Three-dimensional pitot tube flue gas on-line monitoring system and measuring method

Abstract

The invention relates to a three-dimensional pitot tube flue gas on-line monitoring system and a measuring method.The system comprises a flue gas collecting unit and a data processing and control unit, the flue gas collecting unit comprises n measuring probe rods and m measuring probes, each measuring probe rod comprises a main pipe and a flue gas sampling pipe, the front end of each measuring probe is hemispherical, and the front end of each measuring probe is connected with the corresponding main pipe; a plurality of pressure measuring holes are formed in the measuring probe; and the data processing and control unit comprises a sampling electromagnetic valve group, a gas distribution module, a pressure transmitter, a controller and an upper computer. According to the measurement method, the average flue gas flow velocity of the measurement section is calculated according to the pressure value of each measurement point in the polling measurement result and a flow velocity calculation database or a calculation curve preset in the upper computer. The device is more suitable for measuring the flow velocity of gas in three-dimensional turbulent motion, can realize online continuous multi-point monitoring of the flow velocity and flow of flue gas, and is simple to install, convenient to measure and high in measurement precision.

Description

Technical Field

[0001] The invention relates to a flue gas monitoring system, in particular to a three-dimensional pitot tube flue gas online monitoring system and a measuring method, belonging to the technical field of environmental detection. Background Art

[0002] Flue gas velocity and flow measurement technology is a measurement technology that has developed rapidly along with the global economic industrialization. It is used in exhaust gas emission detection, industrial process control, and improving equipment efficiency. It is closely related to energy conservation and environmental protection.

[0003] Traditional flue gas online detection systems are mainly implemented using S-type Pitot tubes or matrix flow meters. The S-type Pitot tube consists of a total pressure tube and a static pressure tube. The total pressure tube faces the airflow direction and is used to measure the total pressure of the gas, while the static pressure tube faces the back of the airflow direction and is used to measure the static pressure of the gas. The dynamic pressure is the total pressure minus the static pressure. The gas flow rate and flow are functions of the dynamic pressure, and the flue gas flow rate and flow can be calculated based on the dynamic pressure. The matrix flow meter has a similar measurement principle to the S-type Pitot tube, but the difference is that the matrix flow meter uses a multi-point measurement method, that is, multiple measuring points are arranged on a measuring section, and each measuring point is composed of two pressure taking tubes, a total pressure tube and a static pressure tube. However, the S-type Pitot tube or matrix flow meter is only suitable for gases with one-dimensional linear motion or approximately one-dimensional linear motion. The flow of gas in the actual flue is three-dimensional turbulent motion. Therefore, this monitoring method has low accuracy in measuring gas flow rate and flow rate. Moreover, the S-type Pitot tube or matrix flow meter can only monitor the size of the flue gas flow rate, but cannot measure the direction of the flow rate. Therefore, the measured parameters cannot accurately reflect the gas situation. The existing S-type Pitot tube or matrix flow meter has high requirements for the installation position. The equipment must be installed on a long straight pipe, that is, there must be a straight pipe section of 4 times the flue diameter in front of the instrument installation position, and there must be a straight pipe section of 2 times the flue diameter behind the instrument installation position. However, actual industrial flues often do not have such long straight pipe sections, which are not only difficult to install, but also difficult to construct.

[0004] In order to improve the measurement accuracy, the prior art also uses a portable three-dimensional Pitot tube for measurement. The three-dimensional Pitot tube adopts a three-dimensional vector velocity measurement method, has high measurement accuracy, and can maintain high measurement stability and measurement accuracy under complex and changeable flue gas conditions. However, this three-dimensional Pitot tube is only suitable for on-site manual comparison testing of flue gas flow rate. During the test, it is necessary to manually adjust the depth of the probe rod inserted into the flue and manually rotate the three-dimensional Pitot tube to make the pressures of two symmetrical pressure measuring holes on the measuring probe equal. The measurement process is cumbersome, the adaptability to working conditions is weak, the real-time measurement is poor, and this method can only measure the flow rate of a single measuring point, and cannot fully reflect the flue gas conditions in the flue. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a three-dimensional Pitot tube flue gas online monitoring system and measurement method, which is suitable for the gas flow velocity measurement of three-dimensional turbulent motion, and can realize online continuous multi-point monitoring of flue gas flow velocity and flow, with simple installation, convenient measurement and high measurement accuracy.

