An electrostatic atomization nozzle and system based on electric field enhancement structure

Abstract

The invention discloses an electrostatic atomization nozzle based on an electric field enhancement structure and a system thereof, comprising a nozzle body of a regular polygon structure, wherein one end of the nozzle body is a spray end and the other end is a liquid injection end; the end face of the spray end is an attachment surface, and the corner between adjacent nozzle outer wall surfaces at the spray end is a nozzle tip; a liquid open channel is axially arranged on each nozzle outer wall surface of the spray end, the bottom end of the liquid open channel extends to the attachment surface, and a liquid outlet is arranged at the top end of each liquid open channel; a liquid injection cavity is axially arranged from the liquid injection end to the inside of the nozzle body; the bottom of the liquid injection cavity is connected to the outside of the nozzle body through the liquid outlet; the nozzle body is connected to a high voltage generator; since the charge density at the nozzle tip is concentrated, a jet is generated at each nozzle tip; therefore, the atomization flow rate can be increased and atomized droplets with good monodispersity and a wide jet area can be obtained at the same time.

Description

Technical Field

[0001] The invention belongs to the field of electrostatic atomization, and particularly relates to an electrostatic atomization nozzle based on an electric field enhancement structure and a system thereof. Background Art

[0002] Electrostatic atomization technology is a method that uses the electrostatic effect of a high-voltage electric field to achieve liquid fragmentation and atomization. The specific principle is that when the charged liquid flows out of the nozzle, the electrostatic shear stress acts on the liquid surface, overcoming the surface tension and viscosity of the liquid itself, thereby promoting the growth of liquid surface instability, causing the initial droplets to deform and break into smaller sub-droplets. Since electrostatic atomization can obtain a large number of charged micro-droplets with small particle size, good monodispersity, strong controllability, and high deposition rate with the advantage of low energy consumption, it has shown great application value in the fields of ultra-low-volume pesticide spraying, micro-nano film preparation, micro-combustion, micro-spray cooling, drug encapsulation, micro-power propulsion, and biomass spectrometry. Most of the existing electrostatic atomization nozzles operate in a cone jet mode. In this mode, the nozzle can only emit a jet. The size of the droplets is strictly limited by the supply flow rate, and the atomization flow rate cannot be further increased, which makes it difficult to meet the needs of practical applications of electrostatic atomization in multiple fields.

[0003] There are currently two main methods to increase the electrostatic atomization flow rate: integrating single capillary nozzles in an array or using a multi-jet mode of electrostatic atomization to achieve a doubling of the flow rate. The former is a method of increasing the atomization flow rate by arranging the nozzles in a linear or array manner and superimposing the number of nozzles, but this requires a relatively high laser etching method and processing cost. At the same time, the interference between adjacent sprays during operation will affect the deposition uniformity of the overall spray; the multi-jet mode can be regarded as a combination of multiple single-cone jets at the nozzle outlet to increase the atomization flow rate. This mode can be obtained at a higher charging voltage. However, in the multi-jet mode, a single jet will swing violently and it is difficult to maintain stability, affecting the monodispersity of the atomized droplets. At the same time, if the atomization voltage is too high, corona discharge is likely to occur, and the long-term stable operation of the equipment cannot be guaranteed. Therefore, the limitations of the above-mentioned methods to increase the atomization flow rate make it difficult for electrostatic atomization technology to be widely promoted and applied in many fields. Summary of the invention

[0004] In order to address the shortcomings of the prior art, the present invention proposes an electrostatic atomization nozzle and a system based on an electric field enhancement structure. The nozzle utilizes the electric field enhancement structure to generate stable multiple jets. On the basis of maintaining a wide stable voltage range, the atomization flow rate is greatly increased and atomized droplets with good monodispersity and a wide jet area can be obtained.

