Liquid level safety system for immersed liquid hydrogen booster pump liquid pool

Abstract

The invention discloses a liquid level safety system for a liquid pool of an immersed liquid hydrogen booster pump, which comprises a guide rod vertically arranged in the liquid pool; the ultra-light floating body unit comprises a shell, the shell is connected with the guide rod in a matched and sleeved mode through a vertical penetrating hole in the middle, annular grooves are formed in the shell, and the shell is coaxially arranged on the outer side of the vertical penetrating hole at intervals; the annular permanent magnet is embedded in the annular groove, the inner diameter of the annular permanent magnet is matched with that of the annular groove, and the annular permanent magnet is attached to the inner ring surface of the annular groove and slides in the axial direction of the annular groove; the non-contact sensing unit is fixed on the outer wall of the liquid pool, is located at a set liquid level control threshold value and is used for detecting the relative position relation between the non-contact sensing unit and the annular permanent magnet; and a safety interlocking execution unit. The device adopts a non-contact measurement mode, and can work safely and reliably for a long time in a deep hypothermia environment, so that the liquid level of a liquid pool is effectively measured and controlled, a pump is actively prevented from idling, and high-reliability safety protection is provided for a liquid hydrogen system.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy and fuel cell vehicles. More specifically, this invention relates to a liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump. Background Technology

[0002] After being transported to a liquid hydrogen refueling station, liquid hydrogen typically undergoes compression using a liquid hydrogen booster pump. Submersible (i.e., liquid-filled) liquid hydrogen booster pumps are widely used in liquid hydrogen storage and transportation due to their rapid cold start, minimal heat leakage, and high volumetric efficiency. In a submersible liquid hydrogen booster pump, the pump body is completely immersed in the liquid hydrogen environment, directly drawing liquid hydrogen from the pool for subsequent compression. This pump design relies on liquid hydrogen for necessary cooling and lubrication. When the liquid level in the pool becomes too low due to consumption or vaporization, the pump inlet is exposed to the gas phase, causing the pump to run dry. Under dry conditions, the pump's piston, seals, and other moving parts lose lubrication and cooling medium, leading to a rapid temperature rise due to intense friction within a very short time. This results in rapid wear, jamming, and permanent equipment damage. More seriously, the high temperatures generated by friction in the pure hydrogen environment within the pump pool pose a significant ignition risk; if ignited, the consequences could be disastrous. Therefore, accurate and reliable monitoring and safe control of the liquid level in the pool are crucial.

[0003] In such applications of liquid level monitoring and control, technological development faces two major challenges: First, there are inherent safety challenges at the system level: traditional differential pressure, capacitive and other contact or invasive liquid level measurement methods usually require opening holes in the liquid hydrogen storage container (liquid pool) to install the corresponding measuring equipment, which creates a fatal leakage risk point in the system and does not meet the inherent safety requirements of the liquid hydrogen system. Secondly, there are challenges in environmental adaptability at the component level: During the measurement process, the measuring equipment installed in the liquid pool faces the test of extreme (deep cryogenic) environment. The equipment itself has a high risk of embrittlement failure. Moreover, due to the frequent and repeated changes in the liquid level of the pool, the detection accuracy and precision of the precision electronic components in the measuring equipment will be greatly affected under the huge temperature difference cycle from room temperature to -253℃.

[0004] To address the aforementioned issues, a liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump needs to be designed to ensure long-term, safe, and reliable operation of the system under cryogenic physical effects while maintaining accurate detection. Summary of the Invention

[0005] The purpose of this invention is to provide a liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump. It adopts a non-contact measurement method and can work safely and reliably for a long time in a deep cryogenic environment, thereby effectively measuring and controlling the liquid level in the pool, actively preventing the pump from running dry, and providing highly reliable safety protection for the liquid hydrogen system.

