A purge device and calibration system and method for reducing powder contamination in vertical pipelines

Abstract

The present invention belongs to the technical field of sensor calibration equipment, and specifically relates to a purging device and a calibration system and method for mitigating powder contamination in a vertical pipeline. The purging device includes a plurality of four-way nozzles, a gas distributor and a controller. Each four-way nozzle is installed on the pipe wall of a vertical pipeline. The gas distributor includes an air source, a main control valve, a manifold block, a plurality of sub-control valves and a plurality of air pipes. The main control valve is connected to the outlet of the air source, and the outlet of the main control valve is connected to the inlet of the manifold block; each outlet of the manifold block is connected to each four-way nozzle through an independent air pipe sub-control valve. The controller is electrically connected to the main control valve and the sub-control valve; in the dust prevention mode, the airflow sprayed by the four-way nozzle forms an air curtain on the inner wall of the vertical pipeline that can prevent dust contamination. In the cleaning mode, each four-way nozzle is alternately opened in a preset order to complete the pipeline cleaning. The present invention solves the problem that the inner wall of the vertical pipeline is easily contaminated with dust during the calibration of the dust concentration sensor.

Description

Technical Field

[0001] The invention belongs to the technical field of sensor calibration equipment, and in particular relates to a purging device for alleviating powder contamination in a vertical pipeline, and a calibration system and a calibration method for a dust concentration sensor using the purging device. Background Art

[0002] In order to ensure high fire extinguishing efficiency, low toxicity and environmental friendliness, dry powder fire extinguishing agent is gradually replacing halon fire extinguishing agent and becoming one of the fire extinguishing agents that are vigorously promoted. When extinguishing a fire, the dry powder fire extinguishing agent is diffused in the space in a flooding manner. Accurately measuring its concentration distribution is the key to effectively extinguishing the fire. Fiber optic probe type dust concentration sensor is usually used to measure the concentration distribution of dry powder fire extinguishing agent. Such sensors must be calibrated before measurement to ensure the accuracy of the measurement.

[0003] In the prior art, the calibration method of the fiber optic probe type dust concentration sensor is to place it in a vertical pipe, and then introduce different concentrations of dust-containing gas into the vertical pipe; then calibrate or correct the sensor's detection results based on the known dust concentration. C It is necessary to combine the dust loss rate in the dust generator that produces dusty gas M , gas flow rate at the dust concentration sensor V and the cross-sectional area of ​​the pipe S To calculate comprehensively, and satisfy the following formula:

[0004] .

[0005] In this calibration system, whether the dust input into the vertical pipe by the dust generator will be contaminated on the inner wall of the pipe has become a key factor restricting the accuracy of the calibration experiment. This is because when the dust falls along the vertical pipe, if the contamination rate on the inner wall of the pipe is high, the calculated dust concentration C in the pipe will be higher than the actual value (part of the powder loss of the dust generator is contaminated by the pipe and does not reach the dust concentration sensor). In this case, the actual concentration value and the theoretical concentration value used for calibration are quite different, which will cause the calibration of the dust concentration sensor to fail, and further affect the detection accuracy of the calibrated dust concentration sensor. Therefore, how to solve the problem of dust contamination on the inner wall of the vertical pipe during the calibration of the powder concentration sensor is becoming a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In order to solve the problem that the inner wall of the pipeline is easily contaminated with dust during the calibration of the dust concentration sensor, the present invention provides a purge device for alleviating powder contamination in a vertical pipeline and a calibration system and a calibration method of a dust concentration sensor using the purge device.

[0007] The present invention is implemented by the following technical solutions:

[0008] A purge device for alleviating powder contamination in a vertical pipeline comprises a plurality of four-way nozzles, a gas distributor and a controller.

[0009] Each four-way nozzle is installed on the wall of the vertical pipe to be purged and is used to spray air into the pipe. The four-way nozzles are arranged in a grid on the wall of the vertical pipe, and each four-way nozzle has a unique layer code and bit code. Each four-way nozzle includes four nozzles, two of which spray in the axial direction of the pipe, and the other two nozzles spray in the tangential direction of the pipe.

[0010] The gas distribution instrument includes a gas source, a main control valve, a manifold block, multiple sub-control valves and multiple gas pipes. The gas source stores background gas in a high-pressure state. The main control valve is connected to the outlet of the gas source and is used to manage the flow of the background gas discharged from the gas source. The outlet of the main control valve is connected to the inlet of the manifold block; each outlet of the manifold block is connected to each four-way nozzle through an independent gas pipe and an independent sub-control valve. The sub-control valve is used to manage the opening and closing of each four-way nozzle.

[0011] The controller is electrically connected to the main control valve and the sub-control valve; it is used to: (1) in the dust prevention mode, obtain the gas flow rate V at the dust concentration sensor in the vertical pipeline, query a preset "flow rate-number of layers mapping", and then issue instructions to the main control valve and each sub-control valve according to the query result, control all four-way nozzles of the specified layer to spray background gas into the vertical pipeline according to the preset standard flow rate, so as to form an air curtain on the inner wall of the vertical pipeline that can prevent dust contamination. (2) in the cleaning mode, issue instructions to the main control valve and each sub-control valve, and alternately control each four-way nozzle to spray background gas at the maximum flow rate according to the preset sequence to complete pipeline cleaning.

[0012] As a further improvement of the present invention, in the dust prevention mode, the controller opens the sub-control valves of all four-way nozzles of the designated layer, and then dynamically adjusts the opening of the main control valve according to the number of layers of the opened four-way nozzles.

[0013] In the cleaning mode, the control opens the main control valve to the maximum, and then alternately opens the sub-control valves of the four-way nozzles at the even positions in all odd-numbered layers and the odd positions in the even-numbered layers, as well as the sub-control valves of the four-way nozzles at the odd positions in all odd-numbered layers and the even positions in the even-numbered layers.