[0005] The technical solution adopted by the present invention is as follows:

[0006] An electrostatic atomizing nozzle based on an electric field enhancement structure comprises a nozzle body, which is a regular polygonal structure, one end of the nozzle body is an injection end, and the other end is an injection end; the end face of the injection end is an attachment surface, and the corner between adjacent nozzle outer wall surfaces at the injection end is the nozzle tip; a liquid open channel is axially arranged on each nozzle outer wall surface of the injection end, the bottom end of the liquid open channel extends to the attachment surface, and the top end of each liquid open channel is provided with a liquid outlet; an injection cavity is axially arranged from the injection end to the inside of the nozzle body; the bottom of the injection cavity is connected to the outside of the nozzle body through the liquid outlet; the nozzle body is connected to a high-voltage generator.

[0007] Furthermore, the liquid open channel is arranged along the axial center line of the outer wall surface of the nozzle.

[0008] Furthermore, the cross-sectional shape of the liquid open channel is designed to be an arc-shaped groove or a regular polygonal groove.

[0009] Furthermore, the cross-sectional shape of the liquid outlet is circular or polygonal.

[0010] Furthermore, the length of the liquid open channel L0 is the length of the nozzle body.

[0011] Furthermore, the nozzle body is made of metal material or alloy material.

[0012] An electrostatic atomization system using an electric field enhancement structure comprises a nozzle body, the injection end of the nozzle body is connected to a micro-injection pump through an infusion tube, and the micro-injection pump pumps the liquid to be atomized into the nozzle body; the nozzle body is connected to a high-voltage generator so that the nozzle body is charged, and since the charge density at the nozzle tip is concentrated, a jet is generated at each nozzle tip.

[0013] Furthermore, the output end of the high voltage generator is connected to the nozzle body through a wire, and the grounding end of the high voltage generator is connected to the ground electrode through a wire.

[0014] Furthermore, a collecting electrode is provided directly below the nozzle body. The height between the collecting electrode and the nozzle body may be 10-80 mm. The collecting electrode is made of a metal material or an alloy conductor.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention is an electrostatic atomizing nozzle based on an electric field enhancement structure. Since the exterior of the nozzle body is a regular polygonal structure, there are multiple edges and corners at the bottom of the spray end. When working, each edge and corner forms a nozzle tip. Therefore, the tip structure is conducive to the increase of local charge density and is more likely to generate multiple jets. At the same time, changing the position and number of the nozzle tip can guide the change of the spray direction and the adjustment of the number of jets, thereby achieving precise control of the atomization area and reducing the atomization voltage.

[0017] 2. During the electrostatic atomization process of the traditional flat-bottomed capillary nozzle, the liquid flowing out of the nozzle will be sucked back and attached to the outer wall of the capillary, and then fall into the curved liquid surface after falling due to gravity, resulting in a sudden change in the flow rate of a certain jet and an imbalance in force, which destroys the stability of the atomization. However, during operation, the electrostatic atomization nozzle with an electric field enhancement structure of the present application has the liquid to be atomized flowing in an orderly manner along the liquid open channel, without causing sudden changes in flow velocity and flow rate, effectively suppressing the liquid level fluctuation at the end of the nozzle and the instability of the jet.

[0018] 3. If Figure 8 After the tube diameter and flow rate of the traditional flat-bottom capillary nozzle are increased, axial and radial disturbances of the curved liquid surface are very likely to occur during the electrostatic atomization process, resulting in jet position shift and jet gap injection. The bottom of the electrostatic atomization nozzle with an electric field enhancement structure in the present application is closed to form an end attachment surface, which improves the adsorption capacity of the nozzle end for the liquid, suppresses the axial disturbance of the liquid surface, makes it easier for the large liquid cone to shrink and flatten to form a liquid film, and enhances the stability of multiple jets.

