CN109839211B - Distributed optical fiber water body temperature and flow velocity distribution measuring device - Google Patents
Distributed optical fiber water body temperature and flow velocity distribution measuring device Download PDFInfo
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- CN109839211B CN109839211B CN201910265772.0A CN201910265772A CN109839211B CN 109839211 B CN109839211 B CN 109839211B CN 201910265772 A CN201910265772 A CN 201910265772A CN 109839211 B CN109839211 B CN 109839211B
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Abstract
The invention discloses a measuring device for distributed optical fiber water body temperature and flow velocity distribution, which relates to the fluid structure design and the distributed optical fiber sensing measuring technology, and aims at the problem of measurement of the existing water body environment, the following scheme is provided, wherein the measuring device comprises a carrier, a rotating fulcrum shaft is connected in the carrier, one end of the rotating fulcrum shaft is connected with a base, a temperature measuring device and a flow velocity measuring device are arranged on the carrier, and an optical fiber hollow winding structure is arranged in the carrier; the surface Teflon coating mode of the carrier structure can effectively reduce the adhesion and radiation of various substances in the water body and prolong the test effectiveness of the device.
Description
Technical Field
The invention relates to a fluid structure design and distributed optical fiber sensing measurement technology, in particular to a distributed optical fiber water body temperature and flow velocity distribution measuring device.
Background
Since the development of the laser technology and the optical fiber technology, the optical fiber is used as a transmission medium and can also be used as a sensing medium characteristic, the developed optical fiber sensing technology can take the wave transmitted in the optical fiber as a carrier, the state of the environment where the optical fiber is located and the optical wave or effect change are related, physical parameters including temperature, strain and the like can influence the refractive index, deformation and the like of the optical fiber, the effect caused by the transmitted optical signal or optical signal changes, and the sensing and the reduction of the related information of the external environment can be realized through the demodulation and analysis of the parameters such as the intensity, the phase, the frequency, the polarization state and the like.
The application of the flow line structure in the physical test of the fluid is very wide, the influence of the structure distribution on the physical quantity of the flow field can be reduced, and the flow line structure is widely applied to the design of the environments such as gas, liquid and the like.
In actual water body test application, physical parameters of different water body layers need to be examined, but the complex water body environment greatly limits the application of optical fiber sensing; meanwhile, under the combined action of multiple physical parameters, the test precision is also reduced to some extent, and the further expansion and application of the technology are influenced.
Disclosure of Invention
The distributed optical fiber water body temperature and flow velocity distribution measuring device provided by the invention solves the problem of influence of a water body environment on measurement.
In order to achieve the purpose, the invention adopts the following technical scheme:
1. temperature change and stress optical fiber measurement scheme:
brillouin scattering results from the interaction of photons with acoustic phonons, and this scattered light is very sensitive to temperature and strain. When a narrow linewidth laser light source is used, stimulated brillouin scattering is easily caused, and such scattering causes sharp attenuation of incident light. The coupling mode equation between brillouin scattering and pump light can be expressed as:
in the formula, Is and Ip are respectively the intensity of Brillouin scattered light and the intensity of incident pump light, gBThe equation above shows that backscattered light has a frequency shift, which can be expressed as a function of temperature and strain:
vB(e，T)＝vB(0，T0)[1+Cse+CT(T-T0)]
in the formula T0Is the reference temperature. The Brillouin scattering sensor detects the frequency shift of scattered light, so a laser light source with a narrow line width is used in the Brillouin scattering sensor, the Brillouin frequency shift is resolved by a high-resolution coherent detection technology, and an expression of scattering power to temperature and strain sensitivity can be further obtained:
PB(e，T)＝PB(0，T0)[1+Dse+DT(T-T0)]
can change Deltav according to Brillouin frequency shiftBAnd power change Δ PBTemperature and strain information are obtained separately.
2. Measuring the temperature and the flow velocity of the water body and checking the double-parameter precision:
the temperature measurement of the water body can directly utilize the optical fiber to obtain temperature information, the flow rate parameter can be obtained by testing the strain quantity of the same optical fiber, and the flow rate and the strain have the following relations:
V＝AvB(e，T)
the parameter a is a constant associated with the mechanical transmission structure.
