A pipe joint assembly for fluid multi-parameter measurement

Abstract

The present disclosure provides a pipe joint assembly for multi-parameter measurement of fluid, including a four-way pipe joint and a composite sensor arranged in the four-way pipe joint, the four-way pipe joint includes a first joint and a second joint for fixing the composite sensor and the optical cable, and a third joint and a fourth joint for transmitting pipeline liquid; the composite sensor includes a housing and a fiber grating temperature sensor arranged in the housing, and a fiber grating temperature pressure sensor, a fiber grating pressure pulsation sensor, a first fiber grating flow velocity sensor and a second fiber grating flow velocity sensor arranged on the housing. Among them, one end of the housing is embedded in the first joint and fixedly connected to the first joint, and the other end is embedded in the second joint and fixedly connected to the second joint; the optical cable extending from the composite sensor is led out from the sealed connection between the first joint and the second joint. The above-mentioned pipe joint assembly for multi-parameter measurement of fluid disclosed in the present disclosure can effectively enhance the detection of hydraulic multi-parameters and reduce the number of measuring points, thereby reducing the risk of leakage in the hydraulic pipeline.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of fluid equipment, and specifically provides a pipe joint assembly for multi-parameter measurement of fluid. Background Art

[0002] In the hydraulic transmission system, the flow rate (kinetic energy) of the medium is low, and the potential energy generated is relatively low, which can be ignored. The power is transmitted only by the pressure energy of the working medium, which is the so-called hydrostatic transmission. With the application of artificial intelligence in engineering machinery and other fields, as a "small but powerful" hydraulic system, it can well amplify electronic information into mechanical actions through the hydraulic system. Therefore, the hydraulic system is an important intermediate link in the operation of intelligent machinery. In order to ensure the normal operation of the hydraulic system, it is usually necessary to monitor the operating parameters of the hydraulic system in real time, so as to timely understand the operating status of the hydraulic system, especially to give early warning before the hydraulic system fails; or, when the hydraulic system fails, to provide analysis parameters for timely diagnosis of the type and cause of the fault.

[0003] In hydrostatic transmission, the flow of liquid in the pipeline forms a corresponding relationship with the pressure difference in the flow interval. The flow rate in the pipeline can correspond to the flow velocity, so the flow rate in the pipeline can be obtained by checking the pressure difference. In this way, the detection of three parameters of temperature, pressure and flow in the hydraulic system can be reduced to the detection of two parameters of temperature and pressure. The fiber Bragg grating sensor has the characteristics of anti-electromagnetic interference, small size and light weight, and can detect two parameters of temperature and pressure. In addition, multiple fiber Bragg grating sensors can be connected in series to form a distributed detection matrix, which can greatly reduce the number of detection lines.

[0004] In the prior art of diagnosing hydraulic system faults, usually only one of the temperature, pressure and flow of the hydraulic system is detected, so it is difficult to diagnose the fault of the hydraulic system. At present, this diagnosis needs to rely on the operating parameters such as temperature, pressure, flow and so on inside the hydraulic system to accurately determine the type or cause of the fault. However, if all sensors for detecting each of the above parameters are set in the hydraulic system, multiple detection points must be set in the hydraulic pipeline (multiple holes need to be opened in the hydraulic pipeline), which increases the risk of hydraulic pipeline leakage. In addition, due to the limited space of the hydraulic system of engineering machinery and mining machinery, and the large total volume of the aforementioned multiple sensors, it is difficult to simultaneously arrange temperature, pressure, flow and flow pulsation detection instruments at key positions for the diagnosis of hydraulic faults. In addition, if sensors for detecting temperature, pressure and flow are arranged in the hydraulic pipeline at the same time, there will be more detection lines (lines connecting sensors), which will not only complicate the structure, but also affect the appearance of the hydraulic system. Summary of the invention

[0005] In order to solve the above-mentioned problems in the prior art, that is, in order to solve the problem that in the prior art, multiple detection points need to be set on the hydraulic pipeline in order to install temperature, pressure and flow sensors at the same time, thereby increasing the risk of hydraulic pipeline leakage, the present disclosure provides a pipe joint assembly for fluid multi-parameter measurement, the pipe joint assembly for fluid multi-parameter measurement comprising a four-way pipe joint and a composite sensor arranged in the aforementioned four-way pipe joint, the aforementioned four-way pipe joint comprising a first joint, a second joint and a third joint and a fourth joint for fixing the aforementioned composite sensor and the optical cable, and transmitting the pipeline liquid; the aforementioned composite sensor comprises a housing, a fiber grating temperature sensor, a fiber grating temperature pressure sensor, a fiber grating pressure pulsation sensor, a first fiber grating flow velocity sensor and a second fiber grating flow velocity sensor, and an optical cable composed of multiple optical fibers: one end of the aforementioned housing is embedded in the aforementioned first joint and connected to the optical cable. The aforementioned first joint is fixedly connected, and the other end of the aforementioned shell is embedded in the aforementioned second joint and fixedly connected to the aforementioned second joint; each of the aforementioned optical fibers in the optical cable composed of multiple optical fibers is engraved with a grating, thereby forming the aforementioned fiber grating temperature sensor, the aforementioned fiber grating temperature pressure sensor or the aforementioned fiber grating pressure pulsation sensor, the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor; the aforementioned optical cables at both ends of the aforementioned shell pass through the sealed connection parts of the aforementioned first joint and the aforementioned second joint; the aforementioned fiber grating temperature sensor is arranged inside the aforementioned shell, and can detect the temperature of the liquid in the aforementioned four-way pipe joint; the aforementioned fiber grating temperature pressure sensor is arranged on the aforementioned shell, and can detect the comprehensive data of the temperature and pressure of the liquid in the aforementioned four-way pipe joint; the aforementioned fiber grating pressure pulsation sensor is arranged on the aforementioned shell, and can detect the pressure fluctuation of the liquid in the aforementioned four-way pipe joint.

[0006] Optionally, the pipe joint assembly also includes a first sealing plug arranged at the first joint and a second sealing plug arranged at the second joint, the first sealing plug and the second sealing plug respectively allow the optical cable to pass through, thereby forming a seal for the first joint and the second joint and the optical cable; the sealing structure is respectively connected to the ends of the first joint and the second joint, thereby respectively restricting the first sealing plug and the second sealing plug in the first joint and the second joint, and enabling the first sealing plug and the second sealing plug to have a tendency to move toward each other, so as to position the composite sensor.

