Method for controlling a turbine engine comprising an electric machine

Abstract

The invention relates to a control method for controlling a turbine engine (100) comprising an electric machine (ME) forming a torque injection device on a low-pressure rotary shaft and / or a low-pressure rotary shaft, the control method comprising steps of determining a setpoint fuel flow rate (WFtr), if the setpoint fuel flow rate (WFtr) is higher than a maximum fuel flow rate (WFmax) by a difference amount (ΔWF), limiting the setpoint fuel flow rate (WFtr) to the maximum fuel flow rate (WFmax), determining a control fuel flow rate (WFcmd) on the basis of the setpoint fuel flow rate (WFtr) for supplying the combustion chamber and determining a control torque (TRQcmd) according to the difference amount (ΔWF) for the electric machine (ME).

Description

Method for controlling a turbomachine comprising an electric machine

[0001] The present invention relates to an aircraft turbomachine, in particular, the control of a turbomachine to provide the desired thrust as a function of the position of the aircraft pilot's control lever.

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

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

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

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

[0006] With reference to the diagram, a turbomachine 100 of the twin-spool, twin-flow turbojet type for aircraft is schematically represented. As is known, the turbomachine 100 comprises, from upstream to downstream in the direction of gas flow, a fan 110, a low-pressure compressor 111, a high-pressure compressor 112, a combustion chamber 113 which receives a fuel flow rate WF, a high-pressure turbine 114, a low-pressure turbine 115, and a primary exhaust nozzle 116. The low-pressure (LP) compressor 111 and the low-pressure turbine 115 are connected by a low-pressure shaft 121 and together form a low-pressure casing. The high-pressure (HP) compressor 112 and the high-pressure turbine 114 are connected by a high-pressure shaft 122 and together, with the combustion chamber, form a high-pressure casing. The blower 110, which is driven by the shaft BP 121, compresses the ingested air.The turbomachine 100 includes a metering system which provides the fuel flow WF following the receipt of a control fuel flow WFcmd.

[0007] The design of a turbomachine 100 requires taking into account a sufficient margin against the so-called surge phenomenon. This phenomenon, which results from an excessive impact of the airflow on the blades of one of the compressors, leads to significant and rapid pressure fluctuations downstream of the affected compressor and can cause combustion chamber 113 to shut down. It also generates significant shocks on the compressor blades and can thus lead to mechanical damage. It is therefore particularly important to prevent its occurrence.

[0008] With reference to the, in order to improve the operability of a turbomachine 100, it has been proposed to provide at least one electric machine ME on the high pressure shaft 122 of the turbomachine 100 so as to inject a torque on the high pressure rotation shaft 122 and thus move away from the pumping limits of the turbomachine 100.

[0009] The turbomachine 100 includes a control unit 200 configured to determine a torque command TRQcmd for the electric motor ME and a fuel flow command WFcmd for a metering system. The control unit 200 implements control instructions to optimize several parameters of the turbomachine 100 (pumping margin, exhaust temperature, etc.). The control unit 200 performs a regulatory function.

[0010] As is known, to modify the low-pressure N1 regime, that of the low-pressure shaft 121 of the turbomachine 100, the aircraft pilot changes the position of a control lever to define a control regime N1cmd. To meet the aircraft manufacturers' specifications, the low-pressure N1 regime must follow an acceleration trajectory to reach the control low-pressure N1cmd regime after a predetermined acceleration time of approximately 10 seconds. In practice, to control the low-pressure N1 regime, the high-pressure N2 regime, that of the high-pressure shaft 122 of the turbomachine 100, is modified to follow an acceleration trajectory of the high-pressure N2cmd regime.

[0011] As is known, the ECU 200 is configured to control the electric motor ME to reduce acceleration time. In practice, the performance of the turbomachine 100 decreases over time, and it can no longer receive the same maximum fuel flow rate. Specifically, the ECU 200 includes a limit switch management module, also called the C / P limit switch, which determines a maximum fuel flow rate value WFmax based on an estimate of the wear on the turbomachine 100.