[0014] As a further improvement of the present invention, the distance between each four-directional nozzle and the four adjacent four-directional nozzles is equal, which is denoted as d . The distance between adjacent four-way sprinklers dSatisfies: when each four-way nozzle sprays background gas at a preset standard flow rate, the pressure generated at a distance of 1 / 2d away from the nozzle is not higher than a preset first pressure threshold value P1.

[0015] As a further improvement of the present invention, the maximum flow rate of the background gas sprayed by the four-way nozzle satisfies: when each four-way nozzle sprays the background gas at a preset maximum flow rate, the pressure generated at d away from the nozzle is not lower than a preset second pressure threshold P2.

[0016] As a further improvement of the present invention, the method for constructing the flow velocity-layer number mapping is as follows:

[0017] (1) At the specified gas flow rate V, turn on the four-way nozzles of all layers and start the test. During the test, gas containing powder is introduced into the vertical pipe, and the powder contamination amount m0 ​​in the vertical pipe is counted after the specified time. After the test, the inner wall of the vertical pipe is cleaned; the ventilation test under the current number of layers is completed.

[0018] (2) Close the four-way nozzle at the bottom layer of the vertical pipeline, repeat the above ventilation test, count the powder contamination amount m1 in the vertical pipeline after closing one layer, and calculate the powder contamination growth rate of the two ventilation tests. q t :

[0019] ,

[0020] In the above formula, m t and m t-1 Respectively indicate closing t Layer and t -1 layer of four-way nozzles, the amount of powder contamination in the vertical pipe during the experiment.

[0021] (3) Repeat step (2) to conduct the next round of testing until the growth rate of powder contamination in the current round of testing is q t Exceeds the preset growth rate threshold q0.

[0022] At this time, the number of layers of the four-way nozzle that was kept open in the previous round is taken as the optimal number of layers under the current gas flow rate V.

[0023] (4) Repeat steps (1) to (3) to test the optimal number of layers of the four-way sprinkler that should be kept open under all flow rate conditions, and establish the required flow rate layer mapping.

[0024] As a further improvement of the present invention, a nano coating for preventing dust contamination is provided on the inner wall of the vertical pipe.

[0025] As a further improvement of the present invention, the four-way nozzle is composed of an air pipe joint and a rectifier block. The rectifier block is in a cubic shape and has a spherical cavity in the center. One side of the rectifier block is provided with a connection hole for connecting the air pipe joint and communicating with the spherical cavity. Four surfaces connected to the surface with the connection hole are provided with air injection holes communicating with the spherical cavity. One end of the air pipe joint is used to connect the air pipe, and the other end is a connector for sealingly connecting with the connection hole of the rectifier block.

[0026] As a further improvement of the present invention, the air pipe joint and the rectifier block are threadedly connected; the connecting hole of the rectifier block is provided with an internal thread; and one end of the connecting head of the air pipe joint is provided with an external thread.

[0027] As a further improvement of the present invention, in the rectifier block, a conical cavity connected to the spherical cavity is provided on the other side opposite to the connecting hole as a buffer zone.

[0028] The present invention also includes a dust concentration sensor calibration system, which is used to calibrate the dust concentration sensor. The calibration system includes: a calibration pipeline, a dust generator, a purge device, a flow rate sensor and a host computer.

[0029] The calibration pipeline is a vertically placed pipeline with an open bottom, and a plurality of through holes distributed in an annular pattern are arranged on the wall of the calibration pipeline. The dust generator is used to introduce background gas mixed with a specified powder into the calibration pipeline along the upper opening.

[0030] The purge device adopts the aforementioned purge device for reducing powder contamination in vertical pipelines. Each four-way nozzle in the purge device is installed at each through hole on the wall of the calibration pipeline, and is used to spray background gas into the calibration pipeline; the gas distribution instrument and controller in the purge device are located outside the calibration pipeline.

[0031] The flow rate sensor and the dust concentration sensor to be calibrated are both fixed in the calibration pipe near the lower opening. The flow rate sensor is used to measure the gas flow rate in the pipe near the dust concentration sensor.

[0032] The host computer is electrically connected to the dust generator, the purge device, the flow rate sensor and the dust concentration sensor to be calibrated. The host computer is used to obtain the dust loss rate of the dust generator in real time during the calibration experiment. M , gas flow rate V And the detection signal of the dust concentration sensor A , then according to M , V And the cross-sectional area of ​​the pipe S Calculate the dust concentration in the calibration pipeline C , and then in C and A Create a mapping between them.

[0033] The present invention also includes a dust concentration sensor calibration method, which includes:

[0034] Install the gas concentration sensor to be calibrated in the calibration system of the dust concentration sensor as mentioned above; then automatically implement the following process under the control of the host computer:

[0035] (1) Control the dust generator to introduce dust-free background gas into the calibration pipeline at a preset flow rate.

[0036] (2) According to the gas flow rate in the calibration pipeline, the purge device is controlled to operate in the dust prevention mode, and background gas is sprayed into the calibration pipeline to form an air curtain on the pipeline wall.

[0037] (3) Control the dust generator to introduce background gas containing dust with gradually increasing dust concentration into the calibration pipeline, and record the dust loss rate in real time M , gas flow rate V And the detection signal of the dust concentration sensor A .

[0038] (4) Using multiple sets of dust concentrations C With detection signal A A data pair is obtained to establish a mapping relationship between the output signal of the dust concentration sensor and the measured dust concentration detection result and send it to the dust concentration sensor for calibration.

[0039] (5) Turn off the dust generator and dust concentration sensor; control the purge device to operate in the cleaning mode, and the four-way nozzles in each layer or column alternately spray background gas to complete the dust cleaning of the inner wall of the pipeline.

