Method for controlling a turbomachine comprising an electric machine

Abstract

The invention relates to a method for controlling a turbomachine (T) comprising a gas generator, the turbomachine comprising an electric machine (ME) forming a torque injection / removal device on one of the low pressure / high pressure rotation axes of the gas generator. The method comprises a step of using a fuel control loop in order to determine a fuel flow setpoint (QCMD) in the combustion chamber, and comprises, upon reaching at least one operability stop point, determining a corrected fuel flow setpoint, the corrected fuel flow setpoint exhibiting a difference with the setpoint. The method also comprises a step of using a torque control loop in order to determine a torque setpoint (TRQCMD) of the electric machine, and comprises determining a torque correction amount as a function of the difference, determining the torque setpoint as a function of the torque correction amount.

Description

Technical Field

[0001] This invention pertains to the general field of aviation, and more specifically to the general field of turbines. More specifically, it relates to a method for controlling a turbine comprising a low-pressure rotor and a high-pressure rotor, respectively driven by a low-pressure rotating shaft and a high-pressure rotating shaft, and at least one motor forming a means for injecting torque into / removing torque from one of the rotating shafts. Background Technology

[0002] refer to Figure 1 The diagram schematically illustrates a turbine 100 including a gas generator. More specifically, Figure 1 The example depicts a turbine 100 of the type of twin-rotor turbofan engine used in aircraft.

[0003] In a known manner, turbine 100 includes, from upstream to downstream along the gas flow direction, a fan 110, a low-pressure compressor 111, a high-pressure compressor 112, a combustion chamber 113 receiving a fuel flow setpoint QCMD, a high-pressure turbine 114, a low-pressure turbine 115, and a main exhaust nozzle 116. The low-pressure (or LP) compressor 111 and the low-pressure turbine 115 are connected via a low-pressure shaft 121 and together form a low-pressure rotor. The high-pressure (or HP) compressor 112 and the high-pressure turbine 114 are connected via a high-pressure shaft 122 and together with the combustion chamber form a high-pressure rotor. The fan 110, driven by the low-pressure shaft 121, compresses the intake air. This air is split downstream of the fan 110 into a secondary airflow and a primary airflow. The secondary airflow is directly delivered toward a secondary nozzle (not shown) and injected through the secondary nozzle to generate the thrust provided by turbine 100. The primary airflow enters a gas generator composed of the low-pressure rotor and the high-pressure rotor and is then injected into the main nozzle 116.

[0004] Typically, the fuel flow setpoint QCMD is determined as a function of the difference between turbine speed and a setpoint speed, which depends on the position of a control stick operable by the pilot. For this purpose, a fuel control loop is implemented by a control unit, usually integrated into the FADEC (Full Authority Digital Engine Control) computer located within the turbine.

[0005] The fuel control circuit is also intended to ensure that the fuel flow injected into the combustion chamber during acceleration or deceleration (i.e., transient phases) does not exceed at least one given threshold known as the "operability limit," exceeding which could lead to engine failure. In other words, the fuel control circuit helps manage the controllability and operability of the turbine 100.

[0006] "Operability" here refers, in a manner known per se, to the concept of ensuring the proper functioning of turbine 100. More specifically, this means ensuring that the operating line of turbine 100 remains within the authorized operating range so as not to exceed the physical limits of the components equipped with turbine 100.

[0007] As a non-limiting example, for the operation of turbine 100, and particularly its high-pressure compressor 112, protective thresholds corresponding to acceleration and deceleration limits are implemented, respectively. These operability limits are determined by restrictions relating to the ratio C / P between the fuel flow rate C injected into the combustion chamber and the static pressure P measured at the combustion chamber inlet. These limits on the ratio C / P are fixed in a manner known per se to prevent surge during acceleration and engine shutdown during deceleration. In other words, these limits correspond to design constraints of turbine 100 that must be adhered to to ensure engine operability.

[0008] Therefore, turbine designers must try to optimize the placement of the operating line by placing it as high as possible to benefit from better compressor performance, while maintaining sufficient distance (i.e., margin) from the operability limits to allow for safe acceleration / deceleration.

[0009] Another constraint to consider involves the fact that the engine's acceleration or deceleration time is directly dependent on the margins associated with maneuverability limits. For example, when a pilot requests an increase in engine speed, the current speed may not be able to follow the requested acceleration path because the latter would require exceeding the acceleration limits, which would result in surge. Therefore, in this case, to protect the turbine, the current speed is increased slowly with a delay.

