Nozzle-restricted gas arc diagnosis device and method based on Schlieren method

Abstract

The present invention discloses a nozzle-limited gas arc diagnosis device and method based on the Schlieren method, the device comprising: a Schlieren light source and a concave reflector group, a gas arc nozzle stabilizing device, a knife edge and an imaging collection mirror group; the Schlieren light source and the concave reflector group comprise an LED light source, a calibration lens, two concave reflectors, and a reflector; the gas arc nozzle stabilizing device comprises a static contact and a fixture thereof, a gas nozzle, a moving contact and a fixture thereof; the knife edge and the imaging collection mirror group comprises an imaging reflector, a knife edge, a spatial filter, a narrowband filter, an imaging lens, and a high-speed camera. The present invention has the characteristics of strong gas arc targeting, high data measurement signal-to-noise ratio, and clear Schlieren imaging. It realizes the collection of Schlieren signals for the pain point that the gas arc is difficult to measure, and filters the arc self-emission noise in a targeted manner to obtain Schlieren signal data with a higher signal-to-noise ratio, and finally obtains the flow field and temperature field data of the gas arc.

Description

Technical Field

[0001] The invention relates to the field of gas arc plasma diagnosis, and in particular to a gas arc plasma diagnosis device and method under nozzle restriction conditions based on a schlieren method. Background Art

[0002] Gas arc is the core research object in gas electrical appliances, and the measurement of its flow field and temperature field is of great significance for analyzing the arc extinguishing mechanism of electrical appliances. The Schlieren method collects and analyzes the refractive index information in the parallel-deflected light passing through the gas arc plasma, and then obtains the flow field and temperature field information of the target object. The traditional Schlieren method is mostly used for fluid measurement objects with weak self-luminescence and low resolution requirements, such as flames, wind tunnel flow field tests, etc.

[0003] The gas arc itself has strong self-luminescence, which will cover most of the effective information and cause overexposure of the camera compared to the background light source of the schlieren. And due to the high instability of the gas arc morphology, it is difficult to ensure that the schlieren is in an axisymmetric state at the time of shooting, which in turn affects the quantitative post-processing of the schlieren. At the same time, due to the extremely fast development and decay speed of the gas arc, the requirements for time and space resolution are extremely high. All these factors make it difficult to apply the schlieren method to the diagnosis of gas arc plasma.

[0004] Therefore, how to provide a schlieren measurement system for gas arc plasma that can solve the above problems is an issue that urgently needs to be solved in the art. Summary of the invention

[0005] In view of this, the present invention provides a flow field and temperature field diagnostic measurement device and method for gas arc based on the schlieren method, which effectively realizes the schlieren diagnosis of gas arc by improving the efficiency of the light source through the correction of the schlieren light source, stabilizing the plasma through a specific gas blowing nozzle, and improving the signal-to-noise ratio through a narrow-band-spatial filter.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A nozzle-restricted gas arc diagnostic device based on the Schlieren method comprises: a Schlieren light source and a concave reflector group, a gas arc nozzle stabilizing device, a knife edge and an imaging collection mirror group.

[0008] The Schlieren light source and concave reflector group includes: an LED light source, a collimating lens, two concave reflectors, and a reflector.

[0009] The knife edge and imaging collection mirror group comprises: an imaging reflector, a knife edge, a spatial filter, a narrow-band filter, an imaging lens, and a high-speed camera.

[0010] The LED light is corrected by the calibration lens and the reflector and then goes to the first concave reflector. After being converged into parallel light, it enters the gas arc object in the gas arc nozzle stabilization device. After being focused by the second concave reflector, it is reflected by the imaging reflector and cut by the knife edge to produce a Schlieren image. The image is imaged and filtered by the imaging lens, narrowband filter and spatial filter to produce a high-quality and clear Schlieren signal, which is finally collected by a high-speed camera.

[0011] Furthermore, the gas arc nozzle stabilizing device comprises: a stationary contact and a clamp thereof, a gas nozzle, a moving contact and a clamp thereof.

[0012] Furthermore, the LED light source is a continuously dimming single-color LED, preferably a continuously dimming single-color LED with a power of 50W.

[0013] Furthermore, the calibration lens has a diameter of 2 inches, the two concave mirrors have a diameter of 100 mm, a focal length of 1000 mm, and a reflector has a diameter of 50 mm.

