Bionic fish gill permeation oxygen supply honeycomb type pemfc stack

Abstract

The application discloses a bionic fish gill permeation oxygen supply honeycomb PEMFC stack, and relates to the field of fuel cells.The technical scheme of the application comprises an axially extending stack body, which comprises a center structure, a middle layer structure and an outer layer structure from the center to the outside; the center structure is used for supplying hydrogen to the anode side; the middle layer structure is arranged around the center hydrogen channel and comprises oxygen channels and seawater cooling channels arranged alternately in the circumferential direction; a membrane electrode layer is arranged on the wall surface adjacent to the oxygen channel of the center hydrogen channel; the outer layer structure comprises a plurality of clean seawater channels and a plurality of solid support skeletons; the outer side of the clean seawater channel is connected with a filter body in a communication mode. The underwater PEMFC stack structure can simultaneously consider seawater filtration, dissolved oxygen permeation supply, cooling channel arrangement, honeycomb pressure bearing support and membrane electrode reaction interface arrangement.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, and in particular to a biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack. Background Technology

[0002] Underwater robots (including autonomous underwater vehicles (AUVs), remotely operated underwater vehicles (ROVs), and long-duration underwater platforms) have broad application prospects in marine resource exploration, subsea pipeline inspection, underwater archaeology, and military reconnaissance. These devices place comprehensive demands on energy systems, requiring high specific energy, long endurance, low noise, and high reliability. Traditional energy storage devices such as lead-acid and lithium-ion batteries are limited by their energy density and self-discharge characteristics, making them unsuitable for long-term underwater operations. Internal combustion engine power systems suffer from high noise levels, exhaust emissions, and difficulties in underwater oxygen supply, thus limiting their application scenarios.

[0003] Proton exchange membrane fuel cells (PEMFCs) have significant advantages such as low operating temperature (60-80℃), high energy conversion efficiency (40%-60%), fast response speed, and low operating noise. Their theoretical specific energy is much higher than that of conventional batteries, making them one of the important candidate solutions for underwater robot power systems. However, the engineering application of existing underwater PEMFC systems still faces multiple technical bottlenecks.

[0004] First, there is the issue of cathode oxygen supply. PEMFC cathodes require a continuous supply of oxidant (oxygen or air) to maintain the electrochemical reaction. Existing underwater PEMFC systems typically require additional high-pressure oxygen cylinders, liquid oxygen devices, or chemical oxygen supply modules to provide oxidant to the cathode. High-pressure oxygen cylinders have limited storage density and pose an explosion risk; liquid oxygen devices require complex cryogenic maintenance systems, resulting in high energy consumption and unavoidable evaporation losses; chemical oxygen supply modules (such as chlorate oxygen candles) are disposable consumables, cannot be reused, and have difficult-to-precisely control oxygen supply rates. These external oxygen sources significantly increase the system's size, weight, and safety risks, while also severely limiting endurance and internal space layout, thus restricting the underwater robot's operating radius and mission duration.

[0005] Second, there is the structural pressure resistance issue in underwater high-pressure environments. Underwater external pressure increases dramatically with depth (approximately one atmosphere per 10 meters of descent). Traditional flat-plate PEMFC stacks employ a stacked flat-plate structure, resulting in a large sealing surface and weak pressure resistance. In the high static pressure environment underwater, this makes them prone to sealing failure, plate deformation, and flow channel collapse. To withstand external water pressure, the entire stack is typically housed in a pressure chamber, which further increases the system's size, weight, and complexity, reducing its payload ratio.

[0006] Third, there is the problem of complex thermal management pathways. The electrochemical reaction in PEMFCs is accompanied by significant exothermic reactions. If the heat cannot be dissipated in time, it will lead to an increase in membrane electrode temperature, dehydration of the proton exchange membrane, and even thermal runaway. Traditional fuel cell stacks rely on dedicated cooling plates or cooling channels, and the cooling medium (usually deionized water) requires an independent circulation system and heat exchanger, resulting in complex piping layouts and space consumption. Although underwater environments have abundant seawater cooling resources, current technologies have generally failed to integrate seawater cooling with the fuel cell stack structure in an efficient manner, resulting in long cooling paths, high thermal resistance, and poor temperature uniformity.

[0007] Fourth, there is the problem of insufficient system integration. In existing underwater PEMFC systems, the functions of oxygen supply, cooling, pressurization, and power generation are dispersed across different subsystems and structural components. These subsystems are connected via external pipelines and interfaces, resulting in a large overall size, redundant weight, and numerous potential failure points. This low integration is particularly problematic for underwater robotic hulls with extremely limited space, severely restricting the installed size and power density of the energy system. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a biomimetic fish gill-inspired honeycomb PEMFC stack. It provides an underwater PEMFC stack structure that simultaneously integrates seawater filtration, dissolved oxygen permeation supply, cooling channel arrangement, honeycomb pressure support, and membrane electrode reaction interface arrangement.

