Method for managing the torque of a turbomachine

Abstract

A method for managing the torque of an aircraft turbomachine comprising a fan (6) or a variable-pitch propeller connected to a turbine (5) by a shaft (7) and a reduction gear (8), and an electric generator (9) connected to the shaft (7), the method comprising the following steps: measuring the torque on the shaft (7) from a torque sensor (10); when a torque peak is measured by the torque sensor (10), calculating a braking setpoint for the turbine (5) by a control system based on the measured torque; and in response to the braking setpoint, adjusting by the control system a resistance (11) of a dissipative load (12) for drawing electrical power from the electric generator (9) to the dissipative load (12). Figure for the abstract: Fig 1

Description

Description Title of the invention: Method for managing the torque of a tur- bomachine technical field

[0001] — The present invention relates, in general, to turbomachinery for aircraft, and in particular turbomachinery equipped with a fan or a propeller variable pitch connected to a turbine via a shaft and a gearbox and, more specifically, the management of torque peaks occurring during the operation of such turbomachinery.

[0002] = More particularly, the invention relates to a method for managing torque of a turbomachine comprising a turbine connected to a blower or a propeller variable timing via a shaft and a reducer. State of the art

[0003] The occurrence of torque peaks during the operation of a turbomachine comprising a blower or variable-pitch propeller, connected to a turbine by The intermediary of a shaft and a reducer is detrimental to the reducer. Indeed, torque peaks have an impact on the mechanical strength of its components, in in particular gears, bearings and structural parts.

[0004] — To withstand torque peaks, the reducer can be resized. The teeth can be reinforced, the bearings increased in size and number of elements rolling bearings, and thickened structural parts to ensure the reliability of the reducer.

[0005] — However, this has the consequence of significantly increasing the mass of the reducer, which is incompatible with current efforts to reduce the mass of an aircraft.

[0006] One solution to avoid increasing the mass of the reducer is to predict and detect the appearance of torque peaks in order to lower the average torque level seen by the reducer just before the occurrence of the torque peak. This detection, prediction and The average torque decrease is classically calculated from a torque measurement on the shaft on which the gearbox and turbine are mounted, as well as a timing control, that is to say, the angle of inclination of the blades of the blower or the pitch propeller variable.

