A calculation experiment system and method for dust concentration in a pipeline under the action of a shock wave

Abstract

The application provides a kind of experimental system and method for calculating dust concentration in pipeline under the action of shock wave, and relates to the field of dust explosion prevention and control.The experimental system includes a vertical pipeline type dust explosion device, a PIV speed measurement system and a high-speed camera.In the application, dust is sprayed into the main body of the vertical pipeline from the powder spraying port through the powder spraying bin and passes through four observation windows in turn from bottom to top along the pipeline.When dust is not sprayed, the PIV laser is started, the laser side is vertically shot into the main body of the vertical pipeline, the PIV camera and the high-speed camera are synchronously shot, the PIV camera collects the inflow and outflow speed of dust particles at the third observation window, the high-speed camera records the visible duration of dust particles, and the real-time dust mass and real-time dust concentration are calculated according to the mass conservation law combined with the size of the main body of the vertical pipeline.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dust explosion prevention and control, and particularly relates to a system and method for calculating dust concentration in a pipeline under the action of a shock wave. BACKGROUND

[0002] Dust explosion is a major safety hazard in many industrial fields such as coal, grain, metallurgy, and chemical industry. It not only has extremely strong explosive power, but also easily causes large-scale casualties and huge property losses. As one of the core parameters that determine whether a dust cloud concentration can occur and the severity of an explosion, accurate measurement of the dust cloud concentration is crucial. Especially in the explosion process, when the dust cloud is in a dynamic state under the action of a shock wave or external force, accurate measurement of the concentration is a key scientific basis and core technical prerequisite for understanding the mechanism of dust explosion, evaluating the risk level of explosion, and designing effective explosion relief and suppression systems.

[0003] Traditional dust cloud concentration measurement methods can be mainly divided into two categories: contact type and non-contact type. However, when applied in a transient and strong disturbance flow field under the action of a shock wave, both types of methods have significant limitations. The contact sampling method, which is based on direct weighing as the core principle, has a simple operation logic and intuitive measurement results, but it is an offline and post-measurement method. Since it cannot capture the transient characteristics of the dust cloud concentration changing with time and space during the explosion process, it basically has no practical value in dynamic explosion process research. The non-contact optical method, which is the most widely used technical method, is represented by the light attenuation method. It measures the light intensity attenuation of a laser beam passing through a dust cloud to inversely calculate the average concentration of the dust cloud. This method has a relatively simple device, but it only obtains the linear average concentration along the laser beam path and cannot measure the distribution of the two-dimensional or three-dimensional concentration field. Moreover, in the case of high concentration of dust, the multiple scattering effect will greatly amplify the measurement error, resulting in a significant reduction in the reliability of the results.

[0004] In recent years, the Particle Image Velocimetry (PIV) technology has gradually become a standard tool for non-contact flow velocity field measurement in fluid mechanics. Its technical principle is to use the scattering characteristics of tracer particles on laser sheet light, record the scattering images of particles in consecutive two or more frames of flow field by a high-speed camera, and finally obtain the instantaneous two-dimensional or three-dimensional velocity vector distribution of the flow field by cross-correlation algorithm calculation. The PIV particle image velocimetry system naturally has the advantages of high spatiotemporal resolution, full-field measurement, and non-invasive, which is very suitable for the study of extreme transient processes such as explosion and combustion.

[0005] Therefore, how to realize accurate, full-field, and quantitative concentration measurement of real-time dust concentration calculation has become a problem to be solved. SUMMARY

[0006] The embodiment of the present application provides a dust concentration calculation system and method in a pipeline under the action of a shock wave, so as to solve the technical problem that the prior art cannot accurately, fully and quantitatively measure the concentration of a transient explosion field.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the embodiment of the present application is:

[0008] In the first aspect, the present application provides a dust concentration calculation experimental system in a pipeline under the action of a shock wave, comprising a vertical pipeline type dust explosion device, a PIV velocity measurement system and a high-speed camera, wherein the vertical pipeline type dust explosion device at least comprises a vertical pipeline main body, a dust spraying system and a data analysis module; three of the four surfaces of the vertical pipeline main body are sequentially provided with four observation windows from bottom to top; the dust spraying system is used for spraying dust particles upward from the bottom of the vertical pipeline main body under a preset working condition;

[0009] The PIV velocity measurement system comprises a PIV laser and a PIV camera; the laser output by the PIV laser is vertically incident into the vertical pipeline main body through the middle surface of the three surfaces; the high-speed camera and the PIV camera are respectively opposite to the left surface and the right surface adjacent to the middle surface, and the PIV camera and the high-speed camera are arranged on the same horizontal plane;

[0010] The high-speed camera is used for photographing the state in the entire vertical pipeline main body and recording the visible duration of the dust particles passing through the third observation window from bottom to top on the left surface;

[0011] The PIV velocity measurement system is used for obtaining the inflow velocity and outflow velocity of the particles passing through the third observation window;

[0012] The data analysis module is used for receiving the respective data of the high-speed camera and the PIV velocity measurement system, and calculating the real-time dust mass and real-time dust concentration passing through the third observation window based on the visible duration, the inflow velocity and the outflow velocity of the particles, in combination with the size of the vertical pipeline main body and the density of the dust particles, and by using the law of conservation of mass.

[0013] In some embodiments, the data analysis module is further used for optimizing and adjusting the related parameters of the PIV velocity measurement system according to the dust spraying pressure of the dust spraying system, including the setting of the shooting position, focal length and aperture of the PIV camera, and the adjustment of the laser intensity and beam thickness; and the optimal time interval of the adjacent two lasers is determined through repeated tests.

