Air volume measuring device based on speed measuring fan

Abstract

The utility model provides an air volume measuring device based on a speed measuring fan. The air volume measuring device comprises at least one speed measuring fan, a rotating speed measuring unit and a monitoring and analyzing unit, wherein the speed measuring fan is arranged in the cross section of an air duct of a non-uniform wind field; the special-shaped steel frame is transversely arranged on the air duct wall of the cross section of the non-uniform wind field air duct; wherein the speed measuring fan is arranged in the cross section of the air duct of the non-uniform wind field by utilizing the special-shaped steel frame; the rotating speed measuring unit is electrically connected with the monitoring and analyzing unit; the speed measuring fan is an unpowered fan; speed measurement fans of the same specification or different specifications are uniformly distributed in the cross section of an air duct of a non-uniform wind field, torque is generated through the wind speed of the average fan blade surface and the plane of the speed measurement fans, and the average wind speed of the fan blade and the cross section is generated after weighted averaging is conducted through a rotating shaft of the speed measurement fans. The method has the advantages that the cost is low, the wind resistance is small, the measurement is accurate, the engineering is easy to implement, and the like.

Description

Technical Field

[0001] The utility model belongs to the technical field of wind volume measurement, and relates to a wind volume measurement device based on a speed measuring fan, in particular to a wind volume measurement device in a cross section of a non-uniform wind field wind duct based on a speed measuring fan. Background Art

[0002] According to the Practical Manual of Flow Measurement published by China Electric Power Press in 2017.8 ISBN978-7-5198-0722-1, Chapter 6, pages 166 and 167, the requirements for air volume measurement points in the duct of large coal-fired boilers are: 30-50D of straight pipe section installed, and the velocity distribution in the pipe is fully developed turbulent flow; but in reality, the cross-sectional diameter, width or height of large coal-fired boilers reaches 4-8 meters, and the straight pipe section can only reach 1-3D in engineering design, which is far from the 30-50D straight pipe section required in the manual, that is, the duct vortex cannot be fully developed into turbulent flow measurement requirements.

[0003] At present, the air volume measurement technology of large coal-fired boilers widely adopts the technology of geometric average fixed point distribution and sampling in the cross section of the air duct, and the weighted coefficient average air volume measurement technology, such as one-dimensional (various types); two-dimensional (matrix type), plug-in fixed position air volume measurement device (one-dimensional), matrix fixed position air volume measurement device (two-dimensional) and other air volume measurement technologies; sampling in the air duct section where the vortex of the air duct cannot fully develop turbulence. Practice has proved that the existing technology uses geometric symmetry or uniform sampling and no difference in pressure equalization, which cannot represent the average wind speed value of the cross section of the air duct of large coal-fired boilers, that is, the air volume measurement in the air duct is inaccurate; at the same time, the existing air volume measurement technology is easy to cause dust blockage, which will cause the coal-fired boiler of the coal-fired generator set to be unable to accurately reach or approach its optimal air-coal ratio during operation, which greatly reduces the safety and economy of the combustion of the coal-fired boiler, and increases the generation of nitrogen oxides and leads to an increase in environmental protection costs. At the same time, it seriously restricts the flexible power generation capacity of the coal-fired generator set, affects the economic benefits of the peak-shaving electricity price, and also affects the stable operation of the entire power grid. In addition, the cost of the existing air volume measurement technology products is also relatively high. Summary of the invention

[0004] In order to solve the problems in the prior art of measuring wind speed in the air duct of large-scale coal-fired boilers (i.e., non-uniform wind field air duct) using geometric mean point arrangement, inaccurate air volume measurement, easy dust clogging, complex structure, high installation cost, and large wind resistance, the utility model provides an air volume measurement device based on a speed measuring fan, which is accurate in measuring air volume in the cross-section of a non-uniform wind field air duct, has no clogging, low cost, and small wind resistance. The device includes at least one speed measuring fan and a speed measurement unit for monitoring the speed of the fan, and a monitoring and analysis unit in a non-uniform wind field air duct cross-section; and also includes a special-shaped steel frame transversely arranged on the air duct wall of the non-uniform wind field air duct cross-section; wherein the speed measuring fan is arranged in the non-uniform wind field air duct cross-section using the special-shaped steel frame; the speed measurement unit is electrically connected to the monitoring and analysis unit respectively; and the speed measuring fan adopts an unpowered fan.

[0005] Preferably, at least one speed measuring fan of the same specification and a speed measuring unit for respectively monitoring the fans are evenly distributed in the cross section of the wind duct of the non-uniform wind field.

[0006] Preferably, in the non-uniform wind field air duct cross section, a guide plate with a peak-shaped windward surface is respectively provided between the speed measuring fans and between the fans and the air duct wall of the non-uniform wind field air duct cross section.

[0007] Preferably, at least two speed measuring fans of the same specification and speed measuring units for respectively monitoring the fans are evenly distributed in the cross section of the wind duct of the non-uniform wind field.

