Temperature measuring device with optical fiber insulated from fixed wall by part comprising cork

Abstract

The invention is directed to a device for measuring the temperature of a fluid flowing on an outer wall (12) of an object, comprising an optical fiber (16) extending along a longitudinal axis X and a flexible shroud (40) surrounding said optical fiber, characterized in that the measuring device (2) comprises an elongate heat-insulating portion (22), the invention relates to an optical fiber (10) comprising an elongate insulating portion (22) comprising cork and having at least two opposite faces (24, 26), an inner face (24) and an outer face (26), and characterized in that a shield (40) surrounds said insulating portion (22), excluding the outer face (26), and keeps the inner face (24) of the insulating portion facing the optical fiber over at least a portion of the length of the optical fiber along a longitudinal axis X, the lateral dimension of the inner face of the insulating portion is at least larger than the diameter of the fiber.

Description

Technical Field

[0001] The invention relates to a measuring device which can be attached to an outer wall of a moving or fixed object located in a fluid flow to measure physical quantities. More specifically, the invention is suitable for measuring parameters for characterizing air flow over an aircraft surface. Background Art

[0002] During flight tests, sensors are installed on the outer surface of the aircraft to perform different types of measurements. The results are studied so that the behavior of the aircraft in flight can be understood and improved or performance levels can be verified. Depending on the specific application, aerodynamic phenomena on the aircraft can be detected and localized, for example.

[0003] Patent application EP 4067827 describes a device for measuring physical quantities (such as temperature), which is intended to be attached to a wall of a mobile object or a fixed object in a flow in which it is desired to characterize the measured physical quantity. The device comprises a support having a face intended to be in contact with the wall and an opposite face in the flow, which is called a free face. The support comprises a recess in which sensors are accommodated, which are provided with an orifice leading to a cavity in which a flexible printed circuit is present on one side of the free face. The circuit is arranged inverted in the cavity, and a sensor fixed to the circuit is suspended in the recess. Therefore, the sensor makes it possible to measure the temperature of the air flow flowing along the wall to which the measuring device is fixed.

[0004] When the support is applied to the engine wall, the temperature can be very high and interfere with the measurement of the temperature of the flow flowing along the wall by the sensor suspended above the wall. Summary of the invention

[0005] The present invention aims to propose a new architecture of a flow temperature measurement device so as to alleviate this disadvantage.

[0006] To this end, the invention relates to a device for measuring the temperature of a fluid flowing on the outer wall of an object, comprising an optical fiber and a flexible shield surrounding said optical fiber, said optical fiber extending along a longitudinal axis X, characterized in that the measuring device comprises an elongated insulating portion, which consists of cork and has at least two opposite faces, namely an inner face and an outer face, and characterized in that the shield surrounds said insulating portion, except for the outer face, and keeps the inner face of the insulating portion facing the optical fiber along the longitudinal axis X over at least a portion of its length, the transverse dimension of the inner face of the insulating portion being at least greater than the diameter of the optical fiber.

[0007] The present invention provides at least one of the following optional features taken alone or in combination.

[0008] The insulating part, whose inner and outer faces are at least partially coated with a layer which is a silicone elastomer, is then referred to as an insulating part with a seal.

[0009] The optical fiber is coated with a jacket and is referred to as a jacketed optical fiber, the jacket surrounding the jacketed optical fiber and a thermally insulating portion having a seal, except for an outer portion which is at least partially coated with a silicone elastomer.

[0010] The jacketed optical fiber is in contact with the thermal insulation portion having the seal over the entire length of the thermal insulation portion.

[0011] The shield has a polyhedral form with six faces including at least two flat parallel faces including a face having an open cavity in a form complementary to the insulating portion having a seal.

[0012] The thickness of the shield between the two flat parallel faces at the jacketed optical fiber substantially corresponds to the diameter of the jacketed optical fiber or is even slightly larger.

[0013] The insulation is made of natural or expanded cork sheets.

[0014] The shield has a trapezoidal cross section, the shield, the insulating portion with a seal, and the jacketed optical fiber have a symmetrical form relative to a plane P passing through the longitudinal axis X, where the jacketed optical fiber is positioned on the insulating portion with a seal.

