing from the scope of the present invention. In this regard, it is understood that the second discharge channel 320 is the same as the first embodiment, and specifically includes a solenoid valve 321 and a check valve 322 located downstream of the solenoid valve 321.

[0085] According to the following reference Figures 2 to 8 In the application example of the second embodiment described, the secondary air circulation device 40 includes a bypass device, which can be arranged on the first discharge channel 30, involving a modification of the first discharge channel 30 relative to the first embodiment, or including a bypass channel attached to the first discharge channel 30, but without modifying the first discharge channel 30 relative to the first embodiment.

[0086] exist Figure 2 In the first example shown, the bypass device of the secondary air circulation device 40 includes a bypass channel 410 arranged in parallel with the first discharge channel 310, and the bypass channel 410 is connected to the reference Figure 1 The first discharge channel 310 described is identical, and in particular comprises a solenoid valve 311 and a check valve 312 located downstream of the solenoid valve 311 .

[0087] The bypass channel 410 extends between a first end 410a and a second end 410b, the first end 410a is communicated with the first discharge channel 310 downstream of the check valve 312, and the second end 410b is communicated with the first discharge channel 310 between the solenoid valve 311 and the first discharge point 313. The bypass channel 410 further includes a solenoid valve 411 and a check valve 412, and the check valve 412 is arranged downstream of the solenoid valve 411 according to the air flow direction between the first end 410a and the second end 410b.

[0088] The check valve 312 of the first discharge channel 310 and the check valve 412 of the bypass channel 410 are installed opposite to each other. Therefore, the check valve 412 of the bypass channel 410 prevents air from flowing from the first discharge point 313 to the downstream channel 330. In other words, the air discharged from the first discharge point 313 can only flow to the downstream channel via the first bypass channel 310. Similarly, the check valve 312 of the first discharge channel 310 prevents air from flowing from the second end 2 to the first engine 1. In other words, the air from the second engine 2 can only flow to the first engine via the bypass channel 410.

[0089] Therefore, when the control unit detects an icing flight condition, the control unit controls the electromagnetic valve 411 of the bypass channel 410 to open, and preferably also controls the electromagnetic valve 311 of the first discharge channel 310 to close. Considering the pressure difference between the started second engine 2 and the first engine 1 in the standby mode, a part of the air discharged from the second engine 2 by the first end 323 is deflected toward the first engine 1 by means of the bypass channel 410, and the other part flows in the downstream channel 330. In addition, the second end 410b of the bypass channel 410 leads to the first discharge channel 310 between the electromagnetic valve 311 and the first discharge point, and the air from the second engine 2 is injected into the first engine 1 through the first discharge point 313.

[0090] Therefore, in Figure 2 In the ECO mode shown, the total air velocity flowing in the downstream passage 330 is equal to q t =q2-q1'. It should be noted that outside the ECO mode, the solenoid valve 411 is closed and the solenoid valve 311 is open, so q1'=0, q t =q1+q2.

[0091] Figures 3 to 8 1 and 2 show modified examples of the second embodiment. In these figures, in order to simplify the description of these examples, only the first discharge passage 310 and the bypass passage 410 are shown when such passages exist. However, although not shown, other elements of the propulsion assembly 100 (particularly the second discharge passage 320 and the downstream passage 330) are also present and are similar to those described above with reference to Figure 2 The description given is the same.

[0092] Figure 3 Examples and references shown Figure 2 The example described differs in that the second end 410b of the bypass channel 410 is not in communication with the first discharge channel 310, but leads directly to the first engine 1 by means of an injection point 414 different from the first discharge point 313. Thus, according to this example, the air originating from the second engine 2 is not injected into the first engine 1 by the same discharge point in the first engine, namely the first discharge point 313, but is injected into the first engine 1 by means of an injection point 414 different from the first discharge point 313.

[0093] Figure 4 Examples and references shown Figure 3The example described differs in that the bypass channel 410 comprises a restriction 415 arranged downstream of the non-return valve 412, more precisely between the non-return valve 412 and the injection point 414. The restriction 415 may be an adjustable constriction of the passage cross section of the bypass channel 415, which allows adjusting the air flow rate injected into the first engine 1 according to the required flow rate and the temperature of the area or component to be heated. The restriction 415 may also be controlled by the control unit.

