CN112888130B - Low-temperature plasma generating device and method for fruit and vegetable fresh-keeping - Google Patents

Abstract

The present application discloses a low-temperature plasma generating device and method for fresh-keeping fruits and vegetables, which are used to solve the problem that the existing devices using low-temperature plasma for sterilizing fruits and vegetables cannot efficiently and stably generate low-temperature plasma. The device includes: a low-temperature plasma generation module; the low-temperature plasma generation module includes a blocking medium plate, a diamond-shaped mesh electrode, and a flat electrode; the first surface of the diamond-shaped mesh electrode is in contact with the first side surface of the blocking medium plate, and the first surface of the flat electrode The surface is in contact with the second side surface of the blocking dielectric plate; wherein, the first diagonal lengths of the several diamond meshes included in the rhombic mesh electrode are all 1 mm, and the second diagonal lengths are both 2 mm; the blocking dielectric plate is made of nitrogen Aluminum AlN. In the present application, by selecting a barrier dielectric plate made of AlN material and a diamond mesh electrode with a rhombus grid diagonal of 1 mm×2 mm, it is ensured that the low temperature plasma generator can efficiently and stably generate low temperature plasma.

Description

A low-temperature plasma generating device and method for fresh-keeping fruits and vegetables

technical field

The present application relates to the technical field of preservation of fruits and vegetables, and in particular, to a low-temperature plasma generating device and method for preservation of fruits and vegetables.

Background technique

Compared with the traditional fruit and vegetable preservation technology, the application of low-temperature plasma for fruit and vegetable preservation is a non-thermal processing technology that has emerged in recent years. , inhibiting the metabolism of fruits and vegetables, has the advantages of high efficiency, no pollution, no residue, no heat damage, obvious bacteriostatic effect, etc., and the application prospect is very good.

In recent years, with the rise of the application of low-temperature plasma for fruit and vegetable preservation, many devices that use low-temperature plasma for fruit and vegetable sterilization have appeared. The structure is complex, the electrode area utilization rate is low, and the low-temperature plasma cannot be efficiently and stably generated.

SUMMARY OF THE INVENTION

The embodiments of the present application provide a low-temperature plasma generating device and method for fresh-keeping fruits and vegetables, which are used to solve the problem that the existing devices using low-temperature plasma for sterilizing fruits and vegetables cannot efficiently and stably generate low-temperature plasma.

On the one hand, an embodiment of the present application provides a low-temperature plasma generating device for fresh-keeping fruits and vegetables, the device includes: a low-temperature plasma generating module; the low-temperature plasma generating module includes a blocking medium plate, a diamond-shaped mesh electrode, and a flat electrode; The first surface of the mesh electrode is in contact with the first side surface of the blocking medium plate, and the first surface of the flat electrode is in contact with the second side surface of the blocking medium plate; wherein, the diamond-shaped mesh electrode includes a plurality of diamond-shaped meshes, and the The length of the first diagonal is 1 mm, and the length of the second diagonal of the plurality of rhombus grids is 2 mm; the material of the blocking medium plate is aluminum nitride AlN.

The embodiment of the present application provides a low-temperature plasma generating device for fruit and vegetable preservation. By selecting a diamond-shaped mesh electrode as the electrode structure of the low-temperature plasma generating module, the low-temperature plasma generating device can efficiently and stably generate low-temperature plasma. ; This is because the perimeter of the diamond mesh is the largest when the mesh area is constant, so the selection of the diamond mesh electrode can maximize the discharge area. By further selecting the material of the blocking dielectric plate as aluminum nitride (AlN), the diagonal size of several rhombus meshes included in the rhombus mesh electrode is 1mm×2mm, which ensures the mechanical strength of the low-temperature plasma generation module and reduces the occurrence of low-temperature plasma. The heat generation of the module discharge increases the heat dissipation performance, reduces the degree of thermal expansion, and also maximizes the efficiency of the low-temperature plasma generator to generate low-temperature plasma, so that the low-temperature plasma generator can better kill and adhere to the surface of fruits and vegetables. The microorganisms can degrade the ethylene gas synthesized by fruits and vegetables, inhibit the metabolism of fruits and vegetables, and make fruits and vegetables get better fresh-keeping effect.

In an implementation manner of the present application, the material of the diamond mesh electrode is AgCu28; the material of the flat electrode is AgCu28.

In the examples of this application, the AgCu28 electrical contact material is innovatively used to make the rhombus mesh electrode and the plate electrode. The characteristics are very suitable for the application requirements of the embodiments of the present application; in addition, since the melting point of the AgCu28 electrical contact material is lower than that of any component in silver or copper, it is also easier to process.

In an implementation of the present application, the shape of the diamond-shaped mesh electrode is the same as the shape of the plate electrode; the area of the first surface of the diamond-shaped mesh electrode is equal to the area of the first surface of the plate electrode; the first surface of the diamond-shaped mesh electrode The corresponding contact position on the first side of the blocking medium plate and the corresponding contact position of the first surface of the flat electrode on the second side of the blocking medium plate are symmetrical with respect to the blocking medium plate.

The contact position of the diamond mesh electrode and the flat electrode in the embodiment of the present application is symmetrical with respect to the blocking dielectric plate, and the symmetrical contact position can make the discharge occur earlier, the current pulses are more dense, the discharge power is larger, the transfer charge is more, and the low temperature plasma The energy is higher and the activity is stronger, so that the low-temperature plasma generating device can generate low-temperature plasma more efficiently, so as to improve the effect of preserving fresh fruits and vegetables.