[0040] The technical solution provided by the present invention has the following beneficial effects:

[0041] The present invention provides a purging device for slowing down the contamination of powder in a vertical pipeline. The purging device sprays airflow in the tangential and circumferential directions toward the inner wall of the pipeline through nozzles densely distributed on the pipeline wall, thereby forming an air curtain for isolating dust. The air curtain blocks the dust flowing through the vertical pipeline from splashing onto the pipeline wall, thereby effectively slowing down the contamination of the pipeline wall. In addition, the purging device provided by the present invention also sets different spraying strategies for each nozzle to clean the dead corners in the pipeline, thereby realizing self-cleaning inside the pipeline.

[0042] The purging device provided by the present invention can effectively suppress dust contamination of the dust concentration sensor during the calibration process, thereby improving the calibration accuracy of the dust concentration sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 This is a schematic structural diagram of a purge device for alleviating powder contamination in a vertical pipeline provided in Example 1 of the present invention.

[0045] Figure 2 The vertical pipeline in Example 1 of the present invention is equipped with a large number of four-way nozzles.

[0046] Figure 3 This is a schematic diagram of the structure of the four-directional nozzle used in Example 1 of the present invention.

[0047] Figure 4 It is a half-section view of the four-directional nozzle used in Example 1 of the present invention.

[0048] Figure 5 The figure shows the airflow distribution generated by the four-way nozzle in the vertical pipeline in Example 1 of the present invention.

[0049] Figure 6 This is a flow chart of the method for constructing flow velocity-layer number mapping in Example 1 of the present invention.

[0050] Figure 7 This is the switching strategy of each four-directional nozzle in the cleaning mode in Example 1 of the present invention.

[0051] Figure 8 It is a schematic diagram of the structure of a four-directional nozzle using a triangular prism-shaped rectifying block.

[0052] Fig. 9 It is a schematic diagram of the structure of a four-directional nozzle using a quadrangular pyramid-shaped rectifying block.

[0053] Fig.10 This is a step flow chart of the dust concentration calibration method provided in Example 2 of the present invention.

[0054] The markings in the figure are:

[0055] 1. Four-way nozzle; 2. Gas distributor; 11. Air pipe joint; 12. Rectifier block; 21. Air source; 22. Main control valve; 23. Manifold block; 24. Sub-control valve; 25. Air pipe; 111. Connector; 120. Spherical cavity; 121. Connecting hole; 122. Jet hole; 123. Buffer zone. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0057] Example 1

[0058] This embodiment provides a purging device for reducing powder contamination in vertical pipelines. The typical application scenario of the purging device is in the calibration experiment of the dust concentration sensor. It is used to prevent dust and clean the pipe wall of the vertical pipeline in the calibration environment, thereby overcoming the influence of dust contamination on the pipe wall on the final calibration accuracy of the dust concentration sensor.

[0059] Specifically, Figure 1 As shown, the purging device for mitigating powder contamination in a vertical pipeline provided in this embodiment includes a plurality of four-way nozzles 1, a gas distributor 2, and a controller. Each of the four-way nozzles 1 is fixedly mounted on the wall of the vertical pipeline to be purged and is used to spray air into the pipeline. Figure 2 As shown, the four-way nozzles 1 are arranged in a grid pattern on the wall of the vertical pipe. That is, the four-way nozzles 1 are evenly spaced in multiple layers on the vertical pipe, and the four-way nozzles 1 in each layer are evenly spaced in a ring at a fixed distance. At this time, each four-way nozzle 1 has a unique layer code i and bit encoding j , i=1, 2, 3, …, n; n represents the number of layers of four-directional sprinklers 1 installed in the vertical pipe; j=1, 2, 3, …, m; m represents the total number of four-directional sprinklers 1 installed in each layer. For example, for the circular tube-type vertical pipe used in the calibration experiment, multiple layers of four-directional sprinklers 1 can be set at intervals of 10 cm in the axial direction of the pipe. For each layer in the vertical pipe, 12 four-directional sprinklers 1 can be set in the same layer at intervals of 30° at the central angle of the circle, and each four-directional sprinkler 1 is respectively set at the azimuth of 0°, 30°, 60°, …, 330° of the cross section of the circular pipe. On this basis, position coding ( i , j ) represents any four-way sprinkler 1 on the vertical pipe. For example, (3,3) represents a four-way sprinkler 1 at 60° in the third layer on the vertical pipe.

[0060] In the four-directional sprinkler heads 1 arranged in a grid in this embodiment, except for the four-directional sprinkler heads 1 located at the top and bottom of the vertical pipe, each of the remaining four-directional sprinkler heads 1 has four adjacent four-directional sprinkler heads 1, which are respectively located in the four directions of up, down, left and right of each four-directional sprinkler head 1. Each four-directional sprinkler head 1 includes four nozzles, of which the spraying directions of two nozzles are along the axial direction of the pipe, and the spraying directions of the other two nozzles are along the tangential direction of the pipe. That is, the spraying direction of each four-directional sprinkler head 1 is respectively directed to the four adjacent four-directional sprinkler heads 1.

[0061] like Figure 3As shown, in a typical scheme of this embodiment, the four-way nozzle 1 adopts a split design, and each four-way nozzle 1 is composed of an air pipe 25 joint 11 and a rectifier block 12, which are threadedly connected. The rectifier block 12 is in a cubic shape and has a spherical cavity 120 in the center. One side of the rectifier block 12 is provided with a connecting hole 121 for connecting the air pipe 25 joint 11 and communicating with the spherical cavity 120, and an internal thread is provided at the connecting hole 121. The four surfaces connected to the surface where the connecting hole 121 is provided are provided with jet holes 122 connected to the spherical cavity 120, and the four jet holes 122 point to the four directions of up, down, left and right respectively. One end of the air pipe 25 joint 11 is used to connect the air pipe 25, and the other end is a connector 111 for sealingly connecting with the connecting hole 121 of the rectifier block 12, and one end of the connector 111 of the air pipe 25 joint 11 is provided with an external thread. The air pipe 25 connector 11 in this embodiment is a 7-shaped pipe connector. In other embodiments, the air pipe 25 connector 11 may also be a straight-shaped conventional connector with an external thread at one end.