[0008] Preferably: the speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also provided at a corresponding position on the special-shaped steel frame evenly distributed on the speed measuring fan; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element provided at the outer end of one of the blades of the speed measuring fan and a magnetic counter provided outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is provided on the special-shaped steel frame, and the magnetic counters are electrically connected to the monitoring and analysis units respectively.

[0009] Preferably: the material of the speed measuring fan blades is carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; the number of the speed measuring fan blades is an odd number greater than 1.

[0010] Preferably, the number of blades of the speed measuring fan is three, five, seven, nine or eleven.

[0011] Based on the above, a wind volume measuring device based on a speed measuring fan is provided. In the cross section of the wind duct in the non-uniform wind field, at least one speed measuring fan of different specifications and a speed measuring unit for respectively monitoring the fans can be unevenly distributed.

[0012] Preferably, in the non-uniform wind field air duct cross section, a guide plate with a peak-shaped windward surface is respectively provided between the speed measuring fans of different specifications and between the fans and the air duct wall of the non-uniform wind field air duct cross section.

[0013] Preferably, at least two speed measuring fans of different specifications and speed measuring units for respectively monitoring them are unevenly distributed in the cross section of the wind duct of the non-uniform wind field.

[0014] Preferably: the speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also provided at a corresponding position on the special-shaped steel frame on which the speed measuring fan is provided; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element provided at the outer end of one of the blades of the speed measuring fan and a magnetic counter provided outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is provided on the special-shaped steel frame, and the magnetic counters are electrically connected to the monitoring and analysis units respectively.

[0015] Preferably: the material of the speed measuring fan blades is carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; the number of the speed measuring fan blades is an odd number greater than 1.

[0016] Preferably, the number of blades of the speed measuring fan is three, five, seven, nine or eleven.

[0017] The utility model utilizes at least one speed measuring fan of the same specification evenly distributed in the cross-section of the air duct in a non-uniform wind field (such as the arrangement of the speed measuring fans in the square air duct in Example 1: four speed measuring fans of the same specification and the guide plates with the windward surfaces between them and between the air duct walls being peak-shaped) or at least one speed measuring fan of different specifications unevenly distributed (such as a square air duct can also be provided with a large speed measuring fan and small speed measuring fans of the same specification at four corners), generates torque through the wind speed of the plane reached by their self-average fan blade surface, and the average wind speed of the fan blade and the cross-section generated by weighted averaging through their rotating shaft, and then calculates their weighted average value or area average value, that is, the flow rate of the entire air duct cross-section, and has the advantages of low cost, excellent dynamic average speed performance, small wind resistance (that is, rotation along the flow without obstruction), accurate real-time dynamic measurement, and easy engineering implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the arrangement of a three-blade speed measuring fan in a square air duct cross section in an air volume measuring device based on a speed measuring fan is provided for the first embodiment;

[0019] Figure 2 for Figure 1 A schematic diagram of the arrangement of the special-shaped steel frame 3 in the cross section of the square air duct is shown in FIG.

[0020] Figure 3 for Figure 2 The enlarged schematic diagram of the cross section of the node where the speed measuring fan is arranged in the special-shaped steel frame 3 is shown in FIG.

[0021] Figure 4 for Figure 2 The enlarged schematic diagram of the cross section of the special-shaped steel bar in the special-shaped steel frame 3 is shown in FIG.

[0022] Figure 5 for Figure 1 A schematic diagram of the three-dimensional structure of the speed measuring fan 2 is shown in FIG.

[0023] Figure 6 for Figure 1 A front view schematic diagram of a right-angle guide plate shown in FIG.

[0024] Figure 7 for Figure 6 AA section schematic diagram of the right-angle guide plate shown in FIG;

[0025] Figure 8 for Figure 1 A front view of the side guide plate shown in FIG.

[0026] Fig. 9 for Figure 8 BB section schematic diagram of the side guide plate shown in FIG.

[0027] Fig.10 for Figure 1 A front view of the center guide plate shown in FIG.

[0028] Fig.11 for Fig.10 A schematic CC cross-sectional view of the central guide plate shown in FIG.

[0029] Fig.12 Based on Figure 1 Schematic diagram of the air volume measurement system of the speed measuring fan shown;

[0030] Fig.13 A schematic diagram of the arrangement of a three-blade speed measuring fan in a square air duct cross section in an air volume measuring device based on a speed measuring fan is provided for the second embodiment;

[0031] Fig.14 for Fig.13 Schematic diagram of arrangement of the special-shaped steel frame 3' in the cross section of the square air duct;

[0032] Fig.15 A flow chart of a method for measuring air volume by setting a plurality of speed measuring fans of the same specification in a square air duct cross section in a non-uniform wind field; and

[0033] Fig.16The present invention is a flow chart of a method for measuring air volume by setting a number of speed measuring fans of different specifications in a square air duct cross section in a non-uniform wind field.