[0012] With reference to Figure 1, a first control strategy is shown in which the electric motor ME provides a low torque TRQ during the acceleration of the turbomachine 100, as illustrated in curve 2d. In this case, the turbomachine 100 has reduced performance, and the fuel flow rate WF coincides with the maximum fuel flow rate WFmax of the turbomachine 100 (which is reduced due to wear). Curve 2a shows that the turbomachine 100 can only reach the low-pressure control speed N1cmd after an acceleration time of approximately 12 seconds, i.e., with a 2-second delay. The high-pressure speed N2 exhibits lag (curve 2b) compared to the high-pressure control speed N2cmd.

[0013] To achieve the desired operating speed within the allotted time, an alternative control strategy was proposed in which the electric machine ME provides a higher electrical torque TRQ. This electrical torque TRQ is calculated by a MISO (Multiple Input Single Output) type multivariable controller, which optimizes the injection of electrical torque to accelerate the turbomachine 100.

[0014] Referring to curve 3d, a significant torque TRQ is supplied by the electric machine ME to accompany the acceleration trajectory. The low-pressure control regime N1cmd is reached within the allotted time (curve 3a), and the high-pressure regime N2 exhibits no drag (curve 3b). The fuel flow rate WF does not reach the maximum fuel flow rate WFmax (curve 3c).

[0015] Such a control strategy for the electric motor meets the aircraft manufacturer's needs but requires the electric motor to deliver a high torque (TRQ) for a significant duration, particularly during takeoff. Consequently, it is necessary to design a large-sized electric motor to provide the required torque, as well as large power sources, such as batteries, which significantly increases both cost and size.

[0016] The invention aims to eliminate at least some of these drawbacks.

[0017] Incidentally, documents WO2023281202A1 and US2021172384A1 are known to describe aircraft turbomachinery including an electric machine to compensate for energy loss on the low-pressure shaft and to participate in a demand for increased thrust. PRESENTATION OF THE INVENTION

[0018] The invention relates to a method for controlling a turbomachine comprising a blower positioned upstream of a gas generator and defining a primary flow and a secondary flow, said gas generator being traversed by the primary flow and comprising a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine, said low-pressure turbine being connected to said low-pressure compressor by a low-pressure rotation shaft and said high-pressure turbine being connected to said high-pressure compressor by a high-pressure rotation shaft, the turbomachine comprising an electric machine forming a torque injection device on the low-pressure rotation shaft and / or the low-pressure rotation shaft, control method comprising steps consisting of: Determining a setpoint fuel flow rate,If the target fuel flow rate is greater than the maximum fuel flow rate by a certain difference, limit the target fuel flow rate to the maximum fuel flow rate, determine a control fuel flow rate from the target fuel flow rate to supply the combustion chamber, and determine a control torque based on the difference for the electric motor.

[0019] Thanks to this invention, the energy from fuel combustion is used optimally while respecting the maximum fuel flow rate. If acceleration is insufficient, electric assistance is dynamically provided to compensate for the acceleration deficit. Thus, electric assistance is used sparingly and only when necessary, avoiding the need for high-capacity electrical sources, particularly electric batteries. The faster dynamics of electric power compared to fuel are taken advantage of. The fuel supply is prioritized.

[0020] According to one aspect, the control process includes steps consisting of: if the setpoint fuel flow is less than the maximum fuel flow, Determine a control fuel flow from the setpoint fuel flow to supply the combustion chamber, Determine a zero-value control torque for the electric machine.

[0021] Thus, no electrical assistance is provided if the target fuel flow rate is sufficient. This limits electrical consumption. Consequently, this strategy allows the electric machine to be used only when necessary. In other words, electrical assistance is used progressively and proportionally to the turbomachine's degradation, i.e., the loss of C / P margin.