[0007] Optionally, the sealing structure includes a nut, a clamping cover plate is provided at one end of the nut, and the clamping cover plate can clamp the sealing plug through an adjusting gasket, the adjusting gasket is arranged between the first sealing plug and the second sealing plug and their corresponding clamping cover plates, and can allow the optical cable to pass through, the adjusting gasket is set as an elastic sealing material, and plays an auxiliary sealing role after being deformed by pressure to prevent liquid leakage from the first joint and the second joint; the clamping cover plate is provided with a through hole, and the diameter of the through hole is larger than the diameter of the composite sensor to ensure that the composite sensor can pass through smoothly; the nut is threadedly connected to the first joint and the second joint, and a groove is provided at the connection between the first joint and the second joint and the nut, and a stop gasket is provided between the nut and the first joint and the second joint, the inner stop portion of the stop gasket can be bent and fitted into the groove to prevent the stop gasket from rotating, and the outer stop portion of the stop gasket can be bent and fitted to the outer groove of the nut or the edge of the nut to prevent the nut from loosening.

[0008] Optionally, a supporting gasket is provided between the first sealing plug and the second sealing plug and their corresponding clamping cover plate, and the supporting gasket can abut against the end faces of the first sealing plug and the second sealing plug or the adjusting gasket under the push of the clamping cover plate to support the relative position of the first sealing plug and the second sealing plug and indirectly locate the position of the composite sensor.

[0009] Optionally, the composite sensor further comprises a positioning member, which is arranged on the surface of the shell and is located at both ends of the shell and can be connected to the first sealing plug and the second sealing plug to limit the rotation of the shell relative to the first sealing plug or the second sealing plug.

[0010] Optionally, the positioning member is configured as a positioning claw structure, and at least two positioning claws are provided at the same end of the shell and are evenly and symmetrically arranged along the outer surface of the shell.

[0011] Optionally, a support frame is provided inside the first sealing plug and the second sealing plug respectively, and the support frame can increase the support strength of the first sealing plug and the second sealing plug, so that the elastic deformation of the first sealing plug and the second sealing plug is controlled within a limited range.

[0012] Optionally, a through hole is provided on the shell; the composite sensor also includes an elastic sheet arranged at the through hole, the elastic sheet is sealed and connected to the shell and thus closes the through hole; the fiber grating pressure pulsation sensor includes a first fiber grating pressure pulsation sensor fixed to the outside of the elastic sheet and a second fiber grating pressure pulsation sensor fixed to the inside of the elastic sheet, so as to detect the pressure fluctuation by the fluctuation of the difference between the data detected by the first fiber grating pressure pulsation sensor and the data detected by the second fiber grating pressure pulsation sensor.

[0013] Optionally, the shell includes a first shell, a second shell and a connecting cover, the first shell is located on one side of the connecting cover and is fixedly connected to the connecting cover, and the second shell is located on the other side of the connecting cover and is fixedly connected to the connecting cover; the composite sensor also includes an airbag arranged in the first shell, and an elastic material is filled between the airbag and the shell and between the airbag and the connecting cover, so as to encapsulate the airbag in the elastic material to form an elastomer; the elastic sheet does not contact the airbag or the elastic material, so that a cavity is formed between the airbag or the elastic material and the connecting cover, and the cavity is filled with hydrogen or helium at a pressure of 0.1MPa to ensure that the elastic sheet has a certain back pressure on the outside; the spacing of the cavity is used to ensure that the elastic sheet does not touch the elastomer when it is deformed to the maximum.

[0014] Optionally, the composite sensor further comprises heat-conducting silicone oil filled in the second shell, the heat-conducting silicone oil immerses the fiber Bragg grating temperature sensor so as to enhance the temperature consistency between the shell and the fiber Bragg grating temperature sensor; the composite sensor further comprises a first fiber Bragg grating flow velocity sensor and a second fiber Bragg grating flow velocity sensor, the first fiber Bragg grating flow velocity sensor and the second fiber Bragg grating flow velocity sensor are symmetrically arranged on the outside of the shell along the axis of the shell, so as to detect the environment in which the composite sensor is located by the difference between the data detected by the first fiber Bragg grating flow velocity sensor and the data detected by the second fiber Bragg grating flow velocity sensor The first fiber grating flow sensor is aligned with the third joint, and the second fiber grating flow sensor is aligned with the fourth joint, or the first fiber grating flow sensor is aligned with the fourth joint, and the second fiber grating flow sensor is aligned with the third joint, and the first fiber grating flow sensor and the second fiber grating flow sensor are symmetrically arranged on the outside of the shell along the axis of the shell, so as to detect the flow rate of the liquid in the four-way pipe joint by the difference between the data detected by the first fiber grating flow sensor and the data detected by the second fiber grating flow sensor.

[0015] Optionally, the aforementioned composite sensor also includes a heat conducting plate and a first fixing plate and a second fixing plate which are arranged in the aforementioned second shell and fixedly connected to the aforementioned second shell, one side wall of the aforementioned heat conducting plate is fixedly connected to the aforementioned first fixing plate to ensure that heat conduction can be carried out between the aforementioned heat conducting plate and the aforementioned first fixing plate in a timely manner; the other side wall of the aforementioned heat conducting plate is relatively movably connected to the aforementioned second fixing plate, so that the aforementioned other end of the aforementioned heat conducting plate can move freely when the aforementioned heat conducting plate is deformed by heat; the aforementioned fiber grating temperature sensor is fixedly connected to the aforementioned heat conducting plate, so that the aforementioned fiber grating temperature sensor can increase the longitudinal deformation of the grating as the heat conducting plate is heated and elongated, thereby making the aforementioned heat conducting plate have a sensitivity enhancing effect on the aforementioned fiber grating temperature sensor.

[0016] Optionally, the composite sensor further comprises a heat conductive wire penetrating the second shell, and the heat conductive wire is fixedly connected to the first fixing plate so that the heat conductive wire can establish a rapid heat transfer channel between the liquid in the environment where the composite sensor is located and the first fixing plate.

[0017] Optionally, the aforementioned composite sensor also includes a first fiber grating flow velocity sensor and a second fiber grating flow velocity sensor, and the aforementioned first fiber grating flow velocity sensor and the aforementioned second fiber grating flow velocity sensor are symmetrically arranged on the outside of the aforementioned shell along the axis of the aforementioned shell, so as to detect the flow velocity and flow direction or change in flow velocity of the liquid in the environment where the aforementioned composite sensor is located by the difference between the data detected by the aforementioned first fiber grating flow velocity sensor and the data detected by the aforementioned second fiber grating flow velocity sensor.

[0018] Optionally, the aforementioned composite sensor also includes a plurality of optical fibers passing through the aforementioned shell, the optical fibers have the same material and specification, each of the optical fibers is engraved with a grating in a specific portion inside or on the surface of the shell, the gratings have the same characteristic values, and thus form the fiber grating temperature sensor, the fiber grating temperature pressure sensor, the fiber grating pressure pulsation sensor, the first fiber grating flow rate sensor and the second fiber grating flow rate sensor; the composite sensor also includes a connector connected to the end of the optical fiber away from the sensor.

[0019] Optionally, the shell is configured to be in the shape of a rugby ball or an ellipsoid.

