Compression waveguide cavity type microwave plasma torch
By designing a compressed waveguide cavity structure, the problems of uneven plasma concentration and carbon adsorption on the quartz tube wall in traditional microwave plasma torch equipment are solved, achieving stable excitation of the plasma torch and system simplification, and making it suitable for common microwave frequencies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- BEIJING GRAPHENE INST
- Filing Date
- 2025-04-08
- Publication Date
- 2026-05-05
AI Technical Summary
Traditional microwave plasma torch equipment suffers from uneven plasma concentration distribution and process instability caused by carbon material adsorption on the quartz tube wall, especially affecting process consistency and stability when preparing carbon-based materials.
The structure employs a compressed waveguide cavity, including an input waveguide, a tapered waveguide, a reaction waveguide, and a connecting waveguide. By setting an air inlet and an observation window, the microwave plasma torch can be stably formed within the waveguide cavity without relying on traditional plasma torch confinement structures such as quartz tubes, ceramic tubes, or metal tubes.
It achieves stable formation of plasma torch in a fixed area, improves electric field strength, simplifies system structure, ensures process stability and consistency, and is applicable to common microwave frequencies.
Smart Images
Figure CN224205299U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of microwave plasma torch technology, specifically to a compressed waveguide cavity type microwave plasma torch. Background Technology
[0002] Microwave plasma torches are increasingly used in materials synthesis and gas cracking catalysis, covering both atmospheric and low-pressure environments.
[0003] However, conventional microwave plasma torch excitation equipment has many limitations. Typically, such equipment requires various structural components to confine and adjust the microwave plasma. For example, a quartz tube system is used to constrain the flow path of the reacting gas, thereby exciting the gas to form plasma; a sliding metal waveguide cutoff plate is placed at the tail end to adjust the microwave intensity range.
[0004] However, this traditional design has significant drawbacks: the microwave generator produces microwaves on one side of the quartz tube, which leads to uneven plasma concentration distribution within the tube, severely affecting the consistency of the process and the final result. Furthermore, in the reaction process of synthesizing certain carbon-based materials using microwave plasma, the quartz tube wall, acting as the reaction torch, readily adsorbs and accumulates carbon materials, leading to plasma extinguishing and greatly hindering the stable progress of the related processes. Utility Model Content
[0005] To address the aforementioned problems, the purpose of this invention is to provide a compressed waveguide cavity type microwave plasma torch suitable for 2.45 GHz microwaves. This structure does not rely on any traditional plasma torch confinement structures, such as quartz tubes, ceramic tubes, metal tubes, carbon-based fiber composite materials, etc., and can achieve stable formation of the plasma torch in a fixed area within the waveguide cavity during microwave transmission. This significantly simplifies the traditional complex microwave plasma torch system. This system is also applicable to common 9.15 MHz microwave systems.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] The compressed waveguide cavity type microwave plasma torch of this utility model includes:
[0008] An input waveguide is provided with a front-end interface at its input end. The input end of the input waveguide is connected to a microwave generator through the front-end interface for inputting microwaves.
[0009] A tapered waveguide, the input end of which is connected to the output end of the input waveguide, is used to compress microwaves and generate standing waves at its output end;
[0010] The first air inlet is connected to the sidewall of the input waveguide at a set angle;
[0011] The second air inlet is connected to the sidewall of the tapered waveguide at a set angle;
[0012] The reactive waveguide and the connecting waveguide are provided, wherein the input end of the reactive waveguide is connected to the output end of the tapered waveguide, the output end of the reactive waveguide is connected to the input end of the connecting waveguide, and the output end of the connecting waveguide forms the nozzle of the flame.
[0013] Preferably, in the compressed waveguide cavity microwave plasma torch, the tapered waveguide tapers from its input end to its output end, and forms a narrow constriction at the output end.
[0014] Preferably, in the compressed waveguide cavity microwave plasma torch, the length and width of the narrow constriction orifice are smaller than the wavelength of the microwave, so as to generate a standing wave at the narrow constriction orifice.
[0015] Preferably, in the compressed waveguide cavity type microwave plasma torch, the angle between the first air inlet and the sidewall of the input waveguide is 15°-30°.
[0016] Preferably, in the compressed waveguide cavity microwave plasma torch, the angle between the second air inlet and the sidewall of the tapered waveguide is 15°-30°.