[0034] Description of the numbers in the figure:

[0035] 1. Square air duct wall; 2. Speed ​​measuring fan, 21. Fan blade, 22. Permanent magnet element, 23. Fan blade handle, 24. Rotating shaft; 3. Special-shaped steel frame, 31. Special-shaped steel bar, 32. External fixed bearing, 4. Guide plate, 4A. Right-angle guide plate, 4B. Side guide plate, 4C. Center guide plate, 5. Magnetic counter. DETAILED DESCRIPTION

[0036] The following takes the arrangement of a three-blade speed measuring fan in a square air duct cross-section in a non-uniform wind field as an example and describes the utility model in detail in combination with the accompanying drawings and specific embodiments. Example 1

[0037] like Figure 1-11 , which is a schematic diagram of the arrangement of a three-blade speed measuring fan in a square air duct cross section in a non-uniform wind field in an air volume measurement device based on a speed measuring fan; and an air volume measurement system based thereon, such as Fig.12 The air volume measuring device comprises four groups of speed measuring fans 2 and magnetic counters 5, each of which has a permanent magnet element 22 at the outer end of a blade 21, and a monitoring and analysis unit, which are evenly distributed on a special-shaped steel frame 3 in a square air duct cross section of a non-uniform wind field; in order to prevent air leakage between the speed measuring fans 21 and between the square air duct wall 1 of the non-uniform wind field, a guide plate with a peak-shaped windward surface (i.e., a right-angle guide plate 4A (its structural schematic diagram is shown in FIG. 1 ) is also provided between them. Figure 6 and 7 ), side guide plate 4B (its structural schematic diagram is shown in Figure 8 and 9 ) and the central guide plate 4C (its structural diagram is shown in Fig.10 and 11 )); wherein the magnetic counter 5 is electrically connected to the monitoring and analysis unit respectively; the speed measuring fan comprises a fan blade 21, a fan blade handle 23 and a rotating shaft 24, wherein the fan blade 21 is evenly arranged on the outer periphery of one side of the fan blade handle 23, and the rotating shaft 24 is arranged at the axis center of the other side of the fan blade handle 23 (its structural schematic diagram is shown in Figure 5 ); Special-shaped steel frame 3 (its layout diagram is shown in Figure 2 ) is set according to the uniform distribution speed measuring fan, which is composed of a special-shaped steel bar 31 (its cross-sectional structure schematic diagram is shown in Figure 4 ) is a grid-like frame (based on the principle of minimizing the wind resistance in the measurement cross section), and an external fixed bearing 32 is provided at the corresponding position of the speed measuring fan evenly distributed on it; the rotating shaft 24 is axially embedded in the external fixed bearing 32 (its structural schematic diagram is shown in Figure 3). The position of the non-uniform wind field square air duct cross section of the above-mentioned three-blade speed measuring fan can be at any longitudinal position of the air duct, and is not limited by the length of the straight air duct required by the existing design specifications.

[0038] The rotation speed measuring unit comprises a permanent magnet element arranged at the outer end of one of the blades of the speed measuring fan and a magnetic counter arranged outside the speed measuring fan and at a corresponding position thereto.

[0039] How it works:

[0040] Four three-blade speed measuring fans are evenly distributed in the cross-section of the wind duct in the non-uniform wind field. Due to the different positions of each speed measuring fan, the wind speed in the sensing area is different; each blade 21 of each speed measuring fan senses the wind speed at the cross-sectional position in the area where it is located: the same blade senses different wind speeds at different points in the measurement area (non-uniform wind duct wind field); in this way, different rotational torques will be generated at the corresponding points of the blade 21, and the rotational force average of the primary rotational thrust will be achieved through the surface of the blade 21; then the three blades 21 form rotational thrusts of different wind speeds and then pass through the blade handle 23 connected thereto, and perform secondary rotational thrust self-average on the rotating shaft 24; finally, the real-time rotation speed of the speed measuring fan is obtained, which represents the average wind speed in the plane covered by the speed measuring fan; at the same time, the average rotation speed is monitored in real time through the permanent magnet element 22 installed at the outer end of a blade 21 of the speed measuring fan, and through the magnetic counter 5 set on the square air duct wall, the number of rotations per minute of the speed measuring fan is monitored, and the number of rotations per minute of the speed measuring fan is transmitted to the monitoring and analysis unit in real time.

[0041] The air volume calculation method for the above non-uniform wind field with four speed measuring fans of the same specification evenly distributed in the square air duct cross section is as follows (e.g. Fig.15 shown):

[0042] Step 1: Using the electrical signal of the speed measurement unit corresponding to at least one speed measuring fan of the same specification set in the cross section of the wind duct of the non-uniform wind field, the rotation of the speed measuring fan is counted and a pulse sequence is generated. Then, the speed value is obtained through the conversion processing of the monitoring and analysis unit and converted into the circular line wind speed μ2. The calculation formula is as follows:

[0043]

[0044] in,

[0045] μ2——Circumferential wind speed of the outer diameter of the speed measuring fan, in m / s;

[0046] n——the number of revolutions per minute of the speed measuring fan, unit: / s;

[0047] D2——the outer diameter of the speed measuring fan, in m;

[0048] Step 2: According to the circular wind speed μ2 calculated above, and according to the outer diameter D2 and flow calibration coefficient Q1 of the speed measuring fan, the air volume L1, L2, L3, ..., LN in the plane area sensed by the speed measuring fan is calculated respectively, and the formula is as follows:

[0049]

[0050] in,

[0051] Li———Calculated air volume of the i-th speed-measuring fan, in m 3 / s;

[0052] D2——The outer diameter of the speed measuring fan, in m;

[0053] Q1——Flow calibration coefficient, which is related to the shape and working conditions of the speed measuring fan;

[0054] The speed measuring range and accuracy of the speed measuring fan: the general accuracy can only reach 0.1m / s, and the maximum range can reach 50m / s.