[0006] To achieve these objectives and other advantages according to the present invention, a liquid level safety system for a submersible liquid hydrogen booster pump pool is provided, comprising: A guide rod is vertically installed inside the liquid pool and fixedly connected to its top; The ultralight buoyancy unit has an overall effective density that is less than that of liquid hydrogen. The ultralight buoyancy unit includes a shell that is fitted with a guide rod through a vertical perforation in the middle and slides along its length. The shell has an annular groove inside, which is coaxially spaced outside the vertical perforation. An annular permanent magnet is embedded in the annular groove. The annular permanent magnet is adapted to the inner diameter of the annular groove. The annular permanent magnet is in contact with the inner annular surface of the annular groove and slides along its axial direction. A non-contact sensing unit is fixed on the outer wall of the liquid pool and located at a set liquid level control threshold. The non-contact sensing unit is configured to detect its relative positional relationship with the annular permanent magnet. The safety interlocking execution unit includes a controller, which is electrically connected to the non-contact sensing unit and the liquid hydrogen booster pump.

[0007] Preferably, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump includes a housing comprising two half-housing units symmetrically joined together to form a complete housing. Each half-housing unit includes an outer shell, which is a hollow structure with a single-sided opening; and a flat plate, which is fixedly closed to seal the opening of the outer shell and has an annular groove on its outer end face; wherein the outer end faces of the two flat plates are pressed together to form the annular groove.

[0008] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the ultralight buoyancy unit further includes an elastic element disposed at the axial gap between the annular permanent magnet and the annular groove. One end of the elastic element is fixedly connected to the annular groove, and the other end abuts against the annular permanent magnet and applies an axial preload to it.

[0009] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the outer diameter of the annular permanent magnet is smaller than the outer diameter of the annular groove.

[0010] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the housing is made of a low-temperature resistant polymer material.

[0011] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the annular permanent magnet is a samarium cobalt permanent magnet.

[0012] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the non-contact sensing unit includes at least two Hall sensors, which are spaced apart on the outer wall of the liquid pool along the height direction. The uppermost Hall sensor is located at a set warning liquid level height, and the lowermost Hall sensor is located at a set minimum safe liquid level height.

[0013] Preferably, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the length of the guide rod is greater than or equal to the set liquid level control range of the liquid pool, and a limiter is fixed at the bottom end of the guide rod, which is configured to limit the axial displacement of the housing on the guide rod. When the housing abuts against the limiter, the annular permanent magnet and the Hall sensor located at the bottom are on the same horizontal plane.

[0014] Preferably, the liquid level safety system for the liquid tank of the submersible liquid hydrogen booster pump further includes an emergency discharge valve, which is fixed to the upper part of the outer wall of the liquid tank and has an exhaust channel connecting the inner and outer sides of the liquid tank. The emergency discharge valve is electrically connected to the controller. An audible and visual alarm is also electrically connected to the controller.

[0015] Preferably, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump includes a controller comprising: a data acquisition module configured to read and store position data of the annular permanent magnet from the non-contact sensing unit and operating status data from the liquid hydrogen booster pump; a data analysis module configured to calculate the real-time liquid level and liquid level change rate of the pool based on the position data of the annular permanent magnet; an early warning module configured to issue graded early warnings for the real-time liquid level and liquid level change rate of the pool based on a set control threshold; and a safety interlock control module configured to control the operating status of the cryogenic emergency discharge valve, the audible and visual alarm, and the liquid hydrogen booster pump based on the early warning level of the early warning module and the operating status of the liquid hydrogen booster pump.