[0010] To improve the turbine's response time during the transient phase, while limiting the impact of design constraints related to operability limits, a hybridization mechanism is specifically proposed by equipping the turbine 100 with an electric motor. This electrical mechanism results in the injection of torque into and / or removal from one of the rotating shafts associated with the low-pressure rotor and the high-pressure rotor, respectively.

[0011] Document WO2016 / 020618 describes an implementation using such a motor. However, it is currently unclear how the motor is controlled in this implementation. Specifically, no explicit and reproducible strategy is proposed to control the motor to optimize turbine operation and operability. Summary of the Invention

[0012] The object of the present invention is to partially or completely overcome the shortcomings of the prior art, particularly the aforementioned prior art, by proposing a solution that enables the effective regulation of the torque generated by at least one motor equipped with a hybrid turbine, thereby obtaining excellent response time from the turbine, improving its operability, and limiting the power consumption of the at least one motor.

[0013] Therefore, according to a first aspect, the present invention relates to a method for controlling a turbine, the turbine including a gas generator comprising a combustion chamber, a low-pressure rotating shaft, and a high-pressure rotating shaft, the turbine including at least one motor configured to inject torque into / remove torque from one of the rotating shafts. Furthermore, the method includes the step of implementing a fuel control loop to determine a fuel flow rate setpoint entering the combustion chamber, and includes:

[0014] - Monitor the turbine to detect whether at least one operability limit of the turbine has been reached.

[0015] If at least one operability limit is reached, a corrected fuel flow rate setting is determined, which differs from the current fuel flow rate setting and is referred to as the "flow difference".

[0016] The method further includes the step of implementing a torque control loop to determine a torque setpoint for the at least one motor, and includes determining a torque correction amount as a function of the flow difference, wherein the torque setpoint is determined as a function of the torque correction amount.

[0017] Therefore, according to the control method described above, when the control provided by the fuel control loop is limited, for example due to potential surge or shutdown, the torque control loop can work in conjunction with the fuel flow control loop. Thus, the torque control loop allows for greater flexibility in application to accommodate turbine design constraints. Consequently, turbine operability is improved.

[0018] For example, in the event of surge and shutdown, the torque control loop advantageously allows for the separation of the turbine's surge and shutdown limits, enabling better control of fuel setpoints.

[0019] Advantageously, the torque control loop does not replace the fuel flow control loop, but rather supports it when operating limits are reached, i.e., when one or more operability limits are met. Therefore, the fundamental principles of speed control remain undisturbed, ensuring reliable control, and consequently, a significantly better turbine response time compared to existing solutions.

[0020] Furthermore, a significant difference between this control method and existing technologies is that the torque correction amount is determined as a function of the flow difference. In fact, such arrangements are particularly advantageous because they allow for consideration of the physical realities of the turbine, especially its operation, regardless of speed (transient or virtually stable).

[0021] "Physical reality" here refers to the fact that the operation of at least one motor is related to the actual changes in fuel flow. In other words, when determining quantities, the thermodynamic aspects involved in changes in fuel flow should be considered.

[0022] In practice, the control method may be considered individually or may further include one or more of the following features based on all technically possible combinations.

[0023] In practice, the torque correction amount is determined to be equal to:

[0024]

[0025] In the expression:

[0026] -EC_DEB corresponds to the flow difference.

[0027] -FHV corresponds to the calorific value of the fuel.

[0028] -N corresponds to the rotational speed of the rotating shaft from which the torque is injected / removed by the at least one motor (ME).

[0029] -C_1 is a constant.

[0030] -η corresponds to the thermal efficiency of the gas generator.

[0031] The expression developed by the inventors is particularly noteworthy because it allows for the determination of torque correction amounts in a simple, fast, and inexpensive manner. Furthermore, the versatility of this expression makes it possible to apply the invention to any type of industrial machine equipped with a turbine according to the invention.

[0032] In practical implementation, the efficiency η of the gas generator is expressed in the following form:

[0033]

[0034] In the expression:

[0035] -M corresponds to Mach speed.

[0036] -γ corresponds to the ratio between isobaric heat capacity and isochoric heat capacity.

[0037] -OPR corresponds to the total pressure rate of the gas generator.

[0038] In practice, the torque correction amount is determined according to the following expression:

[0039]

[0040] In the expression:

[0041] -EC_DEB corresponds to the flow difference.

[0042] -FHV corresponds to the calorific value of the fuel.