[0022] According to one aspect, the control process includes a step consisting of determining the control fuel flow rate from the setpoint fuel flow rate by implementing a control loop.

[0023] A control loop makes it possible to meet operability criteria while ensuring optimal regulation of the combustion chamber.

[0024] The invention also relates to a computer program comprising instructions for executing the steps of a control process as previously described when said program is executed by a computer.

[0025] The invention also relates to a turbomachine computer comprising a memory including instructions from a computer program as previously described.

[0026] The invention also relates to a turbomachine comprising a blower positioned upstream of a gas generator and defining a primary flow and a secondary flow, said gas generator being traversed by the primary flow and comprising a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine, said low-pressure turbine being connected to said low-pressure compressor by a low-pressure rotation shaft and said high-pressure turbine being connected to said high-pressure compressor by a high-pressure rotation shaft, the turbomachine comprising an electric machine forming a torque injection device on the low-pressure rotation shaft and / or the low-pressure rotation shaft, the turbomachine comprising a computer configured to: Determine a target fuel flow rate,If the target fuel flow rate is greater than the maximum fuel flow rate by a certain difference, limit the target fuel flow rate to the maximum fuel flow rate. Determine a control fuel flow rate from the target fuel flow rate to supply the combustion chamber. Determine a control torque based on the difference for the electric motor.

[0027] According to one aspect, the turbomachine includes a fuel setpoint determination module configured to determine a setpoint fuel flow rate comprising: an acceleration trajectory calculation unit configured to determine a setpoint speed based on a control lever position, a comparison unit configured to determine a speed deviation by comparing the setpoint speed and a speed measurement provided by the turbomachine, and a correction unit configured to determine the setpoint fuel flow rate based on the speed deviation and parameters related to the turbomachine.

[0028] Advantageously, the fuel setpoint is calculated to take into account the acceleration trajectory in order to avoid any risk of turbomachine pumping.

[0029] The invention also relates to an aircraft comprising a turbomachine as previously described. PRESENTATION OF THE FIGURES

[0030] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0031] This is a schematic representation of a turbomachine according to the prior art.

[0032] This is a schematic representation of the acceleration of a turbomachine with low-value electrical assistance from the electric machine.

[0033] This is a schematic representation of the acceleration of a turbomachine with high-value electrical assistance from the electric machine.

[0034] This is a schematic representation of a computer for controlling a turbomachine.

[0035] This is a schematic representation of the acceleration of a turbomachine with electrical assistance according to an example of implementation of the invention.

[0036] It should be noted that the figures explain the invention in detail for implementing the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention belongs to the field of regulation and control of the operation of a turbomachine comprising a gas generator.

[0038] For the remainder of this description, we will consider, without limitation, a turbomachine of the twin-spool, turbofan engine type for aircraft, such as a civil aircraft capable of carrying passengers. The invention remains applicable regardless of the type of turbomachine considered, provided that the latter includes a gas generator, for example, a turboshaft engine, a turboprop engine, etc.

[0039] Furthermore, the invention remains applicable to all types of aircraft (airplane, helicopter, etc.), but, more broadly, to all types of industrial machines equipped with a turbomachine according to the invention.

[0040] As presented in the preamble, with reference to the diagram, a turbomachine 100 of the twin-spool, twin-flow turbojet type for aircraft is schematically represented. As is known, the turbomachine 100 comprises, from upstream to downstream in the direction of gas flow, a fan 110, a low-pressure compressor 111, a high-pressure compressor 112, a combustion chamber 113 which receives a fuel flow WF via a high-pressure turbine 114, a low-pressure turbine 115, and a primary exhaust nozzle 116. The low-pressure (LP) compressor 111 and the low-pressure turbine 115 are connected by a low-pressure shaft 121 and together form a low-pressure casing. The high-pressure (HP) compressor 112 and the high-pressure turbine 114 are connected by a high-pressure shaft 122 and together, with the combustion chamber, form a high-pressure casing. The blower 110, which is driven by the shaft BP 121, compresses the ingested air.The turbomachine 100 includes a metering system which provides the fuel flow WF following the receipt of a control fuel flow WFcmd.