[0015] The invention also relates to a structure comprising a wall provided with a measuring device having at least one or more of the above characteristics, and to an aircraft comprising such a structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other objects, features and advantages will emerge from the following description of the invention, given purely as a non-limiting example, with reference to the accompanying drawings, in which: [ Figure 1 ] is a schematic perspective view of an aircraft that can be provided with the measuring device according to the present invention; [ Figure 2 ] is a perspective schematic diagram of an aircraft propulsion assembly provided with a measuring device according to the present invention; [ Figure 3 ] is a side cross-sectional view of a measuring device according to the present invention attached to a wall of an object. DETAILED DESCRIPTION

[0017] The measuring device 2 according to the invention is equipped with a structure 3 according to Figures 1 to 3 The application shown is a certain structure 3 of an aircraft 4, namely more particularly a nacelle 6 of a power plant 8 in the context of flight testing. The invention relates to a device 2 for measuring a flow along an outer wall 12 of the nacelle 6 and caused by Figure 2The two streamlines shown in illustrative diagrams represent the temperature of the air flow 10. Any other application of the device on an outer wall 12 of a mobile object such as an aircraft 4 or a stationary object situated in a fluid flow for measuring its temperature can be envisaged.

[0018] like Figure 3 As represented in , the measuring device 2 comprises a sensor 14 intended to measure the temperature of the flow 10. In order to allow the temperature of the flow 10 to be measured, the sensor 14 must be fixed to the wall 12 of the nacelle 6. The sensor is an optical fiber 16, the operation of which is of a known type and will not be described in more detail. The advantage of the optical fiber is that it can withstand the high temperatures inherent in the nacelle 6 and is flexible to follow the nacelle contour. The optical fiber also has the advantage of being small in size and light in weight. This enables the optical fiber to be applied to large-sized objects like nacelles through its possible length. The optical fiber provides high measurement speed and accuracy. The optical fiber can measure physical quantities such as the temperature of the air flow flowing along the wall of the object to which it is attached, that is, in the reserved application, the temperature of the flow flowing along the outer wall 12 of the nacelle. The optical fiber provides the possibility of making multiple measurements over all or part of its length. The optical fiber 16 is coated with a flexible sheath 18, which is made of polytetrafluoroethylene (also called PTFE) for example, which provides high temperature resistance. The sheath 18 completely surrounds the optical fiber 16 and has the form of a sleeve. In the following, the optical fiber 16 coated with the jacket 18 will be designated as a jacketed optical fiber 20. The jacket 18 can be made of any other type of material suitable for the environment, such as polyetheretherketone (also known as PEEK), glass fiber reinforced polyamide or even metal. The jacketed optical fiber extends along a longitudinal axis X.

[0019] A jacketed optical fiber 20 is placed in the air flow 10 and is thermally insulated from the high temperatures radiated by the wall 12 of the nacelle via an insulating portion 22 comprising cork. The insulating portion 22 has an elongated form extending along the jacketed optical fiber 20 between the jacketed optical fiber and the wall 12 of the object, here the nacelle. The insulating portion 22 comprises at least two opposite faces 24, 26, a so-called inner face 24 situated on one side of the jacketed optical fiber and another so-called outer face 26 situated on the opposite side. The insulating portion remains facing the optical fiber over at least a portion of its length and, in the form shown, over the entire length of the optical fiber. The inner face 24 of the insulating portion 22 has a transverse dimension (i.e. at right angles to the longitudinal axis X) which is at least greater than the diameter of the optical fiber over the entire length of the optical fiber along the axis X and, in the form shown, greater than the diameter of the jacketed optical fiber. Cork is a very good insulator, with the added advantage of being light and easy to handle, allowing a firm fixation of the measuring device depending on the environment in which it will be in the aircraft when it is in flight. More specifically, the material may be natural cork, expanded cork, or even a combination of, for example, cork and another material that offers additional technical advantages. For example, the material may be rubber: the rubber increases the impermeability and allows the measuring device to follow slightly more closely the form of the wall to which it is applied. In the form shown, the insulating portion 22 is made entirely of natural or expanded cork.

[0020] exist Figure 3 In the form shown, the insulating portion 22 consisting of cork takes the form of a sheet: it has the form of a parallelepiped with six faces and of a rectangular cross-section, but any other form is possible as long as it allows it to be inserted between the jacketed optical fiber 20 and the wall 12 of the object (here the nacelle of the aircraft) and thus to thermally insulate the optical fiber from the wall 12. The length of the portion 22 is preferably equal to or greater than the length of the optical fiber. The thickness and width of the portion 22 are determined to ensure sufficient insulation while providing a reduced volume and depend on the circumstances and the materials used. The width of the portion 22 in the form of a sheet is greater than the diameter of the jacketed optical fiber. In the example shown, the insulating portion 22 has two parallel longitudinal faces, one of which is a so-called inner face 24 on which the optical fiber rests on the central longitudinal axis X, and the other is a so-called outer face 26, which is a parallel longitudinal face opposite to the inner face. The longitudinal faces 28, 30 connecting the inner face and the outer face are called lateral longitudinal faces. The portion 22 is Figure 2 The transverse faces 32, 34, which are not visible in the figure but whose positions are indicated by the arrows, are the last two faces of the six faces of the sheet 22. They are parallel to each other, but may not be parallel.

