A device and method for quickly calibrating the flow rate of a fan

Abstract

This application belongs to the technical field of air flow rate calibration, and particularly relates to a device and method for quickly calibrating the flow rate of a fan. By calculating the current inner diameter d of the long-neck nozzle and the inner diameter D of the outlet pipe in real time, the current thermal expansion and contraction conditions of the long-neck nozzle and the outlet pipe can be obtained, so that the mass flow rate Q flowing through the long-neck nozzle can be accurately obtained for accurate flow rate calibration. At the same time, by setting a rectifying grid upstream of the long-neck nozzle to rectify the gas flowing through the long-neck nozzle, the air intake uniformity and the accuracy of the flow rate measurement of the scene nozzle are ensured. By setting multiple measuring points for mass flow rate calculation, the flow rate standard device does not need to be installed at the inlet of the device to be calibrated, nor does it need to install multiple sets of calibration devices, which reduces costs and is convenient for installation and disassembly. It can be selectively installed at the inlet and outlet of the fan according to the structural characteristics of the fan to be calibrated, with wide applicability. Considering the change in the nozzle structure caused by the measurement environment, the flow rate calibration accuracy is high.

Description

Technical Field

[0001] This application belongs to the technical field of air flow rate calibration, and particularly relates to a device and method for rapid calibration of fan flow rate. Background Art

[0002] During the detection process of the flow area of the high and low pressure turbine guide vanes of an aero-engine by using the low-speed blowing method, the volumetric fan inside the measuring device is affected by factors such as atmospheric pressure, temperature, humidity, and equipment wear and aging, and its flow characteristics will change unpredictably. Therefore, calibration is required to ensure the measurement accuracy of the guide vane flow area. However, due to the fact that the fan to be calibrated is located inside the equipment, off-line calibration has the following disadvantages:

[0003] 1. The portable gas flow calibration method does not consider the thermal expansion and contraction of the nozzle and the area change caused by the change of the use environment, resulting in inaccurate flow measurement and low calibration accuracy;

[0004] 2. There is no rectification in front of the flow nozzle in the portable gas flow calibration device, and uneven intake air is likely to cause inaccurate flow measurement of the nozzle, and the requirements for intake air conditions are high;

[0005] 3. The portable gas flow calibration device needs to be installed at the inlet of the pipeline of the device to be calibrated. For the device to be calibrated with multiple intake ports, multiple sets of calibration devices need to be installed, which is costly, or other upstream structures of the device to be calibrated need to be disassembled, making it cumbersome to use and having low applicability.

[0006] Therefore, it is necessary to adopt a rapid and convenient in-situ calibration device and method. Summary of the Invention

[0007] The purpose of this application is to provide a device and method for rapid calibration of fan flow rate, so as to solve the problems that the existing off-line calibration method does not conform to the actual use environment, calibration after disassembly affects the use of the equipment, and repeated disassembly and assembly increase the cumbersome degree of equipment use.

[0008] The first aspect of the present application provides a device for rapid calibration of fan flow rate, including a long-neck nozzle, an outlet pipe, a rectifying grid, a pressure stabilizing section, and a transition section; the inlet end of the transition section is connected to the outlet of the fan to be calibrated, and the outlet end is connected to the inlet end of the pressure stabilizing section; the outlet end of the pressure stabilizing section is coaxially connected to the outlet pipe; a long-neck nozzle is arranged inside the outlet pipe; a signal processor is electrically connected to the long-neck nozzle, the signal processor is electrically connected to a computer, and an atmospheric pressure gauge is also connected to the signal processor; a porous medium is arranged inside the pressure stabilizing section; wall static pressure holes are opened at the throat of the long-neck nozzle and upstream of the outlet pipe, and temperature sensors and static pressure sensors are arranged inside both the outlet pipe and the long-neck nozzle, the static pressure sensors are arranged inside the wall static pressure holes, and an outlet pipe temperature measurement point, a long-neck nozzle temperature measurement point, an outlet pipe static pressure measurement point, and a long-neck nozzle static pressure measurement point are formed on the outlet pipe and the long-neck nozzle; a rectifying grid is arranged upstream of the long-neck nozzle, and the rectifying grid is fixedly connected to the outlet pipe; inlet air temperature and humidity sensors are installed on equal annuli upstream of the rectifying grid to form inlet air temperature and humidity measurement points.

