ASSEMBLY COMPRISING A FLUID ENVELOPE SURROUNDED BY A TUBULAR SECTION DEFINING AN INTERIOR SPACE AND A SET OF HEAT FLOW SENSORS ARRANGED IN THE INTERIOR SPACE

Abstract

ASSEMBLY COMPRISING A FLUID ENVELOPE SURROUNDED BY A TUBULAR SECTION DEFINING AN INTERIOR SPACE AND A SET OF HEAT FLOW SENSORS ARRANGED IN THE INTERIOR SPACE The invention relates to an assembly (100) comprising an inner tubular section (108) and a fluid envelope (102) arranged in the inner tubular section (108) and delimiting therewith an interior space (110). The assembly also comprises a first group of at least three heat flow sensors (112), where the sensors are arranged in said interior space and generally in the same plane perpendicular to the central line (X), and the sensors (112) are distributed angularly around the central line (X), and an acquisition and control unit which receives the data from each sensor and which, from this data, determines an alert level.With such an arrangement, monitoring the values ​​of the various heat flux sensors allows for the rapid detection and monitoring of a possible leakage problem at the fluid envelope. Fig. 2.

Description

Title of the invention: ASSEMBLY COMPRISING A FLUID ENVELOPE SURROUNDED BY A TUBULAR SECTION DEFINING AN INTERIOR SPACE AND A SET OF HEAT FLOW SENSORS ARRANGED IN THE INTERIOR SPACE Technical field

[0001] The present invention relates to an assembly which comprises an outer tubular section, an inner tubular section mounted inside and coaxially with respect to the outer tubular section, a fluid envelope which delimits an interior space with the inner tubular section and a set of thermal flux sensors which are distributed in the interior space, as well as an aircraft comprising at least one such assembly. STATE OF THE PRIOR ART

[0002] An aircraft conventionally comprises at least one turbojet engine which comprises an engine forming a core around which are arranged a fixed internal structure (also called IFS "Internal Fixed Structure" in Anglo-Saxon) surrounding the engine, and external cowls arranged around the fixed internal structure. The fixed internal structure serves, among other things, as thermal barriers with the other elements of the turbojet engine arranged outside the fixed internal structure.

[0003] The fixed internal structure generally takes the form of a cylinder of revolution inside which a fluid circulates, for example in gaseous and / or liquid form for the purpose of cooling the components of the engine. Such a fluid circulates around the engine in the form of a complex flow moving generally from the front to the rear of the fixed internal structure.

[0004] Leaks of hot fluid with a temperature typically exceeding 500°C, for example, from the hot air purge or air conditioning ducts and / or valves for the aircraft or the deicing system located within the fixed internal structure and located around the engine, are likely to create a fire or abnormal heating of the engine components inside the fixed internal structure and the fixed internal structure itself.

[0005] To detect such leaks, it is known to implement, within each engine, a single temperature sensor, generally of the thermocouple type, fixed within the volume formed between the engine and the fixed internal structure, and called a “Tnac” nacelle sensor. To carry out a test to detect a hot air leak, a A well-known test procedure (called the “High Power Assurance” (HPA) test) involves running the aircraft’s starboard and port engines at high power for a predetermined period of time (usually around four minutes). Using their respective temperature sensors, the temperature of the starboard engine is compared to that of the port engine. If a predetermined temperature difference (usually at least 40°C) is observed between the starboard and port engines, it is determined that a potential leak is present in the hotter engine.

[0006] A disadvantage of this technique is that there are so-called "hot" engines and so-called "cold" engines which are characterized by ground tests. Thus, if the aircraft has a hot starboard engine and a cold port engine, the test will detect a potential leak of hot fluid due to the temperature difference measured by the sensors of each engine, when no leak is in fact present.

[0007] If a leak actually occurs on the cold engine, it will not be detected by this test.

[0008] Another disadvantage of this test is that if a potential leak is detected, it is not located or quantified within the fixed internal structure.

[0009] To locate such a leak, it is then known to use a developer in the form of a powder. This powder is applied by the operators to the fluid conduits and valves to try to locate the leak. It is then necessary to restart a leak detection procedure, that is to say to operate the engine presenting a potential leak for a predetermined duration, then to look for traces of elimination of the powder indicating the presence of a leak.