[0017] Preferably, the compressed waveguide cavity microwave plasma torch further includes a first quartz observation window and a second quartz observation window; the first quartz observation window is disposed on the side wall of the reactive waveguide; and the second quartz observation window is disposed on the side wall of the tapered waveguide.
[0018] Preferably, in the compressed waveguide cavity microwave plasma torch, the connecting waveguide is a straight cylindrical structure or a tapered structure.
[0019] Preferably, the compressed waveguide cavity microwave plasma torch further includes a connecting flange; the output end of the connecting waveguide is connected to the exhaust gas collection device through the connecting flange.
[0020] Preferably, in the compressed waveguide cavity microwave plasma torch, the length of the tapered waveguide is 150mm-200mm; the distance between the first air inlet and the input end of the tapered waveguide and the distance between the second air inlet and the output end of the tapered waveguide are 10mm-55mm respectively, and the distance between the first air inlet and the second air inlet is 120mm-200mm.
[0021] Preferably, the compressed waveguide cavity type microwave plasma torch has two air inlets, one first and one second.
[0022] This utility model has the following advantages due to the adoption of the above technical solution:
[0023] Because the wavelength of microwaves is much larger than the length and width of the output end of the tapered waveguide, microwaves cannot pass through the narrowest region. During the reaction process, a microwave cutoff surface will naturally form, which will cause standing waves to be generated in the waveguide cavity and effectively improve the electric field strength.
[0024] This invention features two air inlets, enabling the entire waveguide cavity to be rapidly filled with reactive gas; the gas flow rate and gas type at the upper and lower air inlets can be flexibly adjusted according to actual needs.
[0025] This invention eliminates the need for any traditional plasma torch confinement structures, such as quartz tubes, ceramic tubes, metal tubes, or carbon-based fiber composite materials, to achieve stable formation of the plasma torch in a fixed region within the waveguide cavity during microwave transmission, significantly simplifying the traditional complex microwave plasma torch system. Attached Figure Description
[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:
[0027] Figure 1 This is a schematic diagram of the main structure of this utility model, wherein the connecting waveguide is a rectangular straight cylinder structure;
[0028] Figure 2 This is a side view of the structure of this utility model;
[0029] Figure 3 This is a top view of the structure of this utility model, wherein the connecting waveguide is a tapered structure;
[0030] Figure 4 This is a diagram showing the gas velocity intensity distribution when air is simultaneously introduced through the first and second air inlets.
[0031] Figure 5 This is a diagram showing the gas flow direction when the first and second air inlets are inlet simultaneously.
[0032] The labels for the attached figures are as follows:
[0033] 1-Input waveguide; 2-Front-end interface; 3-Tapered waveguide; 4-First air inlet; 5-Second air inlet; 6-Response waveguide; 7-Connecting waveguide; 8-First quartz observation window; 9-Second quartz observation window; 10-Connecting flange. Detailed Implementation
[0034] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
[0035] This invention provides a compressed waveguide cavity type microwave plasma torch. This structure does not rely on any traditional plasma torch constraint structure, such as quartz tube, ceramic tube, metal tube, carbon-based fiber composite material, etc., and can achieve stable formation of the plasma torch in the fixed area within the waveguide cavity during microwave transmission, which significantly simplifies the traditional complex microwave plasma torch system.
[0036] like Figure 1 As shown, the compressed waveguide cavity type microwave plasma torch provided by this utility model includes:
[0037] Input waveguide 1 has a front-end interface 2 at its input end. The input end of input waveguide 1 is connected to a microwave generator (not shown in the figure) through the front-end interface 2 for inputting microwaves.
[0038] Tapered waveguide 3, whose input end is connected to the output end of input waveguide 1, is used to compress microwaves and generate standing waves at its output end;
[0039] The first air inlet 4 is connected to the side wall of the input waveguide 1 at a set angle;
[0040] The second air inlet 5 is connected to the side wall of the tapered waveguide 3 at a set angle;
[0041] The reactive waveguide 6 and the connecting waveguide 7 are connected. The input end of the reactive waveguide 6 is connected to the output end of the tapered waveguide 3, and the output end of the reactive waveguide 6 is connected to the input end of the connecting waveguide 7. The output end of the connecting waveguide 7 forms the nozzle of the plasma flame.