[0019] 4. In the charged multi-jet mode of the traditional flat-bottomed capillary, all jets will be ejected from the outer edge of the capillary needle, but the capillary nozzle wall is thin, the small liquid cone has a small attachment area, and the ability to resist liquid surface fluctuations and external disturbances is weak, resulting in a very small stable voltage range. However, under the electrostatic atomization nozzle with an electric field enhancement structure of the present application, the small liquid cone can be attached to the end plane, the attachment area is greatly increased, the adhesion of each jet is increased, the jet transfer is suppressed, and the stable voltage range is significantly improved.

[0020] 5. The electrostatic atomization nozzle with an electric field enhancement structure of the present application can operate stably in a multi-jet mode, which increases the capillary supply flow rate exponentially. There is no need for an array of integrated capillary nozzles, which reduces the difficulty and cost of processing. Under stable multi-jet conditions, the droplet size produced by each jet is several times smaller than the cone jet size under the same flow rate, which greatly reduces the particle size of the atomized droplets and thus improves the atomization quality. The jet atomization area is large and the angle is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the electrostatic atomization nozzle of the present invention;

[0022] Figure 2 A top view of the electrostatic atomization nozzle of the present invention;

[0023] Figure 3 It is a partial enlarged view of the liquid outlet of the present invention;

[0024] Figure 4 It is a partial enlarged view of the liquid open channel of the present invention;

[0025] Figure 5 A bottom view of the electrostatic atomizing nozzle of the present invention;

[0026] Figure 6 The electrostatic atomization system of the present invention;

[0027] Figure 7 It is a schematic diagram of the electrostatic atomization process of the present invention;

[0028] Figure 8 Schematic diagram of liquid surface fluctuation during atomization of a conventional flat-bottom nozzle;

[0029] In the figure, 1, nozzle tip, 2, liquid open channel, 3, liquid outlet, 4, nozzle outer wall, 5, nozzle body, 6, liquid injection port, 7, jet, 8, liquid injection cavity, 9, micro-injection pump, 10, syringe, 11, three-dimensional lifting platform, 12, high-voltage generator, 13, wire, 14, ground electrode, 15, collecting electrode, 16, infusion tube, 17, attachment surface; DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] like Figure 1-4 As shown, an electrostatic atomization nozzle based on an electric field enhancement structure includes a nozzle body 5, the nozzle body 5 is a regular polygon structure, that is, the outer wall surface of the nozzle body 5 is composed of a plurality of identical nozzle outer wall surfaces 4, one end of the nozzle body 5 is a spray end, and the other end is a liquid injection end. In this embodiment, the material of the nozzle body 5 is a conductor of a metal material or alloy, such as copper or stainless steel.

[0032] The end face of the nozzle body 5 at the injection end is the attachment surface 17, and the corner between the adjacent nozzle outer wall surfaces 4 at the injection end is the nozzle tip 1; a liquid open channel 2 is axially arranged on each nozzle outer wall surface 4 at the injection end, the bottom end of the liquid open channel 2 extends to the attachment surface 17, and the top end of each liquid open channel 2 is provided with a liquid outlet 3, and the cross-sectional shape of the liquid outlet 3 can be circular or polygonal; more specifically, the liquid open channel 2 is arranged along the axial midline of the nozzle outer wall surface 4, and the cross-sectional shape of the liquid open channel 2 can be designed as a semicircular groove or a regular polygonal groove designed radially inward, such as Figure 5 The liquid open channel 2 shown is a triangular groove; at the same time, the length of the liquid open channel 2 L0 is the length of the nozzle body 5;

[0033] The end surface of the injection end of the nozzle body 5 is an injection port 6, and an injection cavity 8 is axially arranged from the injection port 6 to the inside of the nozzle body 5; the injection cavity 8 can be a regular polygonal cavity similar to the nozzle body 5 or a cylindrical cavity; and the injection cavity 8 is coaxially arranged with the nozzle body 5. The bottom of the injection cavity 8 is connected to the outside of the nozzle body 5 through the liquid outlet 3; the nozzle body 5 is connected to the high voltage generator 12, so the charge density at the nozzle tip 1 of the nozzle body 5 is relatively concentrated, so a jet 7 is formed at the nozzle tip 1.