This value contains the temperature variation part in the actual measurement, so that the influence must be separated from the test data in the actual test. Because the same optical fiber of the same type is adopted, the temperature parameter can be simply and conveniently corrected, and the result can be corrected by combining the temperature test data as follows:
V＝A[vB(e，T)-vB(0，T)|
3. description of the apparatus:
the main features of the measuring device of the invention are described: the method comprises the steps that a test sensing optical fiber and a transmission optical fiber are different parts of the same optical fiber, the optical fiber is wound in a hollow structure of a carrier to be matched with optical fiber measurement space resolution, the distance between a flow velocity measurement point and a temperature measurement point is close to effectively compensate flow velocity measurement errors caused by temperature change, the temperature measurement is directly obtained through a winding optical fiber on a metal heat conductor, and the flow velocity measurement converts the flow velocity into pressure through a streamline blade and acts on multiple parts of the optical fiber in a tangential direction to obtain more accurate test data; the whole fluid carrier is distributed with a plurality of groups of measurement structures of the types according to different depths so as to realize the measurement of the temperature and the flow velocity of the water body with the resolution ratio of more than 25cm and different depths, and the group of measurement is realized by winding one optical fiber.
Preferably, the carrier is a hollow fusiform streamline structure, the hollow structure of the carrier enables the carrier to be suspended in water and to freely rotate around the support body, and the tail part of the carrier is provided with a blade type flow velocity measurement conduction structure.
Preferably, the hollow winding structure in the carrier is a smooth approximately elliptical cylinder, and the surface of the structure is provided with a plurality of optical fiber fixing devices.
Preferably, the temperature measuring device comprises a good heat conduction metal module, a surface grid structure and an optical fiber winding structure, optical fibers are divided into a plurality of groups and tightly wound on metal, the in-out windings of the optical fibers are positioned on the same plane, the metal is fixed at the tail part of the streamline carrier structure and is separated from the carrier by a poor heat conduction layer, the optical fiber winding structure comprises optical fiber windings, and the wound parts of the optical fibers are all smooth structures.
Preferably, the flow velocity measuring device comprises a streamline blade, a lever type force transmission structure, a limiting structure and a reset structure, the streamline blade is of a hollow structure and can be suspended in water, the size of the streamline blade is gradually increased along the water flow direction, and the front section of the streamline blade is a thin rod which is connected with the support shaft and forms the lever type force transmission structure.
Preferably, the lever type force transmission structure is a force application lever structure and is connected with the optical fiber tangential force application structure and the streamline blade, and the distance from the force application structure to the supporting shaft point is smaller than the distance from the blade to the supporting shaft point and is on the same side.
Preferably, the optical fiber tangential force application structure comprises a connecting rod connected with the lever, a T-shaped notch at the tail end of the connecting rod, and an optical fiber support body connected to the wall of the carrier, wherein the T-shaped notch and the support body are adjustable.
Preferably, the limit structure is attached to a connecting rod portion of the optical fiber tangential force application structure, and the reset structure includes an electromagnet fixed to the carrier and a soft magnet attached to the connecting rod portion.
Preferably, the main structural surface of the device adopts a Teflon coating, and the structural surface comprises a streamline structural carrier, blades and connecting rods.
Preferably, the device is provided with a base which is a solid bottom plate, the carrier is connected with the base through a fulcrum shaft and is connected with the fulcrum shaft through a positioning mechanism, and the length of the fulcrum shaft is adjustable through the positioning mechanism.