[0055] Step 3: Calculate the air volume of the entire sensing air duct cross section using the following formula:

[0056]

[0057] in,

[0058] N is the number of speed measuring fans of the same specification uniformly distributed in the cross section of the wind duct in the non-uniform wind field. In this embodiment, N is 4.

[0059] In this embodiment, the speed measuring fan is an unpowered fan, which can calculate the average wind speed of the plane reached by the average fan blade surface. The average values ​​of different speed measuring fans are weighted to calculate the average wind speed of the plane, thereby accurately calculating the air volume in the cross-section of the wind duct in the non-uniform wind field.

[0060] In this embodiment, the speed measuring fans may be unpowered fans of the same specifications or unpowered fans of different specifications.

[0061] In this embodiment, the fan blades can be carbon fiber blades, titanium alloy blades, silicon carbide blades, aluminum blades, iron blades, acrylic blades, plastic blades, solid wood blades and plywood blades. In order to ensure the stable operation of the speed measuring fan, the number of blades of the speed measuring fan is an odd number greater than 1 according to the wind speed of the non-uniform wind field wind duct, such as three, five, seven, nine, eleven or more blades.

[0062] In the present embodiment, the speed measuring fan is an unpowered fan. The more speed measuring fans are arranged in the cross-section of the air duct of the measured non-uniform wind field, the closer the comprehensive average wind speed of each speed measuring fan will be to the average wind speed in the measured cross-section. At the same time, in order to prevent air leakage between the blades of each speed measuring fan and between the blades of each speed measuring fan and the wall of the air duct of the non-uniform wind field during the rotation of each speed measuring fan, a guide plate with a peak-shaped windward surface is designed between them to achieve the purpose of full wind speed measurement and fixing the speed measuring fan.

[0063] The wind speed measuring device of the present invention is simple and easy to operate. The wind speed in the cross section of the non-uniform wind field duct is averaged by the blades in the speed measuring fan and averaged between the matrix groups of the speed measuring fans to form an accurate average wind speed measurement, breaking the harsh condition that the design specification requires the straight pipe section of the wind volume measurement in the wind duct of a large coal-fired boiler to be 30-50D. It is particularly suitable for measuring the wind volume of large wind ducts with no straight pipe sections and variable diameters in coal-fired boilers, and well solves the global problem of inaccurate wind volume measurement in the wind duct of a non-uniform wind field caused by turbulence, vortex and other phenomena in the wind duct of a non-uniform wind field.

[0064] In addition to the overall layout design of the speed measuring fan with a plurality of speed measuring fans evenly distributed in the air duct and a guide plate with a peak-shaped windward surface, the overall layout design can also be performed according to the geometric shape of the air duct cross section, the error of the air volume measured by the overall layout design of the speed measuring fan in the air duct cross section, and the size of the wind resistance of the overall layout design of the speed measuring fan in the air duct cross section. For example, a speed measuring fan with a blade of the same size as the circular radius is set for an air duct with a non-uniform wind field cross section, and then the overall layout design is performed according to the geometric shape of the air duct cross section, the error of the air volume measured by the overall layout design of the speed measuring fan in the air duct cross section, and the size of the wind resistance of the overall layout design of the speed measuring fan in the air duct cross section. Small (minimize the wind resistance while satisfying the measurement error) select the other specification parameters of the speed measuring fan except its outer diameter; for a duct with a square cross-section in a non-uniform wind field, set a speed measuring fan with an inscribed circle in the square, and arrange a speed measuring fan of the same specification at each of the four corners between the speed measuring fan and the square duct wall, or fill each with a guide plate with a mountain-shaped windward surface (wherein the selection of other specification parameters of the speed measuring fan except its outer diameter: overall measurement error and wind resistance (minimize the wind resistance while satisfying the overall measurement error)). The overall layout design scheme for the square duct with a non-uniform wind field cross-section mentioned above: one large speed measuring fan and four small speed measuring fans, and the air volume (i.e., the average wind speed value of the duct) measurement method (calculation method) is as follows (such as Fig.16 shown):

[0065] First, calculate the air volume of each speed-measuring fan (a large speed-measuring fan and four small speed-measuring fans) according to steps 1 and 2 of the air volume calculation method for four speed-measuring fans of the same specification evenly distributed in the cross section of the square air duct in the non-uniform wind field;

