CN115228515A - Series-connection domain limiting device and method for regulating and controlling size distribution of dispersed phases in multiphase system - Google Patents
Series-connection domain limiting device and method for regulating and controlling size distribution of dispersed phases in multiphase system Download PDFInfo
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- CN115228515A CN115228515A CN202110442565.5A CN202110442565A CN115228515A CN 115228515 A CN115228515 A CN 115228515A CN 202110442565 A CN202110442565 A CN 202110442565A CN 115228515 A CN115228515 A CN 115228515A
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
- B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
- B01L3/502769—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by multiphase flow arrangements
- B01L3/502784—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by multiphase flow arrangements specially adapted for droplet or plug flow, e.g. digital microfluidics
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L2300/00—Additional constructional details
- B01L2300/08—Geometry, shape and general structure
- B01L2300/0861—Configuration of multiple channels and/or chambers in a single devices
Abstract
The invention relates to the field of micro-fluidic, and discloses a serial domain limiting device and a method for regulating and controlling the size distribution of a dispersed phase in a multi-phase system, wherein the serial domain limiting device comprises an inlet channel (1), a domain limiting unit and an outlet channel (4) which are continuously arranged, the domain limiting unit comprises at least two domain limiting channels (2) and at least one intermediate channel (3) which are sequentially and alternately connected between the inlet channel and the outlet channel in series, and the flow cross-sectional area of the domain limiting channels is smaller than that of the intermediate channel at least at the positions where the domain limiting channels are connected with each other. The series-connection limited-area device can realize the regulation and control of dispersed phases such as bubbles/liquid drops and the like only by being connected in series with other devices, and has the advantages of simple structure, convenient operation and the like; the control method can effectively utilize the extrusion and the pulse impact of the continuous phase and the self instability and the rapid stretching of the dispersed phase and other rupture mechanisms to realize the effective control of the rupture behavior and the size distribution of the bubbles/liquid drops.
Description
Technical Field
The invention relates to the field of microfluidics, in particular to a series domain limiting device for regulating and controlling the size distribution of a dispersed phase in a multiphase system. On the basis, the invention also relates to a method for regulating and controlling the size distribution of the dispersed phase in the multi-phase system.
Background
Multiphase flow is widely found in nature and in the process industries of chemical, petroleum, power, metallurgy, food, and the like. For a chemical reactor, dispersed phases such as bubbles and liquid drops not only can directly influence a velocity field, but also can change the mass transfer and heat transfer effects of a system by changing the phase interface property and the like, and finally influence the performance of equipment under the micro scale and the macro scale. Therefore, controlling the deformation and collapse behavior of the bubbles/droplets, optimizing the size distribution and heterogeneous dispersion process have a direct and important impact on the momentum, mass and heat transfer of the entire reaction system.
The bubble/droplet breaking and generating process is generally considered to be the result of the combined action of external factors and internal factors, wherein the external factors include flow field (such as turbulence characteristics, shear rate and the like), liquid phase properties (such as viscosity, density and the like) and other external conditions (such as temperature, external electric field, acoustic field and the like); the internal factors mainly include the properties of the two phases, and the internal forces (such as viscosity, surface tension, etc.) of the dispersed phase. The main causes of deformation and rupture of the dispersed phase include turbulent pulsation and collision, interfacial instability, viscous shear of the continuous phase, erosion (scouring) of the fluid, and the like. Although the turbulent flow field can provide high energy to promote bubble collapse, the structure is complex and the fluctuation is high, so researchers have not yet determined the turbulence mechanism, and therefore the control of bubble size by using turbulence pulsation and collision has very high difficulty and very severe operating conditions. The method for realizing size regulation and control of bubbles/liquid drops by utilizing a laminar flow system has obvious advantages in the aspects of stability, controllability and the like, and particularly in recent years, microchannel equipment such as a microreactor and the like are paid more and more attention and are applied due to the characteristics of small size, no back mixing, large specific surface area, high mass and heat transfer coefficients, capability of realizing continuous operation and the like. The majority of the micro-channels are laminar flow systems, and a foundation is also created for realizing the regulation and control of dispersed phases such as bubbles/liquid drops and the like.
At present, the method for regulating and controlling the size of bubbles/liquid drops is mostly realized by cross-shaped, T-shaped, coaxial and similar channel structures, on one hand, the method has very high requirements on equipment processing and process parameter control, on the other hand, at least two channels and driving devices are needed, the cost is increased, and the complexity of the whole process flow is inevitably improved; and the external field strengthening also increases the cost and the difficulty of processing and operation.
