CN111579448A - Powder particle motion state online detection device and method - Google Patents
Powder particle motion state online detection device and method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
- B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
- B65G53/34—Details
- B65G53/52—Adaptations of pipes or tubes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
- B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
- B65G53/34—Details
- B65G53/52—Adaptations of pipes or tubes
- B65G53/56—Switches
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
- B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
- B65G53/34—Details
- B65G53/66—Use of indicator or control devices, e.g. for controlling gas pressure, for controlling proportions of material and gas, for indicating or preventing jamming of material
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
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- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/10—Investigating individual particles
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Abstract
An online detection device and method for the motion state of powder particles belong to the technical field of powder conveying and detection of a device for repairing metal surface defects by laser. The powder particle motion state on-line detection device adopts a vertically arranged conveying pipeline, realizes suspension conveying of powder particles by using a pneumatic conveying mode, and comprises an air source, a gas flowmeter, a powder feeder, a main conveying pipeline, a powder detection box, a high-speed camera, a light source, a computer and a single chip microcomputer controller. In the high transparent PVC plastic pipeline, rely on the strength to carry the powder granule, through the structural design of Y type pipeline and reducing pipeline, be convenient for realize utilizing high-speed camera to the detection and the later stage image processing analysis of powder granule, final computer passes through the control controller and then adjusts step motor rotational speed control powder output, reaches the purpose of powder granule dynamic control. The device integrates the degree well, and the precision is higher, strong adaptability, simple operation, can short-term test powder conveying pipeline in the real-time status information of powder granule.
Description
Technical Field
The invention belongs to the technical field of powder conveying and detection of a device for repairing metal surface defects by laser, and relates to a device and a method for online detection of the motion state of powder particles.
Background
In the long-term use process of the metal part, surface defects such as cracks and the like can be generated under the action of uneven loads such as external alternating stress and the like. If the metal workpieces with the microcrack defects are used continuously, the mechanical performance of equipment is reduced, even the metal workpieces are broken, and a great safety accident is caused. Therefore, core equipment containing surface defects such as microcracks and the like and equipment with high added value are repaired in time, the service life of products can be prolonged, and materials can be saved.
The laser repairing technology is to form a layer of cladding layer on the surface of the defective metal by using high-power laser beams to achieve the effect of repairing the surface defect of the metal. The powder particle conveying and detecting device is a core device of the whole laser repairing device and directly determines the quality of the repaired metal surface.
Under the general condition, the smaller the particle size of the powder particles is, the larger the viscosity is, and meanwhile, the temperature, the humidity, the shape and other factors of the environment can influence the viscosity of the powder particles, so that the powder particles in the powder feeder are adhered, the powder cannot be continuously and stably discharged, the instability of the powder particles in a powder feeding pipeline is finally caused, and the repairing quality is influenced, therefore, the stable and reliable online detection and dynamic control device for the powder particles is designed for the laser repairing technology for coaxially feeding the powder, and the device has higher economic value and engineering application significance.
The existing powder particle detection method generally adopts a photoelectric sensor to irradiate a powder conveying pipeline, detects powder particles by a method of detecting the light passing rate, or detects the powder flow rate by a capacitance detection technology. In the method, when the powder particles are detected, the whole powder particle group is detected, and if the concentration of the powder particles in the pipeline is high, the detection with high precision cannot be realized.
Disclosure of Invention
In order to solve the problems, the invention develops a powder particle conveying and detecting system based on an image processing technology and a light scattering principle, which is used for online detection and dynamic control of powder particles. The system has the advantages of good integration degree, higher precision, strong adaptability and convenient operation, and can quickly detect the real-time information of the powder particles in the powder conveying pipeline.
In order to achieve the purpose, the invention adopts the following technical scheme:
the powder particle motion state online detection device adopts a vertically arranged conveying pipeline, realizes suspension conveying of powder particles by using a pneumatic conveying mode, and comprises an air source 1, a gas flowmeter 2, a powder feeder 3, a main conveying pipeline 6, a powder detection box 9, a high-speed camera 10, a light source 11, a computer 13 and a single-chip microcomputer controller 14.