[0094] Figure 5 Examples and references shown Figure 2 and Figure 3 The difference of the described example is that the second end 410b of the bypass channel 410 is connected to the first discharge channel 310 between the solenoid valve 311 and the check valve 312. In addition, the bypass channel 410 only includes one solenoid valve 411, and no check valve. According to this configuration, by opening the solenoid valve 311 and the solenoid valve 411 to allow air to be delivered from the second engine 2 to the first engine 1, the bypass channel 410 acts as a bridge (or "bypass"), allowing the check valve 312 of the first discharge channel 310 to be bypassed.

[0095] according to Figure 6 In the example shown, the solenoid valve 311 of the first discharge channel 310 is replaced by a three-way valve 311', and the three-way valve 311' is in the first position ( Figure 6 The left picture in the figure) and the second position ( Figure 4 The first position allows air to flow in the first discharge channel 310 and prevents air from flowing in the bypass channel 410, and the second position prevents air from flowing in the first discharge channel 310 and allows air to flow in the bypass channel 410. In this example, the bypass channel 410 is a simple pipeline without a solenoid valve or a check valve. In addition, the three-way valve is also preferably controlled by the control unit.

[0096] Therefore, outside the ECO mode, the three-way valve 311' is placed in its first position to allow the air flow rate q1 (q1'=0) from the first discharge point 313. Conversely, in the ECO mode, the three-way valve 311' is placed in its second position to allow the air flow rate q1' (q1=0) from the second engine 2 to the first discharge point 313 of the first engine 1.

[0097] according to Figure 7In the example shown, the bypass device of the secondary air flow device 40 does not include a bypass passage, but includes a movable check valve 412', which is arranged at the position of the check valve 312 of the first discharge passage 310. The movable check valve 412' is movable between a first position and a second position by pivoting itself, the first position allowing air to flow from the first discharge point 313 of the first engine 1 to the downstream passage 330 in the first discharge passage 310, and the second position allowing air to flow from the second engine 2 to the first engine 1. The rotational movement of the movable check valve 412' is as shown in FIG. Figure 7 As shown by the curved arrow in .

[0098] It can also be understood that in the first position, the movable check valve 412' prevents the flow of air to the first discharge point 313, and in the second position, the movable check valve 412' prevents the flow of air from the first discharge point 313 to the downstream passage 330. Therefore, outside the ECO mode, the movable check valve 412' is maintained by the control unit in the first position, while in the ECO mode, the movable check valve 412' is placed by the control unit in the second position to allow air to be transferred from the second engine 2 to the first engine 2, and this transfer is also allowed by the existing pressure difference between these engines.

[0099] Figure 8 Examples and references shown Figure 7 The example described differs in that the movable check valve 412' is replaced by a blockable check valve 412" which is configured to be blocked and maintained in an open position by a control unit. Thus, in ECO mode, the blockable check valve 412" is maintained in an open position by the control unit to allow air to be transferred from the second engine 2 to the first engine 2, furthermore, such transfer being allowed by the existing pressure difference between these engines. On the contrary, outside the ECO mode, the blockable check valve 412" resumes its normal operation and prevents air from returning to the first engine 1.

[0100] Fig. 9 The different steps of the thermal management method of the propulsion assembly 100 are schematically illustrated.

[0101] In a first step (step S100), the control unit detects whether one of the engines is running in standby mode. If it is detected that no engine is running in standby mode, corresponding to operation outside the ECO mode of the propulsion assembly ("N" in step S100), the method returns to step S100.

[0102] If it is detected that one of the engines is operating in standby mode ("N" in step S100), the control unit determines whether the propulsion unit 100 is in icing flight conditions or whether a criterion is met, such as the need to heat the combustion chamber (step S200). To this end, the control unit detects whether at least one of the previously mentioned sensors is measuring a temperature less than or equal to a predetermined threshold. If it is detected that none of these conditions are met, i.e. there is no situation of being in icing flight conditions ("N" in step S200), the method returns to step S100.

[0103] If it is detected that at least one of these conditions is met, which means that icing flight conditions exist ("0" in step S200), the control unit allows air to be transferred from the started engine to the engine running in standby mode (step S300). To this end, the control unit commands the opening or activation of the valves or check valves mentioned previously with reference to the different application examples of the first embodiment or the second embodiment, in particular the solenoid valve 411, the three-way valve 311', the movable check valve 412' or the blockable check valve 412".

[0104] Note that the criterion for requiring heating (step S200) may be based on the internal temperature of the engine in standby mode, just like the temperature of the components; and / or based on the temperature of the oil used to cool the engine, and / or based on a criterion of the time elapsed at a given temperature; or perhaps based on whether it is raining, which is related to the altitude.

[0105] Furthermore, as long as the condition detected at step S200 is true, air priming and delivery from one engine to the other may be maintained (step S300), while taking into account hysteresis to avoid untimely opening and closing.