[0014] In some embodiments, the smaller the dust spraying pressure is, the larger the optimal time interval is and the higher the frame rate of the high-speed camera is; when the dust spraying pressure is 1.2 MPa, the optimal time interval is 2 Hz.

[0015] In some embodiments, the material of the four observation windows on the three faces of the vertical pipeline body is quartz glass, and the shape of each observation window is a circle with a diameter of 110 mm.

[0016] In some embodiments, the vertical pipeline dust explosion device further comprises a gas distribution system for gas distribution by Dalton partial pressure method, and the gas distribution error is controlled within 0.1%.

[0017] In some embodiments, the PIV velocity measurement system further comprises a synchronization controller for synchronizing the trigger time of the PIV camera and the high-speed camera and the data acquisition start time, so that the PIV camera and the high-speed camera perform image data acquisition at the same time point.

[0018] In some embodiments, the visible duration is calculated by: obtaining the complete image sequence and the total frame number collected by the high-speed camera per unit time; performing frame-by-frame analysis on the complete image sequence to locate the starting frame corresponding to the appearance of the first dust particle in the third observation window and the ending frame corresponding to the complete departure of the first dust particle from the third observation window; determining the target frame number between the starting frame and the ending frame; and determining the visible duration based on the total frame number and the target frame number.

[0019] In a second aspect, the present application provides a method for calculating dust concentration in a pipeline under the action of a shock wave, which is applied to the experimental system of any one of the first aspect, and comprises:

[0020] initializing the vertical pipeline dust explosion device, the PIV velocity measurement system and the high-speed camera;

[0021] After the PIV velocity measurement system starts to operate, the dust injection system injects dust particles upward from the bottom of the vertical pipeline body through the dust injection bin, and the PIV camera and the high-speed camera simultaneously perform shooting;

[0022] The high-speed camera shoots the state in the entire vertical pipeline body from the left side face sequentially provided with four observation windows from bottom to top, and records the visible duration of the dust particles passing through the third observation window from bottom to top on the left side face;

[0023] The PIV velocity measurement system obtains the particle inflow velocity and the particle outflow velocity passing through the third observation window;

[0024] The data analysis module calculates real-time dust mass and real-time dust concentration passing through the third observation window based on the visible time length, the particle inflow velocity and the particle outflow velocity, in combination with the size of the vertical pipeline body and the dust particle density, by using the law of conservation of mass.

[0025] In some embodiments, the size of the vertical pipeline body includes a pipeline cross-sectional area of the vertical pipeline body and a height of the third observation window; and the calculation of the real-time dust mass and the real-time dust concentration passing through the third observation window based on the visible time length, the particle inflow velocity and the particle outflow velocity, in combination with the size of the vertical pipeline body and the dust particle density, by using the law of conservation of mass, includes:

[0026] determining a volume of a corresponding calculation region of the third observation window according to the pipeline cross-sectional area and the height; determining an inlet dust mass flow rate flowing through the inlet within a preset time according to the dust inflow velocity at different positions of the at least three inlets, the dust particle density and the pipeline cross-sectional area; determining an outlet dust mass flow rate flowing through the outlet within the preset time according to the dust outflow velocity at different positions of the at least three outlets, the dust particle density and the pipeline cross-sectional area; determining a mass change rate according to the inlet dust mass flow rate and the outlet dust mass flow rate; determining the real-time dust mass passing through the third observation window based on the mass change rate and the visible time length; and determining the real-time dust concentration passing through the third observation window based on the real-time dust mass and the volume.

[0027] In some embodiments, the real-time dust mass passing through the third observation window is calculated according to the following formula: ; wherein, is the dust particle density, is the pipeline cross-sectional area, is the visible time length, , , is the three dust inflow velocities flowing into the third observation window, , , is the three dust outflow velocities flowing out of the third observation window.

[0028] The real-time dust concentration passing through the third observation window is calculated according to the following formula: ; wherein, represents the dust concentration, represents the volume of the calculation region.

[0029] The technical scheme provided by the embodiments of the present application has at least the following beneficial effects:

[0030] The application provides a dust concentration calculation experiment system and method in a pipeline under the action of an impact wave, which integrates a vertical pipeline type dust explosion device, a PIV speed measurement system and a high-speed camera, realizes dust injection, particle capture and data recording integration, and has four observation windows in the vertical pipeline, and the PIV camera and the high-speed camera are arranged on the adjacent sides of the laser and are coplanar, which not only ensures that the whole dust movement process is visible, but also ensures that the PIV speed measurement system accurately collects data, reduces experimental interference, and improves experimental stability and repeatability; the PIV speed measurement system collects the inflow / outflow speed of particles in the third observation window, and the high-speed camera synchronously records the visible duration of the dust passing through the window, and the data of the two are time-synchronized and spatially corresponding, which avoids the defects that the traditional sampling cannot obtain the speed and time parameters in real time; based on the law of conservation of mass, the dust inflow speed, the dust outflow speed, the visible duration, the pipeline size and the dust particle density measured by the PIV camera and the high-speed camera are combined, and the real-time dust mass and the real-time dust concentration are derived through a data analysis module, which overcomes the problems of the traditional method depending on empirical formula and large calculation error, realizes real-time and quantitative calculation of the dust concentration in the pipeline, and has high data reliability. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the overall structure design drawing of the dust concentration calculation experiment system in a pipeline under the action of an impact wave provided by the embodiment of the application;

[0032] Figure 2 is the related size parameter schematic diagram of the calculation area in the vertical pipeline main body provided by the embodiment of the application;

[0033] Figure 3 is the flowchart of the dust concentration calculation method under the action of an impact wave provided by the embodiment of the application;