[0006] A three-dimensional pitot tube flue gas online monitoring system, comprising a flue gas collection unit and a data processing and control unit, the flue gas collection unit comprising n measuring probes, 1≤n≤10, each measuring probe being provided with m measuring probes along the axial direction, 1≤m≤10, the measuring probe being a three-dimensional pitot tube structure, the front end of the measuring probe being hemispherical, and a plurality of pressure measuring holes being arranged on the measuring probe, the measuring probe being arranged in the direction of the flue gas flow; the measuring probe comprising a main pipe and a flue gas sampling pipe, the flue gas sampling pipe being arranged inside the main pipe; the data processing and control unit comprising a sampling solenoid valve group, a gas distribution module, a pressure transmitter, a controller and a host computer, each measuring probe being provided with a plurality of pressure measuring holes arranged on the main pipe, and the flue gas sampling pipe ... m solenoid valve groups are set up accordingly, and each solenoid valve group includes solenoid valves with the same number as the pressure measuring holes. One end of the flue gas sampling tube is connected to the pressure measuring holes on each probe, and the other end is connected to the air inlets of the gas separation module through the solenoid valve. The air outlets of the gas separation module are respectively connected to the pressure transmitter. The pressure transmitter sends the pressure signal to the controller and the host computer. The host computer processes, calculates, stores and displays the data. The host computer is pre-set with an airflow angle database and an airflow total pressure and static pressure database. The database is established according to the total pressure value and static pressure value of the standard wind tunnel, and the pressure value, pitch angle α and yaw angle β of each pressure measuring hole under different wind speeds.

[0007] Furthermore, there are five pressure measuring holes on the measuring probe, including a central pressure measuring hole and a yaw pressure measuring hole and a pitch pressure measuring hole arranged in pairs. The two pitch pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are parallel to the axial direction of the measuring probe rod. The two yaw pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are perpendicular to the axial direction of the measuring probe rod.

[0008] Furthermore, the data processing and control unit also includes 5 sets of zeroing valves, and the gas distribution module has 5 pressure regulating gas circuits inside. The gas outlet of each zeroing valve is respectively connected to the gas inlet of the pressure regulating gas circuit in the gas distribution module, and the gas outlet of the pressure regulating gas circuit in the gas distribution module is respectively connected to the pressure transmitter. The pressure values ​​of the 5 pressure transmitters are zeroed through the zeroing valve and the pressure regulating gas circuit in the gas distribution module.

[0009] Furthermore, a temperature sensor is provided in the main pipe of each measuring probe, and the temperature sensor sends a temperature signal to the controller and the host computer.

[0010] Furthermore, it also includes a purge unit, which includes a purge solenoid valve, a compressed air source and a purge air circuit. Each probe rod is provided with a purge solenoid valve, and the purge air circuit includes a purge gas mother pipe and m purge gas branch pipes. The air inlet of the purge solenoid valve is connected to the compressed air source, the air outlet of the purge solenoid valve is connected to the purge gas mother pipe, and the air outlet of the purge branch pipe is respectively connected to the purge gas inlet of each sampling solenoid valve group.

[0011] Furthermore, when the measuring probe is installed in a rectangular flue and the length of the probe exceeds 4 meters, a limit rod is also provided in the flue, both ends of the limit rod are fixedly connected to the flue wall panel, a limit sleeve is provided at the relative position of the limit rod and the measuring probe, and the bottom end of the measuring probe is inserted into the sleeve of the limit rod.

[0012] A three-dimensional pitot tube flue gas online monitoring system measurement method, comprising the following steps:

[0013] S1, calibrate the measuring probe and the three-dimensional pitot tube in a standard wind tunnel, establish a velocity calculation database or calculation curve, and embed it into the host computer calculation software;

[0014] S2, the measuring probe is inserted into the flue or chimney, with the probe facing the direction of the flue gas flow. When inserted into a rectangular flue, the measuring points are distributed in a matrix form. When inserted into a circular chimney, the measuring points are distributed in a circular symmetrical manner with the circular cross section of the chimney as the center.

