Aircraft propulsion assembly and thermal management method

Abstract

The present disclosure relates to a propulsion assembly (4) of an aircraft (1) and a method for thermally managing such a propulsion assembly (4). The propulsion assembly (4) comprises: a first engine (5a) having a heat exchanger (16a) through which an air duct (15a) passes; a second engine (5b) as a heat engine; and an air interconnection duct (21) connecting the air duct (15a) downstream of the heat exchanger (16a) of the first engine (5a) to the second engine (5b). The thermal management method comprises the steps of: heating, in a heat exchanger (16a) of the first engine (5a), an air flow circulating in an air duct (15a) passing through the heat exchanger (16a) of the first engine (5a); and diverting the heated airflow downstream of the heat exchanger (16a) of the first engine (5a) through an air interconnection duct (21) to the second engine (5b).

Description

Technical Field

[0001] This invention relates to the field of aviation propulsion, and more particularly to engine assemblies for aircraft comprising at least two engines (e.g., turboshaft engines or turboprop engines). Specifically, this invention relates to thermal management of components of propulsion assemblies for aircraft comprising at least two engines, and methods for thermal management of such propulsion assemblies. Background Technology

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. In fact, countries have already implemented, are implementing, or will implement various carbon emission control measures. In particular, an ambitious standard applies to both new and existing aircraft, requiring the implementation of technological solutions to ensure compliance with current regulations. For many years, the civil aviation industry has been actively committed to addressing climate change.

[0003] Technological research has led to significant improvements in the environmental performance of aircraft. The applicant comprehensively considers all influencing factors across the design and development phases to obtain more energy-efficient and environmentally friendly aviation components and products, ensuring that their integration and use in civil aviation have a moderate environmental impact, thereby improving aircraft energy efficiency.

[0004] Therefore, the applicant is committed to reducing negative impacts on the climate and minimizing greenhouse gas emissions as much as possible through the use of sound development and manufacturing methods and operating processes, thereby reducing the environmental impact of its activities.

[0005] The pursuit of minimizing pollution emissions related to air transport involves improving all aspects of the efficiency of propulsion systems, more specifically, improving propulsion efficiency, which characterizes the efficiency with which energy is converted into useful thrust.

[0006] For reasons such as redundancy, aircraft in aviation are typically equipped with at least two engines. In particular, propulsion systems for rotorcraft (such as helicopters or tiltrotor aircraft) usually have at least two engines (typically gas turbine engines), which can be mechanically coupled together. This multi-engine propulsion system allows operation in an economical mode known as "ECO mode." ECO mode is an operating mode, typically corresponding to the cruise phase of a twin-engine architecture, in which one or more engines of the propulsion system are placed in standby mode to provide very low or even zero power, while one or more other engines of the propulsion system ensure most or all of the power delivery.

[0007] As specifically proposed in French patent applications FR 2 967 132 A1 and FR 2 967 133 A1, at least one engine in standby mode can be shut down. To expedite restarting (particularly to allow for possible emergency starts to replace or support another failed power source), these disclosures also propose, for example, using an electric motor to keep one shaft of each shut-down thermal engine rotating. However, it is also conceivable that the standby mode is an extremely low-speed, over-idle state, such as below 40% of the rated speed, without shutting down.

[0008] However, in this standby mode, the thermal engine generates very little or no heat, and depending on atmospheric conditions, especially at high altitudes or in cold weather, its temperature can drop rapidly to very low values, posing risks of icing, difficulty in restarting, and / or loss of lubrication. Indeed, these engines typically require adequate lubrication to provide power, necessitating that the lubricant reach a minimum temperature, typically around 273K to 278K, depending on the lubricant. Therefore, French patent application FR 3 011 277 A1 proposes providing at least one heat source to heat the lubricant of the thermal engine maintained in standby mode. More specifically, the document proposes using the motor driving the thermal engine shaft in standby mode and / or the power supply to that motor as the heat source. However, it may be necessary to find other, more efficient, and / or simpler heat sources to integrate into the thermal engine and / or its lubrication circuitry intended for standby mode. Summary of the Invention

[0009] This disclosure is the result of technical research aimed at significantly improving the performance of aircraft and contributing to reducing their environmental impact, particularly in terms of energy consumption and greenhouse gas emissions. To this end, a first aspect of this disclosure relates to an aircraft propulsion assembly comprising: a first engine having a heat exchanger through which an air duct passes; a second engine serving as a thermal engine; and an air interconnect duct downstream of the heat exchanger of the first engine connecting the air duct to the second engine.

