CN102313684A - System and method for real-time measurement of gas-solid two-phase flow field - Google Patents

Abstract

The invention provides a real-time measurement system and method for a gas-solid two-phase flow field. The system includes at least one solid-phase camera, at least two gas-phase cameras, a computing device and a display device. The method includes: 1) controlling at least one low-resolution, high-frame transfer time digital high-speed camera with a relatively large field of view and splicing with each other to acquire motion track images of solid-phase particles, and controlling at least two high-resolution, low-frame transfer cameras Digital high-speed cameras with a relatively small field of view and spliced with each other acquire the motion trajectory images of gas-phase fluorescent tracer particles; 2) respectively obtain the motion vector images of gas-solid two-phase particles; 3) synchronously output and display gas-solid two-phase Particle motion vector image. The invention expands the scope of application of the image velocity measurement technology, improves the efficiency of gas-solid two-phase flow measurement; avoids complex phase separation calculations; realizes the online measurement of gas-solid two-phase flow field; and provides quantitative research on particle agglomeration Dynamic evolution is possible.

Description

System and method for real-time measurement of gas-solid two-phase flow field

technical field

The invention relates to the technical field of multiphase flow laser measurement, in particular, the invention relates to a real-time measurement system and method for gas-solid two-phase flow flow field.

Background technique

The heat transfer, mass transfer and reaction performance of gas-solid two-phase flow reactors are closely related to the instantaneous kinetic behavior of mesoscale particle agglomeration in the reactor. Therefore, it is necessary to obtain and display online the flow information of micro-scale single particles or fluid micro-units and meso-scale particle aggregates, or even gas-solid two-phase flow information on the macro-reactor scale through high-precision, non-invasive measurement methods. The basis and key to develop a new type of high-efficiency gas-solid two-phase flow reactor.

Measurement techniques such as digital high-speed photography (CCD), positron emission tracking detection (PEPT) and nuclear magnetic resonance (MRI) can be used to track the trajectory of individual particles, but they are all limited to single-point measurement, and it is difficult to obtain gas-solid two-phase Two-dimensional velocity field or other relevant vector field information of the flow.

In the 1980s, the particle image velocimetry (PIV) technology, which comprehensively utilized modern computing technology, optical technology and image analysis technology, not only broke through the limitation of single-point measurement, but also realized the undisturbed measurement of the physical form of the flow field and provided Quantitative information on instantaneous full-field flow. In this technology, tracer particles are sprinkled into the flow field, and the velocity of the particles represents the velocity of the fluid at the corresponding position in the flow field. A plane in the flow field is irradiated with strong light, and the positions of particles exposed two or more times in a row are recorded by imaging method, and the displacement of particles at each point is obtained by image analysis technology, and the displacement and the time interval of exposure can be obtained The flow velocity vector and other motion parameters of each point in the flow field. However, it is difficult for the gas-solid two-phase phase to be clearly formed on the same film at the same time, coupled with the inherent contradiction between the resolution of the camera itself and the field of view, the existing PIV technology-based gas-solid two-phase flow field measurement method is limited to Measurement of single-phase flow in a small field of view. On the other hand, due to the limitations of the existing PIV technology in terms of data processing capacity and processing methods, the current image velocity measurement technology cannot measure and display the flow field in real time.