Disclosure of Invention
The invention aims to solve the problems that the size regulation of a dispersed phase needs a complex channel structure and the size control is unstable in the prior art, and provides a series domain limiting device for regulating the size distribution of the dispersed phase in a multiphase system.
In order to achieve the above object, the present invention provides, in one aspect, a series-connected confinement device for regulating size distribution of dispersed phases in a multiphase system, comprising an inlet channel, a confinement unit and an outlet channel, which are arranged in series, wherein the confinement unit comprises at least two confinement channels and at least one intermediate channel, which are alternately connected in series between the inlet channel and the outlet channel in sequence, and the flow cross-sectional area of the confinement channels is smaller than that of the intermediate channel at least at the position where the confinement channels are connected with each other.
Preferably, the limiting channel has a constant cross-sectional flow area over its extent.
Preferably, the extension length of the limited area channel is notLess than 10 times the maximum width dimension of the confinement passage and/or the cross-sectional flow area of the confinement passage is not greater than 0.01mm 2 。
Preferably, the maximum width dimension of the confinement channels is no more than half of the maximum width dimension of the intermediate channels.
Preferably, the flow cross-sectional area of the domain-defining passage is smaller than the flow cross-sectional area of the inlet passage, and the inlet passage tapers in a direction toward the domain-defining unit at a position where it meets the domain-defining unit.
Preferably, the cross-sectional flow area of the outlet channel increases in a direction away from the confinement unit.
Preferably, the outlet passage extends gradually in a direction away from the confinement unit at a position where it meets the confinement unit; and/or the bottom of the outlet channel is provided with a step part which is downward step by step so that the flow cross-sectional area of the outlet channel is increased gradually.
Preferably, the series confinement device has a housing, and the inlet passage, the confinement passage, the intermediate passage and the outlet passage are formed in the housing along a same line.
Preferably, the material of the shell is one or more of glass, metal, ceramic, alloy, polymer and composite material.
In a second aspect, the present invention provides a method for controlling the size distribution of dispersed phases in a multiphase system, comprising: s1, material analysis and pretreatment, namely determining at least one material parameter of density, viscosity, surface tension and rheological property of a substance to be operated, and filtering a solution in the substance to be operated to remove impurities; s2, selecting the corresponding domain limiting device according to the expected dispersed phase size and the determined material parameter, and connecting the serial domain limiting device in series to a fluid conveying control system; s3, the fluid conveying control system is used for controlling the multiphase materials including the operated substances to be introduced into the inlet channel, and the multiphase materials are output after flowing through the limited area unit and the outlet channel.
Through the technical scheme, the series-connection domain limiting device can realize the regulation and control of dispersed phases such as bubbles/liquid drops and the like only by being connected in series with other devices, does not need additional channels, driving devices or internal components, and has the advantages of simple structure, convenience in operation and the like; the control method can effectively utilize the extrusion and the pulse impact of the continuous phase and the self instability and the rapid stretching of the dispersed phase, and can realize the effective control of the breaking behavior and the size distribution of the bubbles/droplets with higher control precision by connecting a plurality of limited channels in series.
Drawings
FIG. 1 is a schematic structural diagram of a series confinement unit according to a first preferred embodiment of the invention;
FIG. 2 is a velocity vector diagram for a multiphase system within the series-connected domain-limiting device shown in FIG. 1;
FIG. 3 is a flow chart of a multiphase system within the series confinement unit shown in FIG. 1;
FIG. 4 is a schematic view of the connection structure of the inlet passage and the confinement unit in the serial confinement arrangement according to another preferred embodiment of the invention;
FIG. 5 is a schematic diagram of the configuration of the outlet passages in the series of confinement devices in accordance with another preferred embodiment of the invention;
FIG. 6 is a size distribution of bubbles produced in example 1;
FIG. 7 is a size distribution of bubbles generated in comparative example 1;
FIG. 8 is a size distribution of bubbles generated in comparative example 2;
FIG. 9 is the size distribution of the droplets produced in example 2;
fig. 10 is a size distribution of droplets produced by comparative example 3.
Description of the reference numerals
1-an inlet channel; 2-a confinement channel; 3-an intermediate channel; 4-outlet channel.