[0020] Based on the foregoing description, it can be understood by those skilled in the art that, in the aforementioned technical solution of the present disclosure, by setting the housing to have a streamlined outer surface, the resistance of the composite sensor to the detection liquid can be effectively reduced; by setting the fiber Bragg grating temperature sensor inside the housing, the composite sensor can be free from the interference of the pressure of the liquid in the environment detected by the sensor; by setting the fiber Bragg grating temperature and pressure sensor on the housing, the composite sensor can detect the comprehensive data of the temperature and pressure of the liquid in the environment through the fiber Bragg grating temperature and pressure sensor and then convert the temperature detection value into the pressure value detection; by setting the fiber Bragg grating pressure pulsation sensor on the housing, the composite sensor can detect the pressure fluctuation of the liquid in the environment through the fluctuation amount and time difference of the difference between the data of the two grating pressure pulsation sensors at a certain center. Therefore, the composite sensor of the present disclosure can not only detect the pressure, temperature and pressure pulsation of the liquid in the environment, but also can be built into the pipeline. At the same time, by centrally arranging multiple sensors on or inside the housing, the multiple measuring points required for comprehensive parameters of the hydraulic system are reduced to only one detection point to complete the measurement of pressure, temperature and pressure pulsation, greatly reducing the risk of hydraulic pipeline leakage.

[0021] Furthermore, by symmetrically arranging the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor on the outer side of the shell along the axis of the shell, and making the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor located in the flow direction of the flowing liquid during use, and ensuring that the fiber grating characteristic values ​​in the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor are the same, the composite sensor can eliminate the influence of temperature factors in the same temperature environment field through the difference between the data detected by the first fiber grating flow velocity sensor and the data detected by the second fiber grating flow velocity sensor, and thus obtain the pressure difference of the liquid in the environment, and the flow velocity of the liquid at the sensor can be obtained from the pressure difference, and then the flow rate of the liquid at the sensor can be converted into the flow rate of the liquid at the sensor in combination with the flow area; the fluctuation of the flow velocity can also be detected by the fluctuation of the pressure difference; the direction of the flow velocity can also be measured by the change of the direction of the pressure difference.

[0022] Furthermore, by setting each of the aforementioned sensors as fiber grating sensors, the composite sensor has the characteristics of anti-electromagnetic interference, small size and light weight, and has better performance, and multiple fiber grating sensors can be used as a detection line through an optical cable (including multiple optical fibers), which greatly reduces the number of detection lines compared with the prior art, thereby making the detection wiring of the hydraulic system more beautiful. Therefore, the engineering machinery with the composite sensor disclosed in the present invention can systematically collect hydraulic system parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The preferred embodiments of the present disclosure are described below with reference to the accompanying drawings, taking a four-way pipe joint as an example, wherein:

[0024] Figure 1 is a cross-sectional view of a pipe joint assembly for fluid multi-parameter measurement in a preferred embodiment of the present disclosure;

[0025] Figure 2 is an exploded schematic diagram of the structure of the composite sensor in a preferred embodiment of the present disclosure (optical fiber is not shown);

[0026] Figure 3 is a front view of a composite sensor in a preferred embodiment of the present disclosure (optical fiber is not shown);

[0027] Figure 4 yes Figure 3 The cross-sectional view along the AA direction;

[0028] Figure 5 yes Figure 3 The cross-sectional view along the BB direction;

[0029] Figure 6 It is a schematic diagram of the structure of the support gasket in the preferred embodiment of the present disclosure.

[0030] List of reference numerals:

[0031] 1. four-way pipe joint; 11. first joint; 12. second joint; 13. third joint; 14. fourth joint;

[0032] 2. Composite sensor; 201. Shell; 2011. First shell; 2012. Second shell; 2013. Connecting cover; 202. Fiber Bragg Grating temperature sensor; 203. Fiber Bragg Grating temperature pressure sensor; 204. First Fiber Bragg Grating pressure pulsation sensor; 205. Second Fiber Bragg Grating pressure pulsation sensor; 206. First Fiber Bragg Grating flow velocity sensor; 207. Second Fiber Bragg Grating flow velocity sensor; 208. Elastic sheet; 209. Elastomer; 2091. Airbag; 2092. Elastic material; 210. Heat conducting sheet; 211. Heat conducting wire; 212. First fixing plate; 213. Second fixing plate; 214. First optical fiber group; 215. Second optical fiber group; 216. First connector; 217. Second connector; 218. Cavity; 219. Positioning member;

[0033] 3. The first sealing plug;

[0034] 4. Second sealing plug;

[0035] 5. Sealing structure; 501. Nut; 5011. Groove; 502. Pressing cover plate; 5021. Through hole; 503. Adjusting gasket; 504. Stop gasket; 505. Supporting gasket; 5051. Groove; 506. Supporting frame. DETAILED DESCRIPTION

[0036] It should be understood by those skilled in the art that the embodiments described below are only preferred embodiments of the present disclosure, which are intended to explain the technical principles of the present disclosure, and do not mean that the technical principles of the present disclosure can only be realized through the preferred embodiments, so the preferred embodiments cannot limit the protection scope of the present disclosure. Based on the preferred embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work should still fall within the protection scope of the present disclosure.

[0037] It should be noted that in the description of the present disclosure, the terms "center", "upper", "lower", "top", "bottom", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are merely for the convenience of description and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0038] In addition, it should be noted that in the description of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0039] like Figure 1-6 As shown, in a preferred embodiment of the present disclosure, a pipe joint assembly for multi-parameter measurement of a fluid includes a four-way pipe joint 1, a composite sensor 2, a first sealing plug 3, a second sealing plug 4 and a sealing structure 5. The composite sensor 2 is arranged in the four-way pipe joint 1, and is used to detect the temperature, pressure, pulsation and flow rate of the liquid in the four-way pipe joint 1. The first sealing plug 3, the second sealing plug 4 and the sealing structure 5 jointly fix the composite sensor 2 to the four-way pipe joint 1 in a sealed form, and have a certain shock absorption and anti-vibration effect.

[0040] Continue reading Figure 1The four-way pipe joint 1 comprises a first joint 11 and a second joint 12 aligned with each other, and a third joint 13 and a fourth joint 14 aligned with each other. The first joint 11 and the second joint 12 are blocked by the first sealing plug 3, the second sealing plug 4 and the sealing structure 5 and are thus completely closed, and the third joint 13 and the fourth joint 14 are used to connect pipelines and pass liquids.

[0041] like Figure 1 and Figure 2 As shown, the composite sensor 2 includes a housing 201, a fiber Bragg grating temperature sensor 202, a fiber Bragg grating temperature pressure sensor 203, a first fiber Bragg grating pressure pulsation sensor 204, a second fiber Bragg grating pressure pulsation sensor 205, a first fiber Bragg grating flow velocity sensor 206, a second fiber Bragg grating flow velocity sensor 207, an elastic sheet 208, an elastomer 209, a heat conductive sheet 210, a heat conductive wire 211, a first fixing plate 212, a second fixing plate 213, a first optical fiber group 214, a second optical fiber group 215, a first connector 216 and a second connector 217.

