A device and method for measuring three-dimensional rainbow refraction of liquid droplets in a space body

Abstract

The present invention discloses a three-dimensional rainbow refraction device for measuring droplets in a space body: a laser light source emission and atomized droplet generation system: a laser, a beam modulation element and an atomization device; a rainbow signal acquisition system: a convex lens, a horizontal slit aperture, a cylindrical lens and a digital camera; a rainbow signal processing system for processing three-dimensional rainbow images. The present invention also discloses a three-dimensional rainbow refraction method: a beam expander light source irradiates droplets in a space body to generate rainbow signals, which are recorded on a camera in the form of stripe blocks of different outline sizes; a three-dimensional scattering angle calibration is performed on the space body to be measured; the three-dimensional position of the droplets is determined according to the plane position and outline size of the rainbow signal, and the rainbow signal is extracted and inverted in combination with the three-dimensional scattering angle calibration result to obtain the refractive index and particle size. The device and method can realize the online measurement of fuel atomization field, droplet evaporation and combustion and other processes, and has the characteristics of non-contact, three-dimensional, high-precision and in-situ online.

Description

Technical Field

[0001] The invention relates to the field of gas-liquid two-phase flow measurement, and in particular to a three-dimensional rainbow refraction device and method capable of measuring liquid droplets in a space body. Technical Background

[0002] Atomized droplets are widely present in energy, chemical industry and other industrial fields: for example, in aircraft engines or internal combustion engines, fuel is atomized into droplets, mixed with air, evaporated and burned, and the chemical energy of the fuel is converted into mechanical kinetic energy, providing a continuous source of power for the engine; during fire fighting, water is sprayed from a high-pressure water gun and atomized into small droplets, which evaporate and absorb heat from the environment, and also play the role of oxygen isolation and suffocation and attenuation of thermal radiation, and finally achieve fire extinguishing; food and medicine to be dispersed are mixed in the dispersant to make a suspension, which is atomized into droplets through the nozzle and dried in a hot air environment to form powder particles of suitable size and uniformity. The physical and chemical reactions involved in these processes are all related to the properties of the droplets. The key parameters of the droplets, such as particle size and distribution, velocity, temperature, concentration and spatial distribution, not only affect the working performance and quality of the equipment, but also have great economic significance and far-reaching social significance for achieving efficient and clean utilization of energy, enhancing fire extinguishing effects, optimizing and improving production efficiency, controlling environmental pollution and protecting personal health. Studying and measuring these key parameters of droplets and their changing patterns helps us gain a deeper understanding of the interaction between droplets and the surrounding environment, and has important guiding significance for theoretical model verification, system design optimization, and safe and efficient operation.

[0003] Traditional droplet measurement technology is mainly based on contact measurement, such as using thermocouples to measure temperature, instantaneous sampling method to measure component concentration, collection method to measure spray field flow and mixing ratio, sedimentation method to measure particle size and distribution, etc. The above contact measurement method is simple to operate and has high accuracy, but its measurement device will interfere with the field to be measured; and it is impossible to achieve online measurement. With the rapid development of fields such as optics, information and computers, and the gradual increase in requirements for droplet parameter measurement in different occasions, non-contact (non-invasive) droplet online measurement technology based on optical principles has received widespread attention and development. Compared with traditional measurement technology, optical measurement technology has the advantages of non-contact, high temporal and spatial resolution, online real-time and high measurement accuracy. Therefore, it is widely used in the measurement of droplet parameters such as particle size, concentration and velocity.

[0004] By recording the second-order refraction signal and the direct reflection signal near the geometric rainbow angle, the rainbow refraction technique is a rare optical measurement method that can simultaneously measure thermodynamic parameters (refractive index, temperature, composition, etc.) and geometric parameters (particle size) online. Compared with two-color laser induced fluorescence, laser induced phosphorescence and Raman scattering, the rainbow refraction measurement system is simple to install, low-cost and can achieve one-dimensional and two-dimensional measurements. Therefore, in recent years, the rainbow refraction technique has been applied by domestic and foreign scholars to cold-state measurements such as flash atomization droplet groups, liquid-liquid systems, CO2 absorption, cryogenic spray, spray mixing ratio and non-spherical droplets, and hot-state measurements such as droplet evaporation and combustion.

[0005] After decades of development, advanced droplet optical measurement technology has bottlenecks in terms of time and space scales. The droplet atomization process is multi-field coupled and highly transient in many practical scenarios, especially in extreme environments (for example, the duration in automotive fuel injection is a few milliseconds or less), which puts higher requirements on the measurement of the atomization process. On the one hand, the density of measurement data per unit time can be increased by improving the performance of hardware equipment (such as high-speed cameras and pulsed lasers) or increasing the number of hardware equipment. On the other hand, in the face of the measurement requirements of complex multiphase flows, it also prompts the measurement technology to develop in the direction of high dimensions, etc., to meet this challenge at the level of technological innovation.