Detailed Description
The following describes in detail embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
Referring to fig. 1 to 3, a serial confinement device for regulating the size distribution of dispersed phases in a multiphase system according to a preferred embodiment of the present invention comprises an inlet passage 1, a confinement unit and an outlet passage 4 arranged in series, wherein the confinement unit comprises at least two (three shown) confinement passages 2 and at least one (two shown) intermediate passage 3 alternately connected in series between the inlet passage 1 and the outlet passage 4 in sequence, and the flow cross-sectional area of the confinement passages 2 is smaller than that of the intermediate passage 3 at least at the position where they meet each other.
Thus, by feeding the multiphase material into the inlet channel 1, the multiphase material continues to flow through the respective confinement unit and the outlet channel 4. In the process, due to the change of the cross-sectional area of the flow at the position where different channels are connected with each other, the size of the dispersed phase in the multiphase system can be regulated. Specifically, when flowing from the inlet passage 1 into the domain-defining passage 2 having a relatively small flow-through cross-sectional area and flowing out from the domain-defining passage 2 to the intermediate passage 3 and the outlet passage 4, the continuous phase in the multiphase system generates a squeezing action and a pulsating impact, so that the dispersed phase therein is broken; in the process of flowing through the restricted passage 2, the dispersed phase can be stretched by utilizing a relatively small flow cross section area, and the breaking behavior and the size distribution of bubbles/liquid drops can be effectively controlled by utilizing breaking mechanisms such as instability and rapid stretching of the dispersed phase.
The series-connection limited domain device can realize the regulation and control of dispersed phases such as bubbles/liquid drops and the like only by being connected in series with other devices, does not need additional channels, driving devices or internal components, and has the advantages of simple structure, convenient operation and the like. The invention can effectively realize the regulation and control of dispersed phases such as bubbles/liquid drops and the like in a multi-phase system, is suitable for various multi-phase systems such as gas-liquid, liquid-liquid, gas-liquid-solid, gas-liquid, liquid-liquid and the like, and provides required conditions for material conveying, mixing, dispersing and reacting processes; the provided confinement unit can be independently used as a micro-reactor, a tubular reactor or a micro-mixer, can be combined with a heat exchange unit, a collection unit or a reaction/mixing unit and the like to realize a complete set of functions, and has wide application prospects in the fields of chemical engineering, biology, medicines, electronics, machinery and the like.
Based on the regulation mechanism, the series-connection domain-limiting device can be formed into various different structural forms, and the size distribution of a dispersed phase in a multi-phase system can be regulated and controlled by utilizing various rupture mechanisms. For example, the inlet channel 1, the confinement unit and the outlet channel 4 may be formed directly by a tube-like housing as illustrated, but also by fluid channels formed in other forms (casting). In the illustrated preferred embodiment, the inlet channel 1, the delimiting channel 2, the intermediate channel 3 and the outlet channel 4 each have a constant flow cross-sectional area over their extent; in other embodiments, it can also be provided with a varying flow cross-sectional area according to the control requirements.
With continued reference to fig. 1 to 3, the limiting channel 2 extends in a straight line and has a constant cross-sectional flow area over its extension. Wherein the cross-sectional flow area of the confinement channel 2 should not be too large in order to effectively stretch the dispersed phase. For example, the extension length of the limiting channel 2 is not less than 10 times of the maximum width dimension of the limiting channel 2, and/or the flow cross-sectional area of the limiting channel 2 is not more than 0.01mm 2 . In the preferred embodiment shown in the drawing, the flow cross-section of the limiting channel 2 is a square cross-section with a width dimension of 100 μm and a flow cross-sectional area of 0.01mm 2 . In an alternative embodiment, in which the field limiting channel 2 is formed, for example, with a circular throughflow cross section, the above-mentioned maximum width dimension is the diameter of the channel.
In order to effectively utilize the extrusion and pulse impact effects of the continuous phase to realize the rupture and size control of the dispersed phase through the change of the flow cross-sectional area, the flow cross-sectional area of the limiting passage 2 is greatly different from the flow cross-sectional areas of the inlet passage 1, the intermediate passage 3 and the outlet passage 4. In a preferred embodiment, the maximum width dimension of the confinement channels 2 does not exceed half the maximum width dimension of the inlet channels 1, the intermediate channels 3 and the outlet channels 4.