In an implementation manner of the present application, the contact mode between the first surface of the diamond-shaped mesh electrode and the first side surface of the blocking dielectric plate is PCB printing; and, the contact between the first surface of the flat electrode and the second side surface of the blocking dielectric plate is The contact mode is PCB printing; electrode welding points are provided on the diamond mesh electrodes, and electrode welding points are provided on the flat electrodes; wherein, the electrode welding points are used to connect the low-temperature plasma generating module and the voltage supplying module.

In the embodiment of the present application, PCB printing is used to realize the contact between the diamond-shaped mesh electrode and the blocking medium plate, as well as the flat electrode and the blocking medium plate, and the electrodes are directly bonded to the surface of the blocking medium plate at high temperature, which greatly reduces the contact between the diamond-shaped mesh electrode and the blocking medium plate. The degree of uneven contact between the blocking medium plate and the flat electrode and the blocking medium plate effectively solves the problem of local overheating and rupture of the blocking medium plate due to uneven contact.

In an implementation manner of the present application, the second surface of the diamond-shaped mesh electrode is covered with an insulating anti-corrosion layer; the second surface of the flat electrode is covered with an insulating anti-corrosion layer.

In the embodiment of the present application, the surface of the diamond electrode and the flat electrode is covered with an insulating anti-corrosion layer, which effectively avoids the possibility of the exposed surface of the diamond electrode and the flat electrode being ablated and oxidized during the discharge process, and enhances the corrosion resistance of the low-temperature plasma generation module. durability, wear resistance and stability, extending the service life of the low temperature plasma generator.

In an implementation manner of the present application, the second surface of the flat electrode is further covered with a thermally conductive plate.

In the embodiment of the present application, in order to further enhance the heat dissipation capability of the low-temperature plasma generating device, improve the stability and service life of the low-temperature plasma generating device, and increase the discharge uniformity of the low-temperature plasma generating module, a heat-conducting plate is installed under the surface of the flat electrode. .

In an implementation manner of the present application, the grid line width of the diamond-shaped mesh electrode is 0.3 mm; the thickness of the blocking medium plate is 0.5 mm.

In an implementation manner of the present application, the device further includes a voltage supply module; the voltage supply module includes a power supply and a booster circuit; the power supply is connected to the booster circuit; the booster circuit is used to convert the voltage provided by the power supply into a high voltage frequency AC voltage; the power supply includes at least any one of the following: commercial AC power supply, DC battery power supply.

In an implementation manner of the present application, the peak value of the high-frequency AC voltage is greater than 5.5kv.

On the other hand, an embodiment of the present application also provides a low-temperature plasma generating method for fresh-keeping fruits and vegetables, applying the above-mentioned low-temperature plasma generating device for fresh-keeping fruits and vegetables, and the method includes: a voltage supply module is welded through electrodes point to supply power to the low temperature plasma generating module; the low temperature plasma generating module generates an electric field based on the diamond mesh electrode and the flat electrode; based on the electric field, the low temperature plasma generating device generates low temperature plasma.

Description of drawings

The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the attached image:

FIG. 1 is a structural diagram of a low-temperature plasma generating device for fresh-keeping fruits and vegetables provided by an embodiment of the present application;

2 is a schematic cross-sectional structure diagram of a low-temperature plasma generation module provided by an embodiment of the present application;

FIG. 3 is a diagram showing the relationship between discharge voltage and discharge power of a low-temperature plasma generating module in which a blocking dielectric plate is made of Al ₂ O ₃ according to an embodiment of the present application;

FIG. 4 is a diagram showing the relationship between discharge voltage and discharge power of a low-temperature plasma generating module in which a barrier dielectric plate is made of AlN, provided by an embodiment of the present application;

5 is a schematic diagram of the front structure of a low-temperature plasma generating module provided by an embodiment of the present application;

6 is a schematic diagram of the reverse side structure of a low-temperature plasma generating module provided by an embodiment of the present application;

FIG. 7 is a schematic diagram of a power supply structure of a voltage supply module provided by an embodiment of the present application;

FIG. 8 is a schematic diagram of a power supply structure of another voltage supply module according to an embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below with reference to the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

For the low-temperature plasma fruit and vegetable preservation technology, the core is the low-temperature plasma generation module. How to generate low-temperature plasma with lower voltage peak and lower power consumption in atmospheric pressure atmosphere has become the key to the research and development of current preservation devices. However, the currently disclosed low-temperature plasma generation module for fresh-keeping fruits and vegetables has disadvantages such as high discharge voltage, insufficient utilization of electrode area, poor contact between electrodes and medium, and easy oxidation and corrosion of electrodes. For example, the plasma sterilization device used in the refrigerator storage room disclosed in Patent No. CN201520300025.3, and the plasma-coupled photocatalytic method and system for removing ethylene in the fresh-keeping storehouse of vegetables and fruits disclosed in Patent No. CN201310179679.0, are based on the principle of corona discharge. It is easy to be transformed into a penetrating spark discharge, which is difficult to control, and will burn fruits and vegetables, and may also cause damage to the equipment itself and the operator. The utilization rate of the electrode area is improved, but the discharge starting voltage is high, and the fresh-keeping device fixes the mesh electrode on the fixing frame by mechanical means. If the electrode is loose, unnecessary discharge may occur between the two gaps. It will also lead to increased local heat generation.

In addition, the currently disclosed low-temperature plasma generation module for fresh-keeping does not take any protective measures for the electrodes, and directly exposes the bare electrodes to the air. As the use time increases, the discharge process will lead to metal ablation on the surface of the electrodes. , oxidation, rust and other unfavorable phenomena, so that the efficient and stable generation of low-temperature plasma cannot be guaranteed.