[0016] The present invention has at least the following beneficial effects: 1. The ultralight buoyancy unit of the present invention adopts an axially free and radially constrained structure for the internal permanent magnet. A functional compensation gap is reserved between the annular permanent magnet and the annular groove, which allows the shell and the permanent magnet to undergo stress-free relative displacement along the axial direction when experiencing huge temperature differences. This completely compensates for the shrinkage deformation caused by the huge difference in the coefficient of thermal expansion between the two, thereby completely eliminating destructive internal stress in the structure and effectively reducing the risk of component cracking or jamming. It fundamentally solves the technical problem of existing liquid level measuring devices causing structural damage or measurement failure due to material thermal mismatch stress in deep and low temperature environments, and ensures long-term, maintenance-free, and highly reliable operation of the system in deep and low temperature environments. 2. This invention adopts a non-contact measurement scheme. The sensing unit can be installed outside the liquid pool and cooperate with the permanent magnet inside the ultralight buoy unit to achieve real-time and accurate measurement of the liquid level. There is no need to puncture the liquid hydrogen storage container, eliminating the risk of leakage caused by sensor installation and realizing the inherent safety of the system. 3. The safety interlock execution unit of the present invention has a fast response speed. Once the liquid level reaches the set control threshold, the sensing unit can immediately trigger the safety interlock operation. Its response time depends only on the action time of the external electrical components, which can effectively prevent the occurrence of faults such as dry running and overheating of the booster pump, thereby extending the service life of the equipment. 4. This invention, through multiple functional modules of the controller, can realize multi-level early warning of dual parameters (real-time liquid level and liquid level change rate of the liquid pool) and intelligent control of safety interlock execution units, avoiding unnecessary emergency shutdowns and material discharges, ensuring equipment safety under extreme operating conditions, and at the same time helping to identify potential problems in the operation of the liquid hydrogen system in advance, thereby realizing predictive maintenance, with good economy and safety.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a liquid level safety system for a liquid pool of a submersible liquid hydrogen booster pump according to an embodiment of the present invention; Figure 2 This is a sectional elevation view of the upper half of the shell of the floating body unit described in the above embodiments; Figure 3 This is a sectional elevation view of the upper half of the shell of the floating body unit described in another embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Liquid hydrogen booster pump; 2. Liquid tank; 3. Ultralight buoyancy unit; 31. Shell; 311. Annular groove; 312. Outer shell; 313. Elastic element; 32. Guide rod; 33. Limiter; 4. Non-contact sensing unit; 41. Hall sensor; 42. Annular permanent magnet; 51. Controller; 52. Emergency discharge valve; 6. Audible and visual alarm. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0021] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] like Figure 1-3 As shown, the present invention provides a liquid level safety system for a liquid pool of a submersible liquid hydrogen booster pump, comprising: Guide rod 32, which is vertically installed inside liquid pool 2 and fixedly connected to its top; The ultralight buoyancy unit 3 has an overall effective density that is less than that of liquid hydrogen. The ultralight buoyancy unit 3 includes a shell 31, which is fitted with the guide rod 32 through a vertical perforation in the middle and slides along its length. The shell 31 has an annular groove inside, which is coaxially spaced outside the vertical perforation. An annular permanent magnet 42 is embedded in the annular groove. The annular permanent magnet 42 is adapted to the inner diameter of the annular groove. The annular permanent magnet is in contact with the inner annular surface of the annular groove and slides along its axial direction. The non-contact sensing unit 4 is fixed on the outer wall of the liquid pool and located at a set liquid level control threshold. The non-contact sensing unit is configured to detect its relative positional relationship with the annular permanent magnet. The safety interlocking execution unit includes a controller 51, which is electrically connected to the non-contact sensing unit 4 and the liquid hydrogen booster pump 1.