[0009] The second aspect of the present application provides a method for rapid calibration of fan flow rate, including:

[0010] Estimate the flow rate range of the fan to be calibrated, determine the calibration range, select a long-neck nozzle that meets the calibration range, select an outlet pipe according to the inner diameter d size of the long-neck nozzle, select a rectifying grid and a pressure stabilizing section according to the inner diameter D size of the outlet pipe, and select a transition section with a size matching that of the pressure stabilizing section;

[0011] Establish a calibration device: Install the long-neck nozzle and the rectifying grid on the outlet pipe, and evenly distribute multiple static pressure measurement points circumferentially upstream and downstream of the inlet end face of the long-neck nozzle; evenly embed multiple temperature measurement points circumferentially at the throat of the long-neck nozzle and upstream of the outlet pipe; install multiple inlet air temperature and humidity measurement points on equal annuli upstream of the rectifying grid, and install the atmospheric pressure gauge in the test environment;

[0012] Obtain the static pressure Ps1 at the throat of the long-neck nozzle and the static pressure Ps0 of the upstream incoming flow of the long-neck nozzle through the static pressure measurement points, obtain the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outlet pipe wall through the temperature measurement points, obtain the incoming flow temperature t and humidity Hu through the inlet air temperature and humidity measurement points, and obtain the atmospheric pressure Pa through the atmospheric pressure gauge; then calculate the mass flow rate Q flowing through the long-neck nozzle through an iterative method according to the obtained data;

[0013] Control the air supply of the fan to be calibrated, increase the speed to the calibration range, obtain the mass flow rate Q flowing through the long-neck nozzle in real time, and record the speed of the fan to be calibrated. The fan to be calibrated continuously increases the rotation speed to increase the intake air flow rate until the flow rate calibration of the required calibration range is completed;

[0014] Dismantle the calibration device, complete data processing and output, and end the calibration work.

[0015] Preferably, the iterative method is calculated as follows:

[0016] Measure the incoming flow temperature t and humidity Hu through the temperature and humidity measuring points at the inlet, and calculate the physical properties of the incoming flow in combination with the ambient atmospheric pressure Pa. The physical properties of the incoming flow include the incoming flow density , viscosity and isentropic exponent ;

[0017] According to the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outlet pipe wall, calculate the inner diameter temperature functions of the long-neck nozzle and the outlet pipe wall respectively , T = T1 or T2; then calculate the inner diameter d of the long-neck nozzle and the inner diameter D of the outlet pipe in real time according to the inner diameter temperature function, and obtain the pipe diameter ratio ;

[0018] Obtain the static pressure Ps1 at the throat of the long-neck nozzle and the static pressure Ps0 of the incoming flow upstream of the long-neck nozzle from the static pressure measuring point, and calculate the pressure difference , pressure ratio ;

[0019] According to the pipe diameter ratio and combined with the pressure ratio and isentropic exponent calculate the expansion coefficient ;

[0020] According to the expansion coefficient calculate the parameter , and set the initial value of the discharge coefficient of the long-neck nozzle;

[0021] Let n = 1 in the Reynolds number calculation formula , is the discharge coefficient of the long-neck nozzle, is the Reynolds number; substitute the initial value of the discharge coefficient of the long-neck nozzle into the Reynolds number calculation formula to obtain the iterative value of the Reynolds number , and according to the iterative value of the Reynolds number continuously iterate the Reynolds number ;

[0022] Judge whether the Reynolds number satisfies the convergence judgment formula. If it is satisfied, output the mass flow rate Q from the mass flow rate calculation formula ; if not, calculate the iterative value of the discharge coefficient from the empirical formula of the discharge coefficient of the nozzle, and continue to iterate the Reynolds number.

[0023] Preferably, the convergence judgment formula is , m is a positive integer set by the user; the initial value of the discharge coefficient of the long-neck nozzle is .

[0024] Preferably, the inner diameter D of the outlet pipe is 2d to 2.5d; the length of the rectifying grid is 2D to 2.5D, and the diameter of the pressure stabilizing section is 4D to 5D.

[0025] Preferably, a plurality of static pressure measuring points are circumferentially distributed at a position 1D upstream of the inlet end face of the long-neck nozzle, and a plurality of static pressure measuring points are circumferentially distributed at a position 0.5D downstream of the inlet end face of the long-neck nozzle.