[0010] Due to the arrangement of the interconnecting pipes, the heat released by the first engine can be supplied to the second engine through the heat exchanger of the first engine and the air circulating in the air ducts and air interconnecting pipes, so as to maintain its temperature even at very low speeds or in the shutdown turning mode.

[0011] Specifically, the second engine can be a gas turbine engine, particularly for providing a high power-to-weight ratio. In this case, the second engine may specifically include a gas generator with a combustion chamber and a shaft configured to be driven to rotate in a turning gear mode when the combustion chamber is deactivated. Therefore, heat supplied via an air interconnection duct can maintain the temperature of the second engine even in the turning gear mode with the combustion chamber deactivated, facilitating its de-icing, lubrication, and / or subsequent restart. For this purpose, the air interconnection duct can specifically discharge into the gas generator of the second engine, more specifically into the intake port of the gas generator. Thus, the air supplied by the air interconnection duct can specifically ensure de-icing of the gas generator and / or sufficient temperature in its combustion chamber to facilitate subsequent restart.

[0012] Alternatively or additionally, the second engine may also include a heat exchanger, and an air interconnection duct may discharge upstream of the heat exchanger of the second engine. Therefore, heat transferred by the air supplied by the air interconnection circuit can be received by the second engine through its heat exchanger. In particular, the heat exchanger of the second engine may be an air-oil heat exchanger through which the lubricating oil passages of the second engine pass, thereby maintaining the temperature of the lubricant in the second engine.

[0013] The first engine may also include a lubrication passage, and the heat exchanger of the first engine can therefore be an air-oil heat exchanger through which the lubrication passage of the first engine passes. Thus, the heat supplied to the second engine can come from the cooling of the lubricant in the first engine.

[0014] The component may include at least one valve for redirecting airflow from an air duct to an air interconnect duct, and optionally includes a controlled actuator for actuating the at least one valve. However, alternatively, the at least one valve may include a check valve that is directly actuated by a pressure differential in the duct, rather than being actively controlled.

[0015] In particular, the first engine can be a thermal engine, like the second engine, especially a gas turbine engine. However, it is also possible to consider the first engine as another type, more specifically an electric motor.

[0016] The first and second engines can be mechanically coupled to the same gearbox, which can be, in particular, the main gearbox of an aircraft (especially a rotorcraft, such as a helicopter).

[0017] The second aspect of this disclosure relates to such aircraft including the propulsion assembly of the first aspect, and the third aspect of this disclosure relates to a method for thermal management of the propulsion assembly, the method comprising the steps of: heating an airflow circulating in an air duct passing through an air exchanger of a first engine in a heat exchanger of a first engine; and diverting the heated airflow downstream of the first engine heat exchanger via an air interconnect duct to a second engine, the second engine being a thermal engine capable of operating at reduced speeds or being shut down. Thus, heat released by the first engine is supplied to the second engine via the heat exchanger of the first engine and the air circulating in the air duct and the air interconnect duct, so as to maintain its temperature even in standby mode.

[0018] In particular, the second engine can be a gas turbine engine, which includes a gas generator with a combustion chamber that is deactivated and a shaft that is driven to rotate in turning mode. In this case, a heated airflow can be supplied to the gas generator of the second engine. However, alternatively or additionally, the heated airflow can be supplied upstream of a heat exchanger of the second engine, which can in particular be an air-oil heat exchanger through which the lubrication circuit of the second engine passes. Attached Figure Description

[0019] The invention and its advantages will be better understood by reading the following detailed description of embodiments shown by way of non-limiting examples. This description refers to the accompanying drawings, which are schematic and intended primarily to illustrate the principles of this disclosure.

[0020] In these figures, identical or equivalent elements (or parts thereof) are identified by the same reference numerals in different figures. In these figures:

[0021] Figure 1 The illustration schematically depicts an aircraft with a propulsion assembly that includes two engines.