[0010] A disadvantage of this technique is that applying the powder to fluid conduits and valves is time-consuming and expensive. In addition, specific areas are generally tested as a priority and the quantity of powder to be applied must be appropriate to reveal the leak. However, this procedure is not always known and / or mastered by operators.

[0011] Another disadvantage is that it is then necessary to clean the engine, i.e. to remove the powder applied during the test before the aircraft can be used in flight condition, which is also a relatively time-consuming and expensive operation.

[0012] Another disadvantage is that the traces of powder removal indicating the passage of hot air are relatively difficult to exploit and quantify. If the number of temperature sensors were multiplied in order to improve the location of the leak, the problem would only be multiplied due to the complexity of the air flow. Therefore, the leak detection procedure, i.e., operating the engine with a potential leak for a predetermined period of time, must be repeated until the leak is precisely located. so that the corresponding maintenance operations can be carried out. However, each leak detection procedure represents a relatively high cost and a relatively significant environmental impact due to the operation of the engine.

[0013] The state of the art is not satisfactory and it is therefore necessary to find a solution which makes it possible, among other things, to quickly and reliably locate and quantify fluid leaks during operation of the aircraft engines, on the ground but preferably also in flight conditions, while limiting the operability and maintenance constraints of such a solution. Statement of the invention

[0014] An object of the present invention is to provide an assembly which comprises an outer tubular section, an inner tubular section mounted inside and coaxially with respect to the outer tubular section, a fluid envelope which delimits an interior space with the inner tubular section and a set of thermal flux sensors which are distributed in the interior space.

[0015] For this purpose, an assembly is proposed comprising:

[0016] - an inner tubular section extending longitudinally between a first end, called front, and a second end, called rear, along a central line,

[0017] - an envelope of a fluid mounted coaxially with respect to the section inner tubular section and within the inner tubular section, an interior space being defined between said inner tubular section and said envelope of a fluid and wherein a fluid flow moves generally parallel to the center line in said interior space from the front to the rear of said inner tubular section,

[0018] - a first group of at least three thermal flux sensors arranged in said interior space at a rear area of ​​said assembly, where the sensors of said first group are arranged generally in the same plane perpendicular to the central line, and where the sensors of said first group are distributed angularly around the central line, said sensors of said first group being configured to acquire data representative of a thermal flux, and

[0019] - an acquisition and control unit connected to each sensor of said first group and configured to receive the data acquired by each sensor of said first group, compare said data to reference values, and determine an alert level relating to said assembly based on said comparison.

[0020] With such an assembly, monitoring the values ​​of the different heat flow sensors makes it possible to detect and monitor a possible problem at the level of the fluid envelope, such as for example a leak of hot fluid, a possible start of fire or a possible overheating coupled with an overpressure, both due to a pipe rupture, with a more precise quantification of the event in relation to the state of the technical. This assembly also allows for improved detection of a potential problem with the fluid envelope in terms of reliability, detection time and location of said problem, as well as a reduction in ground investigation time to locate said problem, and better monitoring in the event of a problem occurring. This monitoring allows for the implementation of predictive maintenance with a reduction in costs.

[0021] According to a particular aspect, the assembly comprises a second group of at least three heat flux sensors arranged in said interior space at a front zone of said assembly, where the sensors of said second group are arranged generally in the same plane perpendicular to the central line, where the sensors of said second group are distributed angularly around the central line, said sensors of said second group being configured to acquire data representative of a heat flux, and where the sensors of said second group are connected to said acquisition and control unit, the acquisition and control unit being configured to receive the data acquired by each sensor of said second group, compare said data with reference values, and determine an alert level relating to said assembly as a function of said comparison.

[0022] According to another particular aspect, the assembly comprises a third group of at least three heat flux sensors arranged in said interior space between said first and second groups, where the sensors of said third group are arranged generally in the same plane perpendicular to the central line, where the sensors of said third group are distributed angularly around the central line, said sensors of said third group being configured to acquire data representative of a heat flux, and where the sensors of said third group are connected to said acquisition and control unit, the acquisition and control unit being configured to receive the data acquired by each sensor of said third group, compare said data with reference values, and determine an alert level relating to said assembly as a function of said comparison

[0023] According to another particular aspect, for each group, there are three sensors which are arranged in a transverse plane perpendicular to the central line and which are distributed at an angle of between 110° and 130° around the central line and where a first of said at least three sensors is arranged in the upper part of the assembly, above said envelope of a fluid, and on a vertical axis extending generally perpendicular to the central line.