The main conveying pipeline 6 is of an L-shaped structure and comprises a horizontal pipeline part and a vertical pipeline part, the conveying pipeline is a high-transparency PVC round plastic pipe, and powder particles in the conveying pipeline are finally conveyed in a suspended state. The horizontal pipeline is connected with an air source 1, a gas flowmeter 2 and a powder feeder 3 in sequence, the top of the vertical pipeline is divided into two branches which are Y-shaped pipelines, and then the Y-shaped pipelines are connected with a reducing pipeline and a powder particle detection box 9. The air source 1 is connected with the end part of a horizontal pipeline of the main conveying pipeline 6, the gas flowmeter 2 is fixed on the horizontal pipeline, the gas flowmeter 2 is mainly used for detecting gas flow and used for detecting information of the conveying gas flow at the inlet of the pipeline, and when the conveying gas flow is 6.03L/min and the gas speed is 2m/s, powder particles in the pipeline can be conveyed in a stable suspension state.
The powder feeder 3 is arranged on a horizontal pipeline of the main conveying pipeline 6 and comprises a powder feeding groove 4, a powder feeding groove cover plate 15, a stepping motor 5 and a screw mechanism 16. Step motor 5 and powder are located and are sent the powder groove 4 inside, send powder groove 4 top to be equipped with and send powder groove apron 15, and step motor 5 bottom is connected with screw mechanism 16, and screw mechanism 16 is located and is sent powder groove 4 bottom, and the powder granule drives screw mechanism 16 through step motor 5 and is rotated in main conveying pipeline 6, carries in the pipeline under the effect of air source 1. The main conveying pipe section communicated with the lower part of the powder feeder 3 adopts the structural design of a Venturi tube 17, and the structure is known according to the Bernoulli equation: the air in the same height and different pipe diameters has the characteristics of faster flow speed and lower pressure, and the structure sucks powder particles into the pipeline by utilizing the pressure difference generated by the change of the pipe diameters.
The sampling conveying branch 7 adopts the structural design of a reducing pipeline 18 and comprises an upper pipeline and a lower pipeline: the diameter of the upper pipeline is twice that of the lower pipeline, and the diameter of the upper pipeline is the same as that of the main conveying pipeline 6; in the powder granule transportation process, the transportation gas that flows through pipeline reducing 18 department can expand because of the volume grow, and gas-solid two-phase flow can demonstrate the transport state of dispersing, plays the effect of diluting 7 powder particle concentrations of sample pipeline, is convenient for realize utilizing high-speed camera to the detection of powder granule to and later stage image processing analysis.
The powder detection box 9 is internally in arc transition without edges and corners, so that the influence of a background on image processing can be reduced, the powder detection box 9 is sealed and light-proof, two opposite horizontal side surfaces are provided with through holes, and the vertical side surface is provided with a slit 12; the pipeline of 7 tops of sample conveying branch road passes the both sides face of powder detection box 9 perpendicularly, and the pipeline reducing is located 9 box belows of powder detection box, and the pipeline after the reducing is located 9 box insides of powder detection box, and the powder granule presents the motion of dispersing because of gas expansion after pipeline position 18. The strong light source 11 is emitted into the powder detection box 9 through the slit 12 and irradiates the sampling conveying branch 7 (high transparent PVC plastic) in the box. The side of the powder detection box 9 is provided with a high-speed camera 10, and the high-speed camera 10 is connected with a computer 13 for image analysis and calculation.
The powder particle motion state online detection method is realized based on the device and comprises the following steps:
first step, select the powder granule that the diameter is more even, put into drying device and dry the powder granule, reduce moisture wherein, reduce because the powder granule diameter is inhomogeneous and the powder granule adhesion that factors such as ambient humidity lead to, influence screw mechanism 16 and go out the powder volume.
And step two, opening the air source 1, adjusting the flow of the conveying gas, conveying powder particles by adopting the device at 6.03L/min, and detecting the flow of the gas in the main pipeline 6 in real time by using the gas flowmeter 2.
And thirdly, filling the dried powder particles into a powder feeding groove 4, covering a cover plate 15 of the powder feeding groove, opening a stepping motor 5 in the powder feeding groove 4, driving a screw mechanism 16 at the bottom to rotate by the stepping motor 5, and screwing the powder particles into the main pipeline 6 through the screw mechanism 16.