[0034] Figure 4 is the particle original drawing, the speed field and the speed cloud diagram of the third observation window provided by the embodiment of the application;

[0035] The drawings show that: 1 is a vertical pipeline type dust explosion device; 2 is a high-speed camera; 3 is a PIV speed measurement system; 4 is a vertical pipeline main body; 5 is a dust injection system; 6 is a data analysis module; 7 is a PIV laser; 8 is a PIV camera; 9 is a gas distribution system; 10 is a synchronous controller; 11 is a dust injection bin; 12 is a dust injection port. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with reference to the drawings, and the described embodiments should not be regarded as limiting the application, and all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0037] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" can be the same subset or different subsets as each other and can be combined with each other, without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present application belong. The terms used in the embodiments of the present application are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0038] The existing dust concentration measurement method depends on offline sampling analysis or single online monitoring device, which has two key defects: one is that offline sampling cannot capture the dynamic change process of dust concentration under the action of shock wave, and the time resolution is low; the other is that single monitoring device is difficult to obtain the motion speed and concentration data of dust at the same time, and is easy to produce measurement error due to flow field disturbance, which cannot meet the high-precision experimental demand.

[0039] Figure 1 The present application provides a kind of dust concentration calculation experimental system in pipeline under the action of shock wave, as shown in Figure Figure 1 It includes vertical pipeline type dust explosion device 1, PIV speed measurement system 3 and high-speed camera 2, vertical pipeline type dust explosion device at least includes vertical pipeline main body 4, powder spraying system 5, data analysis module 6;Three of the four faces of vertical pipeline main body are sequentially provided with four observation windows from bottom to top;Powder spraying system 5 is used to spray dust particles upward from the bottom of the vertical pipeline main body under the preset working condition;

[0040] PIV speed measurement system 3 includes PIV laser 7, PIV camera 8;The laser output by PIV laser 7 is vertically injected into vertical pipeline main body 4 through the middle of the three faces;High-speed camera 2 and PIV camera 8 are respectively opposite to the left side and right side adjacent to the middle, and PIV camera 8 and high-speed camera 2 are arranged on the same horizontal plane;

[0041] High-speed camera 2 is used to shoot the state of the whole vertical pipeline main body 4 and record the visible duration of dust particles passing through the third observation window from bottom to top on the left side;

[0042] PIV speed measurement system 3 is used to obtain the inflow velocity and outflow velocity of particles passing through the third observation window;

[0043] Data analysis module 6 is used to receive the data of high-speed camera 2 and PIV speed measurement system 3 respectively, based on the visible duration, particle inflow velocity and particle outflow velocity, combined with the size of vertical pipeline main body 4 and the density of dust particles, the real-time dust mass and real-time dust concentration passing through the third observation window are calculated by using the law of conservation of mass.

[0044] In the present application, the vertical pipe body functions to provide a closed space for dust movement and simulate the scenario of dust being subjected to the action of a shock wave in the pipe. Figure 2 As shown, the vertical pipe body is provided with a structure design of three observation windows on three of the four faces, which enables multi-device collaborative observation. Among them, the three faces are each provided with four observation windows from bottom to top, and the third observation window serves as the core measurement area. This area is optimized in terms of flow field stability under the action of a shock wave through preliminary fluid mechanics simulation and pre-experiment verification, and can effectively avoid uneven distribution of dust at both ends of the pipe due to airflow, thereby improving the accuracy of measurement data.

[0045] In some embodiments, the material of the four observation windows on the three faces of the vertical pipe body 4 is quartz glass, and the shape of each observation window is circular with a diameter of 110 mm.

[0046] In this embodiment, when the vertical pipe dust explosion device is ready but the dust has not been sprayed, the PIV velocity measurement system starts to operate, the laser is vertically shot from the side into the vertical pipe body, and at the same time, the dust in the dust spraying bin is manually sprayed into the vertical pipe body, and the two faces adjacent to the laser are photographed by the PIV camera and the high-speed camera.

[0047] Here, the preset working conditions include parameters such as dust spraying pressure, dust spraying amount, and dust particle size distribution. By controlling these parameters, the pipe dust conveying state under different industrial scenarios can be simulated, so that the experimental conditions are closer to the actual application scenario. In addition, the design of spraying dust upward from the dust spraying port 12 of the dust spraying bin 11 under the dust spraying pressure ensures that the dust particles can pass through each observation window in turn under the premise of meeting the condition that the dust in the industrial pipe often flows in the vertical direction, thereby providing a stable particle movement path for subsequent data acquisition of the high-speed camera and the PIV velocity measurement system.

[0048] In the present application, the PIV output laser is vertically shot into the vertical pipe body through the middle one of the three faces, with the purpose of forming a uniform laser sheet region in the pipe, which covers the third observation window. When the dust particles pass through the laser sheet, they will scatter the laser, providing clear particle imaging signals for the PIV camera and the high-speed camera. The vertical shooting method can avoid the offset of the laser sheet region caused by oblique incidence, ensuring the clarity and positional accuracy of particle imaging.

[0049] In the present application, the PIV camera 8 and the high-speed camera 2 are respectively opposite to the left side and the right side adjacent to the middle surface, and are arranged in the same horizontal plane, which can ensure that the shooting fields of view of the two cameras can accurately cover the third observation window, and avoid the misjudgment of the particle position caused by the angle deviation; at the same time, the imaging planes of the two devices are coaxial with the laser sheet light area, which ensures that the particle velocity direction measured by the PIV speed measurement system is consistent with the particle running direction captured by the high-speed camera.