[0015] S3, open the zeroing valve, adjust the indication of all pressure transmitters to zero, and close the zeroing valve after the zeroing is completed;

[0016] S4, the measuring points on each probe are measured by patrol measurement, and the controller controls each solenoid valve group to be turned on and off in sequence, so that the pressure measuring hole on each probe is connected to the pressure transmitter in sequence;

[0017] S5, calculating and obtaining the average flue gas flow velocity of the measurement section according to the pressure value of each measurement point in the patrol measurement result and the velocity calculation database or calculation curve pre-set in the host computer.

[0018] Furthermore, the method for establishing a velocity calculation database or a calculation curve in S1 is as follows:

[0019] S11, installing a measuring probe equipped with a three-dimensional pitot tube measuring probe in a standard wind tunnel, and adjusting the pitch angle α and the yaw angle β of the airflow relative to the measuring probe in sequence under a set wind speed to obtain the pressure values ​​of each pressure measuring hole on the measuring probe under different airflow angle conditions;

[0020] S12, establishing an airflow angle calculation database or an airflow angle calculation curve according to the pitch angle α, the yaw angle β, and the pressure values ​​of each pressure measuring hole of the probe;

[0021] S13, under the set wind speed, a calculation database for total airflow pressure and static pressure or a calculation curve for total pressure and static pressure is established based on the total pressure, static pressure, pressure values ​​of each pressure measuring hole of the measuring probe, pitch angle α and yaw angle β of the standard wind tunnel;

[0022] S14, repeating the above S11 to S13 under different wind speed conditions;

[0023] S15, embedding the above database or calculation curve into the upper computer calculation software.

[0024] Furthermore, the step of obtaining the average flue gas flow velocity of the measurement section according to the patrol measurement results in S5 is as follows:

[0025] S51, each pressure value of the current measuring point measured by the measuring probe is sent to the host computer through the controller, and the airflow angle of the current measuring point, that is, the pitch angle α and the yaw angle β, is calculated according to the airflow angle calculation database or airflow angle calculation curve built into the host computer software;

[0026] S52, calculating the total pressure and static pressure of the airflow at the current measuring point according to the pressure values ​​of the current measuring point, the airflow pitch angle α and yaw angle β calculated in the previous step, and the airflow total pressure and static pressure calculation database or total pressure and static pressure calculation curve built into the host computer software;

[0027] S53, calculating the air flow pressure according to the total air flow pressure and the static pressure, and then calculating the air flow velocity at the front measuring point;

[0028] S54, repeating the above S51 to S53 to calculate the average value of the airflow velocity of all measuring points in a measurement cycle as the average flue gas flow velocity of the measurement section, and the average flue gas flow velocity is calculated and updated every time the airflow velocity of a measuring point is updated.

[0029] The system and method provided by the present invention have the following advantages:

[0030] 1) The measurement is carried out on the flue or chimney cross section in a grid-like arrangement of measuring points, and each measuring point uses a measuring probe with a three-dimensional pitot tube structure, which is more suitable for measuring the gas flow rate of three-dimensional turbulent motion and has high measurement accuracy;

[0031] 2) Automatic, continuous and real-time measurement can be achieved through the preset database or data curve in the host computer, and the flow velocity at each measuring point and the average flow velocity of the section can be monitored online;

[0032] 3) The present invention is easy to install. During measurement, there is no need to manually rotate the three-dimensional pitot tube probe. It only needs to be fixed roughly in the direction of the flue gas flow to perform continuous measurement.

[0033] 4) The present invention can not only measure the gas flow velocity, but also measure the direction angle of the flow velocity, and the measurement data is more accurate;

[0034] 5) The present invention is also provided with a timed automatic purge system, which can realize timed automatic purge of the flue gas collection tube and the measuring probe, and has good anti-blocking performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the system layout provided by the present invention;

[0036] Figure 2 A schematic diagram of a measuring probe provided by the present invention;

[0037] Figure 3 for Figure 2 A-direction enlarged schematic diagram;

[0038] Figure 4 This is the layout diagram of each measuring point in the rectangular flue;