[0009] The technical solution adopted by the present invention to solve its technical problem is: a biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack, including a stack body extending along the axial direction, wherein the stack body includes a central structure, a middle layer structure and an outer layer structure in sequence from the axis outward;

[0010] The central structure is provided with a central hydrogen channel for supplying hydrogen to the anode side;

[0011] The middle layer structure is arranged around the central hydrogen channel, including oxygen channels and seawater cooling channels arranged alternately in the circumferential direction;

[0012] A membrane electrode layer is disposed on the wall surface adjacent to the central hydrogen channel and the oxygen channel, and the membrane electrode layer constitutes an electrochemical reaction interface.

[0013] The outer structure includes several clean seawater channels and several solid support frames, with the clean seawater channels and the solid support frames arranged alternately.

[0014] A filter body is connected to the outside of the clean seawater channel, and the outside seawater enters the clean seawater channel after being filtered by the filter body.

[0015] The clean seawater channel and the oxygen channel are separated by a selective oxygen-permeable wall. The selective oxygen-permeable wall is used to prevent liquid seawater and salt from entering the oxygen channel, while allowing dissolved oxygen in the seawater to permeate into the oxygen channel.

[0016] Fish gills selectively extract dissolved oxygen from water through gill filament membranes. This invention draws on this principle, utilizing a selectively oxygen-permeable wall to achieve "liquid-blocking and oxygen-permeable"—preventing the permeation of liquid seawater and salt while allowing dissolved oxygen molecules to diffuse across the wall into the oxygen channels. With the central hydrogen channel as the axis, reaction zones (middle layer) and supply / support zones (outer layer) are arranged outwards in a radially symmetrical flow field distribution, which is beneficial for uniform fluid distribution and pressure balance. Driven by the concentration gradient, dissolved oxygen in seawater diffuses through the selectively oxygen-permeable wall from the high-concentration clean seawater channels to the low-concentration oxygen channels, achieving passive oxygen supply without additional energy consumption.

[0017] It achieves integrated oxygen supply, cooling, pressurization and power generation, significantly improving the system's compactness and integration.

[0018] By directly utilizing dissolved oxygen in seawater to supply oxygen to the cathode, the reliance on external oxygen sources such as high-pressure oxygen cylinders and liquid oxygen devices is reduced or eliminated, saving system volume and weight, and improving the underwater robot's endurance and space utilization.

[0019] By arranging hydrogen, oxygen, and cooling medium in concentric layers from the axis outward, the reactant transport path is shortened, and the efficiency of electrochemical reaction is improved.

[0020] The solid support frame and clean seawater channels are arranged in an alternating manner, which not only ensures the seawater supply function but also enhances the overall pressure resistance and deformation resistance of the fuel cell stack, making it suitable for underwater high static pressure conditions.

[0021] Pre-filtration of the filter media can reduce the entry of particulate matter, suspended solids and marine biological impurities into the fuel cell stack, reduce the risk of contamination and blockage of the oxygen permeable walls and internal flow channels, and improve long-term operational stability.

[0022] Preferably, the membrane electrode layer comprises an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer arranged sequentially in a radial direction from the central hydrogen channel to the oxygen channel.

[0023] The anode gas diffusion layer (GDL) evenly distributes hydrogen to the anode catalyst layer; the Pt / C catalyst in the anode catalyst layer promotes the hydrogen oxidation reaction (HOR) to generate protons and electrons; the proton exchange membrane (such as the Nafion membrane) only allows the hydration transport of protons (H⁺) and blocks the transmembrane conduction of electrons and gases; the cathode catalyst layer promotes the oxygen reduction reaction (ORR); the cathode gas diffusion layer evenly distributes oxygen and collects electrons, while simultaneously expelling the water generated in the reaction.

[0024] Each functional layer is arranged radially from the inside out, allowing hydrogen to diffuse outward from the center and oxygen to diffuse inward from the outer layer. The reaction interface is located in the middle, and the reactants are transported towards each other under the drive of the concentration gradient, resulting in the shortest path.

[0025] The five-layer standard structure of the membrane electrode layer is clearly defined to ensure that the hydrogen oxidation and oxygen reduction reactions proceed efficiently in the anode and cathode catalyst layers, respectively. The gas diffusion layer provides a multifunctional channel for uniform distribution of reactant gases, electron conduction, and product water discharge. The proton exchange membrane enables selective proton transport and prevents direct mixing of hydrogen and oxygen, ensuring the safe operation of the fuel cell stack.

