CN113560058B - Array integrated electrostatic atomization device capable of stabilizing multiple jet flow modes and experimental system - Google Patents

Abstract

The invention discloses an array integrated electrostatic atomization device and an experimental system for stabilizing a multi-strand jet mode, wherein the array integrated electrostatic atomization device comprises a plurality of flat capillary nozzles and double-layer crossed space shielding electrodes, and the double-layer crossed space shielding electrodes comprise cylindrical wall-shaped electrodes and electrodes; the bottom of the cylindrical wall-shaped electrode is arranged at the upper part of the electrode and is in one-to-one correspondence with the through holes on the electrode; the input end of the plain capillary nozzle is connected with the liquid injection unit, the output end of the plain capillary nozzle is arranged at the central position of the cylindrical wall-shaped electrode, and the end part of the output end is kept flush with the bottom edge of the cylindrical wall-shaped electrode; the plain end capillary nozzle is connected with a negative high-voltage direct-current power supply; applying the array integrated electrostatic atomization device to an electrostatic atomization test; the stability of single-capillary multi-strand jet atomization is enhanced by using a double-layer crossed space shielding electrode and a plain capillary.

Description

A stable multi-jet mode array integrated electrostatic atomization device and experimental system

technical field

The invention belongs to the field of electrostatic atomization, and in particular relates to an array-integrated electrostatic atomization device and an experimental system with a stable multi-jet mode.

Background technique

Electrospray (ES) technology is an atomization technology that can produce a large number of charged droplets with extremely low energy consumption. The main principle of this technology is to weaken the surface tension of the liquid flowing out of the nozzle and break it up by the electrostatic action of an external electric field. Compared with the traditional mechanical atomization method, the droplets generated by electrostatic spray have significant advantages such as small particle size, good monodispersity, and good controllability, which have been shown in many fields such as film preparation, inkjet printing, and biopharmaceuticals. huge application potential.

In recent years, the related research and application of electrostatic atomization mainly focus on the cone jet mode, because this mode can stably generate fine atomized droplets with good monodispersity. However, when electrostatic atomization is operated in this mode, there is a highly positive power-law relationship between the particle size of the generated droplets and the flow rate of the liquid supply. This means that to obtain micro/nano-scale atomized droplet populations in this mode, the supply flow must be limited to an extremely small order. This feature largely limits the production of atomized droplets when electrostatic spraying is used in industrial applications. The research on multi-jet mode and its integration provides a new solution for breaking through the flow bottleneck of electrostatic atomization. In the multi-jet mode, the supply flow rate can be greatly increased, while the size of the generated droplets can still be maintained at the micro/nano scale. On this basis, if the nozzles are integrated in an array, that is, the number of nozzles is superimposed and arranged in a certain way, and operated in a multi-jet mode, the output of atomized droplets can be further greatly improved.

At present, the main drawback of electrostatic spray operating in multi-jet mode is its poor stability. When using an array integrated nozzle to operate in a multi-jet mode, the jets of adjacent nozzles will also produce voltage edge effects due to the existence of spray current, which interferes with each other. In general, the instability of the multi-jet mode affects the characteristics such as the monodispersity of the generated droplets, which is the main technical bottleneck limiting its application in the field of industrial production.

SUMMARY OF THE INVENTION

According to the deficiencies and defects of the prior art, the present invention proposes a stable multi-jet mode array integrated electrostatic atomization device and experimental system, designs a detachable double-layer cross-space shielding electrode, and manufactures it based on 3D printing technology A new type of flat capillary is used to enhance the stability of single-capillary multi-jet atomization. At the same time, a plexiglass plate is used to fix the microchannel unit and shield electrodes, thereby integrating the atomizing nozzle and eliminating the voltage between adjacent microchannel outlets. edge effects. The device combines the advantages of the cone jet mode and the multi-jet mode, and has the advantages of large supply flow, small device volume, low cost and high stability, which can effectively improve the current array integrated atomization device operating in the multi-jet mode. Stability and monodispersity and yield of generated atomized droplets.

The technical scheme adopted in the present invention is as follows:

An array-integrated electrostatic atomization device with a stable multi-jet mode, comprising a plurality of flat capillary nozzles and a double-layer cross-space shielding electrode, wherein the double-layer cross-space shield electrode includes a cylindrical wall electrode and an electrode; There are through holes, and the bottom of the cylindrical wall-shaped electrode is installed on the upper part of the electrode and corresponds to the through holes on the electrode one by one; the input end of the flat capillary nozzle is connected to the liquid injection unit, and the output end of the flat capillary nozzle is set at The central position of the cylindrical wall-shaped electrode, and the end of the output end is kept flush with the bottom edge of the cylindrical wall-shaped electrode; the flat capillary nozzle is connected to a negative high-voltage direct current power supply.