[0039] Figure 5 for Figure 4 Enlarged schematic diagram of the AA section;

[0040] Figure 6 This is the layout diagram of each measuring point in the circular chimney;

[0041] In the figure: 1. Main pipe; 2. Nozzle; 3. Measuring probe; 4. Sampling gas pipe; 5. Temperature sensor; 6. Temperature signal cable; 7. Adapter box; 8. Pipe joint; 9. Aviation plug joint; 10. Sampling solenoid valve group; 11. Gas pipe I; 12. Gas distribution module; 13. Gas pipe II; 14. Pressure transmitter; 15. Zeroing valve; 16. Controller; 17. Pressure signal cable; 18. Temperature signal transmission cable; 19. Host computer; 20. Communication cable; 21. Purge solenoid valve; 22. Purge gas main pipe; 23. Purge gas branch pipe; 24. Control cable; 25. Limit rod; 26. Limit sleeve. DETAILED DESCRIPTION

[0042] In order to explain the present invention more clearly, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0043] like Figure 1As shown, a three-dimensional pitot tube flue gas online monitoring system includes a flue gas collection unit and a data processing and control unit. The flue gas collection unit includes n measuring probes, 1≤n≤10, each measuring probe is provided with m measuring probes 3 along the axial direction, 1≤m≤10, the measuring probe 3 is a three-dimensional pitot tube structure, the front end of the measuring probe is hemispherical, and a plurality of pressure measuring holes are arranged on the measuring probe, and the measuring probe is arranged toward the flue gas flow direction; the measuring probe includes a main pipe 1 and a flue gas sampling pipe 4, and the flue gas sampling pipe 4 is arranged inside the main pipe 1; the data processing and control unit includes a sampling solenoid valve group 10, a gas distribution module 12, a pressure transmitter 14, a controller 16 and a host computer 19, and each measuring probe is for m solenoid valve groups 10 should be set up, each solenoid valve group 10 includes solenoid valves with the same number as the pressure measuring holes. One end of the smoke sampling tube 4 is connected to the pressure measuring holes on each probe, and the other end is connected to the air inlets of the gas separation module 12 through the solenoid valve. The air outlets of the gas separation module 12 are respectively connected to the pressure transmitter 14. The pressure transmitter 14 sends the pressure signal to the controller 16 and the host computer 19. The host computer 19 processes, calculates, stores and displays the data. The host computer 19 is pre-set with an airflow angle database and an airflow total pressure and static pressure database. The database is established based on the total pressure value and static pressure value of the standard wind tunnel, as well as the pressure value, pitch angle α and yaw angle β of each pressure measuring hole under different wind speeds.

[0044] like Figure 1 and Figure 2 As shown, in this embodiment, the position where the measuring probe is set on the main pipe has a nozzle 2, the main pipe 1 is a steel pipe with a diameter of 20-120 mm, the nozzle 2 is a steel pipe with a thread or a smooth steel pipe, the nozzle 2 is welded to the main pipe 1, the front part of the measuring probe 3 is hemispherical, the rear part is cylindrical, the ball head diameter is 10-50 mm, the measuring probe 3 is connected to the nozzle 2 by a thread, or the measuring probe 3 is inserted into the nozzle 2 and then fixed by a screw. One end of the flue gas sampling air pipe 4 placed in the main pipe 1 is connected to each pressure measuring hole on the measuring probe 3, and the other end is connected to each pipe joint 8 in the adapter box 7 arranged on the top of the measuring probe rod; the pipe joint 8 is connected to the air inlet of the sampling solenoid valve group 10 through the air supply pipe I11; the air outlet of the sampling solenoid valve group 10 is connected to the air inlet of the gas distribution module 12 through the air supply pipe II13, and each air outlet of the gas distribution module 12 is respectively connected to the air inlet of the pressure transmitter 14, the pressure transmitter 14 is connected to the controller 16 through the pressure signal cable 17, and the controller 16 is connected to the host computer 19 through the communication cable 20.

[0045] like Figure 3As shown, there are five pressure measuring holes on the measuring probe 3, including a central pressure measuring hole and a yaw pressure measuring hole and a pitch pressure measuring hole arranged in pairs. The two pitch pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are parallel to the axial direction of the measuring probe rod. The two yaw pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are perpendicular to the axial direction of the measuring probe rod.