[0026] Preferably, the oxygen channel is filled with a metal foam structure.

[0027] It provides a three-dimensional porous mass transfer channel, significantly increasing the contact area between oxygen and the cathode gas diffusion layer, and improving the uniformity of oxygen distribution. The three-dimensional interconnected pore structure forms a tortuous flow channel, ensuring uniform oxygen distribution across the channel cross-section and avoiding uneven current density caused by local oxygen deficiency.

[0028] This enhances electron collection and conduction capabilities on the cathode side, reduces contact resistance, and improves current collection efficiency. The metal foam maintains close contact with the cathode side of the membrane electrode layer, providing numerous conductive contacts and forming a low-resistance current conduction network.

[0029] The high thermal conductivity of the metal framework enhances local heat transfer within the oxygen channels, helping to maintain a stable operating temperature for the membrane electrode. The specific surface area of ​​the metal foam is much larger than that of the smooth wall surface, enhancing convective and conductive heat transfer with the surrounding structure.

[0030] The capillary forces within the foam pores help draw cathodic generated water out of the catalyst layer, preventing a water film from covering the active sites. The porous structure promotes capillary drainage of product water, improves cathodic water management, and prevents flooding.

[0031] Preferably, the material of the metal foam structure is titanium foam, nickel foam, stainless steel foam, copper foam, or a metal foam with a corrosion-resistant conductive coating on its surface, and the porosity of the metal foam structure is 70% to 98%, and the pore size is 0.1 mm to 3 mm.

[0032] A dense TiO2 passivation film can form on the surface of titanium and titanium alloys, exhibiting excellent resistance to pitting and crevice corrosion in chloride-containing seawater. Stainless steel (such as 316L) contains Mo, which enhances its resistance to seawater corrosion. Nickel foam is resistant to alkaline environments. Conductive anti-corrosion layers (such as noble metal coatings or conductive ceramic coatings) are formed on the surface of the base metal foam through electroplating, chemical plating, or thermal spraying. These layers both prevent corrosive media from contacting the substrate and maintain electron conduction pathways. Porosity determines the effective mass transfer cross-sectional area and specific surface area, while pore size affects flow resistance and capillary force. A porosity of 70%-98% ensures sufficient mass transfer channels and reaction area, while a pore size of 0.1-3 mm ensures uniform oxygen dispersion across the channel cross-section while controlling pressure drop.

[0033] Preferably, the filter body includes at least one filter unit, which is a metal filter screen, a sintered porous material, a microporous membrane, a fiber filter layer, or a combination thereof.

[0034] Through a multi-layered filtration unit combination, gradient filtration from coarse to fine filtration is achieved, effectively trapping particulate matter, suspended solids, and biological impurities of different sizes. This protects the downstream selective oxygen-permeable wall from mechanical damage and biofouling, maintaining long-term stable oxygen permeability. Combinations of different filter materials can be optimized for different pollutant characteristics, improving filtration efficiency and service life.

[0035] Preferably, the selective oxygen-permeable wall comprises a porous support layer and an oxygen-permeable selective layer, wherein the oxygen-permeable selective layer is silicone rubber, polydimethylsiloxane, polytetrafluoroethylene modified layer, fluoropolymer layer, or other composite membrane layer capable of achieving liquid resistance and oxygen permeability.

[0036] The porous support layer provides mechanical support for the oxygen-permeable selective layer, preventing it from deforming, cracking, or detaching under seawater pressure differentials. The oxygen-permeable selective layer achieves a "liquid-blocking and oxygen-permeable" function, preventing seawater and salt from entering the oxygen channels while allowing dissolved oxygen to permeate. Materials such as silicone rubber and PDMS have high oxygen permeability coefficients and strong hydrophobicity, naturally possessing liquid-blocking and oxygen-permeable properties. The fluoropolymer layer exhibits excellent chemical corrosion resistance and low surface energy, making it resistant to degradation even after long-term immersion in seawater.

[0037] Preferably, the solid support frame is fixedly connected to the clean seawater channel and the seawater cooling channel, respectively.

[0038] The solid support frame is fixedly connected to the clean seawater channels and seawater cooling channels, forming a rigid frame network that effectively transfers the load-bearing capacity of the outer structure to the middle structure. This improves the overall structural rigidity and compressive strength of the fuel cell stack, enabling it to withstand the high static pressure environment underwater without significant deformation. The fixed connection prevents relative displacement between layers under water flow impact or pressure fluctuations, maintaining the stability of the flow channel geometry and ensuring uniform fluid distribution.

