Cloud particle acquisition probe based on interference particle imaging

Abstract

The invention discloses a cloud and mist particle acquisition probe based on interference particle imaging, and the probe comprises a sheet-shaped laser emission unit which is used for emitting sheet-shaped pulse laser beams, expanding the laser beams, adjusting the incident position and the incident angle, and irradiating cloud and mist particles to generate scattered light signals; the scattered light signal acquisition unit is used for collecting scattered light signals and recording the scattered light signals on the camera; the mechanical unit comprises a first measuring arm used for installing the sheet-shaped laser unit and a second measuring arm used for installing the scattered light signal acquisition unit, and the first measuring arm and the second measuring arm are connected through a connecting section and are installed on the base; and the signal processing system is used for processing the scattered light interference signal recorded by the camera to obtain cloud and mist particle parameters. The acquisition probe provided by the invention ensures stable operation of a photoelectric system in a low-temperature complex and severe cloud environment, improves the accuracy of interference particle imaging measurement, and realizes real-time measurement of cloud particle parameters suitable for different industrial scenes.

Description

Technical Field

[0001] The invention belongs to the field of gas-liquid two-phase flow measurement, and in particular relates to a cloud and fog particle collection probe based on interference particle imaging. Background Art

[0002] A comprehensive analysis of aircraft accidents in recent years shows that most of them are caused by icing in aircraft engines and other parts, which causes engine stall, surge, rotation and other phenomena, resulting in aircraft loss of control. This further highlights the extreme need for timeliness and accuracy of cloud field measurements. By simulating the low temperature and high humidity environment of clouds and fog, cloud field tests can more accurately understand the dynamic characteristics of heat and mass transfer of cloud particles and their specific impact on flight performance. Therefore, in order to calibrate and calibrate cloud field tests, the development of cloud particle measuring instruments is crucial and of key significance. Cloud particle measuring instruments can provide information such as the size, distribution, velocity, and temperature of cloud field particles. By accurately monitoring the above parameters, the cloud field state under icing conditions can be effectively simulated and predicted, thereby conducting targeted icing tests on aircraft and engines to improve their efficiency and safety under extreme weather conditions.

[0003] Optical measurement technology can realize online non-contact measurement of droplets, and can also provide accurate parameters such as particle size and distribution. It is gradually being widely used in the testing of icing fog fields. For example, microscopic imaging technology is used to measure parameters such as particle morphology and particle size, holographic imaging technology is used to measure parameters such as particle size distribution, median volume diameter and liquid water content, and rainbow refraction technology is used to measure parameters such as particle temperature, evaporation rate and particle size. For example, the Chinese patent with publication number CNCN117990568A discloses an integrated measurement device for backscattering imaging of fog particles, which includes: a backscattering imaging photoelectric system, which emits a laser beam through a laser, collimates and irradiates fog particles, and the generated scattering signal is collected and recorded on the camera by a Fourier optical imaging system; a probe system, including a head, a transition section, an intermediate section and a tail, is used to install and fix the backscattering imaging photoelectric system; the patent has the characteristics of real-time non-contact measurement of multiple parameters of fog particles (fog particle size, distribution, refractive index, temperature, etc.).

[0004] After the droplets are interfered by the scattered light generated by laser irradiation, a stable stripe structure will be formed. These structures carry information such as particle size and distribution. The interference particle imaging technology is to invert the particle size according to the frequency of the stripes, and then realize the real-time online measurement of cloud and fog particle median volume diameter, liquid water content and other parameters. The particle size measurement range of the interference particle imaging technology changes with the layout of the optical path system, and can generally reach 20 to 500 μm, which can reach the same level as the aforementioned technology. In addition, the effects of the existing technologies in phase state recognition are not very ideal, while the interference particle imaging technology can accurately identify the speckle signal of ice crystals, thereby realizing the phase state recognition of the ice-water mixed phase particle field. Through further analysis of the speckle signal, the particle size, morphology and other information of the ice crystal can also be obtained, which is a major advantage over other measurement technologies. Therefore, the optical measurement technology based on particle interference particle interference imaging is urgently needed to be applied in cloud and fog field testing to improve the accuracy and diversity of cloud and fog particle testing.

