FR3088425A1 - METHOD FOR DETECTING A THERMAL EVENT - Google Patents

Abstract

The present invention relates to a method for detecting and determining a thermal event, implemented by a regulation system (10) of an aircraft engine, said regulation system (10) comprising: - a main computer ( 200) regulating the engine; a metering unit (100) comprising a fuel metering member for supplying the engine, associated with at least one electronic card (111) for controlling the metering member, said electronic card (111) being included in an electronic unit ( 110) separate from the main computer (200).

Description

DESCRIPTION

TITLE: METHOD FOR DETECTING A THERMAL EVENT

FIELD OF THE INVENTION

The present invention relates to the general field of aeronautics.

It relates more particularly to the detection of a thermal event, such as a fire or an overtemperature (substantial rise in temperature which is not caused by a fire) affecting a computer engine of an aircraft engine. This engine is for example a turbomachine such as a turbojet.

STATE OF THE ART

In known manner, an electronic engine computer of an aircraft is in the form of a box containing a plurality of electronic cards responsible for performing various functions such as engine regulation.

In current engines, an engine regulation system can also be equipped with a fuel metering unit, corresponding to a hydromechanical block more commonly known as FMU ("Fuel Metering Unit").

The hydromechanical unit shares several functions. It ensures, by a metering device, the metering of the fuel, that is to say the flow information which arises from a need dictated by a control unit of the regulation system according to the flight phase, with the relative precision required. It also allows, by a cut-off device, the fuel cut following a pilot command, and the cut and / or regulation of the fuel flow in the event of an overspeed emergency (high engine speed which gets carried away and requires for safety an engine shutdown) detected by a speed sensor of the high and / or low pressure part of the engine. For better operability of the systems, and especially for the flexibility of control / parameterization of the operability, but also for reasons of gain of mass, volume, the engine regulation computers today integrate certain electronic functions formerly fulfilled by hydromechanical blocks, such as in particular the "overspeed protection" function allowing the engine to be protected in a case where the engine speed exceeds the predefined maximum speed threshold (overspeed), by monitoring the engine speed and switching off the engine an overspeed is detected.

However, the behavior of an engine computer (such as a regulation computer, also called FADEC for "Full Authority Digital Engine Control" in English, and more generally called EEC, for "Electronic Engine Controller" in English) overheating or fire is difficult to predict, which leads engine manufacturers to consider the worst assumptions for the certification of computers (by the aeronautical equipment certification authorities).

Thus, the certification constraints impose not to undergo a simple electrical or electronic failure that could cause a risky event, for example an engine overspeed event caused by an erroneous command to actuate the metering device (known as in English " Fuel Metering Valve ": FMV) of the hydromechanical block (for example reaching the maximum dosing stop).

Consequently, in the context of a degraded engine operating mode such as a fire scenario, in which the overspeed event is a feared event, it must be possible to demonstrate that the overspeed detection and engine shutdown functions are still operational when the control function of the computer dies. This scenario is called "clean death" of the control unit of the regulatory system.

Otherwise, if we consider a "non-clean death", the protective functions "die" therefore firstly, leaving regulation alone in control. The worst scenario would then be an erroneous command from the regulating system to an engine regulating member, for example an erroneous position command to an actuator of a fuel metering unit which would put the actuator in a position of maximum flow, driving to an engine overspeed state in which the overspeed protection function could not accommodate the failure and therefore shut down the engine before it was damaged.

To deal with such a possibility, various solutions are envisaged in the state of the art.

One solution consists in using for the overspeed function, electronic components resistant to very high temperatures. This is to ensure that in the scenario considered above, a failure of an electronic card in charge of the overspeed protection function would occur after a failure of a card (of the engine control unit), responsible for the regulation function. However, historically, such components are components developed in small quantities, for very specific military aeronautical applications. They are therefore very expensive and difficult to obtain, and subject to early obsolescence.

An alternative solution consists in installing the overspeed detection function in a computer located in a so-called fire-free zone, in other words in an environment different from that of the regulation computer.

In the case in particular of certain engines developed by the applicant, the overspeed management functions are integrated into the engine computer. This solution requires solving problems of certification of the computer, in particular with respect to fire management events, in particular by solutions for segregation of the two subsystems containing the bodies performing the regulation and protection functions, within '' one housing.