According to the regulation and control requirements, the series connection limiting device can be formed into different structural forms so as to strengthen or weaken the expected effect of one or more of the regulation and control mechanisms, and a targeted leading mechanism is selected according to different systems, so that the application range is wide. In an alternative embodiment shown in fig. 4 and 5, the inlet channel 1 extends tapering in the direction towards the confinement unit at the location where it meets the confinement unit, e.g. the part of the inlet channel 1 adjacent to the confinement unit is formed in a tapering cone shape to reduce the squeezing action of the continuous phase there.
Similarly, the cross-sectional flow area of the outlet channel 4 increases in a direction away from the confinement unit to reduce the pulsating impact effect of the multiphase system flowing in the outlet channel 4. The adjacent part of the outlet channel 4 to the confinement unit can be formed into a gradually expanding cone shape, and the bottom of the outlet channel 4 is formed with step parts which are downward step by step, so that the through-flow cross-sectional area of the outlet channel 4 is increased gradually. Other aspects of this alternative embodiment may be the same as or have the same variations as the previously described preferred embodiment and will not be repeated here.
In the preferred embodiment described above, the series confinement device is formed by a tubular housing in which the inlet passage 1, the confinement passage 2, the intermediate passage 3 and the outlet passage 4 are formed along the same line. The shell is made of one or more of glass, metal, ceramic, alloy, polymer and composite materials, and the processing mode can be engraving and machining, dry etching, LIGA, injection molding, wet etching, photoetching, 3D printing and the like.
Based on the series connection domain limiting device, the invention also provides a method for regulating and controlling the size distribution of the dispersed phase in a multi-phase system, and the effective control of the breaking behavior and the size distribution of bubbles/liquid drops is realized by scientifically regulating and controlling mechanisms such as extrusion and pulse impact of a continuous phase and self instability and rapid stretching of the dispersed phase. The method comprises the following operation steps:
s1, material analysis and pretreatment: determining material parameters such as density, viscosity, surface tension (interfacial tension), rheological property and the like of a material (a material to be operated) involved in operation, which can influence the effect of a dispersed phase; and carrying out suction filtration, temperature control and other treatments on the solution to enable the solution to meet the feeding and operating requirements.
S2, determining a domain limiting structure and operation parameters: and (3) making a domain-limiting structure design and operation scheme according to the requirements of expected achieved dispersed phase size and the like. The tandem confinement device provided by the invention establishes a slit or a pore throat-shaped structure with a certain length by reducing the size of the channel, is operated in tandem with the main channel, utilizes various mechanisms causing fracture, including but not limited to extrusion, pulsation, impact and erosion of a continuous phase, instability of a dispersed phase, rapid tensile fracture and the like, and can strengthen one or more mechanisms according to the characteristics and requirements of a specific system to achieve the expected effect. The regulation and control of the dispersed phase is determined by the structure (shape, size, etc.) and the operating parameters (flow rate/quantity of various materials, operating pressure, feeding mode, etc.), and the method for determining the structure and the operating parameters comprises theoretical analysis, numerical simulation, condition experiment, experience or semi-experience model, etc. Meanwhile, one limiting channel or a plurality of limiting channels can be selected to be used in series/parallel operation according to the characteristics of a specific operation system. It should be noted that, a plurality of confinement channels are connected in series between the inlet channel and the outlet channel through the intermediate channel, so that the pressure drop can be increased while the uniformity and stability of the system are improved, and therefore, the number of the confinement channels can be adjusted according to specific process requirements and material properties in the actual process.
Device construction: besides selecting the series-connection limited-area device, the devices (fluid conveying control system) such as inlet channels, pumps, pipelines, flowmeters, valves, control systems, reactors and the like which are possibly required for conveying and controlling the fluid are selected, built and connected. The invention has no special requirements on upstream and downstream conditions, for example, the upstream can be matched with various devices for generating bubbles/liquid drops such as T-shaped, Y-shaped, coaxial type, focusing type, cross type and the like, and only needs to be connected with a series connection limited domain device in series without additional equipment.
S3, feeding and dispersed phase regulation: and (3) carrying out multiphase feeding according to set operating conditions to realize the regulation and control of dispersed phases such as bubbles/liquid drops and the like. If necessary, measurement can be carried out by various measurement means such as a camera, PIV/PLIF, probe, pressure gauge/flowmeter, etc. The regulated multiphase system can be connected with a reactor, a mixer, a heat exchanger or other conveying equipment as required.
