A ship's underwater shaft frequency electric field on-board in-situ monitoring device

Abstract

The present invention belongs to the technical field of underwater shaft frequency electric field of ships, and specifically relates to an on-board in-situ monitoring device for underwater shaft frequency electric field of ships. The main structure includes a hull connector and an on-board in-situ fixing bracket arranged on the outside of the hull, a conductive rod sealing box and a watertight mechanism arranged inside, and a sensor probe arranged on the on-board in-situ fixing bracket. When in use, it is connected with ordinary high-frequency electric potential sampling equipment available on the market to achieve long-term and effective in-situ real-time monitoring of the underwater shaft frequency electric field; through in-situ monitoring, the slight changes in the electric field potential and the signal characteristic laws at the shaft frequency can be grasped in real time; through the electric potential fluctuations on the hull surface with the same frequency characteristics as the propeller-shaft rotation, the peak value changes of the shaft frequency characteristic peaks before and after the electric field control are extracted in real time, the suppression ratio of the ship's shaft frequency electric field strength is independently judged, and the concealment effect of the shaft frequency electric field is grasped and regulated in real time; the electric potential parameters of the hull surface above the propeller-shaft are captured in real time in situ by the sensor probe.

Description

Technical field:

[0001] The present invention belongs to the technical field of underwater shaft frequency electric field of ships, and specifically relates to an on-board in-situ monitoring device for underwater shaft frequency electric field of ships, so that the ship can grasp its own underwater shaft frequency electric field suppression effect in-situ throughout its entire life cycle. Background technology:

[0002] With the improvement of ship vibration and noise reduction technology, non-acoustic signals such as underwater shaft frequency electric field have become an important signal source for underwater enemy detection and attack. The main mechanism of the generation of underwater shaft frequency electric field of ships is as follows: Figure 1 As shown in the figure: During the rotation of the propeller, the grounding resistance between the shaft and the hull changes periodically, causing the corrosion or cathodic protection current flowing back to the hull through the shaft and bearings to be modulated. The fluctuation frequency of the modulated current is consistent with the shaft frequency, and the shaft frequency modulated current generates a shaft frequency electric field underwater.

[0003] The underwater shaft-frequency electric field of a ship has extremely low-frequency signal characteristics, with obvious frequency line spectrum characteristics of about 0.1-10Hz (related to the ship's propeller speed), and there are obvious frequency-multiplication signal characteristics, so it has the characteristics of long-distance propagation. Generally, the signal strength is on the order of μV. At the same time, the source of the ship's underwater shaft-frequency electric field is basically clear, and it has the characteristics of being detectable, measurable, and controllable. In the existing technology, the detection of the ship's underwater shaft-frequency electric field is mainly achieved through indirect measurement by a third-party measurement ship using an electric field measurement array deployed in the test sea area. The measured ship cannot immediately perceive the effect of its own shaft-frequency electric field control. As the service time of the ship increases and the service environment changes, the crew cannot adjust the working status of the electric field protection system in time, which may lead to the uncontrollable characteristics of the ship's underwater shaft-frequency electric field, seriously affecting its safety and reliability when performing tasks.

[0004] Chinese patent 201320328964.X discloses a low-noise ship shaft frequency electric field measurement system, including an electric field sensor, a signal conditioning circuit, and a data acquisition system connected in sequence. The electric field sensor includes four measuring electrodes and a reference electrode for measuring the potential difference between two points in three orthogonal directions in seawater. The four measuring electrodes include a first electrode located at the coordinate origin, a third electrode, a fourth electrode, and a second electrode located in three orthogonal directions of the coordinate origin and capable of forming electric field measurement electrode pairs in corresponding directions with the first electrode. The reference electrode includes a fifth electrode. The fifth electrode is a reference electrode, arranged near the third electrode, and connected to the ground wire of the signal conditioning circuit. The signal conditioning circuit includes a preamplifier circuit, a filter circuit, a secondary amplifier circuit, and a level conversion circuit connected in sequence between the electric field sensor and the data acquisition system. The preamplifier circuit mainly includes a low-noise instrumentation amplifier AD624. The filter circuit mainly includes an 8th-order low-pass active filter and a 2nd-order high-pass active filter arranged in series, both of which adopt a Butterworth structure. The principle of the shaft-frequency electric field measurement method was confirmed in laboratory-scale seawater environments using a scaled-down model driven by electrodes at a constant speed. However, the laboratory environment is different from actual engineering applications, and it is uncertain whether it can be applied in the complex environment of real seas and ships. In addition, the electric field sensors used in the three-axis measurement system are arranged in a three-dimensional space outside the ship model. When used, they need to be calibrated with a remote reference electrode in the same space. In this measurement method, the sensor measurement dimension and the dimension generated by the shaft-frequency field source are in relative motion. Therefore, this method cannot achieve in-situ measurement and self-perception of the underwater electric field of a ship when the shaft-frequency electric field measurement point and the source are in a relatively static state.