[0042] like Figure 1 As shown, one end of the housing 201 is embedded in the first joint 11 and fixedly connected to the first joint 11 through the sealing structure 5, and the other end of the housing 201 is embedded in the second joint 12 and fixedly connected to the second joint 12 through the sealing structure 5, so that the housing 201 is fixed to the cross-way pipe joint 1. It can be understood by those skilled in the art that, in the case where the sealing structure 5 can fix the housing 201 to the cross-way pipe joint 1 in a sealed form, the sealing structure 5 can be any feasible structure, such as a material such as rubber or plastic, or a composite material of rubber or plastic with metal protection, or a split or semi-split structure used for installation and sealing.

[0043] Continue reading Figure 1 , the specific principle of the sealing structure is described. The sealing structure 5 is connected to the ends of the first joint 11 and the second joint 12 respectively, and the first sealing plug 3 and the second sealing plug 4 are respectively confined in the first joint 11 and the second joint 12, and can make the first sealing plug 3 and the second sealing plug 4 have a tendency to move towards each other to position the composite sensor 2.

[0044] Preferably, the first sealing plug 3 and the second sealing plug 4 may adopt a split structure, the split structure snaps and fixes the contact part of the optical cable and the housing 201, and the outer part of the split structure is tightly against the inner wall of the first joint 11 and the second joint 12 to form a seal for the first joint, the second joint and the optical cable;

[0045] Specifically, the sealing structure 5 includes a nut 501, one end of which is provided with a pressing cover plate 502, and the pressing cover plate 502 can press the sealing plug through an adjusting gasket 503, and the adjusting gasket 503 is arranged between the first sealing plug 3 and the second sealing plug 4 and the corresponding pressing cover plate 502, and can allow the optical cable to pass through, and the adjusting gasket 503 is set as an elastic sealing material, which plays an auxiliary sealing role after being deformed by pressure to prevent liquid leakage from the first joint 11 and the second joint 12; the pressing cover plate 502 is provided with a through hole 50 21. The diameter of the through hole 5021 is larger than the diameter of the composite sensor 2, so as to ensure that the composite sensor 2 can pass through smoothly. The nut 501 is threadedly connected to the first joint 11 and the second joint 12, and a groove 5011 is provided at the connection between the first joint 11 and the second joint 12 and the nut 501. A stop gasket 504 is provided between the nut 501 and the first joint 11 and the second joint 12, and the inner stop portion of the stop gasket 504 can be bent and fitted into the groove 5011 to prevent the stop gasket 504 from rotating.

[0046] Continue reading Figure 1 A support gasket 505 is provided between the first sealing plug 3 and the second sealing plug 4 and their corresponding pressing cover plate 502. The support gasket 505 can abut against the end surface of the first sealing plug 3 and the second sealing plug 4 or the adjustment gasket 503 under the push of the pressing cover plate 502 to support the relative position of the first sealing plug 3 and the second sealing plug 4, and indirectly locate the position of the composite sensor 2. Figure 6 It should be noted that the support gasket 505 is provided with a groove 5051 for allowing the optical cable to pass through. The groove is open along the side of the support gasket 505 to facilitate the optical cable to be inserted from the side of the support gasket 505, and the size of the groove 5051 can also be larger than the outer diameter of the optical cable and smaller than the size of the connector and the composite sensor at the end of the optical cable.

[0047] Continue reading Figure 1 The composite sensor 2 also includes a positioning member 219, which is arranged on the surface of the shell 201, and the positioning member 219 is located at both ends of the shell 201, and can be connected to the first sealing plug 3 and the second sealing plug 4 to limit the rotation of the shell 201 relative to the first sealing plug 3 or the second sealing plug 4.

[0048] Further, the positioning member 219 is configured as a positioning claw structure. At least two positioning claws are provided at the same end of the housing 201 and are evenly and symmetrically arranged along the outer surface of the housing 201 .

[0049] Continue reading Figure 1 The first sealing plug 3 and the second sealing plug 4 are respectively provided with a support frame 506, and the support frame 506 can increase the support strength of the first sealing plug 3 and the second sealing plug 4, so that the elastic deformation of the first sealing plug 3 and the second sealing plug 4 is controlled within a limited range.

[0050] It is worth mentioning that after the first joint 11 and the second joint 12 are matched with the third joint 13 and the fourth joint 14, the first sealing plug 3 in the first joint 11 or the second sealing plug 4 in the second joint 12 and the positioning member 219 are connected and positioned to ensure that the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 on the composite sensor 2 correspond to the third joint 13 and the fourth joint 14 respectively or correspond to the fourth joint 14 and the third joint 13 respectively, so that the first fiber grating flow velocity sensor 206 or the second fiber grating flow velocity sensor 207 is directly facing the incoming flow direction or the outgoing flow direction of the liquid; at the same time, it is ensured that the fiber grating temperature and pressure sensor 203 is arranged on the housing 201, specifically, it is arranged on the outside of the second housing 2012 and the first housing 2011, perpendicular to the liquid flow direction or the pipe wall; it is ensured that the first fiber grating pressure pulsation sensor 204 is arranged on the housing 201, specifically, it is arranged on the outside of the first housing 2011, perpendicular to the liquid flow direction or the pipe wall; in this way, the composite sensor 2 is accurately positioned in the four-way pipe joint 1.

[0051] It is worth mentioning that the third joint 13 and the fourth joint 14 are connected and positioned to form a transmission pipeline part that allows fluid to pass through. Specifically, the connection part between the third joint 13 and the fourth joint 14 and the outside world can be a flange or a threaded structure, which is convenient for assembly, disassembly and maintenance in different occasions.

[0052] like Figure 2 As shown, the fiber Bragg grating temperature sensor 202 is arranged inside the housing 201, and can detect the temperature of the liquid in the four-way pipe joint 1. Those skilled in the art can understand that by arranging the fiber Bragg grating temperature sensor 202 inside the housing 201, it is possible to avoid the pressure of the external liquid from affecting the detection result of the fiber Bragg grating temperature sensor 202, thereby ensuring the detection accuracy of the fiber Bragg grating temperature sensor 202.

[0053] Continue reading Figure 2 The fiber Bragg grating temperature and pressure sensor 203 is arranged on the housing 201 (specifically, it is arranged on the outside of the housing 201; perpendicular to the liquid flow direction or the pipe wall), and can detect the temperature and pressure of the liquid in the four-way pipe joint 1. Then, by comparing the data detected by the fiber Bragg grating temperature and pressure sensor 203 and the fiber Bragg grating temperature sensor 202, the pressure of the liquid in the four-way pipe joint 1 can be obtained according to the pure temperature value detected by the fiber Bragg grating temperature sensor 202 and the pre-calibrated comparison data corresponding to the fiber Bragg grating temperature and pressure sensor 203. The problem of cross-sensitivity of fiber Bragg grating sensors to pressure and temperature in the prior art, and the problem that the pressure detection range is affected by linear calibration and the pressure range is limited. Continue to refer to Figure 2The first fiber Bragg grating pressure pulsation sensor 204 and the second fiber Bragg grating pressure pulsation sensor 205 are arranged on the housing 201 and can detect the pulsation of the liquid in the four-way pipe joint 1.