[0034] like Figure 6 An electrostatic atomization system using an electric field enhancement structure is shown, comprising a nozzle body 5, the injection end of the nozzle body 5 is connected to a micro-injection pump 9 through an infusion tube 16, and the micro-injection pump 9 pumps the liquid to be atomized into the nozzle body 5; the nozzle body 5 is connected to a high-voltage generator 12, so that the nozzle body 5 is charged, and the liquid to be atomized generates a jet 7 at the corner of the injection end of the nozzle body 5; the output end of the high-voltage generator 12 is connected to the nozzle body 5 through a wire 13, and the grounding end is connected to a ground electrode 14 through a wire; in this embodiment, a syringe 10 and a micro-injection pump 9 are used in combination; the nozzle body 5 is installed on a three-dimensional lifting platform 11, and a collecting electrode 15 is provided at 10-80 mm directly below the nozzle body 5. The collecting electrode 15 can be made of a metal material or an alloy conductor, such as copper or stainless steel, and the collecting electrode 15 is connected to the ground electrode 14 through a wire 13.

[0035] Combined with the electrostatic atomization nozzle based on the electric field enhancement structure and Figure 6 The working process of the electrostatic atomization system shown is further explained:

[0036] In this example, the nozzle body 5 is a regular hexagon, so the nozzle body 5 has 6 nozzle outer wall surfaces 4, and each nozzle outer wall surface 4 is provided with a liquid open channel 2; the liquid to be atomized, such as ethanol, is used as the atomizing medium, and the ethanol is loaded into the syringe 10, and the nozzle body 5 is located 15mm above the collecting electrode 15 by controlling the three-dimensional lifting platform 11, and the flow rate of the micro-injection pump 9 is adjusted to 30mL / h. The liquid to be atomized will enter the nozzle body 5 from the injection port 6 through the infusion tube 16, and then the liquid to be atomized will flow out from the 6 liquid outlets 3 of the nozzle outer wall surface 4, and will be delivered to the attachment surface 17 along the liquid open channel 2, and then accumulate and fall by gravity, presenting a drop-shaped pattern.

[0037] Turn on the negative high voltage generator 12 and gradually increase the voltage, the droplet dripping speed will increase, then switch to the cone jet mode, continue to increase the voltage to 12.21kV, the large liquid cone will gradually shrink and flatten, and generate a jet 7 at the nozzle tip 1 where the charge density is relatively concentrated, forming a stable six-stream jet, such as Figure 7As shown in the figure, since the liquid surface does not fluctuate in the stable multi-stream mode, the jet 7 is absolutely stable, so a large number of charged micro-droplets with small particle size, good monodispersity, strong controllability and high deposition rate can be continuously obtained.

[0038] During the whole process, the atomized liquid flows in an orderly manner along the liquid open channel 2 without sudden changes in flow velocity and flow rate; the attachment surface 17 effectively suppresses the up and down jumping of the liquid surface and enhances the adsorption force of the liquid surface. The large liquid cone is more likely to shrink and flatten to form a liquid film, reducing liquid surface fluctuations and jet instability; at the same time, the small liquid cone can be attached to the attachment surface 17, and the attachment area is greatly increased, which increases the adhesion of each jet and suppresses the jet transfer, thereby ensuring that the electrostatic atomization operates in a stable multi-jet mode.