[0005] Chinese Patent 201910140651.3 discloses a ship tracking and positioning method based on shaft-frequency electric fields, comprising the following steps: S1) establishing two or more ship shaft-frequency electric field measurement nodes; S2) using the measurement nodes to measure the ship's shaft-frequency electric field signals in real time; S3) calculating the envelope of the measured shaft-frequency electric field signals; S4) modeling the shaft-frequency electric field envelope signals using a unit current source model and establishing a Kalman filter observation model; S5) using the Kalman filter method to estimate the ship's state information based on the measured shaft-frequency electric field envelope signals to achieve ship tracking and positioning. The method involves establishing two or more ship shaft-frequency electric field measurement nodes in the measurement area, acquiring the shaft-frequency electric field signals of the measured ship through a measurement array composed of the measurement nodes, performing real-time calculation and analysis of the measurement data, and tracking and positioning the target ship.

[0006] Chinese patent 202211189953.8 discloses a ship shaft frequency electric field detection system and method, which includes the following steps: S1.1: recording the propeller speed range and corresponding shaft frequency of different types of ships for storage; S1.2: installing an electric field measurement system on the bottom of the detected ship to detect the underwater signal; S1.3: performing noise processing on the measured signal data of the detected ship by constructing a function model and confirming the basic information of the detected ship; S1.4: measuring the signal of the detected ship again to obtain the position, forward direction and forward speed of the detected ship; S1.5: the visual screen simulates the driving status of the detected ship. And a ship shaft frequency electric field detection method disclosed in Chinese patent 202110360409.4 includes an electric field detection device, a display system and a computing device. The number of electric field detection devices is two, and the two electric field detection devices are fifteen meters apart. The specific detection steps are: Step 1, data entry: input the propeller speed range and shaft frequency electric field information corresponding to various ship types into the computing device; Step 2, ship type detection: in the process of detecting the movement of the ship, the electric field detection device is used to detect the surrounding electric field, and the detected shaft frequency electric field and the corresponding shaft frequency electric field of the ship recorded in the first step are analyzed to analyze the ship type, and the ship type information is transmitted to the display system for display; Step 3, ship angle detection: two electric field detection devices The device records the corresponding shaft-frequency electric field transmission angle. Fourth, position calculation: The computing device combines the electric field propagation angle of the detected vessel in step 3 and the distance between the two electric field detection devices to calculate the direction of the detected vessel and the distance between the detected vessel and the detecting vessel at this time, thereby determining the position of the detected vessel. Fifth, secondary detection: After the detecting vessel moves for 1 to 2 seconds, the detected vessel's position is continuously detected using steps 3 and 4. Simultaneously, the computing device calculates the moving speed of the detected vessel based on the distance between the two detected positions. Sixth, position display: The computing device transmits the detected vessel's position signal and travel information to the display system, which then displays the detected vessel's position and travel information. These two processes, through two or more electric field detection device measurement nodes, employ steps such as data entry, vessel type detection, vessel angle detection, position verification, secondary detection, and position display to achieve target vessel detection and positioning within the limitations of acoustic detection technology. Although it has developed from laboratory exploration to actual engineering application, the detection dimension has always been to monitor the dynamic shaft frequency field source by an underwater static sensor array. No in-situ onboard monitoring method for underwater shaft frequency electric field in the same spatial dimension with the monitoring sensor and the actual ship shaft frequency field source being relatively stationary has been proposed. There is a lack of effective means for ships to actively and immediately grasp the characteristic intensity of their own underwater shaft frequency electric field.