[0054] like Figure 1 As shown, the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 are both arranged on the housing 201 (specifically, they are arranged on both sides of the outside of the housing 201, parallel to the flow velocity direction or pipeline), and the first fiber grating flow velocity sensor 206 is aligned with the third joint 13, and the second fiber grating flow velocity sensor 207 is aligned with the fourth joint 14, or the first fiber grating flow velocity sensor 206 is aligned with the fourth joint 14, and the second fiber grating flow velocity sensor 207 is aligned with the third joint 13. It can be understood by those skilled in the art that by comparing the difference between the data detected by the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207, the flow velocity and flow direction or the change in flow velocity of the liquid in the four-way pipe joint 1 can be determined. Then, the flow rate of the liquid in the four-way pipe joint 1 can be calculated according to the product of the flow velocity and the cross-sectional area of ​​the gap between the four-way pipe joint 1 and the composite sensor 2. Since the flow rate can be calculated by those skilled in the art based on the common knowledge in the art, it will not be described in detail here. Those skilled in the art can also understand that, in a hydrostatic system, according to the Bernoulli equation, by ignoring the effect of potential energy and local pressure loss, the flowing liquid forms a pressure difference before and after the object flowing around, and the pressure difference can accurately reflect the flow velocity and direction of the liquid at that location. Therefore, when the flowing liquid passes through the body (composite sensor), a pressure difference will be generated before and after the body, and then by detecting the pressure difference, the flow velocity and direction can be determined.

[0055] Continue reading Figure 1, the first optical fiber group 214 passes through the first connector 11, the first sealing plug 3 and the sealing structure 5 after being armored (a protective layer is provided on the outer side of the first optical fiber group 214), and is sealed and connected with the first sealing plug 3 and the sealing structure 5. In other words, the first optical fiber group 214 is sealed and connected with the first connector 11 through the first sealing plug 3 and the sealing structure 5. Further, one end of the first optical fiber group 214 is connected to the first connector 216 so as to be connected to the external optical cable through the first connector 216; the other end of the first optical fiber group 214 is respectively connected to one end of the aforementioned six fiber grating sensors. Specifically, the first optical fiber group 214 includes six optical fibers, each of which is a carrier of a fiber grating sensor. In other words, the fiber grating sensor is made by recording gratings on optical fibers, and the grating characteristic values ​​of the six fiber grating sensors in a composite sensor are the same (same core diameter, same material, same specification, same grating recording depth, same grating period, same grating length), so that when using wavelength division multiplexing technology, the location of the data source obtained by the demodulation device can be determined because the characteristic values ​​of each fiber grating in the same composite sensor are the same. Since wavelength division multiplexing technology is a technology well known to those skilled in the art, it will not be described in detail here.

[0056] Continue reading Figure 1 , the second optical fiber group 215 passes through the second joint 12, the second sealing plug 4 and the sealing structure 5 after being armored, and is sealed and connected with the second sealing plug 4 and the sealing structure 5. In other words, the second optical fiber group 215 is sealed and connected with the second joint 12 through the second sealing plug 4 and the sealing structure 5. Further, one end of the second optical fiber group 215 is connected with the second connector 217 so as to be connected to the external optical cable through the second connector 217; the other end of the second optical fiber group 215 is respectively connected with the other ends of the aforementioned six fiber grating sensors. Specifically, the second optical fiber group 215 includes six optical fibers, each of which is an extension of the aforementioned optical fiber and belongs to the other end of the corresponding fiber grating sensor.

[0057] It should be noted that the terms "first fiber group 214" and "second fiber group 215" and the description of the connection relationship between the two and each fiber Bragg grating sensor in the foregoing text are only for the convenience of description and for those skilled in the art to understand the technical solution. In actual use, the "first fiber group 214" and the "second fiber group 215" are actually the same fiber group. In other words, the fiber group consisting of 6 optical fibers runs through the housing 201, and each optical fiber is engraved with a grating at a specific portion in the housing 201, thereby forming a fiber Bragg grating temperature sensor 202, a fiber Bragg grating temperature pressure sensor 203, a first fiber Bragg grating pressure pulsation sensor 204, a second fiber Bragg grating pressure pulsation sensor 205, a first fiber Bragg grating flow rate sensor 206, and a second fiber Bragg grating flow rate sensor 207.

[0058] Refer to the following Figures 2 to 5 , to describe the specific structure of the composite sensor 2 in detail.

[0059] like Figure 2 , Figure 4 and Figure 5 As shown, the shell 201 is an ellipsoidal spherical structure as a whole, so as to reduce the resistance to the liquid flowing through it. In addition, those skilled in the art can also set the shell 201 to any other feasible structure with a streamlined appearance, such as an olive shape, a fish shape, etc. as needed. Further, the shell 201 includes a first shell 2011, a second shell 2012 and a connecting cover 2013. The first shell 2011 and the second shell 2012 can be detachably connected to the connecting cover 2013 respectively, and in the assembled state, the connecting cover 2013 can seal the first shell 2011 and the second shell 2012, so that a closed space can be formed between the first shell 2011 and the connecting cover 2013, and a closed space can also be formed between the second shell 2012 and the connecting cover 2013.

[0060] Although not shown in the figure, in the preferred embodiment of the present disclosure, the first housing 2011, the second housing 2012 and the connection cover 2013 are all made of titanium alloy or aluminum alloy by stamping, or those skilled in the art can also make at least one of the first housing 2011, the second housing 2012 and the connection cover 2013 made of titanium alloy or aluminum alloy by stamping as needed. Furthermore, the first housing 2011 is also provided with a through hole for installing the elastic sheet 208.

[0061] like Figure 4 and Figure 5 As shown, the elastic sheet 208 is embedded in the through hole on the first shell 2011, and the circumferential edge of the elastic sheet 208 is sealed and connected to the side wall of the through hole, or the elastic sheet 208 is sealed and connected to the first shell 2011, and the through hole is closed. The first fiber grating pressure pulsation sensor 204 is fixedly connected to the outside of the elastic sheet 208, and the second fiber grating pressure pulsation sensor 205 is fixedly connected to the inside of the elastic sheet 208, and the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 are symmetrically arranged relative to the elastic sheet 208, so that the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 can produce deformations with equal strain values ​​but opposite directions as the elastic sheet 208 is deformed.

[0062] Furthermore, the elastic sheet 208 has good thermal conductivity, such as thermally conductive silicone sheet, graphene diaphragm, etc. The specific technical means of detecting the liquid pressure by the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 can be referred to by those skilled in the art for the relevant principles on page 2155 of the Journal of Scientific Instruments (Volume 39, Issue 9) published in September 2013. It can be known that the reverse deformation difference subtraction principle can effectively eliminate the influence of temperature on strain in the cross-sensitivity problem of temperature and strain of the fiber grating sensor. Then on this basis, the measured value of pressure strain can be obtained. By using the diaphragm to directly contact the working medium, the variation of the measured value of pressure strain can be obtained, so that the fluctuation of environmental pressure can be measured in time. The variation of the pressure measurement value in unit time can be easily obtained according to the existing computer processing technology, so no more explanation will be given here.

