Deepwater aeration and gas circulation synergistic interaction method for layered water body

Abstract

The invention discloses a layered water body deepwater aeration and gas circulation synergistic interaction system and method, and relates to the technical field of water environment in-situ ecological restoration. The system is based on a coaxial sleeve structure, an outer-layer flow channel drives a deep-layer water body to lift by utilizing an airlift effect generated by compressed air, and an inner-layer flow channel is used for reinjecting an oxygen-enriched water body to a deep water layer. An inverted bell-jar-shaped gas-liquid separation cabin is arranged at the top of the device, bubble separation is achieved by means of flow velocity attenuation and the Stokes sedimentation principle, and a gas cavity with pressure potential energy is formed through accumulation. A spiral guide vane is arranged at an inlet of the inner pipe, downward water flow is converted into strong rotational flow, a Rankine vortex negative pressure area is constructed, and gas accumulated on the top is passively sucked into a downward flow channel through the pressure difference between a gas cavity and a vortex core. Through gradient utilization of fluid energy and active fine control of a flow state, the oxygen mass transfer efficiency is remarkably improved without additional energy consumption, a natural thermal stratification structure of a water body is strictly maintained, and resuspension of bottom mud is prevented.

Description

Technical Field

[0001] This invention relates to the field of in-situ ecological restoration technology for water environments, specifically a method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies. Background Technology

[0002] During seasonal thermostratification, deep-water reservoirs and lakes often experience severe oxygen depletion or even anaerobic conditions in the deep water layer (below the thermocline) due to the oxygen consumption caused by the decomposition of organic matter and the lack of atmospheric reoxygenation mechanisms. This anaerobic environment can induce the release of endogenous pollutants such as iron, manganese, phosphorus, and sulfides from the sediment, seriously threatening water supply security and the health of the aquatic ecosystem. Deep-water aeration technology, as an effective means of replenishing dissolved oxygen in deep water layers without disrupting the thermostratification structure, has been widely used in water quality improvement projects.

[0003] Existing deep-water aeration technologies mostly employ pumped aeration tubes or airlift circulation devices. Their core principle is to use compressed air to reduce the fluid density within the aeration tube, thereby generating buoyancy to drive water circulation. However, these technologies suffer from significant bottlenecks in gas-liquid mass transfer efficiency and energy utilization deficiencies in practical applications. Specifically, in traditional devices, the compressed air injected has limited contact time with the water during its ascent. Furthermore, due to the large bubble size and small specific surface area, a large amount of undissolved oxygen rises with the water flow to the top and then directly escapes into the atmosphere, resulting in a significant waste of air source energy. Although some existing technologies attempt to recover exhaust gas through return pipes, this often requires additional pressurization equipment or relies on a large hydraulic elevation difference to overcome two-phase flow resistance. This not only increases system complexity and maintenance costs but also introduces additional energy consumption, making it difficult to achieve truly low-energy self-sustaining circulation.

[0004] Furthermore, to improve oxygen transfer efficiency, existing technologies typically rely on microporous aerators to generate microbubbles or underwater mechanical mixers for mixing. However, in deep-water eutrophic environments, microporous materials are easily clogged by biofilms or mineral deposits, leading to increased back pressure and energy consumption. Underwater mechanical mixers, on the other hand, involve complex underwater power supply and sealing issues, resulting in high maintenance difficulty and a high failure rate. More importantly, traditional devices offer relatively crude control over fluid flow patterns, lacking active intervention mechanisms for bubble breakup, making it difficult to obtain high-density microbubble clusters under low-energy conditions. Simultaneously, in pursuit of better mixing, some devices are designed with excessively high outlet velocities. High-energy jets can easily disrupt the natural thermal stratification of the water body, even scouring bottom sediments and causing resuspension of pollutants, which contradicts the goal of "preserving the stratum and preventing disturbance" in deep-water in-situ remediation.

[0005] In summary, how to achieve efficient recovery and utilization of undissolved gases without the need for external power, enhance bubble breakup and mass transfer processes through pure fluid dynamics, and strictly limit the outflow state to protect the water stratification structure are the key technical challenges that urgently need to be solved in the field of deep-water aeration technology. Summary of the Invention

[0006] The present invention aims to solve the technical problems of low oxygen utilization, short bubble residence time and easy destruction of the natural stratification structure of water in existing deep-water aeration technology.

[0007] The first aspect of the present invention provides a method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies.

[0008] This method, based on a coaxial dual-channel circulation system, reconstructs the traditional unidirectional aeration process into a closed-loop circulation process involving gas-liquid separation, vortex self-absorption, pulse modulation, and resonant shearing through fluid dynamics design. The method includes the following steps:

[0009] First, a coaxial dual-channel circulation device is deployed below the thermocline of the stratified water body. This device includes an outer rising channel, an inner descending channel, and a gas-liquid separation and gas collection chamber located at the top.

