Orthogonal multi-electrode combined plasma heater

Abstract

The invention provides an orthogonal multi-electrode combined plasma heater. The plasma generator is characterized in that the plasma generator is formed by embedding at least two groups of plasma generators, each group of plasma generator is composed of an electrode bar and an insulating electrode holder, current loops of the plasma generators are mutually independent, the plasma generators are circularly and symmetrically distributed, and formed plasma arc ring heating temperature zones are uniformly distributed in an annular sheet shape; the optical fiber penetrates along the central axis of the heating temperature area, the temperature is adjusted by adjusting the number of the plasma generators, and the needle point distance of an electrode bar in the plasma generators is adjusted to adapt to the diameter of the optical fiber to be processed. On the basis of arc discharge optical fiber hot processing, under the condition that it is guaranteed that the optical fibers are heated evenly, the processing and preparing requirements of large-diameter silica optical fibers such as optical fiber welding, steep cone tapering, short-pitch torsion and optical fiber end microsphere firing can be met, and the hot processing technology of different optical fiber types is achieved. The method is suitable for the optical fiber processing field.

Description

Technical Field

[0001] The invention relates to an orthogonal multi-electrode combined plasma heater, which can be used for processing and preparing large-diameter quartz optical fibers such as optical fiber welding, steep cone tapering, short pitch twisting, and optical fiber end microsphere sintering, so as to meet different types of thermal processing requirements for optical fibers, and belongs to the field of optical fiber processing. Background Art

[0002] In the field of optical fiber thermal processing, arc plasma has a higher electrical-to-thermal conversion efficiency than laser, and reactive gases can be introduced for chemical removal. It can maintain the high quality of plasma processing while having the high efficiency of laser heat removal, which has important research significance for the processing of large-diameter and high-precision optical components.

[0003] Arc discharge is widely used in long-period fiber grating writing and melt taper. Long-period fiber gratings prepared by arc discharge have good thermal stability at high temperatures. The arc discharge method is that during the axial movement of the optical fiber, the electrode periodically discharges the optical fiber to form a long-period fiber grating. This method is simple and easy to control. It does not require doped optical fiber and optical fiber hydrogen loading. It can be adjusted by adjusting the size of the arc current and the size of the heated area of ​​the optical fiber. However, in the case of different optical fiber diameters such as optical fiber preform taper and large pitch torsion, the existing arc discharge based on plasma generation device has a small temperature zone and uncontrollable temperature, and cannot adapt to the thermal processing conditions of large core diameter optical fiber.

[0004] To solve the above problems, a patent for a large constant temperature zone four-electrode arc discharge high temperature optical fiber processing device is proposed. In the method proposed in (CN113820786A), the axis of the electrode rod and the axis of the optical fiber are in the same plane, which widens the range of the constant temperature zone and overcomes the problem of the narrow constant temperature zone of the arc discharge in the axial direction of the optical fiber. However, it does not solve the problem that in the thermal processing of optical fiber with large core diameter, when the core diameter is too large and exceeds the plane of the temperature zone, it is easy to cause uneven thermal processing. At the same time, when the external air flow fluctuates, the temperature of the plane temperature zone is easily disturbed. The method proposed in the patent multi-electrode system (CN200880008726) improves the problem of narrow temperature zone and reduces air flow disturbance. However, when used, the electrodes need to be arranged in a partial vacuum or absolute vacuum. The processing conditions are harsh and it is not suitable for large pitch long distance torsion processing. The patent for a multi-electrode AC arc discharge device, equipment and AC power supply (CN113727483A) mainly solves the problem of generating continuous and uniform large-volume plasma, but it is often used for powder material processing and preparation, and is not suitable for optical fiber thermal processing.

[0005] At present, the thermal processing requirements of different types of optical fibers such as steep cone drawing, short pitch twisting, etc. for large-diameter optical fiber drawing are all based on oxyhydrogen flame optical fiber thermal processing, etc., and no large-diameter optical fiber thermal processing technology based on arc plasma has been found. However, the temperature of the oxyhydrogen flame may be difficult to accurately control, which may cause inconsistency in the optical fiber during processing. Due to the high temperature of the oxyhydrogen flame, the optical fiber material may be damaged, especially in high-power applications, where thermal damage or melting may occur. The use of oxyhydrogen flame may produce harmful byproducts and have potential negative impacts on the environment. At the same time, hydrogen is a flammable and explosive gas, and special attention should be paid to safety during operation, and the safety requirements for operators are high. As the requirements for precision and repeatability of optical fiber devices increase, oxyhydrogen flame processing may be difficult to meet the needs of high precision and high repeatability. In order to maintain stability during oxyhydrogen flame processing, a complex gas path system may be required, which may increase production costs.