[0063] Continue reading Figure 4 and Figure 5 The airbag 2091 is arranged in the first shell 2011, and the elastic material 2092 is filled between the airbag 2091, the first shell 2011 and the connection cover 2013, so as to encapsulate the airbag 2091 in the elastic material 2092 to form the elastic body 209. The elastic sheet 208 does not contact the airbag 2091 or the elastic material 2092, so that a cavity 218 is formed between the elastic sheet 208 and the elastic body 209, and the cavity 218 is filled with hydrogen or helium at a pressure of 0.1 MPa, and it is ensured that the elastic sheet 208 does not touch the elastic body 209 when the maximum deformation occurs. It should be further explained that the hydrogen or helium filled in the cavity can play a certain back pressure role, which can prevent the elastic sheet 208 from being dented at standard atmospheric pressure. At the same time, the hydrogen or helium filled in the cavity can play a certain heat conduction and damping role. When the liquid temperature or pressure in the pipeline is disturbed, it can avoid thermal cracking caused by inconsistent shrinkage rates between the elastic sheet 208 and the first shell 2011 or vibration of the elastic sheet 208.

[0064] Furthermore, those skilled in the art may also, as required, provide the elastic material 2092 provided between the airbag 2091 and the housing 201 as an elastic filler, which includes materials such as rubber or resin. A skin may also be provided on the outside of the housing 201, the skin being encapsulated on the outside of the housing 201 and the optical fiber, and the skin being compatible with the liquid in the pipeline (the skin and the liquid do not chemically react).

[0065] Continue reading Figure 4 and Figure 5, the first fixing plate 212 and the second fixing plate 213 are fixed to the second shell 2012 respectively. Specifically, the first fixing plate 212 is fixedly connected to the second shell 2012 by welding or thermal bonding or by a first fixing column (not shown in the figure) (for example, welding or thermal bonding), and the second fixing plate 213 is fixedly connected to the first fixing plate 212 by welding or thermal bonding or by a second fixing column (not shown in the figure) (for example, welding or thermal bonding). One end of the heat conductive sheet 210 is fixedly connected to the first fixing plate 212; the other end of the heat conductive sheet 210 is relatively movably connected to the second fixing plate 213. Specifically, the second fixing plate 213 is provided with a through hole (not shown in the figure) that allows the heat conductive sheet 210 to pass through, and the other end of the heat conductive sheet 210 is inserted into the through hole so that the heat conductive sheet 210 can be deformed freely when heated. Preferably, the heat conducting sheet 210 is an aluminum sheet that can play a role in temperature measurement and sensitivity enhancement, and the aluminum sheet is a longitudinal strip in the shape of an arc tile, and the fiber Bragg grating temperature sensor 202 is closely attached to the middle of the longitudinal axis of the arc tile-shaped aluminum sheet. Of course, those skilled in the art can also set the heat conducting sheet 210 to any other structure as needed, such as a flat plate, cylinder, or other structure made of materials such as copper sheet and zinc sheet.

[0066] The heat-conducting wire 211 passes through the side wall of the second housing 2012 (or passes through the gap between the connecting cover 2013 and the second housing 2012 to communicate with the outside), and one end is fixedly connected to the heat-conducting sheet 210, and the other end extends to the outside of the second housing 2012, so as to transfer the heat of the liquid in the four-way pipe joint 1 to the heat-conducting sheet 210, and then be detected by the fiber grating temperature sensor 202 fixed to the heat-conducting sheet 210. Among them, the fiber grating temperature sensor 202 can be longitudinally deformed with the longitudinal deformation of the heat-conducting sheet 210, so that the fiber grating temperature sensor 202 can increase the longitudinal deformation of the grating as the heat-conducting sheet 210 is heated and elongated, so that the heat-conducting sheet 210 plays a role in enhancing the sensitivity of the fiber grating temperature sensor 202, so as to improve the measurement sensitivity of the fiber grating temperature sensor 202. At the same time, since only one end of the heat conductive sheet 210 (which serves as a temperature grating sensitivity enhancement component) is fixed during longitudinal deformation and the other end can move freely, the interference of the inherent thermal stress deformation caused by the thermal expansion and contraction of the heat conductive sheet 210 on the longitudinal signal of the fiber Bragg grating temperature sensor 202 is overcome, thereby improving the detection accuracy of the fiber Bragg grating temperature sensor 202.

[0067] In addition, those skilled in the art may also, as needed, fix one end of the heat conductive wire 211 located inside the second shell 2012 to the first fixing plate 212 so that the heat conductive wire 211 first transfers the heat in the external environment to the first fixing plate 212, and then the first fixing plate 212 transfers the heat to the heat conductive sheet 210.

[0068] Although not shown in the figure, the second housing 2012 is also filled with heat-conducting silicone oil, and the volume of the heat-conducting silicone oil is between 1 / 2 and 4 / 5 of the volume of the space in the second housing 2012, so that the heat-conducting silicone oil can also reliably transfer the heat of the liquid in the four-way pipe joint 1 to the heat-conducting sheet 210, and ensure that the expansion of excessive heat-conducting silicone oil or the conduction of external pressure will not cause additional compressive strain on the grating in the fiber Bragg grating temperature sensor 202. It can be understood by those skilled in the art that the heat-conducting silicone oil submerging the heat-conducting sheet 210 enhances the uniformity of the heat received by the heat-conducting sheet 210 and the rapidity of heat conduction between the heat-conducting sheet 210 and the housing 201.

[0069] Continue reading Figure 4 and Figure 5 The fiber Bragg grating temperature and pressure sensor 203 is fixedly mounted to the outer side of the side wall of the second shell 2012 (preferably, placed directly below the elastic sheet 208 symmetrically and perpendicular to the direction of the fluid flow rate, to ensure that the pressure and pressure fluctuation detection values ​​can be referenced to each other and are not affected by the fluid dynamic pressure), and the first fiber Bragg grating flow rate sensor 206 and the second fiber Bragg grating flow rate sensor 207 are symmetrically arranged on the circumferential surface of the connecting cover 2013 relative to the long axis of the shell 201 (preferably, the plane where the first fiber Bragg grating flow rate sensor 206 and the second fiber Bragg grating flow rate sensor 207 are located is parallel to the direction of the fluid flow rate).

[0070] Although not explicitly shown in the figure, the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 are fiber grating sensors with the same parameters, so that when the external environment (pressure or temperature) is the same, the data detected by the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 can be subtracted from each other, and the subtraction value can correspond to the flow velocity of the fluid. At the same time, the flow direction can also be measured based on the positive and negative relationship of the subtraction value; at the same time, the fluctuation of the flow velocity can also be measured based on the change of the subtraction value over time.