[0041] The design of a turbomachine 100 requires taking into account a sufficient margin against the so-called surge phenomenon. This phenomenon, which results from an excessive impact of the airflow on the blades of one of the compressors, leads to significant and rapid pressure fluctuations downstream of the affected compressor and can cause the combustion chamber 113 to shut down. It also generates significant shocks on the compressor blades and can thus lead to mechanical damage. It is therefore particularly important to avoid its occurrence. With reference to [reference missing], in order to improve the operability of a turbomachine 100, it has been proposed to include at least one electric machine ME on the high-pressure shaft 122 of the turbomachine 100 in order to inject torque onto the high-pressure rotation shaft 122 and thus mitigate the surge limits of the turbomachine 100.

[0042] For the remainder of this description, it is assumed, without limitation, that the turbomachine 100 comprises a single electric machine ME and that the rotational shaft on which torque is injected / received by the electric machine ME is the high-pressure shaft 122. However, nothing precludes considering that the rotational shaft on which this single electric machine ME acts is the low-pressure shaft 121. Nor does anything preclude considering that the turbomachine 100 comprises a plurality of electric machines ME capable of injecting / receiving torque on a single one of said shafts or even on separate shafts.

[0043] Thus, the electric machine ME is configured, according to a first operating mode, to generate torque capable of driving the high-pressure shaft 122. Conventionally, such a first operating mode corresponds to a "motor operating mode." The electric machine ME is also configured, according to a second operating mode, to generate torque capable of extracting mechanical energy from the high-pressure shaft 122. This extracted energy can, for example, be used to power at least one electrical component of the turbomachine 100. Again, conventionally, such a second operating mode corresponds to a "generator operating mode." Those skilled in the art can refer to document WO2016 / 020618 regarding the design and implementation of such an electric machine ME for a turbomachine; these aspects are therefore not detailed further here.

[0044] The turbomachine 100 includes a control unit 200 configured to determine a torque command TRQcmd for the electric machine ME and a fuel flow command WFcmd for a metering system. The control unit 200 performs a regulatory function. It implements control instructions to optimize several parameters of the turbomachine 100 (pumping margin, exhaust temperature, etc.).

[0045] As is known, to modify the low-pressure N1 regime, that of the low-pressure shaft 121 of the turbomachine 100, the aircraft pilot changes the position of a control lever to define a control regime N1cmd. To meet the aircraft manufacturers' specifications, the low-pressure N1 regime must follow an acceleration trajectory to reach the control low-pressure N1cmd regime after a predetermined acceleration time, for example, on the order of 10 seconds. In practice, to control the low-pressure N1 regime, the high-pressure N2 regime, that of the high-pressure shaft 122 of the turbomachine 100, is modified to follow an acceleration trajectory of the high-pressure N2cmd regime.

[0046] With reference to the, a method of controlling the turbomachine 100 is shown. In this example, the turbomachine 100 provides the computer 200 with a plurality of MES measurements, in particular, the position of the control lever, the low pressure speed N1, the high pressure speed N2, the electrical torque TRQ, the fuel flow WF.

[0047] These MES measurements can also correspond to physical quantities, for example, pressure measurements, shaft rotation speed, or aircraft speed. Furthermore, the acquisition means configured to acquire these physical quantities include, as is known, an acquisition chain comprising a sensor dedicated to measuring each of these quantities. Generally, the configuration of such acquisition means is well known to those skilled in the art and is therefore not detailed further here. In addition, those skilled in the art will also be able to determine which physical quantities need to be measured in order for the control method according to the invention to be implemented, with regard to the implementation methods described below for the control method according to the invention.

[0048] With reference to the, computer 200 is represented schematically for the control and regulation of the turbomachine 100. Computer 200 includes a stop management module 1, also called C / P stop, which determines a maximum fuel flow WFmax which is a function of an estimate of the wear of the turbomachine 100 from the different MES measurements of the turbomachine 100.