[0006] The invention discloses an orthogonal multi-electrode combined plasma heater. It can be used for thermal processing requirements of different optical fiber types such as large-diameter optical fiber drawing, steep cone drawing, short pitch twisting, etc., and belongs to the field of optical fiber device processing technology. By designing the size of the insulating electrode seat and the angle of the electrode rod to change the arc width, it is suitable for thermal processing of optical fibers of different diameters. By adjusting the number of plasma generators to adjust the temperature, it can adapt to the thermal processing requirements of optical fibers of different sizes and different temperatures. Summary of the invention

[0007] The purpose of the present invention is to provide an orthogonal multi-electrode combined plasma heater. This device can be used to meet the thermal processing requirements of different optical fiber types such as large-diameter optical fiber drawing, steep cone drawing, short pitch twisting, etc., and can be widely used in optical fiber thermal processing systems.

[0008] The object of the present invention is achieved in that:

[0009] An orthogonal multi-electrode combined plasma heater is characterized in that the device comprises: a plasma generator, which is composed of an insulating electrode seat and an electrode rod and is used to generate a plasma arc.

[0010] The number of the plasma generators is no less than two groups, and each group of plasma generators is combined by embedding the insulating electrode seats in each group. The embedding positions are circularly symmetrically distributed. After discharge, the circular center area presents an annular thin sheet temperature zone. The circumferential center area is the optical fiber processing area. The processing optical fiber passes through the processing area along the axial direction and is orthogonal to the fire arc. The current circuits of each group of plasma generators are independent of each other, and the temperature of the processing temperature zone is adjusted by changing the number of plasma generators.

[0011] The electrode rod is embedded or bolted to the insulating electrode seat, and the area where the needle tips of the two face each other is the plasma arc generation area. The length of the plasma arc generation area can be changed by adjusting the needle tip distance.

[0012] The center angle of the insulating electrode seat is set according to the number of plasma generators, and the positions are distributed in a circular symmetrical manner.

[0013] The lateral area of ​​the insulating electrode seat can be set according to the radius of the processed optical fiber, and its calculation formula is as follows:

[0014] Among them, R is the outer radius of the insulated electrode seat, L is the length of the electrode rod, r is the radius of the large core diameter optical fiber, θ is the angle of the electrode rod tip deviating from the center of the circle, and n is the number of plasma generators. The corresponding lateral area of ​​the insulated electrode seat is selected by the known optical fiber diameter, the purpose of which is to select a suitable area to save device space.

[0015] The volume of the insulating electrode seat can be set according to the radius of the processed optical fiber, and the calculation formula is as follows:

[0016] Among them, R is the outer radius of the insulating electrode seat, L is the length of the electrode rod, r is the radius of the large core fiber, θ is the angle of the electrode rod tip deviating from the center of the circle, n is the number of plasma generators, and h is the thickness of the insulating electrode seat. The corresponding lateral area of ​​the insulating electrode seat is selected by the known fiber diameter, with the purpose of selecting the appropriate volume for heat dissipation.

[0017] The central angle of the insulating electrode seat can be set according to the device radius and the chord length of the insulating electrode seat, and its calculation formula is as follows:

[0018] Where c is the chord length of the insulated electrode holder, and r1 is the angle at which the electrode tip deviates from the center of the circle. The corresponding center angle of the insulated electrode holder is calculated by the known optical fiber diameter, and the purpose is to select the appropriate electrode rod length and deflection angle by the center angle.

[0019] The plasma discharge satisfies the following rules.

[0020] Arc discharge is an important form of gas discharge. It is difficult to give a strict definition of arc discharge. The most significant feature that distinguishes it from other gas discharge stages is that it will present an upward curved arc and produce a very high temperature hot plasma during the discharge process. The positive and negative electrodes are broken down by high voltage discharge to form a loop. The cathode emits an electron flow to the anode. The electron flow is constantly accelerated in the process of moving toward the anode, gaining extremely high energy, colliding with neutral gas molecules and atoms between the electrodes, transferring energy to neutral particles, and the gas is strongly ionized to produce ions and free electrons, accompanied by strong luminescence and heat release. The electrons generated by gas ionization further collide with non-ionized neutral gas particles, thereby producing avalanche ionization.

[0021] Gas breakdown is an important phenomenon in the gas discharge process. When the voltage across the gas discharge tube is small, the gas discharge current is very weak. On this basis, when the voltage across the two ends is increased, the current does not increase significantly. However, when the voltage increases to a certain level, the current passing through the gas gap will increase sharply, and the gas will show the characteristics of a conductor. This phenomenon is called gas breakdown, and the corresponding critical voltage is called breakdown voltage.