[0050] In some embodiments, the data analysis module 6 is also used for optimizing and adjusting the related parameters of the PIV speed measurement system according to the powder spraying pressure of the powder spraying system, including the shooting position, focal length, aperture setting of the PIV camera, and the adjustment of the laser intensity and the beam thickness; and the optimal time interval of the adjacent two lasers is determined through repeated tests.

[0051] In the present application, the PIV speed measurement system parameters are dynamically adjusted by the data analysis module with the powder spraying pressure as the input variable, so that the parameters always match the particle motion characteristics under the current pressure, and the measurement accuracy of the PIV speed measurement system on the particle velocity is ensured.

[0052] In some embodiments, the smaller the powder spraying pressure is, the larger the optimal time interval is and the higher the frame rate of the high-speed camera is; when the powder spraying pressure is 1.2 MPa, the optimal time interval is 2 Hz.

[0053] In the present application, the smaller the powder spraying pressure is, the slower the particle motion is, and the smaller the position change of the particle in the image per unit time is; if the frame rate of the camera is too low, the difference between the particle positions of adjacent frames is small, and the visual illusion of the particle being stationary is easy to appear, so that the complete process of the particle from entering the window to leaving the window cannot be accurately captured, resulting in a large error in the calculation of the visible time. Therefore, it is necessary to increase the frame rate and increase the image sampling density to ensure that each frame can record the small displacement of the particle, so the smaller the powder spraying pressure is, the higher the frame rate of the high-speed camera is. For example, in practical application, the powder spraying pressure is 1.2 MPa; when the powder spraying pressure is adjusted to 1 MPa, the inflow and outflow speed of the dust particles will slow down, so the laser interval time can be appropriately increased and the frame number of the high-speed camera can be increased to ensure that the captured results contain more particles.

[0054] In some embodiments, the vertical pipeline dust explosion device 1 further comprises a gas distribution system 9 for distributing gas by the Dalton partial pressure method, and the gas distribution error is controlled within 0.1%.

[0055] In some embodiments, the PIV speed measurement system 3 further comprises a synchronous controller 10 for controlling the trigger time and the data acquisition start time of the PIV camera 8 and the high-speed camera 2 to be synchronized, so that the PIV camera 8 and the high-speed camera 2 perform image data acquisition at the same time point.

[0056] In the present application, the trigger time of the PIV camera and the high-speed camera, and the data acquisition start time are completely synchronized, ensuring that the image data collected by the two types of devices correspond to the particle motion process of the same time dimension. Here, the combination of the PIV camera and the high-speed camera is not simply superimposed, but through precise time synchronization and data fusion, real-time measurement of dust concentration is realized. The selection of the above-mentioned third observation window and the cooperative work of PIV speed measurement and high-speed camera timing are the unique innovations of the present application in the technical scheme.

[0057] In some embodiments, the visible duration is calculated by: obtaining the complete image sequence and the total frame number collected by the high-speed camera per unit time; performing frame-by-frame analysis on the complete image sequence to locate the starting frame corresponding to the appearance of the first dust particle in the third observation window, and the termination frame corresponding to the complete departure of the first dust particle from the third observation window; determining the target frame number between the starting frame and the termination frame; and determining the visible duration based on the total frame number and the target frame number.

[0058] The present application provides an experimental system and method for calculating dust concentration in a pipeline under the action of a shock wave. By integrating a vertical pipeline dust explosion device, a PIV speed measurement system and a high-speed camera, dust injection, particle capture and data recording are integrated, and real-time dust concentration during transient processes such as shock wave can be calculated through the experimental system. The vertical pipeline is provided with four observation windows, and the PIV camera and the high-speed camera are arranged adjacent to each other on the same plane, which not only ensures that the entire dust movement is visible, but also ensures that the PIV speed measurement system accurately collects data, reduces experimental interference, and improves experimental stability and repeatability. The PIV speed measurement system collects the particle inflow / outflow speed in the third observation window, and the high-speed camera synchronously records the visible duration of the dust passing through the window. The data of the two are time-synchronized and spatially corresponding, avoiding the defects of traditional sampling that cannot obtain speed and time parameters in real time. Based on the law of conservation of mass, combined with the measured particle inflow speed, particle outflow speed, visible duration, pipeline size and dust particle density by the PIV camera and the high-speed camera, the real-time dust mass and real-time dust concentration are derived through the data analysis module, overcoming the problem of large calculation error of traditional methods relying on empirical formula, realizing real-time and quantitative calculation of dust concentration in the pipeline, and the data has high reliability. The present application can measure the dust concentration in real time, providing key data support for dust explosion prevention and control.

[0059] The present application provides a method for calculating dust concentration in a pipeline under the action of a shock wave, as shown in Figure 3 , Figure 3 is a flowchart of a method for calculating dust concentration in a pipeline under the action of a shock wave provided by the present application, which will be described in combination with the steps shown in Figure 3 .

[0060] Step S310: Initialize the vertical pipe dust explosion device, PIV speed measurement system, and high-speed camera.

[0061] In some embodiments, initializing a vertical pipe-type dust explosion device may include checking the pipe's sealing, cleaning residual impurities inside the pipe, and confirming the pipe's verticality; initializing a PIV velocimetry system may include calibrating the PIV camera's shooting angle to align it with a third observation window; debugging the image analysis algorithm to ensure the accuracy of inflow and outflow velocity calculations; verifying the identifiability of tracer particles; initializing a high-speed camera may include adjusting the frame rate to match the dust velocity, ensuring the complete particle motion process can be captured, and calibrating the shooting position, etc.

[0062] In this invention, initializing the vertical pipe dust explosion device, PIV velocity measurement system, and high-speed camera ensures that all experimental equipment is in a stable initial state, eliminating the influence of equipment errors on experimental results.