The invention has the beneficial effects that:
the invention has the beneficial effects that: the device can measure the temperature and the flow velocity of the water body, and the measurement precision is improved by obtaining the average measurement of multiple groups of parameters of a single point, namely, the stress change of the optical fiber caused by the same physical quantity is measured at multiple points in a certain section of optical fiber interval; the influence of the water body environment temperature on the flow velocity measurement is corrected through the temperature measurement value, namely, the temperature data is firstly tested, then the flow velocity data is obtained, and the temperature influence of the flow velocity data is corrected. The streamline carrier structure can be suspended in a water body, the maximum flow velocity value in the method can be selected automatically, and the test accuracy is improved; by adopting the vertical integrated multi-point measurement, the distribution of the flow velocity and the temperature of the water body in depth can be effectively obtained, and the measurement is completed by a single test optical fiber, so that the test efficiency is improved, and the test cost is reduced; the surface Teflon coating mode of the carrier structure can effectively reduce the adhesion and radiation of various substances in the water body and prolong the test effectiveness of the device.
Drawings
Fig. 1 is a schematic structural diagram of a device for measuring the temperature and the flow velocity of an optical fiber water body according to the present invention.
Fig. 2 is a schematic structural diagram of an embodiment of the present invention.
Fig. 3 is a schematic view of the interface for measuring temperature and flow rate of the optical fiber of fig. 1 and 2.
Fig. 4 is a schematic view of the temperature measurement structure in fig. 1 and 2.
Reference numbers in the figures: the device comprises a carrier 1, a rotating fulcrum 2, an optical fiber hollow winding structure 3, a flow rate measuring device 4, a temperature measuring device 5, a base 6, a supporting shaft 7, streamline blades 8, a connecting rod 9, an optical fiber support body 10, a T-shaped notch 11, an electromagnetic coil 12, soft magnets 13, metal with a grid structure 14 and optical fibers 15.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Referring to fig. 1-4, an example of the measuring device for realizing the temperature and flow velocity distribution of a water body by using a distributed optical fiber according to the present invention is shown in fig. 1-2, and the device can measure the temperature, the flow velocity and the distribution thereof in the depth direction of the water body. Whole measuring mechanism is attached to carrier 1 of hollow type fusiform streamlined structure, and carrier 1 is connected with base 6 through rotatory fulcrum 2, and base 6 stabilizes the water with whole measuring device, and the hollow structure of carrier 1 can suspend in the water, and fusiform streamlined structure can reduce the device flow resistance to measuring the influence and cooperate velocity of flow measuring device 4 to realize the biggest direction automatic selection of velocity of flow under the impact of rivers. The temperature measuring point is arranged at the tail end of the carrier and close to the flow velocity measuring device 4, signal receiving and transmitting in the device are realized through a sensing optical fiber in the device, laser emission and signal receiving are realized at the same side of the optical fiber, the technology is common technology in the field, detailed description is omitted, and the other end of the optical fiber can be connected with the same type of measuring device to realize the extended application of a plurality of measuring points.
The temperature and flow velocity sensing mechanism is shown in fig. 3-4, the temperature measurement point surface grid structure 14 realizes the exchange with the water body temperature, the optical fiber 15, the blade 8, the connecting rod 9 and the supporting shaft 7 which are transmitted to the tail end through good heat conduction metal are in a lever structure, the distance between the blade 8 and the supporting shaft 7 is larger than the distance between the connecting rod 9 and the supporting shaft 7, the lever structure is a stress application lever structure, and the stress on the blade 8 is transmitted to the T-shaped notch 11 through the connecting rod 9 and is applied to the optical fiber 15. The connecting rod 9 has a protruding structure with a soft magnet 13 attached to its surface, and an electromagnet 12 at a corresponding position on the carrier wall, the soft magnet 13 and the electromagnet 12 constituting the resetting means. The position of the optical fiber support body 10 is adjustable, so that a proper initial position between the optical fiber and the T-shaped notch 11 on the connecting rod 9 is ensured, and the limiting structure on the connecting rod 9 can ensure that the optical fiber works in a safe testing range without causing excessive deformation or damage of the optical fiber.