[0062] The function of the rectifying block 12 provided in this embodiment is to eject the airflow transmitted from the air pipe 25 joint 11 in four specified directions. When the airflow enters the spherical cavity 120 in the rectifying block 12 from one side of the connecting hole 121, it will first be blocked by the cavity wall of the opposite spherical cavity 120, resulting in an increase in the pressure in the spherical cavity 120. The high-pressure gas in the spherical cavity 120 will be released through the four jet holes 122 at the top, bottom, left and right, thus generating a corresponding jet airflow. In a more optimized solution of this embodiment, as shown in FIG. Figure 4 As shown, a conical cavity connected to the spherical cavity 120 is provided on the other side opposite to the connecting hole 121 as a buffer zone 123. The buffer zone 123 can reduce the wear and consumption caused by long-term or frequent impact of the airflow, and can more evenly disperse the airflow discharged from each nozzle.

[0063] When installing the four-way sprinkler 1, a through hole for installing each four-way sprinkler 1 is reserved on the vertical pipe. The technician places the rectifier block 12 inside the pipe, and makes the connection hole 121 of the four-way sprinkler 1 face outward and correspond to the position of each through hole. Next, the connector 111 with external threads in the 7-shaped air pipe 25 is inserted into the pipe along the through hole. At this time, the nozzle direction of the rectifier head is respectively pointed to the axial direction and tangential direction of the pipe and kept fixed, and then the air pipe 25 joint 11 is screwed so that the air pipe 25 interface and the rectifier block 12 clamp the pipe wall.

[0064] The gas distribution device 2 in this embodiment is a device for controlling each four-way nozzle 1 on the vertical pipeline to spray gas into the vertical pipeline. Figure 1As shown, each gas distributor 2 is composed of a gas source 21, a main control valve 22, a manifold block 23, a plurality of sub-control valves 24 and a plurality of gas pipes 25. Among them, the gas source 21 stores background gas in a high-pressure state. The background gas in this embodiment refers to the gas that will not affect the normal conduct of the experiment. For example, in the dust concentration sensor test or calibration experiment, the dust generator at the front end will transport dust-containing air into the vertical pipeline. At this time, the accessory gas in the purge device of this embodiment uses dust-free air as the background gas. The main control valve 22 is connected to the outlet of the gas source 21 and is used to manage the flow of the background gas discharged from the gas source 21. The outlet of the main control valve 22 is connected to the inlet of the manifold block 23; each outlet of the manifold block 23 is connected to each four-way nozzle 1 through an independent gas pipe 25 and an independent sub-control valve 24.

[0065] In the gas distributor 2 of the purge device of the present embodiment, when the main control valve 22 connected to the gas source 21 is opened, the high-pressure gas stored therein will first enter the manifold block 23, and the manifold block 23 will divide the gas introduced into multiple airflows and discharge them from various outlets of the manifold block 23. Each airflow divided by the manifold block 23 is connected to one of the four-way nozzles 1 on the vertical pipeline through an independent air pipe 25. Among them, an independent sub-control valve 24 is provided in the air pipe 25 for connecting the four-way nozzle 1 and the manifold block 23. The sub-control valve 24 corresponds to the four-way nozzle 1 one by one, and the sub-control valve 24 is used to manage the opening and closing of each four-way nozzle 1. By opening and closing the sub-control valve 24, each four-way nozzle 1 can be controlled to spray the background gas stored in the gas source 21 into the vertical pipeline in a partitioned manner.

[0066] Finally, the controller is electrically connected to the main control valve 22 and the sub-control valve 24, and the controller is the control center of the entire purge device. In this embodiment, the main control valve 22 and the sub-control valve 24 are both electrically controlled valves, such as solenoid valves. During the operation of the purge device, the controller will issue instructions to the main control valve 22 according to the situation, and dynamically adjust the opening of the main control valve 22 according to the total number of four-way nozzles 1 that need to be opened and the required flow rate of each four-way nozzle 1.

[0067] Under the control of the controller, the purging device for mitigating powder contamination in the vertical pipeline provided in this embodiment has two main working modes, one is a dust prevention mode, and the other is a cleaning mode. The former is turned on before the vertical pipeline starts to transport the dust-containing medium. In this mode, a uniform air curtain is formed inside the pipeline, thereby minimizing the dust from being contaminated on the inner wall of the vertical pipeline. Among them, the latter is turned on after the vertical pipeline completes the transportation of the dust-containing medium. In this mode, each nozzle will spray a strong airflow to other adjacent four-way nozzles 1, thereby directionally purging the dead angle area formed near each four-way nozzle 1 installed in the vertical pipeline.

[0068] In order to make the performance and advantages of the purge device for reducing powder contamination in a vertical pipeline provided by the present embodiment more obvious, the functions and principles of the purge device provided by the present embodiment are described in detail below in combination with two working modes:

[0069] 1. Dust-proof mode

[0070] When dusty gas is transported in a vertical pipe, most of the dust particles will move downward along the pipe with the airflow, while a small number of dust particles will tend to move radially along the pipe under the influence of Brownian motion. The particles moving toward one side of the pipe wall will eventually hit the inner wall of the vertical pipe and become contaminated.

