Parameter design method of multi-section distributed electrode based on inner wall disinfection of plasma tube

Abstract

The application discloses a parameter design method of a multi-section distributed electrode based on inner wall disinfection of a plasma tube, which comprises the following steps: a three-dimensional simulation model of a multi-section distributed-ring annular sleeve electrode structure is established; X-axis electric field check maps and Y-axis electric field check maps of a discharge area between two adjacent electrodes in the multi-section distributed-ring annular sleeve electrode structure model are determined; based on the multi-section distributed-ring annular sleeve electrode structure model, no target tube is inserted, working gas is introduced, the spacing between two electrodes of a single-section annular jet sleeve is changed under an applied electric field intensity, and an effective discharge area surrounded by preset electric field intensity isosurface is obtained; the target tube with different sizes is inserted into the effective discharge area, the pulse voltage of the external electric field is increased to a preset pulse voltage, the effective discharge area surrounded by the preset electric field isosurface is simulated to obtain an effective discharge area, and the maximum effective discharge area is determined. The application realizes the design of the multi-section distributed electrode.

Description

Technical Field

[0001] This invention relates to the field of plasma technology, specifically to a parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection. Background Technology

[0002] In scientific research and production practice, there are many situations where the inner surface of tubular workpieces is used as the working surface. For example, in industry, the deposition of a thin film on the inner surface of pipes can significantly improve the performance of the workpiece; in the food industry, it can be used for industrial sterilization of the inner surface of conveying pipes; and in the medical and health field, it can be used to disinfect medical rubber tubing that is not resistant to moisture and heat to improve the safety of use.

[0003] However, preparing and sterilizing thin films on the inner walls of long tubes with small inner diameters is quite difficult. Plasma surface modification and sterilization of the inner surface of slender tubes has always been a major challenge in surface treatment. Due to the excessively small inner diameter and high length-to-diameter ratio, it is difficult to uniformly deliver plasma into the tube, making the process challenging. When the inner diameter of the pipe is on the order of millimeters, or even less than 1 mm, the electron free path of low-pressure plasma is greater than 1 cm, making it very difficult to generate high-density plasma inside the pipe, resulting in insufficient treatment effects. Existing technology publication number CN113692100A discloses a multi-segment electrode plasma jet triggering method for disinfecting the inner wall of an endoscope. The structure of the multi-segment electrode is a multi-segment distributed ring-ring sleeve electrode structure that generates plasma in the inner cavity of the pipe, producing uniform plasma discharge on the inner surface of the pipe. However, in practical applications, it has been found that using a multi-segment distributed ring-ring sleeve electrode structure to generate plasma within the pipe cavity has significant impacts on the uniformity of plasma discharge when treating the inner surfaces of insulated pipes of different lengths and diameters. Factors such as the working gas, the diameter and length of the pipe being treated, and the electrode spacing parameters all have a considerable influence. Existing technology publication CN103585650B discloses a low-temperature plasma endoscope sterilization device. Its multi-segment electrode structure plasma jet endoscope sterilization method has the same electrode structure as the multi-segment distributed ring-ring sleeve electrode. However, in practical applications, when treating the inner surfaces of pipes of different lengths and diameters, the electrode design parameters, voltage amplitude, repetition frequency, etc., change with the pipe diameter, failing to maintain a stable range. This places high demands on the output voltage amplitude and frequency of the high-voltage power supply, posing numerous difficulties for practical engineering applications. Furthermore, since the electrodes are in direct contact with the outer wall of the endoscope, there is a risk of surface flashover, potentially damaging the outer surface material of the endoscope. Meanwhile, since the target tube of the endoscope is relatively long, if a high-voltage electrode of the same length as the target tube is used, the power requirements would be too high, which is not feasible. Therefore, the target tube is usually processed by moving it between the electrodes. The length of the electrode processed in one processing cycle needs to be determined at one time.