In another solution, as is the case with other engines developed by the applicant, an independent computer is developed for the implementation of the overspeed protection functions in a “fire-free zone” and placed away from the computer control (engine control unit), which is located in the fire zone. However, the impacts in terms of mass (case, harness, additional supports, etc.) are considered significant and are reflected in particular by an increase in specific fuel consumption, which makes the engine less competitive from a point of view of aircraft performance. Furthermore, the development costs of an electronic aircraft computer are very high, an architecture comprising two computers developed independently is therefore particularly expensive.

In another alternative solution, publication FR2957667A1 by Snecma discloses a device for detecting overheating affecting a computer such as a FADEC (“Full Authority Digital Engine Control”), having at least one temperature sensor located inside of the computer, and at least one overheating detector located outside the computer in the vicinity thereof.

This publication does not disclose a detection strategy for discriminating overheating not related to a fire.

On the other hand, it does not provide a sufficient thermal margin to ensure a "clean death" of the control computer.

Consequently, considering the current state of the art, there are no satisfactory solutions for engine regulation calculator, which are not penalizing in terms of mass, installation cost and making it possible to comply with certification constraints and thus avoid a mode of operation. degraded.

STATEMENT OF THE INVENTION

The proposed invention makes it possible to implement a fire or overtemperature event detection system which makes it possible to shut down an aircraft engine before endangering the electronics dedicated to regulating or protecting the engine; and thus avoid a degraded operating mode.

To this end, the invention proposes a method for detecting and determining a thermal event, implemented by a system for regulating an aircraft engine, said regulation system comprising:

- a main computer regulating the engine;

- a metering unit comprising a fuel metering unit for supplying the engine, associated with at least one electronic control card for the metering unit, said electronic card being included in an electronic unit separate from the main computer; the process comprising the following steps:

- calculation of a theoretical ambient temperature threshold and a theoretical ambient temperature gradient threshold, as well as a theoretical card temperature threshold and a theoretical card temperature gradient threshold, by the main computer on the basis of a thermal model taking into account an engine speed value acquired by the main computer;

measurement of the temperature of the electronic card of the block by at least one first sensor disposed on the card, and acquisition of the measurement by the main computer and,

measurement of the ambient temperature of the block by at least one second sensor internal to a block housing or disposed on said housing, and acquisition of the measurement by the main computer;

- calculation of the temperature gradients acquired by the main computer;

- determination of a thermal overheating event if the following conditions are met:

o the ambient temperature is higher than the theoretical ambient temperature threshold, or the card temperature is higher than the theoretical card temperature threshold; or o the ambient temperature gradient is greater than or equal to the theoretical ambient temperature gradient threshold, or the card temperature gradient is greater than or equal to the theoretical card temperature gradient threshold;

the thermal overheating event corresponding to a fire if the ambient temperature gradient is greater than or equal to a predefined fire threshold of ambient temperature gradient; and the thermal overheating event corresponding to an over-temperature of origin external to said housing if:

o the ambient temperature gradient is greater than or equal to a predefined ambient temperature gradient overtemperature threshold and less than the ambient temperature gradient fire threshold; and o the card temperature gradient is greater than or equal to a predefined card temperature gradient over temperature threshold.

Advantageously, the detection method also comprises the following steps: a step of determining a thermal overheating event of internal origin at said housing if:

o the ambient temperature gradient is lower than the predefined over-temperature threshold of the ambient temperature gradient; and o the card temperature gradient is greater than or equal to the predefined card temperature gradient overtemperature threshold.

- confirmation of the determination of an event corresponding to a fire if the following condition is met:

o the ambient temperature gradient is greater than or equal to the predefined ambient temperature gradient overtemperature threshold for a first predefined confirmation period.

- confirmation of the determination of an event corresponding to an over-temperature if the following condition is met:

o the ambient temperature gradient is greater than or equal to a predefined ambient temperature gradient overtemperature threshold and less than the ambient temperature gradient fire threshold; and o the card temperature gradient is greater than or equal to a predefined card temperature gradient overtemperature threshold for a second predefined confirmation period.