[0071] Combine the following Figure 1 , Figure 4 and Figure 5 , to briefly explain the working principle of composite sensor 2.

[0072] When flowing liquid is passed into the four-way pipe joint 1, the heat-conducting wire 211 can transfer the heat of the liquid to the heat-conducting sheet 210, so that the fiber Bragg grating temperature sensor 202 attached to the heat-conducting sheet 210 can increase the longitudinal deformation of the grating as the heat-conducting sheet 210 is heated and elongated, so that the heat-conducting sheet 210 plays a role in enhancing the sensitivity of the fiber Bragg grating temperature sensor 202, so that the fiber Bragg grating temperature sensor 202 obtains the temperature value and the temperature sensitivity accuracy. Specifically, the precise temperature of the liquid in the four-way pipe joint 1 is obtained by calculating the light wave changes caused by the fiber Bragg grating temperature sensor 202 at this time. The cross-influence of the environmental pressure outside the shell on the detection result of the fiber Bragg grating temperature sensor 202 is avoided.

[0073] At the same time, the changes in the temperature and pressure of the liquid in the four-way pipe joint 1 will also cause the deformation of the fiber Bragg grating temperature and pressure sensor 203, and then the comprehensive data of the temperature or pressure of the liquid in the four-way pipe joint 1 can be obtained according to the changes in the light wave related parameters caused by the fiber Bragg grating temperature and pressure sensor 203 at this time (for example: the characteristic wavelength center offset of the grating transmitted light or reflected light, or the change of the Stokes parameter). Then, by comparing the data detected by the fiber Bragg grating temperature and pressure sensor 203 and the fiber Bragg grating temperature sensor 202, the pressure of the liquid in the four-way pipe joint 1 is obtained according to the corresponding data group pre-stored during calibration. This avoids the cross-influence of the temperature of the liquid when the pressure of the liquid is measured by the fiber Bragg grating pressure sensor alone using the grating center wavelength drift in the prior art, which leads to the difficulty of extracting the pressure detection value.

[0074] At the same time, since the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 are simultaneously in the environment where the liquid pressure and temperature act together in the four-way pipe joint 1, and their grating characteristic values ​​are the same, at this time, the difference in the change of the characteristic light wave signal caused by the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207 is not affected by the external environmental pressure or temperature. Therefore, the flow velocity of the liquid in the four-way pipe joint 1 is calculated based on the difference in the comprehensive data (including the values ​​of the pressure and temperature signals) of the characteristic light signal detected by the first fiber grating flow velocity sensor 206 and the second fiber grating flow velocity sensor 207. The auxiliary computer system can calculate the flow velocity fluctuation based on the change of the flow velocity over time, and the flow direction of the liquid can be determined based on the positive and negative relationship of the difference subtraction data.

[0075] At the same time, the liquid flowing in the four-way pipe joint 1 may pulsate (pressure changes all the time), and thus cause the elastic sheet 208 to deform periodically, thereby forcing the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 to deform periodically, and then according to the periodic changes of the characteristic light wave signal caused by the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 at this time, the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 detect the real-time pressure pulsation changes of the liquid. It can be understood by those skilled in the art that the first fiber grating pressure pulsation sensor 204 and the second fiber grating pressure pulsation sensor 205 disposed on both sides of the elastic sheet 208 can also eliminate the cross-effect of temperature on pressure detection. Specifically, the elastic sheet 208 can play a role in heat conduction, so the difference between the values ​​detected by the first fiber Bragg grating pressure pulsation sensor 204 and the second fiber Bragg grating pressure pulsation sensor 205 is the liquid pressure value outside the housing 201 (for details, please refer to the relevant principles on page 2155 of the Journal of Scientific Instruments (Volume 39, Issue 9) published in September 2013. It can be seen that this reverse deformation subtraction principle can effectively eliminate the cross-sensitivity problem of fiber Bragg grating sensors regarding temperature and strain, and thus obtain a pressure measurement value that is not affected by temperature.). Then, on this basis, the principle that the diaphragm directly (or indirectly through the epidermis) contacts the working medium and can timely measure the fluctuation of the ambient pressure measurement value can be determined to be the pressure pulsation.

[0076] Of course, those skilled in the art may also accurately detect the fluctuation of external liquid pressure directly through the change in the difference between the data detected by the first fiber grating pressure pulsation sensor 204 and the data detected by the second fiber grating pressure pulsation sensor 205 as needed.

[0077] In addition, in actual use, those skilled in the art can also connect multiple composite sensors 2 in series for use as needed, so that each composite sensor 2 detects parameters at multiple positions in the liquid pipeline. It should be noted that in order to prevent the measurement data of the multiple composite sensors 2 connected in series from affecting each other, the characteristic values ​​of the gratings between the multiple composite sensors 2 need to be set to be different. Specifically, the characteristic values ​​of the gratings between the multiple fiber grating sensors connected in series are set to be different, so that each composite sensor in the multiple fiber grating sensors connected in series corresponds to a different characteristic grating, and each composite sensor connected in series corresponds to each sensor (fiber grating temperature sensor, fiber grating temperature pressure sensor, fiber grating pressure pulsation sensor, first fiber grating flow velocity sensor and second fiber grating flow velocity sensor), specifically, the fiber grating temperature sensor is connected in series with the fiber grating temperature sensor, the fiber grating temperature pressure sensor is connected in series with the fiber grating temperature pressure sensor, the fiber grating pressure pulsation sensor is connected in series with the fiber grating pressure pulsation sensor (the outer side of the elastic sheet corresponds to the outer side, and the inner side corresponds to the inner side), the first fiber grating flow velocity sensor is connected in series with the first fiber grating flow velocity sensor, and the second fiber grating flow velocity sensor is connected in series with the second fiber grating flow velocity sensor, so as to facilitate the checking. Further, in order to facilitate the collection of data, those skilled in the art can also make the characteristic values ​​of the gratings of the multiple fiber grating sensors on each composite sensor 2 the same as needed.

[0078] So far, the technical solutions of the present disclosure have been described in combination with the above multiple embodiments, but it is easy for those skilled in the art to understand that the protection scope of the present disclosure is not limited to these specific embodiments. Without departing from the technical principles of the present disclosure, those skilled in the art can split and combine the technical solutions in the above-mentioned various embodiments, and can also make equivalent changes or replacements to the relevant technical features. Any changes, equivalent replacements, improvements, etc. made within the technical concept and / or technical principle of the present disclosure will fall within the protection scope of the present disclosure.