[0005] Since the conditions for the implementation of optical technology are relatively harsh, such as the need to fix photoelectric elements in a precise spatial position relationship, maintain a constant temperature and humidity working environment, reduce the interference of stray light such as reflected light, etc., in order to apply interferometric particle imaging technology in icy cloud fields, the collection probe is required to have an integrated and optimized optical path system and a compact mechanical unit. Summary of the invention

[0006] The object of the present invention is to provide a cloud and fog particle collection probe based on interferometric particle imaging, which can realize real-time measurement of the dynamic characteristics of multiphase flow particles in a cloud and fog field in a low-temperature, complex and harsh cloud and fog environment.

[0007] The technical solution adopted by the present invention is:

[0008] A cloud and fog particle collection probe based on interferometric particle imaging, the probe comprising:

[0009] The sheet laser emitting unit is used to emit a sheet pulse laser beam, expand the beam, adjust the incident position and the incident angle, and generate a scattered light signal after irradiating the cloud particles;

[0010] A scattered light signal acquisition unit, used for collecting scattered light signals and recording them on a camera;

[0011] The mechanical unit comprises a first measuring arm for mounting the sheet laser unit and a second measuring arm for mounting the scattered light signal acquisition unit, wherein the first measuring arm and the second measuring arm are connected via a connecting section and mounted on a base;

[0012] The signal processing system is used to process the scattered light interference signal recorded by the camera to obtain the cloud particle parameters.

[0013] The sheet laser emitting unit comprises a pulse laser, a plano-concave cylindrical lens, a plano-convex cylindrical lens and a laser reflecting mirror. The pulse laser beam generated by the pulse laser is expanded by the plano-concave cylindrical lens and adjusted by the plano-convex cylindrical lens to form a parallel and uniform sheet pulse laser, which is then changed in direction by the laser reflecting mirror to irradiate the cloud particles.

[0014] Furthermore, in the sheet-shaped laser emitting unit provided by the present invention: a pulse laser is used to generate a stable pulse laser beam with adjustable light intensity, frequency and delay, which forms a sheet-shaped pulse laser beam after passing through a collimation system.

[0015] The scattered light signal collection unit comprises a signal reflector, a collection lens and a camera. The signal reflector and the collection lens cooperate to collect the scattered light signal and then record it on the camera.

[0016] The camera is located at the defocusing position of the collection lens in the scattered light signal collection unit.

[0017] Among them, the camera and the pulse laser are synchronously triggered by a signal generator to ensure the synchronous operation of the sheet laser emitting unit and the scattered light signal collection unit.

[0018] The main optical axis of the sheet-shaped laser emitting unit and the main optical axis of the scattered light signal collecting unit are located on the same horizontal plane and have an included angle of 45° to 90°.

[0019] Furthermore, the scattered light signal collection unit provided by the present invention collects scattered signals in the measurement area through a signal reflector and a collection lens, the measurement area is located in the middle of the instrument, effectively avoiding interference from stray light, and records the signal through a camera; wherein, the optical elements of the sheet laser emitting unit and the scattered light signal collection unit are directly fixed inside the collection probe, and the relative positions can be fine-tuned; the laser emission direction and the signal collection direction are located in the same horizontal plane, and the angle is between 45° and 90°.

[0020] Furthermore, the sheet laser emission unit and the scattered light signal collection unit operate synchronously and are controlled by a signal generator to transmit signals with a certain delay to the pulse laser and the camera respectively, thereby ensuring that the emission frequency of the sheet pulse laser and the collection frequency of the camera remain consistent.

[0021] The first measuring arm and the second measuring arm each include a head, a middle portion and a tail portion, the head portion is wedge-shaped, the cross-section of the middle portion is circular, and the tail portion is conical; the middle portion of the first measuring arm and the middle portion of the second measuring arm are connected by a connecting section to form a symmetrical structure; an electric heating anti-icing device is provided inside the first measuring arm, the second measuring arm and the connecting section.

[0022] Specifically, the heads of the first measuring arm and the second measuring arm are both provided with electric heating anti-icing devices, and the inside of the probe is provided with an electric heating control element for controlling the electric heating anti-icing devices.

[0023] The head of the first measuring arm is provided with a laser emitting window, and the head of the second measuring arm is provided with a signal collecting window. Both the laser emitting window and the signal collecting window are provided with symmetrical boss structures, drainage grooves and wedge structures.