In recent years, a two-phase flow particle image velocimetry technology has emerged to realize the simultaneous measurement of fluid and solid phases in multiphase flow. This technology spreads tracer particles that can follow the flow of different phase fluids in the two-phase flow field, irradiates the area of the measured flow field with a laser light source, and obtains records through continuous exposure on the same negative film or continuous exposure on different negative films. The negative film of the particle displacement is traced, and finally the velocity distribution of the two-phase flow field is obtained by using a variety of specific image processing methods. Obviously, the digital image processing technology required for two-phase measurement is much more difficult than single-phase. It not only needs to distinguish the displacement of particles representing the same phase in a known time interval, but also distinguishes particles representing different phases. That is, the imaging of two-phase particles is to be separated. At present, the methods for separating two-phase particle imaging are mainly divided into two categories: one is to directly process the digital image of two-phase flow through a special software algorithm to separate the two phases after imaging the two-phase particles on the same film. However, due to the complexity of the two-phase particle image separation algorithm and the huge amount of calculation, it is difficult to achieve high-precision online measurement and display of two-phase motion vectors using this method. In addition, if the optical properties of the particles representing the two phases are different, it will be difficult for the two-phase tracer particles to be clearly imaged simultaneously on the same film; if the density of the two-phase tracer particles is different and the image is taken horizontally, the denser particles will It is easy to run out of the irradiated area of the sheet of light and it is easy to cause no relevant points of the tracer particles; if the slip velocity between the two-phase particles is too large, the measured velocity of the phase of the tracer particles The instant effect is poor. The other is to use hardware measures (such as using a special camera or changing the optical properties of particles, etc.) to obtain images of continuous-phase and discrete-phase tracer particles, respectively. This type of approach is currently limited to bubble flow in gas-liquid two-phase flow [Fuzio, et al. Proceedings of Int. Conf. on Fluids Eng., Kwangju, 1994; Tokuhiro, et al. , 24:1383-1406] and the measurement of simple flows such as low-velocity or dilute gas-solid/liquid-solid [Martin, et al. Powder Technol., 2005, 155:175-180]. Moreover, the contradictory limitation between the camera resolution and the size of the field of view also makes the number of effective discrete-phase particle images that can be obtained in one measurement by this method less, because it is not representative, it cannot fully summarize and reflect the specific discrete-phase particles Hydrodynamic behavior of aggregates or entire discrete phases. Therefore, its application range is greatly limited.

In summary, the existing gas-solid two-phase flow field measurement technology has poor real-time performance, it is difficult to take into account the imaging resolution and field of view of two-phase particles at the same time, and it is difficult to quantitatively measure the dynamic evolution of particle agglomeration. Therefore, there is an urgent need for a device and method for real-time measurement and display of the gas-solid two-phase flow field that can solve the above-mentioned problems.

Contents of the invention

The purpose of the present invention is to provide a real-time gas-solid two-phase flow field real-time measurement that has good real-time performance, can take into account the imaging resolution and field size of two-phase particles, and can quantitatively measure the dynamic evolution process of particle agglomeration systems and methods.

In order to achieve the purpose of the above invention, the present invention provides a real-time measurement system for gas-solid two-phase flow field, including:

At least one solid-phase camera for synchronously capturing images of solid-phase particle motion trajectories;

At least two gas-phase cameras for synchronously taking images of the trajectory of gas-phase tracer particles;

The computing device is used to perform data processing on the solid-phase particle motion trajectory image and the gas-phase tracer particle motion trajectory image respectively to obtain a solid-phase particle motion vector image and a gas-phase tracer particle motion vector image; and

The display device is used to synchronously output and real-time superimpose and display the solid-phase particle motion vector image and the gas-phase tracer particle motion vector image according to their respective fields of view.

Wherein, the gas-solid two-phase flow field real-time measurement system also includes a main synchronous controller and an auxiliary synchronous controller that respectively control the synchronization of the gas phase camera and the solid phase camera; the main synchronous controller is also used to control the auxiliary synchronous controller , so that the frame rate of the gas-phase camera is an integer multiple of the frame rate of the solid-phase camera.

In order to achieve the purpose of the above invention, the present invention provides a method for real-time measurement of gas-solid two-phase flow field, comprising the following steps:

Use fluorescent particles to mark the movement of the gas phase, and use high-energy laser sheet light to illuminate the solid-phase particles and fluorescent tracer particles in the flow field; use an auxiliary synchronization controller to control at least one low-resolution, high-frame transfer time and field of view Relatively large and mutually spliced digital high-speed cameras acquire motion trajectory images of solid-phase particles, using a master synchronous controller to control the above-mentioned auxiliary synchronous controller and at least two high-resolution, low frame transfer time and relatively small field of view and The digital high-speed cameras spliced with each other acquire the motion track images of gas-phase fluorescent tracer particles, so that the gas-solid two-phase camera can be triggered at the same reference moment, but the frame rate of the gas-phase camera is an integer multiple of the frame rate of the solid-phase camera;