[0066] Then multiply the air volume of each speed measuring fan calculated above by the proportion of the entire fan blade rotating cross-sectional area of ​​each speed measuring fan in the entire air duct cross-sectional area to get the average wind speed value of the air duct (assuming that the air volume value of the large speed measuring fan is LA1, the proportion of its entire fan blade rotating cross-sectional area in the entire air duct cross-sectional area SA1 is 0.8, and the air volume values ​​of the four small speed measuring fans are La1, La2, La3, and La4 respectively, and the proportions of their respective entire fan blade rotating cross-sectional areas in the entire air duct cross-sectional area sa1, sa2, sa3, and sa4 are all 0.05):

[0067] The average wind speed value of the air duct = the sum of the air volume value of each speed measuring fan multiplied by the proportion of the entire fan blade rotating cross-sectional area of ​​each speed measuring fan in the entire air duct cross-sectional area

[0068] =LA1*SA1+La1*sa1+ La2*sa2+ La3*sa3+ La4*sa4

[0069] =LA1*0.8+ La1*0.05+ La2*0.05+ La3*0.05+ La4*0.05

[0070] For example, an air duct with a rectangular cross-section in a non-uniform wind field is provided with two speed measuring fans inscribed in the rectangle, and a speed measuring fan of the same specification is arranged at each of the four corners between the two speed measuring fans and the rectangular air duct wall, or each is filled with a guide plate with a peak-shaped windward surface (of course, the above two adjacent corner areas can be provided with only one speed measuring fan or a guide plate with a peak-shaped windward surface. For the selection of other specification parameters of the speed measuring fan except its outer diameter and the calculation of the average wind speed value of the air duct, please refer to the above-mentioned air duct calculation method for the square air duct with a non-uniform wind field cross-section).

[0071] The measurement error of the overall layout selection design of the speed measuring fan in the cross section of the air duct in this embodiment can be determined according to the following three methods:

[0072] 1. Computer simulation The air duct model is determined by computer;

[0073] 2. Indirect determination based on laboratory simulation of actual air duct experiments;

[0074] 3. Install in the actual air duct and calibrate with standard measuring instruments to determine the actual measurement (the air volume measuring device is also a kind of measuring instrument, which must be calibrated by a calibration agency before it can be used, as long as the measurement error of the air volume measuring device in this embodiment is within the calibration range).

[0075] The technical solution of this embodiment is easier to implement in actual engineering implementation and installation, and its practicality is stronger; at the same time, compared with the existing uniform tube air volume measuring device, multi-point insertion air volume measuring device, especially the existing Pitot tube air volume flowmeter or Venturi air volume flowmeter and the big data air volume measurement system constituted by them (such as Chinese patent number CN2022227521229 patent name: A wind volume measurement system for wind ducts in non-uniform wind fields, Chinese patent CN2022227517134 patent name: A wind volume measurement system based on big data analysis), a back-purge device is required to prevent dust from clogging the air volume flowmeter. Dust will not cause clogging problems, and accurate measurements can be made in real time and dynamically, and the cost is low and the operation and maintenance are convenient; in addition, compared with the wing-type air volume measuring device in the prior art, there is almost no wind resistance loss. Example 2

[0076] like Fig.13 As shown, it is a schematic diagram of the arrangement of two three-blade speed measuring fans in a square air duct cross section of a non-uniform wind field in an air volume measurement device based on a speed measuring fan; the difference from the first embodiment is that: the two three-blade speed measuring fans are installed at the position of the data average wind speed point in the square air duct cross section of the non-uniform wind field, and there is no need to set a guide plate with a peak-shaped windward surface between the speed measuring fans 2 and between the speed measuring fans 2 and the square air duct wall 1 of the non-uniform wind field; because the speed measuring fans are irregularly arranged in the square air duct cross section of the non-uniform wind field, the structure of the special-shaped steel frame 3' fixing them is also changed accordingly, such as Fig.14 As shown; for the rest of the structural parts, please refer to the corresponding parts of Example 1.

[0077] How it works:

[0078] In this embodiment, the speed measuring fan is an unpowered fan, which is arranged at the position of the data average wind speed point in the square air duct cross-section of the non-uniform wind field. By weighting the wind speed of the plane reached by the self-average fan blade surface, the average wind speed in the square air duct cross-section of the non-uniform wind field can be directly calculated by the average value of the two speed measuring fans, thereby accurately measuring the air volume in the square air duct cross-section of the non-uniform wind field; or directly using the self-average wind speed of one of the speed measuring fans, the air volume in the square air duct cross-section of the non-uniform wind field can also be accurately measured.