[0043] -N corresponds to the rotational speed of the rotating shaft from which the torque is injected / removed by the at least one motor (ME).

[0044] -C'_1 is a constant.

[0045] As long as the efficiency is considered constant, the expression for the torque correction is particularly easy to calculate, which can be demonstrated by the fact that the above-mentioned efficiency η fluctuates very little except at idle speed.

[0046] In specific implementation, the at least one operability limit corresponds to any one of the following parameters:

[0047] -C / P limit,

[0048] -The limit relative to the mechanical speed N1,

[0049] - Relative to the limit of mechanical speed N2,

[0050] - The limit relative to the exhaust temperature at the inlet of the low-pressure turbine of the turbine.

[0051] According to another aspect, the present invention relates to a system for controlling a turbine, the turbine including a gas generator comprising a combustion chamber, a low-pressure rotating shaft, and a high-pressure rotating shaft, the turbine including at least one motor configured to inject torque into / remove torque from one of the rotating shafts. Furthermore, the control system includes a fuel control loop for determining a setpoint for the fuel flow rate into the combustion chamber, the fuel control loop including:

[0052] - A module for monitoring the turbine, configured to detect whether at least one operability limit of the turbine has been reached.

[0053] - A determination module is configured to determine a corrected fuel flow setting value if the at least one operability limit is reached, the corrected fuel flow setting value exhibiting a difference relative to the current fuel flow setting value, referred to as "flow difference".

[0054] The control system further includes a torque control loop for determining the torque setpoint of the at least one motor, the torque control loop comprising:

[0055] - A first determining module, configured to determine the torque correction amount as a function of the flow difference.

[0056] - A second determining module, configured to determine the torque setpoint as a function of the torque correction amount.

[0057] According to another aspect, the present invention relates to a gas generator turbine, the gas generator comprising a combustion chamber, a low-pressure rotating shaft and a high-pressure rotating shaft, the turbine comprising at least one motor forming a device for injecting torque into / removing torque from one of the rotating shafts, and a control system according to the invention.

[0058] According to another aspect, the present invention relates to an aircraft comprising a turbine according to the invention. Attached Figure Description

[0059] Other features and advantages of the invention will become more apparent from the following description, which illustrates a non-limiting exemplary embodiment of the invention, with reference to the accompanying drawings. In the drawings:

[0060] [ Figure 1 ] Figure 1 A turbine including a gas generator according to the prior art is shown in schematic form;

[0061] [ Figure 2 ] Figure 2 An embodiment of the turbine according to the invention in its environment is illustrated in schematic form;

[0062] [ Figure 3 ] Figure 3 It shows that it belongs to Figure 2 An example of the hardware architecture of the control system of the turbine according to the present invention;

[0063] [ Figure 4 ] Figure 4 The following diagram illustrates an operational example of two control loops according to the present invention, a fuel flow control loop B1 and a torque control loop B2, wherein loops B1 and B2 belong to... Figure 3 The control system;

[0064] [ Figure 5 ] Figure 5 The main steps of the control method according to the present invention are shown in the form of a flowchart. Detailed Implementation

[0065] This invention belongs to the field of regulating (i.e. controlling) the operation of a turbine, including a gas generator.

[0066] In the following description, turbines of the twin-shaft turbofan engine type for aircraft, such as passenger-carrying civil aircraft, are considered in a non-limiting manner. However, it should be noted that the invention is applicable to any type of turbine as long as it includes a gas generator. For example, turboshaft engines, ducted engines, etc., may be considered.

[0067] Furthermore, the invention remains applicable to any type of aircraft (airplanes, helicopters, etc.), and more broadly to any type of industrial machine equipped with a turbine according to the invention.

[0068] Figure 2 An embodiment of the turbine T according to the invention in its environment is shown in schematic form.

[0069] The turbine T has a general construction that at least conforms to the prior art. As a non-limiting example, the above references... Figure 1 This describes the overall structure.

[0070] Therefore, the turbine T, from upstream to downstream along the gas flow direction, includes a fan 10, a low-pressure compressor 11, a high-pressure compressor 12, a combustion chamber 13 receiving the fuel flow setpoint QCMD, a high-pressure turbine 14, a low-pressure turbine 15, and a main exhaust nozzle 16. The low-pressure (or LP) compressor 11 and the low-pressure turbine 15 are connected by a low-pressure shaft 21 and together form a low-pressure rotor. The high-pressure (or HP) compressor 12 and the high-pressure turbine 14 are connected by a high-pressure shaft 22 and together with the combustion chamber form a high-pressure rotor. The fan 10, driven by the low-pressure shaft 21, compresses the intake air. This air is divided downstream of the fan 10 into a secondary airflow and a main airflow. The secondary airflow is directly delivered toward the secondary nozzle (not shown) and injected through the secondary nozzle to generate the thrust provided by the turbine T. The main airflow enters the gas generator composed of the low-pressure rotor and the high-pressure rotor and is then injected into the main nozzle 16.