Use the CPU (Central Processing Unit) serial method to adopt the global particle cross-correlation algorithm for the images acquired by all solid-phase cameras, that is, firstly perform binary processing on the solid-phase particle image, and then convert a certain solid-phase particle image in the previous image Phase particles are pattern-matched with all reference particles in the latter image to identify paired particles to calculate the motion vector of solid-phase particles;

Use GPU (Graphics Processing Unit) parallel method to adopt local gray level cross-correlation algorithm for all the images acquired by gas phase cameras, that is, first divide the gas phase tracer particle image in the previous image into small local interpretation areas, and then target a certain Interpretation area: Find the area with the largest gray similarity in the latter image to calculate the motion vector of the gas-phase fluorescent tracer particles;

Use the GPU parallel method to superimpose the solid-phase particle image and the gas-phase tracer particle motion vector image at the same time. If the solid-phase particle image overlaps with one or more gas-phase tracer particle images to a certain extent in the local interpretation area, delete it erroneous gas-phase tracer particle motion vectors resulting from the one or more local interpretation regions;

The gas-phase tracer particle motion vector image obtained by the same gas-phase camera after error vector elimination and the corresponding area of the solid-phase particle motion vector image at the same time are synchronously transmitted to different display screens of the same display array or at the same time by using GPU in parallel. The different display areas of a display are displayed online.

Define the maximum distance that can exist between particles in a particle aggregate according to the initial fluidization porosity of solid phase particles, calculate the distance between any two solid phase particles at any time and compare it with the above maximum distance value, less than All the solid phase particles at the maximum value are judged to belong to the same particle aggregate, and thus the dynamic evolution law of the particle aggregate is further quantitatively studied.

Compared with the prior art, the present invention has the following technical effects:

1. Expand the scope of application of image velocity measurement technology, and improve the efficiency of undisturbed experimental measurement of gas-solid two-phase flow;

2. Solved the contradiction between the field of view and resolution of the digital high-speed camera lens, and avoided the subsequent complicated phase separation calculation;

3. Improve the efficiency of gas-solid two-phase image processing, and realize the real-time measurement of gas-solid two-phase flow field;

4. The number of effective samples of solid phase particles that can be obtained in one measurement is increased, and it is possible to quantitatively study the dynamic evolution of particle aggregation.

Description of drawings

Hereinafter, embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, wherein:

Fig. 1 shows the structural representation of the gas-solid two-phase flow field real-time measurement method and device utilizing a solid-phase digital high-speed camera and two gas-phase digital high-speed cameras in an embodiment of the present invention;

Fig. 2 shows the flow chart of the multi-scale parallel real-time processing and display software system of the gas-solid two-phase particle trajectory image in the above embodiment.

Detailed ways

According to an embodiment of the present invention, a method for real-time measurement of a flow field of a gas-solid two-phase flow is provided. The method is realized based on the real-time measurement system of the gas-solid two-phase flow field shown in Fig. 1 . Referring to Fig. 1, the gas-solid two-phase flow field real-time measurement system in this embodiment includes: a high-energy laser sheet light source 1, a solid-phase digital high-speed camera 2 and corresponding auxiliary synchronous controller 5, two gas-phase digital High-speed cameras 3 and 4 and corresponding main synchronous controller 6, computer 7 loaded with one or more graphics processing units (GPU), and a display screen or display screen for real-time display of gas-solid two-phase motion vector images array8.

Among them, the solid-phase digital high-speed camera 2 is a low-resolution, high-frame transfer time digital high-speed camera for collecting motion trajectory images of solid-phase particles. Two gas-phase digital high-speed cameras 3 and 4 are high-resolution digital high-speed cameras with low frame transfer time for collecting gas-phase fluorescent tracer particle motion trajectory images. Described gas-phase digital high-speed camera 3 and 4 and solid-phase digital high-speed camera 2 all adopt lens translation method, are arranged in the both sides of target plane 9 respectively, so that the fields of view 10 and 11 of two gas-phase digital high-speed cameras 3 and 4 mutually splicing, and the common field of view between the cumulative field of view of the two and the field of view of the solid-phase digital high-speed camera 2 is as large as possible.