In addition, the regulation method of the present invention may include post-treatment and calibration steps. And if the size of the disperse phase does not reach the ideal condition, adjusting and optimizing parameters according to the actual condition.
The invention can promote the coalescence of partial micro bubbles/liquid drops by utilizing the domain limiting function of the wall surface and the contact and collision between the dispersed phases before and after the expanding area while promoting the rupture of larger bubbles/liquid drops, thereby effectively regulating and controlling the size of the dispersed phases within a target range. The confinement structure can effectively improve multiphase mixing and transfer efficiency, not only improves local flow velocity, shear rate and turbulence degree, but also reduces mass transfer distance and further strengthens the mixing process. According to different processes and material characteristics, the invention can adjust the number of units, structural parameters and operating conditions, thereby pertinently strengthening the fracture leading mechanism and realizing the size distribution meeting the expected target, and has wide application range.
The invention can meet the requirements of the fields of chemical industry, biology, medicine, electronics, machinery and the like on the size distribution of dispersed phase bubbles/droplets, and is suitable for various multi-phase systems such as gas-liquid, liquid-liquid, gas-liquid-solid, gas-liquid, liquid-liquid and the like; can also be used as a micromixer/reactor and applied to a series of chemical processes: oxidation, peroxidation, reduction, addition, metathesis, substitution, polymerization, nitration, epoxidation, alkylation, hydrogenation, dehydrogenation, organometallic reactions, carbonylation, alkoxylation, halogenation, dehalogenation, carboxylation, arylation, coupling, condensation, dehydration, alcoholysis, hydrolysis, ammonolysis, etherification, ketonization, saponification, isomerization, diazotization, and enzymatic reactions, among others.
In the specific implementation process of the invention, according to the actual process requirements and material properties, the adjustment and optimization of structural properties such as channel materials, channel dimensions, confinement structure dimensions/shapes and the like and the design of operation parameters such as flow rate, pressure, proportion and the like can be carried out, and the balance of pressure drop and dispersion can be adjusted to obtain the best performance: for example, by increasing the flow rate of the mixing system, the size ratio of the inlet, the pressure differential at the inlet can be increased to push the bubble/droplet to break; the bubble/liquid drop rupture can be effectively promoted and the size can be reduced by reducing the size of the confinement structure; by increasing the length of the confinement section, local instability-induced fragmentation of the bubble/droplet can be promoted; by increasing the size ratio of the outlet, the jet effect of the liquid phase can be increased to promote sub-bubble/droplet shedding.
Example 1: bubble size regulation in gas-liquid two-phase flow
A mixed system of 95% glycerol and water is prepared at room temperature, and the properties of the system, such as the density of 1255 kg.m -3 Surface tension coefficient of 0.0675 Nm -1 And viscosity of 0.58 pas. And stirring and mixing the solution, then carrying out suction filtration, and filtering out impurities. The regulation and control aim is to provide nitrogen bubbles with equivalent diameter ranging from 150 to 200 mu m, theoretical analysis and numerical calculation are carried out aiming at target requirements and material characteristics, and a scheme that micro bubbles are generated through a cross focusing structure and then the bubbles are further regulated and controlled by connecting two middle channels in series with three restricted channels is determined. Wherein the size of the confinement channels is 100 μm and the length is 1mm (FIG. 1). The passageway adopts the metal material, forms through cnc engraving and milling machine precision finishing to it is sealed to be connected with the shell through forms such as welding and screw thread.
Introducing the solution into a micro-injection pump, connecting an injector with a nitrogen steel cylinder, filling the injector with nitrogen, then loading the injector into the micro-injection pump, and connecting the injector with the micro-channel by using a rubber tube. And (3) building a backlight lamp and a high-speed camera, adjusting the relative positions of the backlight lamp and the high-speed camera and the micro-channel structure, and shooting the generated bubbles. Starting a micro-injection pump to drive liquid, controlling the flow of each phase, completing the generation of micro bubbles by using a cross focusing structure, further regulating and controlling the generated bubbles by using a confinement structure, acquiring and maintaining pictures after the flow is stable, and performing bubble identification and size calculation by using a digital image processing technology at the later stage.