[0049] The computer 200 further includes a fuel setpoint determination module 2 configured to determine a setpoint fuel flow rate WFtr. In this example, the fuel setpoint determination module 2 includes an acceleration trajectory calculation unit 21 configured to determine a high-pressure speed setpoint N2CS as a function of the control lever position, a comparison unit 22 configured to determine a speed deviation dN2 by comparing the high-pressure speed setpoint N2CS and a high-pressure speed N2 supplied by the turbomachine 100, and a correction unit 23, known to the person skilled in the art, configured to determine the setpoint fuel flow rate WFtr as a function of the speed deviation dN2 and parameters related to the turbomachine 100, in particular, the operability limits.

[0050] According to the invention, the fuel setpoint determination module 2 further comprises a limiting unit 24 configured to limit the setpoint fuel flow rate WFtr to the maximum fuel flow rate WFmax, thereby providing a control fuel flow rate WFcmd. Thus, the control fuel flow rate WFcmd is always determined to be as high as possible while respecting the maximum fuel flow rate WFmax. This ensures trajectory tracking by fully utilizing the energy from fuel combustion. In other words, it minimizes the need for electric assistance, as will be explained later.

[0051] The ECU 200 includes a control module 3 configured to determine a CD metering command from the WFcmd control fuel flow rate. In this example, the fuel control module 3 implements a control loop to determine a CD metering command for a fuel metering system, specifically one comprising one or more fuel metering units. The CD metering command results from nested control loops.

[0052] According to the invention, the calculator 200 includes a setpoint torque determination module 4 configured to determine a setpoint torque TRQtr from the setpoint fuel flow WFtr and the maximum fuel flow WFmax.

[0053] The setpoint torque determination module 4 includes a comparator unit 41 configured to determine a deviation magnitude ΔWF by comparing the setpoint fuel flow rate WFtr and the maximum fuel flow rate WFmax.

[0054] The torque setpoint determination module 4 includes a calculation unit 42 configured to calculate a torque setpoint TRQtr as a function of the error magnitude ΔWF. Preferably, the torque setpoint TRQtr is determined from a database, mathematical functions, correction algorithms, or nomograms, known to a person skilled in the art, so that the torque setpoint TRQtr compensates for the fuel deficit, i.e., the error magnitude ΔWF. The torque setpoint TRQtr is thus defined to compensate for any drag by providing dynamically defined electric assistance.

[0055] With reference to the, the computer 200 includes a filtering module 5 configured to cancel the setpoint torque TRQtr if it is not positive. In other words, during an acceleration of the turbomachine 100, the electric machine ME is configured to operate only as a "motor".

[0056] The TRQcmd control torque is transmitted to the ME electric machine which generates the required TRQ torque.

[0057] With reference to the, a control strategy for the turbomachine 100 is represented according to one embodiment of the invention.

[0058] In this case, the turbomachine 100 has reduced performance and its maximum fuel flow rate WFmax is reduced due to wear. The maximum fuel flow rate WFmax is determined by the stop management module 1 as illustrated in the figure.

[0059] In curve 5a, we observe that the low-pressure N1 regime of the turbomachine 100 can reach the control low-pressure N1cmd regime after an acceleration time of approximately 10 seconds, i.e., without any delay. The high-pressure N2 regime exhibits no lag (curve 5b) compared to the control high-pressure N2cmd regime.

[0060] As a reminder, the fuel flow rate WF reaches the maximum fuel flow rate WFmax for a turbomachine 100 with reduced performance due to its degradation.

[0061] Referring to curve 5c, it is advantageous to observe that the fuel flow rate WF reaches the maximum fuel flow rate WFmax. This is due to the comparison unit 24 being configured to limit the setpoint fuel flow rate WFtr to the maximum fuel flow rate WFmax. Thus, the energy associated with fuel combustion is fully utilized.

