Preventive thermal monitoring system for a fixed internal structure in a turbojet engine nacelle

Abstract

The invention relates to a method for monitoring an aircraft nacelle, the method comprising steps of: acquiring and storing, by an aircraft-mounted processor (ACT), measurement data from an array of temperature sensors (SN) distributed over a surface of a fixed composite structure of the nacelle; transmitting maintenance data from the stored measurement data, via a transmission network (NT), when the aircraft is on the ground; receiving and storing, by a ground-based maintenance system (GCT), the transmitted measurement data; detecting potential damage to the fixed composite structure based on the maintenance data; and determining, by the maintenance system, maintenance operations to be performed based on the detected potential damage to the fixed composite structure. Figure 3

Description

Title of the invention: Preventive thermal monitoring system for a fixed internal structure in a turbojet nacelle technical field

[0001] The present invention relates to a monitoring system for defining preventively maintenance operations carried out in the nacelle of a turbojet engine equipping an aircraft. State of the art

[0002] A turbojet nacelle generally has a substantially tubular structure comprising an air inlet upstream of the turbojet, an intermediate assembly designed to surround a turbojet fan, and a rear assembly that may incorporate thrust reversing means and is designed to surround the combustion chamber and all or part of the compressor and turbine stages of the turbojet. The nacelle is generally terminated by an exhaust nozzle whose outlet is located downstream of the turbojet.

[0003] Modern nacelles are designed to house a turbofan engine capable of generating, on the one hand, a hot air flow (also called the primary flow) from the turbofan engine's combustion chamber, circulating within a space delimited by a substantially tubular compartment called the "core" compartment, and on the other hand, a cold air flow (called the "secondary flow") from the fan, circulating outside the turbofan engine through an annular passage, called the "vein," formed between an internal structure defining a turbofan fairing and an internal wall of the nacelle. Both airflows are ejected from the turbofan engine through the nozzle at the rear of the nacelle.

[0004] The core compartment comprises an external casing serving as a housing, called the internal fixed structure (IFS), generally made of composite material. This internal fixed structure is subjected to significant thermal stresses. To thermally protect this internal IFS, thermal protection panels are known to be used, notably to isolate the nacelle components from the engine environment, thereby maintaining them at acceptable temperatures and ensuring a minimum service life. These thermal protection panels also provide fire protection. They can be used in other areas of the nacelle where there is a risk of fire.

[0005] Thermal protection panels generally include at least one insulating layer, which may be made from silica fibers, ceramic or a microporous material. The mattress can be fixed between straps, usually made of stainless steel.

[0006] During maintenance inspections on turbofan engines, numerous IFS components were found to have defects due to localized overheating of the composite structure. This overheating results from prior deterioration of the thermal protection, to the point that the latter can no longer protect the composite structure. Under these conditions, the composite structure can therefore be subjected to a heat flux with an excessive temperature. This flux can have a significant impact on the mechanical strength of a component of the structure, necessitating repair or even complete replacement of the component. The late detection of such overheating thus potentially leads to more complex and extensive replacements or repairs of the composite structure, and longer and more frequent grounding.However, at present, there is no solution for detecting heating of the IFS composite structure in flight.

[0007] It is therefore desirable to propose a system that can more quickly detect overheating of a composite structure such as that of the IFS during flight, analyze it, and define a maintenance operation within a timeframe compatible with an estimated state of damage. Indeed, optimizing maintenance operations can reduce the number of scrapped parts and decrease the duration and frequency of aircraft grounding. The aircraft's operational reliability can thus be improved. Summary

[0008] Embodiments relate to a method for monitoring an aircraft nacelle, the method comprising steps of: acquiring and storing, by a processor on board the aircraft, measurement data from a set of temperature sensors distributed over a surface of a fixed composite structure of the nacelle; transmitting maintenance data from the stored measurement data, by a transmission network, when the aircraft is on the ground; receiving and storing, by a ground monitoring system, the transmitted maintenance data; detecting, based on the maintenance data, potential damage to the fixed composite structure; and determining, by the maintenance system, maintenance operations to be carried out based on the potential damage detected to the fixed composite structure.