The result shows that the structure provided by the method can effectively control the flow process, similar local velocity gradient and pressure difference are generated in each domain-limited structure, the bubbles are rapidly distorted and unstably broken (figure 2 and figure 3), the sizes of the bubbles are gradually close to the ideal distribution target, the sizes of the finally generated bubbles are more than 90% in the size range of 150-200 mu m (figure 6), the size regulation of the bubbles can be effectively realized, the process requirement is met, and the control precision is greatly improved without increasing the operation complexity.
Comparative example 1: single confinement channel for bubble size regulation in gas-liquid two-phase flow
The bubble size of the system in the embodiment 1 is regulated and controlled by using a single limited passage, wherein the used materials are the same as those in the embodiment 1, and the driving, connecting and shooting equipment are the same, and the difference is that the multistage series structure is changed into only one limited passage.
Controlling the flow of each phase by using a micro-injection pump, collecting and maintaining pictures after the flow is stable, performing bubble identification and size calculation by using a digital image processing technology at the later stage, and feeding back and optimizing operation parameters according to results until the size of the generated bubbles is closest to a target condition.
The results show that the device produces about 85% of bubbles in the size range of 150-200 μm (fig. 7), and the regulation of bubble size can be realized to a certain extent, but the control precision is lower than that of a plurality of devices connected in series.
Comparative example 2: adjustment and control of bubble size in gas-liquid two-phase flow by T-shaped bifurcation structure
The bubble size of the system in the embodiment 1 is regulated and controlled by using a single T-shaped bifurcation structure, wherein the used materials are the same as those in the embodiment 1, and the driving, connecting and shooting equipment are the same, and the difference is that the bubble generation system is changed into a structure that gas phase and liquid phase pass through a T-shaped pipeline.
And controlling the flow of each phase by using a micro-injection pump, acquiring and maintaining pictures after the flow is stable, performing bubble identification and size calculation by using a digital image processing technology at the later stage, and feeding back and optimizing operation parameters according to results until the size of the generated bubbles is closest to a target condition.
The results show that the method produces only about 50% of bubbles in the size range of 150-200 μm (fig. 8), the bubble size distribution is not uniform, and the control precision is obviously lower than that of the device of the invention.
Example 2: droplet size regulation in liquid-liquid two-phase flow
Adding 0.5 mass percent of sodium dodecyl sulfate into deionized water at normal temperature, uniformly stirring in a pretreatment beaker to serve as a continuous phase, sucking cyclohexane by using an injector to serve as a dispersed phase, measuring the material properties of the two phases, and filtering and removing impurities.
Theoretical analysis and numerical calculation are carried out according to target requirements and material characteristics, and a scheme that liquid drops are generated through a T-shaped structure and then are further regulated and controlled by utilizing a five-stage series connection limited domain structure is determined. The microchannel is made of Polydimethylsiloxane (PDMS) material, and is formed by gluing, photoetching, mask processing and other operations to form microchannels for flowing of a continuous phase and a disperse phase, and then bonding with a glass substrate. The size of the confinement structure is 80 micrometers, the length of the confinement structure is 1mm, and the outlet is provided with a multi-stage stepped reducing structure, so that the purpose of placing the liquid drops to be broken again due to stronger liquid phase impact caused by overlarge channel size ratio is achieved. The difference from the structure of example 1 is that the liquid drop of the present system is relatively easy to deform and break, and the inlet and outlet are adjusted to have a gradually reducing structure to prevent excessive breakage (fig. 4 and 5).
Feeding a continuous phase and a dispersed phase with certain flow rates from channels at two ends respectively, converging the continuous phase and the dispersed phase in a T-shaped micro-channel structure, generating droplets by the dispersed phase under the shearing action of the continuous phase, then breaking large droplets through a series connection domain-limiting structure, and converging partial micro droplets so as to regulate and control the size. The regulated and controlled mixed system flows out of the micro-channel chip through an outlet, the generation and the rupture process of the micro-bubbles are recorded through an external high-speed camera, and the formed photos of the micro-bubbles are processed and analyzed by software such as MATLAB, photoshop, image Pro and the like, so that the size distribution condition of the bubbles is obtained. The method is verified to be capable of continuously and controllably preparing a large number of micro bubbles.
The result shows that the structure provided by the method can effectively control the flow process, local velocity gradient and pressure difference are generated by utilizing the domain-limited structure, so that liquid drop extrusion, local stretching and unstable fracture are caused, the finally generated air bubbles have a target size range (figure 9) of more than 88 percent between 80 and 100 mu m, and the regulation and control of the size of the liquid drops can be effectively realized.