- if a thermal event corresponding to a fire or an over-temperature originating outside said housing is determined, a step of transmitting a control signal to a cut-off member of a hydromechanical block of the metering unit to cut off the fuel supply to the engine.

The invention also provides a metering unit supplying fuel to an aircraft engine, comprising:

an electronic unit comprising an electronic card, said electronic unit comprising:

- at least a first sensor arranged on the card configured for the acquisition of the temperature of the electronic card of the electronic unit;

- at least one second sensor internal to a housing of the electronic unit, or disposed on said housing, and configured for the acquisition of the ambient temperature of the electronic unit;

said electronic unit being configured for the implementation of the method described above.

Advantageously, the metering unit also includes the following characteristic:

a hydraulic block configured to supply fuel to the engine, the electronic block being configured to transmit a command to cut off the fuel supply to the hydraulic block if a thermal event corresponding to a fire or to an over-temperature of external origin to said audit housing is determined.

The invention also provides a system for regulating an aircraft engine, said system comprising:

- a main computer;

a metering unit supplying fuel to the engine, comprising an electronic unit comprising a main electronic card, said electronic unit comprising:

o at least a first sensor disposed on the card and configured for the acquisition by the main computer of the temperature of the electronic card of the electronic unit;

o at least one second sensor internal to a box of the electronic block or disposed on said box, and configured for the acquisition by the main computer of the ambient temperature of the electronic block; and said regulation system being configured for the implementation of the method described above.

Advantageously, the regulation system also includes the following characteristics:

- the computer has two redundant channels;

the electronic unit comprises two redundant channels associated with the two channels of the computer, said electronic unit comprising on each channel:

o a first electronic module corresponding to a channel of two redundant channels of an electronic card configured for the protection of an overspeed state of the engine speed;

o a second electronic module corresponding to a channel of two redundant channels of an electronic card configured for the detection of an overspeed state of the engine speed;

and said electronic unit comprises on at least one channel:

o the first electronic module configured for the acquisition of temperature data from a sensor located on the main electronic card;

o the second electronic module configured for the acquisition of temperature data from the first electronic module of the same channel; and transmitting said temperature data to the corresponding channel of the computer; and / or o the second electronic module configured for the acquisition of temperature data from a sensor disposed on the main electronic card;

o the first electronic module configured for the acquisition of temperature data from the second electronic module of the same channel; and transmitting said temperature data to the corresponding channel of the computer.

The invention also provides a turbomachine of an aircraft comprising an engine regulation system as described above.

Advantageously, the invention makes it possible to rationalize the integration of an electronic card within a conventional metering unit by adding engine protection functionalities thereto, thereby making it possible to facilitate the system certification strategy while limiting the costs and physical impacts (mass, volume) and improving engine performance (via improved dosing accuracy).

DESCRIPTION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which should be read with reference to the appended drawings, in which:

[Fig. 1]

- Figure 1 illustrates a system for regulating a turbojet of an aircraft according to the invention;

[Fig. 2] Figure 2 illustrates an electronic unit of a metering unit according to the invention;

[Fig. 3]

- Figure 3 illustrates the main steps of a method of detecting a thermal event according to the invention; and [Fig. 4]

- Figure 4 illustrates a determination of theoretical thermal gradients according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

It will be used in the following description, the concept of "fire zone" and "non-fire zone". Only the compartments which contain sources of ignition and a risk of leaking flammable liquid are classified as fire zones, ie comprising potential sources of ignition in the event of failure which could cause a temperature higher than the auto-ignition temperature of the fluids possibly present in the compartment.

In contrast, a non-fire zone is a zone which is not in the configuration defining the fire zone.

FIG. 1 illustrates a regulation system 10 of a turbojet engine of an aircraft. The invention however also applies to other aircraft engines, and typically to other turbomachines (eg turboprop).

System for regulating the fuel supply of an aircraft

The regulation system 10 has a distributed electronic architecture studied, in the example envisaged here, this consists in deporting a certain number of functions performed by various electronic organs, within an electronics directly positioned on the equipment.