[0079] In this embodiment, the number of speed measuring fans is set according to the number of data average wind speed points in the square wind duct cross section of the non-uniform wind field, and at least one speed measuring fan is set; at the same time, a speed measuring fan of specific specifications (mainly referring to the blade material, blade shape and size, number of blades and other parameters of the speed measuring fan) is selected according to the size of the data average wind speed value, that is, after the average wind speed position is determined, the smaller the size of the speed measuring fan, the more accurate the air volume measurement in the cross section of the non-uniform wind field. The method for determining the data average wind speed point in the cross section of the wind duct in the non-uniform wind field has been disclosed in a Chinese patent (patent number CN2022112805951, patent name method for determining the data average wind speed value point in the cross section of the wind duct in the non-uniform wind field). A speed measuring fan is directly set at the data average wind speed point. Since the speed measuring fan can measure the wind speed of the plane reached by the average fan blade surface, the speed measuring fan does not need to be set in the non-uniform wind field. The position error of the wind duct cross section does not need to be particularly accurate, and the air volume in the square wind duct cross section of the non-uniform wind field can be accurately measured. In this way, the technical solution of this embodiment is easier to implement in actual engineering implementation and installation, and its practicality is stronger; at the same time, compared with the existing uniform pipe air volume measurement device, multi-point insertion air volume measurement device, especially the existing bar-type air volume flowmeter or Venturi type The air volume flow meter and the big data air volume measurement system it constitutes (such as Chinese patent number CN2022227521229 patent name: an air volume measurement system for an air duct in a non-uniform wind field, Chinese patent CN2022227517134 patent name: an air volume measurement system based on big data analysis) must also be equipped with a back-purge device to prevent dust from clogging the air volume flow meter. The problem of clogging caused by dust will not occur, and the structure is simple and the installation cost is low. In addition, compared with the wing-type air volume measurement device in the prior art, there is almost no wind resistance loss. In addition, in order to prevent the failure of one of the speed measuring fans or the speed measuring unit (the speed measuring unit includes a permanent magnet element provided at the outer end of one of the blades of the speed measuring fan and a magnetic counter provided at the outer edge of the speed measuring fan and at a corresponding position thereof), a speed measuring fan can be respectively provided at two or more data average wind speed points within the cross-section of the square air duct in the non-uniform wind field, and speed measuring units can be respectively monitored therefor. The specific specifications of the speed measuring fans should be basically the same (the reason is that the wind speeds at the data average wind speed points within the cross-section of the square air duct in the non-uniform wind field are approximately equal within the allowable range of air volume measurement error).

[0080] After confirming the three average wind speed points according to the public technical solution of the Chinese patent (patent number CN2022112805951, patent name: method for determining the data average wind speed value point in the cross section of the wind duct in a non-uniform wind field), a standard wind tunnel experimental device (this standard wind tunnel experimental device is the wind tunnel experimental device of Baoji Branch of Xi'an Zhongwang Measurement and Control Instrument Co., Ltd., which is designed and manufactured by Chongqing Lantian Instrument Co., Ltd. and calibrated by Chongqing Metrology and Quality Inspection Institute. The calibration uses a Pitot tube flowmeter, and the wind duct is designed to be 1:1 with the actual wind duct outer dimensions, that is, the public experimental wind duct in the Chinese patent (patent number CN2022112805951, patent name: method for determining the data average wind speed value point in the cross section of the wind duct in a non-uniform wind field) is used to conduct a reverse verification experiment on the accuracy of its air volume measurement. The experimental time is August 16, 2023, and the experimental process is as follows:

[0081] Step 1: Use the standard measuring instruments in Table 1 to calibrate the seven different wind speeds at the three average wind speed points mentioned above. The corresponding recorded data are shown in Table 2;

[0082] Table 1: List of main standard measuring instruments used for calibration:

[0083] name Measuring range Technical features Traceability Agency Certificate No. Validity Pitot tube L8-1000 / 0.999 Shaanxi Institute of Metrology QL10235580Z 20240510 Digital pressure gauge CPG2400 0~2500Pa 0.00% Chongqing Metrology and Quality Inspection Institute 202208150362 20240814 Temperature and humidity sensor HF332-DB1 / Temperature: U=0.3℃ k=2 Humidity: U=1.2%RH,k=2 Chongqing Metrology and Quality Inspection Institute 2022081502566 20240811 Intelligent differential pressure transmitter 3051CD 0~4000Pa 0.10% Shaanxi Institute of Metrology YP20221986J 20241016

[0084] Step 2: First, use a dual-throat wind speed measuring device (Xi'an Zhongwang Measurement and Control Instrument Co., Ltd. dual-throat air volume measuring device: Model AFM-110) to measure the differential pressure values ​​at the above three average wind speed points under seven different wind speed conditions, and then use a fan anemometer (Germany Testo (TESTO) mini anemometer, model TESTO 410-1) to measure and verify the wind speed at the above three average wind speed points under seven different wind speed conditions. The records are as follows:

[0085] Table 2: Standard calibration measurement section wind speed (Pitot tube) - throat diameter (traditional differential pressure) - fan anemometer (speed measuring fan) "three measurement methods measurement data record table