The following description is made of the measurement process of the above measurement apparatus: under the action of water flow, the direction of the fusiform streamline carrier can automatically select the optimal test posture, firstly, an electromagnet 12 in figure 3 works, a soft magnet 13 is adsorbed with the electromagnet 12 under the action of a magnetic field, so that a T-shaped notch 11 is not in contact with an optical fiber 15, the temperature of a water body is sensed through a metal 14 with a surface grid-shaped structure and is conducted to a connecting rod 9 through a good heat conductor, corresponding spectral characteristics are obtained, temperature data are demodulated, each point is the average value of the two temperature data, the electromagnet 12 is powered off after the temperature data are obtained, a blade 8 feels the impact action of the water flow, the acting force has a corresponding physical relation with the flow velocity, the flow velocity can be reflected by testing the acting force, the force felt by the blade 8 is amplified and transmitted to the connecting rod 9 and the T-shaped notch 11 through a lever principle and acts on the connecting rod 9 to generate, the signal receiving end obtains the laser spectral characteristics under this state and demodulates out temperature and stress combined action data, is the average value of two data to the measuring point too, and stress data can be dissociated out after the temperature data of adjacent position is rejected to this data to obtain water velocity of flow data, realize the purpose of measuring the velocity of flow, there is the different positions of a carrier in the measurement process of above-mentioned every measuring point equally, is also the same with the different carriers of same test fiber simultaneously: for the same carrier, each depth position corresponds to and forms a set with two measurement points on the left and right, and a plurality of sets of measurement points are distributed at different spaced depth positions, and the same measurement optical fiber channel can be connected with a plurality of measurement devices of the type in a series connection mode, so that a water body main parameter measurement network is constructed with lower cost.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the equipment or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (3)
1. A measuring device for distributed optical fiber water body temperature and flow velocity distribution comprises a carrier (1) and is characterized in that a rotating fulcrum (2) is connected in the carrier (1), one end of the rotating fulcrum (2) is connected with a base (6), a temperature measuring device (5) and a flow velocity measuring device (4) are arranged on the carrier (1), and an optical fiber hollow winding structure (3) is arranged in the carrier (1); the flow velocity measuring device (4) comprises a streamline blade (8), a limiting structure, an optical fiber tangential force application structure, a reset structure and a support shaft (7); the streamline blades (8) are of hollow structures, the sizes of the streamline blades are gradually increased along the water flow direction, one ends of the streamline blades (8) are connected with levers, and the other ends of the levers are connected with the supporting shaft (7) to form lever type force transmission structures; the lever type force transmission structure is a stress application lever structure and is connected with the optical fiber tangential force application structure and the streamline blade (8), and the distance from the force application structure to the support shaft (7) is smaller than the distance from the streamline blade (8) to the support shaft (7) and is on the same side; the optical fiber tangential force application structure comprises a connecting rod (9) connected with a lever, a T-shaped notch (11) is formed in the tail end of the connecting rod (9), an optical fiber supporting body (10) is connected to the inner wall of the carrier (1) in a specified mode, an optical fiber (15) is connected to the optical fiber supporting body (10), and one end of the optical fiber (15) is connected with metal (14) of a grid-shaped structure fixedly connected with the carrier (1); the limiting structure is positioned on a connecting rod (9) of the optical fiber tangential force application structure, and the reset structure comprises an electromagnetic coil (12) fixed on the carrier (1) and a soft magnet (13) attached to the connecting rod (9).
2. The distributed optical fiber water temperature and flow velocity distribution measuring device according to claim 1, wherein the carrier (1) is a hollow fusiform streamline structure, and a blade type flow velocity measurement conducting structure is arranged at the tail of the carrier (1).
3. The distributed optical fiber water body temperature and flow velocity distribution measuring device according to claim 2, wherein the optical fiber hollow winding structure (3) in the carrier (1) is a smooth approximately elliptical cylinder, and a plurality of optical fiber fixing devices are arranged on the surface of the optical fiber hollow winding structure (3).
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| CN100353167C (en) * | 2005-11-04 | 2007-12-05 | 南开大学 | Sensing device for optical fiber optical grating flow speed |
| EP1936332A1 (en) * | 2006-12-22 | 2008-06-25 | Nederlandse Organisatie voor Toegepast-Natuuurwetenschappelijk Onderzoek TNO | Karman vortex flowmeter assembly comprising a fiber Bragg grating sensor and method to measure a fluid flow rate |
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