[0007] …— Nevertheless, the torque peaks persist. The response time of the timing control is not sufficient to reject the most rapid disturbances on the couple related to va- aircraft sampling variations and variations in angle of attack and Mach number, particularly during takeoff and climb. Description of the invention The invention therefore aims to remedy these drawbacks and to propose a method for reducing the torque of a turbomachine turbine connected via a shaft and a reducer to a blower or a variable pitch propeller when a torque peak occurs, and this in a sufficiently short time to reduce the torque transmitted to the reducer and protect the latter, without it being necessary to resize and increase the mass of the turbomachine. A method for managing the torque of an aircraft turbomachine is therefore proposed, comprising a fan or variable-pitch propeller connected to a turbine by a shaft and a reduction gear, and an electric generator connected to the shaft, the method comprising the following steps: the measurement of torque on the shaft from a torque sensor; When the occurrence of a torque peak is measured by the torque sensor, a turbine braking setpoint is calculated by a control system based on the measured torque; and In response to the braking command, the control system adjusts the resistance of a dissipative load to draw electrical power from the electric generator to the dissipative load. Advantageously, the braking setpoint can be calculated based on the difference between the measured torque and a maximum torque setpoint. Preferably, the braking setpoint is calculated based on the thermal capacity of the dissipative load. According to one implementation method, the dissipative load can be formed by the electric generator and the resistance is the internal resistance of the electric generator constituted by its winding. Preferably, when electrical power is drawn by the internal resistance of the electric generator, the electric generator is short-circuited from the aircraft's electrical network. Preferably, a control of the fan or variable pitch propeller pitch is carried out by the control system in parallel with the adjustment of the dissipative load resistance. The invention also relates to an aircraft turbomachine comprising a fan or variable-pitch propeller connected to a turbine by a shaft and a reduction gear, and an electric generator connected to the shaft, the turbomachine comprising: a torque sensor configured to measure the torque on the shaft; a control system configured to calculate a turbine braking setpoint when a torque peak is measured by the torque sensor, and configured to adjust the resistance of a dissipative load in response to the setpoint braking for the extraction of electrical power from the electric generator to the dissipative load. Preferably, the control system is configured to calculate the braking setpoint based on the thermal capacity of the dissipative load. According to one embodiment, the dissipative load can be formed by the electric generator. Advantageously, the control system can include an electric generator computer configured to calculate the braking setpoint and adjust the internal resistance of the electric generator in response to the braking setpoint. The invention also relates to an aircraft comprising at least one turbomachine as previously described. Brief description of the drawings Other goals, advantages, and characteristics will become apparent from the following description, given for illustrative purposes only and with reference to the attached drawings, on which: [Fig.1] schematically illustrates an aircraft turbomachine according to one embodiment of the invention. [Fig.2] schematically illustrates an electric generator connected to a dissipative load of a turbomachine according to an embodiment of the invention. [Fig.3] illustrates a braking logic according to one embodiment of the invention. [Fig.4] illustrates a logic of protection against overheating of the dissipative load according to an embodiment of the invention. Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more". Detailed description of a method of implementation Figure [Fig. 1] schematically illustrates an aircraft turbomachine. In the illustrated example, the turbomachine comprises a high-pressure body 2 with a high-pressure compressor and a high-pressure turbine, and a low-pressure body 3 with a low-pressure compressor 4 and a low-pressure turbine 5. The low-pressure body 3 is connected to a blower 6 via a shaft 7 and a reducer 8. Alternatively, the blower 6 can be replaced by a variable pitch propeller. In addition, an electric generator 9 connected to the shaft 7 is arranged downstream of the low pressure turbine 5 and comprises a rotor 9a and a stator 9b. It may be foreseen that the electric generator 9 is located upstream of the low pressure turbine 5, for example on the periphery of the blower 6. The turbomachine 1 includes a torque sensor 10 configured to measure the torque on the shaft 7, advantageously the torque at the input of the gearbox 8, or the torque between the fan 6 and the output of the gearbox 8, or between the low-pressure compressor 4 and the low-pressure turbine 5. The turbomachine 1 also includes a control system configured to calculate a braking setpoint for the low-pressure turbine 5 when the occurrence of a torque peak is measured by the torque sensor 10. By braking instruction, we mean a torque limitation instruction between the turbine, in this example the low pressure turbine 5, and the blower 6. In addition, the control system is configured to adjust the resistance 11 of a dissipative load 12, visible in [Fig.2]. Preferably, the resistance 11 is a variable resistance. In particular, the control system is capable of adjusting the torque on the shaft 7 of the low-pressure body 3 according to the braking setpoint so as to draw part of the electrical power from the electric generator 9 to the dissipative load 12. In the illustrated example, the control system includes a regulation computer 13 configured to calculate the braking setpoint and a torque control computer 14 configured to adjust the resistance 11 of the dissipative load 12. The control unit 13 is connected to the torque sensor 10 and the torque control unit 14 by an electrical link, which can be analog or digital. Preferably, the control computer 13 is configured to control the timing of the blower 6. According to another embodiment, the dissipative charge 12 can be formed by the electric generator 9. In this case, the control system can be expected to include a generator control unit (GCU) configured to calculate the braking setpoint and adjust the internal resistance of the generator in response to that setpoint. The internal resistance, or short-circuit resistance, of the generator allows electric current to flow through the windings, thus transforming power into thermal energy dissipated by the windings. The invention also relates to a method for managing the torque of the aircraft turbomachine 1 comprising measuring the torque on the shaft 7 from the torque sensor 10. In the illustrated example, the torque considered is the drive torque of the low-pressure body 3 transmitted by the shaft 7. Preferably, the torque on shaft 7 is measured continuously during operation of the turbomachine 1. When the occurrence of a torque peak is measured by the torque sensor 10, a braking command for the low-pressure turbine 5 is calculated by the control system from the measured torque. The occurrence of a torque peak can be detected by measuring a torque disturbance, such as a transient phenomenon, by the torque sensor 10. A torque peak is defined as a sudden increase in torque beyond a maximum threshold value. As illustrated in [Fig.2], in the illustrated example, the braking command is calculated by the control computer 13 and then communicated to the torque control computer 14. In response to the braking command, the torque control computer 14 adjusts the resistance 11 of the dissipative load 12 so that part of the electrical power of the electric generator 9 is dissipated to the dissipative load 12. The current dissipation of the electric generator 9 through the dissipative load 12 results in a limitation of the torque of the low pressure turbine 5. The low-pressure turbine 5 drives the blower 6 via the shaft 7 so that limiting the torque of the low-pressure turbine 5 reduces the torque of the blower 6 and, consequently, reduces the torque transmitted to the reducer 8. The maximum torque setpoint, advantageously fixed, is determined according to the limits of the reducer 8 in order to optimize its lifespan. In the illustrated example, the control system includes a proportional integral differential regulator, also known as a PID regulator, without an integral component. Figure 3 illustrates a braking logic designed to push the torque of the low-pressure turbine 5 below a fixed limit 15 by current dissipation from the electric generator 9 to the dissipative load 12. In the illustrated example, the braking command is calculated based on the difference between the torque measured 16 by the torque sensor 10 and a maximum torque command 17. The braking logic incorporates a proportional component 18 and a derived component 19 of the PID regulator from which respectively derive a proportional gain and a derived gain on the braking setpoint. This results in a braking instruction which translates into a torque extraction instruction 19 on the electric generator 9. According to an alternative to the PID controller involving a fine but costly limitation of the torque of the low pressure turbine 5, it may be envisaged that the control system will integrate an on / off control logic and include a switching relay in place of the variable resistor 11. As illustrated in [Fig.4], the torque management process preferably integrates, in addition to the braking logic, a protection logic 20 of the dissipative load 12 against overheating. In this regard, the braking instruction can be calculated based on the thermal capacity of the dissipative load 12. The heat capacity is equal to the difference between an estimated temperature 21 of the dissipative load 12 and a limiting temperature 22 of the dissipative load 12. The limit temperature 22 is a constant representing the temperature limit not to be exceeded including a safety margin. The estimated temperature 21 is calculated from the torque sampling setpoint 19. A first-order filter 23 can be used to estimate the coarse-mesh thermal, but this modeling can be done with nonlinear, tabulated, higher-order models, and / or based on other information such as cooling capacity. A proportional gain 24 of the protection logic 20 of the dissipative load 12 against overheating leads to obtaining a limiting setpoint 25 of the torque taken from the electric generator 9. The torque taking setpoint 19 is advantageously calculated as a function of the protection logic 20 of the dissipative load 12 against overheating. This results in a saturation of the braking setpoint proportional to the thermal capacity. In the illustrated example, the protection logic 20 of the dissipative load 12 against overheating does not have a derived component due to the slow thermal dynamics. This allows the torque taken to be limited according to the thermal limits of the dissipative load 12. According to another embodiment, the dissipative load 12 can be formed by the electric generator 9, provided that the electric generator 9 is capable of absorbing the energy associated with the torque extracted from the low-pressure turbine 5 without generating a fire. The resistance 12 adjusted to meet the braking requirement is then the internal resistance of the electric generator 9. In the event that the dissipative load 12 is formed by the electrical generator 9, the electrical generator 9 will preferably be short-circuited or disconnected from the aircraft's electrical network. This makes it possible to protect the consumers present on the electrical network. In this regard, the turbomachine 1 may include a switching relay capable of short-circuiting the electrical generator 9 of the aircraft's electrical network. It will also be possible to anticipate that the braking setpoint will be calculated and the resistance internal of the electric generator 9 is adjusted by the electric generator 9 computer. The control computer 13 can then be configured to control the timing of the blower 6 and communicate to the electric generator 9 computer the measurement of the torque taken by the torque sensor 10. Preferably, in parallel with the adjustment of the resistance 11 of the dis- sipative load 12, a check of the timing of the blower 6 is carried out. Adjusting the angle of the blower blades 6 allows control, at least in part, of the torque on the shaft 7. The dynamics of controlling the dissipative load 12 are far superior to those of controlling the timing, which makes it possible to quickly limit the torque of the low pressure turbine 5 in order to protect the reducer 8 without it being necessary to increase the weight or complicate the architecture of the turbomachine 1.