[0024] According to another particular aspect, each sensor comprises a generally planar effective measuring surface, where a normal of said surface extends at an angle of between +30° and -30° relative to said central line.

[0025] According to yet another particular aspect, said normal of the surface of said sensor extends parallel to said central line.

[0026] According to a particular aspect, said surface of each sensor is housed in a sleeve made of thermally insulating material with a thermal conductivity of less than 0.1 Wm 'K'.

[0027] According to another particular aspect, said assembly further comprises an outer tubular section mounted coaxially with respect to the inner tubular section, outside the inner tubular section, where said assembly is an aircraft turbojet, where the fluid envelope is an engine channeling a flow of hot gas, and where the outer tubular section and the inner tubular section respectively constitute an outer wall and an inner wall of a fixed internal structure.

[0028] According to yet another particular aspect, said first, second and third groups of sensors are removable from said assembly.

[0029] The invention also proposes an aircraft comprising at least one assembly according to one of the preceding variants. Brief description of the drawings

[0030] The above-mentioned features of the invention, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in relation to the attached drawings, among which:

[0031] [Fig-1] is a side view of an aircraft according to the invention,

[0032] [Fig.2] is a schematic and sectional representation along line ILII of the [Fig.l] of a fixed internal structure of a turbojet according to an embodiment of the invention,

[0033] [Fig.3] is a sectional view along line III-III of the fixed internal structure of the [Fig.2],

[0034] [Fig.4a] is a front view of an example of sensors implemented in the structure fixed internal according to the invention,

[0035] [Fig.4b] is a front view of a variant of the sensor of [Fig.4a]; and

[0036] [Fig.5] represents an example of architecture of an acquisition and control unit implemented in an assembly according to the invention.

[0037] DETAILED DESCRIPTION OF EMBODIMENTS

[0038] With reference to [Fig.l], an aircraft 10 comprises a fuselage 12 on each side of which is fixed a wing 14 which carries at least one turbojet engine 100, in particular a dual-flow turbojet engine, and a mast 18 which ensures the fixing of the turbojet engine 100 under the wing 14.

[0039] In the following description, and by convention, X is the longitudinal axis of the turbojet 100 which is parallel to the longitudinal axis of the aircraft 10 and oriented posi tively towards the front of the aircraft 10, we call Y the transverse axis of the turbojet 100 which is horizontal when the aircraft 10 is on the ground, and Z the vertical axis of the turbojet 100 when the aircraft 10 is on the ground, these three axes X, Y and Z being orthogonal to each other.

[0040] On the other hand, the terms "front" and "rear" are to be considered in relation to a direction of advancement of the aircraft 10 during operation of the turbojet 100, this direction being represented schematically by the arrow A.

[0041] With reference to [Fig.2] and [Fig.3] an exemplary embodiment of the invention is disclosed in the case of a turbojet engine 100 of an aircraft 10. [Fig.2] illustrates a front sectional view of the turbojet engine 100 which comprises a fluid casing here in the form of an engine 102. The engine 102 forms a core around which is arranged a

[0042] fixed internal structure 104. Around a casing of the engine 102 circulates a flow of fluid E, preferably air, taken from a secondary flow of the turbojet 100 to cool the engine 102 and its components fixed on the casing of the engine 102. This flow of fluid E is also called ventilation flow. In a variant, around the casing of the engine 102 circulates a flow of hot air taken from the engine 102 and the assembly formed by the fixed internal structure 104 and the engine 102 then behaves as a transport pipe for the flow of fluid E. The engine 102 constitutes a fluid envelope 102 which channels a flow of hot gas which circulates in said fluid envelope 102.

[0043] The fixed internal structure 104 generally takes the form of a cylinder of revolution coaxial with the longitudinal axis X. This cylinder shape can also be close to a barrel shape.

[0044] In the embodiment of the invention presented here, the fixed internal structure 104 is divided into two half-cylinders fixed in the upper part to the mast 18 of the aircraft 10. The lower parts of the two half-cylinders are fixed to a structural element 20 of the turbojet 100.

[0045] The fixed internal structure 104 comprises an inner wall 108 which is centered on a center line X and, in this example, an outer wall 106 which extends coaxially with the inner wall 108 and outside the inner wall 108. The motor 102 is also mounted coaxially with and inside the inner wall 108. An interior space 110 is defined between the inner wall 108 and the motor 102. The fluid flow E circulates in this interior space 110 generally parallel to the center line X, from the front to the rear of the motor 102, as illustrated by the arrow F.