[0071] In a known manner, the operation of turbine T is controlled by full authority digital engine control (FADEC 20). Furthermore, to modify the speed of turbine T, the aircraft pilot modifies the position of the control stick, which in turn modifies the fuel flow setpoint QCMD entering combustion chamber 13.

[0072] The turbine T according to the invention also includes at least one electric motor ME. Conventionally, the at least one electric motor ME forms a device for injecting / removing torque to / from one of the rotating shafts. The torque generated by the electric motor ME is generated upon receiving a torque setpoint TRQCMD, as detailed below.

[0073] As described below in the instruction manual, Figure 2 As shown, the turbine T is considered in a non-limiting manner to include a single motor ME, and the rotating shaft through which torque is injected / removed is the high-pressure shaft 22. However, it is also entirely possible to consider the rotating shaft operated by a single motor ME as the low-pressure shaft 21. It is also entirely possible to consider the turbine T to include multiple motors T, which are capable of injecting torque into and / or removing torque from a single shaft, or in fact, injecting into / removing torque from a single shaft.

[0074] Therefore, according to the first operating mode, the motor ME is configured to generate torque suitable for driving the high-voltage shaft 22. In a conventional manner, this first operating mode corresponds to a "traction operating mode". Furthermore, according to the second operating mode, the motor ME is configured to generate torque suitable for removing mechanical energy from the high-voltage shaft 22. This removed energy can be used, for example, to drive at least one electrical device of the turbine T, such as full-authority digital engine control or FADEC. Again, in a conventional manner, this second operating mode corresponds to a "generator operating mode".

[0075] Those skilled in the art can refer to document WO2016 / 020618 to understand the production and implementation of such motors ME for turbines, and therefore these aspects will not be described in further detail here.

[0076] According to the present invention, the turbine T further includes a control system SYS_C, which includes a fuel setpoint QCMD control loop referred to as "first loop B1" and a torque setpoint TRQCMD control loop referred to as "second loop B2". According to the present invention, the first loop B1 and the second loop B2 are implemented according to a control method described in detail below.

[0077] In this embodiment, the control system SYS_C is integrated into FADEC 20, specifically into the computer of FADEC 20. However, as long as the turbine T can be controlled via the two control loops B1 and B2, no restrictions are imposed on the location of the control system SYS_C within the turbine T.

[0078] In the following description, control loops B1 and B2 are considered in a non-limiting manner to be integrated into a single entity that forms a control device in conjunction with the control system SYS_C. However, according to other examples not detailed herein, it is also entirely possible to integrate the first loop B1 and the second loop B2 into a first control device and a second control device, respectively, which are themselves integrated into the control system SYS_C.

[0079] Figure 3 An example of the hardware architecture of the control system SYS_C according to the present invention is shown in schematic form.

[0080] like Figure 3 As shown, the control system SYS_C according to the present invention has a computer hardware architecture. Therefore, the control system SYS_C specifically includes a processor 1, a random access memory 2, a read-only memory 3, and a non-volatile memory 4. It also includes a communication device 5.

[0081] The communication device 5 specifically allows the control system SYS_C to send a torque setpoint TRQCMD to the motor ME, and thus the motor ME is equipped with a communication device configured to receive the torque setpoint TRQCMD. The communication device 5 also allows the control system SYS_C to receive measurements of physical quantities acquired via an acquisition device equipped with a turbine T. The communication device 5 includes, for example, a computer data bus suitable for transmitting the setpoint and the measurements of the physical quantities. According to another example, the communication device 5 includes a wired or wireless communication interface capable of implementing any suitable protocol known to those skilled in the art (Ethernet, Wi-Fi, Bluetooth, 3G, 4G, 5G, etc.).