Further, the inside of the flat capillary nozzle is a circular through hole, and the inner diameter of the through hole is between 0.2 mm and 0.5 mm.

Further, the outside of the flat capillary nozzle is a uniform cylindrical shape, and the outer diameter is between 0.8 and 1.0 mm.

Further, the outer wall of the jetting end of the flat capillary nozzle is configured in a conical shape.

Further, a hydrophobic coating is applied to the outer face of the spray tip.

Further, the cylindrical wall-shaped electrode material is red copper, and the electrode material is red copper.

Further, the array-integrated electrostatic atomization device includes a fixed plate, an adjustment plate and a support plate, the fixed plate and the adjustment plate are arranged in parallel, and the support plate is arranged between the fixed plate and the adjustment plate; the adjustment plate is provided with a mounting hole, The cylindrical wall electrodes are arranged in the installation holes one by one, and the electrodes are attached and installed on the bottom of the adjustment plate and are connected to the bottom edge of each cylindrical wall electrode.

Further, the electrodes are copper foil patch electrodes.

An array-integrated electrostatic atomization experimental system with a stable multi-jet mode includes a liquid injection unit, an array-integrated electrostatic atomization device, a ground electrode and an information acquisition unit; the input end of the flat capillary nozzle in the array-integrated electrostatic atomization device is connected to a liquid Injection unit; the ground electrode is arranged below the flat capillary nozzle, and the ground electrode is grounded; the information collection unit includes an LED cold light source and a camera, the LED cold light source illuminates the atomization area between the flat capillary nozzle and the ground electrode, and the camera collects the fog The experimental images in the area of the transformation.

Further, the ground electrode is used as a positive electrode and corresponds to the flat capillary nozzle of the negative electrode, and the distance between the ground electrode and the flat capillary nozzle is kept at 20 mm.

Beneficial effects of the present invention:

1. For the capillary nozzle micro-channel used in this device, through reasonable nozzle design and working condition setting, a single nozzle can achieve stable multi-jet electrostatic spraying. Compared with the conventional cone jet mode, the multi-jet mode atomized jet generated by this device not only ensures a large supply flow, but also expands the stable operation range of the multi-jet mode, and maintains a good quality of atomized droplets. properties, which have important implications for the practicality of multi-jet electrostatic atomization.

2. In order to solve the influence of the voltage edge effect between each capillary micro-nozzle of the array nozzle device, a double-layer cross-space shielding electrode made of red copper is designed. The device has simple assembly and low cost, and eliminates the voltage edge effect between adjacent nozzles, so that the jets generated by each nozzle do not interfere with each other. In addition, the electrode shielding device also realizes the limitation of the spray cone angle of multiple jets, which can collect the generated droplets in a smaller space.

3. By further improving the integration degree of the array-integrated atomizing device of the present invention, the supply flow can be doubled, and the output of atomized droplets can be greatly increased accordingly. At the same time, the average diameter and size distribution of the generated atomized droplets can maintain good properties similar to those of the droplets generated in the cone jet mode, and will not change significantly with the increase of the integration degree. This not only realizes large-flow droplet production in the multi-jet mode, but also expands the stable operation range, and has the advantages of stable atomization process, convenient operation, and good droplet properties in the cone-jet mode. This is the traditional It is difficult to achieve by atomization methods and ordinary nozzle devices.

Description of drawings

1 is a schematic structural diagram of an array-integrated electrostatic atomization device with a stable multi-jet mode of the present invention;

Fig. 2 is the schematic diagram of the partial two-dimensional structure of the flat capillary in the present invention;

Fig. 3 is the double-layer intersection space shielding electrode in the present invention;

Fig. 4 is the electrostatic atomization experimental device of the present invention;

Fig. 5 is the evolution diagram of multi-jet electrohydrodynamic atomization morphology under different integration devices;

Fig. 6 is the operating domain of microchannel electrohydrodynamic jet atomization;

Fig. 7 is the applied voltage interval required to form and maintain stable multi-jet mode operation under different array integrated microchannel devices;

Fig. 8 is the variation of the average size of droplets generated by the formation of a stable multi-jet pattern with the supply flow rate under the same array integrated microchannel device.