[0039] Preferably, the seawater cooling channel and the oxygen channel are alternately arranged circumferentially within the middle layer structure.

[0040] Seawater cooling channels and oxygen channels are arranged alternately along the circumference, ensuring that each oxygen channel is adjacent to at least one seawater cooling channel. This allows for the local removal of heat generated during the membrane electrode assembly (MEA) reaction. This shortens the heat transfer path, reduces the thermal resistance between the MEA and the cooling medium, and improves heat dissipation efficiency. The alternating circumferential arrangement also results in a more uniform temperature distribution, preventing localized hot spots that could lead to MEA performance degradation or proton exchange membrane dehydration. The proximity of the cooling channels to the oxygen channels also provides auxiliary cooling for the metal foam structure within the oxygen channels, maintaining a suitable operating temperature on the cathode side.

[0041] Preferably, the solid support frame is made of titanium and titanium alloys, stainless steel, graphite composite materials, or a metal material with a conductive and corrosion-resistant layer on its surface. This ensures that it possesses excellent mechanical and electrical properties simultaneously in a seawater corrosive environment.

[0042] Preferably, a turbine shroud is provided on the outside of the outer structure. The turbine shroud includes vortex blades and retaining rings. The two ends of each vortex blade are respectively fixed relative to each other by the retaining rings to form a cage-like rotating assembly. The two ends of the retaining rings are adapted to the outer structure by bearings.

[0043] The vortex blades passively rotate as the underwater robot moves, creating active disturbance to the water flow around the filter, breaking the static boundary layer and oxygen-depleted liquid film on the filter surface. This causes the surrounding oxygen-rich seawater to flow continuously and rapidly around the filter, maintaining the dissolved oxygen concentration gradient at the filter inlet and preventing oxygen deficiency in localized areas due to continuous oxygen consumption.

[0044] The disturbance of water flow generates shear force, inhibiting the adhesion and deposition of particulate matter, marine organisms, and microorganisms on the filter surface. This reduces biofouling and physical clogging of the filter layer, extending the maintenance cycle and service life of the filter.

[0045] Advantages of this invention:

[0046] This solution utilizes a biomimetic fish gill permeation oxygen supply mechanism, directly using dissolved oxygen in seawater as the cathode oxygen source, eliminating the need for high-pressure oxygen cylinders, significantly reducing system size and weight while improving endurance. It employs a concentric honeycomb layered structure from the axis outwards, integrating oxygen supply, cooling, pressure bearing, and power generation functions into a single unit, shortening reactant transport and heat transfer paths, and improving electrochemical reaction efficiency and temperature uniformity. The outer solid support skeleton and conductive, corrosion-resistant skeleton work together to enhance structural reliability in underwater high-pressure environments. The combination of selective oxygen-permeable walls and a pre-filter ensures long-term operational stability. Overall, this solution achieves high integration, high specific energy, low noise, and high environmental adaptability in the underwater PEMFC stack, making it suitable for long-endurance energy demand scenarios such as AUVs and underwater loitering platforms. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only five of the drawings in this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a cross-sectional schematic diagram of an embodiment of the present invention (without turbine circulation structure);

[0049] Figure 2 This is an exploded view of an embodiment of the present invention;

[0050] Figure 3 This is a perspective view of the turbine circulation structure according to an embodiment of the present invention;

[0051] Figure 4 A schematic diagram of the metal foam filling the oxygen channel according to an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the underwater robot energy system according to an embodiment of the present invention.

[0053] The components include: 1. Central hydrogen channel; 2. Oxygen channel; 3. Seawater cooling channel; 4. Membrane electrode layer; 5. Turbine shroud; 51. Vortex blades; 52. Retaining ring; 53. Bearing; 6. Clean seawater channel; 7. Solid support frame; 8. Filter body; 9. Selective oxygen permeable wall.

[0054] 100. Bionic fish gill permeation oxygen supply honeycomb PEMFC fuel cell stack;

[0055] 200. Hydrogen supply module; 201. High-pressure hydrogen cylinder; 202. Pressure reducing valve; 203. Hydrogen flow controller;

[0056] 300. Seawater supply and filtration module; 301. Seawater inlet; 302. Natural flow channel; 303. Active circulation pump; 304. Diverter valve;

[0057] 400. Power Management Module; 401. DC / DC Converter; 402. Power Distribution Unit; 403. Energy Storage Management Unit;

[0058] 500. Underwater robot payload module; 501. Thruster; 502. Sensor; 503. Controller; 504. Communication device; 505. Energy storage unit. Detailed Implementation

[0059] To enhance understanding of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. These embodiments are only used to explain the invention and do not limit the scope of protection of the invention.