[0026] The fan flow rate rapid calibration device and method of the present application can obtain the current thermal expansion and contraction conditions of the long-neck nozzle and the outlet pipe by calculating the current inner diameter d of the long-neck nozzle and the inner diameter D of the outlet pipe in real time, so as to accurately obtain the mass flow rate Q flowing through the long-neck nozzle for accurate flow rate calibration; at the same time, by arranging a rectifying grid upstream of the long-neck nozzle to rectify the gas flowing through the long-neck nozzle, the air intake uniformity and the accuracy of the flow rate measurement of the scene nozzle are ensured; by setting multiple measuring points for mass flow rate calculation, the flow rate standard device does not need to be installed at the inlet of the device to be calibrated, nor does it need to install multiple sets of calibration devices, which reduces costs and is convenient for installation and disassembly. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions provided by the present application, the drawings will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application.

[0028] Figure 1 It is a schematic diagram of the overall structure of the rapid calibration device of the present application;

[0029] Figure 2 It is a schematic diagram of the overall flow of the rapid calibration method of the present application.

[0030] 1. Outlet of the fan to be calibrated; 2. Transition section; 3. Pressure stabilizing section; 4. Porous medium; 5. Atmospheric pressure gauge; 6. Signal processor; 7. Computer; 8. Outlet pipe; 9. Temperature measuring point of the long-neck nozzle; 10. Static pressure measuring point of the long-neck nozzle; 11. Long-neck nozzle; 12. Temperature measuring point of the outlet pipe; 13. Static pressure measuring point of the outlet pipe; 14. Rectifying grid; 15. Inlet air temperature and humidity measuring point. Detailed Embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The first aspect of the present application provides a fan flow rate rapid calibration device, as Figure 1, including a long-neck nozzle 11, an outflow pipe 8, a rectifying grid 14, a pressure stabilizing section 3 and a transition section 2. The inlet end of the transition section 2 is connected to the outlet of the to-be-calibrated fan 1, and the outlet end is connected to the inlet end of the pressure stabilizing section 3; the outlet end of the pressure stabilizing section 3 is coaxially connected to the outflow pipe 8. The long-neck nozzle 11 is arranged inside the outflow pipe 8; a signal processor 6 is electrically connected to the long-neck nozzle 11, the signal processor 6 is electrically connected to a computer 7, and at the same time, an atmospheric pressure gauge 5 is also connected to the signal processor 6.

[0033] A porous medium 4 is arranged inside the pressure stabilizing section 3, which can reduce the spatial non-uniformity of the incoming flow velocity and reduce the pressure; wall static pressure holes are opened at the throat of the long-neck nozzle 11 and upstream of the outflow pipe 8. Temperature sensors and static pressure sensors are arranged inside both the outflow pipe 8 and the long-neck nozzle 11. The static pressure sensors are arranged inside the wall static pressure holes, and outflow pipe temperature measurement points 12, long-neck nozzle temperature measurement points 9, outflow pipe static pressure measurement points 13 and long-neck nozzle static pressure measurement points 10 are formed on the outflow pipe 8 and the long-neck nozzle 11. The corresponding temperature measurement points are used to obtain the real-time temperatures of the long-neck nozzle 11 and the outflow pipe 8, and correct the inner diameters of the long-neck nozzle 11 and the outflow pipe 8; the corresponding static pressure measurement points are connected to the signal processor 6 and the computer 7 to output the local static pressure value in real time.

[0034] A rectifying grid 14 is further arranged upstream of the long-neck nozzle 11. The rectifying grid 14 is fixedly connected to the outflow pipe 8, playing a role in rectifying and breaking vortices, so that the flow in the outflow pipe 8 is uniform and stable during calibration. An inlet air temperature and humidity sensor is installed on the equatorial plane upstream of the rectifying grid 14 to form an inlet air temperature and humidity measurement point 15, which is used to measure the temperature and humidity conditions of the incoming flow and calculate the physical property parameters of the incoming flow.

[0035] The transition section 2 is selected to be installed or not according to whether the calibration device is connected to the outlet of the to-be-calibrated fan 1, and a detachable connection is maintained with the upstream of the pressure stabilizing section 3. The transition section 2 is connected to the outlet of the to-be-calibrated fan 1 to form a calibration flow passage with good airtightness.