In the figure, 1. Flat capillary nozzle, 2. Fixed plate, 3. Support plate, 4. Cylindrical wall electrode, 5. Adjustment plate, 6. Electrode, 7. Micro syringe pump, 8. Syringe, 9. Negative high pressure DC power supply, 10, camera, 11, LED cold light source, 12, grounding plate, 13, infusion tube, 14, lead wire, 15, ground pole.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

As shown in FIG. 1 , an array-integrated electrostatic atomization device with stable multi-jet mode includes multiple flat capillary nozzles 1 , a double-layer cross-space shielding electrode, a fixed plate 2 , a support plate 3 and an adjustment plate 5 . The fixed plate 2 , the support plate 3 and the adjustment plate 5 are all made of plexiglass. The double-layer cross space shielding electrode includes a cylindrical wall electrode 4 and an electrode 6; a through hole is opened on the electrode 6, and the bottom of the cylindrical wall electrode 4 is installed on the upper part of the electrode 6 and is connected with the through hole on the electrode 6. One-to-one correspondence; the input end of the flat capillary nozzle 1 is connected to the liquid injection unit, the output end of the flat capillary nozzle 1 is set at the center of the cylindrical wall electrode 4, and the end of the output end is kept in the cylindrical wall shape. The bottom edge of the electrode 4 is flush; the flat capillary nozzle is connected to a negative high voltage DC power supply 9 .

The inside of the flat capillary nozzle 1 is a circular through hole, and the inner diameter of the through hole is between 0.2 mm and 0.5 mm. The outside of the flat capillary nozzle 1 is a uniform cylindrical shape, and the outer diameter is between 0.8 and 1.0 mm. In order to increase the adhesion area of the liquid cone at the nozzle outlet, thereby enhancing the stability of the atomized jet to resist external disturbances, and to ensure the monodispersity of the atomized droplets generated, the outer wall of the spray end of the flat capillary nozzle 1 is set to a conical shape. , the outer diameter of the bottom of the flat capillary nozzle 1 is controlled at 1.7 to 2.0mm, and the transition is uniform; and an inner inclined annulus is formed between the conical end and the inner pipe, and the position of the lower outlet of the inner circular hole of the flat capillary is connected to the lower outer end annulus. The vertical distance is 0.2 mm; the total length of the flat capillary nozzle 1 is controlled at 30 to 40 mm.

As shown in FIG. 3 , the cylindrical wall electrode 4 is made of red copper, the outer diameter is 8 mm, the inner diameter is 7 mm, the thickness is 0.5 mm, and the height is 5 mm. The electrode 6 is made of red copper, the size is 35mm×35mm, and the thickness is 1mm. The diameter of the circular through hole on the electrode 6 is 8mm. When assembling the cylindrical wall electrode 4 and the electrode 6, the lower end of the cylindrical wall electrode 4 needs to be flush with the lower end surface of the circular through hole on the electrode 6, that is, the double-layer intersecting space shielding electrode in the present invention is obtained.

In order to realize the fixing of the flat capillary nozzle 1 , the flat capillary nozzle 1 is fixed by the fixing plate 2 , the adjusting plate 5 and the supporting plate 3 . Specifically, the fixed plate 2 and the adjustment plate 5 are arranged in parallel, and the support plate 3 is arranged between the fixed plate 2 and the adjustment plate 5; the adjustment plate 5 is provided with installation holes, and the cylindrical wall electrodes 4 are arranged in the installation holes one by one , and the electrode 6 is attached to the bottom of the adjustment plate 5 and connected to the bottom edge of each cylindrical wall-shaped electrode 4; the electrode 6 is a copper foil patch electrode.

As shown in Figure 4, an experimental system applied to the above-mentioned stable multi-jet mode array integrated electrostatic atomization device includes a micro-injection pump 7, a syringe 8, a negative high-voltage DC power supply 9, a camera 10, and an LED cold light source 11. , a grounded circular copper plate, an infusion tube 13 , a wire 14 and a ground pole 15 . The flat capillary nozzle 1 is connected to the syringe 7 containing the working fluid through the infusion tube 13, and passes through the cylindrical wall electrode 4 and the electrode 6 to weaken the voltage edge effect between adjacent capillaries. The syringe 7 is controlled by a micro-injection pump, which supplies the working fluid at a fixed flow rate, and is evenly distributed to each capillary nozzle through an infusion tube of the same program. The voltage of the negative high voltage DC power supply 9 is output to the flat capillary nozzle 1 through the wire 14 , so that the nozzle becomes the negative electrode, and the grounded circular copper plate is connected to the ground electrode 15 through the wire 14 . The grounded circular copper plate is used as the positive electrode, and the nozzle corresponding to the negative electrode is located 20mm below the nozzle 1. The LED cold light source 11 will illuminate the atomized area between the grounded circular copper plate 12 and the flat capillary nozzle 1 , and the camera 10 will capture experimental images.