[0006] The development of rainbow refraction technology from single point to one dimension and two dimensions has realized "line" and "surface" measurement, which not only effectively increases the density of measurement data, but more importantly, can capture the evolution of key parameters of droplets moving along the measurement line and measurement surface. However, this method still has certain limitations, because it can only record the evolution of droplets moving along the measurement line or measurement surface, and in fact the motion trajectory of atomized droplets is changeable, and it is impossible to move along the trajectory of the measurement line or measurement surface. Compared with the measurement line or measurement surface, the droplets must move in a spatial body. Expanding the spatial measurement dimension of the droplets to be measured is greatly beneficial to the evolution measurement of key parameters of droplets in the atomization field, which has prompted the invention of rainbow refraction technology from one-dimensional "line" and two-dimensional "surface" to three-dimensional "body" measurement. Summary of the invention

[0007] The purpose of the present invention is to further expand the measurement dimension of the rainbow refraction method, and to provide a three-dimensional rainbow refraction device and method for droplets in a spatial body, which can analyze the gas-liquid two-phase flow or gas-liquid-solid three-phase flow involving droplets, and realize the online measurement of fuel atomization field, droplet evaporation and combustion and other processes, and has the characteristics of non-contact, three-dimensional, high precision and in-situ online.

[0008] The specific technical solution adopted by the present invention to solve the above technical problems is:

[0009] A three-dimensional rainbow refraction device for measuring droplets in a space body, the device comprising:

[0010] The laser body light source emission and atomized droplet generation system comprises a laser, a beam modulation element and an atomization device; the laser beam emitted by the laser is modulated into a vertically polarized body light source by the beam modulation element, and irradiates the atomized droplets generated by the atomization device in the space to be measured to form a rainbow signal; the beam modulation element comprises a vertical polarizer, a plano-concave spherical lens and a plano-convex spherical lens in sequence;

[0011] The rainbow signal acquisition system includes a convex lens, a horizontal slit aperture, a cylindrical lens and a digital camera in sequence, and is used to separate and image the rainbow signals generated by the atomized droplets at different positions in the measured space, record and obtain a three-dimensional rainbow image, and transmit it to the rainbow signal processing system;

[0012] The rainbow signal processing system processes the three-dimensional rainbow image to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the measured space.

[0013] The laser is a continuous laser or a pulsed laser; the atomizing device is a pneumatic or pressure atomizing nozzle. The continuous laser or pulsed laser is used to generate a coherent light beam with adjustable intensity and good beam characteristics; the beam modulating element is used to modulate the outgoing laser beam into a vertically polarized body laser; the atomizing device, such as a pneumatic or pressure atomizing nozzle, is used to generate a group of atomized droplets to be tested;

[0014] The continuous laser is a semiconductor laser with adjustable intensity of 0mW to 5W, a wavelength of 400nm to 760nm in the visible light band, and a beam waist radius of 0.4mm to 2mm; the pulse laser is a solid laser with adjustable single pulse energy of 0mJ to 100mJ, a pulse width of 1ns to 500ns, a wavelength of 400nm to 760nm in the visible light band, and a beam waist radius of 0.4mm to 2mm;

[0015] Among them, in the beam modulation element, the laser beam emitted by the laser becomes a vertical linear polarized laser beam after passing through the polarizer, and then is expanded into a volume light source by the plano-concave spherical lens and the plano-convex spherical lens to irradiate the atomized droplets in the space to be measured. Preferably, the focal length of the plano-concave spherical lens is -20mm to -5mm, and the focal length of the plano-convex spherical lens is 50mm to 200mm; the diameter of the vertically polarized volume light source is not less than 20mm.

[0016] The space body to be measured is a cube formed with the optical axis x of the rainbow signal acquisition system as one side, and the other two sides of the space body to be measured are parallel to the coordinate axes y and z respectively.

[0017] Among them, in the rainbow signal acquisition system, the rainbow signals of atomized droplets at different positions in the space to be tested are collected by a convex lens; a horizontal slit aperture is provided at the rear focal length of the convex lens, so that only scattered light vertically incident on the convex lens in the height direction can pass through, thereby filtering scattered light in other directions, so that the rainbow signals of atomized droplets at different heights are separately imaged and recorded on different rows of pixels of the digital camera, and the rainbow signals of atomized droplets at different horizontal positions are separately imaged and recorded in the form of striped blocks on different columns of pixel blocks of the digital camera; the rainbow signals of atomized droplets at different depths have signal profiles of different sizes; a vertically placed cylindrical lens is provided behind the horizontal slit aperture to adjust the width of the rainbow signal on the digital camera in the horizontal direction.