[0024] The laser beam irradiates the cloud particles after passing through the laser emission window, and the interference signal is recorded on the camera by the imaging lens through the signal collection window. Symmetrical boss structures are designed at the two windows, extending outward from the surface of the measuring arm to reduce the windward area at the window; drainage grooves and wedge structures are designed in front of the window to reduce the influence of large-area heat dissipation of the measuring arm head on the window temperature, making it easier to control the window temperature and prevent contamination and icing.

[0025] The walls of the laser emission window and the signal collection window are both provided with electric heating anti-icing devices.

[0026] The front edge of the base is an arc, and the base is connected to the connecting section through a sealing groove.

[0027] The first measuring arm, the second measuring arm, the connecting section and the base have a smooth transition. The interface at the bottom of the base can be customized according to the fixing method at the experimental site.

[0028] The mechanical unit provided by the present invention can protect the photoelectric elements inside the acquisition probe and control the external flow field. The optical path system can be fixed inside, the aerodynamic shape is good, the interface at the lower end of the base can be customized, and it can be directly fixed on the platform for high-speed testing. The middle section connects the measuring arms on both sides, and the connection with the cylindrical structures on both sides has a smooth transition without obvious protrusions or depressions. The windward surface is designed to be pointed to reduce the possibility of icing. The front edge of the base is an arc, which directly connects the middle section and the test bench. The lower end interface can be customized, and its external shape has little effect on the original flow field and hardly changes the multiphase flow characteristics. In addition, the measurement area is located below the middle area of ​​the instrument, avoiding the influence area of ​​the mechanical structure of the measuring arms on both sides. The smooth connection and transition of the various parts of the mechanical unit can reduce the possibility of icing, contamination and the like.

[0029] In the present invention, the special structures of the head and tail of the windward side of the measuring arm can effectively reduce the influence of the external flow field on the collection probe, and improve the stability and anti-interference of the collection probe.

[0030] The probe also includes an electric control unit, including a power supply and the above-mentioned signal generator and electric heating anti-icing device, which is used to power the camera and the laser and control the signal synchronization between the camera and the pulse laser, and control the window temperature to prevent contamination and icing. The electric heating anti-icing device is adjusted by a temperature control instrument, and the temperature control instrument controls the solid-state relay according to the temperature measured by the thermocouple, thereby controlling the connection and disconnection of the electric heating anti-icing device.

[0031] Furthermore, seals are added to the joints of the various parts of the mechanical unit, the laser emission window and the signal collection window, as well as the base and the connection section, so that the sealing level of the collection probe reaches IP65.

[0032] The mechanical unit provided by the present invention prevents the internal components from being affected by the low-temperature, high-speed and humid environment through sealing, mechanical anti-icing, electric heating anti-icing device and other protection methods, ensuring the normal operation of the optical system in a complex and harsh environment (ensuring the stable operation of the optoelectronic system). The electric heating anti-icing device is located at the head of the measuring arm, the window and the front end, the front end of the connecting section, the laser and other electrical components, with a total heating power of more than 500W, ensuring that when the collection probe is running in a foggy environment of -40°C, the icing phenomenon on the surface of the collection probe will not affect the accuracy of particle measurement.

[0033] The method for the signal processing system to process the scattered light interference signal recorded by the camera to obtain the cloud and fog particle parameters is:

[0034] When the scattered light interference signal is the interference fringe signal of the droplet, the particle size of the cloud particle droplet is obtained by inverting the fringe image;

[0035] When the scattered light interference signal is the speckle signal of ice crystals, the particle size of ice crystals of cloud particles can be obtained by inverting the speckle image;

[0036] The cloud particle parameters are output according to the droplet size and ice crystal size, including particle phase change (particle phase identification), particle size distribution, uniformity (median volume diameter) and liquid water content.

[0037] The cloud and fog particle collection probe based on interference particle imaging provided by the present invention operates stably at a wind speed of 200 m / s.