[0023] In the above technical solution, the ultralight buoyancy unit is an adaptive buoyancy unit that adopts a "stress decoupling" design. The radial displacement of the annular permanent magnet is constrained by the annular groove, but it can slide within the axial height range of the annular groove (the height of the annular permanent magnet is less than the height of the annular groove). That is, the axial displacement of the annular permanent magnet is designed to be non-rigidly fixed, allowing an axial compensation gap to be formed between the shell and the permanent magnet. The size of this gap is sufficient to compensate for the maximum differential shrinkage deformation caused by the difference in thermal expansion coefficients between the two in the temperature range from room temperature to deep cryogenic temperatures. Thus, through a functional internal compensation structure, the damage problem caused by "thermal mismatch stress" at deep cryogenic temperatures is fundamentally solved, ensuring the long-term physical reliability of the sensing front end in extreme environments. Specifically, the design value of the above-mentioned axial compensation gap (the height difference between the annular permanent magnet and the annular groove) must be greater than or equal to the maximum differential shrinkage deformation of the system across the entire temperature range. This deformation can be estimated by the following formula: , where α s α is the coefficient of thermal expansion of the shell. m Let be the coefficient of thermal expansion of the toroidal permanent magnet, and L be the axial height of the permanent magnet. This represents the maximum temperature difference.

[0024] In this embodiment, the external shape of the ultralight buoyancy unit (shell) can be flexibly designed into various forms, such as a sphere or a cylinder, based on factors such as hydrodynamic performance, internal space of the liquid pool, coordination of the guiding mechanism, and ease of processing. The vertical perforation is also coaxially arranged with the shell. To ensure that the overall effective density of the buoyancy unit is less than the density of liquid hydrogen, the shell is made of ultralight material resistant to ultra-low temperatures. A cavity can also be provided inside the shell at a position that does not affect the vertical perforation and annular groove, forming a hollow structure. This allows the shell to float on the surface of liquid hydrogen in the liquid pool under normal conditions and drive the annular permanent magnet to move up / down along the guide rod as the liquid level changes. The annular permanent magnet can be made of SmCo (samarium cobalt) or NdFeB (neodymium iron boron) material so that the non-contact sensing unit can sense its position signal. The position of the annular permanent magnet detected by the non-contact sensing unit represents the height of the ultralight buoyancy unit in the liquid pool, i.e., the liquid level. The overall effective density of the ultralight buoyancy unit must meet the following requirements: .

[0025] The controller can be a programmable logic controller (PLC). Its linkage logic is set to trigger the final safety interlock operation only when a signal indicating that the liquid level in the tank is below or equal to a set liquid level control threshold and a signal indicating that the booster pump is running are simultaneously detected. (For example, a forced shutdown signal is sent to the pump's motor control unit after the liquid level has been continuously detected below or equal to a set minimum safe liquid level height for a certain period of time). This avoids unnecessary safety interlock operations triggered by normal liquid level drops when the pump is already stopped. Thus, by logically associating the liquid level signal with the actual operating status signal of the pump, the interlock operation is executed only under truly dangerous conditions, achieving a balance between safety, reliability, and economical operation.

[0026] In another technical solution, the liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump includes a housing 31 comprising two half-housing units symmetrically joined to form a complete housing. Each half-housing unit includes an outer shell 312, which is a hollow structure with a single-sided opening; a flat plate, which fixes and closes the opening of the outer shell and has an annular groove 311 on its outer end face; wherein the outer end faces of the two flat plates are pressed together to form the annular groove.

[0027] When the shell is a sphere, such as Figure 2 As shown, the semi-shell is a hemisphere, and the flat plate is embedded in the corresponding opening surface of the hemisphere. That is, the flat plate does not protrude from the opening surface of the hemisphere; rather, the outer end face of the flat plate is flush with the opening surface of the hemisphere. Therefore, when the semi-shells are assembled, the two flat plates fit together and abut, and simultaneously, the opening ends of the two outer shells also fit together and seal to form a closed whole. Similarly, as... Figure 3 As shown, when the shell is cylindrical, the half-shell is a cylindrical segment broken vertically from the middle. The above two shell shapes are only two typical embodiments of shell shape selection. Other enclosed body shapes that can provide sufficient buoyancy, such as a spherical shape or a cylindrical shape with hemispherical ends, can also be used in shell design.