[0004] To effectively address technical challenges in electrode design, mitigate the impact of working gases on plasma discharge, and optimize electrode design parameters for multi-segment distributed-ring sleeve electrodes when processing pipes of varying lengths and inner diameters, thus achieving optimal discharge performance, this study utilizes electric field simulation to model and analyze electrode parameters based on the multi-segment distributed-ring sleeve electrode structure. This simulation yields electric field and electrode data for different working gases and for processing the inner surfaces of insulated pipes of varying lengths and diameters, providing guidance for practical electrode design. Summary of the Invention

[0005] 1. The technical problem to be solved: To address the aforementioned technical problems, this invention provides a parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection. The method achieves the design of the actual electrode through electrode modeling and electric field simulation analysis, thereby bringing convenience to engineering applications.

[0006] 2. Technical Solution: A parameter design method for a multi-segment distributed electrode based on plasma tube inner wall sterilization, characterized by the following steps: Step 1: Establish a 3D simulation model of the multi-segment distributed-ring-tube electrode structure and determine its relevant parameters; the multi-segment distributed-ring-tube electrode structure includes multiple single-segment annular jet tubes; the multi-segment distributed-ring-tube electrode includes a glass tube and multiple electrode rings sleeved on the outer surface of the glass tube; the multiple electrode rings are distributed with high-voltage electrode rings and low-voltage electrode rings interleaved; an adjacent high-voltage electrode ring and a low-voltage electrode ring form a single-segment annular jet tube; relevant parameters include working gas, electrode width, outer diameter of the quartz glass tube, and inner diameter of the quartz glass tube; determine the X-axis electric field verification diagram and Y-axis electric field verification diagram of the discharge region between two adjacent electrodes in the multi-segment distributed-ring-tube electrode structure model; Step 2: Determine the distance between adjacent electrodes of a single-segment annular jet sleeve: Based on the multi-segment distributed-annular sleeve electrode structure model, when there is no target tube in the discharge region, simulate the introduction of the corresponding working gas, and change the distance between the two electrodes of the single-segment annular jet sleeve with a preset external electric field strength to simulate the electric field strength between the electrodes at different electrode distances; and obtain the discharge region enclosed by the preset electric field strength, i.e., the critical breakdown voltage contour lines; if the preset electric field contour lines can form a closed region, then the closed region is the effective discharge region; at the same time, the corresponding electrode distance is the critical maximum electrode distance for achieving working gas breakdown discharge; Step 3: Determine the length of the effective discharge region of the dielectric tube in the electric field; based on the effective discharge region obtained in Step 2, place target tubes of different preset diameters into the effective discharge region, increase the pulse voltage of the external electric field to the preset pulse voltage, and simulate to obtain the effective discharge region enclosed by the electric field contour lines of the preset size; thus, determine the length of the maximum effective discharge region that a single-segment annular jet sleeve can generate in the target tube to be disinfected under the preset electric field strength, electrode spacing, and target tube diameter parameters.

[0007] Furthermore, in step 2, under the applied electric field strength, as the distance between the electrodes increases, the corresponding effective discharge area first increases and then decreases until it becomes 0; when the area of ​​the effective discharge area becomes 0, the electric field strength in the central region between the electrodes is insufficient to break down the working gas discharge.

[0008] Furthermore, in step 2, when the working gas is He gas, the applied electric field strength is 4.5kV, and the simulation yields the preset electric field strength, i.e., the breakdown field strength. E breakdown_He It is 2.7 kV / cm.

[0009] Furthermore, in step 3, when the working gas is He gas, the intensity of the external electric field is increased to 8kV; the electric field strength of the preset value, i.e., the breakdown field strength, is obtained through simulation. E breakdown_He It is 2.7 kV / cm.

[0010] Furthermore, the working gas includes He and Ar gases.

[0011] Furthermore, it also includes step 4: based on the length corresponding to the maximum effective discharge area of ​​the single-segment annular jet sleeve obtained in step 3, the maximum length that the multi-segment distributed-ring sleeve electrode can process at one time is obtained.