[0071] In the dust prevention mode of the purge device provided in this embodiment, multiple layers of four-way nozzles 1 are simultaneously opened in the vertical pipe. Figure 5 As shown, the airflow ejected outward by each four-way nozzle 1 will intersect with the airflow ejected by other adjacent four-way nozzles 1. Among them, the airflow before the intersection will form a layer of air curtain on the inner side of the inner wall of the pipe. The airflow after the intersection will also form an intersecting airflow toward the inner side of the pipe between any two adjacent four-way nozzles 1. On this basis, on the one hand, the intersecting airflow has a "gathering" effect on the airflow transported in the pipe, which can suppress the movement tendency of some dust in the gas transported in the vertical pipe to the side of the pipe wall. On the other hand, even if some dust particles overcome the constraints and reach the side close to the pipe wall, they will be blocked by the air curtain formed by each four-way nozzle 1 on the inner side of the pipe wall. The air curtain generated by each open four-way nozzle 1 is equivalent to a "barrier" suspended above the inner wall of the pipe, making it difficult for dust in the gas transported in the pipe to reach the inner wall of the vertical pipe. In summary, under the dual influence of the intersecting airflow and the air curtain, the dust contamination phenomenon on the inner wall of the vertical pipe can be effectively controlled.

[0072] In the actual application of the scheme of this embodiment, the four-way nozzle 1 sprays airflow mainly for two purposes, namely, to form an air curtain and to form an intersecting airflow along the radial direction of the pipeline and inward. In practical applications, the flow rate of the intersecting airflow should not be too large, so as to avoid interfering with the normal movement of dust particles contained in the main airflow transported in the vertical pipeline. In order to achieve the desired technical effect, this embodiment strictly controls the position of each four-way nozzle 1 and the gas flow rate of the spray. Specifically, in this embodiment, the distance between each four-way nozzle 1 and the four adjacent four-way nozzles 1 is equal, which is recorded as d The spray flow rates of all four-way nozzles 1 in the dust prevention mode are uniformly set to a fixed flow rate, which is recorded as the standard flow rate.

[0073] Distance between adjacent four-way sprinklers dSatisfies: when each four-way nozzle 1 sprays background gas at a preset standard flow rate, the pressure generated at a distance 1 / 2d away from the nozzle is not higher than a preset first pressure threshold value P1.

[0074] In addition, it is necessary to explain that: in the dust prevention mode, turning on all the four-way nozzles 1 in the vertical pipeline can achieve the best purpose of preventing dust contamination, but this will lead to more consumption of the gas source 21, that is, higher operating power consumption. The technicians of this case have found through testing that when the airflow / flow rate of the main airflow in the vertical pipeline is small, only the upper several layers of four-way nozzles 1 need to be turned on to achieve a better dust prevention effect, and when the airflow / flow rate of the main airflow in the vertical pipeline is small, more rows of four-way nozzles 1 need to be turned on to avoid dust contamination in the lower part of the pipeline.

[0075] In view of the above situation, in order to reduce the power consumption of the purge device during the actual application process, this embodiment obtains in advance through actual testing the minimum number of layers of the four-way nozzles 1 that need to be opened to achieve the required dust prevention effect under the main air flow conditions of different flow rates. Then, a corresponding "flow rate-number of layers mapping" is established based on the test data and stored in the controller. At this time, when the device is running in the dust prevention mode, the gas flow rate V at the dust concentration sensor in the vertical pipeline can be obtained first, and the preset flow rate-number of layers mapping can be queried. Then, according to the query result, instructions are issued to the main control valve 22 and each sub-control valve 24 to control all the four-way nozzles 1 of the specified layer to spray background gas into the vertical pipeline according to the preset standard flow rate, so as to form an air curtain on the inner wall of the vertical pipeline that can prevent dust contamination. The controller opens the sub-control valves 24 of all the four-way nozzles 1 of the specified layer, and then dynamically adjusts the opening of the main control valve 22 according to the number of layers of the opened four-way nozzles 1. For example, in a certain application scenario, 4 layers of four-way nozzles 1 need to be opened, the number of four-way nozzles 1 in each layer is 12, and the flow rate required by each four-way nozzle 1 is q1, then the opening of the main control valve 22 should satisfy the flow rate input to the manifold block 23 of 4×12×q1. The controller will issue instructions to each sub-control valve 24 according to the number of layers N of four-way nozzles 1 that need to be opened, so that the sub-control valve 24 corresponding to each four-way nozzle 1 with i≤N in the position code is in the open state, and the sub-control valve 24 corresponding to each four-way nozzle 1 with i>N is in the closed state.

[0076] In the scheme of this embodiment, under the specified gas flow rate condition, by gradually reducing the number of layers of the opened four-way nozzles 1, the effect of the change in the number of layers on the dust prevention effect of the vertical pipeline is tested and analyzed to determine the optimal number of opened layers of the four-way nozzles 1 under each gas flow rate. Specifically, Figure 6 As shown, the method to construct the required flow rate-layer number mapping through testing is as follows:

[0077] (1) At the specified gas flow rate V, turn on the four-way nozzles 1 of all layers and start the test. During the test, gas containing powder is introduced into the vertical pipe, and the powder contamination amount m0 ​​in the vertical pipe is counted after the specified time. After the test, the inner wall of the vertical pipe is cleaned; the ventilation test under the current number of layers is completed.

[0078] (2) Close the four-way nozzle 1 at the bottom layer of the vertical pipeline, repeat the above ventilation test, count the powder contamination amount m1 in the vertical pipeline after closing one layer, and calculate the powder contamination growth rate of the two ventilation tests. q t :

[0079] ,

[0080] In the above formula, m t and m t-1 Respectively indicate closing t Layer and t -1 layer four-way nozzle 1, the amount of powder contamination in the vertical pipeline in the experiment.

[0081] (3) Repeat step (2) to conduct the next round of testing until the growth rate of powder contamination in the current round of testing is q t Exceeds the preset growth rate threshold q0.