[0022] The breakdown voltage is an important parameter of gas discharge, which is related to factors such as electrode material, gas medium, inter-electrode distance, gas pressure, etc. Paschen derived a method for calculating the breakdown voltage of gas under uniform field strength, which is called Paschen's law. The calculation formula is as follows: Among them, P is the gas pressure, d is the inter-electrode distance, and A, B, and γ are constants related to the gas type and metal material. According to Paschen's law, when the metal material and gas medium are determined, the breakdown voltage is a function of the product of the gas pressure and the inter-electrode distance. In addition, as the product of the gas pressure and the inter-electrode distance increases, the breakdown voltage first decreases and then increases. By setting the breakdown voltage parameters, the inter-electrode distance can be changed. Increase the working range.

[0023] Compared with the prior art, the double-ring cage-shaped multi-electrode combined plasma high-temperature furnace proposed by the present invention has at least the following advantages:

[0024] (1) The device has high reliability, simple structure, simple electrode rod installation, high feasibility of optical fiber thermal processing, and is suitable for mass production.

[0025] (2) Improve temperature diversity. During the thermal processing of optical fibers, in addition to increasing the breakdown voltage parameters and increasing the power to increase the temperature of the processing zone, the number of plasma generators can also be increased to increase the temperature of the temperature zone. The temperature at the center of the circle increases as the number of plasma generators increases.

[0026] (3) The processing efficiency is stable. During the optical fiber thermal processing, because the processed optical fiber does not directly pass through the fire arc, when the breakdown voltage peak changes instantaneously, it will not directly affect the heating of the optical fiber.

[0027] (4) Improve processing quality. During the optical fiber thermal processing, because the processed optical fiber does not directly pass through the fire arc, the impact of metal splashing from the electrode rod is greatly reduced.

[0028] (5) There are a variety of optical fiber processing types, which can be applied to the thermal processing needs of different optical fiber types such as large-diameter optical fiber drawing, steep cone drawing, short-pitch twisting, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of an orthogonal multi-electrode combination plasma heater;

[0030] Figure 2 It is a schematic diagram of the structure of an orthogonal eight-electrode combination plasma heater;

[0031] Figure 3 It is a schematic diagram of the current loop structure of an orthogonal eight-electrode combination plasma heater;

[0032] Figure 4 It is a schematic diagram of the structure of an orthogonal four-electrode combination plasma heater;

[0033] Figure 5 It is a schematic diagram of the current loop structure of an orthogonal four-electrode combination plasma heater and a temperature diagram of the arc-heated optical fiber;

[0034] In the figure:

[0035] 1-plasma generator, 2-insulated electrode holder, 301-electrode rod, 302-electrode rod. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments. In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The invention discloses an orthogonal multi-electrode combined plasma heater.

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Figure 2This is a schematic diagram of the structure of an orthogonal eight-electrode combination plasma heater. It includes: a plasma generator, which is composed of an insulated electrode seat and an electrode rod, and is used to generate a plasma arc. The number of plasma generators is four groups, and each group of plasma generators is combined by the insulated electrode seat in each group. The insulated positions are distributed in a circular symmetrical manner. After discharge, the central area of ​​the circle presents an annular thin-sheet temperature zone, and the central area of ​​the circle is the optical fiber processing area. The processing optical fiber passes through the processing area in the axial direction and is orthogonal to the arc. The electrode rod is embedded or bolted to the insulated electrode seat, and the area where the needle tips of the two are opposite is the plasma arc occurrence area. The length of the plasma arc occurrence area can be changed by adjusting the needle tip distance. The center angle of the insulated electrode seat is set according to the number of plasma generators, and the positions are distributed in a circular symmetrical manner. Assuming that the radius r of the processed optical fiber is 2 mm, the inner radius of the plasma generator is 5 cm, the outer radius of the plasma generator is the electrode rod length L = 2 cm, and the electrode rod tip deviation angle θ is 12°, the lateral area of ​​the insulated electrode seat S = 161.0065 mm is calculated according to formula (1) and formula (2): 2 , volume of insulated electrode holder V = 805.0331 mm 3 , the central angle of the insulating electrode holder θ r =44.97°, and the appropriate area is selected through relevant parameters to save device space and maintain good heat dissipation conditions.

[0040] Figure 3 The invention is a schematic diagram of the current loop structure of an orthogonal eight-electrode combination plasma heater. The invention comprises a plasma generator, which is composed of an insulating electrode seat and an electrode rod and is used to generate a plasma arc. The number of the plasma generators is four.

[0041] In the system, the two electrode rods in each of the four groups of electrode rods are opposite to each other, forming a quadrilateral processing temperature zone centered on the processed optical fiber. The needle tip potential is from A+, B+, C+, D+ to A-, B-, C-, D-, and the four current loops are independent of each other and do not affect each other. At the same time, the distance between the needle tips of each group of electrode rods is adjusted. As the arc lengthens, the four different arcs continue to approach the center optical fiber position, forming a higher temperature area in the longitudinal center. When the optical fiber passes through the central area axially, it will not be affected by the arc plasma. Based on this temperature field, large-diameter optical fiber drawing, steep cone drawing, short pitch twisting and other different optical fiber types can meet the thermal processing requirements.