[0022] Figure 2 A first embodiment of the propulsion assembly is illustrated in more detail;

[0023] Figure 3 The illustration shows an air circuit of a variant of a first embodiment of the propulsion assembly;

[0024] Figure 4 A second embodiment of the propulsion component is illustrated;

[0025] Figure 5 The illustration shows a third embodiment of the propulsion component; and

[0026] Figure 6 The illustration shows a fourth embodiment of the propulsion component. Detailed Implementation

[0027] To make this disclosure more specific, embodiments are described in detail below with reference to the accompanying drawings. However, it should be noted that the present invention is not limited to these embodiments.

[0028] The first figure illustrates a rotorcraft 1, more specifically a helicopter with a main rotor 2 and a counter-torque tail rotor 3, which are coupled to a propulsion assembly 4 for drive. The illustrated propulsion assembly 4 includes a first engine 5a and a second engine 5b. The power output shafts 6a and 6b of these engines 5a and 5b are connected to a main reduction gear 7 to drive the main rotor 2 and the tail rotor 3.

[0029] exist Figure 2 The propulsion assembly 4 according to the first embodiment is illustrated in more detail below. As shown in the figure, each engine 5a, 5b may be a thermal engine, and more specifically a gas turbine engine, including: compressors 8a, 8b; combustion chambers 9a, 9b; first turbines 10a, 10b operably connected to the compressors 8a, 8b via rotating shafts 11a, 11b; and second turbines 12a, 12b or free turbines coupled to power output shafts 6a, 6b. The components of each engine 5a, 5b—compressors 8a, 8b, combustion chambers 9a, 9b, first turbines 10a, 10b, and rotating shafts 11a, 11b—may form gas generators 20a, 20b. The rotating shafts 11a, 11b of each gas generator 20a, 20b are operably coupled to drive units 13a, 13b and fans 14a, 14b.

[0030] Despite Figure 2 and Figures 4 to 6 In the illustration, the drive units 13a, 13b associated with each gas generator 20a, 20b are shown mounted on the same rotational axis as their respective fans 14a, 14b. However, it is also possible to mount the drive units 13a, 13b and fans 14a, 14b associated with each gas generator 20a, 20b on separate shafts and directly coupled to the gas generators 20a, 20b or operably coupled to the gas generators 20a, 20b via an intermediate transmission device (which may in particular include one or more gears).

[0031] The drive units 13a and 13b can be, in particular, electric motors, and more specifically, electric generators connected to the electrical grid of the aircraft 1. Therefore, the drive units 13a and 13b can be used both to start the corresponding engines 5a and 5b, and to generate electricity after starting them. In the first case, the motors of the drive units 13a and 13b can be powered by the aircraft's electrical grid and operate in electric motor mode. In the second case, the motors of the drive units 13a and 13b can operate in generator mode to power the aircraft's electrical grid.

[0032] However, in addition, the drive unit 13b of the second engine 5b can be used to reduce the rotational speed N. 盘车 Rotating the rotating shaft 11b while stopping the combustion chamber 9b is used to keep the second engine 5b in a turning gear mode, at a speed, for example, between 5% and 20% of the rated speed N1 of the rotating shaft 11b. Keeping the gas turbine engine in a turning gear mode can accelerate its possible re-ignition.

[0033] Each fan 14a, 14b can be disposed in air ducts 15a, 15b, which pass through air-oil heat exchangers 16a, 16b, through which the lubrication passages 17a, 17b of the corresponding engines 5a, 5b pass. Each lubrication passage 17a, 17b may also include pumps 18a, 18b, specifically connected to the transmission housings 19a, 19b of the corresponding engines 5a, 5b. As shown, each fan 14a, 14b can be operatively coupled to the rotating shafts 11a, 11b of the corresponding gas generators 20a, 20b, thereby being driven by them to ensure airflow via the corresponding heat exchangers 16a, 16b through air ducts 15a, 15b.