[0010] Secondly, gas is injected into the outer rising channel to generate a gas lift effect by utilizing the density difference of the gas-liquid mixture, which drives the bottom water to flow upward and undergo primary dissolution.

[0011] Next, after the mixed fluid reaches the top, it undergoes gas-liquid separation in the gas-liquid separation chamber. The separated undissolved gas accumulates to form a high-pressure gas chamber, while the degassed water flows into the inner downflow channel.

[0012] Subsequently, the water in the inner downflow channel forms a vortex, creating a negative pressure zone in the center of the channel. The pressure difference is used to draw the gas in the high-pressure gas chamber into the center of the vortex, achieving closed-loop gas recovery.

[0013] Then, the mixed swirling flow of the inhaled gas passes through the flow-induced vibration coupled pulse modulation component, which uses the fluid-structure interaction effect to induce periodic vibrations, modulating the continuous flow state into a pulsed flow state.

[0014] Finally, the pulsed flow fluid impact shearing component breaks up bubbles and reconstructs the interface, and then the oxygen-rich water is released back to the bottom of the water body in a laminar flow.

[0015] As a further improvement to the first aspect of the present invention, the method employs a coupling mechanism of gas phase pressure potential energy accumulation and vortex-induced self-absorption.

[0016] Specifically, in the gas-liquid separation stage, gravity separation is achieved by reducing the flow velocity and using baffles. Undissolved gas accumulates at the top of the inverted bell-shaped jar, establishing gas phase pressure potential energy. A spiral guide structure is installed at the inlet of the inner downflow channel, where the vertical velocity component of the water is converted into a tangential velocity component as it flows through, forming a Rankine vortex structure where the central pressure is lower than the outer pressure.

[0017] This invention triggers self-priming under specific hydrodynamic conditions, namely, requiring a high pressure in the high-pressure air chamber. Pressure at the center of the vortex For fluid dynamic equilibrium to be satisfied, the critical intake condition is expressed as follows: ; in, This represents the friction loss along the gas flow path. The low pressure at the center of the vortex is established through Bernoulli's principle, which forces the gas to be entrained into the liquid phase flow field.

[0018] As a key improvement of the first aspect of the present invention, the method introduces a flow-induced vibration coupled pulse modulation mechanism.

[0019] A flexible bistable oscillating ring is installed at the throat of the downward flow channel of the meat layer. When the high-speed swirling flow passes through this component, the hydrodynamic pressure forces the flexible material to undergo high-frequency self-excited switching between an expansion steady state and a contraction steady state. The periodic contraction and expansion of the flexible bistable oscillating ring mechanically chops the continuously inhaled gas-liquid mixture, cutting the continuous gas column into discrete pulsed gas clusters.

[0020] The frequency of the pulse modulation It exhibits flow velocity adaptive characteristics and follows the following fluid-structure interaction relationship: ; in, For Strauhal numbers, The average velocity of the fluid flowing through the throat. This is the characteristic hydraulic diameter of the oscillating ring. As the air intake increases, the flow rate... When the frequency increases, the vibration frequency The automatic elevation increases the frequency of gas mass cutting, ensuring uniform gas-liquid mixing at high flow rates.

[0021] As a further improvement to the first aspect of the present invention, the method employs a multi-level resonant shearing and interface reconstruction mechanism.

[0022] Pulse-modulated fluid impacts a downstream multi-stage fractal shear grid. The pulse frequency of the pulsed flow is configured to be close to the natural frequency of the multi-stage fractal shear grid, inducing micro-amplitude resonance in the grid. The grid structure, in a vibrating state, actively impacts the pulsed air mass, achieving forced bubble breakage.

[0023] In this process, the efficiency of interface reconstruction depends on the Weber number of bubble bursting. The unsteady flow characteristics introduced by pulsed flow significantly increase the turbulent fluctuation velocity, causing the Weber number to satisfy the following relationship:

[0024] ; in, For the density of the liquid, The turbulent pulsation velocity induced by the pulse. The diameter of the bubble. Surface tension coefficient This is the critical Weber number for bubble breakup. This mechanism promotes the breakup of large bubbles into micron-sized bubbles and inhibits secondary coalescence of microbubbles under the action of pulsed turbulent kinetic energy.

[0025] As a further improvement to the first aspect of the present invention, the method employs a laminar flow release control mechanism.