[0039] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. An electrostatic atomization nozzle based on an electric field enhancement structure, characterized in that: The nozzle body (5) comprises a nozzle main body (5), the nozzle main body (5) is a regular polygonal structure, one end of the nozzle main body (5) is a spray end, and the other end is a liquid injection end; the end surface of the spray end is an attachment surface (17), and the corner between adjacent nozzle outer wall surfaces (4) at the spray end is a nozzle tip (1); a liquid open channel (2) is axially provided on each nozzle outer wall surface (4) of the spray end, the bottom end of the liquid open channel (2) extends to the attachment surface (17), and the top end of each liquid open channel (2) is provided with a liquid outlet (3); a liquid injection cavity (8) is axially provided from the liquid injection end to the inside of the nozzle main body (5); the bottom of the liquid injection cavity (8) is connected to the outside of the nozzle main body (5) through the liquid outlet (3); The nozzle body (5) is connected to a high-voltage generator (12); The liquid open channel (2) is arranged along the axial midline of the nozzle outer wall surface (4); The cross-sectional shape of the liquid open channel (2) is designed to be an arc-shaped groove or a regular polygonal groove; The length of the liquid open channel (2) is L=1 / 3L0 to 1 / 2L0, where L0 is the length of the nozzle body (5); The cross-sectional shape of the liquid outlet (3) is circular or polygonal; Working process: the nozzle body (5) is a regular hexagon, so the nozzle body (5) has 6 nozzle outer wall surfaces (4), and each nozzle outer wall surface (4) is provided with a liquid open channel (2); the liquid to be atomized, such as ethanol, is used as the atomizing medium, and the ethanol is loaded into the syringe (10), and the nozzle body (5) is located 15 mm above the collecting electrode (15) by controlling the three-dimensional lifting platform (11), and the flow rate of the micro-injection pump (9) is adjusted to 30 mL / h; The atomized liquid will enter the nozzle body (5) through the liquid infusion tube (16) from the liquid injection port (6), and then flow out from the six liquid outlets (3) on the outer wall (4) of the nozzle, and be delivered to the attachment surface (17) along the liquid open channel (2), where it will accumulate and fall due to gravity, presenting a drop-shaped pattern; The negative high voltage generator (12) is turned on and the voltage is gradually increased, and the droplet dripping speed is accelerated. Then, the mode is switched to the cone jet mode, and the voltage is further increased to 12.21 kV. The large liquid cone will gradually shrink and flatten, and a jet (7) will be generated at the nozzle tip (1) where the charge density is relatively concentrated, forming six stable jets. Since the liquid surface does not fluctuate in the stable multi-stream mode, the jet (7) is absolutely stable, so a large number of charged micro-droplets with small particle size, good monodispersity, strong controllability and high deposition rate are continuously obtained. During the whole process, the atomized liquid flows in an orderly manner along the liquid open channel (2) without causing sudden changes in flow velocity and flow rate; the attachment surface (17) effectively suppresses the up and down jumping of the liquid surface and enhances the adsorption force of the liquid surface, and the large liquid cone is more likely to shrink and flatten to form a liquid film, thereby reducing liquid surface fluctuations and jet instability; at the same time, the small liquid cone is attached to the attachment surface (17), and the attachment area is greatly increased, which increases the adhesion force of each jet and suppresses jet transfer, thereby ensuring that the electrostatic atomization operates in a stable multi-jet mode.

2. The electrostatic atomization nozzle based on the electric field enhancement structure according to claim 1, characterized in that: The nozzle body (5) is made of metal material.

3. An electrostatic atomization system equipped with an electrostatic atomization nozzle based on an electric field enhancement structure as claimed in claim 1, characterized in that: The nozzle body (5) comprises a nozzle body (5), wherein the injection end of the nozzle body (5) is connected to a micro-injection pump (9) via an infusion tube (16), and the micro-injection pump (9) pumps liquid to be atomized into the nozzle body (5); the nozzle body (5) is connected to a high-voltage generator (12), so that the nozzle body (5) is charged, and since the charge density at the nozzle tip (1) is concentrated, a jet (7) is generated at each nozzle tip (1); The output end of the high voltage generator (12) is connected to the nozzle body (5) through a wire (13), and the grounding end of the high voltage generator (12) is connected to a ground electrode (14) through a wire (13); A collecting electrode (15) is arranged directly below the nozzle body (5). The height between the collecting electrode (15) and the nozzle body (5) is 10-80 mm. The collecting electrode (15) is made of a conductor of metal material.

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