[0082] At this time, the number of layers of the four-way nozzle 1 that was kept open in the previous round is taken as the optimal number of layers under the current gas flow rate V.

[0083] (4) Repeat steps (1) to (3) to test the optimal number of layers of the four-way sprinkler 1 that should remain open under all flow rate conditions, and establish the required flow rate layer mapping.

[0084] 2. Cleaning Mode

[0085] In the dust prevention mode, each four-way nozzle 1 will spray gas to the four adjacent four-way nozzles 1. Any two adjacent four-way nozzles 1 will spray gas in opposite directions and equal sizes to each other, so the two will form a converging airflow pointing to the middle of the pipe at the middle boundary position. In this case, the position where each four-way nozzle 1 connects to the pipe wall will form a "dead corner" where dust is easily accumulated. Once some dust particles that pass through the air curtain reach this position, they are easily contaminated. In order to remove the dust contamination in these dead corners in each calibration experiment, this embodiment adds a cleaning mode to the purge device. In the cleaning mode, the four-way nozzle 1 will spray gas to the surrounding four directions in a more intense spray state, and the gas it sprays should be able to blow away the dust accumulated on the adjacent four-way nozzles 1. In order to avoid the airflows sprayed by different four-way nozzles 1 from causing relevant interference and suppressing their dust removal and cleaning effects. The controller of this embodiment turns on different four-way nozzles 1 alternately in the cleaning mode, thereby ensuring that when each four-way nozzle 1 is turned on, the four adjacent four-way nozzles 1 will remain closed.

[0086] Specifically, in the cleaning mode, the controller issues instructions to the main control valve 22 and each sub-control valve 24, and alternately controls each four-way nozzle 1 to spray background gas at the maximum flow rate in a preset order to complete pipeline cleaning. Among them, the maximum flow rate of the background gas sprayed by the four-way nozzle 1 satisfies: when each four-way nozzle 1 sprays the background gas at the preset maximum flow rate, the pressure generated at d away from the nozzle is not lower than the preset second pressure threshold P2. The second pressure threshold in this embodiment is actually the wind pressure that can blow off the dust accumulated on each four-way nozzle 1. That is: the pressure of the airflow sprayed by each four-way nozzle will gradually decay after leaving the nozzle, but after the sprayed airflow reaches the adjacent four-way nozzle 1, the airflow can still blow off the dust on the four-way nozzle 1.

[0087] In order to ensure that the airflows sprayed by each four-directional nozzle 1 do not interfere with each other and to maximize the coverage area in each round of spraying, the order of alternately opening different four-directional nozzles 1 in this embodiment is as follows: divide all four-directional nozzles 1 at even positions in odd layers and odd positions in even layers into the first zone, and divide all four-directional nozzles 1 at odd positions in odd layers and even positions in even layers into the second zone; then alternately open all four-directional nozzles 1 in the first zone and the second zone. For example, a vertical pipeline is installed with 4 layers of four-directional nozzles 1, and the number of four-directional nozzles 1 on each layer is 4. In the opening strategy of the four-directional nozzles 1 in this embodiment, if Figure 7As shown, when the four nozzles in the first zone are turned on, the surfaces of the four-directional nozzles 1 in the second zone will be swept by the airflows sprayed by the four-directional nozzles 1 in the first zone. When the four nozzles in the second zone are turned on, the surfaces of the four-directional nozzles 1 in the first zone will also be swept by the airflows sprayed by the four-directional nozzles 1 in the second zone. By alternately turning on the four-directional nozzles 1 in the first zone and the second zone, a micro-cyclone is formed in the vertical pipe, and then the dust in the "dead corner" of each four-directional nozzle 1 is blown back to the center of the vertical pipe. After the dust falls naturally, the inner wall of the vertical pipe is self-cleaned.

[0088] In this embodiment, in addition to using the purge device of this embodiment to prevent dust contamination, a nano-coating for preventing dust contamination can be further provided on the inner wall of the vertical pipe. It should be noted that the dust-proof principle of the nano-coating is to change the microscopic surface features of the inner wall of the vertical pipe, thereby reducing the probability of contamination when particles contact the pipe wall. However, in actual applications, once the nano-coating is contaminated, these special microstructures will also be destroyed, and the probability of contamination of the pipe wall will be significantly increased. The purge device provided in this embodiment can produce good synergy with the nano-coating. For example, under conditions of slight contamination, this embodiment can effectively remove the dust by using the self-cleaning effect of the purge device in the cleaning mode, thereby avoiding the deterioration of the dust-proof performance of the nano-coating.

[0089] It should be emphasized that the four-way nozzle 1 in the purge device constructed in this embodiment adopts a cubic rectifier block 12. In other embodiments, the rectifier block 12 may also adopt other shapes, such as Figure 8 Further, in this embodiment, the rectifier block 12 can be configured as follows: Fig. 9 The four-sided pyramid shown in the figure has nozzles arranged at the four triangular faces of the four-sided pyramid. The slope formed by the triangular faces of the four-sided pyramid is less likely to accumulate dust than the horizontal platform at the top of the cube, thereby reducing the influence of the dead angle formed by each four-way nozzle 1 on the dust-proof performance of the vertical pipeline. Based on the same design concept, in other embodiments, the rectifier block 12 can also be designed as a hemispherical shape. These simple adjustments made on the basis of the scheme of this embodiment should still be part of the overall concept of the scheme of this embodiment.

[0090] Example 2

[0091] Based on the solution of Example 1, this embodiment further provides a dust concentration sensor calibration system, which is used to calibrate the dust concentration sensor. The calibration system includes: a calibration pipeline, a dust generator, a purge device, a flow rate sensor and a host computer.

[0092] The calibration pipeline is a vertically placed pipeline with an open bottom, and a plurality of through holes distributed in an annular pattern are arranged on the wall of the calibration pipeline. The dust generator is used to introduce background gas mixed with a specified powder into the calibration pipeline along the upper opening.