The embodiments of the present application provide a low-temperature plasma generating device and method for fresh-keeping fruits and vegetables, which are used to solve the problem that the existing devices using low-temperature plasma for sterilizing fruits and vegetables cannot efficiently and stably generate low-temperature plasma.

The technical solutions proposed by the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a structural diagram of a low-temperature plasma generating device for preservation of fruits and vegetables according to an embodiment of the present application. As shown in FIG. 1 , a low-temperature plasma generating device 100 for fresh-keeping fruits and vegetables provided by an embodiment of the present application includes: a voltage supplying module 101 and a low-temperature plasma generating module 102 .

As shown in FIG. 1 , in a low-temperature plasma generating device 100 for fruit and vegetable preservation provided by an embodiment of the present application, a voltage supply module 101 is connected to a low-temperature plasma generating module 102 . When the low-temperature plasma generating device is in use, the direct start-up voltage supply module 101 provides a high-frequency AC voltage for the low-temperature plasma generating module 102, so that the low-temperature plasma generating module 102 discharges, accelerates the collision reaction of free electrons and gas molecules in the air, and generates low temperature plasma. Wherein, the voltage supply module 101 is used to provide a high-frequency AC voltage to the low-temperature plasma generation module 102; the low-temperature plasma generation module 102 is used to discharge under the high-frequency AC voltage, so that the acceleration of free electrons and gas molecules in the air in the air The collision reaction generates low-temperature plasma to kill microorganisms attached to the surface of fruits and vegetables, degrade the ethylene gas synthesized by fruits and vegetables, and inhibit the metabolism of fruits and vegetables.

The low-temperature plasma generating module proposed in the embodiment of the present application will be described in more detail below with reference to FIG. 2 .

FIG. 2 is a schematic cross-sectional structural diagram of a low-temperature plasma generating module according to an embodiment of the present application. In Fig. 2, 201 denotes a diamond mesh electrode, 202 denotes a flat electrode, 203 denotes a blocking dielectric plate, 204 denotes an insulating and anti-corrosion layer, and 205 denotes a heat conducting plate.

As shown in FIG. 2 , in the low-temperature plasma generation module provided by the embodiment of the present application, the first surface of the diamond-shaped mesh electrode is in contact with the first side surface of the blocking dielectric plate, and the first surface of the flat electrode is in contact with the second side surface of the blocking dielectric plate. touch. Wherein, the rhombic mesh electrode of the embodiment of the present application includes several rhombic meshes, and the diagonal size of the several rhombic meshes is 1 mm×2 mm (the length of the first diagonal line is 1 mm, and the length of the second diagonal line is 2 mm), The material of the blocking dielectric plate is aluminum nitride AlN.

It should be noted that, after the voltage is applied to the low-temperature plasma generating module, the discharge occurs at the edge of the electrode, and the mesh electrode can greatly increase the circumference of the electrode and make full use of the limited area. Therefore, choosing a mesh electrode can be more efficient. to generate low temperature plasma. When the grid area is constant, the perimeter of the rhombus grid is the largest, so the selection of rhombic mesh electrodes can maximize the discharge area. In order to reduce the discharge initiation voltage of the low temperature plasma generation module, increase the discharge intensity of the low temperature plasma generation module, and improve the low temperature plasma generation rate, it is necessary to optimize the size of the diamond mesh and the material and thickness of the blocking dielectric plate. Among them, the blocking dielectric plate needs to have the characteristics of high melting point, large dielectric constant, high breakdown voltage, good mechanical properties, good thermal conductivity, and stable chemical properties. The size of the rhombus grid should conform to the discharge law, and should not be too large or too small. This is because when the size of the rhombus is too large, the gap between the filaments in the rhombus grid is too large, resulting in insufficient surface utilization, and the discharge area is blocked. The proportion of the surface of the dielectric plate is not high; when the size of the rhombus is too small, the grids are too dense. Since the grids of the rhombus-shaped mesh electrodes are equipotential, they will affect each other and weaken the electric field strength between them, so that the gas can not be reached. Field strength required for gap discharge. In addition, when the size of the rhombus is too small, due to the interaction between the space charge and the surface charge generated by the partial area discharge, the discharge in the surrounding area will be suppressed, which is not conducive to the generation of low-temperature plasma.

Further, the relative permittivity ε _rd of the Al ₂ O ₃ material and the AlN material barrier dielectric plate are both larger, and ε _rd is 9.8 and 8.6, respectively. According to the principle of electric flux conservation, the electric field strength is related to the relative dielectric The constant is inversely proportional, that is, due to the existence of the blocking dielectric plate, the electric field strength in the air gap is ε _rd times the electric field strength in the blocking dielectric plate. The larger the value, the higher the low temperature plasma generation efficiency. In addition, the two blocking medium plates containing Al material have high thermal conductivity and thermal stability, and have good chemical stability and mechanical properties, and are suitable as the blocking medium of the device. For the barrier dielectric plate made of Al ₂ O ₃ and the barrier dielectric plate made of AlN, the discharge characteristics of diamond grids of different sizes are shown in Figure 3 and Figure 4.

FIG. 3 is a diagram showing the relationship between discharge voltage and discharge power of a low-temperature plasma generating module with a barrier dielectric plate made of Al ₂ O ₃ provided by an embodiment of the present application; FIG. 4 is a barrier dielectric plate provided by an embodiment of the present application. The relationship between the discharge voltage and the discharge power of the low-temperature plasma generation module made of AlN. Among them, the grid line width of the diamond grid of the low temperature plasma generation module studied (the width of the sides of the diamond grid) is uniformly 0.3mm, and the diagonal dimensions of the diamond grid are as follows: ①: 1mm×2mm , ②: 2mm×4mm, ③: 3mm×5mm, ④: 4mm×8mm, the thickness of the blocking medium plate is 1mm.