Fourthly, the powder particles move to the Y-shaped pipeline under the action of the air source 1, the Y-shaped pipeline of the device adopts an equal division structure design, namely the diameter D1 of the total conveying pipeline 6 is twice as large as the diameter D2 of the sampling conveying pipeline 7 and the diameter D2 of the conveying pipeline 8, so that the total number of the powder particles in the sampling conveying pipeline 7 can be reduced, and the detection precision is improved.
And fifthly, when the powder particles in the sampling conveying pipeline 7 move to the pipeline diameter-changing position 18, the diameter of the pipeline after diameter changing is 2 times of that of the sampling conveying pipeline 7 and is the same as that of the main conveying pipeline 6. Pipeline reducing position 18 department, because the pipeline diameter after the reducing becomes thick, move the gas density reduction and the inflation of here, the powder granule can present the dispersed state of suspension and carry, the interval between the powder granule increases, the concentration of powder granule reduces, and the particle shows more easily, and structural design is convenient for realize utilizing high-speed camera to the detection of powder granule like this to and later stage image processing analysis.
Sixthly, the sampling conveying pipeline after diameter reduction passes through the airtight and light-tight powder detection box 9, the strong light source 11 irradiates the conveying pipeline after diameter reduction through the slit 12 on the vertical side surface of the powder detection box 9, so that powder particles conveyed in a divergent state in the pipeline are subjected to Mie scattering under the irradiation of the strong light source 11, the light propagation direction is changed to form a dark region, then the motion state of the powder particles is shot by using the high-speed camera 10, an image is transmitted to the computer 13 for analysis and calculation, real-time concentration information of the powder particles in the pipeline is obtained after calculation, then the computer 13 controls the frequency of pulse output by the single chip microcomputer controller 14, the rotating speed of the stepping motor 5 is adjusted, the total amount of the powder particles screwed out by the screw mechanism 16 is adjusted, and finally the dynamic adjustment of the powder particles is realized.
And seventhly, the sampling conveying pipeline 7 and the conveying pipeline 8 which pass through the detection box 9 are finally converged into a pipeline 19, and the pipeline 19 is connected with a nozzle of the laser repairing device and used for providing stable and reliable powder for laser repairing.
The invention realizes the online detection of the motion state of powder particles based on the light scattering principle and the computer image processing technology, and specifically comprises the following steps:
the light scattering principle is as follows: the powder particles in the sampling and powder conveying pipeline 7 after diameter reduction are in a divergent state for suspension conveying, and the propagation direction of light of the powder particles is changed under the irradiation of the strong light source 11 to form a dark space, namely the powder particles are scattered; the motion state of the powder particles is photographed by the high-speed camera 10, and the image is transmitted to the computer 13 for calculation and analysis.
The computer image processing technology comprises the following steps: the shot powder particle motion state is transmitted to a computer 13 by using a high-speed camera 10, and the computer performs image processing through operations such as denoising, enhancement, particle segmentation and the like to finally obtain a clear powder particle conveying state image at a certain moment; through the processed picture, the powder particles can be displayed clearly, then the particles in the picture are labeled by using image processing software, the total number of the particles in the picture is counted, and then the real-time concentration information of the powder particles in the pipeline is obtained through formula calculation.
The invention has the beneficial effects that: according to the online detection device for the motion state of the powder particles, the powder particles are conveyed by virtue of force in a highly transparent PVC plastic pipeline, through the structural design of a Y-shaped pipeline and a reducing pipeline, the structural design is convenient for realizing detection and later image processing analysis of the powder particles by utilizing a high-speed camera, and finally, a computer controls the powder output by regulating the rotating speed of a stepping motor through a control controller, so that the aim of dynamically controlling the powder particles is fulfilled. The device integrates the degree well, and the precision is higher, strong adaptability, simple operation, can short-term test powder conveying pipeline in the real-time information of powder granule.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a cross-sectional view of the powder feeder and venturi circuit;
FIG. 3 is a view showing the structure of a stepping motor;
FIG. 4 is a sectional view of the powder feeding pipe;
FIG. 5 is a schematic diagram of the detection of the present invention;
FIG. 6 is a schematic view of a powder flow measuring cassette;
FIG. 7 is a diagram of computer image processing effects;
FIG. 8 is a diagram showing a movement state locus of powder particles at a speed of 1m/s (a partially enlarged pipeline); (a) a Y-shaped opening; (b) branch pipeline (inclined sampling branch pipeline);
FIG. 9 is a diagram showing a movement state locus of powder particles at a speed of 2m/s (a partially enlarged pipeline); (a) a Y-shaped opening; (b) branch pipelines (junctions of the inclined sampling branch pipelines and the vertical pipelines); (c) a reducing pipeline;
in the figure: the device comprises an air source 1, a gas flow meter 2, a powder feeder 3, a powder feeding groove 4, a stepping motor 5, a main powder conveying pipeline 6, a sampling powder conveying pipeline 7, a powder conveying pipeline 8, a powder detection box 9, a high-speed camera 10, a light source 11, a powder detection box detection gap 12, a computer 13, a single-chip microcomputer controller 14, a powder feeding groove cover plate 15, a screw mechanism 16, a venturi tube 17 and a pipeline reducing position 18.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, the present patent discloses an online detection device and method for the motion state of powder particles, which are mainly used for online real-time detection and dynamic control of powder particles; the detection device comprises an air source 1, a gas flowmeter 2, a powder feeder 3, a main conveying pipeline 6, a powder detection box 9, a high-speed camera 10, a light source 11, a computer 13 and a single-chip microcomputer controller 14.