[0042] Example 2

[0043] Figure 4This is a schematic diagram of the structure of an orthogonal four-electrode combination plasma heater. It includes: a plasma generator, which is composed of an insulating electrode seat and an electrode rod, and is used to generate a plasma arc. The number of the plasma generators is two groups, and each group of plasma generators is combined by the insulating electrode seat in each group. The embedded positions are distributed in a circular symmetrical manner. After discharge, the central area of ​​the circle presents an annular thin sheet-like temperature zone, and the central area of ​​the circle is the optical fiber processing area. The processing optical fiber passes through the processing area in the axial direction and is orthogonal to the arc. The electrode rod is embedded or bolted to the insulating electrode seat, and the area where the needle tips of the two are opposite is the plasma arc occurrence area. The length of the plasma arc occurrence area can be changed by adjusting the needle tip distance. The center angle of the insulating electrode seat is set according to the number of plasma generators, and the positions are distributed in a circular symmetrical manner. Assuming that the radius r of the processed optical fiber is 2 mm, the inner radius of the plasma generator is 5 cm, the outer radius of the plasma generator is the electrode rod length L = 2 cm, and the electrode rod tip deviation angle θ is 12°, the lateral area of ​​the insulated electrode seat S = 91.627 mm is calculated according to formula (1) and formula (2): 2 , Insulated electrode holder volume V = 476.325 mm 3 , the central angle of the insulating electrode holder θ r =89.47°, and the appropriate area is selected through relevant parameters to save device space and maintain good heat dissipation conditions.

[0044] Figure 5 The figure on the left is a schematic diagram of the current loop structure of an orthogonal four-electrode combination plasma heater. It includes: a plasma generator, which is composed of an insulated electrode seat and an electrode rod, and is used to generate a plasma arc. The number of the plasma generators is two groups. In the system, the two electrode rods in each group of two groups of electrode rods are opposite to each other, forming a quadrilateral processing temperature zone centered on the processed optical fiber. The needle tip potential is from A+, B+ to A-, B-. The two current loops are independent of each other and do not affect each other. At the same time, the distance between the needle tips of each group of electrode rods is adjusted. While the arc is elongated, the two different arcs continue to approach the center optical fiber position, forming a higher temperature area in the longitudinal center. When the optical fiber passes through the central area axially, it will not be affected by the arc plasma. Based on this temperature field, the thermal processing requirements of different optical fiber types such as steep cone drawing, short pitch twisting, etc. of large-diameter optical fiber drawing are met.

[0045] Figure 5The figure on the right is a simple implementation example of an orthogonal four-electrode combination plasma heater and a temperature diagram of an arc-heated optical fiber. (a) in the figure shows an actual orthogonal four-electrode combination plasma heater and the distribution position of the optical fiber. The distance between the needle tips of the two sets of electrode rods is 3 mm. The optical fiber is located in the center area of ​​the two sets of electrode rods. The breakdown voltage is started to generate an arc. (c) in the figure shows the temperature distribution of the optical fiber during the thermal processing of the optical fiber. The highest temperature fluctuates around 1100°C. The temperature diagram can be used to reasonably arrange the positions of the electrode rods, providing feasibility for multi-electrode combinations.

[0046] The present invention and its implementation methods are described schematically above, and the description is not restrictive. The drawings show only one implementation method of the present invention, and the actual structure and method are not limited thereto. Therefore, if a person skilled in the art is inspired by the invention and designs a structure and implementation method similar to the technical solution without creativity without departing from the purpose of the invention, they all fall within the protection scope of the present invention.

Claims

1. An orthogonal multi-electrode combined plasma heater, characterized in that the device include: A plasma generator (1) is composed of an insulating electrode base (2), an electrode rod (301), and an electrode rod (302).

2. The orthogonal multi-electrode combined plasma heater according to claim 1, characterized in that: Each group of plasma generators (1) is joined and combined through an insulating electrode seat (2) in each group, and the joining positions are distributed in a circular symmetry. The processing optical fiber passes through the processing area along the axial direction and is orthogonal to the fire arc. The current loops of each group of plasma generators (1) are independent of each other.

3. The orthogonal multi-electrode combined plasma heater according to claim 1, characterized in that: The number of the plasma generators (1) is n groups, and the relationship between n and the center angle of the circle is a multiple relationship, and n is not less than 2.

4. The orthogonal multi-electrode combined plasma heater according to claim 1, characterized in that: The electrode rod (301) and the electrode rod (302) are fixed to the insulating electrode seat (2), and the area where the needle tips of the two face each other is the plasma arc generation area, and the distance between the needle tips can be adjusted.

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