Aircraft propulsion system, aircraft and helicopter comprising such propulsion system, and method for controlling propulsion system

Abstract

The system (100) comprises a control system (124) configured to:-in response to receiving a quick start command, accelerate a first output shaft (116A) disengaged from the first turboshaft engine (102A); -during acceleration, not imposing any limitation on the acceleration setpoint of the first output shaft (116A); -calculating and monitoring an estimate of the joint time; decreasing an acceleration of the first output shaft (116A) when the estimated value of the engagement time falls below a predetermined threshold value; then, a limit is applied to the acceleration setpoint of the first output shaft (116A) prior to engagement.

Description

Technical Field

[0001] The present invention relates to an aircraft propulsion system, an aircraft and a helicopter including such a propulsion system, and a method for controlling the propulsion system. Background Technology

[0002] Climate change is a major concern for many legislative bodies and regulatory bodies around the world. Indeed, states have already implemented, are implementing, or will implement various carbon emission limits. In particular, an ambitious standard applies to both new and currently in-service aircraft, requiring the implementation of technological solutions to bring them into compliance with current regulations. For several years, civil aviation has been committed to helping address climate change.

[0003] Technological research has significantly improved the environmental performance of aircraft. The applicant has considered influencing factors at all design and development stages to obtain aerospace components and products that consume less energy, are more environmentally friendly, and whose integration and use in civil aviation have a milder environmental impact, thereby improving aircraft energy efficiency.

[0004] Therefore, the applicant continuously strives to reduce its climate impact by using environmentally friendly methods and processes, and to minimize greenhouse gas emissions as much as possible, in order to reduce the environmental footprint of its activities.

[0005] This ongoing research and development effort focuses on next-generation aircraft engines, specifically by using lighter materials and lighter avionics to make aircraft lighter, developing propulsion using electric technology, and developing aviation biofuels as a necessary complement to technological advancements.

[0006] For example, as is known from the prior art, the propulsion system of an aircraft includes: - A first turbine shaft engine with a first output shaft; - A second turbine shaft engine with a second output shaft; - Main output shaft, which is configured to be connected to a mechanical load; - An overrunning clutch system between the first output shaft, the second output shaft, and the main output shaft; -Control system, the control system is designed to: • When the first output shaft is engaged with the main output shaft, the first turbine shaft engine is controlled by limiting the acceleration setpoint of the first output shaft to the acceleration limit; • Control the first turbine shaft engine to disengage the first output shaft, and control the second turbine shaft engine to engage the second output shaft; • In response to receiving a rapid start command, the disengaged first output shaft is accelerated.

[0007] Specifically, the first turboshaft engine is disconnected from the main output shaft, allowing it to operate at idle or even at a standby (so-called "standby" engine), while the second turboshaft engine provides full power, thereby optimizing efficiency.

[0008] In response to a rapid start request, the re-engagement of the first output shaft must be as fast as possible, while ensuring that the overrunning clutch system is not damaged.

[0009] In patent application US 2020 / 0508148 A1, an application is proposed for a speed setpoint for a first output shaft, which is presented as a ramp up to the engagement speed. When the speed of the first output shaft reaches a predetermined threshold, the acceleration setpoint (or equivalently, the torque setpoint) is limited to the engagement allowable limit. However, the response of the first output shaft to the ramp depends on internal and / or external conditions of the turbine shaft engine, and therefore it is unpredictable whether the output shaft speed will increase slowly or rapidly (in response to the ramp). Therefore, by applying an acceleration setpoint limit when the speed of the first output shaft reaches the predetermined threshold, the acceleration limit may be applied too early (when the speed of the first output shaft increases slowly) or too late (when the speed of the first output shaft increases rapidly). When the acceleration limit is applied too early, the speed of the first output shaft will take a long time to reach the speed of the main output shaft. If the acceleration limit is applied too late, the speed of the first output shaft will reach the speed of the main output shaft too quickly, causing a shock upon re-engagement.