As shown in figure 1, the powder particle motion state online detection device adopts pneumatic transmission powder particles, a main conveying pipeline 6 is of an L-shaped structure and comprises a horizontal pipeline part and a vertical pipeline part, the conveying pipeline is a high-transparency PVC round plastic pipe, and the powder particles in the conveying pipeline are finally conveyed in a suspended state. The horizontal pipeline is connected with an air source 1, a gas flowmeter 2 and a powder feeder 3 in sequence, the top of the vertical pipeline is divided into two branches which are Y-shaped pipelines, and then the Y-shaped pipelines are connected with a reducing pipeline and a powder particle detection box 9. The air source 1 is connected with the end part of a horizontal pipeline of the main conveying pipeline 6, the gas flowmeter 2 is fixed on the horizontal pipeline, and the gas flowmeter 2 is mainly used for detecting the gas flow and is used for detecting the information of the gas flow conveyed at the inlet of the pipeline.
Selecting air with higher purity as a power source for conveying powder particles, avoiding the influence of overhigh impurities in the air on a detection result, connecting an air source 1 to a right end interface of a main conveying pipeline 6, and connecting a gas mass flow meter 2 to the main conveying pipeline 6 for detecting the flow of the conveyed gas; according to the pneumatic transmission theory, the powder particles in the vertical pipeline are subjected to stress analysis, the suspension transmission speed of the single powder particles is calculated to be 1.12m/s, the shape of the powder particles is corrected due to the irregular shape of the powder particles, the suspension transmission speed of the corrected single powder particles is obtained to be 0.87m/s, and then the suspension transmission speed of the powder particle group at the volume concentration m is calculated through a formula0When the suspension velocity is between 5 and 12 percent, the suspension velocity of the particle group is between 0.55 and 0.72m/s according to a formula, and then the critical velocity V of the conveying gas is obtained through mathematical calculation and analysis according to the gas-solid two-phase flow conveying theoryk1.086m/s, because the critical conveying speed is the theoretical calculation result, the critical conveying speed is multiplied by the safety factor in engineering application, and finally the optimal speed of the conveying gas is 2m/s, and the gas flow is 6.03L/min。
As shown in fig. 2, the powder feeder 3 is disposed on a horizontal pipeline of the main conveying pipeline 6, and includes a powder feeding groove 4, a powder feeding groove cover plate 15, a stepping motor 5, and a screw mechanism 16. Step motor 5 and powder are located and are sent the powder groove 4 inside, send powder groove 4 top to be equipped with and send powder groove apron 15, and step motor 5 bottom is connected with screw mechanism 16, and screw mechanism 16 is located and is sent powder groove 4 bottom, and the powder granule drives screw mechanism 16 through step motor 5 and is rotated in main conveying pipeline 6, carries in the pipeline under the effect of air source 1. The design of a main pipeline 6 below the powder feeder is as follows according to Bernoulli equation: p + rho gh +1/2 rho v2Known as C (constant): the air in the same height and different pipe diameters has the characteristics of faster flow speed and lower pressure, and the structure sucks powder particles into the pipeline by utilizing the pressure difference generated by the change of the pipe diameters.
Because the powder granule is easily influenced by environment humiture, use the heat preservation stove heating stoving powder granule, reduce moisture in the powder granule, reduce the powder granule adhesion, and then reduce the influence to the play powder volume.