[0007] Chinese patent 201710046480.9 discloses a ship shaft frequency electric field suppression device and its suppression method, which includes a rectifier module, a power module and a control module. The rectifier module is connected to the power module, which is connected to the control module. The rectifier module is provided with a current input terminal, the power module is provided with a current output terminal, and the control module is provided with a signal processing board, a current control board, a power monitoring board, a display driver board, and a status display board; the signal processing board is connected to the shaft housing current signal input terminal, the signal processing board is connected to the display driver board, and the display driver board is connected to the status display board; the signal processing board is provided with an amplifier circuit, which includes three stages, the first stage is an instrument amplifier, and the second and third stages are reverse amplifiers; the signal processing board is connected to the current control board, and the current control board is provided with a high-pass filter circuit, a first low-pass filter circuit, a second low-pass filter circuit, an absolute value circuit and a voltage follower; the current control board is connected to the power monitoring board, and the power monitoring board is connected to the power module. This method collects the shaft housing current signal of the load from the outside of the ship, and after signal amplification, DC component filtering, and AC component output, the power module outputs a counteracting current. This method focuses on the process of electric field suppression, but does not detect the results of electric field suppression. It lacks a means for the ship itself to independently assess the results of underwater shaft frequency electric field suppression. Therefore, the inventors have developed and designed a ship's underwater shaft frequency electric field onboard in-situ monitoring device. This device allows relevant crew members to monitor their own underwater shaft frequency electric field strength at any time throughout the ship's lifecycle, instantly determine the control effect of the ship's underwater shaft frequency electric field, and proactively and promptly monitor the ship's underwater shaft frequency electric field strength, thereby enhancing safety and concealment and improving the ship's vitality. Summary of the invention:

[0008] The purpose of the present invention is to overcome the shortcomings of the existing technology and to develop and design an on-board in-situ monitoring device for the underwater shaft frequency electric field of a ship, which is directly installed and fixed on the ship. By providing real-time feedback on the changes in the shaft frequency domain characteristics before and after the control of the ship's shaft frequency electric field, the control effect of the ship's underwater shaft frequency electric field can be instantly judged and mastered.

[0009] In order to achieve the above-mentioned purpose, the main structure of the ship's underwater shaft frequency electric field on-board in-situ monitoring device involved in the present invention includes a hull connector and an on-board in-situ fixed bracket arranged on the outside of the hull, a conductive rod sealing box and a watertight mechanism arranged inside, and a sensor probe arranged on the on-board in-situ fixed bracket; wherein, a sealing gasket is arranged between the hull connector and the hull and the on-board in-situ fixed bracket, and the sensor probe has a sensor cover.

[0010] The hull connector involved in the present invention is made of a mesh glass fiber composite material and has a conductive rod arranged in the center; the ship's in-situ fixing bracket is made of a mesh glass fiber composite material and has a mounting slot; the main structure of the sensor probe includes a probe body and a probe working surface arranged on the outside, a sensor wire arranged on the top, and the sensor wire is connected to the conductive rod.

[0011] The sensor probe of the present invention has a standard error of accuracy of ≤0.1mV and self-noise

[0012] ≤5nV / (@1Hz), prepared by melt-pressing impregnation method, the preparation process is as follows:

[0013] First, the powdered electrode core material is heat-melted and die-cast with the mesh electrode cover in a mold to form the probe body;

[0014] Then, the probe body is placed in a polar solution and repeatedly immersed in cooling until the surface of the mesh electrode cover forms a long-lasting and stable probe working surface;

[0015] Finally, the probe body, sensor wire and sealing plug are cured and packaged.

[0016] The present invention relates to an on-board in-situ monitoring device for underwater shaft frequency electric field of a ship. When used, the device is installed above the propeller-shaft of the ship and connected to a host computer via a cable. The host computer is a commercially available conventional potential sampling device with a high sampling frequency. The sampling frequency is set to ≥100Hz. The sensor probe captures the potential parameter change parameters of the hull surface above the propeller-shaft at the shaft frequency in real time, obtains characteristic data containing the fluctuations of the underwater shaft frequency electric field of the ship, and extracts the potential fluctuations on the hull surface with the same frequency characteristics as the propeller-shaft rotation of the ship through real-time data processing. The peak value changes of the characteristic peaks of the shaft frequency before and after control are analyzed, so that the crew can timely grasp the control effect of the underwater shaft frequency electric field of the ship. The shaft frequency electric field data results obtained in real time by the in-situ monitoring device can be used to guide the adjustment and optimization of the working parameters of the underwater shaft frequency electric field suppression device.