[0063] Step 320: After the PIV speed measurement system starts operating, the powder spraying system sprays dust particles upward from the bottom of the vertical pipe body through the powder spraying chamber, and the PIV camera and the high-speed camera simultaneously take pictures.

[0064] In this invention, the powder spraying system, used in experiments as a power system to deliver dust particles into a vertical pipe, includes a powder spraying chamber. The powder spraying chamber stores the dust particles to be tested; it is a storage container for the dust particles, and the initial powder spraying amount can be adjusted by controlling the release rate to ensure the stability of the experimental dust supply.

[0065] Step 330: The high-speed camera takes pictures of the entire vertical pipe body from the bottom up on the left side with four observation windows, and records the visible time of the dust particles passing through the third observation window from the bottom up on the left side.

[0066] In some embodiments, the visible duration refers to the time it takes for dust particles to enter the third observation window and leave the window as recorded by the high-speed camera, reflecting the residence time of the dust particles within the window.

[0067] In this invention, the selection of the third observation window from bottom to top along the main body of the vertical pipe for measurement is not arbitrary, but based on in-depth research into the stability of the flow field after the impact wave. Specifically, the location of this specific third observation window can capture the most representative dust flow, thus more accurately reflecting the dust concentration distribution throughout the entire vertical pipe. This selection is an experimentally verified optimal solution, rather than a simple conventional choice. Measurements through the third observation window can more comprehensively capture the flow of dust particles within the pipe, providing richer data for accurately calculating real-time dust concentration.

[0068] Step 340, obtaining the particle inflow velocity and the particle outflow velocity through the third observation window by the PIV velocity measurement system.

[0069] In some embodiments, the particle inflow velocity is the moving velocity of the dust particles entering the third observation window upward along the pipeline measured by the PIV velocity measurement system. The particle outflow velocity is the moving velocity of the dust particles leaving the third observation window upward along the pipeline measured by the PIV velocity measurement system.

[0070] In the present application, the PIV velocity measurement system can calculate the displacement of the particles in adjacent frames by shooting continuous images of the dust particles in the window, and convert the velocity by combining the frame rate; identify the displacement data of the particle inflow velocity and the particle outflow velocity respectively.

[0071] Step 350, calculating the real-time dust mass and the real-time dust concentration through the third observation window by the data analysis module based on the visual duration, the particle inflow velocity and the particle outflow velocity, combining the size of the vertical pipeline body and the dust particle density, and using the law of conservation of mass.

[0072] In some embodiments, the size of the vertical pipeline body includes the pipeline cross-sectional area of the vertical pipeline body and the height of the third observation window; the above step S350 can further include the following contents:

[0073] According to the pipeline cross-sectional area and the height, determine the volume of the calculation region corresponding to the third observation window. According to the dust inflow velocity at at least three different positions of the inlet, the dust particle density, and the pipeline cross-sectional area, determine the inlet dust mass flow rate flowing through the inlet within a preset time. According to the dust outflow velocity at at least three different positions of the outlet, the dust particle density, and the pipeline cross-sectional area, determine the outlet dust mass flow rate flowing through the outlet within a preset time. According to the inlet dust mass flow rate and the outlet dust mass flow rate, determine the mass change rate. Based on the mass change rate and the visual duration, determine the real-time dust mass through the third observation window. Based on the real-time dust mass and the volume, determine the real-time dust concentration through the third observation window.

[0074] In some embodiments, the real-time dust mass through the third observation window is calculated according to the following formula:

[0075] ;

[0076] wherein, is the dust particle density, is the pipeline cross-sectional area, is the visual duration, , , three dust inflow velocities of the third observation window, , , three dust outflow velocities of the third observation window;

[0077] The real-time dust concentration passing through the third observation window is calculated according to the following formula:

[0078] ;

[0079] In the formula, represents the real-time dust concentration, represents the volume of the calculation region.

[0080] Next, an exemplary application of the embodiment of the present application in an actual application scenario will be described.

[0081] In this experiment, 250-mesh magnesium powder is used as tracer dust, which is sprayed into the pipeline from the powder spraying port of the powder spraying bin below the vertical pipeline body. In this way, the dust particles will pass through the four observation windows from bottom to top, so that the PIV velocity measurement system and the high-speed camera can capture the dust particles. When the dust particles have not been sprayed, the PIV velocity measurement system starts to work, and the laser is vertically shot from the side into the vertical pipeline. At the same time, the dust in the powder spraying bin is manually sprayed into the vertical pipeline, and the two sides adjacent to the laser are respectively shot by the PIV camera and the high-speed camera. Among them, the PIV camera only shoots the particle movement of the third observation window from bottom to top, while the high-speed camera can shoot the entire vertical pipeline. Here, the particle movement flow field of the third observation window can be obtained by the PIV velocity measurement system, so as to determine the particle inflow velocity and the particle outflow velocity of the third observation window under ideal state. Then, according to the visible duration of the first dust particle in the third observation window obtained by the high-speed camera, combined with the size of the vertical pipeline body, the real-time dust mass and the real-time dust concentration passing through the third observation window in this period of time are estimated by using the law of conservation of mass.

[0082] The embodiment provides a dust concentration calculation experiment system in a pipeline under the action of a shock wave. In the process of building the experiment system, it is necessary to ensure that the laser of the PIV velocity measurement system is aligned with the middle one of the three window surfaces of the vertical pipeline body, and the PIV camera and the high-speed camera are aligned with the two sides of the three window surfaces, that is, to ensure that the laser of the PIV velocity measurement system and the camera are perpendicular, and the PIV camera and the high-speed camera are on the same surface.