[0018] The width of the horizontal slit aperture is variable, ranging from 0.1mm to 10mm; the diameter of the convex lens is 50mm to 200mm, and the focal length is 50mm to 250mm; the cylindrical lens is a plano-concave cylindrical lens, and the focal length is -200mm to -5mm; the digital camera is an array camera (such as CCD or CMOS), with a pixel range of 1M to 16M, a recording scattering angle range of 6° to 20°, an angular resolution of not less than 0.002°, and an exposure time of 1μs-1000ms adjustable. Depending on the measurement object and measurement conditions, the camera exposure time can be adjusted to achieve the best measurement effect;

[0019] The rainbow signal processing system comprises a computer and a synchronous controller; the computer is connected to and synchronously controls the laser and the digital camera through the synchronous controller, including controlling the switch and intensity of the laser and the switch and exposure time of the digital camera (when the laser is a pulse laser, the frequency of the pulse light and the digital camera is also synchronously controlled); the collected three-dimensional rainbow image is transmitted to the computer for processing to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the space to be measured;

[0020] The method for obtaining the three-dimensional position of the atomized droplets in the space to be measured is as follows:

[0021] For the atomized droplet located in the space to be measured, its position on the xy plane is recorded as (x s ,y s ), the light transmission matrices from the droplet to the digital camera in the horizontal and vertical directions are and The angles in the horizontal and vertical directions are (θ s , ) After the scattered light near the geometric rainbow angle passes through the rainbow signal acquisition system, the position of the geometric center of the rainbow signal on the digital camera (x r ,y r ) can be expressed as:

[0022]

[0023]

[0024] The light transmission matrix system is being implemented. x ≠0, to ensure that they are at the same height y s , different horizontal positions x s The rainbow signal of the droplet can be separated in the horizontal direction by a digital camera; A y ≠0, to ensure that they are at the same horizontal position x s , different heights s The rainbow signal of the droplet can be separated in the vertical direction of the digital camera. The geometric center of the rainbow signal of the droplet at the same xy plane position and different z depth positions on the digital camera is the same, but the outline size is different. By calibrating the relationship between the depth position and the outline size, the depth information of the third dimension can be determined.

[0025] The present invention also provides a method for measuring the three-dimensional rainbow refraction of a droplet in a space body, using the above-mentioned three-dimensional rainbow refraction device, comprising the following steps:

[0026] (1) Calibrate the three-dimensional scattering angles of different positions in the measured space of the three-dimensional rainbow refraction device;

[0027] (2) Turn on the atomization device and adjust the atomized droplet group to a stable working state;

[0028] (3) Turn on the laser, and after the laser beam emitted by the laser is modulated by a polarizer, a plano-concave spherical lens, and a plano-convex spherical lens, it is irradiated onto the atomized droplets in the space to be measured in the form of a vertically polarized light source;

[0029] (4) The rainbow signal is collected by a convex lens and converged to propagate backwards, passing through a horizontal slit aperture and a plano-concave cylindrical lens in sequence, so that the rainbow signals of atomized droplets at different heights are separated and imaged on different rows of pixels of a digital camera, and the rainbow signals of atomized droplets at different horizontal positions are separated and imaged on different columns of pixels of a digital camera in the form of stripe blocks. The outline sizes of the rainbow signals of atomized droplets at different depths are different;

[0030] (5) adjusting the width of the horizontal slit aperture and the position of the plano-concave cylindrical lens to control the height and position of the rainbow stripe block until a clear and appropriately sized three-dimensional rainbow image is obtained;

[0031] (6) Combined with the three-dimensional scattering angle calibration results, the rainbow signal processing system processes the three-dimensional rainbow image to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the measured space.

[0032] The three-dimensional scattering angle calibration described in step (1) is to obtain the relationship between the scattering angle at different positions in the measured space and the corresponding position of the digital camera pixel. Since the corresponding relationship between the scattering angle and the pixel position at each position in the three-dimensional space is inconsistent, the entire calibration process is relatively complicated. The calibration method is as follows:

[0033] (1-1) Using a monodisperse droplet generation system, a monodisperse droplet stream with known particle size D and refractive index n is generated in a direction parallel to the y-axis;

[0034] (1-2) In the space to be tested, the depth position z is divided into several intervals with equal intervals, and a three-dimensional displacement stage is used to sequentially move the droplet flow from one edge of the space to be tested to another edge along the x-axis direction in each interval, and the droplet flow stops at several discrete positions in between; each time the droplet flow stops at a position, it is irradiated by a vertically polarized volume light source, and a rainbow signal acquisition system will collect and record a calibration experimental rainbow signal of the droplet flow at the position, and the calibration experimental rainbow signal is a function of the scattering intensity distribution with respect to the pixel position of the digital camera;