As shown in fig. 4, according to the concentration of the powder particles in the pipeline, the end of the vertical pipeline of the main conveying pipeline 6 is divided into a sampling conveying branch pipe 7 and a conveying pipeline 8 according to a fixed proportion (the device adopts an equal division way), the sampling conveying branch pipe 7 and the conveying pipeline 8 together form a Y-shaped pipeline with the vertical pipeline of the main conveying pipeline 6, and the total number of the powder particles in the sampling conveying pipeline 7 is reduced; sampling pipeline 7 adopts the structural design of pipeline reducing 18 simultaneously, including top pipeline and below pipeline two parts: the diameter of the upper pipeline is twice that of the lower pipeline, and the diameter of the upper pipeline is the same as that of the main conveying pipeline 6; in the powder granule transportation process, the transportation gas that flows through pipeline reducing 18 department can expand because of the volume grow, and gas-solid two-phase flow can demonstrate the transport state of dispersing, plays the effect of diluting 7 powder particle concentrations of sample pipeline, is convenient for realize utilizing high-speed camera to the detection of powder granule to and later stage image processing analysis.
As shown in FIG. 5, the powder particle detection box adopts circular arc transition inside, and has no edge angle, so that the influence of the background on the picture processing can be reduced.
As shown in fig. 1, the powder detecting box 9 is sealed and light-proof, and has two opposite horizontal sides with through holes and vertical sides with slits 12; the pipeline of 7 tops of sample conveying branch roads passes the both sides face of powder detection box 9 perpendicularly, and the pipeline reducing is located 9 box belows of powder detection box, and the pipeline after the reducing is located 9 box insides of powder detection box, and powder granule presents the motion of dispersing because of gas expansion behind pipeline position 18. The strong light source 11 is emitted into the powder detection box 9 through the slit 12 and irradiates the sampling conveying branch 7 (high transparent PVC plastic) in the box. The side of the powder detection box 9 is provided with a high-speed camera 10, and the high-speed camera 10 is connected with a computer 13 for image analysis and calculation.
In order to verify the optimal speed theory of gas delivery, a FLUENT simulation mode is adopted to carry out simulation analysis on the motion state and the speed distribution of powder particles in a pipeline; as shown in FIG. 8, set at-9.81 m/s in the Y-axis direction2The gravity acceleration, the gas-solid two-phase flow speed in the pipeline is 1m/s, the Injection Type of the particles adopts a surface mode, and the powder output is 0.0006 kg/s; because the conveying speed of the powder at the Y-shaped interface is low, the powder particles can not move in a stable suspension state and can not be shunted according to a set proportion; due to the low speed of the conveying gas and the gravity of the powder particles, the powder particles can be accumulated on the outer side pipe wall at the branch pipe, and cannot be conveyed uniformly and stably.
As shown in fig. 9, at a gas delivery speed of 2m/s, the powder can stably move in a suspended state at the Y-shaped interface and can be well shunted according to a designed structure; the powder particles at the bent pipe can vertically move upwards in a stable suspension state after passing through the bent pipe; the powder particles at the sampling reducing pipeline 18 can be dispersed under the condition that the air density is reduced, and the powder particles can be uniformly and stably conveyed.
Therefore, under the gas conveying speed of 1m/s, the powder particles can not stably move in a suspension state in the pipeline due to the factors such as self gravity, energy loss in the conveying process and the like; when the speed of the conveying gas is 2m/s, the conveying gas can overcome the factors such as the self gravity of powder particles and the like, and finally moves in a stable suspension state in a pipeline, so that reliable powder is provided for the whole laser repair device.
Analyzing the speed of the powder particles in the pipeline at each position, and selecting a proper high-speed camera; when the powder particles move in the vertical pipeline, the speed is slightly less than the gas conveying speed by 2m/s because partial conveying energy needs to be consumed by overcoming the self gravity; when the powder particles move to the Y-shaped nozzle, the speed is reduced to about 1.5m/s due to the loss of part of energy caused by collision with the Y-shaped nozzle; then the powder particles enter a branch pipeline, the pipe diameter is narrowed, the movement speed of the powder particles is gradually increased again, and finally the maximum speed is 3.4 m/s; the powder particles move to the bent pipe, collide with the outer pipe wall to lose part of energy, and the speed is reduced to about 2.45m/s from the maximum value of 3.4 m/s; the powder particles pass through the sampling reducing pipeline 18, the air density is reduced due to the increase of the pipe diameter, the powder particles move in a divergent state, the moving speed of the powder particles is further reduced, and the speed is reduced to about 1 m/s.
