High-speed continuous flow field impurity particle detection method and detection system

Abstract

The invention relates to a method and a system for detecting impurity particles in a high-speed continuous flow field. The detection method comprises the following steps: injecting pulse laser from one side outside the high-speed continuous flow field along a direction perpendicular to the high-speed continuous flow field; recording a laser scattering signal of the impurity particles at a certain moment in a region irradiated by the pulse laser by using image capturing equipment outside the high-speed continuous flow field, and converting the size of the impurity particles in the irradiated region according to a Mie scattering principle; the detection area is converted according to the imaging field of view and the scanning speed of the image capturing device, the number of impurity particles in the area irradiated by the pulse laser is counted, and the concentration of the corresponding impurity particles is calculated. Particles in a flow field are irradiated by high-energy pulse laser, the relationship between scattered light intensity and particle size is analyzed by utilizing the Mie scattering theory, and statistical measurement of particle size and concentration is realized. And further obtaining the particle size and concentration of impurity particles in the whole high-speed continuous flow field.

Description

Technical Field

[0001] This application relates to the technical field of flow field particle detection, and particularly to a method and a detection system for detecting impurity particles in a high-speed continuous flow field. Background Art

[0002] During the wind tunnel test, impurity particles moving at high speed carry kinetic energy and impact the surface of the model, resulting in an increase in the surface roughness of the model, directly affecting the simulation accuracy of the model in the flow field, causing deviations between the simulation and experimental results, affecting the aerodynamic performance analysis and structural design, and leading to potential safety hazards in the design. Therefore, it is necessary to detect the size of the internal impurity particles and the concentration of impurity particles in the flow field cross-section during the wind tunnel test in real time.

[0003] Currently, the conventional particle image velocimetry instrument used for high-speed flow field measurement can only measure the particle movement speed and the number of particles, and cannot measure the particle size. Moreover, the detection surface of the particle image velocimetry instrument is not perpendicular to the flow field direction, and the particle concentration in the flow field cross-section cannot be obtained. In addition, the detection instrument needs to be placed inside the flow field during detection. However, in the high-speed flow field of the wind tunnel, this instrument will become the second flow guiding structure in the flow field in addition to the model to be detected, damaging the flow field state, thereby reducing the test simulation accuracy. At the same time, the impurity particles in the flow field will also reduce the service life of the detection instrument. Summary of the Invention

[0004] Based on this, it is necessary to provide an online detection method for the size and concentration of impurity particles in a high-speed continuous flow field to realize continuous online monitoring of the cleanliness of the high-speed flow field on the premise of not requiring flow guiding and without causing adverse effects on the flow field structure and the detection instrument.

[0005] A method for detecting impurity particles in a high-speed continuous flow field includes the following steps: Shoot pulsed laser from one side outside the high-speed continuous flow field along the direction perpendicular to the high-speed continuous flow field; Use an image capture device outside the high-speed continuous flow field to record the laser scattering signals of impurity particles at a certain moment in the area irradiated by the pulsed laser, count the number of impurity particles according to the number of laser scattering signals, and further calculate the size of the impurity particles in the irradiated area according to the Mie scattering principle; Calculate the detection area according to the imaging field of view and the scanning speed of the image capture device, count the number of impurity particles in the area irradiated by the pulsed laser, and calculate the corresponding impurity particle concentration.

[0006] As a preference of the method for detecting impurity particles in a high-speed continuous flow field of the present invention, before shooting the pulsed laser, the high-speed continuous flow field should be pre-operated, and the pre-operation time is determined according to the area and wind speed of the high-speed continuous flow field.

[0007] As a preference of the method for detecting impurity particles in a high-speed continuous flow field in the present invention, a laser collection device is provided at a position corresponding to the pulsed laser on the other side outside the high-speed continuous flow field.

[0008] As a preference of the method for detecting impurity particles in a high-speed continuous flow field in the present invention, the optical path of the pulsed laser is perpendicular to the flow direction of the high-speed continuous flow field.

[0009] A detection system for implementing the above method for detecting impurity particles in a high-speed continuous flow field, the detection system includes an observation window and a detection device. The observation window is arranged on the side wall and the top wall of the high-speed continuous flow field chamber. The detection device is arranged around the high-speed continuous flow field chamber and is coplanar with its cross-section. The detection device includes a pulsed laser, an optical trap, and a camera. The pulsed laser and the optical trap are arranged opposite to each other. The output end of the pulsed laser faces the optical trap. The camera is arranged above the pulsed laser and the optical trap, and its imaging lens faces the pulsed laser emitted by the pulsed laser.