[0038] Compared with the prior art, the present invention has the following excellent effects:

[0039] Aiming at low-temperature, complex and humid icy cloud and fog fields, the present invention provides a cloud and fog particle collection probe based on interference particle imaging: the probe adopts an optical-mechanical-electrical-thermal integrated design to detect the dynamic characteristics of multiphase flow particles in the cloud and fog field in real time, and is mainly used to analyze parameters such as particle phase change, particle size distribution, uniformity and liquid water content; in terms of optical path structure, the angles of the laser emitting surface and the signal receiving surface are selected according to the Debye series expansion model of the Mie scattering theory, so as to obtain an interference fringe signal with better contrast, thereby improving the signal quality and increasing the amount of effective data; the special structure of the head and the window, combined with the electric heating anti-icing system, can greatly reduce the possibility of icing, and ensure that the measurement area is basically not affected by the mechanical structure of the collection probe.

[0040] The acquisition probe provided by the present invention is a collection probe that can measure multi-parameters of multiphase flow particles in complex and harsh cloud and fog fields. It overcomes the difficulty that optical measurement technology is difficult to apply in the harsh environment of cloud and fog fields, and realizes real-time detection of cloud and fog particles by an interference particle measurement system. It has the characteristics of high integration, strong anti-interference, and suitability for industrial online applications. It can not only measure the changes in multiphase flow particle parameters in real time, but also measure the particle characteristics in different areas of the cloud and fog field by moving the position of the overall acquisition probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 An overall schematic diagram of a cloud and fog particle collection probe based on interferometric particle imaging provided by the present invention;

[0042] Figure 2 A schematic diagram of the internal structure of the cloud and fog particle collection probe provided by the present invention;

[0043] Figure 3 A schematic diagram of the connection section and base of the cloud and fog particle collection probe provided by the present invention;

[0044] Figure 4 Schematic diagram of the interference particle imaging optical path in the embodiment;

[0045] Figure 5 In the embodiment, the interference fringe signal of water droplets captured in the mixed phase wind tunnel test is processed in the frequency domain to obtain the corresponding particle size of the water droplets;

[0046] Figure 6 The speckle signals of different ice crystals measured in a wind tunnel and the corresponding spectrum images after two-dimensional Fourier transformation are shown in the embodiment;

[0047] Among them, 1-first measuring arm; 2-second measuring arm; 3-connecting section; 4-tail; 5-laser emission window; 6-photoelectric control system; 7-sheet laser emission unit; 8-scattered light signal acquisition unit; 9-head of the first measuring arm; 10-signal collection window; 11-electric heating anti-icing device; 12-mechanical sealing device; 13-base; 14-cable area; 15-pulse laser; 16-plano-concave cylindrical lens; 17-plano-convex cylindrical lens; 18-laser reflector; 19-signal reflector; 20-collection lens; 21-camera; 22-sheet pulse laser; 23-scattered light interference signal. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment. It should be noted that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] like Figure 1-Figure 4 As shown, the cloud and fog particle collection probe based on the interference particle imaging technology provided by the present invention includes a sheet laser emission unit 7, a scattered light signal collection unit 8, a mechanical unit, an electric control unit and a signal processing unit, specifically:

[0050] The sheet laser emitting unit 7 generates a pulsed laser beam through a pulsed laser 15, which is expanded by a plano-concave cylindrical lens 16 and adjusted by a plano-convex cylindrical lens 17 to form a parallel and uniform sheet pulsed laser 22. The laser reflector 18 changes the direction of the sheet pulsed laser 22 and then irradiates the cloud particles to generate a scattered light interference signal 23. The interference signal near the scattering angle of 66° is collected by the signal reflector 19 and the collection lens 20, and is imaged on the camera 21.

[0051] The sheet laser emitting unit 7 includes a pulse laser 15, a plano-concave cylindrical lens 16, a plano-convex cylindrical lens 17, and a laser reflector 18, which are used to generate a sheet pulse laser beam 22 with adjustable frequency and intensity. The sheet light beam has uniform light intensity and is emitted in parallel. The laser reflector 18 is used to adjust the incident position and incident angle of the light beam so that the scattered light interference signal 23 generated by the cloud particles passing through the measurement area can be collected by the scattered light signal collection unit 8.

[0052] The sheet laser emitting unit 7 further includes a photoelectric control system 6 .

[0053] Among them, the pulse laser 15 is a pulse laser with adjustable light intensity from 0 to 5mJ and adjustable frequency from 0 to 10Hz, and can select internal triggering or external triggering mode. The pulse laser 15, plano-concave cylindrical lens 16, plano-convex cylindrical lens 17, and laser reflector 18 are all directly fixed inside the mechanical unit.