[0036] The second aspect of the present application provides a method for quickly calibrating the flow rate of a fan. Using the above calibration device, the flow rate of the fan is quickly calibrated, as Figure 2 , specifically including the following steps:

[0037] Step S100, structure selection: Estimate the flow rate range of the to-be-calibrated fan, determine the calibration range, select a long-neck nozzle that meets the calibration range, select an outflow pipe according to the inner diameter size of the long-neck nozzle, select a rectifying grid and a pressure stabilizing section according to the inner diameter size of the outflow pipe, and select a transition section with a size matching that of the pressure stabilizing section.

[0038] Preferably, the inner diameter of the long-neck nozzle is d, and the inner diameter D of the outflow pipe is 2d to 2.5d; the length of the rectifying grid is 2D to 2.5D, and the diameter of the pressure stabilizing section is 4D to 5D.

[0039] Step S200, Installation of the calibration device: Install the long-neck nozzle and the rectifying grid on the outflow pipe. The specific installation method is to determine whether the vortex size in the flow state immediately upstream of the inlet surface of the long-neck nozzle is less than the set value or there is no vortex under the current installation position. When the vortex size is greater than the set value, the installation positions of the long-neck nozzle and the rectifying grid are adjusted again until the requirements are met.

[0040] A plurality of static pressure measurement points are evenly distributed circumferentially upstream and downstream of the inlet end face of the long-neck nozzle. A plurality of temperature measurement points are evenly embedded circumferentially in the throat of the long-neck nozzle and the upstream outflow pipe. A plurality of inlet air temperature and humidity measurement points are installed on the equal annulus upstream of the rectifying grid, and the atmospheric pressure gauge is installed in the test environment.

[0041] If it is necessary to install the calibration device at the outlet of the fan to be calibrated, connect the calibration device together with the transition section to the outlet of the fan to be calibrated, otherwise the transition section is not installed.

[0042] Assemble and connect the above-mentioned hardware so that the airtightness of the flow pipeline is good and the sensors at each measurement point work normally.

[0043] Preferably, a plurality of static pressure measurement points are evenly distributed circumferentially at a position 1D upstream of the inlet end face of the long-neck nozzle, and a plurality of static pressure measurement points are evenly distributed circumferentially at a position 0.5D downstream of the inlet end face of the long-neck nozzle.

[0044] Step S300, Mass flow calculation: Obtain the static pressure Ps1 at the throat of the long-neck nozzle and the static pressure Ps0 of the upstream flow of the long-neck nozzle through the static pressure measurement points, obtain the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outflow pipe wall through the temperature measurement points, obtain the incoming flow temperature t and humidity Hu through the inlet air temperature and humidity measurement points, and obtain the atmospheric pressure Pa through the atmospheric pressure gauge; then calculate the mass flow Q through the long-neck nozzle by an iterative method according to the obtained data;

[0045] The specific design of the iterative method is as follows:

[0046] Step S310, Measure the incoming flow temperature t and humidity Hu through the inlet air temperature and humidity measurement points, and calculate the physical properties parameters of the incoming flow in combination with the ambient atmospheric pressure Pa. The physical properties parameters of the incoming flow include the incoming flow density , viscosity , isentropic index , etc.;

[0047] Step S320, According to the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outflow pipe wall, calculate the inner diameter temperature functions of the long-neck nozzle and the outflow pipe wall respectively, where T = T1 or T2; then calculate the inner diameter d of the long-neck nozzle and the inner diameter D of the outflow pipe in real time according to the inner diameter temperature function, and obtain the pipe diameter ratio ;

[0048] Step S330: Calculate the pressure difference from the static pressure Ps1 at the throat of the long-neck nozzle and the static pressure Ps0 of the upstream incoming flow of the long-neck nozzle obtained by the static pressure measuring points , and the pressure ratio ;

[0049] Step S340: Calculate the expansibility coefficient according to the pipe diameter ratio and in combination with the pressure ratio and the isentropic exponent ; It can be calculated using existing formulas.