Claims

1. A pipe joint assembly for multi-parameter measurement of fluid, characterized in that: The pipe joint assembly for fluid multi-parameter measurement comprises a four-way pipe joint and a composite sensor arranged in the four-way pipe joint. The four-way pipe joint includes a first joint and a second joint for fixing the composite sensor and the optical cable, and a third joint and a fourth joint for transmitting pipeline liquid; The composite sensor comprises a housing, a fiber Bragg grating temperature sensor, a fiber Bragg grating temperature pressure sensor, a fiber Bragg grating pressure pulsation sensor, a first fiber Bragg grating flow velocity sensor, a second fiber Bragg grating flow velocity sensor, and an optical cable composed of a plurality of optical fibers: One end of the shell is embedded in the first joint and fixedly connected to the first joint, and the other end of the shell is embedded in the second joint and fixedly connected to the second joint; Each of the optical fibers in the optical cable composed of multiple optical fibers is engraved with a grating, thereby forming the fiber grating temperature sensor, the fiber grating temperature pressure sensor or the fiber grating pressure pulsation sensor, the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor; The optical cables at both ends of the housing penetrate the sealing structures of the first connector and the second connector; The fiber grating temperature sensor is arranged inside the housing and is capable of detecting the temperature of the liquid in the four-way pipe joint; The fiber grating temperature and pressure sensor is arranged on the housing and is capable of detecting comprehensive data of the temperature and pressure of the liquid in the four-way pipe joint; The fiber grating pressure pulsation sensor is arranged on the housing and is capable of detecting the pressure fluctuation of the liquid in the four-way pipe joint; The pipe joint assembly for fluid multi-parameter measurement also includes a first sealing plug arranged at the first joint and a second sealing plug arranged at the second joint; The sealing structure comprises a nut, one end of which is provided with a pressing cover plate, the pressing cover plate can press the sealing plug through an adjusting gasket, the adjusting gasket is arranged between the first sealing plug and the second sealing plug and the corresponding pressing cover plates, and can allow the optical cable to pass through, the adjusting gasket is made of elastic sealing material, and plays an auxiliary sealing role after being deformed by pressure, so as to prevent liquid leakage from occurring in the first joint and the second joint; The pressing cover plate is provided with a through hole, the diameter of which is larger than the diameter of the composite sensor, so as to ensure that the composite sensor can pass through smoothly; The nut is threadedly connected to the first joint and the second joint, and a groove is provided at the connection between the first joint and the second joint and the nut, and a stop washer is provided between the nut and the first joint and the second joint, and the inner stop portion of the stop washer can be bent and fitted into the groove to prevent the stop washer from rotating; The shell is provided with a through hole; The composite sensor further comprises an elastic sheet disposed at the through hole, the elastic sheet being sealingly connected to the housing and thus closing the through hole; The fiber Bragg grating pressure pulsation sensor comprises a first fiber Bragg grating pressure pulsation sensor fixed to the outside of the elastic sheet and a second fiber Bragg grating pressure pulsation sensor fixed to the inside of the elastic sheet, so as to detect the pressure fluctuation by the fluctuation of the difference between the data detected by the first fiber Bragg grating pressure pulsation sensor and the data detected by the second fiber Bragg grating pressure pulsation sensor; The housing comprises a first housing, a second housing and a connection cover, wherein the first housing is located at one side of the connection cover and is fixedly connected to the connection cover, and the second housing is located at the other side of the connection cover and is fixedly connected to the connection cover; The composite sensor further comprises an airbag disposed in the first shell, and an elastic material is filled between the airbag and the shell and between the airbag and the connection cover, so as to encapsulate the airbag in the elastic material to form an elastic body; The elastic sheet does not contact the airbag or the elastic material, so that a cavity is formed between the airbag or the elastic material and the connecting cover, and the cavity is filled with hydrogen or helium at a pressure of 0.1 MPa to ensure that the elastic sheet has a certain back pressure on the outside; the spacing of the cavity is used to ensure that the elastic sheet does not touch the elastomer when it is deformed to the maximum.

2. A pipe joint assembly for fluid multi-parameter measurement according to claim 1, characterized in that: The first sealing plug and the second sealing plug respectively allow the optical cable to pass through, thereby forming a seal for the first joint, the second joint and the optical cable; The sealing structure is connected to the ends of the first joint and the second joint respectively, restricting the first sealing plug and the second sealing plug in the first joint and the second joint respectively, and enabling the first sealing plug and the second sealing plug to move towards each other to position the composite sensor.

3. A pipe joint assembly for fluid multi-parameter measurement according to claim 1, characterized in that: A supporting gasket is provided between the first sealing plug and the second sealing plug and their corresponding clamping cover plate. The supporting gasket can abut against the end faces of the first sealing plug and the second sealing plug or the adjusting gasket under the push of the clamping cover plate to support the relative position of the first sealing plug and the second sealing plug and indirectly locate the position of the composite sensor.

4. A pipe joint assembly for fluid multi-parameter measurement according to claim 1 or 3, characterized in that: The composite sensor also includes a positioning member, which is arranged on the surface of the shell and located at both ends of the shell, and can be connected to the first sealing plug and the second sealing plug to limit the rotation of the shell relative to the first sealing plug or the second sealing plug.

5. A pipe joint assembly for fluid multi-parameter measurement according to claim 4, characterized in that: The positioning member is configured as a positioning claw structure, and at least two positioning claws are provided at the same end of the shell and are evenly and symmetrically arranged along the outer surface of the shell.

6. A pipe joint assembly for fluid multi-parameter measurement according to claim 5, characterized in that: The first sealing plug and the second sealing plug are respectively provided with support frames inside, and the support frames can increase the support strength of the first sealing plug and the second sealing plug, so that the elastic deformation of the first sealing plug and the second sealing plug is controlled within a limited range.

7. A pipe joint assembly for fluid multi-parameter measurement according to claim 1, characterized in that: The composite sensor further comprises heat-conducting silicone oil filled in the second housing, wherein the heat-conducting silicone oil immerses the fiber Bragg grating temperature sensor so as to enhance the temperature consistency between the housing and the fiber Bragg grating temperature sensor; The composite sensor further comprises a first fiber Bragg grating flow velocity sensor and a second fiber Bragg grating flow velocity sensor, wherein the first fiber Bragg grating flow velocity sensor and the second fiber Bragg grating flow velocity sensor are symmetrically arranged on the outer side of the housing along the axis of the housing, so as to detect the flow velocity and flow direction or the change amount of the flow velocity of the liquid in the environment where the composite sensor is located by the difference between the data detected by the first fiber Bragg grating flow velocity sensor and the data detected by the second fiber Bragg grating flow velocity sensor; The first fiber grating flow velocity sensor is aligned with the third joint, and the second fiber grating flow velocity sensor is aligned with the fourth joint, or the first fiber grating flow velocity sensor is aligned with the fourth joint, and the second fiber grating flow velocity sensor is aligned with the third joint, and the first fiber grating flow velocity sensor and the second fiber grating flow velocity sensor are symmetrically arranged on the outside of the shell along the axis of the shell, so as to detect the flow velocity of the liquid in the four-way pipe joint by the difference between the data detected by the first fiber grating flow velocity sensor and the data detected by the second fiber grating flow velocity sensor.

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