[0082] The measured values ​​of the physical quantities correspond, for example, to measured values ​​of pressure, shaft speed, and aircraft speed. Furthermore, the acquisition device configured to acquire these measured values ​​includes, in a known manner, an acquisition chain comprising sensors dedicated to measuring each of the quantities. The construction of such acquisition devices is generally well known to those skilled in the art and therefore will not be described in further detail here. Moreover, based on the embodiments described below with respect to the control method according to the invention, those skilled in the art can also determine which physical quantities need to be measured in order to execute the control method according to the invention.

[0083] The read-only memory 3 of the control system SYS_C constitutes a recording medium according to the invention, which can be read by a processor and stores a computer program PROG according to the invention thereon. The computer program PROG includes instructions for performing steps of the control method according to the invention. The program PROG defines functional modules of the first control loop B1 and the second control loop B2, which depend on or control the hardware elements 2 to 5 of the previously referenced control system SYS_C.

[0084] Therefore, the first loop B1 specifically includes:

[0085] - The monitoring module MOD_B1_SUR for monitoring turbine T is configured to detect whether at least one operability limit of turbine T has been reached.

[0086] - The module MOD_B1_DET is configured to determine a corrected fuel flow setting value QCMD_CORREC if the at least one operability limit is reached. The corrected fuel flow setting value QCMD_CORREC shows a difference relative to the current fuel flow setting value, referred to as the "flow difference".

[0087] "Current fuel flow setting" refers to the applicable fuel flow setting QCMD before a correction is determined due to reaching at least one operability limit.

[0088] It should be noted that devices constructed by software and / or hardware to implement the first loop B1 are well known to those skilled in the art and therefore will not be described in further detail here. As a non-limiting example, document FR2977638A1 describes these aspects in the context of controlling fuel flow to prevent surge, or in other words, when the operability limit in question is the C / P limit.

[0089] The second loop B2 includes:

[0090] - The first determining module MOD_B2_DET1 is configured as a function to determine the torque correction amount ΔTRQ as the flow difference EC_DEB.

[0091] - The second determining module MOD_B2_DET2 is configured as a function to determine the torque setting value TRQCMD as the torque correction amount ΔTRQ.

[0092] The method for determining the torque correction amount ΔTRQ by the first determining module MOD_B2_DET1 is described in detail below with reference to several embodiments of the control method according to the present invention.

[0093] In the following description, for the sake of simplicity, a single operability limit corresponding to the C / P acceleration limit is considered, as is well known to those skilled in the art.

[0094] However, it should be noted that choosing an operability limit corresponding to the acceleration limit is only one embodiment of the invention. Other options are also possible, such as: the C / P deceleration limit, the limit relative to mechanical speed N1, the limit relative to mechanical speed N2, and the limit relative to the exhaust temperature (also known as EGT) at the inlet of the low-pressure turbine 15 of the turbine, etc.

[0095] Furthermore, it should be noted that there is no limitation on the number of limits that may be considered within the scope of this invention. Therefore, the invention applies equally when considering a single operability limit, or indeed when considering several operability limits, and some or all of these operability limits may also be of different types. Those skilled in the art will understand how to implement this invention when considering several operability limits.

[0096] Figure 4 An example of the operation of loops B1 and B2 is shown in schematic form.

[0097] like Figure 4As shown, if the C / P acceleration limit is not reached, the monitoring module MOD_B1_SUR receives the fuel setting value corresponding to the current fuel flow setting value QCMD as input; if the C / P acceleration limit is reached, it receives the fuel setting value actually corresponding to the fuel flow setting value QCMD_CORREC. The monitoring module MOD_B1_SUR also receives appropriate pressure measurements as input to determine whether the C / P acceleration limit has not been reached, particularly including the pressure P at the outlet of the high-pressure compressor 12.

[0098] As is customary, the monitoring module MOD_B1_SUR also receives an indicator as input corresponding to the rotational speed N of the rotating shaft that injects / removes torque from the motor ME. In this embodiment, this indicator corresponds to the rotational speed NHP of the high-voltage shaft 22. It is well known that the monitoring module MOD_B1_SUR uses the received speed indicator to determine whether there is an intention to enter a transient phase.

[0099] When the C / P acceleration limit is reached, the determination module MOD_B1_DET receives a signal (not shown in the figure) from the monitoring module MOD_B1_SUR as input. The determination module MOD_B1_DET also receives appropriate pressure and temperature measurements as input in order to determine the calibration setpoint QCMD_CORREC.