[0028] In practical applications, the split design facilitates the installation of the annular permanent magnet. Specifically, the annular permanent magnet is first inserted into the annular groove of one half-shell, and then the other half-shell is positioned and installed using the annular permanent magnet, allowing the two half-shells to be assembled together to form a complete shell. After assembly, the two half-shells can be fixedly connected by welding (such as ultrasonic welding) or bonding (such as special low-temperature resistant structural adhesive). Furthermore, each half-shell (outer shell, plate) has a vertical perforation in its center, allowing the complete vertical perforation formed after assembly to fit snugly onto the guide rod. The closed hollow structure formed by the outer shell and plate does not interfere with the vertical perforation. For the hollow structure of each half-shell, the cavity is pre-evacuated and then backfilled with approximately 0.1 MPa of helium to ensure that the overall apparent density of the shell is lower than that of liquid hydrogen, thus obtaining sufficient buoyancy. Helium is chosen because it remains gaseous at -253℃ liquid hydrogen temperature, preventing condensation that would affect buoyancy, and its small molecular size facilitates sealing testing.

[0029] The above technical solution designs the shell of the ultralight buoyancy unit as a sealed hollow structure. This structure allows the overall apparent density of the ultralight buoyancy unit (the ratio of its total mass to the volume enclosed by the outer layer) to be precisely designed to be lower than the density of liquid hydrogen, thereby obtaining sufficient buoyancy margin to respond to changes in liquid level. This solves the technical problem that the intrinsic density of conventional cryogenic materials (e.g., PEEK is about 1.3 g / cm³) is much higher than the density of liquid hydrogen (about 0.07 g / cm³).

[0030] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump further includes an elastic element 313 in the ultralight buoyancy unit 3, which is disposed at the axial gap between the annular permanent magnet 42 and the annular groove. One end of the elastic element 313 is fixedly connected to the annular groove, and the other end abuts against the annular permanent magnet 42 and applies an axial preload to it.

[0031] In the above technical solution, the design of the elastic element must meet the following requirements: at the lowest operating temperature, it can still provide sufficient preload to the annular permanent magnet to eliminate gaps and noise that may be caused by the vibration of the permanent magnet, and prevent the permanent magnet from being suspended or shaking in the groove; at the highest temperature, the compression of the elastic element is far from reaching its limit and is still within the elastic working range, which ensures that the permanent magnet always has room for thermal expansion and contraction and will not be rigidly squeezed due to the presence of the elastic element.

[0032] In this embodiment, the elastic element can be a non-magnetic, cryogenic wave spring, made of a non-magnetic material that maintains good elasticity at deep cryogenic temperatures, such as cryogenic stainless steel. The design and material selection of this elastic element fully consider the effects of cryogenic environments. The spring's dimensions and stiffness are precisely designed to ensure that the spring provides a continuous and gentle axial preload to the annular permanent magnet throughout the entire operating temperature range (from room temperature to liquid hydrogen temperature). This preload is sufficient to eliminate axial movement of the permanent magnet under vibration. Simultaneously, the spring's large-stroke elastic deformation capability still fully allows for the occurrence of the previously calculated maximum differential shrinkage deformation δ without being compacted or failing.

[0033] Adding an elastic element places higher demands on the design of the axial compensation gap (the height difference between the annular permanent magnet and the annular groove). Specifically, the design value of the axial compensation gap must not only be greater than δ, but also provide sufficient space for the installation and working stroke of the elastic element. This design perfectly achieves the dual purpose of eliminating vibration gaps and releasing thermal stress, and is the optimal implementation of this invention.

[0034] In another technical solution, in the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump, the outer diameter of the annular permanent magnet 42 is smaller than the outer diameter of the annular groove.

[0035] In the above technical solution, to ensure that the annular permanent magnet and the shell remain concentric at room temperature, the inner ring surface of the annular groove provides radial restraint for the annular permanent magnet. Furthermore, to eliminate the destructive radial stress caused by material thermal mismatch at deep cryogenic temperatures, a radial compensation gap is intentionally reserved between the outer ring surface of the annular permanent magnet and the outer ring surface of the annular groove. This gap is large enough to compensate for the greater radial contraction of the shell relative to the permanent magnet during the transition from room temperature to deep cryogenic temperatures, thus allowing the shell to contract freely without compressing the permanent magnet.