[0026] Oxygen-rich water is released through a radially attached laminar flow disk at the bottom. This structure converts vertical momentum into horizontal momentum and reduces flow velocity through diffusion. To prevent disruption of the thermocline and resuspension of sediments, the outlet flow pattern is controlled at a low Froude number. Density flow:

[0027] ; in, For export flow rate, To calculate gravitational acceleration, The thickness of the fluid layer.

[0028] A second aspect of the present invention provides a deep-water aeration system based on energy cascade conversion.

[0029] This system achieves efficient energy conversion and utilization through structural design: the outer rising channel converts the buoyant potential energy of the gas into the lifting potential and kinetic energy of the water; the inner descending channel converts the potential energy of the water into swirling kinetic energy for gas intake; and the flow-induced vibration coupled pulse modulation component converts some of the fluid kinetic energy into mechanical vibration energy for bubble breakage and interface renewal. This energy cascade utilization mode achieves a fully closed-loop gas circulation and efficient mass transfer without introducing additional external energy.

[0030] This invention provides a method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies. It offers the following beneficial effects:

[0031] 1. This invention innovatively utilizes the device's own coaxial structure and fluid kinetic energy conversion mechanism to achieve internal recovery of undissolved gas without the need for any external pressurization equipment or electric drive. The top inverted bell-shaped structure accumulates undissolved gas to establish gas phase pressure potential energy, which, combined with the strong swirling Rankine vortex negative pressure generated by the inner tube's spiral flow, creates a stable self-absorption pressure difference between the gas chamber and the throat. This ingenious fluid loop design allows approximately 25% of the injected gas volume to be automatically drawn back, significantly reducing energy waste caused by exhaust gas escape and increasing gas-liquid contact time and oxygen dissolution opportunities, thus achieving the cascade utilization of fluid energy.

[0032] 2. To address the issues of easy clogging and high resistance in microporous aerators in deep-water environments, this invention abandons microporous materials and instead employs large-aperture channels combined with fluid dynamics modulation components. Utilizing the fluid-structure interaction effect of a flexible bistable oscillating ring at a specific Reynolds number, high-frequency self-excited vibration is induced, actively modulating the originally continuous gas-liquid two-phase flow into a pulsed slug flow with a high momentum gradient. This dynamic modulation mechanism not only fundamentally eliminates the risk of microporous clogging and ensures the long-term stable operation of the system, but also provides a crucial kinetic basis for subsequent bubble breakage due to the unsteady fluctuation energy inherent in the pulsed flow itself.

[0033] 3. This invention enhances the bubble breakup process through the synergistic effect of a multi-stage fractal shear grid and upstream pulsed flow, utilizing the principle of fluid resonance. When the pulsed air mass impacts the grid blades with fractal geometry, the natural frequency of the fluid structure couples with the pulse frequency, inducing strong local turbulence and cavitation effects, causing the bubble Weber number to far exceed the critical breakup threshold. This purely hydrodynamic shearing method can efficiently break millimeter-sized large bubbles into micron-sized bubble clusters within an extremely short mixing distance, significantly increasing the gas-liquid mass transfer surface area and greatly improving the oxygen transfer coefficient in deep-water environments without increasing additional mechanical energy consumption.

[0034] 4. Given the stringent requirements for "layer preservation" in deep-water remediation, this invention incorporates a special radial laminar flow release component at the bottom of the device. Upon reaching the bottom, the oxygen-rich water, enhanced by the inner pipe, efficiently dissipates its vertical kinetic energy through the diffusion effect of the laminar flow disk, converting it into horizontal pressure potential energy. This energy then diffuses smoothly along the horizontal plane as a low-Froude number density flow. This design strictly limits the outlet flow velocity, eliminates vertical disturbance components, avoids damage to the overlying thermocline, and prevents resuspension of bottom sediments, ensuring environmental safety during the remediation process.

[0035] 5. Apart from the shore-based air compressor, the entire underwater system contains no electric components, rotating machinery, or consumable parts. All fluid modulation, gas circulation, and bubble breaking functions rely on the physical effects generated when water flows through specific geometric structures (spiral blades, oscillating rings, and fractal grids). This "static equipment, dynamic fluid" design concept enables the device to adapt to the harsh environment of deep water with high pressure, corrosion, and biofouling, greatly reducing the failure rate and maintenance costs. It is particularly suitable for in-situ remediation projects of deep-water reservoirs that require long-term unattended operation. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall application scenario of the synergistic enhancement system of deep-water aeration and gas circulation in stratified water bodies according to the present invention. Figure 2 This is a second schematic diagram of the method flow of the present invention; Figure 3 This is a partially enlarged cross-sectional schematic diagram of the top gas-liquid separation and gas collection chamber and the vortex-induced self-absorption structure in an embodiment of the present invention. Detailed Implementation

[0037] See attached document Figures 1 to 3 , Figure 1 This is a schematic diagram of the overall structure of a synergistic enhancement system for deep-water aeration and gas circulation in stratified water bodies according to an embodiment of the present invention; see attached diagram. Figure 2 , Figure 2 This is a partial cross-sectional structural diagram of the flow-induced vibration coupled pulse modulation component, a core component of this invention. This invention provides a deep-water in-situ treatment system capable of achieving closed-loop gas-liquid circulation, recovering exhaust gas without external power, and actively reconstructing the gas-liquid interface.