Thus, said regulation system 10 comprises:

a main engine regulation computer 200 (generally called EEC, for “Electronic Engine Controller” in English) which generates, as a function of the thrust requested by the aircraft, a fuel mass flow rate instruction transmitted to a metering unit 100. Said computer 200 is provided with two redundant channels A and B, represented 200A and 200B, and is located in a fire zone or in a non-fire zone; and a fuel metering unit 100 in a fire zone different from that in which the main computer 200 is located. This can thus be within the ventilation ("fan") or central ("core") compartment of the engine depending on whether the main controller is in the "fan" zone or in another zone such as the pylon or even integrated within the aircraft.

The metering unit 100 comprises a hydromechanical metering block 120 to which is added an electronic block 110 comprising at least one main electronic card 111 performing several functions for controlling and protecting the engine.

The electronic unit 110 is placed inside a housing 115.

In known manner, the electronic unit 110 is provided with two redundant channels A and B, in order to guarantee its operation even in the event of a breakdown of one of its components. Thus, typically, the two-way electronic unit 110 is divided into two sub-organs:

- two electronic modules 113A and 113B: responsible for regulating the motor, they correspond to the two redundant channels A and B of an internal / external (s), test & diagnostic sensor acquisition card and monitoring. This electronic card contains the meter's individual calibration data (FMV = Fuel Metering Valve). These modules can also be provided with control functions; and

- two electronic modules 114A and 114B: responsible for detecting an overspeed of engine speed, they correspond to the two redundant channels A and B of a card for protection against the overspeed event, and for fuel cut-off (according to the order engine / aircraft / protection). The module contains a critical function for detecting and accommodating an overspeed state of the high and / or low pressure part of the engine.

The modules 113 (113A and 113B) and 114 (114A and 114B) can be equipped with a plurality of temperature sensors 112A, located directly on the main card 111.

The temperature sensors 112A can be sensors known per se and having a sufficiently constant time constant to be able to quickly detect a significant change in temperature.

The 112A sensors are for example platinum resistance thermometers (of the silver, copper, nickel, gold, platinum, tungsten, titanium type, etc.), thermoresistors, thermistors, silicon sensors, thermocouples, etc. . It is not necessarily sought for precision, but simply a (strong) variation. A sensor for example with a wire (a hot spot and cold spot to the chassis ground) allows harness wiring to be saved.

Regardless of the type of 112A temperature sensor chosen, it is possible to "combine" several sensors on a single acquisition channel. It is therefore necessary to optimize the number of sensors necessary to minimize the impact on the main computer 200. Thus, failing to monitor component by component, the sensors are arranged in order to target the critical components and whose breakdowns most hamper the operation of the system even lead to dangerous events. It is therefore preferred areas of power supplies and areas where the logic components are located, these areas are the most critical because the largest heat emitters and whose temperature levels change more than the others.

The acquisition of this data from the 112A temperature sensors is done within the electronic cards. The data are then exchanged with the main computer 200, analogically or digitally by each channel, for example via the same communication bus connecting it to the electronic card of the metering unit 100 containing the data from other sensors (actuator, position ...).

An electronic module 113, 114 preferably comprises more than one sensor, since there are several critical components within it: generally the software part (a programmable FPGA logic circuit for example) as well as the power supply module. It should be noted that the use of two temperature sensors per card ensures redundancy at the level of each card. However, the invention also applies when a single temperature sensor is used per module.

Preferably, in order to respect as best as possible the rule of segregation between the control and protection functions, the channels A and B do not intersect (example of case of crossing: by acquiring information on channel A by lane B and vice versa).

In a first embodiment, the modules 114A and 114B, responsible for the protective functions against the overspeed event, are responsible for monitoring the temperature. It is the modules 113A and 113B which carry out the temperature acquisition of the modules 114A and 114B, and therefore centralize the temperature acquisition of the entire electronic card.

In a second embodiment, the modules 114A and 114B already having, moreover, engine speed acquisition functions for detecting an overspeed speed, they can also communicate the temperature data (for example by acquiring temperature data from modules 113A and 113B) to the main computer 200, help consolidate the overspeed information, by incorporating a thermal monitoring test into a continuity test of the overspeed event (current regime> design overspeed regime during X ms). This thus makes it possible to prevent and detect inadvertent detections of overspeed event due to a thermal failure of this card sector.