[0010] Therefore, the present invention aims to solve at least some of the problems and constraints mentioned above. Summary of the Invention

[0011] This invention is the result of technical research aimed at significantly improving aircraft performance, thereby contributing to a reduction in the environmental impact of aircraft. To this end, the invention relates to an aircraft propulsion system comprising: - A first turboshaft engine, the first turboshaft engine having a first output shaft; - Second turboshaft engine, the second turboshaft engine has a second output shaft; - Main output shaft, which is configured to be connected to a mechanical load; - An overrunning clutch system between the first output shaft, the second output shaft, and the main output shaft; -Control system, the control system is designed to: • When the first output shaft is engaged with the main output shaft, the first turbine shaft engine is controlled by limiting the acceleration setpoint of the first output shaft to the acceleration limit; • Control the first turbine shaft engine to disengage the first output shaft, and control the second turbine shaft engine to engage the second output shaft; • In response to receiving a rapid start command, the disengaged first output shaft is accelerated; The control system is characterized in that, during acceleration in response to receiving a rapid start command, it does not impose any restrictions on the acceleration setpoint of the first output shaft, such that the acceleration of the first output shaft exceeds the acceleration limit, and the control system also aims to: - Calculate and monitor estimates of the time prior to engagement; -When the engagement time drops below a predetermined threshold, reduce the acceleration of the first output shaft; then - Before engagement, a limit is imposed on the acceleration setpoint of the first output shaft.

[0012] Therefore, due to this invention, the limitation of the acceleration setpoint is no longer applied at the start of the rapid start-up phase, which allows the speed to increase more quickly. This last point involves strongly braking the first output shaft before engagement, then reactivating the limitation of the acceleration setpoint and controlling the acceleration so that engagement occurs under favorable conditions.

[0013] Furthermore, using engagement time to begin reducing acceleration ensures that the speed of the first output shaft will reach the speed of the main output shaft in a short time with limited impact risk, essentially independent of the internal or external conditions of the turboshaft engine.

[0014] The present invention may also include one or more of the following optional features in any technically possible combination: Optionally, during the deceleration of the first output shaft, the acceleration is monitored, and when the acceleration of the first output shaft drops below the acceleration limit, a limit is imposed on the acceleration setpoint of the first output shaft. This allows for controllable deceleration, which cannot be achieved by immediately applying an acceleration limit.

[0015] Alternatively, the acceleration limit can also be a function of the rotational speed of the first output shaft.

[0016] Optionally, to accelerate the disengaged first output shaft, the control system is configured to set the fuel flow setpoint of the first turbine shaft engine to a predetermined value, such as the maximum possible value. By setting the flow setpoint instead of providing a speed setpoint and allowing the control chain to infer the flow setpoint, control chain reaction time is avoided, and thus acceleration can be achieved more quickly in response to a rapid start command.

[0017] Alternatively, the propulsion system also includes a starter coupled to the first gas generator, and the control system is configured to activate the starter in order to accelerate the disengaged first output shaft.

[0018] Alternatively, in order to reduce the acceleration of the first output shaft, the control system is configured to set the fuel flow setpoint of the first turbine shaft engine to a predetermined value, such as the minimum possible value.

[0019] Alternatively, in order to reduce the acceleration of the first output shaft, the control system is configured to stop the starter.

[0020] An aircraft including a propulsion system according to the invention is also proposed.

[0021] A helicopter is also proposed, which includes a propulsion system according to the invention and a main rotor as a mechanical load.