[0050] Step S350: Calculate the parameter according to the expansibility coefficient , and set the initial value of the discharge coefficient of the long-neck nozzle to ;

[0051] Step S360: Let n = 1 in the Reynolds number calculation formula , is the discharge coefficient of the long-neck nozzle, is the Reynolds number; Substitute the initial value of the discharge coefficient of the long-neck nozzle into the Reynolds number calculation formula to obtain the Reynolds number iteration value , and continuously iterate the Reynolds number according to the Reynolds number iteration value ;

[0052] Step S370: Judge whether the Reynolds number satisfies the convergence judgment formula , m is a positive integer set by the user; If it is satisfied, the mass flow rate Q is output from the mass flow rate calculation formula ; If it is not satisfied, the iteration value of the discharge coefficient is calculated from the empirical formula of the discharge coefficient of the nozzle , and continue to iterate the Reynolds number.

[0053] Step S400: Flow calibration: Control the air supply of the fan to be calibrated, slowly increase the rotational speed to the calibration range, obtain the mass flow rate Q flowing through the long-neck nozzle in real time, and record the rotational speed of the fan to be calibrated. The fan to be calibrated continuously increases the rotational speed to increase the intake air flow until the flow calibration of the required calibration range is completed. If the calibration range exceeds the working range of a group of long-neck nozzles, collect multiple groups of long-neck nozzles to take over and complete the calibration work.

[0054] Step S500: Complete calibration: Remove the calibration device, complete the data processing and output, and end the calibration work.

[0055] Through the above design, by calculating the current inner diameter d of the long-neck nozzle and the inner diameter D of the outflow pipe in real time, the current thermal expansion and contraction conditions of the long-neck nozzle and the outflow pipe can be obtained, so that the mass flow rate Q flowing through the long-neck nozzle can be accurately obtained for accurate flow calibration; at the same time, by setting a rectifying grid upstream of the long-neck nozzle to rectify the gas flowing through the long-neck nozzle, the intake air uniformity and the accuracy of the flow measurement of the scene nozzle are ensured; by setting multiple measuring points for mass flow calculation, the flow standard device does not need to be installed at the inlet of the pipeline of the device to be calibrated, nor does it need to install multiple sets of calibration devices, which reduces costs and is convenient for installation and disassembly.

[0056] Finally, it should be noted that: in the attached drawings of the disclosed embodiments of the present invention, only the structures related to the disclosed embodiments of the present disclosure are involved, and other structures can refer to the general design. Without conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0057] Finally: The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for rapidly calibrating the flow rate of a fan, characterized in that the corresponding calibration device includes a long-neck nozzle (11), an outlet pipe (8), a rectifying grid (14), a pressure stabilizing section (3) and a transition section (2); the inlet end of the transition section (2) is connected to the outlet of the fan to be calibrated (1), and the outlet end is connected to the inlet end of the pressure stabilizing section (3); the outlet end of the pressure stabilizing section (3) is coaxially connected to the outlet pipe (8); a long-neck nozzle (11) is arranged inside the outlet pipe (8); a signal processor (6) is electrically connected to the long-neck nozzle (11), the signal processor (6) is electrically connected to a computer (7), and an atmospheric pressure gauge (5) is also connected to the signal processor (6); a porous medium (4) is arranged inside the pressure stabilizing section (3); wall static pressure holes are opened at the throat of the long-neck nozzle (11) and upstream of the outlet pipe (8), temperature sensors and static pressure sensors are arranged inside the outlet pipe (8) and the long-neck nozzle (11), the static pressure sensors are arranged inside the wall static pressure holes, and outlet pipe temperature measurement points (12), long-neck nozzle temperature measurement points (9), outlet pipe static pressure measurement points (13) and long-neck nozzle static pressure measurement points (10) are formed on the outlet pipe (8) and the long-neck nozzle (11); a rectifying grid (14) is arranged upstream of the long-neck nozzle (11), and the rectifying grid (14) is fixedly connected to the outlet pipe (8); inlet air temperature and humidity sensors are installed on the equal annulus upstream of the rectifying grid (14) to form inlet air temperature and humidity measurement points (15); The method includes: Estimate the flow rate range of the fan to be calibrated, determine the calibration range, select a long-neck nozzle that meets the calibration range, select an outlet pipe according to the inner diameter d of the long-neck nozzle, select a rectifying grid and a pressure stabilizing section according to the inner diameter D of the outlet pipe, and select a transition section with a size matching that of the pressure stabilizing section; Establish a calibration device: install the long-neck nozzle and the rectifying grid on the outlet pipe, and evenly distribute multiple static pressure measurement points circumferentially upstream and downstream of the inlet end face of the long-neck nozzle; evenly embed multiple temperature measurement points circumferentially at the throat of the long-neck nozzle and upstream of the outlet pipe; install multiple inlet air temperature and humidity measurement points on the equal annulus upstream of the rectifying grid, and install the atmospheric pressure gauge in the test environment; Obtain the static pressure Ps1 at the throat of the long-neck nozzle and the static pressure Ps0 of the oncoming flow upstream of the long-neck nozzle through the static pressure measurement points, obtain the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outlet pipe wall through the temperature measurement points, obtain the incoming flow temperature t and humidity Hu through the inlet air temperature and humidity measurement points, and obtain the atmospheric pressure Pa through the atmospheric pressure gauge; then calculate the mass flow rate Q flowing through the long-neck nozzle through an iterative method according to the obtained data; Control the air supply of the fan to be calibrated, increase the speed to the calibration range, obtain the mass flow rate Q flowing through the long-neck nozzle in real time, and record the speed of the fan to be calibrated. The fan to be calibrated continuously increases the speed to increase the intake air flow rate until the flow rate calibration of the required calibration range is completed; Remove the calibration device, complete the data processing and output, and end the calibration work.