[0014] Furthermore, the gas nozzle has a pair of through holes as light paths and windows along the direction of transmission of the Schlieren light, and the through holes are covered with quartz glass. The gas enters the nozzle through the opening inside the static contact, and then blows the arc downward along the pipeline formed by the nozzle and the contact.

[0015] Furthermore, the knife edge is cut vertically, the narrowband filter is a filter that allows the central wavelength of the light source to be ±3nm, and the imaging lens has a diameter of 2 inches.

[0016] The present invention also proposes a method for collecting schlieren signals of a gas arc, comprising the following steps:

[0017] Step 1: The Schlieren LED light is focused by the calibration lens and then goes to the first concave reflector;

[0018] Step 2, adjusting the position and angle of the first concave reflector so that the schlieren light passes through the gas arc plasma in parallel;

[0019] Step 3: Adjust the angle and position of the gas arc nozzle so that the window is located at the center of the Schlieren light spot and faces the direction of the incoming light;

[0020] Step 4: adjust the second concave reflector so that the received Schlieren parallel light is focused on the knife edge behind the reflector, and adjust the knife edge and the imaging lens so that the Schlieren signal enters the high-speed camera;

[0021] Furthermore, the concave mirror, reflector, lens and filter through which the Schlieren LED light passes must all be coaxial.

[0022] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a device and method for schlieren imaging and signal collection of gas arcs at nozzles in electrical appliances, which achieves the stabilization of the gas arc and the penetration of the schlieren light source by cleverly designing a specific nozzle, and based on the limited installation conditions of the gas arc extinguishing chamber, the schlieren light source is converged and corrected, and the concave reflector group and the reflector group are constructed and debugged to achieve the imaging and collection of the gas arc schlieren signal, and the spontaneous light and stray light generated in the schlieren signal collection process are filtered through spatial and narrow-band filters, thereby effectively improving the signal-to-noise ratio.

[0023] The advantages of the present invention are:

[0024] Compared with the traditional Schlieren system, which has the disadvantages of difficulty in measuring objects with strong self-luminescence and low resolution, the present invention has the characteristics of strong gas arc targeting, high data measurement signal-to-noise ratio, and clear Schlieren imaging. It realizes the collection of Schlieren signals to address the pain point that gas arc is difficult to measure, and performs targeted filtering of its arc self-emission noise to obtain Schlieren signal data with a higher signal-to-noise ratio, and finally obtains the flow field and temperature field data of the gas arc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the main structure of the system of the present invention; wherein, the schlieren LED light source 1, the collimating lens 2, the reflector 3, the concave reflector 4, the gas arc nozzle stabilizing device 5, the imaging reflector 6, the knife edge 7, the imaging lens 8, the narrowband filter 9, the spatial filter 10, and the high-speed camera 11;

[0026] FIG2( a ) is a schematic diagram of a gas arc nozzle system in the system of the present invention;

[0027] FIG2( b ) is a cross-sectional view of the gas arc nozzle system in the system of the present invention;

[0028] Among them, the static contact fixture 12, the PTFE nozzle housing 13, the window glass 14, the moving contact and fixture 15, and the plasma area 16;

[0029] Figure 3 Schematic diagram of the schlieren flow field of a gas arc object photographed by the present invention;

[0030] Figure 4 This is the temperature test result diagram. DETAILED DESCRIPTION

[0031] The following will refer to the attached Figures 1 to 4Specific embodiments of the present disclosure are described in detail. Although specific embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0032] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present disclosure, but the description is based on the general principles of the specification and is not used to limit the scope of the present disclosure. The scope of protection of the present disclosure shall be determined by the attached claims.

[0033] To facilitate understanding of the embodiments of the present disclosure, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present disclosure.