[0060] Example 1: Bionic fish gill permeation oxygen supply honeycomb PEMFC fuel cell stack

[0061] like Figure 1 As shown, this embodiment provides a biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack, including a stack body extending along the axial direction. The stack body includes a central structure, a middle layer structure and an outer layer structure in sequence from the axis outward.

[0062] The central structure includes a central hydrogen channel 1, which is a hexagonal prism-shaped cavity structure that runs along the axial direction of the fuel cell stack and penetrates the entire fuel cell body to supply hydrogen to the anode side. The walls of the central hydrogen channel 1 are made of titanium alloy, which has both pressure-bearing and electrical conductivity functions.

[0063] The intermediate structure surrounds the central hydrogen channel 1 and includes oxygen channels 2 and seawater cooling channels 3 arranged alternately along the circumference. In this embodiment, the intermediate structure has a total of three oxygen channels 2 and three seawater cooling channels 3, all of which are hexagonal prism structures, evenly and alternately arranged along the circumference, corresponding to the six sides of the hexagonal prism structure of the central structure. The three oxygen channels 2 and three seawater cooling channels 3 are attached to each other. A membrane electrode layer 4 is disposed on the wall surface adjacent to the central hydrogen channel 1 and the oxygen channels 2, and the membrane electrode layer 4 constitutes an electrochemical reaction interface.

[0064] The membrane electrode layer 4 includes an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer arranged radially from the central hydrogen channel 1 to the oxygen channel 2. The anode and cathode gas diffusion layers are made of carbon paper, the anode and cathode catalyst layers are Pt / C catalyst coatings, and the proton exchange membrane is a perfluorosulfonic acid membrane (Nafion 212).

[0065] Combination Figure 4 As shown, the oxygen channel 2 is filled with a metal foam structure. The metal foam structure is made of titanium foam with a porosity of 85% and a pore size of 1.5 mm. The three-dimensional interconnected pore structure of the titanium foam provides a uniform distribution channel for oxygen and, as an auxiliary structure for cathode current collection, is in close contact with the cathode gas diffusion layer of the membrane electrode layer 4, reducing contact resistance.

[0066] The outer structure includes several clean seawater channels 6 and several solid support frames 7, which are arranged alternately. In this embodiment, the outer structure has a total of 9 clean seawater channels 6 and 3 solid support frames 7, all of which are hexagonal prism structures. Every group of 3 clean seawater channels 6 is arranged side by side, and the solid support frames 7 are positioned between the two groups of clean seawater channels 6. The solid support frames 7 are solid titanium alloy columns, which are fixedly connected to the outer walls of the clean seawater channels 6 and the outer walls of the seawater cooling channels 3 by laser welding to form a rigid load-bearing frame.

[0067] A filter body 8 is connected to the outside of the clean seawater channel 6. The filter body 8 includes three layers of filter units, which are arranged from the inside out as follows: a stainless steel metal filter screen (pore size 100 μm), a sintered titanium porous material (pore size 10 μm), and a polytetrafluoroethylene microporous membrane (pore size 0.2 μm), forming a gradient filtration structure.

[0068] The clean seawater channel 6 and the oxygen channel 2 are separated by a selective oxygen-permeable wall 9. The selective oxygen-permeable wall 9 includes a porous titanium support layer and a polydimethylsiloxane (PDMS) oxygen-permeable selective layer coated on its inner side. The PDMS layer is 200 μm thick and can prevent liquid seawater and salt from entering the oxygen channel 2, while allowing dissolved oxygen in the seawater to permeate into the oxygen channel 2 driven by the concentration gradient.

[0069] In the preferred embodiment, the clean seawater channel 6 and the seawater cooling channel 3 are each equipped with external water pumps, which can output the internal water to the outside when necessary, thereby accelerating the flow of the internal water.

[0070] The working principle is as follows:

[0071] Under external water pressure or pumping action, seawater first passes through a three-layer gradient filtration system (filter 8) to remove particulate matter, suspended solids, and biological impurities before entering the clean seawater channel (6). Driven by the concentration gradient, dissolved oxygen in the clean seawater permeates through the PDMS oxygen-permeable selective layer of the selective oxygen-permeable wall (9) into the oxygen channel (2). After being uniformly distributed within the titanium foam structure (5) of the oxygen channel (2), the oxygen reaches the cathode gas diffusion layer (4) of the membrane electrode layer (4) and then diffuses to the cathode catalytic layer to participate in the oxygen reduction reaction.