The computer 7 is equipped with a gas-solid two-phase particle trajectory image multi-scale parallel real-time processing and display software system, the software system is based on the Windows application platform and adopts VisualStudio 2008 programming, providing a good user expandable space.

The method for real-time measurement of the gas-solid two-phase flow field provided in this embodiment includes the following steps:

1. Use the corresponding digital high-speed camera to obtain the moving trajectory images of gas-solid two-phase particles respectively

Fluorescent coating treatment is performed on the gas-phase tracer particles, and the gas-phase digital high-speed cameras 3 and 4 are controlled by the main synchronous controller 6 to synchronously obtain moving track images of the gas-phase fluorescent tracer particles. The auxiliary synchronous controller 5 controls the solid-phase digital high-speed camera 2 to obtain the moving track image of the solid-phase particles. The main synchronous controller 6 triggers two gas phase digital high-speed cameras 3 and 4 at the same reference moment, and the main synchronous controller 6 controls the auxiliary synchronous controller 5, so that the auxiliary synchronous controller 5 is also at the reference moment (i.e. the main synchronous control The device 6 triggers the reference moment of two gas-phase digital high-speed cameras 3 and 4) triggers the solid-phase digital high-speed camera 2. And, by main synchronous controller 6 control auxiliary synchronous controller 5, make the exposure time interval of solid-phase digital high-speed camera 2 be the integral multiple of gas-phase digital high-speed camera 3 (or 4), i.e. gas-phase digital high-speed camera 3 (or 4) The frame rate is an integer multiple of the solid-phase digital high-speed camera 2.

2. Use different calculation methods to obtain the motion vector images of gas-solid two-phase particles

The above-mentioned gas-solid two-phase particle trajectory image is input into the computer 7 at the same time, and different processing methods and calculation methods are used to process the gas-solid two-phase particle trajectory image.

In the present embodiment, the described software system (as shown in Figure 2) of computer 7 utilizes CPU and adopts the global particle cross-correlation algorithm to process the solid-phase particle trajectory image captured by solid-phase digital high-speed camera 2 through serial processing . That is: using the CPU serial processing method, the solid-phase particle image is first binarized, and then a certain solid-phase particle in the previous image is cross-correlation pattern matched with all reference particles in the next image to identify Pair the particles, and then calculate the motion vector of the solid phase particles. The details of the global particle cross-correlation algorithm can refer to the records in the literature [Yamamoto, et al. J. of Flow Visualization and Image Processing, 1996, 3: 51-64], and will not be repeated here.

In this embodiment, the software system (as shown in FIG. 2 ) of the computer 7 utilizes the GPU to process the gas-phase fluorescent tracer particles captured by the gas-phase digital high-speed cameras 3 and 4 by means of parallel processing and local gray-scale cross-correlation algorithm. motion track images. That is: first divide the images acquired by two gas-phase digital high-speed cameras into multiple square or rectangular local interpretation areas, and assign a calculation thread in the GPU to each local interpretation area, and then use GPU parallel processing to target A local interpretation area in the previous image is searched for the area with the greatest gray similarity in the latter image to identify the paired local interpretation area, and then the motion vector representing the local interpretation area is calculated. For the details of the local gray level cross-correlation algorithm, please refer to the records in [Adrian.Annual Review of Fluid Mechanics, 1991, 23:261-304], and will not repeat them here.

3. Delete the wrong vector in the vector image of the gas-phase fluorescent tracer particle motion

The solid-phase particle image at the same time is superimposed with the gas-phase fluorescent tracer particle motion vector image to perform real-time error vector deletion processing.

According to the above, the local gray level cross-correlation algorithm actually obtains the average motion vector of all particles in the local interpretation area, which is expressed by the motion vector of the center point of the local interpretation area. Since there are actually no particles in the position occupied by the solid-phase particles in the gas-phase fluorescence tracer particle image, this gap makes the local interpretation area including this part of the area in the cross-correlation calculation may produce wrong motion vectors, and this possibility The property will increase with the increase of the ratio of the characteristic size of the solid phase particles to the characteristic size of the corresponding local interpretation area.