[0034] like Figure 1 As shown, the present invention proposes a device for imaging and collecting gas arc schlieren, including a schlieren LED light source 1, a calibration lens 2, a reflector 3, a concave reflector 4, a gas arc nozzle stabilization device 5, an imaging reflector 6, a knife edge 7, an imaging lens 8, a narrowband filter 9, a spatial filter 10, and a high-speed camera 11. The schlieren method collects and analyzes the refractive index information in the parallel-deflected light passing through the gas arc plasma, thereby obtaining the flow field and temperature field information of the target object. Since the arc plasma of the photographed object has strong self-emission light, the present device suppresses and filters the arc self-emission light through narrowband filtering, thereby improving the signal-to-noise ratio of the schlieren signal. At the same time, the optical path of the traditional schlieren system does not have high requirements on the efficiency of light source utilization. Due to the particularity of the observed object, the present system will cause a strong filtering attenuation of the light source. Therefore, the present system needs to make full use of the light source, mainly by correcting the schlieren LED light through the lens group, so that it can pass through the plasma to be measured as efficiently as possible and be efficiently collected by the high-speed camera. At the same time, as Figure 2(a) to Figure 2(b) As shown, the Schlieren LED light is corrected by 2 and 3 and then goes to 4, where it converges into parallel light and then enters the gas arc object in 5. Figure 2(a) to Figure 2(b)As shown, the plasma is located in the elliptical region. Due to the uneven refractive index distribution in the plasma region, the parallel light is deflected differently. The Schlieren light is then focused by the second concave reflector lens. After the Schlieren light beam carrying the deflected light information is reflected by 6 and cut by the knife edge 7, it will produce a Schlieren image with different brightness, which is imaged and filtered by 8, 9, and 10 to produce a high-quality and clear Schlieren signal that is finally collected by the high-speed camera 11. It should be noted that there is no strict requirement for the position and angle of the above components, as long as the above process can be realized.

[0035] In one embodiment, the LED light source is a continuously dimming single-color LED, preferably a continuously dimming single-color LED with a power of 50W.

[0036] In one embodiment, the collimating lens has a diameter of 2 inches, the two concave mirrors have a diameter of 100 mm, a focal length of 1000 mm, and a reflector has a diameter of 50 mm.

[0037] In one embodiment, if Figure 2(a) to Figure 2(b) As shown, the gas nozzle has a pair of through holes as light passages and windows along the direction of the Schlieren light transmission, and the through holes are covered with quartz glass. The gas enters the nozzle through the opening inside the static contact, and then blows the arc downward along the pipeline formed by the nozzle-contact.

[0038] In one embodiment, the knife edge is cut vertically, the narrowband filter is a filter that allows the central wavelength of the light source to be ±3nm, the diameter is 1 inch, and the diameter of the imaging lens is 2 inches.

[0039] The present invention also proposes a method for collecting schlieren signals of a gas arc, comprising the following steps:

[0040] Step 1: The Schlieren LED light is focused by the calibration lens and then goes to the first concave reflector;

[0041] Step 2, adjusting the position and angle of the first concave reflector so that the schlieren light passes through the gas arc plasma in parallel;

[0042] Step 3: Adjust the angle and position of the gas arc nozzle so that the window is located at the center of the Schlieren light spot and faces the direction of the incoming light;

[0043] Step 4: Adjust the second concave reflector so that the received Schlieren parallel light is focused on the knife edge behind the reflector, and adjust the knife edge and imaging lens so that the Schlieren signal enters the high-speed camera.

[0044] Furthermore, the concave mirror, reflector, lens and filter through which the Schlieren LED light passes must all be coaxial.

[0045] like Figure 2(a) to Figure 2(b)As shown, the present invention proposes an arc nozzle and a fixing device for collecting Schlieren signals of gas arcs, including a static contact fixture 12, a PTFE nozzle housing 13, a window glass 14, a moving contact and a fixture 15. The airflow enters through the static contact fixture 12, enters the pipeline formed by the contact and the PTFE nozzle housing along the internal opening of the static contact, and finally blows to the arc burning area, and stabilizes and cools the gas arc. The PTFE nozzle housing 13 has a boundary limiting effect on the flow field, and at the same time realizes fixed assembly of the static contact fixture 12. The window glass 14 facilitates the Schlieren light to pass through the plasma area 16. The moving contact and the fixture 15 are driven by an electromagnetic mechanism to pull and generate an arc.

[0046] The temperature measurement range of the traditional Schlieren method is only 300-1000K, and the resolution is no higher than 100us / frame and 1mm / pixel. It is mostly used for flow field observation of low-temperature gas or cold plasma. The temperature range of the test object targeted by the present invention is 300-30000K, and the resolution can reach up to 10us / frame and 0.1mm / pixel. Therefore, the system has the advantages of high temporal and spatial resolution and a wide temperature range of the observed object, and has a good application effect on the diagnosis of thermal plasma such as gas arc. Figure 3 The schlieren flow field and temperature test results of the gas arc object photographed for the present invention include the arc plasma schlieren results at 0, 1ms, 3ms, and 11ms after the arc, where different colors represent changes in grayscale values. The schlieren image is symmetrically distributed with opposite light and dark, reflecting the axially symmetrical distribution of the arc column, and the lower turbulent structure shows a diffusion effect over time. Figure 4 The temperature test result diagram is shown in Figure 1. The axial distribution of the temperature is obtained by processing the Schlieren results of the axially symmetrical area 1ms after the arc. It can be seen that the test results of the present invention can clearly show the turbulent structure of the flow field and perform temperature testing.