[0072] Meanwhile, the hydrogen supply module supplies hydrogen to the central hydrogen channel 1. The hydrogen diffuses through the anode gas diffusion layer to the anode catalyst layer, where a hydrogen oxidation reaction occurs to generate protons and electrons. The protons migrate through the proton exchange membrane to the cathode side, and the electrons, after doing work through the external circuit, reach the cathode catalyst layer, where they react with protons and oxygen to generate water and output electrical energy.

[0073] The heat generated during the reaction is promptly carried away by the cooling seawater in the seawater cooling channel 3, which is arranged alternately with the oxygen channel 2. The cooling seawater and the clean seawater share the same seawater source, and after being diverted, they enter the clean seawater channel 6 and the seawater cooling channel 3 respectively, maintaining the working temperature of the membrane electrode layer 4 within the range of 60-80℃.

[0074] Example 2: Turbine Circulation Structure

[0075] Combination Figure 2 and Figure 3 As shown, this embodiment, based on the biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack described in Embodiment 1, adds an outer hydrodynamic self-driven turbine shroud 5 to the outer layer structure. The turbine shroud 5 is coaxially sleeved on the outside of the stack body. The turbine shroud 5 includes vortex blades 51 and retaining rings 52. The two ends of each vortex blade 51 are respectively fixed relative to each other by the retaining rings 52, forming a cage-like rotating assembly. The two ends of the retaining rings 52 are adapted to the outer layer structure through bearings, allowing the turbine shroud 5 to rotate freely around the axis of the stack body. The overall shape of the cage-like rotating assembly is a spindle-shaped structure, thicker in the middle and thinner at both ends, to facilitate better contact with water during movement.

[0076] Vortex blades

[0077] The vortex blades 51 comprise 20-40 blades, evenly distributed circumferentially between the two retaining rings 52. Each vortex blade 51 has a twisted airfoil cross-section, with strip-shaped protrusions or grooves on its outer surface along the water flow direction. These protrusions or grooves have a height difference of 2-5 mm from the blade surface to enhance turbulence intensity and flow conversion efficiency. The helix angle is determined within the range of 15°-60° based on the speed and water depth conditions.

[0078] The blade material can be titanium alloy, stainless steel, engineering plastics, carbon fiber composites, or lightweight alloys with anti-corrosion coatings. In this embodiment, the blade is made of carbon fiber reinforced epoxy resin composite material with a density of approximately 1.6 g / cm³, which reduces rotational inertia while ensuring structural strength. The blade surface is coated with an organosilicon-based antifouling coating to inhibit the attachment of marine organisms and maintain long-term stable hydrodynamic performance. When the underwater robot moves forward or is affected by ocean currents, the water flow impacts the blades, generating a driving torque that drives the turbine fairing 5 to rotate.

[0079] Keep the circle

[0080] The retaining ring 52 includes a front retaining ring and a rear retaining ring, respectively disposed at both axial ends of the vortex blade 51. The retaining ring 52 is an annular frame structure with a rounded rectangular cross-section. Its outer diameter matches the tip position of the vortex blade 51, and its inner diameter fits with the outer ring of the bearing. The retaining ring 52 is made of the same material as the blade or is made of titanium alloy, and is fixed to the end of the vortex blade 51 by a combination of plug-in bonding and laser welding. The front end face (fronting face) of the front retaining ring is designed as a streamlined guide shield to reduce the incoming flow resistance and guide the water flow evenly into the flow channel between each vortex blade 51.

[0081] Bearing support

[0082] The bearing support portion is disposed between the retaining ring 52 and the internal solid support frame 7, and includes the bearing and a sealing structure. The bearing can be a roller bearing, ceramic bearing, polymer wear-resistant bearing, or a magnetically assisted support structure. In this embodiment, a double-row angular contact ceramic ball bearing is selected, with the inner ring and outer wall surface of the outer structure having an interference fit, and the outer ring and inner hole of the retaining ring 52 having a transition fit. Ceramic bearings are resistant to seawater corrosion, require no lubrication, and have a low coefficient of friction, making them suitable for long-term underwater operation.

[0083] The bearing is equipped with elastic sealing rings (such as fluororubber O-rings) and a seawater-resistant sealing coating on both sides, forming a combined sealing structure to prevent silt, salt particles, and biological impurities from entering the rotational gap, while allowing a small amount of seawater to enter the bearing gap for lubrication and cooling. The rated dynamic load of the bearing meets the centrifugal force and hydrodynamic load requirements of the turbine fairing 5 at maximum speed (8 knots) and corresponding water depth, and its design service life is not less than 5000 hours.