As shown in Figure 3 and Figure 4, the discharge power under the two barrier dielectric materials, Al ₂ O ₃ and AlN, increases continuously with the increase of the applied voltage, because when the voltage increases, it acts on the edge of the electrode. The voltage on the surrounding air gap also increases, and the electric field strength increases, so that the discharge increases and the power increases. However, due to the high thermal conductivity of AlN ceramics (about 320W/m·K), it is 5-8 times that of Al ₂ O ₃ ; the thermal expansion coefficient is 4.5×10 ^-6 /K, which is only 0.56 times that of Al ₂ O ₃ . ; The dielectric loss is 0.001, which is only 0.5 times that of Al ₂ O ₃ ; the thermal shock resistance is good; the flexural strength is higher than that of Al ₂ O ₃ ; and the discharge power under the same voltage is similar. Therefore, when AlN is selected as the material of the barrier dielectric plate, it can not only have a considerable low plasma generation efficiency, but also increase the mechanical strength of the structure, reduce the heat generation of discharge, and have better heat dissipation performance and small thermal expansion. Therefore, AlN is selected. As the material of the blocking medium plate.

As shown in Fig. 4, the discharge power is the largest when the diagonal product is 1 mm × 2 mm. Therefore, the grid line width is 0.3 mm and the diagonal line is 1 mm × 2 mm as the diamond grid size. In addition, with regard to the thickness of the blocking dielectric plate, the present application has conducted experiments on four types of blocking dielectric plate structures with thicknesses of 0.365mm, 0.5mm, 0.635mm and 1mm, and found that both 0.365mm and 0.5mm can achieve a larger discharge under the same voltage. Power, considering that the blocking dielectric plate needs to have a certain mechanical strength, so choose a thickness of 0.5mm.

Further, the materials of the rhombic mesh electrode and the flat electrode are AgCu28.

It should be noted that, for the electrodes in the low temperature plasma generating module, the material should firstly be a good conductor of electricity and heat, and secondly, it should have certain ductility and workability. At present, the commonly used electrode material is copper; in addition, because silver has the highest electrical and thermal conductivity, it is also used in precision instruments. However, the chemical properties of copper are relatively active. When the temperature is high, it can be oxidized by oxygen in the air to form non-conductive black copper oxide; it can also react with water and carbon dioxide in humid air to form patina with high resistivity. If the low-temperature plasma generation module uses copper as the electrode material, and the above-mentioned corrosion reaction occurs, when the low-temperature plasma generation module discharges to generate low-temperature plasma, many sharp black copper oxide and verdigris layers will be formed on the copper surface due to the generated black copper oxide layer. The unevenness of the electrode surface will seriously distort the electric field near the electrode in the protruding part, thereby reducing the uniformity of the discharge and heat generation of the low-temperature plasma generation module, which will seriously reduce the The generation efficiency of low temperature plasma and the service life of the low temperature plasma generation module. Therefore, copper should not be used directly as an electrode material.

Although the physical and chemical properties of silver are better than those of copper, because silver is a precious metal, the cost of using silver as an electrode material is relatively high, and silver is soft and has insufficient strength as an electrode material. Therefore, silver should not be used directly as an electrode material.

In order to solve the above-mentioned problems exposed by common electrode materials when generating low-temperature plasma, AgCu28 electrical contact material is selected to make electrodes in the embodiments of the present application. The addition of Ag to Cu can significantly increase the corrosion resistance, chemical stability and mechanical strength of the material, so that the material has the advantages of both metals, and has good electrical and thermal conductivity, burning resistance, wear resistance, and anti-corrosion properties. Fusion welding characteristics, chemical stability characteristics, and high mechanical strength characteristics are more suitable for the needs of this application. Additionally, since the electrical contact material has a lower melting point than either silver or copper, it is also easier to handle. The melting point of AgCu28 is only 1016K, which is lower than that of pure copper, and its wettability is good. In addition, AgCu28 also has excellent physical and chemical properties: its resistivity is 1.93×10 ^-8 Ω·m, and its electrical conductivity can reach 90.7% of that of pure copper; its tensile strength is 587MPa, which is about 2.5 times that of ordinary pure copper. ; The hardness can reach 850N/mm ² ; The thermal conductivity is 408W·m ^-1 K ^-1 . In the embodiment of this application, AgCu28 is selected as the fabrication material of the rhombus mesh electrode and the plate electrode of the low-temperature plasma generating module, which greatly improves the efficiency and stability of generating the low-temperature plasma.

Further, the shape of the rhombic mesh electrode is the same as the shape of the flat electrode; the area of the first surface of the rhombus mesh electrode is equal to the area of the first surface of the flat electrode; the first surface of the rhombus mesh electrode is on the first side of the blocking medium plate. The contact position corresponding to the upper surface of the plate electrode corresponds to the contact position of the first surface of the flat electrode on the second side surface of the blocking medium plate, which is symmetrical with respect to the blocking medium plate.

It should be noted that the above-mentioned contact method can make the discharge of the low-temperature plasma generation module occur earlier, the current pulse is more dense, the discharge power is larger, the transferred charge is more, the plasma energy is higher, and the activity is stronger. . Therefore, the shape of the rhombic mesh electrode is made the same as the shape of the plate electrode; the area of the first surface of the diamond mesh electrode is equal to the area of the first surface of the plate electrode; the first surface of the diamond mesh electrode is on the first side of the blocking medium plate The contact position corresponding to the first surface of the flat electrode on the second side of the blocking dielectric plate is symmetrical with respect to the blocking dielectric plate, so that the low-temperature plasma generating module can efficiently and stably generate low-temperature plasma.