In this embodiment, each solid-phase particle is assigned a computing thread in the GPU, and then the solid-phase particle image and the gas-phase tracer particle motion vector image are superimposed at the same time through GPU parallel processing to perform error vector deletion deal with. Namely: preset a threshold value of an overlapping area or a threshold value of the area ratio of the overlapping area to the local interpretation area. When it is greater than the corresponding threshold, it can be judged that the two overlap, and the gas-phase fluorescent tracer particle motion vector generated by the local interpretation area is deleted as a wrong vector. In this embodiment, the position of the solid-phase particles obtained by the solid-phase camera is used to eliminate errors in the motion vector image of the gas-phase fluorescent tracer particles, and to make up for the deficiency of the local gray level cross-correlation algorithm.

4. Synchronous output and real-time display of gas-solid two-phase particle motion vector images

The motion vector image of the gas-solid two-phase particles after the false vector elimination is synchronously sent to the display screen or the display screen array 8 for online display.

In this step, a calculation thread in the GPU is allocated separately to the gas-phase tracer particle motion vector image obtained by each gas-phase camera after error vector elimination, and then processed in parallel with the GPU at the same time. The corresponding area of the particle motion vector image is synchronously sent to different display screens or different display areas of the display screen array or display screen 8 for online display. The gas-phase fluorescent tracer particle motion vector images acquired by different gas-phase cameras are spliced into one image, and are superimposed and displayed synchronously with the solid-phase particle motion vector images, so as to obtain the dynamic image of the gas-solid two-phase flow field in a large field of view. In this embodiment, the GPU parallel processing method is used to separately call and synchronously output the gas-phase fluorescent tracer particle motion vector images acquired by different gas-phase cameras and the solid-phase particle motion vector images or images in the images acquired by different solid-phase cameras. In a certain area, it solves the problem that a large amount of non-computing time is required for intensive reading and display of massive data, and improves the real-time performance of gas-solid two-phase flow measurement and display.

On the basis of the above dynamic images of the gas-solid two-phase flow field, the principle of the maximum distance between particles determined by the initial fluidization porosity of the solid phase particles is used to discriminate the particle agglomeration, which can be further analyzed with the gas-solid two-phase flow. The dynamics of the interaction and the changing behavior are quantitatively studied. Specifically, the maximum distance that can exist between particles in a particle aggregate is defined according to the initial fluidization porosity of solid phase particles, and the distance between any two solid phase particles at any time is calculated and compared with the above maximum distance value In comparison, all solid phase particles smaller than the maximum value are judged to belong to the same particle aggregate, and thus the dynamic evolution law of the particle aggregate is further quantitatively studied.

The beneficial technical effects that can be realized by the present invention include: (1) adopting the hardware design and software algorithm consistent with the multi-scale essence of gas-solid two-phase flow, expanding the application range of image velocity measurement technology and improving the speed of gas-solid two-phase flow; The efficiency of the disturbance experiment measurement; (2) Using fluorescent particles to mark the gas phase movement, and adopting special hardware design, the method of taking images of the two phases separately is applied to the gas-solid two-phase flow system to solve the problem of the field of view and resolution of the digital high-speed camera lens (3) Using different image calculation methods adapted to the nature of the image to perform multi-scale parallel real-time processing and display of the two-phase particle trajectory image and each local interpretation area of the gas phase, Improve the calculation efficiency to realize the online measurement of the gas-solid two-phase flow field; (4) The expansion of the measurable field of view increases the effective number of solid-phase particles that can be obtained in one measurement, thus providing a basis for quantitative research on the dynamic evolution of particle agglomerations Offer possible.

It should be noted that the present invention can also use multiple solid-phase digital high-speed cameras and more gas-phase digital high-speed cameras, and splice and superimpose according to the above description to obtain the gas-solid two-phase flow field in a larger field of view dynamic image. The method and device for real-time measurement of the gas-solid two-phase flow field in the above embodiment is only a specific embodiment of the present invention, and it should not be construed as any limitation on the scope of protection of this description. Moreover, those skilled in the art can understand that without departing from the spirit and principle of this embodiment, various equivalent changes, modifications and various improvements not described in this embodiment are within the scope of protection of this patent. within.