Be further explained below in conjunction with the working process of the present invention:

Under the conditions of an ambient temperature of 25±0.5°C and a relative humidity of 40%±2.5%, the atomized absolute ethanol is loaded into the syringe 8 and installed and calibrated on the micro-flow syringe pump 7, and the total supply flow is controlled to 20- 200 μL/min. The working fluid flows to the nozzle 1 through the infusion pipe 13, forms a jet at the tip of the nozzle, and is broken under the influence of negative high pressure. With the increase of the applied voltage, the atomized jet gradually evolves from a droplet mode to a cone jet mode, and finally to a multi-jet mode.

In order to illustrate the effect of the array-integrated electrostatic atomization device of the present invention, the array-integrated atomization device of the present invention was replaced with a single capillary microchannel and an array-integrated atomization device with a higher degree of integration, and a comparative experiment was carried out, as shown in the following figure.

In Figure 5, under the single capillary micro-channel atomization device in Figure 5(a), the initial voltage for forming a multi-jet mode is small (about 4.5kV), and a stable multi-jet mode appears when the voltage is increased to around 5kV. The number of stable jet strands increases with the increase of the applied voltage. After reaching a certain critical value (about 6kV), the jet loses its stability and becomes a disordered multi-strand jet mode. It can be seen that under the single capillary microchannel device, the stable operating range of the multi-jet mode is less than 1kV.

As shown in Fig. 5(b), in the array-integrated atomization device, the initial voltage for forming the multi-jet mode is about 5 kV, which is higher than that in the single-capillary microchannel device. When the voltage is increased to 8kV, a stable multi-jet appears, and it becomes unstable until the voltage is increased to around 10kV.

As shown in Fig. 5(c), the initial voltage for forming the multi-jet mode is also about 5kV, while the stable multi-jet appears only when the applied voltage is 10kV, and the applied voltage can be continuously increased to about 12kV. just started to become unstable.

In summary, the array integrated atomization device can form a stable multi-jet while multiplying the supply flow, and can correspondingly increase the atomization output, while increasing the operating range of the stable multi-jet (about 2kV). ), and does not change with the increase in integration. In addition, the number of jet strands in the formation of stable multi-jet atomization under the array-integrated microchannel atomization device does not change with the increase of the applied voltage, which is different from the situation under the single capillary microchannel atomization device.

In Fig. 6, CJa indicates that the cone jet begins to appear, CJv indicates that the cone jet disappears, MJa indicates that the multiple jets on the meniscus begin to appear, EMJa indicates that the edge multiple jets begin to appear, SMJv indicates that the stable multiple jets disappear, and SMJ indicates that the stable multiple jets disappear. . The lowermost cone jet has a narrower stable operation area, and the uppermost stable multi-jet (ie, the edge multi-jet mode) has the widest operation area.

SMJ _onset and SMJ _offset in Fig. 7 represent the critical applied voltages corresponding to the formation and disappearance of the stable multi-jet atomization state, respectively. It can be seen from the figure that the initial applied voltage required to form stable multiple jets under different array integrated microchannel atomization devices and the corresponding critical applied voltage when the steady state disappears will increase with the increase of the supply flow. However, under the same array-integrated microchannel device, the size of the stable operating voltage interval basically does not change with the increase of the supply flow. All in all, the supply flow rate and stable operating voltage range of the stable multi-jet mode under the single-capillary micro-channel atomization device are significantly improved compared with the cone-jet mode, but the stable multi-jet formed under the array-integrated micro-channel atomization device can Further increase the supply flow and stabilize the operating voltage range.

It can be seen from Figure 8 that the average size of the droplets formed by the formation of stable multi-jet atomization in the array integrated microchannel system is only affected by the supply flow of a single capillary microchannel, and will not lead to an increase in the overall supply flow due to the increase in integration. The lift causes a change in the average size of the droplets. The average size of droplets formed by stable multi-jet atomization under the array-integrated microchannel device shows a nonlinear growth trend with the increase of the overall supply flow, and its growth rate decreases with the increase of the supply flow. It is very beneficial to increase the overall atomization flow rate. Under the condition of (Qv=50μL/min), the peak value of the volume distribution of the atomized droplet size under the single capillary microchannel device is about 19%, and the corresponding droplet size is around 6μm. The peaks of the volume distribution of droplet particle size under the device are around 17% and 14%, respectively, and the corresponding droplet sizes are all around 7.5 μm. It can be seen that the peak value of the volume distribution of droplet particle size under the microchannel array integrated device will slightly decrease with the increase of the integration degree, but the droplet size corresponding to the maximum volume distribution is basically unchanged, and the droplet particle size The diameter distribution range slightly increases with the increase of the integration degree. These changes are caused by the increase of the overall supply flow, which leads to the increase of the applied voltage required to form a stable multi-jet atomization.