[0034] The power provided by propulsion assembly 4 can vary significantly depending on the flight phase of aircraft 1. Therefore, the power required for cruise speed is typically much less than the maximum continuous power of propulsion assembly 4, and even more so than its maximum takeoff power. However, since propulsion assembly 4 is usually designed to be sized based on this power, it may be far larger than its design size relative to the power required for cruise speed. Therefore, during cruise, if both engines 5a and 5b are operating, they may be far from reaching their optimal operating speeds, resulting in a relatively high fuel consumption rate.

[0035] In principle, for propulsion components comprising multiple engines, it is advisable to maintain cruising speed with at least one of these engines in standby mode. Since at least one engine operates at a speed closer to its optimal speed, overall fuel consumption can be reduced. To achieve this economical operating mode for propulsion component 4, while allowing for immediate power increases when necessary, one of engines 5a and 5b (e.g., the second engine 5b) can be placed in standby mode. This standby mode can be the aforementioned turning mode, or an extremely low-speed over-idle state, such as a speed below 40% of the rated speed, without stopping the engine.

[0036] Therefore, in Figure 2In the illustrated propulsion assembly 4, during the cruise speed of the aircraft 1, the second engine 5b can be in standby mode, while the first engine 5a provides most (if not all) of the power to drive the main rotor 2 and tail rotor 3 via the main gearbox 7. To ensure an emergency power boost, especially in the event of a failure of the first engine 5a, the second engine 5b can be kept in cranking mode by having its rotating shaft 11b driven by the drive unit 13b, or kept at over-idle speed without stopping.

[0037] However, during flight, the temperature of the second engine 5b may drop significantly due to the inactivity of combustion chamber 9b and the potentially very low ambient temperature (especially at high altitudes). Even at over-idle speeds with combustion chamber 9b not in use, the heat released may not be sufficient to maintain the temperature of the second engine 5b and prevent compressor 8b from freezing or the lubricating oil from becoming too viscous. To continue providing sufficient heat to the second engine 5b, even in standby mode, propulsion assembly 4 may therefore include an air interconnect duct 21 that connects the air duct 15a of the first engine 5a (downstream of its heat exchanger 16a) to the second engine 5b. More specifically, in the first embodiment, air interconnect duct 21 may discharge into the air duct 15b of the second engine 5b (upstream of its heat exchanger 16b). Propulsion assembly 4 may also include a valve 22 that may be disposed on air interconnect duct 21 and connected to actuator 23. Actuator 23 may be controlled to open valve 22 when the second engine 5b is in standby mode. The actuator 23 and / or valve 22 may also include a reset device (not shown), which is, for example, resilient or magnetic, to close valve 22 when the second engine 5b is no longer in standby mode.

[0038] Therefore, during the operation of propulsion assembly 4, heat transfer occurs in the air-oil heat exchanger 16a of the first engine 5a, where the lubricating oil circulating in the lubricating oil passage 17a of the first engine 5a is transferred to the pulsating airflow in the air duct 15a of the first engine 5a via the fan 14a, to heat the airflow and cool the lubricating oil of the first engine 5a. When the second engine 5b enters standby mode, the controlled actuator 23 can open valve 22, thereby redirecting the airflow heated by the air-oil heat exchanger 16a of the first engine 5a from downstream of the heat exchanger 16a and in the air duct 15a of the first engine 5a to upstream of the heat exchanger 16b and in the air duct 15b of the second engine 5b. Then, in the heat exchanger 16b of the second engine 5b, heat transfer can proceed in reverse, thereby heating the lubricating oil circulating in the lubricating oil passage of the second engine 5b with the heat carried by the airflow drawn from the first engine 5a.

[0039] Despite Figure 2In the example shown, valve 22 is actively controlled, but it is also possible to use a check valve instead, which is calibrated to similarly respond to the second engine 5b switching to standby mode. Therefore, in a variant of the first embodiment, as... Figure 3 As shown, check valve 22b can be located in the air duct 15b of the second engine 5b, upstream of the inlet of the air interconnect duct 21, and is calibrated to switch from an open position (dashed line) to a closed position as the fan 14b speed decreases when the second engine 5b switches to standby mode. Another check valve 22c can be located in the air interconnect duct 21 and is calibrated to move from a closed position (dashed line) to an open position in response to a pressure drop in the air duct 15b of the second engine 5b caused by the closure of check valve 22b in that air duct. Another check valve 22a can be located in the air duct 15a of the first engine 5a, downstream of the branch leading to the air interconnect duct 21, and is calibrated to switch from an open position (dashed line) to a closed position in response to a pressure drop in the air duct 15a of the first engine 5a caused by the opening of check valve 22c in the air interconnect duct 21.