[0035] (1-3) Based on the known particle size D and refractive index n of the droplet flow, the Mie theory is used to simulate and calculate the accurate calibration theoretical rainbow signal, which is a function of the scattering intensity distribution with respect to the scattering angle;

[0036] (1-4) Combined with the global optimization algorithm, the calibration experimental rainbow signal collected at each discrete position of the plane xy is fitted and matched with the calibration theoretical rainbow signal, and the calibration relationship between the scattering angle and the pixel position at each discrete position of the plane is obtained in turn, and the interpolation method is further used to fit the calibration relationship between the scattering angle and the pixel position at a certain depth position in the entire xy plane;

[0037] (1-5) Record and calibrate the corresponding relationship between the rainbow signal contour size and the depth position z at the same plane position and different discrete depth positions. Use interpolation fitting to obtain the depth position information of the entire space to be measured and complete the three-dimensional scattering angle calibration of the space to be measured.

[0038] Among them, the monodisperse droplet generation system includes a monodisperse droplet generator, a high-pressure injection pump, a signal generator and an adapter, etc.

[0039] The method for processing the three-dimensional rainbow image in step (6) includes:

[0040] (6-1) Based on the recorded three-dimensional rainbow image, image recognition locates the geometric center of the rainbow signal of each droplet in the test space on the digital camera (x r ,y r );

[0041] For the atomized droplet located in the space to be measured, its position on the xy plane is recorded as (xs ,y s ), the light transmission matrices from the droplet to the digital camera in the horizontal and vertical directions are and The angles in the horizontal and vertical directions are (θ s , ) After the scattered light near the geometric rainbow angle passes through the rainbow signal acquisition system, the position of the geometric center of the rainbow signal on the digital camera (x r ,y r ) can be expressed as:

[0042]

[0043]

[0044] The light transmission matrix system is being implemented. x ≠0, to ensure that they are at the same height y s , different horizontal positions x s The rainbow signal of the droplet can be separated in the horizontal direction by a digital camera; A y ≠0, to ensure that they are at the same horizontal position x s , different heights s The rainbow signal of the droplet can be separated in the vertical direction of the digital camera. The geometric center of the rainbow signal of the droplet at the same xy plane position and different z depth positions on the digital camera is the same, but the outline size is different;

[0045] (6-2) Combined with the transmission matrix parameter A in the rainbow signal acquisition system x , A y , B x , B y The angle between the rainbow signal in the horizontal and vertical directions (θ s , ), the plane position (x s ,y s ), where x s =(x r -B x θ s ) / A x ,

[0046] (6-3) By calibrating the relationship between the depth position and the contour size, the depth position of the droplet to be measured is calculated according to the contour size of the rainbow signal;

[0047] (6-4) Combined with the pre-calibrated three-dimensional scattering angle relationship, the angular distribution of the rainbow signal intensity of each droplet in the measured space is extracted on the computer at the same time, and the optimized objective function is iteratively calculated:

[0048]

[0049] Among them, I r (θ) is the rainbow signal collected in the experiment, I f (D, n, θ) is the rainbow signal of the inversion fitting, θ is the scattering angle, D is the droplet diameter, and n is the refractive index;

[0050] (6-5) When the difference between the rainbow signal collected experimentally and the rainbow signal obtained by inversion fitting is less than a preset threshold, the inversion ends and the particle size and refractive index of the droplets are obtained; thus, the three-dimensional position, particle size and refractive index of each atomized droplet in the measured space are obtained.

[0051] Compared with the prior art, the beneficial effects of the present invention are: further expanding the measurement dimension of the rainbow refraction method, and proposing a three-dimensional rainbow refraction device and method. It can simultaneously measure the position, particle size and refractive index of atomized droplets at different positions in the measured space in situ online; combined with the relationship between the refractive index of the droplets and key parameters such as temperature or composition, through time-continuous measurement, the three-dimensional distribution evolution law of parameters such as droplet temperature or composition can be further obtained. The device of the present invention has the characteristics of simple device structure and high precision.

[0052] The device and method provided by the present invention can analyze the gas-liquid two-phase flow field and realize the three-dimensional plane online measurement of the fuel atomization, evaporation and other processes, and has the characteristics of three-dimensional, real-time transient and non-contact. The present invention will provide a better testing method for the study of non-steady complex spray flow field, which is of great significance for a more comprehensive and in-depth study of the spray mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the overall structure and optical path system of the three-dimensional rainbow refraction device of the present invention;

[0054] Figure 2 It is a top view and a side view of the device of the present invention collecting rainbow signals of droplets at different spatial positions;

[0055] Figure 3 This is a schematic diagram of the scattering angle of the space to be measured by the monodisperse droplet flow system in the present invention;

