Wake flow electromagnetic field test device based on circulating water tank

Abstract

The utility model relates to the field of magnetic detection, and provides a wake flow electromagnetic field test device based on a circulating water tank. The wake flow electromagnetic field test device comprises a circulating water tank, a magnetic field generator and a wake flow electromagnetic field measurement system, wherein the circulating water tank comprises a water tank main body, paddles, a transmission shaft, a driving motor and a bearing. The main body of the test device is designed based on the circulating water tank, the test model is fixed in the water tank, and the water flow circularly flows at a set speed by virtue of the power system, so that the wake flow electromagnetic field can be monitored in real time, and a long-time test can be carried out; in addition, a signal enhancement technology for the wake flow electromagnetic field test device is designed, and the sensitivity of signal detection is improved by increasing a background magnetic field, so that the reliability of a test result is enhanced.

Description

Technical Field

[0001] The utility model relates to the field of magnetic detection, in particular to a wake electromagnetic field test device based on a circulating water tank. Background Art

[0002] Seawater has a high electrical conductivity. When a submersible navigates underwater, it causes the conductive seawater to flow in the Earth's magnetic field. This movement cuts through the Earth's magnetic field lines. According to Faraday's law of electromagnetic induction, this process induces an electromotive force in the seawater, generating an electric current. These currents, in turn, generate an induced electromagnetic field, forming a wake electromagnetic field in the seawater. This electromagnetic field has a wide range and long duration. The development of a wake electromagnetic field test device and the corresponding detection methods are of great significance and potential application value for exploring the mechanism of submersible wake electromagnetic fields and the development of new detection technologies.

[0003] Under the geomagnetic background, the wake electromagnetic field generated by the navigation of the submersible is not only very weak and of low frequency, but also easily interfered by the low-frequency electromagnetic noise of the environment. Therefore, there are many challenges when directly applying advanced electromagnetic sensors to the wake electromagnetic field test device. At present, there is no good experimental system for wake testing. The current experimental system is often a temporary towed experimental system. This experimental system requires the continuous towing of the submersible model to move, which increases the difficulty of signal detection and makes it difficult to operate continuously for a long time. Utility Model Content

[0004] In order to better detect and test the wake magnetic field, the utility model proposes a wake electromagnetic field test device based on a circulating water tank, which can greatly improve the test capability of wake magnetic field detection: the main body of the test device of the utility model is designed based on a circulating water tank, and the test model is fixed in the water tank. With the help of a power system, the water flow circulates at a set speed, so that the wake electromagnetic field can be monitored in real time and long-term testing can be carried out because there is no need to repeatedly drag the model like the existing test device; and the utility model designs a signal enhancement technology for the wake electromagnetic field test device, which improves the sensitivity of signal detection by increasing the background magnetic field, thereby enhancing the reliability of the test results.

[0005] In summary, the wake electromagnetic field test device based on the circulating water tank proposed in this utility model provides a new technical means for the study of the electromagnetic field mechanism and detection method of the wake of a submersible, and has broad application prospects in the field of electromagnetic field characteristic analysis and detection of marine targets.

[0006] Specifically, the utility model provides a wake electromagnetic field test device based on a circulating water tank, the wake electromagnetic field test device comprising: a circulating water tank, a magnetic field generator and a wake electromagnetic field measurement system, the circulating water tank comprising a water tank body, blades, a transmission shaft, a drive motor and bearings, wherein the water tank body is made of corrosion-resistant, non-conductive and non-magnetic material, the water tank body forms an annular flow channel, the blades are arranged in the annular flow channel, one end of the transmission shaft passes through the side wall of the annular flow channel and is fixedly connected to the blades, and the other end is transmission-connected to the output shaft of the drive motor, the bearing is arranged at the position where the transmission shaft passes through the annular flow channel, the bearing is a sealed and waterproof bearing, a test model is arranged in the annular flow channel, the magnetic field generator is arranged outside the annular flow channel and on both sides of the test model, the wake electromagnetic field measurement system comprises an electric field sensor and a magnetic field sensor, and the electric field sensor and the magnetic field sensor are arranged downstream of the test model.

[0007] In a preferred implementation, the rotational speed of the drive motor changes periodically, and the change period is between 0.1 Hz and 2 Hz.

[0008] In another preferred implementation, the magnetic field generator is a pair of Helmholtz coils, which are respectively located on both sides of the test model position in the annular flow channel, and the electric field sensor and magnetic field sensor are arranged near the axis thereof, so that a uniform area with a magnetic contour uniformity of more than 95% covers the measurement position of the electric field sensor and the magnetic field sensor.