[0021] like Figure 3As shown, sealing layers 36, 38 are at least partially applied to at least two faces (respectively 24, 26) of the insulating portion 22, one of which is intended to be fixed to the wall 12. In the example shown, the insulating portion 22 is sandwiched between two sealing layers 36, 38. The sealing layers 36, 38 can be made of silicone elastomers of the RTV (room temperature vulcanization) 106 type, for example. The sealing layers 38 make it possible to improve the fixation of the insulating portion 22 containing cork to the wall 12. The use of RTV silicone elastomers also makes it possible to withstand high temperatures, while additionally making it possible to insulate the jacketed optical fiber from vibrations. Each layer 36, 38 is applied to a portion or all of the surface of the longitudinal inner face 24 and the longitudinal outer face 26 of the insulating portion 22. In the embodiment described as an example, each layer 36, 38 completely coats the faces 24, 26 of the portion 22, respectively. The insulating portion 22 coated with the sealing layers 36, 38 will be referred to as the insulating portion 23 with a sealing portion 23 hereinafter.

[0022] The jacketed optical fiber 20 is positioned on and along the insulating portion 23 with a seal. The jacketed optical fiber 20 and the insulating portion 23 with a seal (except for the face 26 coated with the layer 38 and intended to be fixed to the wall 12) are covered by a shield 40. The shield 40 enables them to be kept against each other. In the form shown, the shield keeps the inner face 24 of the insulating portion facing the optical fiber along the longitudinal axis X over the entire length of the optical fiber, the jacketed optical fiber being in contact with the insulating portion over at least a portion of the insulating portion, in the form shown over the entire length of the insulating portion. According to another possible form, the jacketed optical fiber can be separated from the insulating portion with a seal by the shield. The free face 26 makes it possible to improve the fixation to the wall 12 of the nacelle via the sealing layer 38 as previously seen. Preferably, the thickness of the shield 40 on the jacketed optical fiber is such that the jacketed optical fiber is as close to the air flow 10 as possible so as to more accurately measure the temperature of the air flow when it is held by the shield 40. Figure 3 As shown, in the illustrated embodiment, in the transverse section of the jacketed optical fiber and the jacket and in the central longitudinal plane of symmetry P, the thickness of the jacket 40 substantially matches the thickness of the jacketed optical fiber or is even slightly greater to ensure the continuity of the jacket surface. In addition, the layer 36 on the inner face 24 of the insulating portion 22 makes it possible to facilitate the fixing of the insulating portion 23 with the seal to the jacket 40. The surface of the layer 38 and the surface of the face 41 of the jacket 40 intended to be attached to the wall 12 are flush with each other, thereby forming the same surface intended to be attached to the wall of the nacelle.

[0023] The main function of the shield 40 is to provide a fairing for the sensor 14 (in the example shown, the jacketed optical fiber 20) and the thermal insulation 23 with a seal to protect them from any type of external aggression (impact of objects, birds or other things on the air intake, bad weather or any other type of aggression). The jacketed optical fiber 20 and the thermal insulation 23 with a seal (except for the layer 38 as seen above) are embedded in the shield 40. In the example described, the jacketed optical fiber 20 is in contact with the thermal insulation 23 with a seal, but they can be separated by the shield, both embedded inside the shield. The flexible shield 40 can be produced from a polymer material, for example from a compound of polyurethane or silicone or any other type of material, which is flexible enough to closely follow the contours of the wall 12 and makes it possible to protect the jacketed optical fiber and withstand the high temperatures of the environment. This flexible shield can be produced by molding, machining or any other known type of manufacturing method.

[0024] The flexible shield 40 can be produced from a polymer material, such as a compound of polyurethane or silicone or any other type of material that is flexible enough to closely follow the contours of the aircraft and that allows the jacketed optical fiber to be protected and withstand the high temperatures of the environment. The flexible shield can be produced by molding, machining or any other known type of manufacturing method.