Consequently, the electronic architecture presented above makes it possible to take into account the need to monitor the temperature of each channel of the electronic block.

Referring again to FIG. 1, the electronic unit 110 also includes temperature sensors 112B, located inside said electronic unit 110, in order to monitor the temperature of the air surrounding the electronic card 111, or even the temperature of inner skin of the housing 115. These sensors 112B can be positioned inside the housing 115, or arranged on said housing 115, outside of the electronic card 111 or on the periphery thereof. The data from these sensors 112B is acquired directly by the main engine computer 200.

Consequently, due to the arrangement of the sensors 112A and 112B, during an increase in temperature outside the electronic unit 110, caused by an external event, regardless of the zone in which the electronic unit 110 is positioned, the temperature monitoring is doubly acquired by two different components. This allows the main control computer 200 to be informed as soon as possible of a fire situation around the system 10, using a network of judiciously distributed temperature sensors.

The main computer 200 therefore has two sources of temperature information giving it a precise map of the metering unit 100 and its associated critical functions.

FIG. 2 illustrates an example of distribution of the sensors within an electronic box 115, two networks of sensors 112 are located at the 8 interior vertices of the box 115. The costs of the sensors being significant, the box 115 can also include four sensors, in an optimized manner, they are arranged in such a way that the distance between each sensor 112 is maximum.

Method for detecting a thermal event

With reference to FIG. 3, the principle of operation of the main steps of a method for detecting a thermal event is now described, implemented by the main computer 200. The method can also, in an alternative embodiment, implemented by a remote computer, external to the regulation system 10.

In a configuration step E1, the main computer 200 initializes values of theoretical reference parameters, as a function of data of the engine speeds, of the external conditions (ex: temperature outside the airplane, temperature of the internal engine compartment in which the system is integrated depending on the flight phase, altitude, etc.). Thus, the computer 200 determines the theoretical parameters such as an ambient temperature T ° amb1, a card temperature T ° pcb1, an ambient temperature gradient V amb1, a card temperature gradient Vpcbl, an overheating temperature gradient of the Vpcb2 card, and a Vamb2 ambient superheat temperature gradient.

The main computer 200 can include a data memory in which the values of the theoretical parameters described above are for example pre-recorded.

It can also include a program memory in which the detection method is for example prerecorded.

Then, in a step E2, the ambient temperature T ° amb around the electronic card is acquired by the main computer 200. Similarly, the temperature T ° pcb of the electronic card is also acquired in a step E2 ’.

In a step E3, the ambient ambient temperature T ° acquired is compared with a threshold value. Said threshold value is determined as a function of the theoretical ambient temperature T ° amb1 and of a predefined thermal temperature AT ° amb.

Also, in a step E3 ’, the temperature T ° pcb acquired card is compared with a threshold value determined as a function of the temperature T ° pcb1 theoretical card and a predefined thermal margin AT ° pcb.

In the case where the temperatures acquired, in steps E3 and E3 ’, are lower than the threshold values, the thermal detection ends and the detection state is" healthy "(F1 with reference to FIG. 3).

Otherwise, in a step E4, an ambient temperature gradient Vamb is calculated and compared for a predefined confirmation time T4 (for example around 30 s), to the ambient theoretical Vambl gradient.

Likewise, in a step E4 ’, a map temperature gradient Vpcb is calculated and compared for a predefined confirmation time T4’ (for example around 30 s), to the theoretical map gradient V pcb1.

In the case where the gradients calculated are less than the theoretical gradients, the main computer 200 determines that the detection state is "healthy" (F1).

With reference to FIG. 4, the comparison with the theoretical temperature gradients may include a predefined margin, in order to determine an area of acceptable gradient values.

Otherwise, in a step E5, during a predefined confirmation time T5 (for example around 30s), the ambient temperature Vamb gradient is compared to the theoretical ambient Vamb2 gradient, also the acquired ambient temperature T ° is compared at theoretical ambient temperature T ° amb2.

Similarly, in a step E5 ′, during a predefined confirmation period T5 ′ (for example around 30 s), the gradient Vpcb of card temperature is compared to the gradient V pcb2 theoretical card, and the temperature T ° pcb card acquired is compared at temperature T ° pcb2 theoretical map.