[0106] Although the present invention has been described with reference to specific exemplary embodiments, it is apparent that these examples can be modified and altered without departing from the overall scope of the present invention as defined in the claims. Specifically, the various features of the different embodiments illustrated / mentioned can be combined into other embodiments. Therefore, this specification and the drawings should be considered in an illustrative rather than a restrictive sense.

[0107] It is also self-evident that all features described with reference to a method can be converted, individually or in combination, into a device and conversely, all features described with reference to a device can be converted, individually or in combination, into a method.

Claims

1. A propulsion assembly (100) for an aircraft, in particular for a multi-engine helicopter, comprising: - at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; - a main air circulation device (30) configured to draw air from the first engine (1) via a first draw-off channel (310) and / or from the second engine (2) via a second draw-off channel (320) to deliver the air to the propulsion assembly (100); as well as - a secondary air circulation device (40) configured to, when one of the first engine or the second engine (1, 2) is operating in the at least one standby mode, draw air from the other of the first engine or the second engine (1, 2) that is not operating in the standby mode, and deliver the air to the first engine or the second engine (1, 2) operating in the standby mode, The auxiliary air circulation device (40) comprises a bypass device arranged on one of the first discharge channel or the second discharge channel (310, 320), the first discharge channel and the second discharge channel (310, 320) comprising a solenoid valve (311, 321) and a check valve (312, 322), the bypass device comprises a bypass channel (410) having a solenoid valve (411), a first end (410a) of the bypass device (410) being communicated with the first discharge channel or the second discharge channel (310, 320) downstream of the check valve (312, 322) of the first discharge channel or the second discharge channel (310, 320), and a second end (410b) of the bypass channel (410) being communicated with the first discharge channel or the second discharge channel (310, 320) upstream of the check valve (312, 322).

2. The propulsion assembly (100) according to claim 1, characterized in that The bypass device is configured to allow air originating from one of the first or second engines (1, 2) not operating in standby mode to flow to the other of the first or second engines (1, 2) operating in standby mode, while preventing air from flowing in the opposite direction.

3. The propulsion assembly (100) according to claim 1 or 2, characterized in that: The second end (410b) of the bypass channel (410) is connected to the first discharge channel or the second discharge channel (310, 320) between the solenoid valve (311, 321) and the check valve (312, 322) of the first discharge channel or the second discharge channel (310, 320).

4. The propulsion assembly (100) according to claim 1 or 2, characterized in that: The first and second discharge passages (310, 320) are configured to discharge air from the first and second engines (1, 2) at discharge points (313, 323) of the first and second engines (1, 2), respectively; the bypass passage (410) comprises a check valve (412), the check valve being installed opposite to the check valve (312, 322) of the first or second discharge passage (310, 320); the second end (410b) of the bypass passage (410) is connected to the first or second discharge passage (310, 320) between the discharge point (313, 323) of the first or second discharge passage (310, 320) and the solenoid valve (311, 321).

5. A propulsion assembly (100) for an aircraft, in particular a multi-engine helicopter, comprising: - at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; - a main air circulation device (30) configured to draw air from the first engine (1) via a first draw-off channel (310) and / or from the second engine (2) via a second draw-off channel (320) to deliver the air to the propulsion assembly (100); as well as - a secondary air circulation device (40) configured to, when one of the first engine or the second engine (1, 2) is operating in the at least one standby mode, draw air from the other of the first engine or the second engine (1, 2) that is not operating in the standby mode, and deliver the air to the first engine or the second engine (1, 2) operating in the standby mode, The auxiliary air circulation device (40) comprises a bypass device arranged on one of the first discharge channel or the second discharge channel (310, 320), the first discharge channel and the second discharge channel (310, 320) comprising a solenoid valve (311, 321) and a check valve (312, 322), the bypass device comprises a bypass channel (410) having a solenoid valve (411), a first end (410a) of the bypass device (410) being communicated with the first discharge channel or the second discharge channel (310, 320) downstream of the check valve (312, 322) of the first discharge channel or the second discharge channel (310, 320), wherein the first discharge channel and the second discharge channel (310, 320) are configured to be respectively connected to the discharge channels of the first engine (1, 2) and the second engine (2). Air is discharged from the first engine and the second engine (1, 2) at a discharge point (313, 323), the bypass passage (410) includes a check valve (412), the check valve (412) is installed opposite to the check valve (312, 322) of the first discharge passage or the second discharge passage (310, 320), the second end (410b) of the bypass passage (410) is configured to inject air to the first engine or the second engine (1, 2) operating in the standby mode at an injection point (414) different from the discharge point (313, 323), the bypass passage (410) includes a restrictor (415) arranged between the check valve (412) and the injection point (414), the restrictor (415) is configured to adjust the flow rate of air flowing in the bypass passage (410).