[0017] Compared with the prior art, the present invention can realize long-term and effective in-situ real-time monitoring of underwater shaft frequency electric field by connecting with ordinary high-frequency electric potential sampling equipment purchased on the market, which greatly reduces the threshold for use. Crew members can operate it after simple training; through in-situ monitoring, the slight changes in electric field potential at the shaft frequency and the signal characteristic laws can be grasped in real time, making it possible to capture the underwater shaft frequency electric field characteristics of the ship on board in actual engineering applications; through the potential fluctuations on the hull surface with the same frequency characteristics as the propeller-shaft rotation, the peak value changes of the shaft frequency characteristic peak before and after the electric field control are extracted in real time, the suppression ratio of the ship's shaft frequency electric field strength is independently judged, and the concealment effect of the shaft frequency electric field is grasped and regulated in time; the potential parameters of the hull surface above the propeller-shaft are captured in real time in situ by the sensor probe, which reduces the difficulty of engineering application and realizes the same-space-dimensional signal collection and analysis when the signal detection end and the actual ship's shaft frequency field source are relatively stationary. Description of the drawings:

[0018] Figure 1 This is a schematic diagram of the generation mechanism of the underwater shaft frequency electric field of a ship involved in the background technology of the present invention.

[0019] Figure 2 It is a schematic diagram of the main structural principle of the present invention.

[0020] Figure 3 It is a schematic diagram of the explosion decomposition of the main structure of the present invention.

[0021] Figure 4 It is a cross-sectional schematic diagram of the outer cabin portion of the main structure of the present invention.

[0022] Figure 5 It is a cross-sectional schematic diagram of the cabin interior of the main structure of the present invention.

[0023] Figure 6 This is a cross-sectional schematic diagram of the sensor probe involved in the present invention.

[0024] Figure 7 This is a schematic diagram of the installation of the sensor probe involved in the present invention.

[0025] Figure 8 This is a schematic diagram of the actual measured state of the present invention under real sea and real ship conditions.

[0026] Figure 9 This is a comparison diagram of the frequency domain characteristic peak values ​​before and after the shaft frequency electric field suppression obtained by actual measurement after the present invention was installed on board. Specific implementation method:

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1:

[0029] The main structure of the ship underwater shaft frequency electric field on-board in-situ monitoring device involved in this embodiment is as follows: Figure 2-5 As shown, it includes a hull connector 2, an onboard in-situ fixing bracket 3, a sealing gasket 4, a sensor probe 5, a sensor clamping bolt 6, a sensor cover 7, a conductive rod sealing box 8 and a watertight mechanism 9; the hull connector 2 and the onboard in-situ fixing bracket 3 are sequentially arranged on the outside of the hull 1, and a sealing gasket 4 is arranged between the hull connector 2 and the hull 1 and the onboard in-situ fixing bracket 3. Four sensor probes 5 are arranged on the onboard in-situ fixing bracket 3 at equal intervals, and the onboard in-situ fixing bracket 3 is connected to the sensor probe 5 by a sensor clamping bolt 6. The sensor probe 5 has a sensor cover 7. A conductive rod sealing box 8 is arranged inside the hull 1, and a watertight mechanism 9 is arranged outside the conductive rod sealing box 8.

[0030] Among them, the hull connector 2, the ship's in-situ fixing bracket 3, the sealing gasket 4, the sensor probe 5, the sensor clamping bolt 6 and the sensor cover 7 are mechanically fastened to the outer surface of the hull 1, and the conductive rod sealing box 8 and the watertight mechanism 9 are welded to the inner surface of the hull 1.

[0031] The center of the hull connector 2 of this embodiment is provided with a cylindrical cavity structure supporting boss 21, the interior of the supporting boss 21 is provided with four conductive rods 22, and the lower surface of the hull connector 2 is embedded with a wire groove 23;

[0032] Four mounting grooves 31 are evenly spaced on the ship's in-situ fixing bracket 3. The upper opening of the mounting groove 31 is a truncated cone-shaped clamping ring 32 with a wide upper and narrow lower structure, and the lower opening is a cylindrical annular groove 33 with an internal thread structure.