[0040] However, the air interconnection duct 21 can discharge air to locations other than the air duct 15b of the second engine 5b. Especially... Figure 4 In the second embodiment shown, the air interconnect duct 21 can discharge into the gas generator 20b of the second engine 5b, for example, into the intake duct of the compressor 8b of the second engine 5b. The remaining components of the propulsion assembly according to this second embodiment are similar to the remaining components of the propulsion assembly in the first embodiment, therefore... Figure 4 Zhongyu Figure 2 The same reference numerals are used in the accompanying drawings.

[0041] Thus, during the operation of the propulsion assembly 4 in this second embodiment, when the second engine 5b enters standby mode, the controlled actuator 23 can open valve 22, thereby diverting the airflow heated by the air-oil heat exchanger 16a of the first engine 5a downstream of the heat exchanger 16a, through the air duct 15a of the first engine 5a, to the gas generator 20b of the second engine 5b, and specifically to the air inlet of the compressor 8b, so as to directly supply heat to the gas generator 20b, particularly ensuring its de-icing and / or maintaining the temperature of the combustion chamber 9b above a minimum threshold. Figure 3 Similar to the variant, the bypass of hot air can also be performed by a set of properly calibrated check valves, rather than by active control through a controlled actuator.

[0042] Alternatively, hot air drawn from the air duct 15a of the first engine 5a can be supplied to multiple locations of the second engine 5b. Therefore, in Figure 5In the third embodiment shown, the air interconnect duct 21 can branch so that it discharges, on one hand, into the air duct 15b of the second engine 5b (located upstream of its heat exchanger 16b), as shown in the first embodiment, and on the other hand, into the gas generator 20b of the second engine 5b, for example, into the intake duct of the compressor 8b of the second engine 5b, as shown in the second embodiment. The remaining elements of the propulsion assembly according to this third embodiment are similar to the remaining elements of the propulsion assembly in the foregoing embodiments, therefore Figure 5 Zhongyu Figure 2 and Figure 4 The same reference numerals are used in the accompanying drawings.

[0043] Thus, during the operation of the propulsion assembly 4 according to the third embodiment, when the second engine 5b enters standby mode, the controlled actuator 23 can open valve 22, thereby redirecting the airflow heated by the air-oil heat exchanger 16a of the first engine 5a from downstream of the heat exchanger 16a, through the air duct 15a of the first engine 5a, to upstream of the heat exchanger 16b, through the air duct 15b of the second engine 5b, and through the gas generator 20b of the second engine 5b, particularly to the air inlet of the compressor 8b. Figure 3 Similar to the variant, the bypass of hot air can also be performed by a set of properly calibrated check valves, rather than by active control through a controlled actuator.

[0044] Although in the foregoing embodiments the first engine 5a is a thermal engine, particularly a gas turbine engine, like the second engine 5b, it is also possible to use other types of engines as the first engine, particularly an electric motor, to form a hybrid propulsion assembly. Therefore, in such... Figure 6 In the fourth embodiment shown, the first engine 5a may be an electric motor having a single rotating shaft 6a operably connected to a main reducer 7 to drive the main rotor 2 and the tail rotor 3, and connected to a fan 14a disposed in an air duct 15a. This air duct passes through an air-oil heat exchanger 16a via a lubrication passage 17a of the corresponding first engine 5a. The lubrication passage 17a is not only connected to the transmission case 19a of the corresponding engine 5a, but also, alternatively or additionally, connected to the housing 60 that houses the engine 5a itself. The remaining elements of the propulsion assembly according to this fourth embodiment are similar to the remaining elements of the propulsion assembly of the third embodiment, therefore... Figure 6 Zhongyu Figure 5The same reference numerals are used in the accompanying drawings. However, it is conceivable that the air interconnect duct 21 discharges only into the air duct 15b of the second engine 5b (located upstream of its heat exchanger 16b), as shown in the first embodiment, or only into the gas generator 20b of the second engine 5b, for example, into the intake duct of the compressor 8b of the second engine 5b, as shown in the second embodiment, instead of both.