[0012] 3. Beneficial effects: (1) This invention proposes an electrode parameter design model and method for multi-segment distributed ring-ring electrodes for endoscope inner wall disinfection. By establishing an electrostatic field coupling superposition model and combining it with electric field simulation, the electrode parameter design is reliably verified in theory. This electrode modeling and electric field simulation combined analysis and electrode parameter design method have reference value for other plasma electrodes and engineering design.

[0013] (2) Based on the electrostatic field strength distribution characteristics and laws at different positions of the single-segment annular sleeve jet electrode, this invention innovatively proposes an effective discharge zone length x. dis The parameters are used to evaluate the critical field strength design value inside the electrode sleeve, providing a theoretical design standard for plasma electrode parameter design.

[0014] (3) The present invention innovatively establishes a modeling method for electric field coupling superposition circuit model of multi-segment electrode structure, and provides a reliable circuit model design method for similar electric field distribution relationships with mutual coupling and overlap formed by multiple pairs of distributed electrodes. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the multi-segment distributed ring-ring electrode involved in this application; Figure 2 This is a schematic diagram of the six-segment distributed outer shell electrode processing function in a specific embodiment; Figure 3 A typical location field strength coordinate calibration diagram for a single-segment annular jet sleeve without a target tube; Figure 4 Simulated curves for different spacing dimensions of a single-segment annular jet sleeve without a target tube; Figure 5 Simulation curves for different target tubes at an electrode spacing of deg=12mm; Figure 6 Simulation curves of multi-segment distribution-ring electrode for large target tubes; Figure 7 The discharge experiment photographs of the target tube in the dynamic processing of Example 1 were used to verify the results. Figure 8 To verify the experimental discharge images and their combinations of the variable tube diameter in Example 2. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings. Specific implementation examples: As attached Figure 1 The diagram shows a schematic of the multi-segment distributed-ring electrode involved in this application. In this embodiment, (a) is a 6-segment distributed electrode structure, and (b) is an electrode and its dimensional parameters of a single-segment annular jet sleeve. The function of this multi-segment distributed-ring electrode is to generate discharge plasma of arbitrary tube length and diameter in the target tube. The function of processing target tubes of arbitrary length is mainly achieved by the structure of the quartz glass shell, such as... Figure 2 (a) The target tube shown is processed through real-time movement, and the discharge plasma within the target tube remains constant throughout the movement. The processing capability for target tubes of arbitrary diameter is primarily achieved by designing a model based on the characteristics and laws of electric field distribution, and by designing appropriate electrode spacing parameters. For ease of modeling and analysis, such as... Figure 2 (b) Target pipes of arbitrary diameter are divided into three typical sizes: large diameter, medium diameter, and small diameter. The inner diameter parameter of the target pipe is... d ti ( dti_l , d ti_m , d ti_s The outer diameter parameter of the target pipe is... d to ( d to_l , d to_m , d to_s The thickness of the target tube medium is... d tt ( d tt_l , d tt_m , d tt_s Based on the actual physical location of the target processing tube, the vertical direction of the target tube was also defined.

[0018] The multi-segment distributed ring-ring electrode and its single-segment annular jet sleeve design model in this application are based on electric field distribution characteristics. The most important design parameter is the spacing between adjacent electrodes. d eg Therefore, the electric field simulation of the design model is mainly aimed at d eg In other words, the electrode spacing d eg The constraints should meet the design requirements. Before processing, the coordinate axis position of each individual electrode segment needs to be calibrated, such as... Figure 3 The diagram shows the typical location field strength coordinates of a single-segment annular jet sleeve without a target tube. Figure 3 (a) is the X-axis electric field calibration diagram located at the central axis of the single-segment annular jet sleeve. Figure 3 (b) is the Y-axis electric field calibration diagram located at the center of the electrode spacing of the single-segment annular jet sleeve, with the coordinate axis points from top (UP) to bottom (DOWN). Figure 3 In (a), we can obtain the electric field values ​​at each point on the central axis of the electrode of the single-segment annular jet sleeve. x 1, E x1 ), ( x 2, E x2 ), ..., ( x n , E xn It can analyze the distribution of the electric field along the X-axis. Simultaneously, Figure 3 (b) represents the electric field value on the Y-axis, (- y n , E -yn), ..., (- y 1. E -y1 ), (0, E y0 ), ( y 1. E y1 ), ..., ( y n , E yn This allows for the analysis of the electric field distribution along the Y-axis. To establish the electrode spacing... d eg The design model defines the effective discharge region length. x dis_c .