Further, the contact mode between the first surface of the diamond-shaped mesh electrode and the first side of the blocking medium plate is PCB printing, and the contact mode between the first surface of the flat electrode and the second side of the blocking medium plate is PCB printing; Electrode welding points are provided, and electrode welding points are arranged on the flat electrode; wherein, the electrode welding points are used to connect the low-temperature plasma generating module with the voltage supplying module to supply power to the low-temperature plasma generating module.

It should be noted that, for the traditional low-temperature plasma generation module based on surface dielectric barrier discharge, there is a major drawback, that is, the problem that the mesh electrode is not in close contact with the blocking dielectric plate, especially the AlN blocking dielectric used in the embodiments of the present application. The hardness of the plate is relatively large, almost no deformation occurs under the action of external pressure, and it is difficult to contact closely. The traditional contact method is a mechanical contact method, that is, the electrodes are fastened on the blocking medium plate by screws and nuts. Obviously, the traditional contact method cannot make the mesh electrode and the blocking dielectric plate completely and uniformly contact the two. When applying voltage to the low-temperature plasma generation module, there will always be some areas with better contact that discharge first, while areas with insufficient contact are weakly discharged, resulting in a voltage of about several kV for initial discharge and completely uniform discharge. gap. After the entire area is completely discharged, the part with better contact is violently discharged, while the part with poor contact is weaker than the part with good contact, resulting in great inhomogeneity, which can easily lead to local overheating of the barrier dielectric plate, resulting in The barrier dielectric plate is prone to rupture after a period of use. The rupture often extends from the position in contact with the screw to the severe discharge area, and cracks appear, resulting in the breakdown of the barrier dielectric plate.

In order to solve the problem that the diamond-shaped mesh electrode is not in close contact with the blocking medium plate caused by the traditional contact method, the embodiment of the present application adopts the PCB printing method to separate the first surface of the diamond-shaped mesh electrode and the first surface of the flat electrode. It is attached to the two sides of the blocking dielectric plate, so that the diamond mesh electrode, the flat electrode and the blocking dielectric plate are integrated, which greatly reduces the unevenness of contact and effectively solves the problem of uneven contact caused by the blocking dielectric plate. , resulting in the problem of local overheating and rupture, which affects the operation of the plasma generating device, and improves the stability of the low-temperature plasma generating module for generating low-temperature plasma. In addition, in order to facilitate the low-temperature plasma generation module to be connected to the voltage supply module, when the first surface of the rhombus mesh electrode and the first surface of the flat electrode are attached to the side of the blocking medium plate, the rhombus mesh electrode and the flat electrode are Set electrode welding points on it.

It should also be noted that since AgCu28 also has good weldability, when welding external leads, it can ensure that the solder joints are firm and stable, and effectively avoid the problem of partial discharge caused by loose solder joints or loose contact.

As shown in FIG. 2 , in the low-temperature plasma generating module provided by the embodiment of the present application, an insulating anti-corrosion layer is covered on the second surface of the diamond-shaped mesh electrode, and an insulating anti-corrosion layer is also covered on the second surface of the flat electrode Anti-corrosion layer. Among them, the insulating and anti-corrosion layer adopts water-based epoxy resin.

It should be noted that the low-temperature plasma generation module may ablate the electrode surface during the discharge process, resulting in electrode defect, resulting in reduced surface flatness, thereby increasing the non-uniformity of the discharge, thereby aggravating the discharge ablation, leading to a vicious circle. Therefore, in order to protect the electrode, the discharge structure can discharge as uniformly as possible, enhance its stability and corrosion resistance, and prolong its service life. In the embodiment of the present application, an insulating anti-corrosion layer is covered on the second surface of the diamond-shaped mesh electrode, and an insulating anti-corrosion layer is covered on the second surface of the flat electrode. Water-based epoxy resin has the characteristics of good adhesion, low shrinkage, good dimensional stability, high hardness, high temperature resistance, corrosion resistance, wear resistance, excellent mechanical properties and insulation properties, and the water-based coating combines epoxy resin with particles. It can be dispersed in water in the form of water, avoiding the use of volatile organic compounds that are harmful to the human body, and is safe, green and environmentally friendly. In addition, the relative dielectric constant of the water-based epoxy resin is 3-4, which is higher than that of air, and the dielectric loss angle of the water-based epoxy resin is low (tanδ=4×10-3), which will not affect the generation efficiency of low-temperature plasma. Therefore, water-based epoxy resin is selected as the insulating and anti-corrosion layer of the low-temperature plasma generating module. Wherein, the thickness of the insulating anti-corrosion layer may be 100 μm. It should be noted that the thickness of the insulating anti-corrosion layer can be adjusted according to the actual situation, which is not limited in this embodiment of the present application.

As shown in FIG. 2 , in the low-temperature plasma generating module provided by the embodiment of the present application, a heat-conducting plate is also covered on the second surface of the flat electrode. It can be understood that the thermally conductive plate is covered on the insulating anti-corrosion layer covered on the second surface of the plate electrode.