[0046] The outer wall 106 is preferably a structural wall of the fixed inner structure 104, but may also be a wall made of a thermally conductive material. insulating.

[0047] The outer wall 106 and the inner wall 108 respectively constitute an outer tubular section 106 and an inner tubular section 108. The outer 106 and inner 108 walls extend coaxially with the central line X, which here merges with the longitudinal axis X.

[0048] The assembly 100 comprises heat flux sensors 112 (hereinafter referred to as “sensors”) distributed in the interior space 110 and embodiments of which are shown in Figs. 4a and 4b.

[0049] The sensors 112 are fixed in the interior space 110, between the inner tubular section 108 and the motor 102, for example by means of fixing supports connected to the outer tubular section 106 which is here structural, and consequently rigid, rather than on the inner tubular section 108 which may have a thermal insulation function and which may need to be replaced. In a variant, it is possible to fix the sensors 112 directly to the components present in the interior space 110, for example by means of a flange or a fixing support, preferably having low thermal conductivity.

[0050] In this way, it is possible to arrange each sensor 112 near a potential leak of hot air from a hot air supply system taken from the engine 102.

[0051] Each sensor 112 delivers a value relative to the value of the heat flux passing through it. The heat flux passing through each sensor 112 comprises the heat flux originating from the flow of fluid E to which is possibly added one or more leakage heat fluxes Lx originating from the components located in the interior space 110. The leakage heat fluxes Lx are heat fluxes originating from the hot air or heat fluxes originating from the cold air which will therefore have an impact on the temperature of the flow of fluid E.

[0052] The use of heat flux sensors makes it possible to measure the heat flux received by each sensor and to compare this received heat flux with an expected heat flux value. These sensors allow use in the case of hot fluid or cold fluid leakage.

[0053] For example, the heat flux sensor used is a one-dimensional flat panel sensor consisting of several small thermocouples connected in series to form a thermopile for amplifying the output voltage from a given temperature. Such sensors have high sensitivity and high accuracy. It is therefore possible to significantly reduce leak detection times (detection time less than 15 seconds), which also makes it possible to reduce the duration of HPA tests to one minute rather than four minutes with prior art solutions. It should be noted that these sensors are also compatible with fire detection solutions implemented in turbojet engines, which also helps to improve aircraft safety.

[0054] In addition, these sensors are robust and have optimized repeatability, which makes it possible to easily exploit their measurements and limit maintenance operations on the assembly 100.

[0055] With reference to Figs. 2 and 3, the distribution of the sensors 112 within the interior space 110 provides a distribution of the sensors in at least three groups of at least three sensors distributed circumferentially and along the longitudinal axis parallel to the direction of fluid flow E.

[0056] The assembly 100 comprises a first group 11a of at least three sensors 112 arranged in the interior space 110, i.e. between the inner tubular section 108 and the engine 102. The first group 11a of sensors 112 is preferably fixed at a rear zone of the assembly 100, relative to the direction of advance A. More particularly, in the case of the turbojet engine 100 illustrated in this example, the first group 11a of sensors 112 is arranged downstream, relative to the direction of flow E, of the various valves and purge pipes (not illustrated) and upstream, relative to the direction of flow E, of the high-pressure turbine (not illustrated) of the turbojet engine.

[0057] The sensors 112 of the first group 11a are arranged generally in the same plane perpendicular to the central line X. In other words, the sensors of the first group 11a are arranged in a plane extending generally parallel to the transverse plane YZ.

[0058] Furthermore, around the central line X, the sensors 112 of the first group 11a are angularly distributed around the central line X and, depending on the number of sensors 112 implemented, the gap between two angularly consecutive sensors 112 varies. In this example, the first group 11a comprises three sensors 112, 112a which are regularly distributed around the central line X with an angle of between 110 and 130° between each sensor 112, 112a, and preferably 120°. It is obviously understood that a different angular distribution is possible. Similarly, if the first group 11a comprises a higher number of sensors, the angular distribution will be different.