Thus, if in step E5, the conditions evaluated (gradient Vamb> ambient ambient Vamb and T ° amb> T ° amb2) are verified, in a step E6a, over a predefined period, the evolution of the ambient temperature T ° amb is evaluated with reference to the ambient temperature T ° amb2. For this purpose, the detection device calculates, over a predefined period T6 (for example around 60s), the evolution of the difference in gradients Vamb-Vamb2 and the difference T ° ambT ° amb2. The system thus seeks to determine an external over-temperature event F2 to the system, characterized by an ambient air temperature within the housing which is constantly increasing, but with a small temperature gradient.

In the positive case, a step E6b can be executed to confirm the overtemperature event F2. Thus, if the gradient Vamb is approximately equivalent to Vamb2 and the difference between T ° amb and T ° amb2 evolves by increasing, and that in step E5, the conditions evaluated (gradient V pcb> V pcb theoretical ambient and T ° pcb> T ° pcb2) are verified, the device calculates, over the period T6, in a step E6b if the gradient Vcarte is approximately equivalent to Vcarte2 and that T ° map is greater than T ° map2.

If these conditions are satisfied (i.e. the board temperature constantly increasing but with a low temperature gradient) the main computer 200 determines that the detection state is an over-temperature event external to the system F2.

If the conditions evaluated in step E6a are not verified, a step E7a is carried out. In this step, the device evaluates whether the difference between gradient Vamb and Vamb2 evolves by increasing and that the difference between T ° amb and T ° amb2 evolves by increasing over a predefined period T7 (for example around 60s).

These conditions correspond to an increase in ambient temperature within the very violent case with a very short characteristic time (compared to the overtemperature event F2), characteristic of a fire event F3 outside the system.

In the positive case, a step E7b can be executed to confirm the fire event F3. Thus, it is also evaluated there if the difference between gradient V card and V card2 evolves by increasing and if the difference between T ° card and T ° card2 evolves by increasing.

If these conditions are verified, i.e. the F3 fire event is confirmed by the increase in temperature of the card in phase shift caused by the inertia, the thermal detection process ends and a fire event outside F3 in the system is detected.

To give an order of magnitude, a map temperature average gradient in the case of an F3 fire event is for example of the order of 1 ° C / s. A map average temperature gradient in the case of an F3 fire event is for example of the order of 5 ° C / s.

It should be noted that step E6b (respectively E7b) is executed after step E6a (respectively E7a) after a predefined delay, characteristic of thermal inertia, since there is a time phase difference in the measurement of the temperatures between the sensors room temperature, and card temperature. The time shift in the case of an over-temperature event F2 being much lower than in the case of a fire event F3.

The described method also allows the detection of a state of electronic failure (F4 with reference to FIG. 1), characterized by an increase in the temperature of the card in phase advance compared to the increase in the temperature of the ambient air in the electronic box 115.

Thus, if in step E4, the conditions evaluated (gradient Vamb> ambient theoretical Vambl and T ° amb> T ° amb1) are negative and the conditions evaluated in step E5 'are positive, a step E8 is executed for check a state of malfunction for a predefined confirmation period T8. The device calculates in a sub-step E8a of step E8 if the gradient Vcarte is approximately equivalent to Vcarte2 and that T ° map is greater than T ° map2.

If these conditions are satisfied, there is a sub-step E8b of step E8. In this sub-step, it is evaluated again if gradient V amb> V amb1 theoretical ambient and T ° amb> T ° amb1. In the positive case, the method concludes with a state F4 of electronic failure. Advantageously, the second acquisition by the main computer 200 provides a second safety curtain and allows a more reliable comparison of the information provided by the sensors 112B with what is seen within the electronic card by the sensors 112A. However, in the event of a breakdown of the communication bus between the metering unit and the main computer 200, the method can accommodate this breakdown by carrying out detection of feared events only from the network of ambient air temperature sensors within of the box without having the vision of the temperature of the electronic card.