[0100] Assuming the operability limit considered in this case is the C / P acceleration limit, the pressure and temperature measurements received as input to the determination module MOD_B1_DET include the pressure measurement PS3 corresponding to the static pressure of the high-pressure compressor 12, the temperature measurement T25 corresponding to the total temperature at the inlet of the high-pressure compressor 12, and the temperature measurement Tstd corresponding to the standard temperature at sea level (i.e., equal to 288.15 K (Kelvin) or 15 °C (°C)). Using these measurements, the determination module MOD_B1_DET determines the correction setpoint QCMD_CORREC in a manner known per se according to the following expression:

[0101]

[0102] It should be noted that, as an alternative to this exemplary embodiment, various measured values ​​PS3, T25, and Tstd can be received as inputs to the monitoring module MOD_B1_SUR and then transmitted to the determination module MOD_B1_DET.

[0103] Furthermore, in this exemplary embodiment, it is envisioned that the correction setting value QCMD_CORREC is determined by calculating the above expression. However, it is also entirely possible to determine the correction setting value QCMD_CORREC by consulting a table, i.e., a table including grouped values, which are taken by the function of the analysis formula corresponding to the expression given above.

[0104] In a manner known per se, FADEC can generate a fuel flow correction command based on the correction setting QCMD_CORREC, which is redirected to the input of the monitoring module MOD_B1_SUR to close the first loop B1.

[0105] In addition, such as Figure 4 As shown, the first determining module MOD_B2_DET1 receives the flow difference EC_DEB determined by the determining module MOD_B1_DET as input (the flow difference EC_DEB is conventionally determined by subtracting the correction setting value QCDMD_CORREC from the current setting value QCMD). The first determining module MOD_B2_DET1 also receives the speed index provided as input to the monitoring module MOD_B1_SUR, i.e., the speed NHP in this embodiment.

[0106] In a more specific exemplary embodiment, the first determining module MOD_B2_DET1 may receive other measurements and / or indicators as input to enable the execution of different embodiments of the control method according to the invention, which are described in detail below. In any case, those skilled in the art know how to determine which measurements and / or indicators the first determining module MOD_B2_DET1 may receive as input to allow the execution of the described embodiments.

[0107] Based on the input provided to the first determining module MOD_B2_DET1, the first determining module MOD_B2_DET1 determines the torque correction amount ΔTRQ to be transmitted to the second determining module MOD_B2_DET2. Therefore, the second determining module MOD_B2_DET2 determines the torque setpoint TRQCMD as a function of the torque correction amount ΔTRQ in a manner known per se.

[0108] In a manner known to itself, FADEC can generate a torque command based on the torque setting value TRQCMD. This torque setting value TRQCMD is then redirected to close loop B2. For example, as... Figure 4As shown, the setting value TRQCMD is redirected to the input of the first determining module MOD_B2_DET1, which can then transmit the setting value TRQCMD to the second determining module MOD_B2_DET. Alternatively, the setting value TRQCMD is redirected to the input of the second determining module MOD_B2_DET2.

[0109] Figure 5 The main steps of the control method according to the present invention are shown in the form of a flowchart, which is implemented by the control system SYS_C.

[0110] like Figure 5 As shown, the control method first includes step F10 of implementing the first loop B1.

[0111] Step F10 first includes a sub-step F10_1 for monitoring turbine T. This monitoring sub-step F10_1 is implemented by the monitoring module MOD_B1_SUR of the first loop B1.

[0112] If the C / P acceleration limit is reached, the control method, more specifically, step F10 of loop B1, includes a sub-step F10_2 that determines a correction setpoint QCMD_CORREC, the difference of which relative to the current flow setpoint QCDM is represented by the flow difference EC_DEB. This determining sub-step F10_2 is implemented by the determining module MOD_B1_DET of the first loop B1.

[0113] As mentioned above, refer to Figure 4 The sub-step F10_2 is performed after the monitoring module MOD_B1_SUR transmits a signal to the determination module MOD_B1_DET, which conveys information indicating that the C / P acceleration limit has been reached in a manner known per se.

[0114] Of course, it should be noted that if the C / P acceleration limit is not reached, the sub-step F10_2 will not be executed, which means that the current setting value QCMD will not be modified.

[0115] Once the calibration setting value QCMD_CORREC is determined, the determination module MOD_B1_DET also determines the flow difference EC_DEB (sub-step F10_3), which is transmitted (sub-step F10_4) to the first determination module MOD_B2_DET1 of the second loop B2.

[0116] The control method further includes step F20, which implements the second loop B2. Step F20 follows the implementation of step F10 associated with the first loop B1. In other words, it should be noted that the implementation of the second loop B2 depends on the first loop B1, from reference... Figure 4 The components mentioned can be clearly seen.