[0019] To investigate the variation of the electric field values ​​along the x and y axes under different electrode spacings, the dimensional parameters of a single-segment annular jet sleeve under simulated electrostatic field conditions are shown in Table 1, along with the corresponding coordinate ranges for the x and y axes under different electrode spacings. Without the addition of the target processing tube, the applied electric field is... E apply =4.5kV. Meanwhile, assuming the working gas in the single-section annular jet bushing is He, its breakdown field strength is... E breakdown_He The value is 2.7 kV / cm. The electrostatic field simulation curves for different electrode spacings of a single-segment annular jet sleeve electrode without a target tube are shown below. Figure 4 As shown, where, Figure 4 (a) and (b) are line graphs of the electric field distribution along the X and Y axes, respectively. Figure 4 (c) shows the electrostatic field simulation diagrams with different spacing sizes. The solid line around the ring electrode in the middle of the diagram is the 2.7kV / cm electrostatic field line, and the dashed line represents its effective discharge area.

[0020] Table 1: Electrode Spacing Parameters Without Target Tube from Figure 4 Three important conclusions can be drawn from this analysis. First, the electric field value at the x-axis first increases monotonically and then decreases monotonically, reaching its maximum value at the midpoint of the electrode spacing. Second, the electric field value at the y-axis remains almost constant, indicating that the cross-sectional electric field strength at a fixed x-axis position remains uniform and constant. Third, as the electrode spacing of the single-segment annular jet sleeve increases, the effective discharge region length xdis_c formed by the electric field contour line Ebreakdown_He (2.7kV / cm) gradually decreases to 0mm, indicating that the electric field strength in the center region of the electrode is insufficient to achieve breakdown discharge of the working gas He.

[0021] To achieve the target tube processing capability of single-section annular jet sleeves of arbitrary diameter, it is necessary to analyze the electric field distribution characteristics of the working gas inside target tubes of different diameters to determine the variation law of the effective discharge area length parameter. Table 2 shows... d eg A list of parameters for different target tube sizes at 12mm is provided, along with a calibration diagram of the target tube's dimensional parameters. Figure 2 As shown in Table 2, in the electric field simulation, we selected three typical target tubes with different diameters: large, medium, and small target tubes. The specific dimensional parameters are also shown in Table 2.

[0022] Table 2: d eg Different target tube size parameters under condition =12mm Electrostatic field simulation curves of single-segment annular jet sleeves under different types of target tubes are shown below. Figure 5 As shown. Among them, Figure 5 (a) is a line graph showing the distribution of electric field data on the y-axis. Figure 5 (b) shows the electrostatic field simulation diagrams for different target tubes, with the placement positions as follows: Figure 2 As shown. Figure 5 (b) The solid lines around the ring electrode in the middle position represent the 2.7 kV / cm isoelectric field lines, and the dashed lines represent the effective discharge region. Due to the addition of the target dielectric tube, the electric field strength of He in the target tube will be greatly reduced. To better analyze the change in the effective discharge area length parameter in the target tube xdis_t, the simulated applied electric field strength Eapple is increased to 8 kV.

[0023] Depend on Figure 5 (a) The broken line graph of the electric field Ey along the y-axis shows that, from the up position to the down position in the single-segment annular jet sleeve, the inflection point of the electric field intensity occurs at the contact position of the target tube, that is, the inflection points of the large target tube, the medium target tube, and the small target tube are -4.5mm, -0.5mm, and 2.5mm, respectively. The change in electric field intensity inside the target tube is relatively small.