[0033] The main structure of the sensor probe 5 is as follows Figure 6-7 As shown, the probe body 51 includes a probe body 51, a fixing fixture 52, a probe housing 53, a probe working surface 54, a sensor wire 55, a sealing plug 56, and a sealing ring 57. The probe body 51 is arranged inside the probe housing 53 by the fixing fixture 52 having an internal and external thread structure. The probe body 51 is provided with a probe working surface 54 on the outer surface, and a sensor wire 55 and a sealing plug 56 are provided on the top. A sealing ring 57 is provided between the fixing fixture 52 and the clamping ring 32. The sensor wire 55 passes through the sealing plug 56 and is laid along the wire groove 23, and is finally welded to the conductive rod 22.

[0034] The sensor clamping bolt 6 is composed of a truncated cone structure with an isosceles trapezoidal cross section, wide at the top and narrow at the bottom, with a threaded cavity in the middle. It is placed in the clamping ring 32 and is threadedly connected to the end of the fixing tool 52.

[0035] The sensor cover 7 is threadedly connected to the annular groove 33 so that the sensor probe 5 is located in the mounting groove 31 to prevent the sensor probe 5 from being damaged by collision;

[0036] The main structure of the conductive rod sealing box 8 includes a sealing box shell 81, a hull connector sealing ring 82, a conductive rod sealing gasket 83, a conductive rod sealing ring 84, a sealing box base 85, a sealing box plug 86 and a sealing box tightening nut 87; a sealing box shell 81 is provided on the periphery of the end where the conductive rod 22 enters the hull 1, and a hull connector sealing ring 82, a conductive rod sealing gasket 83 and a conductive rod sealing ring 84 are provided inside; a sealing box base 85 is provided at the bottom of the sealing box shell 81, and a sealing box plug 86 is provided at the top; the sealing box base 85 is welded and installed to the hull 1.

[0037] The main structure of the watertight mechanism 9 includes a watertight mechanism shell 91, a watertight mechanism upper cover 92, a cable sealing box 93, a cable 94, a watertight mechanism fixing bolt 95, a cable tightening nut 96 and a conductive rod nut assembly 97; a watertight mechanism upper cover 92 is provided on the top of the watertight mechanism shell 91, and a cable sealing box 93 is provided on the side, and the cable 94 passes through the cable sealing box 93 and is connected to the conductive rod 22; the watertight mechanism shell 91 and the watertight mechanism upper cover 92 are connected by the watertight mechanism fixing bolt 95; the cable 94 and the cable sealing box 93 are connected and sealed by the cable tightening nut 96, and are connected to the conductive rod 22 by the conductive rod nut assembly 97.

[0038] The hull connector 2 of this embodiment has the characteristics of high strength, light weight, and excellent rigidity. Ten through holes are opened on the edge to allow fixing studs to penetrate through the holes to fix the hull connector 2 to the hull 1.

[0039] The onboard in-situ fixing bracket 3 is based on the toughness of the mesh glass fiber composite material itself, is easy to install and fix to the hull 1, and closely fits the streamlined design structure of the outer surface of the hull, reducing the seawater resistance of the ship during navigation;

[0040] The distance between the center points of two adjacent installation grooves 31 is 1 meter;

[0041] The probe housing 53 is made of an organic composite material and has a number of small holes evenly distributed on its surface to facilitate the exchange of seawater. It is screwed to the fixing fixture 52 and securely fastened to the probe body 51 and the probe working surface 54.

[0042] The sealing box housing 81, sealing box base 85, watertight mechanism housing 91, watertight mechanism upper cover 92, and cable sealing box 93 are all made of ordinary low-carbon steel. The conductive rod sealing gasket 83, sealing box plug 86, cable compression nut 96, and conductive rod nut assembly 97 are all made of brass.

[0043] The connection between the sealing box base 85 and the hull connector 2 is sealed by the hull connector sealing ring 82, the conductive rod sealing gasket 83, and the conductive rod sealing ring 84, and the internal cavity of the sealing box shell 81 is filled with sealant;

[0044] The cable 94 includes a multi-core shielded cable, and the signal monitored by the sensor probe 5 is transmitted to the host computer via the cable 94 .