[0038] The system adopts a coaxial dual-channel topology in its overall layout, with the main body vertically deployed at the thermocline depth of the target water body. The outer layer of the device consists of a cylindrical tube made of rigid material forming an upward flow channel, with a microporous aerator or jet generator at its bottom serving as the system's initial power source. The inner layer contains a coaxially nested downward flow channel, and the annular space between them constitutes the upward flow channel. The bottom of this structure extends to the bottom of the water body, and the top connects to the gas-liquid separation and gas collection chamber.

[0039] See attached document Figure 1 The gas-liquid separation and collection chamber at the top of the device has an inverted bell-shaped structure. The diameter of this chamber is larger than that of the rising flow channel to ensure that the flow velocity of the fluid is significantly reduced after entering this area. Inside the chamber, there are baffles to prevent bubbles from being directly diverted into the downward flow channel by the water flow, forcing undissolved free gas to accumulate upwards under the action of buoyancy.

[0040] This structural design allows the separated gas to form a stable gas cap at the top of the bell jar. The pressure within the gas cap... It is not constant, but is determined by both the hydrostatic pressure at that depth and the overpressure of the gas accumulated in the air cavity. The physical relationship can be expressed as follows:

[0041] in, Atmospheric pressure For water density, It is the acceleration due to gravity. The total depth of the water body. The depth of the top of the device from the water surface. This is a localized overpressure caused by gas accumulation. The high-pressure gas chamber is connected to the throat of the inner downflow channel through a built-in gas guide channel, forming a pressure source end for gas self-circulation.

[0042] After deaeration, the water flows over the inner pipe opening and into the downstream channel under the influence of gravity. At the inlet of the inner downstream channel, a set of helical guide vanes is rigidly installed. The geometric twist angle of these vanes is calculated using fluid dynamics to transform the vertically downward water flow into a high-speed rotating vortex. Here, the fluid forms a stable Rankine vortex structure, which is a combined flow field with a forced vortex at the center and free vortices on the periphery.

[0043] The formation of the vortex creates a low-pressure zone along the central axis of the downward flow channel. According to fluid dynamics principles, this results in a minimum pressure at the center of the vortex. With tangential velocity Closely related. To achieve automatic gas entrainment, the system's geometry must meet the critical self-entrainment condition, i.e., the gas chamber pressure must overcome the frictional resistance along the gas flow channel. The pressure remains greater than the pressure at the vortex core.

[0044] Based on Bernoulli's equation, this driving pressure difference is mainly derived from the kinetic energy of the water flow, and its approximate relationship is as follows: in, λ is the maximum tangential velocity in the swirling flow field, and λ is the axial velocity. The contribution coefficient to dynamic pressure. When this condition is met, the "exhaust gas" in the top air chamber is forcibly drawn into the center of the downward flow channel, achieving gas-liquid remixing.

[0045] See attached document Figure 2At the throat of the downstream flow channel, directly downstream of the negative pressure intake point, is the core component of this invention—the flow-induced vibration coupled pulse modulation component. This component comprises a flexible bistable oscillating ring made of a polymer elastic material, with an asymmetric valve structure designed on its inner wall. This flexible component is not a static part, but exists as a fluid-structure coupled oscillator.

[0046] When a high-speed swirling flow carrying bubbles passes through the flexible bistable oscillating ring, the interaction between the fluid dynamic pressure and the elastic restoring force induces high-frequency self-excited vibration (flutter) in the component. This vibration reduces the effective flow cross-sectional area of ​​the flow channel. The periodic changes modulate the continuous steady-state gas-liquid two-phase flow upstream into a pulse jet with a specific frequency.

[0047] This pulse modulation process is not merely a simple flow fluctuation, but a physical "chop" of the gas phase. The periodic contraction of the flexible ring cuts the continuously inhaled gas column into discrete gas slugs. Its oscillation frequency... It exhibits adaptive flow velocity characteristics and follows the Strouhal number control law:

[0048] In this formula, The Strouhal number is related to the properties of flexible materials. The average velocity of the fluid flowing through the throat. This is the characteristic hydraulic diameter of the oscillating ring. This design ensures that as the system's air intake increases, leading to a decrease in flow velocity... When the frequency increases, the oscillation frequency It will automatically rise, thereby cutting the air mass more densely and preventing a decrease in gas-liquid mixing efficiency under high load conditions.