[0056] Figure 4 It is a typical three-dimensional rainbow signal recorded in the embodiment of the present invention;

[0057] In the figure: 1. laser, 2. polarizer, 3. plano-concave spherical lens, 4. plano-convex spherical lens, 5. laser body light source, 6. space body to be measured, 7. atomized droplets, 8. atomization device, 9. rainbow signal, 10. convex lens, 11. horizontal slit aperture, 12. vertical plano-concave cylindrical lens, 13. digital camera, 14. collected rainbow signal, 15. computer, 16. synchronization controller, 17. first droplet, 18. second droplet, 19. third droplet, 20. rainbow signal of the first droplet, 21. rainbow signal of the second droplet, 22. rainbow signal of the third droplet, 23. monodisperse droplet stream, 24. monodisperse droplet generator, 25. three-dimensional translation stage, 26. adapter, 27. high-pressure injection pump, 28. signal generator. DETAILED DESCRIPTION

[0058] The specific implementation of the technical solution of the present invention is further described below through examples and in conjunction with the accompanying drawings.

[0059] like Figure 1 As shown, the three-dimensional rainbow refraction device provided by the present invention comprises:

[0060] a. Laser body light source emission and atomized droplet generation system, the laser beam emitted by the laser 1 is modulated into a vertically polarized body light source 5 by a beam modulation element, irradiating the atomized droplets 7 generated by the atomization device 8 in the space body 6 to be measured, forming a rainbow signal 9. The laser body light source emission and atomized droplet generation system consists of three parts:

[0061] Laser 1, used to generate a coherent light beam with adjustable intensity and good beam characteristics; the laser 1 of this embodiment is a 0-2000mW adjustable light intensity semiconductor laser, with a wavelength of 532nm and a beam waist radius of 1mm;

[0062] The beam modulation element includes a vertical polarizer 2, a plano-concave spherical lens 3 and a plano-convex spherical lens 4, which are used to modulate the outgoing laser beam into a vertically polarized volume light source 5; the focal length of the plano-concave spherical lens 3 is -5mm, and the focal length of the plano-convex spherical lens 4 is 200mm; the laser volume light source 5 propagates in parallel and has a diameter of 41mm.

[0063] The atomizing device 8 is used to spray out a solid cone atomized droplet group, and in this embodiment, it is a pneumatic nozzle.

[0064] b. A rainbow signal acquisition system, which is used to record the rainbow signals 9 generated by the atomized droplets 7 at different positions in the space body 6 to be tested separately on a digital camera 13 through the signal acquisition system, and obtain the three-dimensional position, particle size and refractive index of the atomized droplets 7 in the space body 6 to be tested through processing by a computer 15. The rainbow signal acquisition system includes a convex lens 10, a horizontal slit 11, a vertical plano-concave cylindrical lens 12 and a digital camera 13. The rainbow signals 9 of the atomized droplets 7 at different positions in the space body 6 to be tested are collected by the convex lens 10, and converge and propagate backward. The horizontal slit aperture 11 provided at the rear focal length of the convex lens 10 allows only the scattered light that is vertically incident on the convex lens 10 to pass in the height direction, thereby filtering the scattered light in other directions. The vertical plano-concave cylindrical lens 12 is placed between the horizontal slit aperture 11 and the digital camera 13, and is used to adjust the width of the rainbow signal in the horizontal direction without affecting the propagation of the collected rainbow signal 14 in the vertical direction. Figure 2 As shown, the rainbow signals 21 and 22 of the atomized droplets 17 and 19 at different heights are imaged separately on different rows of pixels of the digital camera 12; the rainbow signals 20 and 21 of the atomized droplets 17 and 18 at different horizontal positions are imaged separately on different columns of pixel blocks of the digital camera 13 in the form of stripe blocks; the contour sizes of the rainbow signals 21 and 22 of the atomized droplets 17 and 19 at different depths are different; in this example, the farther away from the measurement system, the larger the contour. The diameter of the convex lens 10 is 100 mm and the focal length is 150 mm; the width of the horizontal slit aperture 11 is variable, ranging from 0.1 mm to 2 mm. The digital camera 13 is a planar array CMOS camera with 8M pixels. The acquisition system records a scattering angle range of 15° and an angular resolution of 0.002°. The rainbow signal processing system includes a computer 15 and a synchronous controller 16. The computer 15 is connected to and synchronously controls the laser 1 and the digital camera 13 through the synchronous controller 16, including controlling the switch and intensity of the laser 1 and the switch and exposure time of the digital camera 13 (when the laser 1 is a pulse laser, the frequency of the pulse light and the digital camera 13 is also synchronously controlled).

[0065] c. Rainbow signal processing system, for example Figure 4 The rainbow signal of each droplet in the three-dimensional rainbow image shown is processed to obtain the three-dimensional position, particle size and refractive index of the droplet.