[0083] In the embodiment, the specific powder spraying operation is as follows: first, the prepared magnesium powder dust particles are put into the powder spraying bin below the vertical pipeline type dust explosion device, the gas distribution system controls the powder spraying bin to be pressurized, the dust particles are sprayed into the pipeline from the powder spraying port through the powder spraying bin, and the powder particles pass through the four observation windows from bottom to top in sequence, so that the PIV speed measurement system and the high-speed camera can capture the dust particles. Based on this, in the embodiment, the PIV camera only shoots the particle movement of the third observation window from bottom to top, because through fluid mechanics simulation and experimental verification, the flow field of the third observation window under the action of the shock wave is most stable, so as to more accurately reflect the dust concentration distribution in the entire pipeline and provide more abundant data for accurately calculating the dust concentration. The high-speed camera can shoot the entire vertical pipeline, and the high-speed camera can capture the time from the appearance of the first particle in the third observation window to the exit of the particle from the window, that is, the visible duration in the above embodiment.

[0084] In the embodiment, the visible duration t from the appearance of the first dust particle in the third observation window to the exit of the particle from the window can be obtained by the high-speed camera, the high-speed camera is set to shoot 10,000 frames per 1 s, and through frame-by-frame playing, it is found that a total of 250 frames appear from the appearance of the first dust particle to the exit of the particle from the window, which is converted into time, that is, the visible duration t=25 ms=0.025 s.

[0085] In the embodiment, the related parameters of the PIV speed measurement system can also be optimized and adjusted according to the powder spraying pressure of the powder spraying system, including the shooting position, focal length, aperture setting of the PIV camera, and the adjustment of laser intensity and beam thickness; and the optimal time interval of the two adjacent lasers is determined through repeated experiments to ensure that the camera of the PIV speed measurement system can capture the dust particles in the pipeline. Through multiple experiments, it is found that the interval time of the two lasers of the PIV speed measurement system is set to 2 Hz, and most of the dust particles can be captured, that is, the shooting effect is good. In the embodiment, the powder spraying pressure is 1.2 MPa (through multiple experiments, the 20 g of 250 mesh magnesium powder sprayed at the powder spraying pressure of 1.2 MPa is more evenly distributed in the pipeline). In the actual application process, the detailed parameters of the PIV speed measurement system can be adjusted according to the powder spraying pressure. Assuming that the powder spraying pressure in the experiment is 1.2 MPa, if the powder spraying pressure is adjusted to 1 MPa, the speed of the dust will slow down, so the laser interval time can be appropriately increased and the frame number of the high-speed camera can be increased to ensure that the shot result contains more particles. That is, the method can appropriately adjust the parameter setting according to the test working condition, which will be suitable for more working conditions, including different dusts, different particle sizes, etc.

[0086] In the present application, the visible duration t can be obtained through experiments , and the particle speed flowing in and out of the third observation window under the ideal state obtained by the PIV speed measurement system and and obtain the experimentally known data including the pipe cross-sectional area , the height h of the third window, the density of the 250-mesh magnesium powder .

[0087] In determining the precise synchronization and data fusion of the PIV velocity measurement system and the high-speed camera, in the ideal state, it is assumed that the change of the moving speed of each dust particle in the pipe is consistent, that is, the dust inflow speed of the first dust particle appearing at the entrance of the third observation window is the same as the dust inflow speed of any dust particle at the entrance (the same for the outlet). Thus, the particle speed of the third observation window at any time in the PIV can be ensured to be the same as the speed of the first particle in the third window shot by the high-speed camera at the same position, which ensures the data fusion of the PIV velocity measurement system and the high-speed camera.

[0088] In the present application, the real-time dust mass and the real-time dust concentration are calculated based on the mass conservation law, and the specific calculation and derivation process is as follows:

[0089] When the dust particles move in the flow field, the concentration distribution thereof follows the mass conservation law, and the expressions of the dust inflow mass flow rate and the dust outflow mass flow rate can be obtained.

[0090] The expressions of the dust inflow mass flow rate and the dust outflow mass flow rate are respectively:

[0091] ;

[0092] ;

[0093] In the formula, represents the dust inflow mass flow rate, represents the dust outflow mass flow rate; , , respectively represent the dust mass flow rates at different positions of the inlet; , , respectively represent the dust mass flow rates at different positions of the outlet;

[0094] According to the expressions of the outlet mass flow rate and the inlet mass flow rate, the dust mass change rate equation based on the mass conservation is determined; the dust mass change rate equation represents that the total mass change rate of the dust particles is equal to the dust outflow mass flow rate minus the dust inflow mass flow rate.

[0095] The dust mass change rate equation is:

[0096] ;

[0097] In the formula, represents the total mass change rate of the dust particles;

[0098] Based on the particle inflow / outflow velocity, the dust particle density, the height, the pipe cross-sectional area and the visible time length, an inflow and outflow dust mass flow continuity equation is constructed;

[0099] The inflow and outflow dust mass flow continuity equations are respectively:

[0100]

[0101]

[0102] In the formula, represents the visible time length; represents the dust particle density; represents the pipe cross-sectional area; represents the height; represents the particle inflow velocity, represents the volume of the calculation region; represents the dust mass in the ideal state;

[0103] According to the inflow and outflow dust mass flow continuity equations, the dust mass change rate equation is rewritten to obtain a rewritten dust mass change rate equation; the rewritten dust mass change rate equation is:

[0104]

[0105] Under a preset working condition, the rewritten dust mass change rate equation is rewritten again according to the dust mass change rate definition formula to obtain a real-time dust mass equation; the real-time dust mass equation is:

[0106]

[0107] According to the real-time dust mass equation, a real-time dust concentration is calculated;

[0108] The real-time dust concentration is: ; in the formula, represents the real-time dust concentration, represents the volume of the calculation region.