It should be noted that the purpose of covering the second surface of the flat electrode with a heat-conducting plate is to further enhance the heat dissipation capability of the low-temperature plasma generating module and improve the stability and lifespan of the low-temperature plasma generating module. The heat-conducting plate is made of pure copper which is economical and has good thermal conductivity. The size is the same as that of the blocking dielectric plate, which ensures that the heat generated during the discharge of the low-temperature plasma generating module can be conducted to the metal plate more quickly for heat dissipation. In addition, in order to ensure more sufficient and efficient heat exchange between the thermal conductive plate and the blocking medium plate, thermal conductive silica gel is used for bonding. Thermally conductive silica gel has excellent anti-cold and heat alternating performance, anti-aging performance and electrical insulation performance, and has excellent moisture resistance, shock resistance, corona resistance, anti-leakage performance and chemical resistance.

In order to further illustrate the structure of the low-temperature plasma generating module, a low-temperature plasma generating module proposed in the embodiments of the present application will be described in detail below with reference to FIGS. 5 and 6 .

FIG. 5 is a schematic diagram of a front side structure of a low temperature plasma generation module provided by an embodiment of the present application, and FIG. 6 is a schematic diagram of a back side structure of a low temperature plasma generation module provided by an embodiment of the present application. As shown in Fig. 5 and Fig. 6, 1 denotes a blocking dielectric plate, 2 denotes a through hole, 3 denotes a diamond mesh electrode covered with an insulating and anti-corrosion layer, 4 denotes a solder joint, 5 denotes a flat electrode, and 6 denotes a thermally conductive plate.

As shown in FIG. 5 and FIG. 6 , the blocking medium plate in the low-temperature plasma generating module provided by the embodiment of the present application not only serves as the substrate of the entire low-temperature plasma generating module, but also serves as the blocking medium of the low-temperature plasma generating module. The function of the through holes is to cooperate with screws, nuts and washers to fix the low temperature plasma generating module; it is understandable that the through holes penetrate through the blocking medium plate and the heat conducting plate. The first surface of the rhombic mesh electrode is in contact with the first side surface of the blocking dielectric plate through PCB printing, the area of the rhombic mesh electrode is smaller than that of the blocking dielectric plate, and the rhombic mesh electrode is covered with an insulating anti-corrosion layer. The welding points are respectively located on the edge of the diamond mesh electrode and the edge of the plate electrode, and the welding points on the diamond mesh electrode and the welding point on the plate electrode are located symmetrically with respect to the blocking medium plate. The first surface of the flat electrode is in contact with the second side surface of the blocking dielectric board through PCB printing, which is covered with an insulating anti-corrosion layer; since the surface of the flat electrode is covered by a thermal conductive plate, it is not actually visible, so as shown in Figure 6, the flat The electrode bonding position is indicated by a dotted line; it should be noted that the area of the flat electrode and the rhombic mesh electrode is the same, and the corresponding contact position between the first surface of the rhombus mesh electrode and the first side of the blocking medium plate, and the flat electrode The corresponding contact positions between the first surface of the plate electrode and the second side of the blocking medium plate are the same: for example, when the shape and first surface area of the plate electrode and the rhombus mesh electrode are the same, the center point of the plate electrode and the second side of the blocking medium plate are the same. The center point of one side is coincident, and the center point of the rhombic mesh electrode is coincident with the center point of the second side of the impedance dielectric plate. Since the center point of the first side and the center point of the second side are symmetrical with respect to the blocking dielectric plate, so the plate The contact positions of the electrodes on the blocking medium plate are the same as the contact positions of the diamond mesh electrodes on the blocking medium plate. The size of the heat-conducting plate is the same as that of the blocking dielectric plate, and the heat generated during the discharge of the low-temperature plasma generating module can be conducted to the metal plate for heat dissipation more quickly, thereby increasing the discharge stability and service life of the low-temperature plasma generating module.

FIG. 7 is a schematic diagram of a power supply structure of a voltage supply module according to an embodiment of the present application. As shown in FIG. 7 , a voltage supply module power supply structure provided by an embodiment of the present application includes: a power supply and a boost circuit. Among them, the power supply can be a 220V commercial power supply; the booster circuit includes: external wiring, an AC-DC rectifier module, and a DC-AC inverter module.

Among them, the 220V commercial power supply is used to provide the commercial 220V AC voltage, and the output end of the 220V commercial power supply is connected to the input end of one end of the AC-DC rectifier module through external wiring; the AC-DC rectifier module is used to provide the 220V commercial power supply. The commercial 220V AC voltage is rectified into DC voltage, and the output end of the other end of the AC-DC rectifier module is connected to the input end of one end of the DC-AC inverter module through external wiring; the DC-AC inverter module is used to output the AC-DC rectifier module. The DC voltage of the inverter is converted into a high-frequency AC voltage, and then the output terminal of the other end of the DC-AC inverter module is connected to the low-temperature plasma generation module through external wiring, which is used to apply the high-frequency AC voltage to the low-temperature plasma generation module, so that the low-temperature plasma The volume generation module discharges to generate low temperature plasma.

It should be noted that, when the low-temperature plasma generating module shown in FIG. 2 is used in the embodiment of the present application, when the applied voltage increases to 5.5kv, the low-temperature plasma generating module is completely discharged, so the high-frequency AC voltage provided by the voltage supply module is The peak value is greater than 5.5kv.

FIG. 8 is a schematic diagram of a power supply structure of another voltage supply module according to an embodiment of the present application. As shown in FIG. 8 , a voltage supply module power supply structure provided by an embodiment of the present application includes: a power supply and a booster circuit. Wherein, the power supply can be a DC battery power supply; the booster circuit includes: external wiring and a DC-AC inverter module.