[0049] Downstream of the flow-induced vibration coupled-pulse modulation component, a multi-level fractal healing grid is installed. This grid consists of multiple layers of staggered, blade-like blades, its spatial structure conforming to fractal geometry to increase turbulence dissipation. The grid's natural frequency... Designed to match the characteristic frequency of the pulse flow The matching is achieved, thereby inducing a slight resonance in the grid during fluid impact.

[0050] This resonant shear mode of "dynamic fluid impacting dynamic solid" causes the Weber number (WN) of bubble breakage to increase. Significantly improved. The Weber number, which defines the ratio of inertial force to surface tension, is a key parameter determining the particle size of broken bubbles.

[0051] in, The turbulent pulsation velocity induced by the pulse. The diameter of the bubble. This represents the surface tension coefficient of the gas-liquid mixture. Due to the extremely high instantaneous pulsation velocity introduced by pulse modulation... , making The number of bubbles far exceeds the critical breakup Weber number, causing large bubbles to break down into micron- or even nano-sized bubbles instantly, which greatly increases the gas-liquid mass transfer specific surface area.

[0052] The system has a radial laminar flow plate at the bottom as the outlet. This component is horizontally disc-shaped and located at the end of the downward flow channel. Its function is to convert the vertically downward high-speed oxygen-rich water flow into a horizontal radial flow, and to reduce the flow velocity by increasing the cross-sectional area of ​​the flow channel.

[0053] Controlling the outlet flow pattern is crucial for maintaining water stratification. This is achieved through the design of radial laminar flow channels, ensuring that the released water flow has a low Froude number. The density flow is governed by the following equation:

[0054] in, For export flow rate, The thickness of the outlet flow layer. Based on ambient cold water density Density of oxygen-rich water The difference is converted to gravitational acceleration. This design ensures that oxygen-rich water spreads smoothly across the lake bottom, avoiding disturbance to the upper thermocline or resuspension of bottom sediments.

[0055] This embodiment details the operation process and dynamic control strategy of the synergistic system for deep-water aeration and gas circulation in stratified water bodies. Through the continuous evolution of fluid dynamic states, this process achieves efficient gas dissolution and cascaded energy utilization.

[0056] During system startup, compressed air is supplied via pipeline to the bottom aeration device in the outer rising channel. The gas is released into the water as microbubbles, creating a gas-liquid mixing flow field. Due to the average density of the mixed fluid... Density lower than that of the surrounding water Under the action of buoyancy, an upward driving head is generated. This driving force overcomes the frictional resistance of the pipe wall and local head loss, pulling the deep water body upwards along the rising channel. During this upward movement, the gas and liquid phases undergo primary mass transfer under turbulence, and some oxygen dissolves in the water.

[0057] When the gas-liquid mixture reaches the top bell-shaped region, the fluid velocity decreases significantly due to the sudden expansion of the flow cross-sectional area. At this point, the flow field enters the gravity separation-dominated stage. According to Stokes' Law, the rising velocity of a bubble in water depends primarily on its diameter and the density difference between the gas and liquid. The design controls the downward flow velocity of the liquid to be lower than the terminal rising velocity of the bubbles, allowing undissolved free bubbles to overcome the drag force of the water flow, detach from the liquid phase, and accumulate at the top of the bell. As the gas continues to accumulate, the pressure within the top gas chamber increases. As the temperature gradually rises, a potential energy reservoir is established to drive the subsequent gas cycle.

[0058] Driven by gravitational potential energy, the deaerated water flows past the inner pipe overflow outlet and turns to enter the inner downstream channel. As the fluid passes through the spiral guide vanes at the inlet, its motion undergoes a qualitative change. Vertical potential energy is converted into rotational kinetic energy, and the water flow changes from a straight flow to a strong swirling flow. A stable low-pressure vortex core forms at the central axis of the downstream channel.

[0059] As the swirling intensity increases, the pressure at the center of the vortex core... Continuously decreasing. When satisfied... Under differential pressure conditions, the undissolved gas accumulated at the top is forcibly "drawn" into the center of the downward flow channel through the connecting conduit. This process is not driven by an external mechanical pump but entirely by the kinetic energy conversion of the fluid itself, achieving passive closed-loop gas recovery. The drawn-in gas is entrained into the high-speed rotating water flow in the form of a gas column, forming a ring-shaped flow pattern with gas and liquid flowing in the same direction.