[0109] ​​​​The application applies the mass conservation law to calculate the mass flow rate and average concentration in the flow field to the calculation of the dust concentration in the pipeline under the action of the shock wave, and provides the exclusive parameter design (such as window selection and laser interval 2Hz) of the transient scene, detailed calculation formula and implementation mode. The specific application and implementation mode are lacked in the prior art. The calculation formula of the application not only considers the dust inflow / outflow speed and visible time length, but also combines the specific size of the pipeline (such as the cross-sectional area, window height and the like), so that the real-time dust concentration can be more accurately calculated.

[0110] The embodiment also provides a specific experiment, and specific contents are as follows.

[0111] In the experiment, the size parameters of the vertical pipeline body are determined as follows: as shown in the figure, Figure 2 the window height h of the calculation area corresponding to the third observation window is 11cm; the pipeline cross section is a square, the side length d is 13.5cm, that is, the pipeline cross-sectional area A = d 2 = 13.5x13.5 (cm 2 ) = 0.135x0.135 (m 2 ) = 0.018225 m 2 ; the volume V of the calculation area is V = Ah = 0.018225x0.11 (m 3 ) ≈ 0.02 m 3 ; the dust particle density corresponding to the 250-mesh magnesium powder is ρ = 1.74g / cm 3 = 1740kg / m 3 ; the visible time length t is t = 25ms = 0.025s.

[0112] According to the above analysis and simple calculation, ρ = 1740kg / m, A = 0.018225m 2 , t = 0.025s, and the multiple dust inflow and outflow speeds are obtained according to Figure 4 , so that v in1 = 0.297391m / s, v in2 = 0.046973m / s, v in 3 = 0.315275m / s, v out1 = 0.305324m / s, v out 2 = 0.050865m / s, v out 3 = 0.316811m / s, and M 总 ≈ 0.00353 = 3.53g are obtained by substituting the values respectively.

[0113] Therefore, the real-time dust mass passing through the third observation window in the time from the first dust particle appearing in the third observation window to its leaving the window is about 3.53g, and the real-time dust concentration calculated is c=3.53 / 0.02=176.5g / m 3 .

[0114] In the experiment, the actual dust particles put into the powder bin are 20g, and the real-time dust concentration in the vertical pipeline is 1000g / m 3 Therefore, the real-time dust concentration of the third observation window calculated by the method of the present application is 176.5g / m 3 which is in line with the actual logic, that is, the calculation method has certain accuracy and reliability.

[0115] The present application describes the specific parameters and details of the experimental device, such as the cross-sectional area of the pipeline, the height of the window, the dust particle density of magnesium powder, the laser parameters of the PIV velocity measurement system, and the frame rate of the high-speed camera, etc.

[0116] The present application specifies the specific parameters of the experimental device, which is based on in-depth research and optimization of the experimental object and measurement accuracy. These parameters are not simply selected by routine selection, but are carefully designed and debugged to ensure the accuracy and reliability of the experimental results. The selection of PIV laser interval time and high-speed camera frame rate is based on in-depth research on dust flow characteristics and measurement accuracy, and the specification of these parameters is the key to the accurate measurement of the present application, which embodies the innovation and practicality of the present application in technical details.

[0117] It should be noted that the description of the device of the present application embodiment is similar to the description of the above method embodiment, and has similar beneficial effects as the same method embodiment, so it is not repeated. For technical details not disclosed in the present device embodiment, please refer to the description of the method embodiment of the present application for understanding.

[0118] The above is only an embodiment of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement and improvement within the spirit and scope of the present application are included in the protection scope of the present application.

[0119] It is to be understood that the terminology "one embodiment" or "an embodiment" used throughout this specification means that a particular feature, structure or characteristic described is included in at least one embodiment of the application. Therefore, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures or characteristics can be combined in any suitable manner in one or more embodiments. It is to be understood that the sequence of steps in the above-described various embodiments of the present application does not mean that the execution order of the steps is prior or posterior, and the execution order of the steps should be determined according to their functions and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The sequence of the above-described embodiments of the present application is only for description, and does not represent the advantages or disadvantages of the embodiments.