[0046] In the present embodiment, three measuring probes are provided, each measuring probe is provided with three measuring probes 3 along the axial direction, and the number of pressure measuring holes on each measuring probe 3 is set to five, so 15 flue gas sampling tubes 4 are provided in each corresponding measuring probe, and three solenoid valve groups are provided correspondingly to each measuring probe, and each solenoid valve group includes five solenoid valves, which are respectively used to control the on-off of the gas path between the flue gas sampling tube 4 on each probe and the gas separation module 12. The gas separation module 12 has 45 air inlets for flue gas collection and five air outlets, which are respectively connected to five pressure transmitters 14 for respectively measuring the pressure values ​​of the five pressure measuring holes on each probe.

[0047] The data processing and control unit also includes 5 groups of zeroing valves 15. The gas distribution module 14 has 5 pressure regulating gas circuits inside. The outlet of each zeroing valve 15 is respectively connected to the air inlet of the pressure regulating gas circuit in the gas distribution module 14, and the outlet of the pressure regulating gas circuit in the gas distribution module is respectively connected to the pressure transmitter.

[0048] The pressure values ​​of the five pressure transmitters 14 are adjusted to zero through the zero adjustment valve 15 and the pressure regulating gas circuit in the gas distribution module 12 .

[0049] A temperature sensor 5 is also provided in the main pipe of each measuring probe, and the temperature sensor 5 sends a temperature signal to the controller 16 and the host computer 19 .

[0050] In this embodiment, Figure 1 As shown, the temperature sensor 5 and the temperature signal cable 6 can be placed in the main pipe 1, one end of the temperature signal cable 6 is connected to the temperature sensor 5, and the other end is connected to the aviation plug connector 9 on the adapter box 7, and the aviation plug connector 9 is connected to the controller 16 through the temperature signal transmission cable 18.

[0051] The monitoring system also includes a purge unit, which includes a purge solenoid valve 21, a compressed air source and a purge air circuit. Each probe rod is provided with a purge solenoid valve, and the purge air circuit includes a purge gas mother pipe 22 and m purge gas branch pipes 23. The air inlet of the purge solenoid valve 21 is connected to the compressed air source, the air outlet of the purge solenoid valve 21 is connected to the purge gas mother pipe 22, and the air outlet of the purge branch pipe 23 is respectively connected to the purge gas inlet of each sampling solenoid valve group.

[0052] When the measuring probe needs to be purged, the controller can be used to control the purge solenoid valve 21 and the sampling solenoid valve group 10 corresponding to the measuring probe to open, and the compressed gas passes through the purge solenoid valve 21, the purge gas main pipe 22, the purge gas branch pipe 23, the sampling solenoid valve group 10, and the flue gas sampling tube 4 to purge the corresponding pressure measuring hole on the probe to prevent the pressure measuring hole from being blocked by smoke. The purge solenoid valve 21 is connected to the controller 16 through a control cable 24. The purge also adopts a patrol purge mode, that is, after one measuring probe is purged, the other measuring probes are purged in turn. After each measurement cycle or multiple cycles, the system enters the measurement and purge mode, and the system automatically purges the probes that do not have any probes in the measurement state.

[0053] like Figure 4 and Figure 5 As shown, when installed in a rectangular flue and the length of the probe rod exceeds 4 meters, a limit rod 25 is also provided in the flue, and both ends of the limit rod 25 are fixedly connected to the flue wall panels. A limit sleeve 26 is provided at the relative position of the limit rod and the measuring probe rod, and the bottom end of the measuring probe rod is inserted into the limit sleeve 26.

[0054] The limit rod 25 can limit the swing amplitude of the longer measuring probe rod, and the measuring probe rod can also be slightly shaken in the limit sleeve 26 to automatically remove dust in the probe.