[0009] According to one embodiment, the sensors are distributed: according to the configuration of hot fluxes reaching the composite structure, and / or according to potential thermal effects on the fixed composite structure in the event of damage to the thermal protection layer, and / or on areas of the fixed composite structure likely to be subjected to the highest temperatures, and / or on areas of the composite structure subjected to the greatest mechanical stresses.

[0010] According to one embodiment, the method includes a functional test step to verify the operability of the temperature sensors and the embedded processor.

[0011] According to one embodiment, the method includes a step of adapting by the processor a sampling frequency of the measurement data according to a flight phase, in order to reduce the volume of maintenance data to be transmitted.

[0012] According to one embodiment, the transmission of maintenance data is carried out: by an existing module on board the aircraft, transmitting data to the ground monitoring system, or by a transmission module of a monitoring unit on board the aircraft, dedicated to the transmission of maintenance data to the ground monitoring system, or by using a network common to other equipment of the aircraft, or by using a network dedicated to the transmission of maintenance data.

[0013] According to one embodiment, the method includes the implementation of an authentication protocol to enable the ground monitoring system to approve or reject the receipt of measurement data, according to an authentication result.

[0014] According to one embodiment, the process comprises

[0015] steps consisting of: validating the measurement data from the sensors by applying confidence tests; constructing a temperature distribution map on the composite structure, from the measurement data; and evaluating a material health status of the composite structure, at least the validation step being executed by the processor.

[0016] Embodiments may also relate to an on-board monitoring system for an aircraft nacelle, comprising: a set of temperature sensors distributed over a surface of a fixed composite structure of the nacelle, a processor connected to the set of sensors, the monitoring system being configured to implement the method defined above.

[0017] According to one embodiment, the sensors comprise: temperature sensors of the type having an RFID communication interface, and / or Bragg gratings on optical fibers, and / or thermocouples, and / or one or more thermal image sensors.

[0018] Embodiments may also relate to an aircraft nacelle monitoring system, comprising: an on-board monitoring system, as previously defined, and a ground-based system configured to receive and store, receive data emitted by the monitoring system, and determine maintenance operations to be carried out on the fixed composite structure based on the data received from the monitoring system. Brief description of the figures

[0019] The present invention will be better understood with the aid of the following description of exemplary embodiments with reference to the accompanying figures, in which identical reference signs correspond to structurally and / or functionally identical or similar elements.

[0020] [Fig-1] Figures IA, IB and IC schematically represent in cross-section an element internal composite structure of a turbojet nacelle combined with thermal protection, according to various embodiments,

[0021] [Fig.2] Figures 2A, 2B, 2C and 2D schematically represent a part embedded in a monitoring system for a fixed composite structure, according to various embodiments,

[0022] [Fig. 3] Figure 3 schematically represents modules of the system of monitoring, according to one embodiment,

[0023] [Fig. 4] Figure 4 schematically represents modules of the system of monitoring, according to another embodiment, Detailed description

[0024] Figures IA, IB, and IC represent a thermal protection layer 2 covering a fixed composite structure 1 such as that of a turbojet engine nacelle. The layer 2 may be formed of several juxtaposed panels. In one embodiment, the thermal protection layer 2 is associated with temperature sensors SN distributed on the external surface of the layer 2 (Figure IA). The sensors may also be integrated within the layer 2 (Figure IB), or distributed on the surface of the composite structure 1, which is covered by the layer 2 (Figure IC). The sensors SN may include temperature sensors and optionally, pressure sensors.

[0025] Figure 2A shows an embedded part of a monitoring system adapted for monitoring a fixed composite structure. The embedded system includes a PRC processor, a TXI transmission interface for communicating with a ground-based part of the monitoring system when the aircraft is on the ground, an RFR RFID reader connected to several UHF AT antennas, and TS temperature sensors of the type with an RFID (Radio-Frequency Identification) communication interface. This design limits the number and length of wires to be installed on or opposite the structure.