[0045] Example 2:

[0046] The installation process of the ship underwater shaft frequency electric field onboard in-situ monitoring device involved in this embodiment is as follows:

[0047] Use the spray derusting method to thoroughly remove the scale, rust, etc. on the outer surface of the hull 1 and the surface of the fixing studs, so that the surface cleanliness reaches Sa 2 1 / 2 level in GB8923-88;

[0048] Welding the watertight mechanism 9 and the sealing box base 85 to the inner surface of the hull 1, and welding fixing studs to the outer surface of the hull 1;

[0049] Fix the sensor probe 5 to the onboard in-situ fixing bracket 3 using the sensor clamping bolts 6 and tighten the sensor cover 7;

[0050] Lay the sensor wire 55 in the wire groove 23 and weld it to the conductive rod 22;

[0051] Apply a layer of sealant on both sides of the upper sealing plate 4, covering the upper surface of the packaged hull connector 2, and apply sealant on both sides of the lower sealing plate 4. Install them from bottom to top in the order of the ship's in-situ fixing bracket 4, the lower sealing plate 4, and the hull connector 2;

[0052] Align the support boss 21 with the sealing box base 85, align the through-holes on the hull connector 2 with the fixing studs on the outer surface of the hull 1, insert the support boss 21 into the sealing box housing 81, fine-tune the position and angle to ensure that the conductive rod 22 is perpendicular to the surface of the hull 1 inside the sealing box housing 81, secure with fasteners, and wait for the sealant to cure;

[0053] Install the hull connector sealing ring 82, conductive rod sealing gasket 83, conductive rod sealing ring 84, and sealing box plug 86 into the sealing box housing 81 in sequence. During installation, pour a proper amount of sealant into the inner cavity of the sealing box housing 81 to further improve the sealing performance. Finally, install the sealing box compression nut 87 and tighten it.

[0054] The cable 94 is connected to the conductive rod 22 , the watertight mechanism is sealed with sealing putty, and the watertight mechanism housing 91 and the watertight mechanism upper cover 92 are connected and fastened with fixing bolts 95 .

[0055] Example 3:

[0056] The actual measurement process of the ship underwater shaft frequency electric field onboard in-situ monitoring device involved in this embodiment under real sea and real ship conditions is as follows:

[0057] like Figure 8 As shown, the shaft frequency electric field suppression device ① is installed in the shaft tunnel of the test ship's cabin. The entire test ship is made of a steel hull ②, the shaft system ③ is coated with non-metallic materials to electrically insulate it from seawater, and the propeller ⑤ is made of aluminum bronze.

[0058] Install the ship's underwater shaft frequency electric field on-board in-situ monitoring device ④ amidships at a vertical height of 1.0m below the waterline.

[0059] A 4-channel 24-bit potential acquisition device is used as the host computer to reduce environmental electromagnetic noise interference. The positive pole of the host computer is connected to the hull, and the negative pole is connected to the four sensor probes on the ship's underwater shaft frequency electric field on-board in-situ monitoring device;

[0060] Set the sampling frequency to no less than 100 Hz, the total cathodic protection current to 5 A, and the propeller ⑤ speed to 77 rpm. Make the test vessel sail at a constant speed in the north-south direction at a fixed longitude. Start recording after the propeller ⑤ speed becomes constant. The effective data sampling time should be no less than 60 seconds.

[0061] Turn on the shaft frequency electric field suppression device ①, continue to keep the test ship in the navigation state unchanged, and start recording after the output current of the shaft frequency electric field suppression device ① stabilizes. The effective data sampling time is not less than 60 seconds;

[0062] Immediately analyze and process the data obtained before and after the shaft frequency electric field suppression device ① is turned on;

[0063] The results show that when the propeller ⑤ rotates at 77 rpm, the rotation frequency of the shaft system ③ is 1.283 Hz, and the frequencies after frequency doubling are 2.566 Hz, 3.849 Hz, 5.132 Hz, 6.415 Hz, etc., respectively. The amplitude peaks of the frequency domain characteristics before and after the shaft frequency electric field suppression device ① is turned on are obtained by the ship's underwater shaft frequency electric field on-board in-situ monitoring device ④ under the shaft frequency fundamental frequency and its frequency doubling signal characteristics. Figure 9 As shown in the figure, it can be seen that the ship underwater shaft frequency electric field on-board in-situ monitoring device ④ meets the needs of in-situ monitoring of the shaft frequency electric field on board, and has high engineering application value.