[0059] The assembly 100 also comprises an acquisition and control unit 500 which is in wired or wireless connection with each sensor 112 of the first group 11a in order to collect the value delivered by said sensor 112 at a time 't'. The acquisition and control unit 500 is also in wired or wireless connection with each sensor 112 of the second 11b and third 11c groups described in more detail below. A wireless connection between the sensors 112 and the acquisition and control unit makes it possible in particular to facilitate the installation or movement of the sensors. 112, as well as the addition or replacement of these.

[0060] Depending on the thermal flows received by the different sensors 112 along the assembly 100, the acquisition and control unit 500 can determine whether one or more sensors 112 measure thermal flows that are disproportionate to the reference values ​​expected for each sensor 112, which may mean the appearance of a problem at the level of the fluid envelope 102 or one of the components located in the interior space.

[0061] From the values ​​received, the acquisition and control unit 500 determines an alert level relating to the assembly 100. The alert levels are for example four in number:

[0062] - class 1: conditions are normal,

[0063] - class 2: conditions are slightly abnormal which suggests a latent leak of the fluid envelope 102 close to the sensor(s) 112 presenting a value disproportionate to the reference value expected by the corresponding sensor, the evolution of this leak having to be monitored in particular,

[0064] - class 3: conditions are highly abnormal, suggesting a burst of a pipe or a loss of sealing at a joint due to overpressure or fatigue of the material constituting the joint close to the sensor(s) 112 having a value disproportionate to the reference value expected by the corresponding sensor, and

[0065] - class 4: the conditions are very highly abnormal which suggests the presence of a start of fire close to the sensor(s) 112 presenting a value disproportionate to the reference value expected by the corresponding sensor.

[0066] Depending on the alert level, appropriate corrective measures may be taken, such as, for example, in-flight measurements, preventive maintenance measures for slightly abnormal and highly abnormal conditions, and verification and possibly extinguishing measures for very highly abnormal conditions, such as, for example, the detection of the start of a fire close to the casing of the engine 102.

[0067] Thus, the assembly 100 allows continuous monitoring of the operating conditions with inexpensive sensors that are simple to implement and lightweight compared to the elements of the state of the art.

[0068] Furthermore, it is possible to monitor the thermal environment of the assembly (here a turbojet engine of an aircraft), whether on the ground or in flight. Such an assembly 100 makes it possible to detect hot air leaks precisely and in real time in order to avoid damage to the structures and components of the turbojet engine nacelle. Thus, it is possible to implement actions in real time or during preventive maintenance of the aircraft.

[0069] In addition, the assembly 100 allows for precise verification and correlation of the thermal simulation models used during tests of the assembly 100 in operation on the ground or in flight, and in the development phase.

[0070] The assembly 100 also makes it possible to measure and detect the effects of recirculation of the air flows within the interior space 110. The assembly 100 can therefore also participate in optimizing the ventilation architecture of the turbojet.

[0071] According to one embodiment, the assembly comprises a second group 11b of at least three sensors 112 also arranged in the interior space 110. The second group 11b of sensors 112 is arranged at a front zone of the assembly 100. In the case of the turbojet engine 100 illustrated here, the second group 11b of sensors 112 is located upstream relative to the direction of the fluid flow E and close to the purge valves and the associated orifices of the turbojet engine. In accordance with the first group 11a, the sensors 112 of the second group 11b are arranged generally in the same plane perpendicular to the central line X (i.e. in another plane extending generally parallel to the transverse plane YZ) and are distributed angularly around the central line X.

[0072] In this example, the second group 11b comprises three sensors 112, 112a and 112b which are distributed regularly around the central line X with an angle of between 110 and 130°, and preferably 120°, between each sensor 112, 112a and 112b.

[0073] As described previously, the acquisition and control unit 500 is in wired or wireless connection with each sensor 112 of the second group 11b in order to collect the value delivered by said sensor 112 at a time 't'.

[0074] The implementation of a second group 11b of sensors 112 located at the front of the assembly 100 makes it possible to improve the detection, quantification and localization in real time of hot air leaks in order to avoid damage to the structures and components of the turbojet nacelle.

[0075] According to one embodiment, the assembly 100 comprises a third group 11e of at least three sensors 112 also arranged in the interior space 110. The third group 11e of sensors 112 is arranged between the first 11a and second 11b groups of sensors 112. Preferably, the third group 11e is located approximately equidistant from the first 11a and second 11b groups of sensors and, preferably, relatively close to the purge valves, the hot air pipes and the associated orifices of the turbojet engine. It is obviously understood that another positioning of the third group 11e is possible depending on the detection needs.