[0010] As a preference of the detection system in the present invention, a beam shaper is provided at the output end of the pulsed laser.

[0011] As a preference of the detection system in the present invention, the light source energy of the pulsed laser is not less than 100 millijoules per pulse, and the repetition frequency is not less than 10 hertz.

[0012] As a preference of the detection system in the present invention, the peak quantum efficiency of the imaging chip of the camera is not less than 90%, the field of view of the camera in cooperation with the imaging lens is not less than 100 millimeters, and the depth of field of the lens is not less than 100 millimeters.

[0013] As a preference of the detection system in the present invention, the imaging lens is provided with an antireflection filter, and the antireflection window of the antireflection filter matches the wavelength of the light source of the pulsed laser.

[0014] As a preference of the detection system in the present invention, the repetition frequency of the pulsed laser is synchronized with the camera shutter.

[0015] Advantages of the present invention: In the present invention, high-energy pulsed laser is used to irradiate the particles in the flow field. By using the Mie scattering theory (analyzing the relationship between the scattered light intensity and the particle size), the statistical measurement of the particle size / diameter and the concentration (the number of particles in a certain area of the flow field cross-section) is realized. After the high-speed continuous flow field in the wind tunnel moves for a period of time, the impurity particles in the flow field can be approximately considered to be evenly distributed. Thus, the particle size and concentration of the impurity particles in the entire high-speed continuous flow field can be obtained. The present invention realizes the continuous on-line monitoring of the cleanliness of the high-speed flow field without causing adverse effects on the flow field structure and the detection instrument. Description of the drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic diagram of the steps of the detection method in Embodiment 1 of the present application; Figure 2 It is a schematic diagram of the principle of the detection method in Embodiment 1 of the present application; Figure 3 It is a schematic diagram of the structure of the detection system in Embodiment 2 of the present application; Figure 4 It is a schematic diagram of the structure of the detection system in Embodiment 3 of the present application; Figure 5 It is a schematic diagram of the structure of the detection system in Embodiment 4 of the present application; Figure 6 It is a schematic diagram of the structure of the detection system in Embodiment 5 of the present application; Explanation of reference numerals: 100, observation window; 200, pulsed laser; 300, optical trap; 400, camera; 500, imaging lens; 600, antireflection filter; 700, beam shaper; 800, scanning device; 900, mirror. Detailed implementation manners

[0018] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will give a detailed description of the specific implementation manners of the present application with reference to the drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0019] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present application.

[0020] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0021] In the present application, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0022] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0023] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0024] Embodiment 1 This embodiment provides a method for detecting impurity particles in a high-speed continuous flow field, as Figure 1 shown, including the following steps: After the high-speed continuous flow field has been operating for a period of time, a pulsed laser is emitted from one side outside the high-speed continuous flow field and exits from the other side.

[0025] Use an image capture device outside the high-speed continuous flow field to record the laser scattering signals of impurity particles at a certain moment in the area irradiated by the pulsed laser, count the number of impurity particles according to the number of laser scattering signals, and further calculate the size of the impurity particles in the irradiated area according to the Mie scattering principle.

[0026] Calculate the detection area according to the imaging field of view and scanning speed of the image capture device, and combine it with the number of impurity particles to calculate the impurity particle concentration.

[0027] In this embodiment, before the pulsed laser is emitted, the high-speed continuous flow field should be operated in advance. The advance operation time is determined according to the area and wind speed of the high-speed continuous flow field. The purpose of the advance operation of the high-speed continuous flow field is to make the impurity particles in the flow field approximately evenly distributed.

[0028] In this embodiment, in order to collect excess laser signals, reduce stray light interference in the flow field, and improve the signal contrast of imaging, a laser collection device is provided at a position corresponding to the pulsed laser on the other side outside the high-speed continuous flow field.

[0029] In this embodiment, the optical path of the pulsed laser is perpendicular to the flow direction of the high-speed continuous flow field. The pulsed laser, the laser collection device, and the image capture device are arranged in a triangle and are located in the cross-section of the high-speed continuous flow field.