[0024] exist Figure 5 In (b), under an 8kV applied electric field, the effective discharge area length corresponding to target tubes with different size parameters can be observed. x dis_t The diameters are 9.36mm, 10.85mm, and 11mm respectively, with little difference. Theoretically, it is possible to achieve discharge of the working gas (He) in the target tube. When designing the dimensional parameters of a single-segment annular jet sleeve, we need to ensure that the critical limiting condition for generating discharge plasma in the target tube is the effective discharge area. x dis_t The length should be greater than 0 mm.

[0025] As attached Figure 6 To apply large-sized tubes under different electric field values ​​( E apply Simulated curves of multi-segment distributed ring-ring electrodes: where (a) x - E x (a) Relationship curve, (b) Electrostatic field simulation diagram.

[0026] from Figure 6 As can be seen in (a), when a multi-segment distributed ring-ring electrode is used to process a large target tube, the applied voltage... E apply With the increase in length, the effective discharge area formed by the 2.7 kV / cm electric field lines gradually extends from segment R1-R6 to all segments. Effective discharge area length x dis_tl_Rx The following inequalities must be satisfied: Therefore, the critical condition for the electrode spacing parameter design model of multi-segment distributed-ring electrodes is that, at the desired applied voltage... E apply_designed Below, the effective discharge region length of R2 (R5) is greater than or equal to 0 mm, as shown in the following formula: ; Based on the above design model, when designing the electrode spacing of the multi-segment distributed ring-ring electrode, we need to ensure that the critical condition is met so that the gas in all regions of the multi-segment distributed ring-ring electrode can discharge and generate discharge plasma.

[0027] Verification Example 1: As attached Figure 7 The image shown is a discharge experiment photograph of the multi-segment distributed ring-ring electrode designed using this method for dynamically processing the target tube: Figure 7 (a) is a schematic diagram of the experimental procedure. Figure 7 (b) is a photograph of the emission before movement. Figure 7 (c) is a discharge emission photograph after movement. This verification demonstrates whether the processing function is achieved by observing whether the working gas entering the target tube can achieve gas discharge and generate the corresponding discharge emission photograph of the discharge plasma.

[0028] The target tube selected in the figure is a large-diameter target tube with a length of 1m. Before the experiment, it is necessary to determine the position of the marking characters on the target tube. The position of the light emitted in the square white board-shaped device in the figure is the multi-segment distributed ring electrode designed using the scheme of this application. The high and low voltage of the electrodes are represented by "+" and "-". The tubular object is the target tube to be processed.

[0029] By comparison Figure 7 As can be seen from (b) and (c), all discharge regions R1 to R6 of the multi-segment distributed ring electrode can maintain their discharge state even when they are dynamically moving. Therefore, the multi-segment distributed ring electrode designed in this application can realize the processing function of target tubes with variable tube lengths.

[0030] Verification Example 2: As attached Figure 8 As shown, the processing capability of the multi-segment distributed ring-ring electrode designed using this method was experimentally verified on three typical diameter variable target tubes: large, medium, and small target tubes. The corresponding dimensional data are shown in Table 2. Experimental discharge photographs of different tube diameters and their combinations are shown below. Figure 8 As shown. The experimental target tube conditions included one large target tube, one medium target tube, one small target tube, one medium target tube (#1-M) and one small target tube (#2-S), and combinations of three small target tubes (#1-S, #2-S, #3-S). From... Figure 8 The emission images and combinations of target tubes with different diameters show that, under a given pulse voltage amplitude... U apply_amp Under conditions of 8kV, a pulse repetition frequency of 2kHz, and a gas flow rate of 1L / min, gas discharge in the target tube can be achieved. Therefore, the proposed multi-segment distributed ring-ring electrode can realize the internal surface treatment function of target tubes with different diameters.