[0042] In the above embodiments, preferably, as follows: Figure 2 As shown, the tapered waveguide 3 tapers from its input end to its output end, forming a narrow opening at the output end. Specifically, the long side of the cavity of the tapered waveguide is compressed from 109.22 mm to 70 mm, and the short side is compressed from 54.61 mm to 20 mm.
[0043] In the above embodiments, preferably, the length and width of the narrow opening are smaller than the wavelength of the microwave, so as to generate a standing wave at the narrow opening. Therefore, the microwave cannot pass through the narrowest region, and a microwave cutoff surface will naturally form during the reaction process, causing a standing wave to be generated within the waveguide cavity, effectively increasing the electric field strength.
[0044] In the above embodiments, preferably, the angle between the first air inlet 4 and the sidewall of the input waveguide 1 is 15°-30°, and most preferably 20°;
[0045] In the above embodiments, preferably, the angle between the second air inlet 5 and the sidewall of the tapered waveguide 3 is 15°-30°, and most preferably 20°.
[0046] The angle setting not only ensures that the reactive gas quickly fills the cavity and is transported stably, preventing gas backflow during plasma torch excitation, but also greatly facilitates the formation of the plasma torch, creating the highest gas flow rate at the narrowing point of the cavity, ensuring that the excited plasma torch is always at the rear outlet position.
[0047] In the above embodiments, preferably, the present invention further includes a first quartz observation window 8 and a second quartz observation window 9; the first quartz observation window 8 is disposed on the side wall of the reactive waveguide 6; the second quartz observation window 9 is disposed on the side wall of the tapered waveguide 3. Thus, the internal conditions can be observed.
[0048] In the above embodiments, preferably, the connecting waveguide 7 is a cylindrical structure or a tapered structure. The cylindrical structure is as follows: Figure 1 As shown, the tapered structure is as follows Figure 3 As shown.
[0049] In the above embodiments, preferably, as follows: Figure 1 As shown, this utility model also includes a connecting flange 10; the output end of the connecting waveguide 7 is connected to the exhaust gas collection device (not shown in the figure) through the connecting flange 10 for the purpose of recovering exhaust gas.
[0050] In the above embodiments, preferably, as follows: Figure 3 As shown, the length of the tapered waveguide 3, from a to b, is 150mm-200mm; the distance from the first air inlet 4 to the input end of the tapered waveguide 3, i.e. a, and the distance from the second air inlet 5 to the output end of the tapered waveguide 3, i.e. b, are 10mm-55mm respectively, and the distance between the first air inlet 4 and the second air inlet 5 is 120mm-200mm.
[0051] In the above embodiments, preferably, there are two first air inlets 4 and two second air inlets 5.
[0052] Figure 4 The diagram shows the gas velocity intensity distribution when the first and second air inlets are inlet simultaneously. As can be seen from the diagram, the gas flows stably within the cavity.
[0053] Figure 5The diagram shows the gas flow direction when the first and second air inlets are inlet simultaneously. As can be seen from the diagram, the gas flows in the cavity and eventually fills the rear port, which is beneficial for the microwave energy to ionize the gas in the compression zone to form a plasma torch.
[0054] This invention features a first and a second air inlet, enabling the entire waveguide cavity to be rapidly filled with reactive gas. The gas flow rate and gas type at the upper and lower inlets can be flexibly adjusted according to actual needs. The actual reactive gases can be selected according to their ionization energy, with the priority order being H2O>CO2>N2>O2>Ar>Ne. When using gases with low ionization energy (such as Ar and Ne), the strong electric field formed by the narrowing region can directly excite the plasma torch. When using gases with high ionization energy (such as H2O, CO2, and air), the plasma torch can be manually ignited from the rear end using an external metal wire.