Claims

Demands

1. A method for managing the torque of an aircraft turbomachine comprising a blower (6) or a variable-pitch propeller connected to a turbine (5) by a shaft (7) and a reducer (8), and an electric generator (9) connected to the tree (7), the process includes the following steps: the measurement of the torque on the shaft (7) from a torque sensor (10); when the occurrence of a torque peak is measured by the sensor torque (10), the calculation of a braking setpoint for the turbine (5) by a control system based on the measured torque; and in response to the braking command, the adjustment by the system of control of a resistor (11) of a dissipative load (12) for the electrical power extraction from the electric generator (9) to dissipative load (12).

2. A management method according to claim 1, wherein the instruction to braking is calculated based on the difference between the measured torque and a maximum torque setting.

3. A management method according to claim 1 or 2, wherein the The braking instruction is calculated based on the thermal capacity of dissipative load (12).

4. Management method according to any one of the preceding claims previous, in which the dissipative charge (12) is formed by the ge- electrical generator (9) and the resistor (11) is an internal resistance of the electric generator (9).

5. A management method according to claim 4, wherein during the pre- electrical power increase due to the internal resistance of the generator electric nerator (9), the electric generator (9) is short-circuited of the aircraft's electrical system.

6. Management method according to any one of the preceding claims previous, in which a fan speed check (6) or of The variable pitch propeller is controlled by the control system. parallel adjustment of the resistance (11) of the dissipative load {12).

7. Aircraft turbomachine comprising a fan (6) or a propeller variable pitch connected to a turbine (5) by a shaft (7) and a reduction gear (8), and an electric generator (9) connected to the shaft (7) the tur- bomachine (1) comprising: a torque sensor (10) configured to measure the torque on the shaft {); a control system configured to calculate a setpoint of turbine braking (5) when a torque peak occurs measured by the torque sensor (10), and configured to adjust a re- resistance (11) of a dissipative load (12) in response to the setpoint of braking for the extraction of electrical power from the generator electrical (9) to the dissipative charge (12).

8. Turbomachine according to claim 7, wherein the system of The control is configured to calculate the braking setpoint based on of the thermal capacity of the dissipative load (12).

9. Turbomachine according to claim 7 or 8, wherein the charge dis- sipative (12) is formed by the electric generator (9).

10. | Turbomachine according to claim 9, wherein the system of The order includes an electric generator calculator (9) configured to calculate the braking setpoint and adjust the resistance internal of the electric generator (9) in response to the instruction of braking.

11. … Aircraft comprising at least one turbomachine according to any one demands 7 to 10.