[0084] Assembly relationship with the internal solid support frame

[0085] The internal solid support frame 7 serves as the pressure-bearing main body, used to keep the filter body, outer structure, intermediate structure, and central structure relatively fixed. The turbine shroud 5 is fitted onto the outside of the external filter body, forming a rotating pair with the internal frame through a bearing support. This structure allows the outer converter components to rotate with low resistance, while the internal electrochemical reaction zone remains pressure-bearing, sealed, and operates stably.

[0086] When the underwater robot navigates or is acted upon by external ocean currents, the surrounding seawater forms an axial flow relative to the main body of the fuel cell stack. This flow impacts the spiral fluid channels and arc-shaped guide vanes on the surface of the turbine shroud 5, generating a circumferential driving torque that drives the turbine shroud 5 to rotate around the axis of the fuel cell stack. During this rotation, the turbine shroud 5 exerts the following three effects on the water flow surrounding the filter layer:

[0087] (1) Axial transport effect: The rotational motion of the spiral fluid channel forms a spiral propulsion flow in the channel, which transports the oxygen-rich seawater in front to the rear along the axis, continuously refreshing the water on the surface of the filter layer;

[0088] (2) Radial flow conversion effect: The twisted airfoil and turbulence structure of the vortex blade 51 generate radial velocity components near the surface of the filter layer, breaking the static boundary layer and causing the oxygen-depleted surface water to be drawn away and replaced by fresh oxygen-rich seawater from the surrounding area.

[0089] (3) Surface scouring effect: The turbulence and shear force generated by the rotation continuously scour the outer surface of the filter layer, inhibiting the attachment and deposition of particulate matter, silt and marine organisms, and reducing the risk of filter layer clogging and biofouling.

[0090] The synergistic effect of the above three factors reduces the concentration boundary layer on the outside of the oxygen-permeable wall, maintains the dissolved oxygen concentration at the inlet of the filter layer, and ensures that there is sufficient concentration gradient driving force on both sides of the selective oxygen-permeable wall, thereby improving the permeation oxygen supply rate and the stability of the stack output power.

[0091] Example 3: Underwater Robot Power System

[0092] like Figure 5 As shown, this embodiment provides an underwater robot energy system, including the biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack 100 described in Embodiment 1, as well as a hydrogen supply module 200, a seawater supply and filtration module 300, a power management module 400, and an underwater robot load module 500.

[0093] The hydrogen supply module 200 includes a high-pressure hydrogen cylinder 201, a pressure reducing valve 202, and a hydrogen flow controller 203. The high-pressure hydrogen cylinder 201 stores high-pressure hydrogen (35 MPa). After being reduced to 0.2-0.3 MPa by the pressure reducing valve 202, the flow rate is regulated by the hydrogen flow controller 203 and supplied to the anode side via a hydrogen supply pipeline 204 connected to the central hydrogen channel 1. The hydrogen flow rate is adjusted in real time according to changes in the underwater robot's load.

[0094] The seawater supply and filtration module 300 includes a seawater inlet 301, a natural flow channel 302, an active circulation pump 303, and a diversion valve 304. When the underwater robot is navigating, seawater is introduced through the natural flow channel 302 formed by its speed. When the underwater robot is stationary or navigating at low speed, the active circulation pump 303 is activated to enhance seawater flow. The seawater is divided into two paths by the diversion valve 304: one path enters the filter body 8 and the clean seawater channel 6 for oxygen supply; the other path enters the seawater cooling channel 3 for heat dissipation. The flow ratio of the two seawater paths is adjusted according to the fuel cell operating status and heat load.

[0095] The power management module 400 includes a DC / DC converter 401, a power distribution unit 402, and an energy storage management unit 403. The DC power output from the PEMFC stack 100 is regulated by the DC / DC converter 401 and then supplied to different loads by the power distribution unit 402 according to priority: the thrusters 501 prioritize mobility requirements; the sensors 502, controllers 503, and communication devices 504 ensure mission execution and remote control; excess power is charged and stored in the energy storage unit 505 by the energy storage management unit 403, and released during stack startup or peak load.

[0096] The underwater robot payload module 500 includes a thruster 501, a sensor 502, a controller 503, a communication device 504, and an energy storage unit 505. The controller 503 coordinates and controls hydrogen flow, seawater flow, and power distribution according to mission requirements and the operating status of the battery pack, achieving optimized operation of the energy system. The energy storage unit 505 is a lithium-ion battery pack.

[0097] The operation method includes the following steps:

[0098] S1: External seawater is introduced through the seawater supply and filtration module 300, filtered by the filter body 8, and then introduced into the clean seawater channel 6 of the outer structure.