[0076] In accordance with the first 11a and second 11b groups, the sensors 112 of the third group 11c are arranged generally in the same plane perpendicular to the center line X (i.e. in yet another plane extending generally parallel to the transverse plane YZ) and are angularly distributed around the center line X.

[0077] In this example, the third group 11 also comprises three sensors 112, 112a and 112b which are distributed regularly around the central line X with an angle of 120° between each sensor 112, 112a and 112b.

[0078] As described previously, the acquisition and control unit 500 is in wired or wireless connection with each sensor 112 of the third group 11e in order to collect the value delivered by said sensor 112 at a time 't'.

[0079] The implementation of a third group 11e of sensors 112 located between the first 11a and second 11b groups makes it possible to further improve the detection, quantification and localization in real time of hot air leaks in order to avoid damage to the structures and components of the turbojet nacelle, due to the division of the assembly into finer detection zones.

[0080] The distribution of groups 11a, 11b and 11c of sensors 112 along the central line X makes it possible to cover the entire part of the assembly 100 concerned by the monitoring.

[0081] The particular installation of the sensors 112 makes it possible to obtain different zones equipped with sensors 112 and distributed along the central line X and to cover the assembly 100 over the entire length thus equipped. Each zone thus corresponds to a group. Preferably, each zone comprises components which could potentially have a leak, such as for example a valve or a connection between two fluid pipes.

[0082] In this way, the location of the leak is relatively precise, which makes it possible to carry out only one HPA test, unlike the solutions of the state of the art which may require the repetition of the HPA test until the leak is located with the developer in the form of a powder. Indeed, the assembly 100 makes it possible to refrain from using a developer, which makes it possible to reduce the operations to be carried out when detecting a leak. The maintenance time allocated to leak detection is therefore reduced, as are the associated costs.

[0083] According to one embodiment, illustrated in particular in [Fig. 2], each group 11a, 11b and 11c comprises three sensors 112a, 112 distributed at an angle of 120° around the central line X. In addition, a first sensor 112a of each group is arranged in the upper part of the assembly 100 (i.e. above the fluid envelope 102) and preferably on a vertical axis extending perpendicular to the central line X. In other words, the first sensor 112a of each group is arranged on a vertical axis generally parallel to the vertical axis Z. Thus, the first sensor 112a is optimally located at the point where the fluid flow E is supposed to be the warmer in the interior space 110, just after the engine is stopped at the end of the HPA test because heat naturally rises within the interior space 110 in the absence of forced convection.

[0084] Consequently, the other two sensors 112 are located in the lower part and on each side (port and starboard) of the fluid envelope 102 relative to the central line X. In addition, a sufficient number of sensors which is typically greater than or equal to three per group makes it possible to compensate for the failure of at least one sensor, which makes it possible to make this detection system robust.

[0085] According to one embodiment, illustrated in Figs. 4a and 4b, each sensor 112, 112a has a total surface area which is here of generally rectangular shape. It is obviously understood that the sensors may have a total surface area of ​​different shape, and in particular of generally circular shape. The effective measuring surface area S is generally slightly less than the total surface area. The effective surface area S is generally flat and rectangular, or even square, with a length L and a width 1. The length L is greater than or equal to the width 1. The normal to the effective surface area S is preferably oriented at an angle of between +30 and -30° relative to the central line X, i.e. at an angle of between +30 and -30° relative to the direction of the air flow E. In other words, the plane of the effective surface area is oriented at an angle of between +30 and -30° relative to the vertical plane ZY.

[0086] Preferably, the normal to the effective surface of each sensor 112, 112a extends parallel to the central line X. In other words, the plane of the effective surface is oriented parallel to the vertical plane ZY.

[0087] Preferably, the effective surface has a low hemispherical emissivity in the infrared and less than 0.1 in order to reduce radiative exchanges with the hot parts of the engine 102 by making them weak with respect to convective exchanges.

[0088] This particular orientation of the sensors 112, 112a makes it possible to optimally measure the convective thermal flux originating mainly from the flow of fluid E while taking into account the additional thermal fluxes due to potential leaks Lx.

[0089] In this example, the sensor 112, 112a comprises a wire 116 for connection to the acquisition and control unit. In a variant not illustrated, the sensor 112 is connected wirelessly to the acquisition and control unit.