6. A propulsion assembly (100) for an aircraft, in particular for a multi-engine helicopter, comprising: - at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; - a main air circulation device (30) configured to draw air from the first engine (1) via a first draw-off channel (310) and / or from the second engine (2) via a second draw-off channel (320) to deliver the air to the propulsion assembly (100); as well as - a secondary air circulation device (40) configured to, when one of the first engine or the second engine (1, 2) is operating in the at least one standby mode, draw air from the other of the first engine or the second engine (1, 2) that is not operating in the standby mode, and deliver the air to the first engine or the second engine (1, 2) operating in the standby mode, The auxiliary air circulation device (40) comprises a bypass device arranged on one of the first discharge channel or the second discharge channel (310, 320), the first discharge channel and the second discharge channel (310, 320) comprising a three-way valve (311') and a check valve (312), the bypass device comprises a bypass channel (410), a first end (410a) of the bypass channel (410) being connected to the first discharge channel or the second discharge channel (310, 320) downstream of the check valve (312) 10, 320), the second end (410b) of the bypass channel (410) is connected to the three-way valve (311'), and the three-way valve (311') is movable between a first position and a second position, the first position allows air to flow in the first discharge channel or the second discharge channel (310, 320) and prevents air from flowing in the bypass channel (410), and the second position prevents air from flowing in the first discharge channel or the second discharge channel (310, 320) and allows air to flow in the bypass channel (410).

7. A propulsion assembly (100) for an aircraft, in particular for a multi-engine helicopter, comprising: - at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; - a main air circulation device (30) configured to draw air from the first engine (1) via a first draw-off channel (310) and / or from the second engine (2) via a second draw-off channel (320) to deliver the air to the propulsion assembly (100); as well as - a secondary air circulation device (40) configured to, when one of the first engine or the second engine (1, 2) is operating in the at least one standby mode, draw air from the other of the first engine or the second engine (1, 2) that is not operating in the standby mode, and deliver the air to the first engine or the second engine (1, 2) operating in the standby mode, The auxiliary air circulation device (40) comprises a bypass device arranged on one of the first discharge channel or the second discharge channel (310, 320), the first discharge channel and the second discharge channel (310, 320) comprise solenoid valves (311, 321), the bypass device comprises a movable check valve (412') arranged on the first discharge channel or the second discharge channel (310, 320), the movable check valve (412') is movable between a first position and a second position, the first position allows air to flow in the first discharge channel or the second discharge channel (310, 320) along a first circulation direction and prevents air from flowing in a second circulation direction opposite to the first direction, and the second position allows air to flow in the second circulation direction and prevents air from flowing in the first circulation direction.

8. A propulsion assembly (100) for an aircraft, in particular a multi-engine helicopter, comprising: - at least one first engine (1) and a second engine (2) configured to operate in at least one standby mode; - a main air circulation device (30) configured to draw air from the first engine (1) via a first draw-off channel (310) and / or from the second engine (2) via a second draw-off channel (320) to deliver the air to the propulsion assembly (100); as well as - a secondary air circulation device (40) configured to, when one of the first engine or the second engine (1, 2) is operating in the at least one standby mode, draw air from the other of the first engine or the second engine (1, 2) that is not operating in the standby mode, and deliver the air to the first engine or the second engine (1, 2) operating in the standby mode, The auxiliary air circulation device (40) comprises a bypass device arranged on one of the first discharge channel or the second discharge channel (310, 320), the first discharge channel and the second discharge channel (310, 320) comprise solenoid valves (311, 321), the bypass device comprises a blockable check valve (412") arranged on the first discharge channel or the second discharge channel (310, 320), the blockable check valve (412") being configured to be blocked in an open position, allowing air to flow in two circulation directions.

9. A thermal management method for a propulsion assembly (100) according to any one of the preceding claims, comprising: - detecting that one of the first engine (1) or the second engine (2) is operating in at least one standby mode; - measuring the temperature of at least one component of the first engine (1) or the second engine (2) operating in standby mode; as well as - If the measured temperature is less than or equal to a predetermined threshold value, air is bled from the other of the first engine (1) or the second engine (2) that is not running in the standby mode by means of the secondary air circulation device (40), and the air is delivered to the first engine (1) or the second engine (2) that is running in the standby mode.

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