Onboard in-situ monitoring device for underwater shaft frequency electric field of ship

Abstract

The invention belongs to the technical field of ship underwater shaft frequency electric fields, and particularly relates to a ship underwater shaft frequency electric field on-board in-situ monitoring device which mainly structurally comprises a ship body connector and an on-board in-situ fixing bracket which are arranged outside a ship shell, and a conducting rod sealing box and a watertight mechanism which are arranged inside the ship shell. When the in-situ monitoring device is used, the in-situ monitoring device is connected with common high-frequency potential sampling equipment purchased on the market, and long-term effective in-situ real-time monitoring of the underwater shaft frequency electric field can be achieved. The tiny change and the signal characteristic rule of the electric field potential under the shaft frequency are mastered in time through in-situ monitoring; peak value changes of shaft frequency characteristic peaks before and after electric field control are extracted in real time through ship surface potential fluctuation with the same frequency characteristic as propeller-shaft rotation, the inhibition proportion of the ship shaft frequency electric field intensity is autonomously judged, and the shaft frequency electric field hiding effect is mastered, regulated and controlled in time; the potential parameters of the surface of the ship body above the paddle-shaft are captured in situ in real time through a 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 on-board 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 during 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: 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, and the frequency line spectrum characteristics are obvious, about 0.1-10Hz (related to the speed of the ship's propeller), and there are obvious frequency-multiplied signal characteristics, so it has the characteristics of long-distance propagation. Generally, the signal strength is in the order of μV. At the same time, the source of the underwater shaft frequency electric field of the ship is basically clear, and it has the characteristics of being detectable, measurable, and controllable. In the prior art, the detection of the underwater shaft frequency electric field of the ship is mainly obtained by indirect measurement by a third-party measurement ship through the electric field measurement array deployed in the test sea area, and the measured ship cannot immediately perceive the control effect of its own shaft frequency electric field. With the extension of the service time of the ship and the change of the service environment, the crew cannot adjust the working state of the electric field protection system in time, which may lead to the uncontrollable characteristics of the underwater shaft frequency electric field of the ship, 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 including four measuring electrodes and one 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 origin of the coordinates, a third electrode, a fourth electrode and a second electrode located in three orthogonal directions of the origin of the coordinates and capable of forming electric field measurement electrode pairs in corresponding directions with the first electrode respectively; one reference electrode includes a fifth electrode; the fifth electrode is a reference electrode, which is arranged close to 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 instrument 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. In a laboratory scaled seawater environment, the scaled model test driven by electrodes at a uniform speed confirmed the feasibility of the shaft frequency electric field measurement method. However, the laboratory environment is different from the actual engineering application, and it is uncertain whether it can be applied in the complex environment of the real sea and real ship. In addition, the electric field sensor measured by the three-axis measurement system is arranged in a three-dimensional space outside the ship model. When used, it needs to be calibrated with the remote reference electrode in the same space. In this measurement method, the dimensional state of the sensor measurement dimension and the dimensional state of the shaft frequency field source generation dimension are in relative motion. Therefore, this method cannot realize the in-situ measurement and self-perception function of the ship's underwater electric field when the shaft frequency electric field measurement point and the generation source are in a relatively static state.

[0005] Chinese patent 201910140651.3 discloses a ship tracking and positioning method based on shaft frequency electric field, which includes the following steps: S1) establish two or more ship shaft frequency electric field measurement nodes; S2) use the measurement nodes to measure the ship shaft frequency electric field signal in real time; S3) calculate the envelope of the measured shaft frequency electric field signal; S4) use the unit current source model to model the shaft frequency electric field envelope signal, and establish the observation model of Kalman filter; S5) use the Kalman filter method to estimate the state information of the ship according to the measured shaft frequency electric field envelope signal, so as to achieve the tracking and positioning of the ship. It establishes two or more ship shaft frequency electric field measurement nodes in the measurement sea area, obtains the shaft frequency electric field signal of the measured ship through the measurement array composed of the measurement nodes, performs real-time calculation and analysis on the measurement data, and tracks and locates the target ship.