[0036] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump is provided, wherein the shell is made of a low-temperature resistant polymer material, such as PEEK (polyether ether ketone) or UHMW-PE (ultra-high molecular weight polyethylene).

[0037] The material is chosen because it maintains excellent mechanical toughness and does not become brittle at cryogenic temperatures of liquid hydrogen. At the same time, the material has extremely low saturated vapor pressure at cryogenic temperatures, so it will hardly release impurity molecules due to material sublimation, which can effectively avoid contamination of high-purity liquid hydrogen.

[0038] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump uses a samarium cobalt permanent magnet, which has a high Curie temperature and better magnetic performance stability and corrosion resistance than neodymium iron boron (NdFeB) magnets at low temperatures, and is less prone to low-temperature magnetic domain shifting.

[0039] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump includes a non-contact sensing unit 4 comprising at least two Hall sensors 41, which are spaced apart on the outer wall of the liquid pool 2 along the height direction. The uppermost Hall sensor is located at a set warning liquid level height, and the lowermost Hall sensor is located at a set minimum safe liquid level height.

[0040] The warning liquid level height corresponds to the first liquid level control threshold, the minimum safe liquid level height corresponds to the second liquid level control threshold, and other Hall sensors can be installed at the liquid level heights corresponding to other set liquid level control thresholds so that the controller can obtain sufficient liquid level data, which is beneficial to realize functions such as graded warning and early response.

[0041] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump has a guide rod 32 with a length greater than or equal to the set liquid pool level control range. A limiter 33 is fixed at the bottom end of the guide rod 32, which is configured to limit the axial displacement of the housing on the guide rod. When the housing abuts against the limiter, the annular permanent magnet and the Hall sensor located at the bottom are on the same horizontal plane, that is, the annular permanent magnet (ultra-light buoyancy unit) is located at the set minimum safe liquid level height. When the liquid level continues to drop, the annular permanent magnet can always be at the minimum safe liquid level height under the limiting action of the limiter, thereby continuously triggering the signal of the Hall sensor at the corresponding position to perform an alarm. It will not cause the ultra-light buoyancy unit to continue to sink and move away from the Hall sensor located at the bottom due to the drop in liquid level, thus preventing the alarm from failing.

[0042] The guide rod can be made of 316L stainless steel, Inconel alloy, or Monel alloy. The limiter can be a limit disc, which is fixedly sleeved on the guide rod. The limiter must be made of cryogenic material to avoid embrittlement and failure in liquid hydrogen (deep cryogenic) environment.

[0043] In another technical solution, the liquid level safety system for the liquid pool of the submersible liquid hydrogen booster pump further includes an emergency discharge valve 52, which is fixed on the upper part of the outer wall of the liquid pool 2 and has an exhaust channel connecting the inner and outer sides of the liquid pool. The emergency discharge valve 52 is electrically connected to the controller 51; and an audible and visual alarm 6 is electrically connected to the controller 51.

[0044] The emergency discharge valve is a conventional safety valve. When the sensing unit detects that the liquid level has dropped to the set minimum safe liquid level, it drives the emergency discharge valve to open the venting channel, thereby quickly reducing the pump pool pressure and terminating the dangerous operation to a safe state, avoiding frequent shutdowns of the booster pump that would affect work efficiency. The audible and visual alarm can be used to issue corresponding warning / alarm signals based on the degree of liquid level drop, reminding staff to promptly investigate / handle the fault.