[0117] Step F20 first includes sub-step F20_1, which determines the torque correction amount ΔTRQ as a function of the flow difference EC_DEB. Step F20_1 is implemented by the first determining module MOD_B2_DET1 of the second loop B2.

[0118] The fact that the torque correction amount ΔTRQ is determined as a function of the flow difference EC_DEB is particularly advantageous because it allows for consideration of the physical reality of the turbine T, especially its operation, regardless of its speed (transient or virtually stable). "Physical reality" here refers to the relationship between the operation of the generator ME and the actual changes in fuel flow. In other words, the thermodynamic aspects involved in the changes in fuel flow are considered when determining the amount ΔTRQ.

[0119] In one specific implementation, the torque correction amount ΔTRQ is determined according to the following expression:

[0120]

[0121] In the expression:

[0122] -FHV corresponds to the calorific value of the fuel (in J.kg). -1 express),

[0123] -C_1 is a constant.

[0124] -η corresponds to the thermal efficiency of the gas generator.

[0125] Of course, it should be understood that in this embodiment, the first determining module MOD_B2_DET1 receives the measured values / indices EC_DEB, FHV, η, C_1, and NHP as inputs in order to calculate the quantity ΔTRQ.

[0126] The expression developed by the inventors is particularly noteworthy because it allows for the determination of the quantity ΔTRQ in a simple, fast, and inexpensive manner.

[0127] To obtain this expression, it is first necessary to assume that the total available power PW_CORE at the gas generator outlet can be calculated according to the following expression:

[0128]

[0129] In the expression:

[0130] -W corresponds to the air flow rate at the high-pressure rotor inlet (in kg·s⁻¹). -1 express),

[0131] -Δh_CORE_EXIT corresponds to the enthalpy (in J.kg) available for generating work at the gas generator outlet. -1 express),

[0132] -V0 corresponds to flight speed.

[0133] -PW_OFF_TAKE corresponds to the power extracted in the form of air and / or mechanical energy removed from the high-pressure rotor.

[0134] Therefore, according to the following expression, the power generated by the gas generator can be associated with the chemical power related to fuel use:

[0135]

[0136] In the expression, Wff corresponds to the fuel flow rate (in kg·s). -1 express).

[0137] The subsequent fuel flow rate change ΔWff can be correlated with the motor power change ΔP_ME using the following expression:

[0138]

[0139] The constant C_2 is introduced here to allow the ΔWff value provided by this formula to be adjusted using a value obtained by another method, such as by an experiment performed on a test bench or by a value actually obtained through digital simulation.

[0140] Assuming that the power change ΔP_ME of motor ME is equal to the product of ΔTRQ and the rotational speed of high-voltage shaft 22, the expression for ΔTRQ can be derived from the latter expression of ΔWff, which is usually expressed as a function of NHP.

[0141] It should be noted that in the above expression, the change in fuel flow rate ΔWff corresponds precisely to the flow difference EC_DEB.

[0142] The efficiency η of a gas generator can be expressed in different ways. For example, the efficiency η can be expressed in the following form:

[0143]

[0144] In the expression:

[0145] -M0 corresponds to Mach speed.

[0146] -γ corresponds, in a manner known per se, to the ratio between isobaric heat capacity and isochoric heat capacity.

[0147] -OPR corresponds to the total pressure rate of the gas generator.

[0148] The choice of efficiency η expressed by the formula given above is only one embodiment of the present invention. For example, other variations can be conceived, considering that the parameter OPR is replaced by the temperature ratio T3 / T2, where T3 and T2 correspond to the outlet temperature of the high-pressure rotor and the inlet temperature of the main flow, respectively.

[0149] A constant efficiency η can also be considered, especially since the fluctuation of the efficiency η is very small except at idle speed. Therefore, in another specific embodiment, the torque correction amount ΔTRQ is determined according to the following expression:

[0150]

[0151] In the expression, C'_1 is a constant.

[0152] Therefore, the constant C'_1 includes not only the aforementioned constant C_1, but also the efficiency value η, which is considered constant in this case.

[0153] The control method then includes a sub-step F20_2 that determines the torque setpoint TRQCMD as a function of the torque correction amount ΔTRQ. This determination sub-step F20_2 is implemented by the determination module MOD_B2_DET2 of the second loop B2.