[0022] A method for controlling an aircraft propulsion system is also proposed, the aircraft propulsion system comprising: a first turboshaft engine having a first output shaft; a second turboshaft engine having a second output shaft; a main output shaft designed to be connected to a mechanical load; and an overrunning clutch system between the first output shaft, the second output shaft, and the main output shaft, the method comprising the following steps: - When the first output shaft is engaged with the main output shaft, the first turbine shaft engine is controlled by limiting the acceleration setpoint of the first output shaft to the acceleration limit; - Control the first turbine shaft engine to disengage the first output shaft, and control the second turbine shaft engine to engage the second output shaft; - In response to receiving a rapid start command, the disengaged first output shaft is accelerated; The method is characterized in that, during acceleration in response to receiving a rapid start command, no limit is imposed on the acceleration setpoint of the first output shaft, causing the acceleration of the first output shaft to exceed the acceleration limit, and the method further includes: - Calculate and monitor estimates of the time prior to engagement; -When the engagement time drops below a predetermined threshold, reduce the acceleration of the first output shaft; then - Before engagement, a limit is imposed on the acceleration setpoint of the first output shaft.

[0023] A computer program is also proposed, which can be downloaded from a communication network and / or recorded on a computer-readable medium, characterized in that the computer program includes instructions for performing the steps of the method according to the invention when the program is executed on a computer. Attached Figure Description

[0024] The invention will be better understood through the following description, given only by way of example and with reference to the accompanying drawings, in which: - Figure 1 This is a simplified view of the propulsion system according to the present invention. - Figure 2 It is used for Figure 1 The diagram shown is a block diagram of the control method for the propulsion system. - Figure 3 It shows Figure 1 The timing diagram of the physical parameters of the propulsion system shown is as follows. - Figure 4 yes Figure 1 A time-series diagram showing the evolution of flow rate and minimum flow rate values ​​of the first turbine shaft engine in the propulsion system, and - Figure 5 It is used for Figure 1 The diagram shown is a block diagram of the control system for the propulsion system. Detailed Implementation

[0025] Reference Figure 1 The system 100 for propelling an aircraft according to the present invention will now be described. For example, the aircraft is a helicopter.

[0026] The propulsion system 100 includes a first turboshaft engine 102A and a second turboshaft engine 102B. Each turboshaft engine 102A, 102B includes gas generators 104A, 104B and free turbines 106A, 106B supplied by the gas generators 104A, 104B. The gas generators 104A, 104B include air compressors 108A, 108B and combustion chambers 110A, 110B connected to each other. In the combustion chambers 110A, 110B, fuel is configured to be burned using air compressed by the air compressors 108A, 108B to produce gases that provide kinetic energy. Each gas generator 104A, 104B also includes turbines 112A, 112B for the partial expansion of these gases, the turbines 112A, 112B being connected to the air compressors 108A, 108B via drive shafts 114A, 114B to drive the air compressors 108A, 108B to rotate. The gas is also configured to rotate the free turbines 106A and 106B. Each turboshaft engine 102A and 102B also includes output shafts 116A and 116B, which are connected to the free turbines 106A and 106B for being driven by the free turbines, denoted as n2 respectively. A n2 B Rotation at a speed of n2. Each speed n2 A n2 B It is usually expressed as a percentage of a fixed nominal speed.

[0027] The propulsion system 100 also includes a main output shaft 118, which is adapted to be connected to a mechanical load (not shown) (e.g., the main rotor of a helicopter) and adapted to rotate at a speed denoted as nr to rotate the mechanical load.

[0028] The propulsion system 100 also includes an overrunning clutch system 120 between the output shafts 116A, 116B of the turboshaft engines 102A, 102B and the main output shaft 118.

[0029] The propulsion system 100 also includes associated starter motors 122A, 122B for each turboshaft engine 102A, 102B. Each starter 122A, 122B includes, for example, an electric motor designed to rotate the gas generators 104A, 104B of the associated turboshaft engine 102A, 102B.

[0030] The propulsion system 100 also includes a control system 124 for the turboshaft engines 102A, 102B and the starter motors 122A, 122B.