[0031] The experimental results above show that the critical design model and method for the effective discharge region length parameter proposed in this invention, based on the electrostatic field coupling superposition model, can ensure that MSC-RRJ has the ability to process the inner wall of a target dielectric tube of any length and the inner surface of dielectric tubes of different diameters. It has a wider range of applications and better compatibility with the inner wall processing of dielectric tubes, which can promote the industrialization process of this type of plasma source device.

[0032] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A parameter design method for a multi-segment distributed electrode based on plasma tube inner wall sterilization, characterized in that: Includes the following steps: Step 1: Establish a 3D simulation model of the multi-segment distributed-ring-tube electrode structure and determine its relevant parameters; the multi-segment distributed-ring-tube electrode structure includes multiple single-segment annular jet tubes; the multi-segment distributed-ring-tube electrode includes a glass tube and multiple electrode rings sleeved on the outer surface of the glass tube; the multiple electrode rings are distributed with high-voltage electrode rings and low-voltage electrode rings interleaved; an adjacent high-voltage electrode ring and a low-voltage electrode ring form a single-segment annular jet tube; relevant parameters include working gas, electrode width, outer diameter of the quartz glass tube, and inner diameter of the quartz glass tube; determine the X-axis electric field verification diagram and Y-axis electric field verification diagram of the discharge region between two adjacent electrodes in the multi-segment distributed-ring-tube electrode structure model; Step 2: Determine the distance between adjacent electrodes of a single-segment annular jet sleeve: Based on the multi-segment distributed-ring sleeve electrode structure model, when there is no target tube in the discharge area, simulate the introduction of the corresponding working gas, and change the distance between the two electrodes of the single-segment annular jet sleeve with a preset external electric field strength to simulate the electric field strength between the electrodes at different electrode distances. The discharge region enclosed by the contour lines of the electric field strength of the preset size, i.e. the critical breakdown voltage, is obtained. If the electric field contour lines of the preset size can form a closed region, then the closed region is the effective discharge region. At the same time, the corresponding distance between electrodes is the critical maximum distance between electrodes to achieve working gas breakdown discharge. Step 3: Determine the length of the effective discharge region of the dielectric tube in the electric field; based on the effective discharge region obtained in Step 2, place target tubes of different preset diameters into the effective discharge region, increase the pulse voltage of the external electric field to the applied electric field strength described in Step 2, and simulate to obtain the effective discharge region enclosed by the electric field contour lines of the preset size; thus, determine the length of the maximum effective discharge region that a single-segment annular jet sleeve can generate in the target tube to be disinfected under the preset electric field strength, electrode spacing, and target tube diameter parameters.

2. The parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection according to claim 1, characterized in that: In step 2, under the applied electric field strength, as the distance between the electrodes increases, the corresponding effective discharge area first increases and then decreases until it becomes 0; when the area of ​​the effective discharge area becomes 0, the electric field strength in the central region between the electrodes is insufficient to break down the working gas discharge.

3. The parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection according to claim 1, characterized in that: In step 2, when the working gas is He gas, the applied electric field strength is 4.5kV, and the simulation yields the preset electric field strength, i.e., the breakdown field strength. E breakdown_He It is 2.7 kV / cm.

4. The parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection according to claim 1, characterized in that: In step 3, when the working gas is He, the intensity of the external electric field is increased to 8kV; the electric field strength of the preset value, i.e., the breakdown field strength, is obtained through simulation. E breakdown_He It is 2.7 kV / cm.

5. The parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection according to claim 1, characterized in that: The working gases include He and Ar.

6. The parameter design method for a multi-segment distributed electrode based on plasma tube inner wall disinfection according to claim 1, characterized in that: It also includes step 4: based on the length corresponding to the maximum effective discharge area of ​​the single-segment annular jet sleeve obtained in step 3, the maximum length that the multi-segment distributed-ring sleeve electrode can process at one time is obtained.

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