[0066] The method for measuring the three-dimensional rainbow refraction of a droplet in a space body by using the above device comprises the following steps:

[0067] (1) Calibrate the three-dimensional scattering angle of the space to be measured by the three-dimensional rainbow refraction device, such as Figure 3 As shown, the calibration method of this embodiment is:

[0068] A monodisperse droplet generating system consisting of a monodisperse droplet generator 24, a high pressure injection pump 27, a signal generator 28 and an adapter 26 is used, such as Figure 3 As shown, a monodisperse droplet stream 23 with known particle size D and refractive index n is generated, and the direction is parallel to the y-axis. In the space body 6 to be tested, the depth position z is divided into several intervals with equal spacing. The three-dimensional displacement stage 25 is used to move the droplet stream 23 from the edge of the space body 6 to be tested in each interval along the x-axis direction from the other edge, and stops at several discrete positions in the middle. The stop position of the droplet stream 23 is shown in FIG. Figure 3 The cross mark shown. Every time the droplet stream 23 stays at a position, after being irradiated by the vertically polarized laser body light source 5, the rainbow signal acquisition system will collect and record the calibration experimental rainbow signal of the droplet stream 23 at that position. According to the known particle size D and refractive index n of the droplet stream 23, the accurate calibration theoretical rainbow signal is simulated and calculated using the Mie theory. The calibration experimental rainbow signal is a function of the scattering intensity distribution with respect to the pixel position of the digital camera, and the calibration theoretical rainbow signal is a function of the scattering intensity distribution with respect to the scattering angle. Combined with the global optimization algorithm, the calibration experimental rainbow signal collected at each discrete position of the xy plane is fitted and matched with the calibration theoretical rainbow signal, and the calibration relationship of the scattering angle-pixel position at each discrete position of the plane is obtained in turn, and the interpolation method is further used to fit the calibration relationship of the scattering angle-pixel position of the entire xy plane at a certain depth position. The corresponding relationship between the contour size of the rainbow signal and the depth position z at different discrete depth positions at the same plane position is calibrated, and the depth position information of the entire space body 6 to be measured can be obtained by interpolation fitting. That is, the three-dimensional scattering angle calibration of the space body 6 to be measured is completed.

[0069] (2) Open Figure 1 The atomizing device 8 shown adjusts the atomized droplet group to a stable working state;

[0070] (3) Turn on the laser 1. The laser beam emitted by the laser 1 is modulated by the vertical polarizer 2, the plano-concave spherical lens 3, and the plano-convex spherical lens 4, and then irradiates the atomized droplets 7 in the space body 6 to be measured in the form of a vertically polarized volume light source 5. The rainbow signals 9 of the droplets at different spatial positions are collected by the rainbow signal collection system;

[0071] (4) Adjust the width of the horizontal slit aperture 11 and the position of the vertical plano-concave cylindrical lens 12 to control the height and position of the rainbow stripe block until a clear and appropriately sized image is obtained. Figure 4 The three-dimensional rainbow image shown;

[0072] (5) Turn on the digital camera 13, and separate the rainbow signals 9 of the atomized droplets 7 at different positions in the measured space body 6 into images in the form of stripe blocks with different outline sizes on pixel blocks of different rows and columns of the digital camera 13, as shown in FIG. Figure 2 ;

[0073] (6) Combined with the three-dimensional scattering angle calibration results, the rainbow signal processing system records the Figure 4The rainbow signals of each droplet in the three-dimensional rainbow image shown are identified, located and inverted in turn to obtain the three-dimensional position, particle size and refractive index of the atomized droplet in the space body 6 to be measured;

[0074] According to the records Figure 4 The three-dimensional rainbow image shown in the figure is firstly image-recognized to locate the geometric center of the rainbow signal of each droplet on the digital camera 13 (x r ,y r ), combined with the calibration of the linear recording of the droplet plane position by the rainbow signal acquisition system, the plane position of each droplet (x s ,y s ). Secondly, the z depth position of each droplet is calculated according to the contour size of the rainbow signal of each droplet, and the three-dimensional position information of each droplet in the measured space body 6 is obtained. On this basis, combined with the pre-calibrated relationship of the three-dimensional scattering angle, the fitting optimization objective function of the rainbow signal of each droplet in the measured space body 6 is iteratively calculated on the computer 15 at the same time: The particle size and refractive index of each droplet in the space body 6 to be measured are obtained by inversion.

[0075] In addition to the above-mentioned embodiments, within the scope disclosed in the claims and the specification of the present invention, the technical features or technical data of the present invention can be reselected and combined to form new embodiments, which can be achieved by those skilled in the art without creative work. Therefore, these embodiments that are not described in detail in the present invention should also be regarded as specific embodiments of the present invention and within the protection scope of the present invention.