[0055] A three-dimensional pitot tube flue gas online monitoring system measurement method, comprising the following steps:

[0056] S1, calibrate the measuring probe and the three-dimensional pitot tube in a standard wind tunnel, establish a velocity calculation database or calculation curve, and embed it into the host computer calculation software;

[0057] S2, the measuring probe is inserted into the flue or chimney, with the probe facing the direction of the flue gas flow. When inserted into a rectangular flue, the measuring points are distributed in a matrix form. When inserted into a circular chimney, the measuring points are distributed in a circular symmetrical manner with the circular cross section of the chimney as the center. Figure 4 and Figure 6 As shown, a pre-buried flange is provided on the top of the flue or the side wall of the chimney, and the flange on the top of the measuring point probe is fixed to the pre-buried flange by bolts;

[0058] like Figure 4 As shown, from left to right, the measuring probes are defined as probe No. 1, probe No. 2, and probe No. 3, and the measuring points on probe No. 1 are defined as measuring point 1-1, measuring point 1-2, and measuring point 1-3 from top to bottom; the measuring points on probe No. 2 are defined as measuring point 2-1, measuring point 2-2, and measuring point 2-3 from top to bottom; and the measuring points on probe No. 3 are defined as measuring point 3-1, measuring point 3-2, and measuring point 3-3 from top to bottom.

[0059] For example, during measurement, the solenoid valve group connected to the measuring point 1-1 is powered on and opened, so that the 5 pressure measuring holes on the measuring probe of the measuring point 1-1 are connected to the 5 pressure transmitters. The controller collects the 5 pressure values ​​of the measuring point 1-1 and transmits them to the host computer. The calculation software in the host computer automatically calculates the flue gas parameter values ​​such as the flow velocity, flow velocity direction angle, flue gas static pressure, and total flue gas pressure at the measuring probe of the measuring point 1-1 according to the measured 5 pressure values ​​and flue gas temperature, and displays them on the screen of the host computer and stores them in the host computer at the same time. After a certain time interval, the solenoid valve group connected to the measuring point 1-1 is closed, and the solenoid valve group connected to the measuring point 1-2 is opened, and the 5 pressure measuring holes of the measuring probe of the measuring point 1-2 are connected to the 5 pressure transmitters. The system automatically calculates the flue gas parameter values ​​at the measuring probe of the measuring point 1-2, and displays them on the screen of the host computer and stores them in the host computer at the same time. It is a cycle until all the measuring points are completed.

[0060] Furthermore, the method for establishing a velocity calculation database or a calculation curve in S1 is as follows:

[0061] S11, installing a measuring probe equipped with a three-dimensional pitot tube measuring probe in a standard wind tunnel, and adjusting the pitch angle α and the yaw angle β of the airflow relative to the measuring probe in sequence under a set wind speed to obtain the pressure values ​​of each pressure measuring hole on the measuring probe under different airflow angle conditions;

[0062] S12, establishing an airflow angle calculation database or an airflow angle calculation curve according to the pitch angle α, the yaw angle β, and the pressure values ​​of each pressure measuring hole of the probe;

[0063] S13, under the set wind speed, a calculation database for total airflow pressure and static pressure or a calculation curve for total pressure and static pressure is established based on the total pressure, static pressure, pressure values ​​of each pressure measuring hole of the measuring probe, pitch angle α and yaw angle β of the standard wind tunnel;

[0064] S14, repeating the above S11 to S13 under different wind speed conditions;

[0065] S15, embedding the above database or calculation curve into the upper computer calculation software.

[0066] Specifically, the steps of obtaining the average flue gas velocity of the measurement section according to the patrol measurement results in S5 are as follows:

[0067] S51, each pressure value of the current measuring point measured by the measuring probe is sent to the host computer through the controller, and the airflow angle of the current measuring point, that is, the pitch angle α and the yaw angle β, is calculated according to the airflow angle calculation database or airflow angle calculation curve built into the host computer software;

[0068] S52, calculating the total pressure and static pressure of the airflow at the current measuring point according to the pressure values ​​of the current measuring point, the airflow pitch angle α and yaw angle β calculated in the previous step, and the airflow total pressure and static pressure calculation database or total pressure and static pressure calculation curve built into the host computer software;

[0069] S53, calculating the air flow pressure according to the total air flow pressure and the static pressure, and then calculating the air flow velocity at the front measuring point;

[0070] S54, repeating the above S51 to S53 to calculate the average value of the airflow velocity of all measuring points in a measurement cycle as the average flue gas flow velocity of the measurement section, and the average flue gas flow velocity is calculated and updated every time the airflow velocity of a measuring point is updated.