[0031] The control system 124 specifically includes control chains 126A, 126B for each turbine shaft engine 102A, 102B, the control chains being configured to operate according to the speed setpoint n2 of the output shafts 116A, 116B. A * n2 B * Determine the acceleration setpoint n2' of output shafts 116A and 116B A* n2' B* And based on the acceleration setpoint n2' A* n2' B* Determine fuel flow setpoint D A * D B * Therefore, the control system 124 is configured to set the fuel flow rate to D. A * D B * It is used in turboshaft engines 102A and 102B.

[0032] For each turboshaft engine 102A, 102B, the control system 124 also includes acceleration limiting modules 128A, 128B, which are configured to limit the acceleration setpoint n2. A ’* n2 B ’* Limit to acceleration limit L A L B The acceleration limit, for example, is specifically the velocity n². A n2 B It varies as a function of L. Typically, this acceleration limit L... A L BMaintain below 6% of the nominal speed (nominal speed is measured in revolutions per second). For example, based on the operating points of turboshaft engines 102A and 102B, the acceleration limit L... A L B Between 4% and 6% of the nominal speed per second.

[0033] Reference Figure 2 , Figure 3 and Figure 4 An example of a method 200 for controlling the propulsion system 100, implemented by the control device 124, will now be described.

[0034] In step 202, the control system 124 controls the turboshaft engine 102A, while the output shaft 116A of the turboshaft engine is engaged with the main output shaft 118. During this step 202, the control device 124 uses the control chain 126A and the acceleration limiting module 128A to set the acceleration setpoint n2'. A * Limit to acceleration limit L A The limitation on the acceleration setpoint ensures that when the output shaft 116A is engaged, the acceleration of the main rotor is not too high during startup or after a speed drop (e.g., due to high power demands). In the case of a helicopter, this limitation makes it possible to avoid yaw turbulence, the tendency for the helicopter to rotate around its own axis due to the different accelerations between the main rotor and the tail rotor.

[0035] In step 204, the control system 124 causes the output shaft 116A to rotate at a lower speed than the main output shaft 118, thereby disengaging the output shaft from the main output shaft 118. For example, the turboshaft engine 102A is in standby mode (referred to as idle mode), in which combustion chamber 110A is shut off and gas generator 104A is driven by starter 122A at a sufficiently low speed. Figure 3 The command C is equal to 1, which makes the speed n2 of the output shaft 116A. A Zero (0% of the nominal speed of output shaft 116A). For example, gas generator 104A is driven by starter 122A at a speed between 5% and 20% of the rated speed of gas generator 104A.

[0036] During step 206, the control system 124 receives a request to rapidly start the output shaft 116A, that is, a request for rapid re-engagement of the output shaft 116A. This means that the speed n2 of the output shaft 116A... A The speed of the main output shaft 118 must be reached as quickly as possible.

[0037] In step 208, in response to receiving a rapid start request, the control system 124 controls the turbine shaft engine 102A and / or starter 122A to accelerate the output shaft 116A. During this step, the control system 124 suppresses the acceleration limiting module 128A to prevent the acceleration setpoint n2' from being applied. A * Limit to the limit L A Limitations. For example, the control system 124 is configured not to apply an acceleration setpoint n2'. A * Any restrictions. Alternatively, an acceleration setpoint n2' can be applied. A * One or more other limitations (e.g., always applying very high security limits) instead of the limit L A Furthermore, the control system 124 accelerates the output shaft 116A. For this purpose, the control system 124, for example, adjusts the flow setpoint D. A Set to a very high predetermined value, such as the maximum value. For example, control system 124 controls starter 122A to accelerate output shaft 116A.

[0038] In parallel with step 208, which accelerates the output shaft 116A, in step 210, the control system 124 calculates an estimate of the engagement time T over time, i.e., the rotational speed n2 of the output shaft 116A. A The time taken to reach the speed nr of the main output shaft 118. This estimate is calculated, for example, using the acceleration n2' of the output shaft 116A. A For example, control system 124 uses the following equation: T = (nr - n2) A ) / n2' A During step 210, the control system 124 also monitors the estimated value T to detect when the estimated value drops below a predetermined threshold.