[0154] The determination of the torque setting value TRQCMD is performed in a manner known per se. Specifically, a previous torque setting value observed before determining the torque correction amount ΔTRQ can be considered, meaning that the newly determined torque setting value TRQCMD corresponds to the old torque setting value to which the torque correction amount ΔTRQ was applied.

Claims

1. A method for controlling a turbomachine (T) comprising a gas generator comprising a combustion chamber (13), a low-pressure rotating shaft (21) and a high-pressure rotating shaft (22), the turbomachine comprising at least one electric machine (ME) forming a device for injecting / removing torque to one of the rotating shafts, the method comprising a step (F10) of implementing a fuel control loop (Bl) to determine a fuel flow setpoint (QCMD) into the combustion chamber, said step comprising: - monitoring (F10_1) the turbomachine to detect if at least one operability limit of the turbomachine is reached, - if the at least one operability limit is reached, determining (F10_2) a corrected fuel flow setpoint (QCMD_CORREC) exhibiting a difference with respect to the current fuel flow setpoint (QCMD), called "flow difference" (EC_DEB), the method further comprising a step (F20) of implementing a torque control loop (B2) to determine a torque setpoint (TRQCMD) of the at least one electric machine, said step comprising determining (F20_1) a torque correction (ATRQ) as a function of the flow difference, the torque setpoint being determined (F20_2) as a function of the torque correction.

2. The method of claim 1, wherein, the torque correction (ATRQ) is determined as equal to: in which: - EC_DEB corresponds to the flow difference, - FHV corresponds to the heat value of the fuel, - N corresponds to the rotational speed of the rotating shaft on which the at least one electric machine (ME) injects / removes torque, - C_1 is a constant, - η corresponds to the efficiency of the gas generator.

3. The method of claim 2, wherein, the efficiency of the gas generator η is expressed in the form: in which: - M corresponds to the Mach speed, - γ corresponds to the ratio between the isobaric heat capacity and the isochoric heat capacity, - OPR corresponds to the overall pressure ratio of the gas generator.

4. The method of claim 1, wherein, the torque correction (ATRQ) is determined according to the following expression: in which: - EC_DEB corresponds to the flow difference, - FHV corresponds to the heat value of the fuel, - N corresponds to the rotational speed of the rotating shaft on which the at least one electric machine (ME) injects / removes torque, - C'_1 is a constant.

5. The method according to any one of claims 1 to 4, characterized in that, the at least one operability limit corresponds to any one of the following parameters: - C / P limit, - limit with respect to the mechanical speed N1, - limit with respect to the mechanical speed N2, - limit with respect to the exhaust temperature at the inlet of the low-pressure turbine (15) of the turbomachine.

6. A computer program comprising instructions for implementing the control method according to any one of claims 1 to 5, when said computer program is run by a computer.

7. A computer-readable recording medium on which the computer program according to claim 6 is saved.

8. A control system (SYS_C) for controlling a turbomachine (T) comprising a gas generator comprising a combustion chamber (13), a low-pressure rotating shaft (21) and a high-pressure rotating shaft (22), said turbomachine comprising at least one electric machine (ME) forming a device for injecting / removing torque to / from one of said rotating shafts, said control system comprising a fuel control loop for determining a fuel flow setpoint (QCMD) into the combustion chamber, said fuel control loop comprising: - a monitoring module (MOD_B1_SUR) for monitoring said turbomachine configured to detect whether at least one operability limit of said turbomachine is reached, - a determination module (MOD_B1_DET) configured to determine a corrected fuel flow setpoint (QCMD_CORREC) if said at least one operability limit is reached, said corrected fuel flow setpoint exhibiting a difference with respect to a current fuel flow setpoint (QCMD), called "flow difference" (EC_DEB), said control system further comprising a torque control loop (B2) for determining a torque setpoint (TRQCMD) of said at least one electric machine, said torque control loop comprising: - a first determination module (MOD_B2_DET1) configured to determine a torque correction (ATRQ) as a function of said flow difference, - a second determination module (MOD_B2_DET2) configured to determine said torque setpoint as a function of said torque correction.

9. A turbomachine (T) comprising a gas generator comprising a combustion chamber (13), a low-pressure rotating shaft (21) and a high-pressure rotating shaft (22), said turbomachine comprising at least one electric machine (ME) forming a device for injecting / removing torque to / from one of said rotating shafts, and a control system (SYS_C) according to claim 8.

10. An aircraft comprising a turbomachine (T) according to claim 9.

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