[0120] It should be noted that the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises... a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element. In several embodiments provided in the present application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The above-described apparatus embodiments are only illustrative, for example, the division of the units is only a logical functional division, and actual implementation can have another division, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0121] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An experimental system for calculating dust concentration inside a pipeline under shock wave action, comprising a vertical pipeline dust explosion device, a PIV velocity measurement system, and a high-speed camera, characterized in that, The vertical pipe dust explosion device includes at least a vertical pipe body, a dust spraying system, and a data analysis module; three of the four sides of the vertical pipe body are provided with four observation windows from bottom to top; the dust spraying system is used to spray dust particles upward from the bottom of the vertical pipe body under preset working conditions; The PIV speed measurement system includes a PIV laser and a PIV camera; the laser output by the PIV laser is perpendicularly injected into the vertical pipe body through the middle surface of the three surfaces; the high-speed camera and the PIV camera are respectively facing the left and right sides adjacent to the middle surface, and the PIV camera and the high-speed camera are set on the same horizontal plane; The high-speed camera is used to capture the state inside the entire vertical pipe body and record the visible duration of the dust particles passing through the third observation window from bottom to top on the left side. The PIV velocities are used to acquire the particle inflow velocity and particle outflow velocity through the third observation window. The data analysis module is used to receive data from the high-speed camera and the PIV speed measurement system, and based on the visible duration, the particle inflow velocity, and the particle outflow velocity, combined with the dimensions of the vertical pipe body and the dust particle density, calculates the real-time dust mass and real-time dust concentration passing through the third observation window using the law of conservation of mass; the dimensions of the vertical pipe body include the cross-sectional area of ​​the vertical pipe body and the height of the third observation window; The calculation of real-time dust mass and concentration through the third observation window, based on the visible duration, particle inflow velocity, and particle outflow velocity, combined with the dimensions of the vertical pipe body and dust particle density, and using the law of conservation of mass, includes: Based on the pipe cross-sectional area and the height, the volume of the calculation area corresponding to the third observation window is determined; based on the dust inflow velocity at at least three different inlet locations, the dust particle density, and the pipe cross-sectional area, the inlet dust mass flow rate flowing through the inlet within a preset time is determined; based on the dust outflow velocity at at least three different outlet locations, the dust particle density, and the pipe cross-sectional area, the outlet dust mass flow rate flowing through the outlet within a preset time is determined; based on the inlet dust mass flow rate and the outlet dust mass flow rate, the mass change rate is determined; based on the mass change rate and the visible duration, the real-time dust mass passing through the third observation window is determined; based on the real-time dust mass and the volume, the real-time dust concentration passing through the third observation window is determined.

2. The experimental system according to claim 1, characterized in that, The data analysis module is also used to optimize and adjust the relevant parameters of the PIV speed measurement system according to the powder spraying pressure of the powder spraying system, including the shooting position, focal length, aperture setting of the PIV camera, and the adjustment of laser intensity and beam thickness; and to determine the optimal time interval between two adjacent laser beams through repeated experiments.

3. The experimental system according to claim 2, characterized in that, The lower the powder spraying pressure, the larger the optimal time interval and the higher the frame rate of the high-speed camera; when the powder spraying pressure is 1.2 MPa, the optimal time interval is 2 Hz.

4. The experimental system according to claim 1, characterized in that, The four observation windows on three sides of the vertical pipe body are made of quartz glass, and each observation window is circular with a diameter of 110 mm.

5. The experimental system according to claim 1, characterized in that, The vertical pipeline dust explosion device also includes a gas distribution system, which uses the Dalton pressure method to distribute gas and control the gas distribution error within 0.1%.

6. The experimental system according to claim 1, characterized in that, The PIV speed measurement system also includes a synchronization controller, which controls the trigger time and data acquisition start time of the PIV camera and the high-speed camera to synchronize, so that the PIV camera and the high-speed camera acquire image data at the same time.

7. The experimental system according to claim 1, characterized in that, The visible duration is calculated in the following way: Obtain the complete image sequence and total number of frames captured by the high-speed camera per unit time; The complete image sequence is analyzed frame by frame to locate the starting frame corresponding to the appearance of the first dust particle in the third observation window, and the ending frame corresponding to the complete departure of the first dust particle from the third observation window. Determine the number of target frames between the start frame and the end frame; The visible duration is determined based on the total number of frames and the target number of frames.

8. A method for calculating dust concentration inside a pipeline under the action of a shock wave, characterized in that, Applied to the experimental system as described in any one of claims 1 to 7, the method comprises: Initialize the vertical pipe-type dust explosion device, PIV velocity measurement system, and high-speed camera; After the PIV speed measurement system starts operating, the powder spraying system sprays dust particles upward from the bottom of the vertical pipe body through the powder spraying chamber, and the PIV camera and the high-speed camera simultaneously take pictures. The high-speed camera captures the state inside the entire vertical pipe body from the bottom up on the left side, which has four observation windows arranged sequentially from bottom to top, and records the visible time of the dust particles passing through the third observation window from bottom to top on the left side. The particle inflow velocity and particle outflow velocity through the third observation window are obtained using the PIV velocimetry system. The data analysis module calculates the real-time dust mass and concentration passing through the third observation window based on the visible duration, particle inflow velocity, and particle outflow velocity, combined with the dimensions of the vertical pipe body and dust particle density, using the law of conservation of mass. The dimensions of the vertical pipe body include the cross-sectional area of ​​the vertical pipe body and the height of the third observation window. The calculation of real-time dust mass and concentration through the third observation window, based on the visible duration, particle inflow velocity, and particle outflow velocity, combined with the dimensions of the vertical pipe body and dust particle density, and using the law of conservation of mass, includes: Based on the pipe cross-sectional area and the height, the volume of the calculation area corresponding to the third observation window is determined; based on the dust inflow velocity at at least three different inlet locations, the dust particle density, and the pipe cross-sectional area, the inlet dust mass flow rate flowing through the inlet within a preset time is determined; based on the dust outflow velocity at at least three different outlet locations, the dust particle density, and the pipe cross-sectional area, the outlet dust mass flow rate flowing through the outlet within a preset time is determined; based on the inlet dust mass flow rate and the outlet dust mass flow rate, the mass change rate is determined; based on the mass change rate and the visible duration, the real-time dust mass passing through the third observation window is determined; based on the real-time dust mass and the volume, the real-time dust concentration passing through the third observation window is determined.

9. The method according to claim 8, characterized in that, The real-time dust mass after the third observation window is calculated using the following formula: ； in, For dust particle density, The cross-sectional area of ​​the pipe. For the duration of viewing, , , The three dust inflow velocities are for the third observation window. , , The three dust outflow velocities are for the third observation window; The real-time dust concentration after the third observation window is calculated using the following formula: ； In the formula, This indicates the real-time dust concentration. This indicates the volume of the computational region.

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