[0054] The focal length of the plano-concave cylindrical lens 16 is -6 mm, and the size is 6×8 mm, the focal length of the plano-convex cylindrical lens 17 is 40 mm, and the size is 10×12 mm. The size of the acquisition lens 20 is 25 mm, and the focal length is 50 mm.

[0055] The scattered light signal collection unit 8 mainly collects the scattered light interference signal through the collection lens 20 and directly records it on the camera 21. By using the signal reflector 19, the layout of the imaging unit is changed, which is more suitable for cloud and fog field measurement. The camera 21 is located at the defocus point of the collection lens 20.

[0056] The resolution of the camera 21 is between 2M and 20M, and the maximum frame rate is 50fps. The resolution of the camera 21 is 2048×2048px, a total of 5MP. The total length of the imaging unit is within 200mm.

[0057] The mechanical unit is used to protect the internal photoelectric components and control the changes of the external flow field, and includes a first measuring arm 1 (laser side measuring arm), a second measuring arm 2 (camera side measuring arm), a connecting section 3, a tail 4, and a base 13; the head 9 of the first measuring arm 1 and the head of the second measuring arm 2 are both wedge-shaped, and the cross-section is the original shape as a whole, and the tail 4 is conical.

[0058] Specifically, the mechanical unit has no gaps in the windward area and is formed by one-piece processing. The material is aviation hard aluminum 7075, and the windward structure is a wedge-shaped head to reduce the impact of droplet impact on the measurement area. The surface of the collection probe is smooth, without obvious bends or protrusions, and the transition between the first measuring arm 1, the second measuring arm 2 and the connecting section 3 is smooth to reduce surface icing.

[0059] Specifically, a laser emission window 5 and a signal collection window 10 are respectively provided on the first measuring arm 1 and the second measuring arm 2. The sheet pulse laser 22 irradiates the cloud particles after passing through the laser emission window 5, and the scattered light interference signal 23 is collected by the imaging system through the signal collection window 10 and recorded on the camera 21; the laser emission window 5 and the signal collection window 10 are both designed as bosses, and a boss structure is formed on the metal wall surface of the first measuring arm 1 and the second measuring arm 2. A wedge structure and a drainage groove are provided at the front end of the window, and the optical glass is made of sapphire.

[0060] Specifically, the acquisition probe also includes a base 13, the front edge of which is an arc; the base 13 is connected to the connection section of the mechanical unit through the sealing groove at the probe connection and the mechanical sealing device 12 (base sealing groove). A space cable area 14 is reserved inside the base 13 for the power line, control line, and data line to pass through. The interface of the base 13 can be designed and replaced according to the application scenario to adapt to more complex and special industrial devices.

[0061] The electric control unit includes a power supply, a signal generator and an electric heating anti-icing device 11.

[0062] Among them, the signal generator controls the laser emission unit and the imaging unit to run synchronously. The signal generator can generate two square wave signals with exactly the same frequency and amplitude, maintain a specific delay time, ensure that the laser emission frequency of the pulse laser 15 and the acquisition frequency of the camera 21 are completely consistent, and reduce the interference of stray light.

[0063] Among them, the head 9 of the first measuring arm 1 and the head of the second measuring arm 2 are provided with an electric heating anti-icing device 11, and the laser emission window 5 and the signal collection window 10 are also provided with an electric heating anti-icing device 11; an electric heating control element for controlling the electric heating anti-icing device 11 is provided inside the probe.

[0064] Signal processing system: The scattered light interference signal recorded by the camera is transmitted to the computer for storage. After inversion processing by the signal processing system, cloud and fog particle parameters such as phase state, droplet size, particle distribution, and ice crystal size can be identified:

[0065] The interference fringe signal of the droplets is used to invert the fringe image to obtain the particle size of the cloud and fog particle droplets;

[0066] The speckle signal of ice crystals is used to invert the speckle image to obtain the particle size of ice crystals in cloud and fog particles;

[0067] The cloud particle measurement results are output based on the particle size information of droplets and ice crystals, including particle phase changes, particle size distribution, uniformity and liquid water content.