[0026] Figure 2B shows the embedded part of the monitoring system, according to another embodiment. The embedded part of the system differs from that of Figure 2A in that the sensors comprise Bragg gratings on OF optical fibers distributed over the composite structure, the PRC processor being connected to the Optical fibers (OF) are transmitted via an optoelectronic interface (OPI) circuit. Each optical fiber transmits light pulses, with a portion of the incident light being reflected by each Bragg grating at the Bragg wavelength, while the remainder is transmitted through the optical fiber. When the optical fiber undergoes deformation or temperature changes, the Bragg wavelength shifts. By detecting and measuring this shift, it is possible to obtain localized temperature measurements along the fiber.

[0027] Figure 2C shows the embedded part of the monitoring system according to another embodiment. The embedded system differs from that of Figure 2A in that the sensors comprise thermocouples TC distributed over the composite structure, in particular according to the configurations shown in Figures IA, IB, IC. The PRC processor can directly receive and process the signals from the thermocouples TC.

[0028] Figure 2D represents the embedded part of the monitoring system, according to another embodiment. The embedded system differs from that of Figure 2A in that the sensors comprise one or more thermal imaging TIS sensors distributed over the composite structure, the PRC processor being able to directly receive and process the thermal images from the sensors. If necessary, an interface circuit can be provided to preprocess the thermal images. The TIS sensors can be positioned taking into account the configuration of heat fluxes likely to reach the composite structure 1.

[0029] Of course, the different types of sensors shown in Figures 2A to 2D can be used in combination, for example depending on the area to be monitored of the composite structure.

[0030] The distribution of the SN sensors (TS, TC, OF, TIS) on the fixed composite structure 1 is determined based on the potential thermal effects in the event of damage to the thermal protection layer 2. In one embodiment, the temperature sensors are positioned so as to detect a heat flux at an excessive temperature on the composite structural part, such an excessive temperature being able to reveal a breach in the thermal protection. For this purpose, a measured temperature can be considered excessive when the corresponding heat flux has sufficient energy to damage the composite structural part.

[0031] According to one embodiment, the temperature sensors are preferably positioned on areas of the composite structure subjected to the greatest mechanical stresses. Indeed, these areas are predominant in the material health of the composite structure as a whole.

[0032] To reduce the number of sensors to be distributed, these can be positioned on the areas of the composite structure likely to be subjected to the highest temperatures. These areas can be identified beforehand, for example, using a thermal imaging camera.

[0033] Figure 3 illustrates the composite structure monitoring system. The system comprises an ACT control unit mounted on the aircraft (AC) and a GCT ground control monitoring unit (GND) communicating with the ACT control unit via an NT network. The ACT control unit is implemented by the PRC processor connected to the SN sensors, which runs an MNTM monitoring module, a DSM data storage module, and a DTTX ​​data transmission module. The MNTM module receives measurements from the SN sensors at a rate determined by a polling cycle during periods when the turbojet engine is running. The MNTM module transmits the acquired measurements to the DSM storage module, which stores the data locally. The DTTX ​​module is activated when the aircraft is on the ground, and the control unit is connected to a GCT ground control monitoring unit.When activated, the DTTX ​​module transmits the data stored by the DSM storage module. For this purpose, the DTTX ​​module can access the NT network, both for transmission and reception, via an NT-compatible ATXI communication interface module.

[0034] The ACT control unit may also include a BITM test module that receives measurements from the SN sensors. The BITM module can be activated before the aircraft takes off to verify that the entire ACT unit and SN sensors are operational. If the test results do not conform to the expected results, the monitoring system can take action in such a way as not to impact the aircraft's availability.

[0035] According to one embodiment, the ACT control unit may include a self-contained power supply unit, independent of the avionics network. This independent power supply unit optimizes the aircraft's power consumption. Activation of this independent unit can be performed according to the aircraft's use case, such as when using BITM and DTTX ​​modules.