[0009] In another preferred implementation, the circulating water tank is made of fiberglass reinforced plastics, and the bearing is a ceramic bearing.

[0010] In another preferred implementation, a reducer is further included, and the output shaft of the servo motor is in driving connection with the reducer, and the output shaft of the reducer is connected to the transmission shaft via a coupling.

[0011] In another preferred implementation, the wake electromagnetic field test device further includes a velocity sensor for measuring the water flow velocity in the water tank.

[0012] In another preferred implementation, the electric field sensor is a silver or silver chloride type electric field sensor, the magnetic field sensor is a fluxgate type magnetic sensor, and the electric field sensor and the magnetic field sensor are arranged in a uniform magnetic field region of a Helmholtz coil.

[0013] The utility model has the following advantages:

[0014] First, this utility model utilizes a circulating water tank structure, which offers significant advantages over towing tanks. While towing tanks have limited testing time due to track constraints, the circulating water tank utilizes a power system to circulate water at a constant rate, allowing the test model to be measured in flowing water. This provides the required simulation environment for extended periods without causing towing damage to the model, and provides a more stable simulation environment. The ability to conduct long-term testing in the circulating water tank not only facilitates the measurement of the wake electromagnetic field, but also allows for observation and video recording through the tank's observation windows. Furthermore, the circulating water tank offers the advantages of low investment, minimal footprint, and rapid results.

[0015] Second, this utility model designs a signal enhancement technology for a wake electromagnetic field test device. By periodically varying the fluid velocity, this technology achieves spectrum shifting, increasing the frequency of the wake electromagnetic field signal, thereby reducing the 1 / f noise impact of the electric and magnetic field sensors. Furthermore, a magnetic field generator is used to enhance the background magnetic field in the wake region, increasing the strength of the wake electromagnetic field signal and reducing the measurement difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the wake electromagnetic field test device used in the embodiment of the present utility model;

[0017] Figure 2 This is a schematic diagram of a water tank body in a circulating water tank in an embodiment of the present utility model;

[0018] Figure 3 This is a schematic diagram of the paddles and transmission shaft in the circulating water tank in an embodiment of the present utility model;

[0019] Figure 4 This is a schematic diagram of a bearing in a circulating water tank in an embodiment of the present utility model;

[0020] Figure 5 This is a schematic diagram of the overall connection of the circulating water tank in the embodiment of the present utility model;

[0021] Figure 6 This is a schematic diagram of the water tank impeller in the embodiment of the present utility model;

[0022] Figure 7 This is the subcritical flow in the channel in the embodiment of the present utility model;

[0023] Figure 8 This is the speed control UI interface in the embodiment of the present utility model;

[0024] Figure 9 This is the placement of the circular Helmholtz coil in the embodiment of the present utility model;

[0025] Figure 10The spatial magnetic field uniform distribution area of ​​the Helmholtz coil in the embodiment of the present utility model is divided;

[0026] Reference numerals: current source 1, test model 2, data collector 3, Helmholtz coil 4, sensor 5, blade 6, transmission shaft 7, drive motor 8, data line 9 DETAILED DESCRIPTION

[0027] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0028] like Figure 1 As shown in the figure, in this embodiment, the wake electromagnetic field test apparatus comprises three main components: a circulating water tank, a magnetic field generator, and a wake electromagnetic field measurement system. All three components are powered by a current source 1. The circulating water tank includes the main body, propeller blades 6, a transmission shaft 7, bearings, and a drive motor 8. The wake electromagnetic field measurement system includes an electric field sensor, a magnetic field sensor (collectively referred to as sensors 5), and a data collector 3.

[0029] The water tank body is the core structure of the entire device and is made of corrosion-resistant, non-conductive and non-magnetic materials such as fiberglass. This material not only resists salt water corrosion but also does not interfere with the measurement of the wake electromagnetic field. Figure 2-4 As shown in the figure, it shows the various parts of the circulating water tank, including the tank body, paddles, transmission shaft and bearings. Figure 5 The overall connection diagram of the circulating water tank is shown.

[0030] The flume is roughly annular, consisting of an inner and outer ring with a sealed bottom. The space between the inner and outer rings serves as a water channel. To ensure smooth fluid flow, the flume's interior features a streamlined geometry to reduce fluid resistance and enhance flow intensity. A test model is secured within the flume, and the circulating motion of the fluid generates a wake behind the model, which is then measured for its resulting electromagnetic field.