Figure 8(b) shows that the droplet size corresponding to the cumulative volume distribution of atomized droplet size reaching 100% under the single capillary microchannel device is smaller than that under the dual capillary and four capillary microchannel array integrated devices, but The improvement of the integration degree has no obvious effect on the cumulative volume distribution of droplet size.

This shows that the array-integrated microchannel device can multiply the supply flow rate with the improvement of the integration degree while keeping the particle size distribution of the atomized droplets almost unchanged.

The above embodiments are only used to illustrate the design ideas and features of the present invention, and the purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made according to the principles and design ideas disclosed in the present invention fall within the protection scope of the present invention.

Claims (6)

1. An array integrated electrostatic atomization device for stabilizing a multi-strand jet flow mode is characterized by comprising a plurality of plain end capillary nozzles (1) and double-layer crossed space shielding electrodes, wherein the double-layer crossed space shielding electrodes comprise cylindrical wall-shaped electrodes (4) and electrodes (6); the electrode (6) is provided with through holes, the bottom of the cylindrical wall-shaped electrode (4) is arranged at the upper part of the electrode (6) and is in one-to-one correspondence with the through holes on the electrode (6); the input end of the plain capillary nozzle (1) is connected with a liquid injection unit, the output end of the plain capillary nozzle (1) is arranged at the central position of the cylindrical wall-shaped electrode (4), and the end part of the output end is kept flush with the bottom edge of the cylindrical wall-shaped electrode (4); the plain end capillary nozzle is connected with a negative high-voltage direct-current power supply (9); the outer wall of the spraying end of the plain capillary nozzle (1) is conical, and an inner inclined ring surface is formed between the conical end and the inner pipeline; a hydrophobic coating is made on the outer surface of the spraying end;

the cylindrical wall-shaped electrode (4) is made of red copper, and the electrode (6) is made of red copper;

the array integrated electrostatic atomization device comprises a fixing plate (2), an adjusting plate (5) and a supporting plate (3), wherein the fixing plate (2) and the adjusting plate (5) are arranged in parallel, and the supporting plate (3) is arranged between the fixing plate (2) and the adjusting plate (5); the adjusting plate (5) is provided with mounting holes, the cylindrical wall electrodes (4) are arranged in the mounting holes one by one, and the electrodes (6) are attached to the bottom of the adjusting plate (5) and connected with the bottom edge of each cylindrical wall electrode (4).

2. The integrated electrostatic atomization device of an array of stable multi-jet patterns according to claim 1, wherein the flat capillary nozzle (1) is internally a circular through hole with an inner diameter between 0.2mm and 0.5 mm.

3. The integrated electrostatic atomizer of an array of stable multi-jet modes according to claim 2, wherein said plain capillary nozzle (1) is of uniform cylindrical shape externally with an outer diameter of between 0.8 and 1.0 mm.

4. The integrated electrostatic atomization device of an array of stable multi-jet modes of claim 1, wherein the electrodes (6) are copper foil patch electrodes.

5. An array integrated electrostatic atomization experimental system applying the array integrated electrostatic atomization device according to claim 1, characterized in that the liquid injection unit, the array integrated electrostatic atomization device, the grounding electrode and the information acquisition unit are included; the input end of a plain end capillary nozzle (1) in the array integrated electrostatic atomization device is connected with a liquid injection unit; the grounding electrode is arranged below the plain end capillary nozzle (1) and is grounded; the information acquisition unit comprises an LED cold light source (11) and a camera (10), the LED cold light source (11) irradiates towards an atomization area between the plain end capillary nozzle (1) and the grounding electrode, and the camera (10) acquires an experimental image in the atomization area.

6. The system for the array integrated electrostatic atomization experiment of the stable multi-jet mode according to claim 5, wherein the grounding electrode is used as a positive electrode, the flat capillary nozzle (1) corresponding to a negative electrode, and the distance between the grounding electrode and the flat capillary nozzle (1) is kept at 20 mm.

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