The DC battery power supply is used to provide DC voltage, and the DC voltage of the DC battery power supply can be selected according to actual needs, which is not limited in the embodiment of the present application; the output end of the DC battery power supply is directly connected to the DC-AC through external wiring. One end of the inverter module is input and output; the DC-AC inverter module converts the DC voltage provided by the DC battery power supply into a high-frequency AC voltage, and then the output end of the other end of the DC-AC inverter module is connected to the low-temperature plasma generation module through external wiring. , which is used to apply a high-frequency AC voltage to the low-temperature plasma generating module to discharge the low-temperature plasma generating module to generate low-temperature plasma.

It should be noted that, when using the low-temperature plasma generating device provided in the embodiment of the present application, one of the two voltage supply structures shown in FIG. 7 and FIG. 8 can be used to provide module power supply according to the characteristics of the environment. When the plasma generating module is connected with the power supply structure of the voltage supplying module, the two wires of the output end of the power supplying structure of the voltage supplying module are respectively welded to the welding points on the side of the diamond-shaped mesh electrode in the low-temperature plasma generating module, and the welding point on the side of the flat electrode in the low-temperature plasma generating module. on the welding point to ensure the firmness and stability of the connection.

The above is an example of the device in the embodiment of the application. Based on the same inventive concept, the embodiment of the application also provides a low-temperature plasma generation method for fresh-keeping fruits and vegetables, using the above-mentioned low-temperature plasma for fresh-keeping fruits and vegetables. body generator. The method includes the following process:

First, the voltage supply module supplies power to the low-temperature plasma generation module through the electrode welding point; then the low-temperature plasma generation module generates an electric field based on the powered diamond mesh electrode and the powered flat electrode; finally, the low-temperature plasma generating device generates low-temperature plasma based on the generated electric field. plasma.

Specifically, due to natural factors such as cosmic radiation and radioactive material radiation, there are certain density of charged particles in the air. When the voltage supply provided by the voltage supply module is applied to the diamond-shaped mesh electrodes and the plate electrodes on both sides of the blocking dielectric plate, an electric field will be generated in the space around the low-temperature plasma generating module, and the edge of the mesh line in the diamond-shaped mesh electrode will be generated. The electric field with the dielectric plate is the strongest. Electrons in the electric field are accelerated, producing more electrons through inelastic collisions with neutral gas molecules. A large number of electrons come together and form an electron avalanche. When the strength of the generated electric field is greater than the breakdown field strength of the air, a streamer discharge process will occur at the edges of the grid lines in the rhombic mesh electrode. The ionization process is strengthened, and the photoionization process occurs, so that the discharge enters the streamer discharge stage. The newly generated electrons in the photoionization process will cause secondary collision ionization between the electrons and neutral gas molecules, resulting in secondary electron avalanches, which eventually lead to the breakdown of the air and the production of low-temperature plasma. The specific performance is that many small-diameter micro-discharge channels are formed in the space between the edge of the grid line in the diamond-shaped mesh electrode and the blocking dielectric plate, and the low-temperature plasma is generated by the gas in the micro-discharge channel through the process of impact ionization and photoionization.

Further, since the low-temperature plasma generating module is driven by a high-frequency alternating voltage, the voltage polarity changes periodically. When the voltage of the rhombic mesh electrode is lower than that of the flat electrode, the negative ions and electrons generated by the streamer discharge process move to the blocking dielectric plate and accumulate on the surface of the blocking dielectric plate, forming an additional electric field opposite to the AC electric field provided by the voltage supply module , when the accumulated charge is enough, the total electric field strength will be less than the air breakdown voltage, and the discharge process will be interrupted. When the polarity of the AC voltage provided by the voltage supply module changes, the AC electric field generated by it and the additional electric field generated by the charges accumulated on the blocking dielectric plate become in the same direction. At this time, the electric field is strengthened, and the total electric field strength will be higher than that of the air shock. When the field strength is penetrated, the streamer discharge process will occur again, forming a micro-discharge channel and generating a low-temperature plasma. Since the polarity of the AC voltage provided by the voltage supply module is periodically changed, the streamer discharge process is also periodically initiated and interrupted, so as to periodically continue to generate low-temperature plasma.

A low-temperature plasma generating device and method for preservation of fruits and vegetables provided by the embodiments of the present application have the following advantages:

(1) The diagonal size of several rhombus meshes included in the rhombus mesh electrode in a low-temperature plasma generating device for fruit and vegetable preservation provided by the embodiment of the present application is 1mm×2mm, and the material of the blocking medium plate is aluminum nitride AlN. By selecting AlN as the material of the barrier dielectric plate and 1mm×2mm as the grid diagonal size of the diamond-shaped mesh electrode, the mechanical strength of the low-temperature plasma generation module is ensured, the heat generation of the discharge of the low-temperature plasma generation module is reduced, and the The heat dissipation performance reduces the degree of thermal expansion, and also maximizes the efficiency and stability of the low-temperature plasma generator to generate low-temperature plasma, so that the low-temperature plasma generator can better kill the microorganisms attached to the surface of fruits and vegetables and degrade fruits and vegetables. Synthetic ethylene gas inhibits the metabolism of fruits and vegetables, so that fruits and vegetables get better fresh-keeping effect.

(2) In a low-temperature plasma generating device for preservation of fruits and vegetables provided by the embodiments of the present application, AgCu28 electrical contact material is used as the electrode material of the rhombus mesh electrode and the flat electrode, and AgCu28 is used for corrosion resistance, wear resistance, chemical resistance The advantages of stability, good electrical conductivity, high mechanical strength, and strong workability and weldability improve the efficiency and stability of the low-temperature plasma generating device for generating low-temperature plasma. In addition, AgCu28 is used as a welding material to ensure the reliability of external wiring, effectively avoiding the possibility of loose contact and partial discharge caused by vibration and long-term work.