[0093] The purging device adopts the purging device for mitigating powder contamination in the vertical pipeline as in Example 1. Each four-way nozzle 1 in the purging device is respectively installed at each through hole on the wall of the calibration pipeline, and is used to spray background gas into the calibration pipeline. The gas distribution device 2 and the controller in the purging device are installed outside the calibration pipeline.

[0094] The flow rate sensor and the dust concentration sensor to be calibrated are both fixed in the calibration pipeline near the lower opening. The flow rate sensor is used to measure the gas flow rate in the pipeline near the dust concentration sensor.

[0095] The host computer is electrically connected to the dust generator, the purge device, the flow rate sensor and the dust concentration sensor to be calibrated. The host computer is used to obtain the dust loss rate of the dust generator in real time during the calibration experiment. M , gas flow rate V And the detection signal of the dust concentration sensor A , then according to M , V And the cross-sectional area of ​​the pipe S Calculate the dust concentration in the calibration pipeline C , the calculation formula is:

[0096] .

[0097] On this basis, a series of related detection signals can be obtained A Dust concentration C . Using these A and C The mapping relationship between the two data pairs established can realize the recalibration of the dust concentration sensor.

[0098] However, combined with the above formula, it can be found that since the M value in the existing calibration system is calculated based on the material consumption of the dust generator, once the vertical pipe in the calibration system is contaminated with dust, the material consumption of the dust generator will not be able to produce aerosols of corresponding concentration at the dust concentration sensor at the bottom of the pipe. The dust mass corresponding to the dust concentration in the detection environment at the dust concentration sensor should be equal to the material consumption of the dust generator minus the dust accumulation on the pipe wall. That is: the dust contamination on the wall of the vertical pipe will cause the M value in the above formula to be higher than the actual value, which will lead to a large error in the calibration process.

[0099] Based on the calibration system described above, this embodiment further provides a calibration method for a dust concentration sensor, which is used to use the calibration system to calibrate the dust concentration sensor more accurately.

[0100] Specifically, Fig.10 As shown, the calibration method provided in this embodiment includes the following steps:

[0101] Install the gas concentration sensor to be calibrated in the calibration system of the dust concentration sensor as mentioned above; then automatically implement the following process under the control of the host computer:

[0102] (1) Control the dust generator to introduce dust-free background gas into the calibration pipeline at a preset flow rate.

[0103] (2) According to the gas flow rate in the calibration pipeline, the purge device is controlled to operate in dust prevention mode, and background gas is sprayed into the calibration pipeline to form an air curtain on the pipeline wall. The air curtain can effectively isolate dust particles, so that all the dust sprayed by the dust generator can be used to generate uniformly dispersed aerosol at the dust concentration sensor.

[0104] (3) Control the dust generator to introduce background gas containing dust with gradually increasing dust concentration into the calibration pipeline, and record the dust loss rate in real time M , gas flow rate V And the detection signal of the dust concentration sensor A .

[0105] (4) Using multiple sets of dust concentrations C With detection signal A A data pair is obtained to establish a mapping relationship between the output signal of the dust concentration sensor and the measured dust concentration detection result and send it to the dust concentration sensor for calibration.

[0106] (5) Turn off the dust generator and dust concentration sensor; control the purge device to operate in the cleaning mode, and the four-way nozzles 1 of each layer or column alternately spray background gas to complete the dust cleaning of the inner wall of the pipeline.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A purge device for reducing powder contamination in a vertical pipeline, characterized in that: It includes: A plurality of four-directional nozzles are installed on the wall of the vertical pipeline to be purged and are used to spray air into the pipeline; the four-directional nozzles are arranged in a grid on the wall of the vertical pipeline, and each four-directional nozzle has a unique layer code and bit code; each of the four-directional nozzles includes four nozzles, wherein the spraying directions of two nozzles are along the axial direction of the pipeline, and the spraying directions of the other two nozzles are along the tangential direction of the pipeline; A gas distribution instrument, comprising a gas source, a main control valve, a manifold block, a plurality of sub-control valves and a plurality of gas pipes; the gas source stores background gas in a high-pressure state; the main control valve is connected to the outlet of the gas source and is used to manage the flow of the background gas discharged from the gas source; the outlet of the main control valve is connected to the inlet of the manifold block; the plurality of outlets of the manifold block are connected to the respective four-way nozzles through independent gas pipes and sub-control valves; the sub-control valves are used to manage the opening and closing of the respective four-way nozzles; A controller is electrically connected to the main control valve and the sub-control valve, and is used to: (1) in the dust prevention mode, obtain the gas flow rate V at the dust concentration sensor in the vertical pipeline, query a preset "flow rate-number of layers mapping", and then issue instructions to the main control valve and each sub-control valve according to the query result, control all four-way nozzles of the specified layer to spray background gas into the vertical pipeline at a preset standard flow rate, so as to form an air curtain on the inner wall of the vertical pipeline that can prevent dust contamination; (2) in the cleaning mode, issue instructions to the main control valve and each sub-control valve, and alternately control each four-way nozzle to spray background gas at a maximum flow rate in a preset order to complete pipeline cleaning.

2. The purging device for alleviating powder contamination in a vertical pipeline according to claim 1, characterized in that: In the dust prevention mode, the controller opens the sub-control valves of all four-way sprinklers on the specified layer, and then dynamically adjusts the opening of the main control valve according to the number of layers of the opened four-way sprinklers; In the cleaning mode, the controller opens the main control valve to the maximum, and then opens the sub-control valves of the four-way nozzles at the even positions in all odd layers and the odd positions in the even layers alternately, and the sub-control valves of the four-way nozzles at the odd positions in all odd layers and the even positions in the even layers.