[0030] The principle of the detection method is as Figure 2As shown, the pulsed laser is incident perpendicular to the direction of the high-speed continuous flow field and coplanar with the cross-section of the high-speed continuous flow field. The pulsed laser hits the impurity particles moving in the high-speed continuous flow field, generating Mie scattering. The image capture device records the laser scattering signal at a certain moment of the flow field. According to the Mie scattering principle, analyzing the intensity of the scattering signal can convert the particle size, counting the number of particles based on the number of scattering signals in the imaging, and calculating the detection area according to the imaging field of view and scanning speed of the image capture device, and then calculating the particle concentration in the high-speed continuous flow field.

[0031] As Figure 2 shown, the vertical double arrow represents the depth of field of the lens, the horizontal double arrow represents the detection area of the camera 400, that is, the area through which the impurity particles pass, the dashed arrow represents the direction of the high-speed continuous flow field, the dashed square represents the cross-section of the high-speed continuous flow field, the light-colored arrow represents the laser beam emitted by the pulsed laser 200, and the dark area in the light-colored arrow is the detection area.

[0032] Embodiment 2 This embodiment provides a detection system for implementing the detection method in Embodiment 1. The detection system includes an observation window 100 and a detection device. The observation window 100 is arranged on the side wall and the top wall of the high-speed continuous flow field chamber. The detection device is arranged around the high-speed continuous flow field chamber and coplanar with its cross-section. The output end of the detection device faces the high-speed continuous flow field through the observation window 100. The detection device includes a pulsed laser 200, an optical trap 300, and a camera 400. The pulsed laser 200 and the optical trap 300 are arranged opposite to each other. The output end of the pulsed laser 200 faces the optical trap 300. The camera 400 is arranged above the pulsed laser 200 and the optical trap 300, and its imaging lens 500 faces the pulsed laser emitted by the pulsed laser 200.

[0033] In this embodiment, the light source energy of the pulsed laser 200 is not less than 100 millijoules per pulse, and the repetition frequency is not less than 10 Hz, which is used to ensure that particles with a minimum size of 1um generate sufficient intensity of light scattering signals and enable the detection system to have a certain efficiency for real-time detection.

[0034] In this embodiment, the peak quantum efficiency of the imaging chip of the camera 400 is not less than 90%, which is used to ensure that extremely weak light scattering signals can be detected.

[0035] In this embodiment, the field of view of the camera 400 in cooperation with the imaging lens 500 is not less than 100 mm, and the depth of field of the lens is not less than 100 mm, and the detection system has a sufficiently large detection area. The impurity particles in the flow field can be approximately considered to be evenly distributed, and the statistical results of a larger area can more accurately represent the particle concentration of the entire cross-section of the flow field.

[0036] In this embodiment, an anti-reflection filter 600 is provided on the imaging lens 500. The anti-reflection window of the anti-reflection filter 600 matches the wavelength of the light source of the pulsed laser 200, which is used to reduce the ambient light entering the camera, improve the signal-to-noise ratio, and reduce the influence of stray light on the camera 400.

[0037] In this embodiment, the repetition frequency of the pulsed laser 200 is synchronized with the shutter of the camera 400, which improves the acquisition efficiency of the effective signal and suppresses the interference of the ambient background light.

[0038] As Figure 3 shown: The observation window 100 includes multiple groups, which are arranged at intervals along the direction of the high-speed continuous flow field. Multiple observation windows 100 within each group are located in the same cross-section. Each group includes a pair of observation windows 100 located on the opposite side walls of the high-speed continuous flow field chamber and an observation window 100 located at the top of the high-speed continuous flow field chamber. An optical trap 300 is arranged outside the opposite observation windows 100 to absorb the excess laser light. The above structure can minimize the interference of the reflected light in the field when the detection device is working.

[0039] A beam shaper 700 is provided at the output end of the pulsed laser 200. It expands the linear beam emitted by the pulsed laser 200, increases the beam diameter to obtain a relatively larger monitoring area. The expanded beam penetrates the observation window 100 and enters the experimental section in the high-speed continuous flow field, is coplanar with the cross-section of the high-speed continuous flow field, and passes through the observation window 100 on the other side and enters the optical trap 300. The camera 400 and the imaging lens 500 are installed on the top observation window 100 perpendicular to the flow field direction and perpendicular to the laser direction, and detect the light scattering signal generated by the impurity particles moving in the high-speed continuous flow field when the laser beam in the detection cross-section hits them. The area formed by the field of view and the lens depth of field of the camera 400 cooperating with the imaging lens 500 covers the detection area.