The movement track and the speed of the powder particles in the pipeline are analyzed through Fluent software, the previous theoretical calculation result is well verified, and therefore the feasibility of the design of the powder particle detection device is also verified.
The shot images are influenced by the environment and the movement speed of the powder particles in the pipeline, so that the particles have unclear phenomena such as smear and the like; because the reducing pipeline 18 is vertically arranged, the powder particles in the pipeline are acted by gravity, and the movement speed of the powder particles at the sampling pipe is actually 1 m/s; therefore, the speed of the powder particles can be reduced by adopting the vertical pipeline and the reducing pipeline, and meanwhile, the powder particles at the position of the reducing pipeline 18 are conveyed in a divergent suspension state, so that the detection of the powder particles is facilitated; in addition, in order to reduce the influence of factors such as smear and depth of field on the on-line detection accuracy, a camera with higher resolution, faster frame rate, larger depth of field and shorter exposure time should be selected.
As shown in fig. 7, the captured picture of the motion state of the powder particles is transmitted to the computer 13 by the high-speed camera 10, and the computer performs image processing through operations such as denoising, enhancement, particle segmentation and the like, and finally obtains a clear powder particle conveying state image at a certain moment; through the picture that has handled, the powder granule can be more clear show, then utilize image processing software to carry out the label to the granule in the image, count out the total number of granule in the image, then calculate through the formula and obtain the real-time concentration information of powder granule in the pipeline:
volume of each powder particle
Volume of pipeline
Gas/solid two-phase mixing ratio:
in the above formula, R is the radius of the pipeline, H is the field width of the high-speed camera, WgFor conveying gas masses, psIs the powder particle density, p is the air density, VsIs the mass of the powder particles, VgFor the volume of gas delivered, N is the total number of particles and N is the powder particle concentration.
The online detection of the powder flow is realized through the real-time detection of the powder particle concentration, then the computer sends an instruction to the stepping motor 5, the powder output amount is adjusted by adjusting the rotating speed of the stepping motor 5, and finally the dynamic control of the powder flow is achieved.
The above-mentioned embodiments only express the embodiments of the present invention, but not should be understood as the limitation of the scope of the invention patent, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these all fall into the protection scope of the present invention.
Claims (3)
1. The on-line detection device for the motion state of the powder particles is characterized by realizing the suspension transportation of the powder particles by utilizing a pneumatic transportation mode and comprising an air source (1), a gas flowmeter (2), a powder feeder (3), a main transportation pipeline (6), a powder detection box (9), a high-speed camera (10), a light source (11), a computer (13) and a single chip microcomputer controller (14);
the main conveying pipeline (6) is of an L-shaped structure and comprises a horizontal pipeline part and a vertical pipeline part, and the conveying pipeline is transparent; one end of the horizontal pipeline is sequentially connected with an air source (1), a gas flowmeter (2) and a powder feeder (3), the other end of the horizontal pipeline is communicated with the vertical pipeline, and the top of the vertical pipeline is divided into two branches; the gas flowmeter (2) is used for detecting the information of the flow rate of the gas conveyed at the inlet of the pipeline;
the powder feeder (3) is arranged on a horizontal pipeline of the main conveying pipeline (6) and comprises a powder feeding groove (4), a powder feeding groove cover plate (15), a stepping motor (5) and a screw mechanism (16); the stepping motor (5) and the powder are arranged inside the powder conveying groove (4), the powder conveying groove cover plate (15) is arranged at the top of the powder conveying groove (4), the bottom of the stepping motor (5) is connected with the screw mechanism (16), the screw mechanism (16) is arranged at the bottom of the powder conveying groove (4), and the powder particles are driven by the stepping motor (5) to drive the screw mechanism (16) to be screwed into the main conveying pipeline (6) and conveyed in the pipeline under the action of the air source (1);
the top of the vertical pipeline of the main conveying pipeline (6) is divided into a sampling conveying branch (7) and a conveying pipeline (8) according to a fixed proportion, and the sampling conveying branch (7) and the conveying pipeline (8) jointly form a Y-shaped pipeline with the vertical pipeline of the main conveying pipeline (6) and are used for reducing the total number of powder particles in the sampling conveying pipeline (7); the sampling conveying branch (7) adopts the structural design of a reducing pipeline (18), and comprises an upper pipeline and a lower pipeline: the diameter of the upper pipeline is twice that of the lower pipeline, and the diameter of the upper pipeline is the same as that of the main conveying pipeline (6);