[0055] Example 1:
[0056] Connect the front-end interface 2 of the compressed waveguide structure described in this utility model to the microwave generator, and adjust the microwave generator to ensure optimal microwave input within the waveguide structure. The output end connecting to waveguide 7 uses a KF40 flange interface. To ensure airtightness, the interface surface must be carefully cleaned and an appropriate amount of sealing silicone grease applied before connecting to the collector or exhaust pipe. The first inlet 4 and the second inlet 5 are connected via corrosion-resistant gas pipelines with the same inner diameter, and a high-precision mass flow controller is used to achieve a stable gas flow supply: high-purity argon is introduced into the first inlet, with the flow rate precisely controlled at 2 SLM (fluctuation range controlled within ±0.05 SLM); high-purity argon is introduced into the second inlet, with the initial flow rate set to 4 SLM, ensuring the lower gas flow rate is greater than the upper gas flow rate. Start the microwave power supply and set the output power to 1KW. After the power is turned on, the argon plasma torch can be observed to be successfully excited in the narrowing region. The torch is bright blue-white and has a shape similar to a cone, with the bottom located in the narrowing region and the tip extending towards the tail end. After the torch is stably excited, the argon flow rate at the lower inlet is gradually increased by 1 SLM each time. When the flow rate reaches 8 SLM, the torch length is significantly extended (by about 50% to 80%), and the overall brightness is enhanced. The surrounding gas is strongly ionized, thus creating a working environment suitable for high-temperature reaction conditions.
[0057] Example 2:
[0058] Connect the front-end interface 2 of the compressed waveguide structure described in this utility model to the microwave generator. Adjust the microwave generator to ensure optimal microwave input within the waveguide structure. The output end connecting the waveguide 7 uses a KF40 flange interface. To ensure airtightness, the interface surface must be carefully cleaned and an appropriate amount of sealing silicone grease applied before connecting to the collector or exhaust pipe. The first air inlet 4 and the second air inlet 5 are connected via corrosion-resistant gas pipelines with the same inner diameter, and a high-precision mass flow controller is used to achieve a stable gas flow supply: high-purity nitrogen is introduced into the first air inlet, with the flow rate precisely controlled at 8 SLM (fluctuation range controlled within ±0.05 SLM); high-purity nitrogen is introduced into the second air inlet, with the initial flow rate set to 16 SLM, ensuring that the lower gas flow rate is greater than the upper gas flow rate. Start the microwave power supply and set the output power to 1KW. After the power supply is started, use an external metal wire (iron, copper, tungsten) to quickly insert upwards from the rear end into the contraction zone and remove it. A purple nitrogen plasma torch will then be seen ejected. Appropriately increasing the flow rate at the lower air inlet can extend the torch length.
[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A compressed waveguide cavity type microwave plasma torch, characterized in that, include: An input waveguide is provided with a front-end interface at its input end. The input end of the input waveguide is connected to a microwave generator through the front-end interface for inputting microwaves. A tapered waveguide, the input end of which is connected to the output end of the input waveguide, is used to compress microwaves and generate standing waves at its output end; The first air inlet is connected to the sidewall of the input waveguide at a set angle; The second air inlet is connected to the sidewall of the tapered waveguide at a set angle; The reactive waveguide and the connecting waveguide are provided, wherein the input end of the reactive waveguide is connected to the output end of the tapered waveguide, the output end of the reactive waveguide is connected to the input end of the connecting waveguide, and the output end of the connecting waveguide forms the nozzle of the flame.
2. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, The tapered waveguide tapers from its input end to its output end, forming a narrow opening at the output end.
3. The compressed waveguide cavity type microwave plasma torch according to claim 2, characterized in that, The length and width of the narrow constriction aperture are smaller than the wavelength of the microwave, so as to generate a standing wave at the narrow constriction aperture.
4. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, The angle between the first air inlet and the sidewall of the input waveguide is 15°-30°.
5. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, The angle between the second air inlet and the sidewall of the tapered waveguide is 15°-30°.
6. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, It also includes a first quartz observation window and a second quartz observation window; The first quartz observation window is disposed on the sidewall of the reactive waveguide; The second quartz observation window is disposed on the sidewall of the tapered waveguide.
7. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, The connecting waveguide has a straight cylindrical structure or a tapered structure.
8. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, It also includes connecting flanges; The output end of the connecting waveguide is connected to the exhaust gas collection device via a connecting flange.
9. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, The length of the tapered waveguide is 150mm-200mm; The distance between the first air inlet and the input end of the tapered waveguide and the distance between the second air inlet and the output end of the tapered waveguide are 10mm-55mm, respectively, and the distance between the first air inlet and the second air inlet is 120mm-200mm.
10. The compressed waveguide cavity microwave plasma torch according to claim 1, characterized in that, There are two air inlets, one first and one second.