[0086] The first wind speed The second wind speed The third wind speed The fourth wind speed The fifth wind speed The sixth wind speed Seventh wind speed unit Calibration section reference wind speed 2.97 4.58 6.01 8.47 10.23 11.47 12.47 m / s Air duct measuring point 1 differential pressure 11.4 34.8 68.9 176.8 267.7 352.9 409.7 Pa Wind speed at wind duct measuring point 1 3.82 6.15 8.24 12.32 14.71 16.56 17.65 m / s Air duct measuring point 2 differential pressure 9.9 32.7 68.9 175.4 260.6 345.8 400.4 Pa Wind speed at wind duct measuring point 2 3.59 5.99 8.24 _12.28 14.55 16.41 17.48 m / s Air duct measuring point 3 differential pressure 11.4 34.8 71 178.2 260.6 354.3 402.6 Pa Wind speed at wind duct measuring point 3 3.82 6.15 8.34 12.36 14.55 16.59 17.52 m / s

[0087] Note: The calibration section reference wind speed measuring instrument has been calibrated by the national traceability agency and is within the validity period. The calibration section reference wind speed measurement results are used as the comparison standard for the measurement results of the double-throat diameter wind speed measuring device (differential pressure type) and the fan flow meter. The measurement results of the double-throat diameter wind speed measuring device and the fan flow meter are their actual measurement data.

[0088] Step 3: Calculate the error between the wind speeds at the three average wind speed points in the wind duct and the average wind speed of the three average wind speed points (according to the corresponding reference wind speed (one of the above seven wind speeds) and the corresponding average wind speed point, and the percentage of conversion based on the calibrated reference wind speed measurement result), see Table 3.

[0089] Table 3: The average wind speed at the three average wind speed points, and the error conversion table between the wind speed at the three average wind speed points and the average wind speed at the three average wind speed points

[0090] The first wind speed The second wind speed The third wind speed The fourth wind speed The fifth wind speed The sixth wind speed Seventh wind speed unit Average wind speed at three points in the wind duct 3.74 6.10 8.27 12.32 14.60 16.52 17.55 m / s Error between one point in the air duct and the average speed 0.424 0.307 -0.202 0.000 0.638 0.219 0.577 % Error between 2 points in the air duct and average speed -0.849 -0.613 -0.202 -0.238 -0.319 -0.597 -0.405 % Error between 3 points in the air duct and average speed 0.424 0.307 0.404 0.237 -0.319 0.379 -0.172 %

[0091] The error value calculation in Table 3 is as follows: the wind speed value at each point is subtracted from the average wind speed value at three points, divided by the maximum wind speed (17.52), and multiplied by 100; then the three error values ​​are averaged, and the average error values ​​all reach above 0.6 level, that is, the wind volume measurement accuracy reaches above 0.6 level.

[0092] The above experiments prove that the fan tachometer (speed measuring fan) verifies the results at the above three average wind speed points and seven different wind speeds, and its air volume measurement accuracy reaches above level 0.6, which is far better than the 2% accuracy requirement of the national industrial secondary flow measurement standard stipulated in the standard.

[0093] In this embodiment, the fan blade material can be carbon fiber blades, titanium alloy blades, silicon carbide blades, aluminum blades, iron blades, acrylic blades, plastic blades, solid wood blades and plywood blades.

[0094] In order to ensure stable operation of the speed measuring fan, the number of blades of the speed measuring fan is selected to be an odd number greater than 1 according to the wind speed in the wind duct of the non-uniform wind field, such as three, five, seven, nine, eleven or more blades.

[0095] The inventive points of the present invention are: 1) using a number of speed measuring fans of the same specification in the cross-section of an air duct in a non-uniform wind field (such as a large speed measuring fan in a square air duct and guide plates with peak-shaped windward surfaces at the four corners, or the speed measuring fans in the square air duct as in Example 1: four speed measuring fans of the same specification and guide plates with peak-shaped windward surfaces between them and between the air duct walls) or a number of speed measuring fans of different specifications (such as a rectangular air duct or other irregular air ducts, a large speed measuring fan and small speed measuring fans of the same specification at the four corners) are arranged, and torque is generated by the wind speed of the plane reached by their self-average fan blade surface, and the average wind speed of the cross-section reached by the fan blade is generated after averaging and weighting by the rotating shaft, and then the weighted average value or area weighted average value, that is, the air volume of the entire air duct cross-section, is calculated in real time and dynamically, so that the air volume in the cross-section of the air duct in the non-uniform wind field is accurately measured by a technical means similar to the overall data average wind speed. 2) By directly setting a speed measuring fan at the data average wind speed point in the cross section of the wind duct in the non-uniform wind field, the wind speed of the plane reached by the self-average blade surface of the speed measuring fan is used, and there is no need to use the average value of each speed measuring fan to weight and dynamically calculate the average wind speed of the entire cross section in real time, so that the air volume in the cross section of the wind duct in the non-uniform wind field can be conveniently and accurately measured by using technical means similar to the data average wind speed. This breaks the drawback of the geometric average designed to replace the inaccurate cross-sectional wind speed measurement that cannot be met in previous domestic and international specifications. The above uses a three-blade speed measuring fan arranged in the cross section of a square wind duct in a non-uniform wind field as an example to illustrate the present invention in conjunction with the accompanying drawings, but it can be understood that those skilled in the art can make changes or improvements to the present invention without departing from the essential spirit and scope of the present invention, but all should fall within the protection scope of the technical solution of the present invention.