[0006] Chinese Patent 202211189953.8 discloses a ship shaft frequency electric field detection system and method, comprising 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 detected ship signal 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, including 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, and the specific detection steps are: the first step, data entry: input the propeller speed range and shaft frequency electric field information corresponding to various ship types in the computing device; the second step, ship type detection: in the process of detecting the movement of the ship, use the electric field detection device to detect the surrounding electric field, analyze the ship type by comparing the detected shaft frequency electric field with the corresponding shaft frequency electric field of the ship recorded in the first step, and transmit the ship type information to the display system for display; the third step, ship angle detection: two electric field detection devices The device records the angle of the corresponding shaft frequency electric field transmission; the fourth step, position calculation: the computing device integrates the electric field propagation angle of the detected ship in the third step and the distance between the two electric field detection devices to calculate the direction of the detected ship and the distance between the detected ship and the detection ship at this time, so as to determine the position of the detected ship; the fifth step, secondary detection: the detection ship moves for 1s to 2s, and the position of the detected ship is continuously detected by the third and fourth steps. At the same time, the computing device calculates the moving speed of the detected ship according to the distance between the positions of the detected ship twice; the sixth step, position display: the computing device transmits the position signal and driving information of the detected ship to the display system, and the display system marks and displays the position and driving information of the detected ship. The two use two or more electric field detection devices to measure nodes, and adopt data entry, ship type detection, ship angle detection, position verification, secondary detection and position display steps to achieve the detection and positioning of target ships under the limitation 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 in which the monitoring sensors and the actual ship shaft frequency field source are relatively static has been proposed. There is a lack of effective means for ships to actively and instantly grasp the characteristic intensity of their own underwater shaft frequency electric field.

[0007] Chinese Patent No. 201710046480.9 discloses a ship shaft frequency electric field suppression device and a suppression method thereof, comprising a rectifier module, a power module and a control module, wherein 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; an amplifier circuit is provided on the signal processing board, and the amplifier circuit 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 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 are provided on the current control board; the current control board is connected to the power monitoring board, and the power monitoring board is connected to the power module. It collects the shaft shell current signal of the load from the outside of the ship, and after steps such as 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, and does not detect the results of electric field suppression. It lacks an evaluation method for the ship body to independently grasp the results of underwater shaft frequency electric field suppression. Therefore, the inventor has developed and designed a ship underwater shaft frequency electric field on-board in-situ monitoring device, which is convenient for relevant crew members to grasp their own underwater shaft frequency electric field strength at any time during the entire life of the ship, and to instantly judge the control effect of the ship's underwater shaft frequency electric field, and actively and timely grasp the underwater shaft frequency electric field strength of the ship, thereby enhancing safety and concealment and improving the vitality of the ship. Summary of the invention:

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and to develop and design an on-board on-board monitoring device for underwater shaft frequency electric field of a ship, which is directly installed and fixed on the ship. By real-time feedback of the changes in the frequency domain characteristics of the shaft frequency 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 outside 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, sealing gaskets are 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 a conductive rod is arranged in the center; the ship's in-situ fixing bracket is made of a mesh glass fiber composite material, and a mounting groove is opened; the main structure of the sensor probe includes a probe body and a probe working surface arranged outside it, and 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 a self-noise of

[0012] ≤5nV / Hz1 / 2(@1Hz), prepared by melt-pressing impregnation method, the preparation process is:

[0013] First, the powdered electrode core material is hot-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 immersed in cooling repeatedly 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] When the ship underwater shaft frequency electric field on-board in-situ monitoring device involved in the present invention is used: it is installed above the propeller-axis of the ship, connected to the host computer through a cable, the host computer is a commercially available conventional potential sampling device with a high sampling frequency, the sampling frequency is set to be ≥100Hz, the sensor probe in-situ real-time captures the potential parameter change parameters of the hull surface above the propeller-axis of the ship under the shaft frequency frequency, obtains the characteristic data containing the ship underwater shaft frequency electric field fluctuation, through the real-time data processing, extracts the hull surface potential fluctuation with the same frequency characteristics as the ship propeller-axis rotation, analyzes the peak value change of the shaft frequency characteristic peak before and after the control, so that the crew can grasp the control effect of the underwater shaft frequency electric field of the ship in time. 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 common high-frequency potential sampling equipment purchased on the market, which greatly reduces the threshold for use, and the crew can operate it after simple training; through in-situ monitoring, the slight changes of electric field potential at the shaft frequency and the signal characteristic law 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 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 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 static. Description of the drawings:

[0018] Figure 1 The 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 is shown in FIG.

[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 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 portion of the main structure of the present invention.

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

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

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

[0026] Fig. 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 is installed on board. Specific implementation method:

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

[0028] Embodiment 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, a ship-mounted in-situ fixing bracket 3, a sealing pad 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 ship-mounted in-situ fixing bracket 3 are sequentially arranged on the outside of the hull 1, and a sealing pad 4 is arranged between the hull connector 2 and the hull 1 and the ship-mounted in-situ fixing bracket 3, four sensor probes 5 are arranged on the ship-mounted in-situ fixing bracket 3 at equal intervals, the ship-mounted in-situ fixing bracket 3 is connected to the sensor probe 5 through 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 fixed bracket 3, the sealing gasket 4, the sensor probe 5, the sensor clamping bolts 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 involved in this embodiment is provided with a support boss 21 of a cylindrical cavity structure, four conductive rods 22 are provided inside the support boss 21, and a wire groove 23 is embedded in the lower surface of the hull connector 2;

[0032] Four installation grooves 31 are evenly spaced on the ship's in-situ fixing bracket 3. The upper opening of the installation 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, it includes a probe body 51, a fixing tool 52, a probe shell 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 shell 53 through the fixing tool 52 with an internal and external thread structure, the outer surface of the probe body 51 is provided with a probe working surface 54, the top is provided with a sensor wire 55 and a sealing plug 56, a sealing ring 57 is provided between the fixing tool 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, a wide upper portion and a narrow lower portion, and a middle cavity with threads, which is placed in the clamping ring 32 and is threadedly connected to the end of the fixing fixture 52;

[0035] The sensor cover plate 7 is threadedly connected to the annular groove 33, so that the sensor probe 5 is located in the installation groove 31, thereby preventing 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 arranged 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 arranged inside; a sealing box base 85 is arranged at the bottom of the sealing box shell 81, and a sealing box plug 86 is arranged 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 clamping nut 96 and a conductive rod nut assembly 97; a watertight mechanism upper cover 92 is arranged on the top of the watertight mechanism shell 91, and a cable sealing box 93 is arranged 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 clamping nut 96, and are connected to the conductive rod 22 by the conductive rod nut assembly 97.

[0038] The hull connector 2 involved in this embodiment has the characteristics of high strength, light weight, excellent rigidity, etc., and 10 through holes are opened on the edge so that the fixing studs can be penetrated to fix the hull connector 2 on the hull 1;

[0039] The ship's in-situ fixing bracket 3 is based on the toughness of the mesh glass fiber composite material itself, is easy to install and fix with the hull 1, and closely fits the streamlined design structure of the outer surface of the hull, thereby 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 organic composite material, and has a number of small holes evenly opened on the surface to facilitate the exchange of seawater medium. It is connected and fixed to the fixing fixture 52 by screwing, and protects the probe body 51 and the probe working surface 54;

[0042] The sealing box housing 81, the sealing box base 85, the watertight mechanism housing 91, the watertight mechanism upper cover 92, and the cable sealing box 93 are all made of ordinary low-carbon steel, and the conductive rod sealing gasket 83, the sealing box plug 86, the cable compression nut 96, and the 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 pad 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 through the cable 94.