[0036] According to one embodiment, the ACT control unit is configured to acquire measurement data from the SN sensors at a sampling rate adapted to the flight phase. Thus, the sampling rate can be reduced when the current flight phase does not require measurements at a high frequency. This reduces the volume of measurement data to be transmitted, which also reduces the power consumption of the onboard part of the monitoring system.

[0037] The GCT ground surveillance control unit includes a processor that implements an AMT access management module and a DTMT data management module. The AMT module manages access to the ACT control unit for aircraft located on the ground nearby. To this end, the AMT module can communicate with the NT network via a GTXI communication interface module compatible with the NT network. The DTMT module stores the data downloaded by the AMT module in a ground-based database that stores downloaded data from a fleet of aircraft. The DTPR module is configured to access the downloaded database for an aircraft and to perform a maintenance diagnosis of the fixed structure of the aircraft's nacelles.

[0038] According to one embodiment, the DSM data storage module applies compression processing to the data before storing it. In this way, the volume of data to be stored and transmitted to the ground can be reduced. The DTMT or DTPR module is then configured to apply a corresponding decompression process to the data received from the aircraft.

[0039] According to one embodiment, the ATXI module is a transmission system available on board and used by other aircraft equipment. An alternative solution is to use the DTTX ​​transmission module of the ACT control unit to communicate the data collected during the flight to the GND ground monitoring system, via the NT network.

[0040] The DTTX ​​module is configured to detect the communication protocol implemented in the aircraft and activate a corresponding communication interface. Thus, the DTTX ​​module can implement, for example, the ARINC, AFDX ("Avionics Full DupleX"), or CAN ("Controller Area Network") protocols, and select the one implemented in the aircraft where the nacelle composite structure monitoring system is installed. The GTXI ground interface can be configured to implement the same communication protocol as the ATXI interface. The NT network can be LoRa, 5G, or WiFi™.

[0041] According to another embodiment, the NT network is separate from the network used by other aircraft equipment to communicate with ground systems, and is dedicated to transmitting measurement data from the SN sensors. The ATXI and GTXI communication interface modules, both onboard and on the ground, are specific interfaces. Thus, the monitoring system gains autonomy, facilitating the integration of the ACT unit onboard the aircraft and expanding its application possibilities to a wider range of aircraft.

[0042] According to one embodiment, the ATXI and GTXI communication interface modules on board the aircraft and on the ground implement an authentication protocol to allow the AMT access management module to approve or reject the downloading of data from the ACT control unit, depending on the authentication result. The implemented authentication protocol can be configured to allow the onboard ACT unit to send a request to the ground-based GCT unit (GND), which then performs an analysis to approve or reject the download of data from the ACT unit to the DTMT downloaded data management module. This measure aims to prevent potential cybersecurity risks.

[0043] According to one embodiment, the raw, unprocessed data from the SN sensors are stored by the DSM module and transmitted to the ground by the DTTX ​​module. Data processing is entirely handled by the DTPR module of the GCT unit on the ground. The DTPR module can be configured to (1) validate the data measured by the SN sensors by applying confidence tests, (2) construct a temperature distribution map of the composite structure, and (3) assess the material health of the composite structure, for example, by calculating margins or applying thresholds. The material health of the composite structure allows for the definition of any necessary maintenance operations.

[0044] According to an embodiment illustrated in Figure 4, the ACT unit includes a DPPR module for preprocessing data from the SN sensors. The DPPR module processes the data received from the sensors and stored by the DSM module in real time. The DTTX ​​module can then transmit only the results of the data processing performed by the DPPR module. Thus, the volume of data transmitted over the NT network can be reduced. The NT network used by the system can therefore have a lower data rate.