[0039] During step 212, the control system 124 detects that the estimated value T has dropped below a predetermined threshold.

[0040] In step 214, in response to detecting that the estimated value T has dropped below a predetermined threshold, the control system 124 controls the turbine shaft engine 124 and / or the starter 122A to reduce the acceleration of the output shaft 116A.

[0041] For example, the control system 124 sets the flow rate setpoint D. A * Set to a low value, such as the minimum value D. A * min ,like Figure 4 As shown, this minimum value can vary over time depending on the operating point of the first turbine shaft engine 102A. By maintaining this minimum value D...A * min The first turbine shaft engine 102A is guaranteed not to shut down when the flow setpoint D is above or maintained at this minimum value. A * Equal to the minimum value D A * min At times, such as Figure 4 As shown, it achieves the maximum deceleration capability of the first turboshaft engine 102A.

[0042] For example, control system 124 stops starter 122A (in... Figure 3 (The control C is zero). In step 214, the control system 124 also monitors the acceleration n2'. A To detect when the acceleration drops to the acceleration limit L A the following.

[0043] During step 216, the control system 124 detects acceleration n2' A It has dropped to the acceleration limit L A the following.

[0044] During step 218, in response to the detection of acceleration n2' A It has dropped to the acceleration limit L A Next, the control system 124 activates the acceleration limiting module 128A to apply the acceleration setpoint n2'. A * Restrictions.

[0045] During step 220, output shaft 116A reaches the speed nr of main output shaft 118 and engages with main output shaft. At this time, acceleration limiting module 128A is activated to limit L. A The following accelerations are used for engagement.

[0046] Reference Figure 5The control system 124 is, for example, a computer system including a data processing unit 502 (such as a microprocessor) and a main memory 504 (such as RAM memory) accessible by the processing unit 502. The computer system also includes, for example, a network interface and / or computer-readable media, such as local media (such as a local hard disk 506), or remote media (such as a remote hard disk accessible via a communication network through a network interface), or removable media (such as a Universal Serial Bus (USB) key, or a Compact Disc (CD) or Digital Versatile Disc (DVD)) readable by a suitable computer system drive (such as a USB port or a CD and / or DVD drive). A computer program 508 containing instructions for the processing unit 502 is stored on the medium 506 and / or can be downloaded via the network interface. The computer program 508 is configured, for example, to be downloaded to the main memory 504 such that the processing unit 502 can execute the instructions of the computer program. Specifically, the computer program includes instructions for performing the steps of method 200 when the program is executed by the processing unit 502 of the computer system.

[0047] Alternatively, all or some of these modules may be implemented as hardware modules, i.e., electronic circuits (e.g., microwires), without including computer programs.

[0048] In summary, it should be noted that the present invention is not limited to the embodiments described above. In fact, those skilled in the art will understand that various modifications can be made to the embodiments described above based on the teachings just disclosed.

[0049] In the above detailed description of the invention, the terminology used should not be construed as limiting the invention to the embodiments disclosed in this specification, but should be construed as including all equivalent means that a person skilled in the art could conceive of by applying his or her conventional knowledge to the implementation of the teachings that have just been disclosed.

Claims

1. An aircraft propulsion system (100), comprising: - First turboshaft engine (102A), the first turboshaft engine having a first output shaft (116A); - Second turboshaft engine (102B), the second turboshaft engine having a second output shaft (116B). - Main output shaft (118), which is configured to be connected to a mechanical load; - An overrunning clutch system (120) between the first output shaft, the second output shaft (116A, 116B) and the main output shaft (118). -Control system (124), the control system is designed to: • When the first output shaft (116A) is engaged with the main output shaft (118), the acceleration setpoint of the first output shaft (116A) is limited to the acceleration limit (L). A (202) to control the first turboshaft engine (102A); • Control (204) the first turbine shaft engine (102A) to disengage the first output shaft (116A), and control the second turbine shaft engine (102B) to engage the second output shaft (116B); • In response to receiving the (206) rapid start command, the disengaged first output shaft (116A) is accelerated (208). The control system (124) is characterized in that, during the acceleration (208) in response to receiving the rapid start command, it does not impose any restrictions on the acceleration setpoint of the first output shaft (116A) such that the acceleration of the first output shaft (116A) exceeds the acceleration limit, and the control system (124) is also intended to: - Calculate and monitor (210) the estimated time prior to engagement; -When the engagement time drops below a predetermined threshold, reduce the acceleration of the first output shaft (116A); then - Before engagement, the limitation described in (218) is applied to the acceleration setpoint of the first output shaft (116A).