Claims (10)

1. A gas-solid two-phase flow field real-time measurement system, characterized in that, comprising: At least one solid-phase camera for synchronously capturing images of solid-phase particle motion trajectories; At least two gas-phase cameras for synchronously taking images of the trajectory of gas-phase tracer particles; The computing device is used to perform data processing on the solid-phase particle motion trajectory image and the gas-phase tracer particle motion trajectory image respectively to obtain a solid-phase particle motion vector image and a gas-phase tracer particle motion vector image; and The display device is used to synchronously output and real-time superimpose and display the solid-phase particle motion vector image and the gas-phase tracer particle motion vector image according to their respective fields of view. 2. The gas-solid two-phase flow field real-time measurement system according to claim 1, further comprising a main synchronous controller and an auxiliary synchronous controller which respectively control the synchronization of the gas-phase camera and the solid-phase camera; the main synchronous The controller is also used to control the auxiliary synchronous controller, so that the frame rate of the gas-phase camera is an integer multiple of the frame rate of the solid-phase camera. 3. A method for real-time measurement of a gas-solid two-phase flow field, characterized in that it comprises the following steps: 1) At least one solid-phase camera is used to simultaneously capture solid-phase particle trajectory images, and at least two gas-phase cameras are used to simultaneously capture gas-phase tracer particle trajectory images; 2) Perform data processing on the solid-phase particle trajectory image and the gas-phase tracer particle trajectory image respectively to obtain a solid-phase particle motion vector image and a gas-phase tracer particle motion vector image; 3) The solid-phase particle motion vector image and the gas-phase tracer particle motion vector image are synchronously output and real-time superimposed according to their respective fields of view. 4. The method for real-time measurement of gas-solid two-phase flow flow field according to claim 3, characterized in that, in the step 1), the frame rate of the gas-phase camera is an integer multiple of the frame rate of the solid-phase camera. 5. the gas-solid two-phase flow field real-time measurement method according to claim 4, is characterized in that, in described step 1), described solid-phase camera and gas-phase camera are digital high-speed cameras, and described solid-phase camera Compared with the gas-phase camera with higher resolution, lower frame transfer time and larger field of view, the total field of view of the solid-phase camera and the total field of view of the gas-phase camera include a common shooting area. 6. The gas-solid two-phase flow field real-time measurement method according to claim 3, characterized in that, in the step 2), the global particle cross-correlation algorithm is used to obtain the solid-phase particle motion vector image, and the local grayscale is used The cross-correlation algorithm obtains the motion vector image of the gas-phase tracer particles. 7. the gas-solid two-phase flow flow field real-time measurement method according to claim 3, is characterized in that, in described step 2), to solid-phase particle trajectory image, adopts global particle interaction based on CPU serial processing mode Correlation algorithm obtains solid-phase particle motion vector images; for gas-phase tracer particle motion trajectory images, the images acquired by all gas-phase cameras are divided into multiple local interpretation areas, and then local interpretation areas are simultaneously taken in parallel by GPU. The gray-level cross-correlation algorithm is used for data processing, and finally a complete gas-phase tracer particle motion vector image is obtained. 8. The gas-solid two-phase flow field real-time measurement method according to claim 7, characterized in that, step 21) is also included between the step 2) and step 3), 21) When the solid-phase particles in the solid-phase particle motion vector image overlap with a certain local interpretation area in the gas-phase tracer particle motion vector image, the motion vector generated by the local interpretation area is deleted as an error vector. 9. The gas-solid two-phase flow field real-time measurement method according to claim 3, characterized in that, in the step 3), the gas-phase tracer particle motion vector image is compared with the solid-state at the same time through GPU parallel processing. The corresponding area of the particle motion vector image is synchronously sent to different display screens of the display screen array or displayed in different display areas of the display screen in real time. 10. The gas-solid two-phase flow field real-time measurement method according to claim 3, further comprising step 4), 4) Determine the maximum distance that can exist between particles in a particle aggregate according to the initial fluidization porosity of the solid phase particles, calculate the distance between any two solid phase particles at the same time and compare it with the maximum distance, Get all the solid phase particles belonging to the same particle aggregate, and then study the dynamic evolution law of the particle aggregate.

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