[0047] The above general description of the invention involved in this application and the description of its specific implementation methods should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art can add, reduce or combine the disclosed technical features in the above general description and / or specific implementation methods (including examples) without violating the constituent elements of the invention involved, to form other technical solutions within the scope of protection of this application.

Claims

1. A nozzle-restricted gas arc diagnostic device based on the Schlieren method, characterized in that: The device comprises: a schlieren light source and a concave reflector group, a gas arc nozzle stabilization device, a knife edge and an imaging collection mirror group; The Schlieren light source and concave reflector group includes: an LED light source, a calibration lens, two concave reflectors, and a reflector; The knife edge and imaging collection mirror assembly includes: an imaging reflector, a knife edge, a spatial filter, a narrowband filter, an imaging lens, and a high-speed camera; The collimating lens has a diameter of 2 inches, the two concave mirrors have a diameter of 100 mm, a focal length of 1000 mm, and a reflector has a diameter of 50 mm; The device targets a test object with a temperature range of 300-30000K, and a resolution of 10us / frame and 0.1mm / pixel; the gas arc nozzle stabilization device comprises a gas nozzle, and the gas nozzle has a pair of through holes along the transmission direction of the schlieren light as a light passage and a window; The spatial filter is arranged in front of the lens of the high-speed camera; The gas arc nozzle stabilizing device comprises: a stationary contact and a clamp thereof, a PTFE nozzle shell, a sight glass, a moving contact and a clamp thereof; the airflow enters through the stationary contact and the clamp thereof, enters into a pipe formed by the contact and the PTFE nozzle shell along the internal opening of the stationary contact, and finally blows to the arc burning area, and realizes stabilization and cooling effects on the gas arc; the PTFE nozzle shell has a boundary limiting effect on the flow field, and at the same time realizes fixed assembly of the stationary contact and the clamp thereof; the sight glass facilitates the passage of the schlieren light and passes through the plasma area; the moving contact and the clamp thereof are driven to move by an electromagnetic mechanism, and are used to pull and generate an arc.

2. The nozzle-restricted gas arc diagnostic device based on the Schlieren method according to claim 1, characterized in that: The LED light source is a continuously dimming single-color LED.

3. The nozzle-restricted gas arc diagnostic device based on the Schlieren method according to claim 1, characterized in that: The knife edge is a vertical cut.

4. The nozzle-restricted gas arc diagnostic device based on the Schlieren method according to claim 1, characterized in that: The narrowband filter is a filter that allows the central wavelength of the light source to pass.

5. The nozzle-restricted gas arc diagnostic device based on the Schlieren method according to claim 1, characterized in that: The imaging lens has a diameter of 2 inches.

6. The nozzle-restricted gas arc diagnostic device based on the Schlieren method according to claim 1, characterized in that: The gas nozzle has a pair of through holes along the transmission direction of the Schlieren light.

7. A method for diagnosing nozzle-restricted gas arc based on Schlieren method, characterized in that: The method utilizes a nozzle-restricted gas arc diagnostic device based on the Schlieren method as described in any one of claims 1 to 6; The method comprises the following steps: Step 1: The Schlieren LED light is focused by the calibration lens and then goes to the first concave reflector; Step 2, adjusting the position and angle of the first concave reflector so that the schlieren light passes through the gas arc plasma in parallel; Step 3: Adjust the angle and position of the gas nozzle so that the window is located at the center of the Schlieren light spot and faces the direction of the incoming light; Step 4: Adjust the second concave reflector so that the received Schlieren parallel light is focused on the knife edge behind the reflector, and adjust the knife edge and imaging lens so that the Schlieren signal enters the high-speed camera.

8. The method for diagnosing nozzle-restricted gas arc based on the Schlieren method according to claim 7, characterized in that: The concave reflector, imaging reflector, imaging lens, narrowband filter and spatial filter that the Schlieren LED light passes through must all be coaxial.

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