2. The propulsion system (100) according to claim 1, wherein, The acceleration is monitored during the period when the acceleration of the first output shaft (116A) decreases, and wherein the acceleration of the first output shaft (116A) decreases to the acceleration limit (L). A When the acceleration is below a certain value, a limit is imposed on the acceleration setpoint of the first output shaft (116A).

3. The propulsion system (100) according to claim 1 or 2, wherein, The acceleration limit (L) A ) is the rotational speed (n2) of the first output shaft (116A). A The function of ).

4. The propulsion system (100) according to any one of claims 1 to 3, wherein, In order to accelerate (208) the disengaged first output shaft (116A), the control system (124) is configured to set the fuel flow rate of the first turbine shaft engine (102A) to a setpoint (D). A Set to a predetermined value, such as the maximum possible value.

5. The propulsion system (100) according to any one of claims 1 to 4 further includes a starter (122A) coupled to the first gas generator (104A), and wherein, In order to accelerate (208) the disengaged first output shaft (116A), the control system (124) is configured to activate the starter (122A).

6. The propulsion system (100) according to any one of claims 1 to 5, wherein, In order to reduce the acceleration (212) of the first output shaft (116A), the control system (124) is configured to set the fuel flow rate of the first turbine shaft engine (102A) to a setpoint (D). A Set to a predetermined value, such as the minimum possible value.

7. The propulsion system (100) according to any one of claims 1 to 6, wherein, In order to reduce the acceleration (212) of the first output shaft (116A), the control system (124) is configured to stop the starter (122A).

8. A helicopter comprising a propulsion system according to any one of claims 1 to 7 and a main rotor as a mechanical load.

9. A method (200) for controlling an aircraft propulsion system, the aircraft propulsion system comprising: A first turboshaft engine (102A) having a first output shaft (116A); a second turboshaft engine (102B) having a second output shaft (116B); a main output shaft (118) configured to be connected to a mechanical load; and an overrunning clutch system between the first output shaft, the second output shaft (116A, 116B), and the main output shaft (118); the method includes: - When the first output shaft (116A) is engaged with the main output shaft (118), the acceleration setpoint of the first output shaft (116A) is limited to the acceleration limit (L). A (202) to control the first turboshaft engine (102A); - Control (204) the first turbine shaft engine (102A) to disengage the first output shaft (116A), and control the second turbine shaft engine (102B) to engage the second output shaft (116B); - In response to receiving the (206) rapid start command, the disengaged first output shaft (116A) is accelerated (208). The method is characterized in that, during the acceleration period in response to receiving a rapid start command, no restriction is imposed on the acceleration setpoint of the first output shaft (116A) such that the acceleration of the first output shaft (116A) exceeds the acceleration limit, and the method further includes: - Calculate and monitor (210) the estimated time prior to engagement; -When the engagement time drops below a predetermined threshold, reduce (214) the acceleration of the first output shaft (116A); then - Before engagement, the acceleration setpoint of the first output shaft (116A) is restricted by (218).

10. A computer program (508), said computer program being downloadable from a communication network and / or recorded on a computer-readable medium, characterized in that, The computer program includes instructions for performing the steps of the method (200) according to claim 9 when the program is executed on a computer.

Images