[0071] The present invention adopts a measuring probe with a three-dimensional Pitot tube structure, which is more suitable for measuring the gas flow rate of three-dimensional turbulent motion, and can realize automatic, continuous and real-time measurement through a database or data curve preset in a host computer, and automatically monitor the flow rate of each measuring point in the measuring section and the average flow rate of the section; the present invention is simple to install, and there is no need to manually rotate the three-dimensional Pitot tube probe during measurement. It only needs to be fixed roughly in the direction of the flue gas flow to perform continuous measurement, and not only the size of the gas flow rate can be measured, but also the direction angle of the flow rate can be measured; the present invention is also provided with a timed automatic purge system, which can realize timed automatic purge of the flue gas collection tube and the measuring probe, and has good anti-blocking performance.

[0072] Those skilled in the art should understand that, in the description of the present invention, it is necessary to understand that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0073] In the present invention, unless otherwise clearly stipulated and limited, for example, it can be a fixed connection, a detachable connection, or an integrated one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0074] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. For ordinary technicians in this field, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A three-dimensional pitot tube flue gas online monitoring system, comprising a flue gas collection unit and a data processing and control unit, wherein the flue gas collection unit comprises n measuring probes, 1≤n≤10, each measuring probe is provided with m measuring probes along the axial direction, 1≤m≤10, and characterized in that: The measuring probe is a three-dimensional pitot tube structure, the front end of the measuring probe is hemispherical, and a plurality of pressure measuring holes are arranged on the measuring probe, and the measuring probe is arranged in the direction of the flue gas flow; the measuring probe includes a main pipe and a flue gas sampling pipe, and the flue gas sampling pipe is arranged inside the main pipe; the data processing and control unit includes a sampling electromagnetic valve group, a gas distribution module, a pressure transmitter, a controller and a host computer, each measuring probe is correspondingly provided with m electromagnetic valve groups, each electromagnetic valve group includes electromagnetic valves with the same number as the pressure measuring holes, one end of the flue gas sampling tube is connected with the pressure measuring holes on each probe, and the other end is connected with each air inlet of the gas distribution module through the electromagnetic valve, each air outlet of the gas distribution module is respectively connected with the pressure transmitter, the pressure transmitter sends the pressure signal to the controller and the host computer, and the host computer processes, calculates, stores and displays the data, wherein the host computer is pre-set with an airflow angle database and an airflow total pressure and static pressure database, and the database is established according to the total pressure value and static pressure value of the standard wind tunnel, and the pressure value, pitch angle α and yaw angle β of each pressure measuring hole under different wind speeds.

2. The three-dimensional pitot tube flue gas online monitoring system according to claim 1 is characterized in that: There are five pressure measuring holes on the measuring probe, including a central pressure measuring hole and a yaw pressure measuring hole and a pitch pressure measuring hole arranged in pairs. The two pitch pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are parallel to the axial direction of the measuring probe rod. The two yaw pressure measuring holes are symmetrically arranged with the central pressure measuring hole as the center and the connecting lines are perpendicular to the axial direction of the measuring probe rod.

3. The three-dimensional pitot tube flue gas online monitoring system according to claim 2 is characterized in that: The data processing and control unit also includes 5 sets of zeroing valves. The gas distribution module has 5 pressure regulating gas circuits inside. The gas outlet of each zeroing valve is connected to the gas inlet of the pressure regulating gas circuit in the gas distribution module. The gas outlet of the pressure regulating gas circuit in the gas distribution module is connected to the pressure transmitter. The pressure values ​​of the 5 pressure transmitters are adjusted to zero through the zeroing valve and the pressure regulating gas circuit in the gas distribution module.

4. The three-dimensional pitot tube flue gas online monitoring system according to claim 1 is characterized in that: A temperature sensor is also provided in the main pipe of each measuring probe, and the temperature sensor sends a temperature signal to the controller and the host computer.