[0068] The cloud and fog particle collection probe based on interference particle imaging technology provided by the present invention integrates the optical path structure of the sheet laser system and the scattered light collection and transmission optical system, ensures the normal operation of the sheet laser emission unit 7 and the scattered light signal collection unit 8, and reduces the optical path length by increasing the reflector, optimizing the focal length of the lens, etc. According to the layout and volume design of the optical path system of the interference particle interference imaging technology, the sheet laser emission unit and the scattered light signal collection unit are respectively integrated in the laser side measurement arm (first measurement arm 1) and the camera side measurement arm (second measurement arm 2), and the sheet laser emission unit 7 and the scattered light signal collection unit 8 are directly fixed in the test area. The mechanical unit is compact and firm, and has good aerodynamic performance. While reducing the impact on the original flow field, the stability of the collection probe in a high wind speed environment is improved. A convex structure is provided at the laser emission window 5 and the signal collection window 10, which cooperates with the wedge-shaped head and drainage groove at the front end to reduce the window contamination phenomenon. The probe body is directly connected to the base 13 to improve the stability and anti-interference of the collection probe.

[0069] The mechanical unit contains a large number of optoelectronic components, such as the sheet laser emission unit 7 and the scattered light signal acquisition unit 8. To ensure the normal operation of the optoelectronic components in the harsh environment of low temperature, high speed and humidity, the mechanical unit includes sealing protection, mechanical structure anti-icing, electric heating anti-icing and transportation protection devices:

[0070] (1) Sealing protection: Sealing protection uses sealing rings and sealing grooves of corresponding specifications, such as the optical window fixing, measuring arm and connecting section, base connection, etc.; protects the connection between various parts of the instrument and other areas that are not integrally processed, and the sealing level is IP65;

[0071] (2) Mechanical structure anti-icing: The aerodynamic shape of the mechanical unit has little effect on the multiphase flow field. The windward surface of the measuring arm is a wedge-shaped structure, and the laser emission window 5 and the tail 4 are conical. These mechanical structures are beneficial to improving the accuracy of system measurement and the stability of the acquisition probe operation.

[0072] (3) Electric heating anti-icing / temperature protection: By installing electric heating anti-icing devices 11 on the head and window, the surrounding environment of the photoelectric element is maintained at a constant temperature, dry and stable. Specifically, electric heating anti-icing refers to the use of temperature control instruments to adjust. The instrument controls the solid-state relay according to the temperature measured by the thermocouple, and then controls the connection and disconnection of the electric heating anti-icing devices 11 on the head and window, so as to achieve temperature protection of the head, laser emission window 5 and signal collection window 10. In addition, it also stabilizes the temperature of the internal connection section and near the laser. The temperature of the heating area controlled by temperature protection can be maintained near the preset value, and remote monitoring can be achieved.

[0073] (4) Transportation protection: The equipment is protected by an aviation box. The filling material is designed according to the shape of the acquisition probe and the power control system, so that the shape of the filling material fits the equipment as closely as possible to avoid damage during transportation.

[0074] The mechanical unit provided by the present invention has been verified through cloud and fog field simulation, and its influence on the flow field is less than 10%.

[0075] The method for using the cloud and fog particle collection probe based on the interference particle imaging technology provided by the present invention comprises the following steps:

[0076] a. Fix the cloud and fog particle collection probe based on interferometric particle interference imaging in the test section of the cloud and fog field, connect the communication line and power line to the power control system, turn on the laser, signal generator, and camera power switches after connecting the power supply, and connect to the computer through the network cable for remote control.

[0077] b. Remotely control and adjust the laser intensity and frequency, the amplitude, frequency and delay of the signal generated by the signal generator, the camera exposure time and trigger mode; turn on the temperature control system and check whether it is operating normally.

[0078] c. Use a spray bottle to generate droplets in the measurement area to check whether the optical path inside the acquisition probe is operating normally.

[0079] d. Turn on the heating switch and let the temperature of the key area be controlled by the temperature control system. Then carry out the cloud field measurement test. According to the test conditions, adjust the synchronization frequency of the laser and camera, laser intensity, camera exposure time and other parameters, record the scattered light signal and store it in the computer.