[0062] Referring to curve 5d, the TRQ torque supplied by the electric machine ME remains low and is used only as a supplement to the fuel. As illustrated in curve 5d, the TRQ torque varies dynamically to precisely meet the demand beyond the maximum fuel flow rate WFmax. An electric machine ME can accommodate this real-time adaptation without constraint. Such operation contradicts prior art, which aimed to provide a substantially constant electrical torque during acceleration.

[0063] Thanks to the invention, the ME electric machine is used sparingly to allow optimal trajectory tracking during acceleration, ensuring the operability of the turbomachine 100, guaranteeing an acceleration time in accordance with aircraft manufacturers' guidelines while limiting the use of electrical resources.

Claims

Method of controlling a turbomachine (100) comprising a blower (110) positioned upstream of a gas generator and delimiting a primary flow and a secondary flow, said gas generator being traversed by the primary flow and comprising a low-pressure compressor (111), a high-pressure compressor (112), a combustion chamber (113), a high-pressure turbine (114) and a low-pressure turbine (115), said low-pressure turbine (115) being connected to said low-pressure compressor (111) by a low-pressure rotation shaft (121) and said high-pressure turbine (114) being connected to said high-pressure compressor (112) by a high-pressure rotation shaft (122), the turbomachine (100) comprising an electric machine (EM) forming a torque injection device on the low-pressure rotation shaft (121) and / or the high-pressure rotation shaft (122),control method comprising steps of: Determining a setpoint fuel flow rate (WFtr), if the setpoint fuel flow rate (WFtr) is greater than a maximum fuel flow rate (WFmax) by a difference (ΔWF), Limiting the setpoint fuel flow rate (WFtr) to the maximum fuel flow rate (WFmax), Determining, by implementing a control loop, a control fuel flow rate (WFcmd) from the setpoint fuel flow rate (WFtr) to supply the combustion chamber (113), and Determining a control torque (TRQcmd) as a function of the difference (ΔWF) for the electric machine (ME), or if the setpoint fuel flow rate (WFtr) is less than the maximum fuel flow rate (WFmax), Determining, by implementing a control loop, a control fuel flow rate (WFcmd) from the setpoint fuel flow rate (WFtr) to supply the combustion chamber (113),Determine a control torque (TRQcmd) of zero value for the electrical machine (ME). Computer program comprising instructions for executing the steps of a control method according to claim 1 when said program is executed by a computer. Computer (200) for turbomachine (100) comprising a memory including instructions of a computer program according to claim 2. Turbomachine (100) comprising a blower (110) positioned upstream of a gas generator and delimiting a primary flow and a secondary flow, said gas generator being traversed by the primary flow and comprising a low pressure compressor (111), a high pressure compressor (112), a combustion chamber (113), a high pressure turbine (114) and a low pressure turbine (115), said low pressure turbine (115) being connected to said low pressure compressor (111) by a low pressure rotation shaft (121) and said high pressure turbine (114) being connected to said high pressure compressor (112) by a high pressure rotation shaft (122), the turbomachine (100) comprising an electric machine (EM) forming a torque injection device on the low pressure rotation shaft (121) and / or the high pressure rotation shaft (122), the turbomachine (100) comprising a computer (200) according to claim 3. Turbomachine (100) according to claim 4 comprising a fuel setpoint determination module (2) configured to determine a setpoint fuel flow (WFtr) comprising: an acceleration trajectory calculation unit (21) configured to determine a setpoint speed (N2CS) as a function of a control lever position, a comparison unit (22) configured to determine a speed deviation (dN2) by comparing the setpoint speed (N2CS) and a speed measurement (N2) provided by the turbomachine (100) and a correction unit (23) configured to determine the setpoint fuel flow (WFtr) as a function of the speed deviation (dN2) and parameters related to the turbomachine (100). Aircraft comprising a turbomachine (100) according to any one of claims 4 to 5.

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