[0099] S2: Allows dissolved oxygen from clean seawater to permeate through the selective oxygen-permeable wall 9 into the oxygen channel 2 of the middle layer structure;

[0100] S3: The hydrogen supply module 200 supplies hydrogen to the central hydrogen channel 1;

[0101] S4: The oxygen in the oxygen channel 2 is evenly distributed to the cathode side of the membrane electrode layer 4 through the metal foam structure, and the hydrogen is distributed to the anode side of the membrane electrode layer 4 through the central hydrogen channel 1. An electrochemical reaction occurs at the membrane electrode layer 4 and electrical energy is output.

[0102] S5: The cooling seawater in the seawater cooling channel 3 carries away the heat of reaction, thereby cooling the fuel cell stack;

[0103] S6: Discharge, collect, or recycle the water produced in the reaction along the axial direction;

[0104] S7: Based on changes in the underwater robot's load, the controller 503 adjusts the hydrogen supply flow rate, seawater flow rate, and cooling seawater flow rate to maintain stable and efficient operation of the fuel cell stack.

[0105] Example 4: Multi-cell series stack

[0106] In this embodiment, multiple single cells as described in Embodiment 1 are connected in series along the axial direction to form a stack structure. After multiple single cells are connected in series, the output voltage of the stack is the sum of the voltages of each single cell, which meets the higher power requirements of the underwater robot.

[0107] Example 5: Solid support framework with different material schemes

[0108] In this embodiment, the solid support frame 7 is made of graphite composite material. The graphite composite material is a composite of expanded graphite and epoxy resin, with a density of approximately 1.8 g / cm³, far lower than titanium alloy (4.5 g / cm³), which effectively reduces the overall weight of the fuel cell stack and improves the underwater robot's payload and maneuverability. The surface of the graphite composite material is treated with chemical nickel plating to form a conductive and corrosion-resistant layer, ensuring reliable electrical connections with surrounding structures and resistance to seawater corrosion.

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A biomimetic fish gill-inspired permeable oxygen supply honeycomb PEMFC fuel cell stack, characterized in that, The battery pack body extends along the axial direction and includes, from the axis outward, a central structure, a middle layer structure, and an outer layer structure. The central structure is provided with a central hydrogen channel for supplying hydrogen to the anode side; The middle layer structure is arranged around the central hydrogen channel, including oxygen channels and seawater cooling channels arranged alternately in the circumferential direction; A membrane electrode layer is disposed on the wall surface adjacent to the central hydrogen channel and the oxygen channel, and the membrane electrode layer constitutes an electrochemical reaction interface. The outer structure includes several clean seawater channels and several solid support frames, with the clean seawater channels and the solid support frames arranged alternately. A filter body is connected to the outside of the clean seawater channel, and the outside seawater enters the clean seawater channel after being filtered by the filter body. The clean seawater channel and the oxygen channel are separated by a selective oxygen-permeable wall. The selective oxygen-permeable wall is used to prevent liquid seawater and salt from entering the oxygen channel, while allowing dissolved oxygen in the seawater to permeate into the oxygen channel.

2. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The membrane electrode layer includes an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer arranged radially from the central hydrogen channel to the oxygen channel.

3. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The oxygen channel is filled with a metal foam structure.

4. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 3, characterized in that: The material of the metal foam structure is titanium foam, nickel foam, stainless steel foam, copper foam, or a metal foam with a corrosion-resistant conductive coating on its surface. The porosity of the metal foam structure is 70% to 98%, and the pore size is 0.1 mm to 3 mm.

5. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The filter body includes at least one filter unit, which is a metal filter screen, a sintered porous material, a microporous membrane, a fiber filter layer, or a combination thereof.

6. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The selective oxygen-permeable wall includes a porous support layer and an oxygen-permeable selective layer. The oxygen-permeable selective layer is made of silicone rubber, polydimethylsiloxane, polytetrafluoroethylene modified layer, fluoropolymer layer, or other composite membrane layer that can achieve liquid resistance and oxygen permeability.

7. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The solid support frame is fixedly connected to the clean seawater channel and the seawater cooling channel, respectively.

8. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The seawater cooling channel and the oxygen channel are alternately arranged circumferentially within the middle layer structure.

9. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The solid support frame is made of titanium and titanium alloys, stainless steel, graphite composite materials, or metal materials with a conductive and anti-corrosion layer on the surface.

10. The biomimetic fish gill permeation oxygen supply honeycomb PEMFC stack according to claim 1, characterized in that: The outer structure is provided with a turbine shroud, which includes vortex blades and retaining rings. The two ends of each vortex blade are respectively fixed relative to each other by the retaining rings to form a cage-like rotating assembly. The two ends of the retaining rings are adapted to the outer structure by bearings.

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