[0090] According to one embodiment, illustrated in [Fig.4b], the sensors 112, 112a may comprise a thermal protection sleeve 114 in which at least the surface S of the sensor is housed. This thermal protection is implemented when the heat flux sensor is not originally a heat flux sensor intended to operate at high temperatures. The sleeve 114 is made of a material thermally insulating preferably having a thermal conductivity of less than 0.1 Wm 'K 1, and in particular of the order of 0.03 Wm 'K '. This makes it possible to protect the sensors 112, 112a from potential direct jets of hot air, which may be at a temperature of up to approximately 650°C. The sleeve 114 thus makes it possible to improve the service life of the sensors 112, 112a, in particular in the event of a bursting pipe or a fire.

[0091] According to a particular aspect, the first 11a, second 11b and third 11b groups of sensors 112 are removable, in that they can be installed for the duration of the test and then removed, when it is necessary to carry out only ground test operations.

[0092] [Fig. 5] shows an example of an acquisition and control unit 500 which comprises, connected by a communication bus 510: a processor 501 or CPU (“Central Processing Unit” in English); a RAM 502 (“Random Access Memory” in English); a ROM 503 (“Read Only Memory” in English); a storage unit such as a hard disk or a storage media reader, such as an SD card reader 504 (“Secure Digital” in English); at least one communication interface 505, allowing the acquisition and control unit 500 to communicate with the sensors 112.

[0093] The processor is capable of executing instructions loaded into RAM from ROM, external memory (not shown), a storage medium (such as an SD card), or a communications network. When the equipment is powered on, the processor is capable of reading instructions from RAM and executing them. These instructions form a computer program causing the processor to implement all or part of the algorithms and steps described below.

[0094] All or part of the algorithms and steps described below can be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (“Digital Signal Processor” in English) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, for example an FPGA (“Field-Programmable Gate Array” in English) or an ASIC (“Application-Specific Integrated Circuit” in English).

[0095] An example of a method for determining the alert level consists, for the acquisition and control unit at a time 't', of:

[0096] - collect the value relating to the thermal flux which passes through each sensor 112 to the instant 't' and transmitted by said sensor 112,

[0097] - compare for each sensor, the value relative to the thermal flux collected with an expected reference value acquired for a turbojet of the same type in optimal operation;

[0098] - for each sensor 112, calculate the difference between the value of said sensor 112 and the expected reference value,

[0099] - for each sensor 112, classify the alert level of said sensor 112 in a category based on the difference thus calculated for said sensor 112.

[0100] For example, to give orders of magnitude that can be adapted according to the calibration of the thermal simulation models during development tests, if the difference is less than or equal to 30%, the corresponding sensor 112 is classified in class 1, if the difference is included in the interval 30%-80%, the corresponding sensor 112 is classified in class 2, if the difference is included in the interval 80%-150%, the corresponding sensor 112 is classified in class 3, if the difference is strictly greater than 150%, the corresponding sensor 112 is classified in class 4. Typically, this classification can be carried out after several successive time acquisitions, in order to increase the reliability of the calculations and the robustness of the anomaly detection method. For example, this classification can be carried out after three successive acquisitions, depending on the acquisition frequency of the sensors 112.

[0101] From this classification, the acquisition and control unit 500 informs the responsible person, for example, the pilot in the case of the aircraft 10 who can then take the appropriate corrective measures. The information of the responsible person can take different forms, such as for example the display of a message on a screen, the sending of a message on a computer, a tablet or a telephone, etc. The acquisition and control unit 500 can thus comprise display means arranged in the cockpit of the aircraft, or outside the aircraft.

[0102] The acquisition and control unit 500 thus comprises:

[0103] - collection means which are intended to collect the value relating to the flow thermal which passes through each sensor 112 at time 't' and transmitted by said sensor 112,

[0104] - calculation means which are intended, for each sensor 112, to calculate the difference between the value of said sensor 112 and the expected reference value, and

[0105] - classification means which are intended, for each sensor 112, to classify the alert level of said sensor 112 in a category based on the difference thus calculated for said sensor 112.

[0106] The acquisition and control unit 500 also comprises transmission means intended to transmit the necessary information to the responsible person.

[0107] The acquisition and control unit 500 is thus configured to analyze the data acquired by the sensors 112 in real time, but can also be configured to store this data and to then allow an analysis of this stored data.