[0060] The subsequent flow modulation stage is the core process of this invention. The swirling mixture of the inhaled gas flows through the flow-induced vibration coupled pulse modulation component at the throat. The flexible bistable oscillating ring is subjected to periodic fluid-structure interaction excitation under the action of fluid dynamic pressure. This excitation causes the flexible ring to rapidly switch between two steady states of expansion and contraction, applying high-frequency mechanical disturbances to the flowing gas-liquid two-phase flow.

[0061] During this process, the continuous gas column is mechanically cut off by the periodic contraction of the flexible ring, forming discrete gas slugs. The originally stable steady flow is modulated into an unsteady pulsed flow, and the instantaneous pressure and velocity in the flow field exhibit periodic and violent fluctuations. This pulse effect greatly enhances the turbulence intensity of the fluid, providing sufficient energy input for subsequent bubble breakup.

[0062] Following this, the pulsed gas-liquid flow impacts the downstream multi-stage fractal shear grid. Because the frequency of the pulsed flow matches the natural frequency of the grid structure, a resonant response is induced in the grid. At this point, the bubbles are not only subjected to the shearing action of the water flow but also to the active impact of the vibrating grid. This synergistic effect of multiple physical fields causes the shear stress borne by the bubbles to far exceed the limit that their surface tension can sustain.

[0063] According to Kolmogorov's turbulence theory, the maximum stable diameter of the bubble... With turbulent dissipation rate Closely related: in, It is the critical constant. The surface tension is the factor. The combined effect of pulse modulation and resonant shearing increases the local turbulent dissipation rate. It increases exponentially, thus forcing The size of the gas mass decreases dramatically. Large gas clouds break down instantly into micron-sized microbubbles, multiplying the gas-liquid contact area and resulting in a qualitative leap in mass transfer efficiency. At the same time, the strong turbulent kinetic energy introduced by the pulsed flow effectively suppresses the coalescence behavior of microbubbles during their downward movement, maintaining highly dispersed flow characteristics.

[0064] Finally, the water carrying a high concentration of dissolved oxygen reaches the bottom outlet. As the fluid passes through the radial laminar flow plate, its kinetic energy is dissipated, and the flow velocity gradually decreases to within the range permitted by the environment. The oxygen-enriched water slowly diffuses horizontally in the form of laminar density flow, forming a high-oxygen zone in the bottom water, completing the entire process of deep-water oxygenation without causing any destructive disturbance to the upper thermocline.

[0065] This invention addresses the issues of gas-liquid mass transfer efficiency and hydrodynamic stability during deep-water aeration by constructing a theoretical model based on vortex-induced self-absorption and fluid-structure interaction pulse modulation. This model reveals the physical mechanisms underlying the system's core components in energy conversion, flow control, and interface reconstruction.

[0066] Regarding the vortex-induced self-absorption mechanism, this invention utilizes the Rankine vortex model to describe the swirling flow field distribution in the inner downflow channel. Assuming the fluid is incompressible and inviscid, the swirling flow field is formed by a radius of... It consists of a forced vortex core and an external free vortex region. Within the forced vortex core region... tangential velocity With radius Proportional, that is ,in Angular velocity; in the free vortex region The tangential velocity is inversely proportional to the radius, that is... Where T is circulation. Based on the radial momentum balance equation, the pressure distribution in the flow field... satisfy:

[0067] The pressure at the center of the vortex core can be obtained by integration. Significantly lower than the edge pressure. To achieve stable gas self-priming, the system must meet the critical intake condition, i.e., the gas chamber pressure. The resistance at the two-phase flow interface and pipeline losses need to be overcome. Using Bernoulli's equation and neglecting the influence of gravity, the intake-driven pressure difference... This can be expressed as:

[0068] in, For the maximum tangential velocity, Axial flow velocity The contribution factor to dynamic pressure. This formula shows that by optimizing the twist angle of the helical guide vanes to improve... This can significantly enhance the system's self-priming capability.

[0069] Regarding the flow-induced vibration coupled pulse modulation mechanism, this invention utilizes the principle of fluid-structure interaction (FSI) to achieve active control of the flow state. A flexible bistable oscillating ring serves as the flow-induced oscillator, and its vibration behavior is controlled by the Strouhal number. When the fluid flows through a characteristic dimension of When using flexible components, the eddy shedding frequency or flow-induced oscillation frequency... With flow rate A linear relationship is observed:

[0070] in, This is a dimensionless parameter related to the elastic modulus and geometry of the flexible material. The vibration frequency determines the modulation characteristics of the pulsed flow. Assume the steady-state flow rate is... Modulated instantaneous flow rate It can be approximated as:

[0071] in, The flow modulation coefficient depends on the radial contraction amplitude of the flexible ring. This pulse modulation transforms the continuous gas-liquid flow into a gas-liquid slug flow with a specific frequency and wavelength, and the slug length... By adjusting With respect to material properties, it can make It is in the optimal breaking range.