[0045] According to one embodiment, the DPPR module is configured to perform all or part of the data validation processes for measurement data from the sensors, to construct a temperature distribution map, and to assess the material health of the composite structure. The DPPR module can thus be configured to establish maintenance diagnostics and generate alerts that are transmitted to the ground-based GCT unit. In this case, the GCT unit is responsible for completing the processing performed by the DPPR module, in particular for generating diagnostic reports and recommendations for the aircraft operators.

[0046] Thanks to these provisions, the IFS environment of the nacelle can be secured by allowing the detection of damage as soon as it appears, or even the detection of potential damage before it appears, and the determination of appropriate maintenance operation recommendations.

[0047] It will be evident to those skilled in the art that the present invention is susceptible of various embodiments and applications. In particular, the invention is not limited to monitoring the thermal exposure of the composite structure of an aircraft nacelle, but can be applied to any other composite part exposed to heat flows that could damage it.

Claims

Demands

1. 1. A method for monitoring an aircraft nacelle, the method comprising steps of: acquiring and storing, by a processor (PRC) on board the aircraft, measurement data from a set of temperature sensors (SN, TC, OF, TIS) distributed over a surface of a fixed composite structure (1) of the nacelle; transmitting maintenance data from the stored measurement data, by a transmission network (NT), when the aircraft is on the ground; receiving and storing, by a ground monitoring system (GCT), the transmitted maintenance data; detecting, based on the maintenance data, potential damage to the fixed composite structure; and determining, by the maintenance system, maintenance operations to be carried out based on the potential damage detected to the fixed composite structure.

2. 2. Method according to claim 1, wherein the sensors (SN, TS, TC, OF, TIS) are distributed: according to the configuration of hot fluxes reaching the composite structure (1), and / or according to potential thermal effects on the fixed composite structure in case of damage to the thermal protection layer (2), and / or on areas of the fixed composite structure likely to be subjected to the highest temperatures, and / or on areas of the composite structure subjected to the greatest mechanical stresses.

3. A method according to any one of claims 1 and 2, comprising a functional test step to verify the operability of the temperature sensors (SN, TC, OF, TIS) and the embedded processor (PRC).

4. A method according to any one of claims 1 to 3, comprising a step of adapting by the processor (PRC) a sampling frequency of the measurement data as a function of a flight phase, to reduce the volume of maintenance data to be transmitted.

5. A method according to any one of claims 1 to 4, wherein the transmission of maintenance data is carried out: by an existing module (ATXI) onboard in the aircraft, transmitting data to the ground monitoring system (GND), or by a transmission module (DTTX) of a monitoring unit (ACT) onboard in the aircraft, dedicated to transmitting maintenance data to the ground monitoring system (GND), or by using a network common to other aircraft equipment, or by using a network dedicated to transmitting maintenance data.

6. 6. A method according to any one of claims 1 to 5, comprising the implementation of an authentication protocol to enable the ground-based monitoring system (GCT) to approve or reject the receipt of measurement data, according to an authentication result.

7. 7. A method according to any one of claims 1 to 6, comprising steps of: validating measurement data from sensors (SN) by applying confidence tests; constructing a temperature distribution map on the composite structure, from the measurement data; and evaluating a material health status of the composite structure, at least the validation step being executed by the processor.

8. 8. Onboard monitoring system for an aircraft nacelle, comprising: a set of temperature sensors (SN, TC, OF, TIS) distributed over a surface of a fixed composite structure (1) of the nacelle, a processor (PRC) connected to the set of sensors, the monitoring system being configured to implement the method according to any one of claims 1 to 7.

9. 9. Monitoring system according to claim 8, wherein the sensors (SN, TC, OF, TIS) comprise: temperature sensors (SN) of the type having an RFID communication interface, and / or Bragg gratings on optical fibers (OF), and / or thermocouples (TC), and / or one or more thermal imaging sensors (TIS).

10. 10. Aircraft nacelle monitoring system, comprising: an on-board monitoring system, according to one of claims 8 to 9, and a ground-based system configured to receive and store data emitted by the monitoring system, and to determine maintenance operations to be performed on the fixed composite structure based on the data received from the monitoring system.

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