Comparative example 3: cross-shaped focusing structure for regulating bubble size in gas-liquid two-phase flow
The size of the liquid drop of the system in the embodiment 2 is regulated and controlled by using a cross-shaped structure, wherein the used materials are the same as those in the embodiment 2, and the materials, the processing mode, the driving, the connecting and the shooting equipment of the micro-channel are the same, and the difference is that the liquid drop generating system is changed into a structure that the fluid passes through a cross-shaped pipeline.
Controlling the flow of each phase by using a micro-injection pump, collecting and maintaining pictures after the flow is stable, performing liquid drop identification and size calculation by using a digital image processing technology at the later stage, and feeding back and optimizing operation parameters according to results until the size of the generated liquid drops is closest to a target condition.
The results show that the method only produces about 55% of bubbles in the size range of 80-100 μm (fig. 10), and the size distribution of the droplets fluctuates greatly, which shows that the method provided by the invention has obvious advantages.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.
Claims (10)
1. A device for regulating and controlling the size distribution of dispersed phases in a multiphase system, characterized by comprising an inlet channel (1), a limiting unit and an outlet channel (4) which are arranged in series, wherein the limiting unit comprises at least two limiting channels (2) and at least one intermediate channel (3) which are connected in series between the inlet channel (1) and the outlet channel (4) in turn in an alternating manner, and the flow cross-sectional area of the limiting channels (2) is smaller than that of the intermediate channel (3) at least at the positions where the limiting channels are connected with each other.
2. A device for regulating the size distribution of dispersed phases in a multiphase system according to claim 1, characterized in that the confinement channel (2) has a constant cross-sectional flow area over its extension.
3. The device for regulating the size distribution of dispersed phases in a multiphase system according to claim 2, wherein the extension length of the confinement passage (2) is not less than 10 times the maximum width dimension of the confinement passage (2), and/or the cross-sectional flow area of the confinement passage (2) is not more than 0.01mm 2 。
4. A device for regulating the size distribution of dispersed phases in a multiphase system according to claim 1, characterized in that the maximum width dimension of the confinement channels (2) does not exceed half the maximum width dimension of the intermediate channels (3).
5. Series confinement device for regulating the size distribution of dispersed phases in a multiphase system according to claim 1, characterised in that the cross-sectional flow area of the confinement passage (2) is smaller than the cross-sectional flow area of the inlet passage (1) and that at the location of the connection to the confinement unit the inlet passage (1) is tapered in the direction towards the confinement unit.
6. The device for regulating the size distribution of dispersed phases in a multiphase system according to claim 1, characterized in that the cross-sectional flow area of the outlet channel (4) increases in the direction away from the confinement unit.
7. The device for regulating the size distribution of dispersed phases in a multiphase system according to claim 6, wherein the outlet channel (4) extends diverging away from the confinement unit at the location where it meets the confinement unit; and/or the bottom of the outlet channel (4) is provided with a step downward step so that the flow cross-sectional area of the outlet channel (4) is increased gradually.
8. The device for regulating the size distribution of dispersed phases in a multiphase system according to claim 1, characterized in that it has a housing in which the inlet channel (1), the confinement channel (2), the intermediate channel (3) and the outlet channel (4) are formed along the same line.
9. The device of claim 8, wherein the housing is made of one or more of glass, metal, ceramic, alloy, polymer, and composite material.
10. A method for regulating the size distribution of dispersed phases in a multiphase system, comprising:
s1, material analysis and pretreatment, namely determining at least one material parameter of density, viscosity, surface tension and rheological property of a substance to be operated, and filtering a solution in the substance to be operated to remove impurities;
s2, according to the size of an expected dispersed phase and the determined material parameters, selecting a corresponding series connection limited domain device according to any one of claims 1 to 9, and connecting the series connection limited domain device in series to a fluid conveying control system;
s3, the fluid conveying control system is used for controlling the multiphase materials including the operated substances to flow into the inlet channel (1) and outputting the multiphase materials after the multiphase materials flow through the limited area unit and the outlet channel (4).
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| WO2015160919A1 (en) * | 2014-04-16 | 2015-10-22 | President And Fellows Of Harvard College | Systems and methods for producing droplet emulsions with relatively thin shells |
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