In the case of a detection of a thermal event (F2 or F3), or of a failure, the method described also allows the main computer 200, in a later step, to accommodate the detected state, by the transmission an engine shutdown signal, for example by a fuel supply cutoff order sent to the metering unit 100 (more specifically by a cutoff member of said unit 100).

However, preferably, in the case of failure where the architecture has temperature sensors acquired by the card which performs the overspeed protection functions, authority is given to the body which can stop the engine in the event that it detects a fire / over-temperature event, no longer allowing it to protect the engine.

The described technical solution proposes a redundant temperature monitoring, by two independent means, thanks to a double acquisition (respectively by the electronic unit 110 and the main computer 200) of an electronic subsystem included in a sub-system of a dosing unit 100; in order to achieve an agile detection of dangerous events mainly of a thermal nature while ensuring maximum security for the system, but also for the entire regulation system as well as for the turbomachine.

In addition, depending on the architecture of the regulation system considered, the invention makes it possible to replace the fire detection system such as fire / overtemperature detection loops external to the main controller and having known disadvantages.

Consequently, the regulation system 10 described makes it possible to reduce the impact in terms of electronic card size (both in the metering unit and the central engine computer).

Also, the technical solution proposed responds to the technical problem of a fire situation or an over-temperature at the level of the electronic subsystem, from which it is vital to protect itself in terms of security or availability, by using in particular, uses the detection of a temperature delta between a reference zone and a zone subjected to external aggressions.

Claims (11)