(3) In a low-temperature plasma generating device for fresh-keeping fruits and vegetables provided by the embodiment of the present application, the manufacturing process of PCB printing is used for the contact mode of the diamond-shaped mesh electrode and the blocking medium plate and the contact mode of the flat electrode and the blocking medium plate Optimized, the diamond mesh electrode and the flat electrode are directly bonded to the surface of the blocking dielectric plate at high temperature, which greatly reduces the degree of uneven bonding and effectively solves the problem of local overheating and uneven stress on the blocking dielectric plate. The problem of cracking increases the efficiency and stability of the low-temperature plasma generating device for generating low-temperature plasma.

(4) In a low-temperature plasma generating device for preservation of fruits and vegetables provided by the embodiment of the present application, water-based epoxy resin material is used as an insulating anti-corrosion layer to cover the diamond-shaped mesh electrode and the flat electrode, which effectively avoids the discharge of the exposed electrode. The occurrence of ablation and oxidation during the process enhances the corrosion resistance, wear resistance and stability of the low-temperature plasma generation module, and prolongs the service life of the low-temperature plasma generator, thereby improving the low-temperature plasma generator generated by the low-temperature plasma generator. body efficiency and stability. In addition, the insulating anti-corrosion layer has strong insulating properties, which can further reduce the use risk and ensure the personal safety of users.

(5) In the low-temperature plasma generating device for fresh-keeping fruits and vegetables provided by the embodiment of the present application, pure copper material is used as the heat-conducting plate, which can further enhance the heat dissipation capability of the low-temperature plasma generating device, increase the uniformity of discharge, and prolong the low temperature The service life of the plasma generator.

Each embodiment in this application is described in a progressive manner, and the same and similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and reference may be made to some descriptions of the method embodiments for related parts.

It should also be noted that the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device comprising a series of elements includes not only those elements, but also Other elements not expressly listed, or which are inherent to such a process, method, article of manufacture, or apparatus are also included. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article of manufacture, or device that includes the element.

The above descriptions are merely examples of the present application, and are not intended to limit the present application. Various modifications and variations of this application are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of the claims of this application.

Claims (7)

1. A low-temperature plasma generating device for fruit and vegetable fresh-keeping is characterized by comprising: a low-temperature plasma generation module;

the low-temperature plasma generating module comprises a blocking dielectric plate, a rhombic mesh electrode and a flat electrode; the first surface of the rhombic net electrode is in contact with the first side surface of the blocking dielectric plate, and the first surface of the flat plate electrode is in contact with the second side surface of the blocking dielectric plate;

the rhombic mesh electrode comprises a plurality of rhombic meshes, wherein the first diagonal length of the rhombic meshes is 1mm, the second diagonal length of the rhombic meshes is 2mm, and the mesh line width of the rhombic mesh electrode is 0.3 mm; the thickness of the blocking dielectric plate is 0.5 mm;

the blocking dielectric plate is made of aluminum nitride (AlN); the material of the rhombic mesh electrode is AgCu 28; the flat plate electrode is made of AgCu 28;

an insulating anti-corrosion layer covers the second surface of the rhombic net electrode; and the second surface of the flat plate electrode is covered with an insulating anti-corrosion layer.

2. The low-temperature plasma generating device for fruit and vegetable fresh-keeping according to claim 1, wherein the diamond-shaped mesh electrode has the same shape as the flat plate electrode;

the area of the first surface of the rhombic net electrode is equal to that of the first surface of the flat plate electrode;

the contact positions of the first surface of the rhombic net-shaped electrode on the first side surface of the blocking dielectric plate and the contact positions of the first surface of the plate electrode on the second side surface of the blocking dielectric plate are symmetrical relative to the blocking dielectric plate.

3. The low-temperature plasma generating device for fruit and vegetable fresh-keeping according to claim 2, wherein the first surface of the rhombic mesh electrode is in contact with the first side surface of the blocking dielectric plate in a PCB printing mode; and the number of the first and second groups,

the contact mode of the first surface of the flat plate electrode and the second side surface of the blocking dielectric plate is PCB printing;

electrode welding points are arranged on the rhombic mesh electrodes, and electrode welding points are arranged on the flat plate electrodes; wherein the electrode welding point is used for connecting the low-temperature plasma generating module with the voltage providing module.

4. The low-temperature plasma generating device for fruit and vegetable fresh-keeping according to claim 1, wherein the second surface of the flat electrode is covered with a heat conducting plate.

5. The low-temperature plasma generating device for fruit and vegetable fresh-keeping according to claim 1, characterized by further comprising a voltage providing module; the voltage supply module comprises a power supply and a booster circuit;

the power supply is connected with the booster circuit; the booster circuit is used for converting the voltage provided by the power supply into high-frequency alternating-current voltage;

the power supply comprises at least one of the following items: commercial AC power supply and DC battery power supply.

6. The low-temperature plasma generating device for fruit and vegetable fresh-keeping according to claim 5, wherein the peak value of the high-frequency alternating voltage is more than 5.5 kv.

7. A low-temperature plasma generating method for fruit and vegetable fresh keeping, which is characterized in that the low-temperature plasma generating device for fruit and vegetable fresh keeping of any one of claims 1-6 is applied, and the method comprises the following steps:

the voltage supply module supplies power to the low-temperature plasma generation module through the electrode welding point;

the low-temperature plasma generation module generates an electric field based on the rhombic mesh electrode and the flat plate electrode;

based on the electric field, the low-temperature plasma generating device generates low-temperature plasma.

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