[0108] To confirm the veracity of an alert level, the determination method is carried out several times to follow, in order to confirm that an alert level remains stable over time. According to a particular embodiment, the determination method is carried out three times successively, for example at a frequency of 1 Hz.

Claims

Claims

1. Assembly (100) comprising: - an inner tubular section (108) extending longitudinally between a first end, called the front end, and a second end, called the rear end, along a central line (X), - a fluid envelope (102) mounted coaxially with respect to the inner tubular section (108) and inside the inner tubular section (108), an interior space (110) being delimited between said inner tubular section (108) and said fluid envelope (102) and where a fluid flow (E) moves generally parallel to the central line (X) in said interior space (110) from the front to the rear of said inner tubular section (108), - a first group (11a) of at least three heat flow sensors (112) arranged in said interior space (110) at a rear zone of said assembly (100), where the sensors (112) of said first group (11a) are arranged generally in the same plane perpendicular to the central line (X),and where the sensors (112) of said first group (11a) are angularly distributed around the central line (X), said sensors (112) of said first group (11a) being configured to acquire data representative of a thermal flux, and, - an acquisition and control unit (500) connected to each sensor (112) of said first group (11a) and configured to receive the data acquired by each sensor (112) of said first group (11a), compare said data with reference values, and determine an alert level relating to said assembly (100) as a function of said comparison.

2. An assembly (100) according to claim 1, characterized in that said assembly comprises a second group (11b) of at least three heat flux sensors (112) arranged in said interior space (110) at a front zone of said assembly (100), where the sensors (112) of said second group (11b) are arranged generally in the same plane perpendicular to the central line (X), where the sensors (112) of said second group (11b) are angularly distributed around the central line (X), said sensors (112) of said second group (11b) being configured to acquire data representative of a heat flux, and where the sensors (112) of said second group (11b) are connected to said acquisition and control unit, the unit and acquisition and control being configured to receive the data acquired by each sensor of said second group (11b), compare said data with reference values, and determine an alert level relating to said assembly (100) based on said comparison.

3. An assembly (100) according to claim 2, characterized in that said assembly comprises a third group (11c) of at least three heat flux sensors (112) arranged in said interior space (110) between said first (11a) and second (11b) groups, wherein the sensors (112) of said third group (11c) are arranged generally in the same plane perpendicular to the central line (X), wherein the sensors (112) of said third group (11c) are angularly distributed around the central line (X), wherein said sensors (112) of said third group (11c) are configured to acquire data representative of a heat flux, and wherein the sensors (112) of said third group (11c) are connected to said acquisition and control unit, the acquisition and control unit being configured to receive the data acquired by each sensor of said third group (11c), compare said data with reference values,and determining an alert level relating to said assembly (100) based on said comparison.,

4. Assembly (100) according to one of claims 1 to 3, characterized in that for each group (11a, 11b, 11c), there are three sensors arranged in a transverse plane (YZ) perpendicular to the central line (X) and distributed at an angle of between 110° and 130° around the central line (X), and where a first (112a) of said at least three sensors (112) is arranged in the upper part of the assembly (100), above said envelope of a fluid (102) and on a vertical axis extending generally perpendicular to the central line (X).

5. Assembly (100) according to one of claims 1 to 4, characterized in that each sensor (112) comprises an effective measuring surface (S) which is generally planar, where a normal of said surface (S) extends at an angle of between +30° and -30° relative to said central line (X).

6. Assembly (100) according to claim 5, characterized in that said normal of the surface (S) of said sensor (112) extends parallel to said central line (X).

7. Assembly (100) according to claim 5 or 6, characterized in that said surface (S) of each sensor (112) is housed in a sleeve (114) made of thermally insulating material with a thermal conductivity of less than 0.1 Wm 'K1.

8. Assembly (100) according to one of claims 1 to 7, characterized in that said assembly (100) further comprises an outer tubular section (106) mounted coaxially with respect to the inner tubular section (108), outside the inner tubular section (108), where said assembly (100) is an aircraft turbojet engine (10) in which the fluid casing (102) is an engine channeling a flow of hot gas, and where the outer tubular section (106) and the inner tubular section (108) respectively constitute an outer wall (106) and an inner wall (108) of a fixed internal structure (104).

9. Assembly (100) according to claim 8, characterized in that said first (11a), second (11b) and third (11c) groups of sensors (112) are removable from said assembly (100).

10. Aircraft (10) comprising at least one assembly (100) according to one of claims 1 to 9.

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