[0045] In another technical solution, the liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump includes a controller comprising: a data acquisition module configured to read and store position data of the annular permanent magnet from the non-contact sensing unit and operating status data from the liquid hydrogen booster pump; a data analysis module configured to calculate the real-time liquid level and liquid level change rate of the pool based on the annular permanent magnet position data; an early warning module configured to issue graded early warnings for the real-time liquid level and liquid level change rate of the pool based on a set control threshold; and a safety interlock control module configured to control the operating status of the cryogenic emergency discharge valve, the audible and visual alarm, and the liquid hydrogen booster pump based on the early warning level of the early warning module and the operating status of the liquid hydrogen booster pump.

[0046] In the above technical solution, the controller monitors the height of the ultralight buoy unit inside the liquid tank in real time through a non-contact sensing unit installed on the outer wall of the liquid tank. This height reflects the change in the liquid level within the tank. Based on this, when the liquid level is detected to be below a preset threshold, a tiered early warning mechanism is triggered. Simultaneously, when the liquid hydrogen booster pump is detected to be running, a corresponding safety interlock operation is executed. Different liquid level thresholds trigger different levels of early warning signals, which in turn control the audible and visual alarms to issue corresponding levels of alarm information (e.g., a primary warning is triggered when the liquid level drops to the first control threshold, a medium warning when it drops to the second control threshold, and a high warning when the liquid level remains at the second control threshold for a set time). Medium and higher level warning signals can drive the emergency discharge valve connected to the liquid tank to open, and a high warning signal can send a forced shutdown signal to the pump's motor control unit. The safety interlock execution unit is also equipped with a display device, which is electrically connected to the controller and used to output detailed warning information from the early warning module for staff to query.

[0047] In this embodiment, the non-contact sensing unit includes at least two Hall sensors, which are spaced apart on the outer wall of the liquid pool along the height direction. The uppermost Hall sensor is located at the set warning liquid level height (first liquid level control threshold), and the lowermost Hall sensor is located at the set minimum safe liquid level height (second liquid level control threshold).

[0048] Specifically, when the liquid level drops to the first liquid level control threshold, the corresponding Hall sensor is triggered, the early warning module issues a low-level early warning signal, and controls the audible and visual alarm through the safety interlock control module to issue an early warning, prompting the operator to pay attention or replenish the liquid.

[0049] If the liquid level continues to drop to the second liquid level control threshold, the safety interlock control module receives an intermediate warning signal and immediately determines the pump's operating status. If the pump is running, it immediately executes the safety interlock command to drive the emergency discharge valve to open and release air. If the liquid level does not rise within the set time, the warning signal from the warning module changes to a high-level warning signal. After determining that the pump is running, the safety interlock control module sends a forced shutdown signal to the pump's motor control unit.

[0050] The above-mentioned working method can cut off the source of danger at the root and eliminate the dangerous consequences that have already occurred, thereby achieving the protection and safety of the pump.

[0051] In addition, the controller also has a predictive alarm function. The data analysis module continuously calculates the rate of liquid level decline through a built-in algorithm module. For example, the rate of liquid level decline is calculated by monitoring the time taken for the ring permanent magnet to move from the warning liquid level height position to the liquid level height corresponding to the next adjacent Hall sensor (not the minimum safe liquid level height).

[0052] The warning module has at least three preset rate thresholds: Normal evaporation rate (V1): The normal evaporation loss rate of the liquid pool when there is no consumption; Normal consumption rate (V2): The rate at which the liquid level drops when the pump is operating normally; Abnormal leakage rate (V3): Much greater than V2, indicating a possible pipeline leak or major malfunction.

[0053] Predictive alarms and interlocks: When the rate of drop in liquid level is between V1 and V2, the liquid hydrogen system is considered to be working normally. When the rate of liquid level drop remains higher than V2 but lower than V3 for an extended period, a high consumption warning message is issued through the early warning module, prompting a check of whether the downstream usage is normal.

[0054] When the rate of drop in liquid level instantaneously exceeds V3, even if the real-time liquid level in the pool is far higher than each liquid level control threshold, the PLC will immediately issue an advanced warning signal and an alarm message indicating a "suspected leak".