Claims

1. A three-dimensional rainbow refraction device for measuring droplets in a space body, characterized in that: The device comprises: The laser body light source emission and atomized droplet generation system comprises a laser, a beam modulation element and an atomization device; the laser beam emitted by the laser is modulated into a vertically polarized body light source by the beam modulation element, and irradiates the atomized droplets generated by the atomization device in the space to be measured to form a rainbow signal; the beam modulation element comprises a vertical polarizer, a plano-concave spherical lens and a plano-convex spherical lens in sequence; The rainbow signal acquisition system includes a convex lens, a horizontal slit aperture, a cylindrical lens and a digital camera in sequence, and is used to separate and image the rainbow signals generated by the atomized droplets at different positions in the measured space, record and obtain a three-dimensional rainbow image, and transmit it to the rainbow signal processing system; The rainbow signal processing system processes the three-dimensional rainbow image to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the measured space; The focal length of the plano-concave spherical lens is -20mm to -5mm; the focal length of the plano-convex spherical lens is 50mm to 200mm; the diameter of the vertically polarized volume light source is not less than 20mm; The rainbow signals of atomized droplets at different positions in the measured space are collected by a convex lens; a horizontal slit aperture is provided at the rear focal length of the convex lens, so that only scattered light vertically incident on the convex lens can pass in the height direction, thereby filtering scattered light in other directions, so that the rainbow signals of atomized droplets at different heights are separately imaged and recorded on different rows of pixels of the digital camera, and the rainbow signals of atomized droplets at different horizontal positions are separately imaged and recorded in the form of stripe blocks on different columns of pixel blocks of the digital camera; the rainbow signals of atomized droplets at different depths have signal profiles of different sizes; a vertically placed cylindrical lens is provided behind the horizontal slit aperture to adjust the width of the rainbow signal on the digital camera in the horizontal direction.

2. The three-dimensional rainbow refraction device for measuring droplets in a space body as claimed in claim 1, characterized in that: The laser is a continuous laser or a pulsed laser; the atomizing device is a pneumatic or pressure atomizing nozzle.

3. The three-dimensional rainbow refraction device for measuring droplets in a space body as claimed in claim 2, characterized in that: The continuous laser is a semiconductor laser with adjustable intensity from 0mW to 5W, a wavelength in the visible light band of 400nm to 760nm, and a beam waist radius of 0.4mm to 2mm; the pulse laser is a solid laser with adjustable single pulse energy from 0mJ to 100mJ, a pulse width between 1ns and 500ns, a wavelength in the visible light band of 400nm to 760nm, and a beam waist radius of 0.4mm to 2mm.

4. The three-dimensional rainbow refraction device for measuring droplets in a space body as claimed in claim 1, characterized in that: The width of the horizontal slit aperture is variable, ranging from 0.1mm to 10mm; the diameter of the convex lens is 50mm to 200mm, and the focal length is 50mm to 250mm; the cylindrical lens is a plano-concave cylindrical lens, and the focal length is -200mm to -5mm; the digital camera is an area array camera, with a pixel range of 1M to 16M, a recorded scattering angle range of 6° to 20°, an angular resolution of not less than 0.002°, and an exposure time adjustable from 1μs to 1000ms.

5. The three-dimensional rainbow refraction device for measuring droplets in a space body as claimed in claim 1, characterized in that: The rainbow signal processing system comprises a computer and a synchronous controller; the computer is connected to and synchronously controls a laser and a digital camera through the synchronous controller, including controlling the switch and intensity of the laser and the switch and exposure time of the digital camera; when the laser is a pulse laser, the frequency of the pulse light and the digital camera is also synchronously controlled; the collected three-dimensional rainbow image is transmitted to the computer for processing to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the space to be measured.

6. A method for measuring the three-dimensional rainbow refraction of a droplet in a space body using the device described in any one of claims 1 to 5, characterized in that: The method comprises the following steps: (1) Calibrate the three-dimensional scattering angles of different positions in the measured space of the three-dimensional rainbow refraction device; (2) Turn on the atomization device and adjust the atomized droplet group to a stable working state; (3) Turn on the laser, and after the laser beam emitted by the laser is modulated by a polarizer, a plano-concave spherical lens, and a plano-convex spherical lens, it is irradiated onto the atomized droplets in the space to be measured in the form of a vertically polarized light source; (4) The rainbow signal is collected by a convex lens and converged to propagate backwards, passing through a horizontal slit aperture and a plano-concave cylindrical lens in sequence, so that the rainbow signals of atomized droplets at different heights are separated and imaged on different rows of pixels of a digital camera, and the rainbow signals of atomized droplets at different horizontal positions are separated and imaged on different columns of pixels of a digital camera in the form of stripe blocks. The outline sizes of the rainbow signals of atomized droplets at different depths are different; (5) adjusting the width of the horizontal slit aperture and the position of the plano-concave cylindrical lens to control the height and position of the rainbow stripe block until a clear and appropriately sized three-dimensional rainbow image is obtained; (6) Combined with the three-dimensional scattering angle calibration results, the rainbow signal processing system processes the three-dimensional rainbow image to obtain the three-dimensional position, particle size and refractive index of the atomized droplets in the measured space.