Claims

1. An air volume measuring device based on a speed measuring fan, characterized in that: The device includes at least one speed measuring fan and a speed measuring unit for monitoring the speed of the fan, and a monitoring and analysis unit in a non-uniform wind field wind duct cross section; it also includes a special-shaped steel frame arranged horizontally on the wind duct wall of the non-uniform wind field wind duct cross section; wherein the speed measuring fan is arranged in the non-uniform wind field wind duct cross section by using the special-shaped steel frame; the speed measuring unit is electrically connected to the monitoring and analysis unit respectively; the speed measuring fan adopts a non-powered fan.

2. The air volume measuring device according to claim 1, characterized in that: At least one speed measuring fan of the same specification and a speed measuring unit for respectively monitoring the speed measuring fans are evenly distributed in the cross section of the wind duct of the non-uniform wind field.

3. The air volume measuring device according to claim 2, characterized in that: In the non-uniform wind field air duct cross section, a guide plate with a peak-shaped windward surface is respectively arranged between the speed measuring fans and between the air duct wall of the non-uniform wind field air duct cross section.

4. The wind volume measuring device according to claim 2 or 3, characterized in that: At least two speed measuring fans of the same specification and speed measuring units for respectively monitoring the fans are evenly distributed in the cross section of the wind duct of the non-uniform wind field.

5. The wind volume measuring device according to claim 2 or 3, characterized in that: The speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also arranged at a corresponding position on the special-shaped steel frame evenly distributed with the speed measuring fan; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element arranged at the outer end of one of the blades of the speed measuring fan and a magnetic counter arranged outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is arranged on the special-shaped steel frame, and the magnetic counters are electrically connected to the monitoring and analysis units respectively.

6. The wind volume measuring device according to claim 4, characterized in that: The speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also arranged at a corresponding position on the special-shaped steel frame on which the speed measuring fan is evenly distributed; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element arranged at the outer end of one of the blades of the speed measuring fan and a magnetic counter arranged outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is arranged on the special-shaped steel frame, and the magnetic counter is electrically connected to the monitoring and analysis unit; the material of the blades of the speed measuring fan is selected from carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; the number of blades of the speed measuring fan is selected from an odd number greater than 1; the number of blades of the speed measuring fan is selected from three, five, seven, nine or eleven.

7. The air volume measuring device according to claim 5, characterized in that: The material of the speed measuring fan blades is selected from carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; the number of the speed measuring fan blades is an odd number greater than 1.

8. The wind volume measuring device according to claim 7, characterized in that: The number of blades of the speed measuring fan is selected to be three, five, seven, nine or eleven.

9. The air volume measuring device according to claim 1, characterized in that: At least one speed measuring fan of different specifications and a speed measuring unit for respectively monitoring the fans are unevenly distributed in the cross section of the wind duct of the non-uniform wind field.

10. The wind volume measuring device according to claim 9, characterized in that: In the non-uniform wind field air duct cross section, a guide plate with a peak-shaped windward surface is respectively arranged between the speed measuring fans of different specifications and between the fans and the air duct wall of the non-uniform wind field air duct cross section.

11. The wind volume measuring device according to claim 9 or 10, characterized in that: At least two speed measuring fans of different specifications and speed measuring units for respectively monitoring them are unevenly distributed in the cross section of the wind duct of the non-uniform wind field.

12. The wind volume measuring device according to claim 9 or 10, characterized in that: The speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also provided at a corresponding position on the special-shaped steel frame on which the speed measuring fan is provided; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element provided at the outer end of one of the blades of the speed measuring fan and a magnetic counter provided outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is provided on the special-shaped steel frame, and the magnetic counters are electrically connected to the monitoring and analysis units respectively.

13. The wind volume measuring device according to claim 11, characterized in that: The speed measuring fan includes blades, blade handles and a rotating shaft; an external fixed bearing is also provided at a corresponding position on the special-shaped steel frame on which the speed measuring fan is provided; the rotating shaft is axially embedded in the external fixed bearing; the speed measuring unit includes a permanent magnet element provided at the outer end of one of the blades of the speed measuring fan and a magnetic counter provided outside the speed measuring fan and at a corresponding position thereto; wherein the magnetic counter is provided on the special-shaped steel frame, and the magnetic counter is electrically connected to the monitoring and analysis unit respectively; the material of the blades of the speed measuring fan is selected from carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; the number of blades of the speed measuring fan is selected from an odd number greater than 1; the number of blades of the speed measuring fan is selected from three, five, seven, nine or eleven.

14. The wind volume measuring device according to claim 12, characterized in that: The fan blades of the speed measuring fan are made of carbon fiber, titanium alloy, silicon carbide, aluminum, iron, acrylic, plastic, solid wood or plywood; The number of blades of the speed measuring fan is an odd number greater than 1.

15. The wind volume measuring device according to claim 14, characterized in that: The number of blades of the speed measuring fan is selected to be three, five, seven, nine or eleven.

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