[0055] When the rate of change (descent) of the liquid level exceeds a preset rate threshold, even if the liquid level has not yet reached the first preset threshold, the PLC will issue a graded warning based on the degree to which the rate of change exceeds the preset threshold. This trend-prediction-based alarm mechanism can detect potential problems earlier than traditional fixed-point alarms, buying valuable processing time for operators and thus elevating the system from "fault response" to "predictive maintenance".

[0056] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A liquid level safety system for a submersible liquid hydrogen booster pump reservoir, characterized in that, include: A guide rod is vertically installed inside the liquid pool and fixedly connected to its top; The ultralight buoyancy unit has an overall effective density that is less than that of liquid hydrogen. The ultralight buoyancy unit includes a shell that is fitted with a guide rod through a vertical perforation in the middle and slides along its length. The shell has an annular groove inside, which is coaxially spaced outside the vertical perforation. An annular permanent magnet is embedded in the annular groove. The annular permanent magnet is adapted to the inner diameter of the annular groove. The annular permanent magnet is in contact with the inner annular surface of the annular groove and slides along its axial direction. A non-contact sensing unit is fixed on the outer wall of the liquid pool and located at a set liquid level control threshold. The non-contact sensing unit is configured to detect its relative positional relationship with the annular permanent magnet. The safety interlocking execution unit includes a controller, which is electrically connected to the non-contact sensing unit and the liquid hydrogen booster pump.

2. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The shell includes two half-shells, which are symmetrically joined to form a complete shell. Each half-shell includes an outer shell, which is a hollow structure with an opening on one side; a flat plate, which is fixed to close the opening of the outer shell and has an annular groove on its outer end face; wherein, the outer end faces of the two flat plates are pressed together to make the two annular grooves join together to form the annular groove.

3. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The ultralight buoyancy unit also includes an elastic element disposed at the axial gap between the annular permanent magnet and the annular groove. One end of the elastic element is fixedly connected to the annular groove, and the other end abuts against the annular permanent magnet and applies an axial preload to it.

4. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The outer diameter of the annular permanent magnet is smaller than the outer diameter of the annular groove.

5. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The shell is made of a low-temperature resistant polymer material.

6. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The ring-shaped permanent magnet is a samarium cobalt permanent magnet.

7. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The non-contact sensing unit includes at least two Hall sensors, which are spaced apart on the outer wall of the liquid pool along the height direction. The uppermost Hall sensor is located at the set warning liquid level height, and the lowermost Hall sensor is located at the set minimum safe liquid level height.

8. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 7, characterized in that, The length of the guide rod is greater than or equal to the set liquid level control range of the liquid pool. A limiter is fixed at the bottom of the guide rod, which is set to limit the axial displacement of the housing on the guide rod. When the housing abuts against the limiter, the annular permanent magnet and the Hall sensor located at the bottom are on the same horizontal plane.

9. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 1, characterized in that, The safety interlock execution unit also includes an emergency discharge valve, which is fixed to the upper part of the outer wall of the liquid tank and the exhaust channel connects the inner and outer sides of the liquid tank. The emergency discharge valve is electrically connected to the controller. An audible and visual alarm is electrically connected to the controller.

10. The liquid level safety system for the liquid pool of a submersible liquid hydrogen booster pump as described in claim 9, characterized in that, The controller includes a data acquisition module, configured to read and store position data of the annular permanent magnet from the non-contact sensing unit and operating status data of the liquid hydrogen booster pump; a data analysis module, configured to calculate the real-time liquid level and liquid level change rate of the liquid pool based on the annular permanent magnet position data; an early warning module, configured to issue graded early warnings for the real-time liquid level and liquid level change rate of the liquid pool based on a set control threshold; and a safety interlock control module, configured to control the operating status of the cryogenic emergency discharge valve, the audible and visual alarm, and the liquid hydrogen booster pump based on the early warning level of the early warning module and the operating status of the liquid hydrogen booster pump.

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