[0045] Embodiment 2:

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

[0047] Use the spraying 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] The watertight mechanism 9 and the sealing box base 85 are welded to the inner surface of the hull 1, and the fixing studs are welded to the outer surface of the hull 1;

[0049] Fix the sensor probe 5 on the ship's in-situ fixing bracket 3 through the sensor clamping bolt 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] A layer of sealant is applied on both sides of the upper sealing pad 4 to cover the upper surface of the packaged hull connector 2, and a layer of sealant is applied on both sides of the lower sealing pad 4 to install the bracket 4, the lower sealing pad 4, and the hull connector 2 from bottom to top in the order of the ship's in-situ fixing bracket 4, the lower sealing pad 4, and the hull connector 2;

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

[0053] Install the hull connector sealing ring 82, the conductive rod sealing gasket 83, the conductive rod sealing ring 84, and the 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] Embodiment 3:

[0056] The actual measurement process of the ship underwater shaft frequency electric field on-board 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 part of the cabin of the test ship. The entire test ship is a steel hull ②, the shaft system ③ is coated with non-metallic materials to make it electrically insulated from seawater, and the propeller ⑤ is made of aluminum bronze;

[0058] Install the ship underwater shaft frequency electric field on-board in-situ monitoring device④ in the midship of the test ship, with the 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 be no less than 100 Hz, the total cathodic protection current to 5 A, the propeller ⑤ speed to 77 rpm, and make the test ship 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 shall 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 shall not be 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 speed of the propeller ⑤ is 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. 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, as shown in Figure 2. Fig. 9 As shown, it can be seen that the ship underwater shaft frequency electric field on-board in-situ monitoring device ④ meets the needs of on-board in-situ monitoring of the shaft frequency electric field and has a high engineering application value.

Claims

1. A ship 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.

2. The device for monitoring underwater shaft frequency electric field of a ship according to claim 1, characterized in that: A shipboard in-situ fixing bracket is also arranged outside the hull, and sealing pads are arranged between the hull connector and the hull and the shipboard in-situ fixing bracket. The sensor probe is arranged on the shipboard in-situ fixing bracket and has 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 connector is made of a mesh glass fiber composite material with a conductive rod in the center; the on-board fixed bracket is made of a mesh glass fiber composite material with a mounting groove; the main structure of the sensor probe includes a probe body and a probe working surface arranged outside the probe, a sensor wire arranged on the top, and the sensor wire is connected to the conductive rod.

4. A ship underwater shaft frequency electric field on-board in-situ monitoring device according to any one of claims 1 to 3, characterized in that: The standard error of the sensor probe accuracy is ≤ 0.1mV, self-noise ≤5nV / Hz1 / 2, prepared by melt-pressing and 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 immersed in it repeatedly for cooling until the surface of the mesh electrode cover forms a 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: A support boss with a cavity structure is arranged at the center of the hull connector, a wire groove is embedded in the lower surface, and a 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 distance between the center points of two adjacent installation grooves is 1 meter; The probe body is arranged inside the probe housing through a fixing fixture having an internal and external thread structure, a sealing plug is arranged on the top of the probe body, a sealing ring is arranged between the fixing fixture 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; 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 on-board 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 arranged 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 arranged inside; a sealing box base is arranged at the bottom of the sealing box shell, a sealing box plug is arranged 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 of 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 arranged on the top of the watertight mechanism shell, a cable sealing box is arranged 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 the 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 an organic composite material, and a plurality of small holes are evenly opened on the surface.

9. A ship underwater shaft frequency electric field on-board 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-axis of the ship and connected to the host computer through a cable. The host computer is a potential sampling device. The sampling frequency is set to ≥100Hz. The sensor probe captures the potential parameter change parameters of the hull surface above the propeller-axis of the ship at the shaft frequency in real time, and obtains characteristic data including the underwater shaft frequency electric field fluctuations of the ship. Through real-time data processing, the hull surface potential fluctuations with the same frequency characteristics as the propeller-axis rotation of the ship are extracted, and the peak changes of the shaft frequency characteristic peaks before and after control are analyzed.

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