3. The purging device for alleviating powder contamination in a vertical pipeline according to claim 2, characterized in that: The distance between each four-way sprinkler and the four adjacent four-way sprinklers is equal, denoted as d ; The distance between adjacent four-way sprinklers d Satisfies: when each four-way nozzle sprays background gas at a preset standard flow rate, the pressure generated at a distance of 1 / 2d away from the nozzle is not higher than a preset first pressure threshold value P1.

4. The purging device for alleviating powder contamination in a vertical pipeline according to claim 3, characterized in that: The maximum flow rate of the background gas sprayed by the four-way nozzle satisfies that when each four-way nozzle sprays the background gas at the preset maximum flow rate, the pressure generated at a point d away from the nozzle is not lower than a preset second pressure threshold value P2.

5. The purging device for alleviating powder contamination in a vertical pipeline according to claim 1, characterized in that: The method for constructing the flow velocity-layer number mapping is as follows: (1) At the specified gas flow rate V, turn on the four-way nozzles of all layers and start the test. During the test, gas containing powder is introduced into the vertical pipe, and the powder contamination amount m0 ​​in the vertical pipe after the specified time is counted; after the test, clean the inner wall of the vertical pipe; complete the ventilation test under the current number of layers; (2) Close the four-way nozzle of the bottom layer of the vertical pipeline that has been opened, repeat the above ventilation test, count the powder contamination amount m1 in the vertical pipeline after closing one layer, and calculate the growth rate of powder contamination amount of the two ventilation tests q t : ， In the above formula, m t and m t-1 Respectively indicate closing t Layer and t -1 layer of four-way nozzles, the amount of powder contamination in the vertical pipe during the experiment; (3) Repeat step (2) to conduct the next round of testing until the growth rate of powder contamination in the current round of testing is q t Exceeding the preset growth rate threshold q0; At this time, the number of layers of the four-way nozzles that remained open in the previous round is taken as the optimal number of layers under the current gas flow rate V; (4) Repeat steps (1) to (3) to test the optimal number of layers of the four-way sprinkler that should be kept open under all flow rate conditions, and establish the required flow rate layer mapping.

6. The purging device for alleviating powder contamination in a vertical pipeline according to claim 1, characterized in that: A nano coating for preventing dust from contaminating is arranged on the inner wall of the vertical pipe.

7. The purging device for alleviating powder contamination in a vertical pipeline according to claim 6, characterized in that: The four-way nozzle is composed of an air pipe joint and a rectifier block, the rectifier block is in a cubic shape and has a spherical cavity in the center; one side of the rectifier block is provided with a connecting hole for connecting the air pipe joint and communicating with the spherical cavity; the four surfaces connected to the surface with the connecting hole are provided with injection holes communicating with the spherical cavity; one end of the air pipe joint is used to connect the air pipe, and the other end is a connector for sealingly connecting with the connecting hole of the rectifier block.

8. The purging device for alleviating powder contamination in a vertical pipeline according to claim 7, characterized in that: The air pipe joint is threadedly connected to the rectifier block; the connection hole of the rectifier block is provided with an internal thread; one end of the connection head of the air pipe joint is provided with an external thread; and / or In the rectifier block, a conical cavity connected to the spherical cavity is provided on the other side opposite to the connecting hole as a buffer zone.

9. A dust concentration sensor calibration system, characterized in that: It is used to calibrate the dust concentration sensor; the calibration system includes: The calibration pipe is a pipe placed vertically and open at the bottom, and a plurality of through holes distributed in an annular pattern are arranged on the pipe wall of the calibration pipe; A dust generator, which is used to introduce background gas mixed with specified powder into the calibration pipeline along the upper opening; A purging device, which adopts the purging device for mitigating powder contamination in a vertical pipeline as described in any one of claims 1 to 8, wherein each four-way nozzle in the purging device is respectively installed at each through hole on the wall of the calibration pipeline, and is used to spray background gas into the calibration pipeline; the gas distribution instrument and controller in the purging device are located outside the calibration pipeline; A flow rate sensor, which together with the dust concentration sensor to be calibrated is fixed in the calibration pipe near the lower opening; the flow rate sensor is used to measure the gas flow rate in the pipe near the dust concentration sensor; A host computer, which is electrically connected to the dust generator, the purge device, the flow rate sensor and the dust concentration sensor to be calibrated; the host computer is used to obtain the dust loss rate of the dust generator in real time during the calibration experiment M , gas flow rate V And the detection signal of the dust concentration sensor A , then according to M , V And the cross-sectional area of ​​the pipe S Calculate the dust concentration in the calibration pipeline C , and then in C and A Create a mapping between them.

10. A method for calibrating a dust concentration sensor, characterized in that: It includes: The gas concentration sensor to be calibrated is installed in the calibration system of the dust concentration sensor as claimed in claim 9; and then the following process is automatically implemented under the control of the host computer: (1) Control the dust generator to introduce dust-free background gas into the calibration pipeline at a preset flow rate; (2) controlling the purge device to operate in a dust prevention mode according to the gas flow rate in the calibration pipeline, spraying background gas into the calibration pipeline to form an air curtain on the pipeline wall; (3) Control the dust generator to introduce background gas containing dust and gradually increasing dust concentration into the calibration pipeline, and record the dust loss rate in real time M , gas flow rate V And the detection signal of the dust concentration sensor A ; (4) Using multiple sets of dust concentrations C With detection signal A A mapping relationship between the output signal of the dust concentration sensor and the obtained dust concentration detection result is established based on the data pair, and the data pair is sent to the host computer for calibration of the dust concentration sensor; (5) Turn off the dust generator and the dust concentration sensor; control the purge device to operate in the cleaning mode, and the four-way nozzles in each layer or column alternately spray background gas to complete the dust cleaning of the inner wall of the pipeline.

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