[0031] The paddle is another key component that promotes fluid circulation through rotation. Its design must follow the principles of fluid dynamics to maximize efficiency and minimize energy consumption, and is designed to be spiral. In addition to the shape, the material of the paddle is equally important. High-strength and corrosion-resistant materials, such as high-quality engineering plastics, should be selected to ensure that it does not deform or corrode during long-term operation. The paddle in this embodiment includes four blades whose shapes roughly match the flow channel. The four blades are arranged around a rotating shaft, and the blade rotating shaft is perpendicular to the propulsion direction of the water flow.

[0032] The blades are connected to the external drive device (drive motor) through a drive shaft, which is the core component of the system's power transmission. One end of the drive shaft passes through the outer wall of the circulating water tank and is fixedly connected to the blades, and the other end is connected to the output shaft of the drive motor. If a reducer is used, it is connected to the output shaft of the reducer. The drive shaft not only needs high strength to meet the requirements of high-speed rotation, but also needs to have excellent corrosion resistance. High-quality engineering plastics are selected for materials to provide sufficient corrosion resistance and mechanical strength. In addition, the design of the drive shaft must take into account the dynamic balance of the system to prevent vibration and instability caused by high-speed rotation. In order to improve the flexibility of the system, the drive shaft is designed to be detachable or equipped with a quick connection device to facilitate the installation and maintenance of the equipment.

[0033] Bearings (preferably sealed bearings) are installed on one or both sides of the circulating water tank, and the propeller shaft passes through the bearings and is fixed on the outer wall. In order to adapt to the use environment, ceramic bearings are selected.

[0034] In addition to the aforementioned components, an automated control system can be used to further enhance the overall performance and applicability of the circulating water tank. This controls the speed of the drive motor (or servo motor), thereby controlling the flow rate of the water in the flow channel. The drive motor has a power of 750W, and its speed is controlled by a controller or control circuit.

[0035] The working process is as follows: the speed input is given to the servo motor on the far right to drive the flow of water in the circulating water tank.

[0036] The motor can realize variable speed rotation (the frequency of the speed change can be set). This control method can realize the variable flow of water and provide support for the test.

[0037] Preferably, before the test, a speed sensor is used to measure the water flow velocity in the water tank, the power of the drive motor is adjusted, and the steady-state upper limit and steady-state lower limit of the water flow velocity are determined (the steady-state upper limit and lower limit here refer to the upper and lower limits of the speed that will not cause excessive splashing of water flow or large vibration of the equipment, and can achieve a certain degree of required flow), as well as the steady-state upper limit speed and steady-state lower limit speed of the drive motor when the water flow velocity reaches the steady-state upper limit and steady-state lower limit. The speed sensor is removed, and the electric field sensor and magnetic field sensor are inserted, and the speed of the drive motor is periodically adjusted between the steady-state upper limit speed and the steady-state lower limit speed or between the local intervals of the two.

[0038] In this embodiment, the water tank body is made of fiberglass, and the blade bearings and blade baffles are made of high-quality engineering plastics to ensure that no electric and magnetic field interference is introduced. The drive shaft is fixed to the drive motor through a coupling and connected to the blades by a latch. A splash-proof cover can also be provided on the water tank, and the water tank and the splash-proof cover are fixed with snaps. The bearings on both sides of the blades rotate in conjunction with the bearing base using ceramic bearings. The bearing base is fixed to the water tank through openings and a retaining ring is used to prevent the bearing from falling off. The bottom of the water tank and the bottom of the motor base are kept at the same level. The base needs to be fixed for shock absorption.

[0039] The following theoretical analysis reveals the effectiveness of increasing the test signal strength by increasing the background magnetic field in this patent.

[0040] The wake motion can be characterized by the balance of mass and momentum, which is described by the continuity equation and the Navier-Stokes equations, as shown in Equation (1):

[0041]

[0042] Where u is the wake velocity, p is the seawater pressure, ρ is the seawater density, and μ is the seawater dynamic viscosity. The left side of the Navier-Stokes equation corresponds to the inertial force, while the terms on the right side correspond to the pressure, viscous force, and external forces acting on the seawater. Under the influence of the Earth's magnetic field, the wake electric field E and the wake magnetic field B satisfy Maxwell's electromagnetic theory:

[0043]

[0044] Among them, equations (2) and (3) are expressions of Maxwell's equations. The tail induced current conduction density is J = σ (E + v0 × B E ), σ is the conductivity of seawater, B E represents the background magnetic field, and v0 is the wake velocity.