[0080] Example

[0081] The cloud and fog particle collection probe based on Interference Particle Imaging (IPI) provided in this embodiment specifically includes:

[0082] like Figure 4As shown, the interference particle imaging system includes a 1mJ 532nm pulse laser 15, a plano-concave cylindrical lens 16, a plano-convex cylindrical lens 17, a laser reflector 18, a signal reflector 19, a collection lens 20, a 532nm narrow-band filter, and an industrial area array camera 21 with a network cable interface. The maximum frequency of the pulse laser 15 is 10Hz, and the laser reflector 18 and the signal reflector 19 are covered with a metal film. The pulse laser 15 and the camera 21 are both in external trigger mode. With the help of preliminary experiments, the delay time of the triggering of the pulse laser 15 and the camera 21 is determined to be 250ms. Two square wave signals with a frequency of 10Hz, the same amplitude, and a delay of 250ms are generated by a signal generator to control the synchronous operation of the laser emission unit and the signal collection unit to reduce the interference of ambient stray light and reflected light. The focal lengths of the plano-concave cylindrical lens 16 and the plano-convex cylindrical lens 17 are -6.35 mm and 40 mm respectively. The width of the sheet pulse laser beam generated by the lens is 10 mm. After passing through the laser reflector 18, it irradiates the cloud particles. The angle and position of the imaging unit are adjusted to ensure that the main optical axis of the imaging unit and the main optical axis of the laser emitting unit are at an angle of 66°. The acquisition lens 20 collects the IPI signal of the cloud particles, generates a defocused image and records it on the camera 21, further adjusts the front and rear axial position of the camera 21, and selects a suitable magnification to produce a clear IPI image.

[0083] Mechanical units such as Figure 1-Figure 3 As shown, the mechanical unit of the acquisition probe is designed according to the integrated interference particle imaging system, with a total size of 632mm×330mm×178mm, the diameters of the laser emission window 5 and the signal collection window 10 are both 12.5mm, the head 9 of the first measuring arm and the head of the second measuring arm are wedge-shaped, and the slope angles are 45° and 80°, which effectively reduce the impact of droplet impact on the measurement. The surface of the acquisition probe is smooth, without obvious bends or protrusions. The aerodynamic shape of the mechanical unit of the acquisition probe has been verified by simulation to have an impact on the original flow field of less than 10%. The base 13 of the acquisition probe has a customizable interface, and the fixed interface can be designed and replaced according to requirements, which can be adapted to the installation methods in different industrial environments. A cable area 14 for power supply wiring and communication wiring is reserved, which is directly connected to the power control system.

[0084] The protection system of the mechanical unit mainly designs sealing grooves 12 at the laser emission window 5 and the signal collection window 10, the probe connection, and the connection with the base, and uses a 2.5mm sealing ring to protect the internal parts of the acquisition probe. The temperature control is achieved by using heating tubes, ceramic heating plates, head electric heating anti-icing devices and window electric heating anti-icing devices 11 (such as thermocouples) at the head 9 of the first measuring arm, the head of the second measuring arm, the laser emission window 5, and the signal collection window 10. The total power is 1000W. The temperature change of the key area inside the device is detected by the temperature control instrument, and the heating switch is controlled to avoid excessive heating temperature. In addition, the aviation box is customized according to the shape of the acquisition probe, and the shape of the internal filler fits the shape of the acquisition probe to prevent bumps and vibrations during transportation from changing the internal optical path structure of the device.

[0085] The power supply of the acquisition probe provided in this embodiment adopts two 24V DC power supplies with power of 1000W and 500W respectively, which are used for heating power supply and component power supply. An air switch is installed to prevent circuit overload. The power interface is used to connect the power supply line, communication line and signal line of the acquisition probe. There are also two external power interfaces connected to the 220V power supply and the remote control computer respectively. The power control system couples the communication line of the temperature control instrument, the communication line of the signal generator, the communication line of the pulse laser, and the signal transmission line of the camera into a network cable to realize remote control of the instrument.

[0086] Figure 5 The interference fringe signal of the water droplets captured in the mixed phase wind tunnel test of this embodiment is displayed, and the corresponding particle size of the water droplets is obtained through frequency domain analysis and processing. Figure 6 The speckle signals of different ice crystals measured in the wind tunnel and the corresponding spectrum images after two-dimensional Fourier transformation are shown in this embodiment. The two-dimensional Fourier transformation images corresponding to different speckles are quite different, which is related to the shape of the ice crystals. This embodiment simultaneously records the interference fringe signals of droplets and the speckle signals of ice crystals. The signal characteristics are obviously different, which verifies the feasibility of the acquisition probe provided by this embodiment to identify the phase state during the measurement of mixed phases in the cloud and fog field.