5. The three-dimensional pitot tube flue gas online monitoring system according to claim 1 is characterized in that: It also includes a purge unit, which includes a purge solenoid valve, a compressed air source and a purge air circuit. Each probe rod is provided with a purge solenoid valve, and the purge air circuit includes a purge gas mother pipe and m purge gas branch pipes. The air inlet of the purge solenoid valve is connected to the compressed air source, the air outlet of the purge solenoid valve is connected to the purge gas mother pipe, and the air outlet of the purge branch pipe is respectively connected to the purge gas inlet of each sampling solenoid valve group.

6. The three-dimensional pitot tube flue gas online monitoring system according to any one of claims 1 to 5, characterized in that: When the measuring probe is installed in a rectangular flue and the length of the probe exceeds 4 meters, a limit rod is also provided in the flue. Both ends of the limit rod are fixedly connected to the flue wall panels. A limit sleeve is provided at the relative position of the limit rod and the measuring probe, and the bottom end of the measuring probe is inserted into the sleeve of the limit rod.

7. A three-dimensional pitot tube flue gas online monitoring system measurement method, characterized in that: The following steps are involved: S1, calibrate the measuring probe and the three-dimensional pitot tube in a standard wind tunnel, establish a velocity calculation database or calculation curve, and embed it into the host computer calculation software; S2, the measuring probe is inserted into the flue or chimney, with the probe facing the direction of the flue gas flow. When inserted into a rectangular flue, the measuring points are distributed in a matrix form. When inserted into a circular chimney, the measuring points are distributed in a circular symmetrical manner with the circular cross section of the chimney as the center. S3, open the zeroing valve, adjust the indication of all pressure transmitters to zero, and close the zeroing valve after the zeroing is completed; S4, the measuring points on each probe are measured by patrol measurement, and the controller controls each solenoid valve group to be turned on and off in sequence, so that the pressure measuring hole on each probe is connected to the pressure transmitter in sequence; S5, calculating and obtaining the average flue gas flow velocity of the measurement section according to the pressure value of each measurement point in the patrol measurement result and the velocity calculation database or calculation curve pre-set in the host computer.

8. The three-dimensional pitot tube flue gas online monitoring system measurement method according to claim 7 is characterized in that: The method for establishing a velocity calculation database or calculation curve in S1 is as follows: S11, installing a measuring probe equipped with a three-dimensional pitot tube measuring probe in a standard wind tunnel, and adjusting the pitch angle α and the yaw angle β of the airflow relative to the measuring probe in sequence under a set wind speed to obtain the pressure values ​​of each pressure measuring hole on the measuring probe under different airflow angle conditions; S12, establishing an airflow angle calculation database or an airflow angle calculation curve according to the pitch angle α, the yaw angle β, and the pressure values ​​of each pressure measuring hole of the probe; S13, under the set wind speed, a calculation database for total airflow pressure and static pressure or a calculation curve for total pressure and static pressure is established based on the total pressure, static pressure, pressure values ​​of each pressure measuring hole of the measuring probe, pitch angle α and yaw angle β of the standard wind tunnel; S14, repeating the above S11 to S13 under different wind speed conditions; S15, embedding the above database or calculation curve into the upper computer calculation software.

9. The three-dimensional pitot tube flue gas online monitoring system measurement method according to claim 8, characterized in that: The steps of obtaining the average flue gas velocity of the measurement section according to the patrol measurement results in S5 are as follows: S51, each pressure value of the current measuring point measured by the measuring probe is sent to the host computer through the controller, and the airflow angle of the current measuring point, that is, the pitch angle α and the yaw angle β, is calculated according to the airflow angle calculation database or airflow angle calculation curve built into the host computer software; S52, calculating the total pressure and static pressure of the airflow at the current measuring point according to the pressure values ​​of the current measuring point, the airflow pitch angle α and yaw angle β calculated in the previous step, and the airflow total pressure and static pressure calculation database or total pressure and static pressure calculation curve built into the host computer software; S53, calculating the air flow pressure according to the total air flow pressure and the static pressure, and then calculating the air flow velocity at the front measuring point; S54, repeating the above S51 to S53 to calculate the average value of the airflow velocity of all measuring points in a measurement cycle as the average flue gas flow velocity of the measurement section, and the average flue gas flow velocity is calculated and updated every time the airflow velocity of a measuring point is updated.

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