1. A method of detecting and determining a thermal event, implemented by a regulation system (10) of an aircraft engine, said regulation system (10) comprising: a main computer (200) regulating the engine; a metering unit (100) comprising a fuel metering unit for supplying the engine, associated with at least one electronic card (111) for controlling the metering unit, said electronic card (111) being included in an electronic unit (110 ) separate from the main computer (200); the process comprising the following steps: (E1) calculation of a theoretical ambient temperature threshold and a theoretical ambient temperature gradient threshold, as well as a theoretical card temperature threshold and a theoretical card temperature gradient threshold, by the main computer (200) on the basis of a thermal model taking into account an engine speed value acquired by the main computer (200); (E2 ') measurement of the temperature of the electronic card (111) of the block (110) by at least one first sensor (112A) disposed on the card, and acquisition of the measurement by the main computer (200) and, (E2 ) measuring the ambient temperature of the block (110) by at least one second sensor (112B) internal to a box (115) of the block (110) or disposed on said box (115), and acquisition of the measurement by the main computer (200); (E4, E4 ’) calculation of the temperature gradients acquired by the main computer (200); (E6a, E7a) determination of a thermal overheating event if the following conditions are met: the ambient temperature is higher than the theoretical ambient temperature threshold, or the card temperature is higher than the theoretical card temperature threshold; or the ambient temperature gradient is greater than or equal to the theoretical ambient temperature gradient threshold, or the card temperature gradient is greater than or equal to the theoretical card temperature gradient threshold; the thermal overheating event corresponding to a fire (F3) if the ambient temperature gradient is greater than or equal to a predefined fire threshold of ambient temperature gradient; and the thermal overheating event corresponding to an over-temperature (F2) of origin external to said housing (115) if: the ambient temperature gradient is greater than or equal to a predefined ambient temperature gradient overtemperature threshold and less than the ambient temperature gradient fire threshold; and the card temperature gradient is greater than or equal to a predefined card temperature gradient over temperature threshold. 2. A method of detecting and determining a thermal event according to claim 1 in which the method further comprises a step of determining a thermal overheating event of internal origin inside said housing (115) if: the ambient temperature gradient is lower than the predefined ambient temperature gradient over-temperature threshold; and the card temperature gradient is greater than or equal to the predefined card temperature gradient overtemperature threshold. 3. A method of detecting and determining a thermal event according to claim 1 or 2 in which the method further comprises a confirmation of the determination of an event corresponding to a fire (F3) if the following condition is met: the ambient temperature gradient is greater than or equal to the predefined ambient temperature gradient overtemperature threshold for a first predefined confirmation period (T7). 4. Method for detecting and determining a thermal event according to one of the preceding claims, in which the method further comprises a confirmation of the determination of an event corresponding to an overtemperature (F2) if the following condition is met: the ambient temperature gradient is greater than or equal to a predefined ambient temperature gradient overtemperature threshold and less than the ambient temperature gradient fire threshold; and the card temperature gradient is greater than or equal to a predefined temperature threshold of the card temperature gradient for a second predefined confirmation period (T6). 5. Method for detecting and determining a thermal event according to one of the preceding claims, in which the method further comprises, if a thermal event (F2, F3) corresponding to a fire (F3) or to an overtemperature (F2 ) of origin external to said housing (115) is determined, a step of transmitting a control signal to a cut-off member of a hydromechanical block of the metering unit for cutting the fuel supply to the engine . 6. Metering unit (100) supplying fuel to an aircraft engine, comprising: an electronic unit (110) comprising an electronic card (111), said electronic unit (110) comprising: at least a first sensor (112A) disposed on the card configured for the acquisition of the temperature of the electronic card (111) of the electronic unit (110); at least one second sensor (112B) internal to a housing (115) of the electronic unit (110), or disposed on said housing (115), and configured for the acquisition of the ambient temperature of the electronic unit (110); said electronic unit (110) being configured for the implementation of the method according to one of claims 1 to 6. 7. Metering unit (100) according to the preceding claim, wherein said metering unit (100) also comprises a hydraulic unit (120) configured to supply fuel to the engine, the electronic unit (110) being configured to transmit a command. cut off the fuel supply to the hydraulic unit (120) if a thermal event (F2, F3) corresponding to a fire (F3) or an over-temperature (F2) of origin external to said housing (115) is determined . 8. System (10) for regulating an aircraft engine, said system comprising: a main computer (200); a metering unit (100) supplying fuel to the engine, comprising an electronic unit (110) comprising a main electronic card (111), said electronic unit (110) comprising: at least a first sensor (112A) disposed on the card (111) and configured for the acquisition by the main computer (200) of the temperature of the electronic card (111) of the electronic unit (110); at least one second sensor (112B) internal to a housing (115) of the electronic unit (110) or disposed on said housing (115), and configured for the acquisition by the main computer (200) of the ambient temperature of the electronic unit (110); and said regulation system being configured for the implementation of the method according to one of claims 1 to 6. 9. System (10) for regulating an aircraft engine, according to the preceding claim, in which: the computer (200) is provided with two redundant channels (200A, 200B); the electronic unit (110) comprises two redundant channels (A, B) associated with the two channels (200A, 200B) of the computer (200), said electronic unit (110) comprising on each channel (A, B): a first electronic module (113A, 113B) corresponding to a channel of two redundant channels of an electronic card configured for the protection of an overspeed state of the engine speed; a second electronic module (114A, 114B) corresponding to a channel of two redundant channels of an electronic card configured for the detection of an overspeed state of the engine speed; and said electronic unit (110) comprises on at least one channel (A, B): the first electronic module (113A, 113B) configured for the acquisition of temperature data from a sensor (112A) disposed on the main electronic card (111); the second electronic module (114A, 114B) configured for the acquisition of temperature data from the first electronic module of the same channel (A, B); and transmitting said temperature data to the corresponding channel (200A, 200B) of the computer (200). 10. An aircraft engine regulation system (10) according to claim 8 in which: the computer (200) is provided with two redundant channels (200A, 200B); the electronic unit (110) comprises two redundant channels (A, B) associated with the two channels (200A, 200B) of the computer (200), said electronic unit (110) comprising on each channel (A, B): a first electronic module (113A, 113B) corresponding to a channel of two redundant channels of an electronic card configured for the protection of an overspeed state of the engine speed; a second electronic module (114A, 114B) corresponding to a channel of two redundant channels of an electronic card configured for the detection of an overspeed state of the engine speed; and said electronic unit (110) comprises on at least one channel (A, B): the second electronic module (114A, 114B) configured for the acquisition of temperature data from a sensor (112A) disposed on the main electronic card (111); the first electronic module (113A, 113B) configured for the acquisition of temperature data from the second electronic module of the same channel (A, B); and transmitting said temperature data to the corresponding channel (200A, 200B) of the computer (200). 11. Turbomachine of an aircraft comprising a system (10) for regulating an engine according to one of claims 8 to 10.