7. The method for measuring three-dimensional rainbow refraction of a droplet in a space body as claimed in claim 6, characterized in that: The three-dimensional scattering angle calibration described in step (1) is to obtain the relationship between the scattering angles at different positions in the measured space and the corresponding positions of the digital camera pixels. The calibration method is as follows: (1-1) Using a monodisperse droplet generation system, a monodisperse droplet flow with known particle size D and refractive index n is generated in a direction parallel to the y-axis; (1-2) In the space to be tested, the depth position z is divided into several intervals with equal intervals, and a three-dimensional displacement stage is used to sequentially move the droplet flow from one edge of the space to be tested to another edge along the x-axis direction in each interval, and the droplet flow stops at several discrete positions in between; each time the droplet flow stops at a position, it is irradiated by a vertically polarized volume light source, and a rainbow signal acquisition system will collect and record a calibration experimental rainbow signal of the droplet flow at the position, and the calibration experimental rainbow signal is a function of the scattering intensity distribution with respect to the pixel position of the digital camera; (1-3) Based on the known particle size D and refractive index n of the droplet flow, the Mie theory is used to simulate and calculate the accurate calibration theoretical rainbow signal, which is a function of the scattering intensity distribution with respect to the scattering angle; (1-4) Combined with the global optimization algorithm, the calibration experimental rainbow signal collected at each discrete position of the plane xy is fitted and matched with the calibration theoretical rainbow signal, and the calibration relationship between the scattering angle and the pixel position at each discrete position of the plane is obtained in turn, and the interpolation method is further used to fit the calibration relationship between the scattering angle and the pixel position at a certain depth position in the entire xy plane; (1-5) Record and calibrate the corresponding relationship between the rainbow signal contour size and the depth position z at the same plane position and different discrete depth positions, and also use interpolation fitting to obtain the depth position information of the entire space to be measured, and complete the three-dimensional scattering angle calibration of the space to be measured.

8. The method for measuring three-dimensional rainbow refraction of a droplet in a space body as claimed in claim 6, characterized in that: The method for processing the three-dimensional rainbow image in step (6) includes: (6-1) Based on the recorded three-dimensional rainbow image, image recognition locates the geometric center of the rainbow signal of each droplet in the test space on the digital camera (x r ,y r ); For the atomized droplet located in the space to be measured, its position on the xy plane is recorded as (x s ,y s ), the light transmission matrices from the droplet to the digital camera in the horizontal and vertical directions are and The angles in the horizontal and vertical directions are After the scattered light near the geometric rainbow angle passes through the rainbow signal acquisition system, the position of the geometric center of the rainbow signal on the digital camera (x r ,y r ) is expressed as: The light transmission matrix system is being implemented. x ≠0, to ensure that they are at the same height y s , different horizontal positions x s The rainbow signal of the droplet can be separated in the horizontal direction by a digital camera; A y ≠0, to ensure that they are at the same horizontal position x s , different heights s The rainbow signal of the droplet can be separated in the vertical direction of the digital camera; while the geometric center of the rainbow signal of the droplet at the same xy plane position and different z depth positions on the digital camera is the same, but the outline size is different; (6-2) Combined with the transmission matrix parameter A in the rainbow signal acquisition system x , A y , B x , B y The horizontal and vertical angles of the rainbow signal The plane position (x s ,y s ), where x s =(x r -B x θ s ) / A x , (6-3) By calibrating the relationship between the depth position and the contour size, the depth position of the droplet to be measured is calculated according to the contour size of the rainbow signal; (6-4) Combined with the pre-calibrated three-dimensional scattering angle relationship, the angular distribution of the rainbow signal intensity of each droplet in the measured space is extracted on the computer at the same time, and the optimized objective function is iteratively calculated: Among them, I r (θ) is the rainbow signal collected in the experiment, I f (D, n, θ) is the rainbow signal of the inversion fitting, θ is the scattering angle, D is the droplet diameter, and n is the refractive index; (6-5) When the difference between the rainbow signal collected experimentally and the rainbow signal obtained by inversion fitting is less than a preset threshold, the inversion ends and the particle size and refractive index of the droplets are obtained; thus, the three-dimensional position, particle size and refractive index of each atomized droplet in the measured space are obtained.

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