2. The method for quickly calibrating the fan flow rate according to claim 1, wherein The specific design of the iterative method calculation is as follows: Measure the incoming flow temperature \(t\) and humidity \(Hu\) through the temperature and humidity measurement points of the incoming air, and calculate the physical property parameters of the incoming flow in combination with the ambient atmospheric pressure \(Pa\). The physical property parameters of the incoming flow include the incoming flow density \(\rho_1\), viscosity \(\mu_1\) and isentropic exponent \(\kappa\). Calculate the inner diameter temperature functions d of the long-neck nozzle and the outflow pipe wall surface respectively according to the real-time temperature T1 of the long-neck nozzle and the real-time temperature T2 of the outflow pipe wall surface T = f(T), where T = T1 or T2; then calculate the inner diameter d of the long-neck nozzle and the inner diameter D of the outflow pipe in real time according to the inner diameter temperature function, and obtain the pipe diameter ratio β = D / d; Obtain the static pressure \(Ps1\) at the throat of the long-neck nozzle and the static pressure \(Ps0\) of the incoming flow upstream of the long-neck nozzle from the static pressure measurement points, and calculate the pressure difference \(\Delta p = Ps0 - Ps1\), and the pressure ratio \(\tau = Ps0 / Ps1\). Calculate the expansibility coefficient \(\varepsilon\) according to the diameter ratio \(\beta\) in combination with the pressure ratio \(\tau\) and the isentropic exponent \(\kappa\). Calculate the parameter according to the expansibility coefficient ε And set the initial value of the flow coefficient of the long-neck nozzle; Let Reynolds number calculation formula Re d，n =A / C n n=1,C n is the discharge coefficient of the long-neck nozzle, Re d,n is the Reynolds number; substitute the initial value of the long-neck nozzle discharge coefficient into the Reynolds number calculation formula to obtain the Reynolds number iteration value Re d，1 , and according to the Reynolds number iteration value Re d，1 Reynolds number Re d,n Conduct continuous iterations; Judge the Reynolds number Re d,n to see if it satisfies the convergence judgment formula. If it does, calculate the mass flow rate Q from the mass flow rate calculation formula and output the mass flow rate Q. If it does not satisfy, calculate the iterative value C2 of the discharge coefficient from the empirical formula C n = f(Re d，n-1 ) of the nozzle discharge coefficient, and continue to iterate the Reynolds number.

3. The method for quickly calibrating the fan flow rate according to claim 2, characterized in that: The convergence judgment formula is m is a positive integer set by the user; the initial value of the discharge coefficient of the long-neck nozzle is C1 = 0.

995.

4. The method for rapid calibration of the fan flow rate according to claim 1, characterized in that: The inner diameter \(D\) of the outlet pipe is \(2d\) to \(2.5d\); the length of the rectifying grid is \(2D\) to \(2.5D\), and the diameter of the pressure stabilizing section is \(4D\) to \(5D\).

5. The method for quickly calibrating the fan flow rate according to claim 1, characterized in that: A plurality of static pressure measurement points are circumferentially distributed at a position \(1D\) upstream of the inlet end face of the long-neck nozzle, and a plurality of static pressure measurement points are circumferentially distributed at a position \(0.5D\) downstream of the inlet end face of the long-neck nozzle.

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