[0025] exist Figure 3 In the embodiment shown, the shroud 40 has an external overall polyhedral form with 6 faces, with two cavities 42, 44, one open cavity 42 in the form complementary to the insulating portion 23 with a seal, and one cavity 44 in the form complementary to the jacketed optical fiber. The shroud's 6 faces are as follows: - a face 41 intended to come into contact with the wall 12 of the nacelle, flush with the surface of the layer 38 intended to come into contact with the wall 12 (as seen previously), the cavity 42 open towards said face 41 in the form complementary to the insulating portion 23 with a seal. Thus, the portion 23 inside the cavity 42 is incorporated in the shroud 40. This portion is sheathed (except for its face 26 coated with the layer 38, which forms the same surface as the face 41 of the shroud, allowing fixation to the wall 12; - a free second face 46, parallel to the first face 41 and opposite to it; - two faces 48, 50 forming the longitudinal lateral edges of the shroud. The lateral edges of the shroud have a thickness that tapers towards the periphery, making it possible to provide a surface that only very weakly disturbs the aerodynamic flow; - two faces 52, 54 (at Figure 2 ), wherein one face 54 is intended to be connected to a measured data management unit 56 and the other face 52 corresponds to the free lateral end of the shield. Figure 3The cross-sectional profile of the shield shown in is a trapezoid. The shield, the thermal insulation with the seal, and the jacketed optical fiber have a symmetrical form relative to a plane P passing through the longitudinal axis X, at which the jacketed optical fiber is positioned on the thermal insulation with the seal. As indicated above, the shield 40 can have any type of form: thus, the free transverse face 52 forming one of the longitudinal ends of the shield can have a thickness that tapers towards the longitudinal side opposite the unit 56, making it possible to provide a surface that disturbs the aerodynamic flow as weakly as possible in the same way as the two faces 48, 50 of the shield. Then, in this case, the face 52 is inclined and does not form a right angle with the faces 41 and 46.

Claims

1. A device for measuring the temperature of a fluid flowing on an outer wall (12) of an object (4, 6), said device comprising an optical fiber (16) and a flexible shield (40) surrounding said optical fiber, said optical fiber extending along a longitudinal axis X, characterized in that The measuring device (2) comprises an elongated insulating portion (22) comprising cork and having at least two opposite faces (24, 26), namely an inner face (24) and an outer face (26), and is characterized in that the shield (40) surrounds the insulating portion (22), except for the outer face (26), and keeps the inner face (24) of the insulating portion facing the optical fiber along the longitudinal axis X over at least a portion of the length of the optical fiber, the transverse dimension of the inner face of the insulating portion being at least greater than the diameter of the optical fiber.

2. The measuring device according to claim 1, characterized in that The inner face (24) and the outer face (26) of the insulating part (22) are each at least partially coated with a layer (36, 38) which is a silicone elastomer, and the insulating part (22) is then referred to as an insulating part (23) with a seal.

3. The measuring device according to claim 2, characterized in that The optical fiber (16) is coated with a jacket (18) and is referred to as a jacketed optical fiber (20), and the shield (40) surrounds the jacketed optical fiber (20) and the thermally insulating portion (23) having a seal, except for the outer portion (26) which is at least partially coated with a silicone elastomer.

4. The measuring device according to claim 3, characterized in that The sheathed optical fiber (20) is in contact with the heat-insulating portion (23) with a seal over the entire length of the heat-insulating portion with a seal.

5. The measuring device according to any one of claims 2 to 4, characterized in that The shield (40) has a polyhedral form with six faces, including at least two flat parallel faces (41, 46), including a face (41) having an open cavity (42) in a form complementary to the insulating portion (23) having a seal.

6. The measuring device according to claims 3 and 5, characterized in that The thickness of the jacket (40) between the two faces (41, 46) at the jacketed optical fiber (20) corresponds substantially to the diameter of the jacketed optical fiber or is even slightly larger.

7. The device according to any one of claims 1 to 6, characterized in that The insulation part (22) is a natural or expanded cork sheet.

8. The device according to claims 3 and 5, characterized in that The shield (40) has a trapezoidal cross-section, and the shield, the insulating portion with a seal, and the sheathed optical fiber have a symmetrical form relative to a plane P passing through the longitudinal axis X, and the sheathed optical fiber is positioned on the insulating portion with a seal at the plane.

9. A structure having a wall (12) provided with a measuring device according to one of claims 1 to 8.

10. An aircraft, characterized in that: The aircraft comprises a structure (3) according to claim 9.

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