[0072] Regarding the bubble breaking and interface reconstruction mechanism, this invention focuses on the Weber number. The influence of the Weber number on bubble stability. The Weber number characterizes the competition between fluid inertial forces disrupting the bubble interface and surface tension maintaining the interface shape:

[0073] in, The velocity difference is at the bubble size. The diameter of the bubble. is the surface tension coefficient.

[0074] In conventional shear flow, It is mainly determined by the average velocity gradient, while in the pulse resonance field of this invention, Pulse-induced turbulent pulsation velocity Dominant. When the pulse frequency Approaching the natural frequency of the downstream shear grid At this time, the system resonates, and the turbulent pulsation velocity... It reaches its peak value. According to turbulent breakup theory, the critical breakup Weber number is... Typically, it is around 1.2 to 2.0. This system uses pulsed power enhancement to increase the actual Weber number. This forces the bubbles to break in a cascade.

[0075] The particle size distribution of the broken bubbles follows a log-normal distribution, and their Sauter average diameter is... With energy dissipation rate The relationship is: Because pulse modulation introduces a periodic high-energy dissipation region, the average value of e is significantly increased, leading to... This reduces the size to the micrometer scale. This significantly increases the specific surface area for gas-liquid mass transfer. It also makes the volumetric mass transfer coefficient This represents an order-of-magnitude improvement, enabling highly efficient oxygenation in deep-water environments.

[0076] This embodiment, based on actual environmental parameters of a deep-water reservoir, details the specific configuration and application effects of a synergistic enhancement system for deep-water aeration and gas circulation in stratified water bodies. This application scenario aims to solve the problem of oxygen deficiency in deep water layers while strictly maintaining the naturally formed thermal stratification structure of the reservoir to prevent the release of pollutants from the bottom sediment.

[0077] The selected target reservoir has a maximum water depth of 50 meters, with the thermocline located between 15 and 20 meters underwater in summer. Based on this hydrological characteristic, the installation depth of this system is set at 35 meters, meaning the main body of the device is entirely situated in the cold water layer below the thermocline. The total height of the device is designed to be 10 meters, with the outer ascending channel having a diameter of 1.5 meters and the inner descending channel having a diameter of 8 meters. The diameter of the top gas-liquid separation and collection chamber is extended to 3.0 meters to ensure sufficient velocity attenuation and gas-liquid separation space.

[0078] After system deployment, compressed air is injected into the bottom of the outer rising channel via a shore-based air compressor. The initial injection volume is set to... As the airlift effect is established, the bottom water is lifted to the top of the device at a velocity of approximately 0.8 m / s. After the mixed fluid enters the separation chamber, the velocity rapidly drops below 0.2 m / s, and most of the undissolved bubbles are successfully separated and accumulate at the top of the bell jar under buoyancy, forming a stable gas chamber with an overpressure of approximately 0.15 bar.

[0079] After deaeration, the water overflows the inner weir and enters the inner downstream channel. Under the action of the spiral guide vanes, the water flow transforms into a strong swirling flow, generating negative pressure at the center. At this point, the accumulated gas in the top air chamber is automatically drawn into the downstream channel, with an intake volume of approximately [missing information]. The process achieved an internal gas recirculation rate of approximately 2596 min. This process requires no external electrical drive and relies entirely on the conversion of water flow potential energy. The mixed swirling flow of the inhaled gas then passes through a flow-induced vibration coupled pulse modulation assembly at the throat. The assembly uses a flexible bistable oscillating ring with a characteristic diameter of 0.6 m, and the material's elastic modulus matches the Strouhal number at the current flow rate. Under an average flow velocity of 2.0 m / s, self-excited vibrations with a frequency of approximately 0.67 Hz are generated. This vibration modulates the continuous gas-liquid flow into a pulsed flow, and the pulsed gas clusters subsequently impact downstream multi-stage fractal shear grids with a spacing of 10 mm. Through resonant shearing, the average bubble size is reduced from the initial millimeter level to below 100 micrometers. The microbubbles dissolve rapidly under high pressure during their descent, resulting in an oxygen saturation level of over 90% in the oxygen-enriched water reaching the bottom. Finally, the water is released through a radial laminar flow plate with a bottom diameter of 4.0 meters. The outlet flow velocity is controlled at... Below s, satisfying the Froude number Under the conditions of density flow, oxygen-rich water can be steadily diffused and covered along the lake bottom, effectively improving the dissolved oxygen level in the deep water area.