[0040] Embodiment 3 The difference between this embodiment and Embodiment 2 is that instead of using a beam shaper 700 to expand the linear beam emitted by the pulsed laser 200, a scanning device 800 is used. The scanning device 800 is equipped with a reflecting mirror 900 arranged at 45 degrees. The scanning device 800 can be translated vertically to keep the laser beam always horizontal and always perpendicular to the direction of the high-speed continuous flow field. Its moving range is smaller than the size of the observation window 100, and the laser beam emitted by the pulsed laser 200 is reflected by the reflecting mirror 900 and enters the high-speed continuous flow field.

[0041] As Figure 4As shown, during detection, the scanning device 800 moves to form multiple optical paths. The multiple optical paths and the camera 400 are combined to form a detection area. Each laser scattering signal within this area does not come from the same moment, but the impurity particles in the high-speed continuous flow field can be considered to be evenly distributed. Therefore, it can still be regarded as a statistical detection of the impurity particles in the cross-section of the high-speed continuous flow field. By measuring multiple times for a certain period, the statistical results can be obtained, and then the size and concentration of the impurity particles in the high-speed continuous flow field can be statistically measured.

[0042] Embodiment 4 The difference between this embodiment and Embodiment 3 is that: as Figure 5 shown, the scanning device 800 is a galvanometer, and the galvanometer can swing quickly at a small angle to deflect the laser angle to achieve scanning.

[0043] Embodiment 5 The difference between this embodiment and Embodiment 2 is that: the beam shaper 700 expands and shapes the laser beam into a sheet without the scanning device 800. The laser beam is expanded and shaped into a sheet beam, and the divergence angle of the sheet beam is controlled so that the size at the far end is smaller than the size of the observation window 100. Limited by the sheet beam shaping method, the area with a thin sheet light thickness is taken as the detection area.

[0044] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0045] The above-described embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for detecting impurity particles in a high-speed continuous flow field, characterized in that, The steps include the following: Inject the pulsed laser from one side outside the high-speed continuous flow field along the direction perpendicular to the high-speed continuous flow field; Use an image capture device outside the high-speed continuous flow field to record the laser scattering signals of impurity particles at a certain moment in the area irradiated by the pulsed laser, count the number of impurity particles according to the number of laser scattering signals, and further calculate the size of impurity particles in the irradiated area according to the Mie scattering principle; Convert the detection area according to the imaging field of view and scanning speed of the image capture device, count the number of impurity particles in the area irradiated by the pulsed laser, and calculate the corresponding impurity particle concentration.

2. The high-speed continuous flow field impurity particle detection method according to claim 1, wherein Before injecting the pulsed laser, the high-speed continuous flow field should be operated in advance, and the advance operation time is determined according to the area and wind speed of the high-speed continuous flow field.

3. The high-speed continuous flow field impurity particle detection method according to claim 1, characterized in that, A laser collection device is provided at the position corresponding to the pulsed laser on the other side outside the high-speed continuous flow field.

4. A detection system for implementing the high-speed continuous flow field impurity particle detection method according to any one of claims 1-3, characterized in that: The detection system includes an observation window and detection equipment. The observation window is arranged on the side wall and the top wall of the high-speed continuous flow field chamber. The detection equipment is arranged around the high-speed continuous flow field chamber and is coplanar with its cross-section. The detection equipment includes a pulsed laser, an optical trap and a camera. The pulsed laser and the optical trap are arranged oppositely. The output end of the pulsed laser faces the optical trap. The camera is arranged above the pulsed laser and the optical trap, and its imaging lens faces the pulsed laser emitted by the pulsed laser.

5. The detection system according to claim 4, characterized in that, A beam shaper is provided at the output end of the pulsed laser.

6. The detection system according to claim 5, wherein The light source energy of the pulsed laser is not less than 100 millijoules per pulse, and the repetition frequency is not less than 10 hertz.

7. The detection system according to claim 4, wherein The peak quantum efficiency of the imaging chip of the camera is not less than 90%.

8. The detection system according to claim 7, wherein The field of view of the camera in cooperation with the imaging lens is not less than 100 millimeters, and the depth of field of the lens is not less than 100 millimeters.

9. The detection system according to claim 8, characterized in that, The imaging lens is provided with an anti-reflection filter, and the anti-reflection window of the anti-reflection filter matches the wavelength of the light source of the pulsed laser.

10. The detection system according to claim 4, wherein The repetition frequency of the pulsed laser is synchronized with the camera shutter.

Images