[0087] In summary, the cloud and fog particle collection probe based on the interference particle interference imaging technology provided by the present invention has a compact and sturdy structure, good aerodynamic performance, and can ensure the stable operation of the internal system in complex and harsh environments. The collection probe mainly includes a sheet laser emission unit, a scattered light signal collection unit, and a mechanical unit: a miniaturized interference particle interference imaging photoelectric system is used to emit a sheet pulse laser beam to irradiate particles, generate, collect and record scattered light interference signals; the mechanical unit is used to protect the internal components of the collection probe and control the external flow field, install and fix the photoelectric system, and ensure the normal operation of the optical technology in a low-temperature, high-speed and humid environment through sealing, electric heating and other protective methods. The present invention proposes an integrated collection probe for an optical system, which can reduce the influence of the external flow field, improve its operational stability and anti-interference, and can realize online measurement of cloud and fog particle parameters through interference particle interference imaging technology in different industrial environments, greatly increasing its scope of application.

Claims

1. A cloud and fog particle collection probe based on interferometric particle imaging, characterized in that: The probe comprises: The sheet laser emitting unit is used to emit a sheet pulse laser beam, expand the beam, adjust the incident position and the incident angle, and generate a scattered light signal after irradiating the cloud particles; A scattered light signal acquisition unit, used for collecting scattered light signals and recording them on a camera; The mechanical unit comprises a first measuring arm for mounting the sheet laser unit and a second measuring arm for mounting the scattered light signal acquisition unit, wherein the first measuring arm and the second measuring arm are connected via a connecting section and mounted on a base; The signal processing system is used to process the scattered light interference signal recorded by the camera to obtain the cloud particle parameters.

2. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1 is characterized in that: The sheet laser emitting unit comprises a pulse laser, a plano-concave cylindrical lens, a plano-convex cylindrical lens and a laser reflecting mirror. The pulse laser beam generated by the pulse laser is expanded by the plano-concave cylindrical lens and adjusted by the plano-convex cylindrical lens to form a parallel and uniform sheet pulse laser, which is then changed in direction by the laser reflecting mirror to irradiate the cloud particles.

3. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1 is characterized in that: The scattered light signal collection unit comprises a signal reflector, a collection lens and a camera. The signal reflector and the collection lens cooperate to collect the scattered light signal and record it on the camera.

4. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 3 is characterized in that: The camera is located at the defocusing position of the collection lens in the scattered light signal collection unit.

5. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1, characterized in that: The main optical axis of the sheet-shaped laser emitting unit and the main optical axis of the scattered light signal collecting unit are located on the same horizontal plane and have an included angle of 45° to 90°.

6. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1, characterized in that: The first measuring arm and the second measuring arm each include a head, a middle portion and a tail portion, the head portion is wedge-shaped, the cross-section of the middle portion is circular, and the tail portion is conical; the middle portion of the first measuring arm and the middle portion of the second measuring arm are connected by a connecting section to form a symmetrical structure; an electric heating anti-icing device is provided inside the first measuring arm, the second measuring arm and the connecting section.

7. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1, characterized in that: The head of the first measuring arm is provided with a laser emitting window, and the head of the second measuring arm is provided with a signal collecting window. Both the laser emitting window and the signal collecting window are provided with symmetrical boss structures, drainage grooves and wedge structures.

8. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 7, characterized in that: The walls of the laser emission window and the signal collection window are both provided with electric heating anti-icing devices.

9. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1, characterized in that: The front edge of the base is an arc, and the base is connected to the connecting section through a sealing groove.

10. The cloud and fog particle collection probe based on interferometric particle imaging according to claim 1, characterized in that: The method for the signal processing system to process the scattered light interference signal recorded by the camera to obtain the cloud and fog particle parameters is: When the scattered light interference signal is the interference fringe signal of the droplet, the particle size of the cloud particle droplet is obtained by inverting the fringe image; When the scattered light interference signal is the speckle signal of ice crystals, the particle size of ice crystals of cloud particles can be obtained by inverting the speckle image; Output cloud particle parameters according to the droplet size and ice crystal size, including particle phase change, particle size distribution, uniformity and liquid water content.

Images