Claims

1. A method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies, characterized in that, Includes the following steps: Step S1: Deploy a coaxial dual-channel circulation device below the thermocline of the stratified water body. The device includes an outer rising channel, an inner descending channel, and a gas-liquid separation and gas collection chamber located at the top. Step S2: Inject gas into the outer rising channel to drive the bottom water to flow upward and perform primary dissolution using the airlift effect; Step S3: After the mixed fluid reaches the top, it undergoes gas-liquid separation in the gas-liquid separation and gas collection chamber. The separated undissolved gas accumulates to form a high-pressure gas chamber, and the degassed water flows into the inner downflow channel. Step S4: The water in the inner downflow channel forms a vortex, creating a negative pressure zone in the center of the channel. The pressure difference is used to draw the gas in the high-pressure gas chamber into the center of the vortex, thus achieving closed-loop gas recovery. Step S5: The mixed swirling flow of the inhaled gas passes through the flow-induced vibration coupled pulse modulation component, which induces periodic vibration by utilizing the fluid-structure interaction effect, thus modulating the continuous flow state into a pulsed flow state; Step S6: The pulsed flow fluid impact shearing component breaks up bubbles and reconstructs the interface, and then the oxygen-rich water is released back to the bottom of the water body in a laminar flow form.

2. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 1, characterized in that, In step S3, the gas-liquid separation gas collection chamber achieves gravity separation through flow velocity reduction and flow deflection; The separated undissolved gas gathers at the top of the inverted bell jar, establishing gas phase pressure potential energy; the degassed water enters the inlet of the inner downflow channel by gravity.

3. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 1, characterized in that, In step S4, a spiral flow guide structure is provided at the inlet of the inner layer downward flow channel; When water passes through the spiral guide structure, the vertical velocity component is converted into the tangential velocity component, forming a Rankine vortex structure with a central pressure lower than the outer pressure. When the pressure at the center of the vortex is lower than the pressure in the high-pressure gas chamber, undissolved gas is passively entrained into the inner downward flow channel through the gas guide channel.

4. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 1, characterized in that, In step S5, the flow-induced vibration coupled pulse modulation component is installed at the throat position of the inner downflow channel, and the component includes a flexible bistable oscillating ring; When a high-speed swirling flow passes through a flexible bistable oscillating ring, the fluid dynamic pressure forces the flexible material to undergo high-frequency self-excited switching between an expansion steady state and a contraction steady state, thereby changing the flow cross-sectional area of ​​the channel.

5. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 4, characterized in that, The specific process of modulating the continuous flow state into a pulsed flow state in step S5 is as follows: The periodic contraction and expansion of the flexible bistable oscillating ring mechanically chops the continuously inhaled gas-liquid mixture, cutting the continuous gas column into discrete pulsed gas clusters, causing the fluid to generate periodic pressure pulsations.

6. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 5, characterized in that, In step S5, the frequency of the pulse flow state has adaptive characteristics; The frequency is positively correlated with the average flow velocity of the fluid flowing through the throat. When the air intake increases, leading to an increase in flow velocity, the vibration frequency of the flexible bistable oscillating ring automatically increases to increase the frequency of cutting the air mass.

7. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 1, characterized in that, In step S6, the shearing component is a multi-level fractal shear grid; The pulse frequency of the pulsed flow state is configured to be close to the natural frequency of the multi-level fractal shear grid, inducing the grid to resonate slightly. The vibrating grid structure actively impacts the pulsed air mass, thereby achieving forced breakage of the bubbles.

8. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 7, characterized in that, The interface reconstruction mentioned in step S6 refers to: Large bubbles break down into micron-sized bubbles under the synergistic effect of pulsed turbulence and resonant grid, which increases the specific surface area of ​​the gas-liquid two-phase contact. At the same time, the pulsed turbulent kinetic energy inhibits the secondary coalescence of microbubbles during the downward process.

9. The method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to claim 1, characterized in that, In step S6, the release of the water body back to the bottom layer in a laminar flow manner is achieved through a radial laminar flow disk at the bottom; When oxygen-rich water passes through a radial laminar flow disk, the momentum in the vertical direction is converted into momentum in the horizontal direction, and the outlet velocity is controlled below the critical velocity that does not cause resuspension of bottom sediments.

10. A method for synergistic enhancement of deep-water aeration and gas circulation in stratified water bodies according to any one of claims 1 to 9, characterized in that, The method described above establishes an energy gradient conversion mechanism: In the outer rising channel, the buoyancy potential energy of the gas is converted into the lifting potential energy and kinetic energy of the water. In the inner descending channel, the potential energy of the water is converted into swirling kinetic energy for air intake. The flow-induced vibration coupled pulse modulation component converts part of the fluid kinetic energy into mechanical vibration energy for bubble breakage and interface renewal.

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