Claims

1. A ship's underwater shaft frequency electric field on-board in-situ monitoring device, characterized in that: The main structure includes a hull connector arranged outside the hull, a conductive rod sealing box and a watertight mechanism arranged inside, and a sensor probe. A conductive rod is arranged at the center of the hull connector, and a ship-mounted in-situ fixed bracket is also arranged on the outside of the hull. The ship-mounted in-situ fixed bracket is made of a mesh glass fiber composite material and has an installation groove; the main structure of the sensor probe includes a probe body and a probe working surface arranged outside it, a sensor wire arranged on the top, and the sensor wire is connected to the conductive rod. A support boss with a cavity structure is provided at the center of the hull connector, and a wire groove is embedded in the lower surface. The conductive rod is arranged inside the support boss; the upper opening of the installation groove is a truncated cone-shaped clamping ring with a wide upper and narrow lower structure, and the lower opening is a cylindrical annular groove with an internal thread structure. The spacing between the center points of two adjacent installation grooves is 1 meter; the probe body is arranged inside the probe shell through a fixing tool with an internal and external thread structure, a sealing plug is provided on the top of the probe body, and a sealing ring is provided between the fixing tool and the clamping ring. The sensor wire passes through the sealing plug and is laid along the wire groove and welded to the conductive rod.

2. The device for monitoring underwater shaft frequency electric field of a ship according to claim 1, characterized in that: Sealing pads are provided between the hull connector and the hull and the onboard in-situ fixed bracket. The sensor probe is provided on the onboard in-situ fixed bracket and is provided with a sensor cover.

3. The device for monitoring underwater shaft frequency electric field of a ship according to claim 2, characterized in that: The hull connectors are made of a mesh fiberglass composite material.

4. A ship underwater shaft frequency electric field onboard in-situ monitoring device according to any one of claims 1 to 3, characterized in that: The standard error of the sensor probe is ≤0.1mV, and the self-noise is ≤5nV / , prepared by melt-pressing impregnation method, the preparation process is: First, the powdered electrode core material is heat-melted and die-cast with the mesh electrode cover to form the probe body; Then, the probe body is placed in a polar solution and repeatedly immersed in cooling until the surface of the mesh electrode cover forms the probe working surface; Finally, the probe body, sensor wire and sealing plug are cured and packaged.

5. The device for monitoring underwater shaft frequency electric field of a ship according to claim 3, characterized in that: The sensor cover is threadedly connected to the annular groove, and the sensor probe is located in the installation groove.

6. A ship underwater shaft frequency electric field onboard in-situ monitoring device according to claim 1 or 5, characterized in that: The main structure of the conductive rod sealing box includes a sealing box shell, a hull connector sealing ring, a conductive rod sealing gasket, a conductive rod sealing ring, a sealing box base, a sealing box plug and a sealing box compression nut; a sealing box shell is provided on the periphery of the end where the conductive rod enters the hull, and a hull connector sealing ring, a conductive rod sealing gasket and a conductive rod sealing ring are provided inside; a sealing box base is provided at the bottom of the sealing box shell, a sealing box plug is provided at the top, and the sealing box base is welded and installed to the hull.

7. The device for monitoring underwater shaft frequency electric field on board a ship according to claim 6, characterized in that: The main structure of the watertight mechanism includes a watertight mechanism shell, a watertight mechanism upper cover, a cable sealing box, a cable, a watertight mechanism fixing bolt, a cable clamping nut and a conductive rod nut assembly; a watertight mechanism upper cover is provided on the top of the watertight mechanism shell, and a cable sealing box is provided on the side, and the cable passes through the cable sealing box and is connected to the conductive rod; the watertight mechanism shell and the watertight mechanism upper cover are connected by watertight mechanism fixing bolts; the cable and the cable sealing box are connected and sealed by the cable clamping nut, and are connected to the conductive rod by the conductive rod nut assembly.

8. The device for monitoring underwater shaft frequency electric field of a ship according to claim 3 or 5, characterized in that: The probe shell is made of organic composite material, and a number of small holes are evenly opened on the surface.

9. A ship underwater shaft frequency electric field onboard in-situ monitoring device according to any one of claims 1 to 3, characterized in that: When in use: It is installed above the propeller-shaft of the ship and connected to the host computer through a cable. The host computer is an electric potential sampling device. The sampling frequency is set to ≥100Hz. The sensor probe captures the electric potential parameter change parameters of the hull surface above the ship's propeller-shaft at the shaft frequency in real time, and obtains characteristic data including the ship's underwater shaft frequency electric field fluctuations. Through real-time data processing, the electric potential fluctuations on the hull surface with the same frequency characteristics as the ship's propeller-shaft rotation are extracted, and the peak changes of the shaft frequency characteristic peaks before and after control are analyzed.

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