the powder detection box (9) is internally in arc transition without edges and corners, so that the influence of a background on picture processing can be reduced, the powder detection box (9) is sealed and light-proof, the upper horizontal side surface and the lower horizontal side surface are provided with through holes, and the vertical side surface is provided with a slit (12); a pipeline above the sampling conveying branch (7) vertically penetrates through a horizontal side through hole of the powder detection box (9), a pipeline reducing position (18) is positioned below the powder detection box (9), the pipeline after reducing is positioned in the powder detection box (9), and powder particles are in divergent motion due to gas expansion after passing through the pipeline reducing position (18); the strong light source (11) is emitted into the powder detection box (9) through the slit (12) and irradiates on the transparent sampling and conveying branch (7) in the box; the side of the powder detection box (9) is provided with a high-speed camera (10), and the high-speed camera (10) is connected with a computer (13) for image analysis and calculation.
2. The on-line detection device for the motion state of the powder particles as claimed in claim 1, wherein the main conveying pipeline section communicated with the lower part of the powder feeder (3) adopts the structural design of a venturi tube (17), and the powder particles are sucked into the main conveying pipeline (6) by using the pressure difference generated by the change of the pipe diameter.
3. The online detection method for the motion state of the powder particles, which is realized based on the online detection device of claim 1 or 2, is characterized by comprising the following steps:
firstly, drying powder particles with uniform diameter;
secondly, opening an air source (1), adjusting the flow of conveying gas, conveying powder particles by adopting 6.03L/min, and detecting the flow of the gas in the main conveying pipeline (6) in real time through a gas flowmeter (2);
thirdly, putting the dried powder particles into a powder feeding groove (4), covering a cover plate (15) of the powder feeding groove, opening a stepping motor (5) in the powder feeding groove (4), driving a screw mechanism (16) at the bottom to rotate by the stepping motor (5), and screwing the powder particles into the main pipeline 6 through the screw mechanism (16);
fourthly, the powder particles move to a Y-shaped pipeline under the action of the air source (1), the Y-shaped pipeline of the device adopts an equal division structure design, namely the diameter D1 of the main conveying pipeline (6) is twice of the diameter D2 of the sampling conveying pipeline (7) and the diameter D2 of the conveying pipeline (8), so that the total quantity of the powder particles in the sampling conveying pipeline (7) is reduced, and the detection precision is improved;
fifthly, when the powder particles in the sampling and conveying pipeline (7) move to a pipeline diameter-changing position (18), the diameter of the pipeline after diameter changing is 2 times of that of the sampling and conveying pipeline (7); at the pipeline diameter-changing position (18), as the diameter of the pipeline after diameter changing becomes thicker, the density of the gas moving to the position is reduced and the gas expands, and the powder particles are conveyed in a suspended divergent state;
sixthly, the sampling conveying pipeline after diameter changing passes through a sealed lightproof powder detection box (9), a strong light source (11) irradiates the conveying pipeline after diameter changing through a slit (12) on the vertical side surface of the powder detection box (9), and powder particles conveyed in a divergent state in the pipeline are subjected to Mie scattering under the irradiation of the strong light source (11) to form a dark area; then shooting the motion state of the powder particles by using a high-speed camera (10), transmitting the image to a computer (13) for analysis and calculation, and obtaining real-time concentration information of the powder particles in the pipeline after calculation; then the computer (13) controls the frequency of the pulse output by the singlechip controller (14), adjusts the rotating speed of the stepping motor (5), further adjusts the total amount of the powder particles screwed out by the screw mechanism (16), and finally realizes the dynamic adjustment of the powder particles;
and seventhly, finally converging the sampling conveying pipeline (7) and the conveying pipeline (8) which pass through the detection box (9) into a pipeline (19), wherein the pipeline (19) is connected with a nozzle of the laser repair device to provide stable and reliable powder for laser repair.
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