[0045] Therefore, in a manner similar to the foregoing embodiments, during operation of the propulsion assembly 4 according to this fourth embodiment, when the second engine 5b enters standby mode, the controlled actuator 23 can open valve 22, thereby diverting the airflow heated by the air-oil heat exchanger 16a of the first engine 5a from downstream of the heat exchanger 16a, in the air duct 15a of the first engine 5a, to upstream of the heat exchanger 16b, in the air duct 15b of the second engine 5b, and / or to the gas generator 20b of the second engine 5b, particularly to the air inlet of the compressor 8b. Figure 3 Similar to the variant, the bypass of hot air can also be performed by a set of properly calibrated check valves, rather than by active control through a controlled actuator.

[0046] Although the invention has been described with reference to specific exemplary embodiments, it will be apparent that various modifications and variations can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, various features of the various embodiments mentioned may be combined in additional embodiments. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A propulsion assembly (4) for an aircraft (1), comprising: The first engine (5a) has a heat exchanger (16a) through which an air duct (15a) passes. The second engine (5b), which serves as a heat engine, and An air interconnect duct (21) connects the air duct (15a) to the second engine (5b) downstream of the heat exchanger (16a) of the first engine (5a). The propulsion assembly (4) is characterized in that the first engine (5a) includes a lubrication passage (17b), and the heat exchanger (16a) of the first engine (5a) is an air-oil heat exchanger through which the lubrication passage (17b) of the first engine (5a) passes.

2. The propulsion component (4) according to claim 1, wherein, The second engine (5b) is a gas turbine engine.

3. The propulsion component (4) according to claim 2, wherein, The second engine (5b) includes a gas generator (20b) with a combustion chamber (9b) and a shaft (11b) configured to be driven to rotate in a turning mode when the combustion chamber (9b) is deactivated.

4. The propulsion component (4) according to claim 3, wherein, The air interconnect duct (21) discharges into the gas generator (20b) of the second engine (5b).

5. The propulsion assembly (4) according to any one of claims 1 to 4, wherein, The second engine (5b) also includes a heat exchanger (16b), and the air interconnect duct (21) discharges upstream of the heat exchanger (16b) of the second engine (5b).

6. The propulsion component (4) according to claim 5, wherein, The second engine (5b) includes a lubrication passage (17b), and the heat exchanger (16b) of the second engine (5b) is an air-oil heat exchanger through which the lubrication passage (17b) of the second engine (5b) passes.

7. The propulsion assembly (4) according to any one of claims 1 to 6, comprising: At least one valve (22; 22a, 22b, 22c) is used to redirect airflow from the air duct (15a) to the air interconnect duct (21).

8. The propulsion assembly (4) according to claim 7, comprising: A controlled actuator (23) is used to drive the at least one valve (22; 22a, 22b, 22c).

9. An aircraft (1), comprising: The propulsion component (4) according to any one of claims 1 to 8.

10. A method for thermal management of a propulsion assembly (4), comprising the following steps: In the heat exchanger (16a) of the first engine (5a), the airflow circulating in the air duct (15a) passing through the heat exchanger (16a) of the first engine (5a) is heated, and Downstream of the heat exchanger (16a) of the first engine (5a), the heated airflow is diverted through the air interconnect duct (21) to the second engine (5b), which is a thermal engine. The method is characterized in that the first engine (5a) includes a lubrication passage (17b), and the heat exchanger (16a) of the first engine (5a) is an air-oil heat exchanger through which the lubrication passage (17b) of the first engine (5a) passes.

11. The method according to claim 10, wherein, The second engine (5b) operates at a reduced speed or stops.

12. The method according to claim 11, wherein, The second engine (5b) is a gas turbine engine, which includes a gas generator (20b) with a deactivated combustion chamber (9b) and a shaft (11b) that is driven to rotate in turning mode.

13. The method according to claim 12, wherein, The heated airflow is supplied to the gas generator (20b) of the second engine (5b).

14. The method according to any one of claims 11 to 13, wherein, The heated airflow is provided upstream of the heat exchanger (16b) of the second engine (5b).

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