[0045] It is generally believed that the conduction current density of seawater is much greater than the displacement current density. Therefore, the second term on the right side of the equal sign in equation (3) can be ignored. The wake electromagnetic field can be expressed as:

[0046] E(r)=v0(r)×B(r)=v0(r)×(B E (r)+B i (r))≈v0(r)×B E (r)(4)

[0047]

[0048] According to equations (4) and (5), it can be seen that the wake electromagnetic field is proportional to the flow velocity. By controlling the periodic variation of the flow velocity, the measurement frequency of the wake electromagnetic field can be increased, thereby reducing the impact of the 1 / f noise of the electric and magnetic field sensors.

[0049] 2. Magnetic field generator

[0050] According to equations (4) and (5), it can also be seen that the wake electromagnetic field is proportional to the background magnetic field. Using a magnetic field generator can enhance the background magnetic field in the wake region, increase the strength of the wake electromagnetic field signal, and reduce its measurement difficulty.

[0051] Consider the attached Figure 9 The arrangement of the Helmholtz coils shown is that the two coils have a diameter of 800 mm and a spacing of 40 mm. A current of 2.5 A is passed through the coils, and the number of turns is 200.

[0052] When setting up the Helmholtz coil, the uniform area of ​​the magnetic field generated by the coil covers the detection area. Taking the 95% uniform area as an example, its entire area is similar to a spindle with a maximum width of 13cm. If the maximum length of the 99% uniform area is used as the uniformity zone parameter, the entire area is a diamond-shaped area with a diagonal length of 13cm x 25cm. The magnetic field sensor and electric field sensor can be placed within this area.

[0053] The area is 0.5×13 cm×25 cm=162.5 cm 2 . The sensor size can be determined based on the area of ​​the region, or different Helmholtz coils can be selected based on the sensor size so that the sensor measurement area is located within the uniform area.

[0054] 3. Wake electromagnetic field measurement system

[0055] Silver / silver chloride type electric field sensor and fluxgate type magnetic sensor are used to measure the wake electric field and wake magnetic field, respectively.

[0056] At the back end of the patented device, a high-resolution data collector can be added to convert the analog signal of the sensor into a digital signal, thereby facilitating the data analysis method to extract the wake electromagnetic field signal, and a signal processor is used to process the obtained signal.

[0057] Although the principles of the present invention have been described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are merely illustrative of the implementation of the present invention and are not intended to limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Without departing from the spirit and scope of the present invention, any obvious changes such as equivalent transformations and simple substitutions based on the technical solutions of the present invention fall within the scope of protection of the present invention.

Claims

1. A wake electromagnetic field test device based on a circulating water tank, characterized in that: The wake electromagnetic field test device includes: a circulating water tank, a magnetic field generator and a wake electromagnetic field measurement system, wherein the circulating water tank includes a water tank body, blades, a transmission shaft, a drive motor and bearings, wherein the water tank body is made of corrosion-resistant, non-conductive and non-magnetic material, the water tank body forms an annular flow channel, the blades are arranged in the annular flow channel, one end of the transmission shaft passes through the side wall of the annular flow channel and is fixedly connected to the blades, and the other end is transmission-connected to the output shaft of the drive motor, the bearing is arranged at the position where the transmission shaft passes through the annular flow channel, the bearing is a sealed and waterproof bearing, a test model is arranged in the annular flow channel, the magnetic field generator is arranged outside the annular flow channel and on both sides of the test model, and the wake electromagnetic field measurement system includes an electric field sensor and a magnetic field sensor, and the electric field sensor and the magnetic field sensor are arranged downstream of the test model.

2. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: The rotation speed of the driving motor changes periodically, and the change period is between 0.1 Hz and 2 Hz.

3. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: The magnetic field generator is a pair of Helmholtz coils, which are respectively located on both sides of the test model position in the annular flow channel, and the electric field sensor and the magnetic field sensor are arranged near the axis thereof, so that the uniform area with a magnetic contour uniformity of more than 95% covers the measurement position of the electric field sensor and the magnetic field sensor.

4. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: The circulating water tank is made of glass fiber reinforced plastic material, and the bearing is a ceramic bearing.

5. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: It also includes a reducer, the output shaft of the drive motor is in transmission connection with the reducer, and the output shaft of the reducer is connected to the transmission shaft through a coupling.

6. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: The wake electromagnetic field test device further comprises a data collector for collecting signals measured by the electric field sensor and the magnetic field sensor.

7. The wake electromagnetic field test device based on a circulating water tank according to claim 1 is characterized in that: Also included is a velocity sensor to measure the velocity of the water in the flume.

8. The wake electromagnetic field test device based on a circulating water tank according to claim 3 is characterized in that: The electric field sensor is a silver or silver chloride type electric field sensor, the magnetic field sensor is a fluxgate type magnetic sensor, and the electric field sensor and the magnetic field sensor are arranged in a uniform magnetic field region of a Helmholtz coil.

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