CN204831400U - Steady voltage formula low discharge wind speed amount of wind measuring device - Google Patents

Abstract

The utility model provides a pressure-stabilized small-flow wind speed and air volume measuring device, which belongs to the field of fluid measurement. It includes: a dynamic pressure stabilizing tank, a static pressure stabilizing tank, a differential pressure transmitter and two pressure taking units. The pressure taking unit is arranged in the air duct, and the dynamic pressure stabilizing tank, the static pressure stabilizing tank and the differential pressure transmitter are all located outside the air duct. Each pressure measuring unit includes an inner venturi tube, an outer venturi tube, a dynamic pressure measuring tube for measuring the inner venturi tube and a static pressure measuring tube for measuring the outer venturi tube, and the inner venturi tube is coaxially sleeved Inside the outer Venturi tube. The dynamic pressure measuring tubes of the two pressure taking units communicate with each other and the dynamic pressure stabilizing tank, the static pressure measuring tubes of the two pressure taking units communicate with each other and communicate with the static pressure stabilizing tank, the dynamic pressure stabilizing tank, the static pressure The surge tanks are also respectively connected with the differential pressure transmitters. The utility model is suitable for the measurement of wind speed and air volume of small-flow fluids, and can effectively avoid the problem that the pressure difference signal is lost due to too low pressure difference during the measurement process.

Description

Stabilized small flow wind speed and air volume measuring device

technical field

The utility model relates to the field of fluid measurement, in particular to a pressure-stabilized small-flow wind speed and air volume measuring device.

Background technique

At present, most of the measurement of boiler flue gas flow velocity and flow rate use single-point Pitot tube flowmeters. In actual application, the measurement method of the single-point Pitot tube flowmeter has the following problems: (1) Accurate measurement cannot be performed when the gas flow rate is small, and the measurement signal is very easy to lose. (2) The air flow flowing in the flue produces a very low differential pressure at low flow rates, resulting in problems such as the flow cannot be displayed or accurately measured, and the signal is missing.

Utility model content

The purpose of the utility model is to provide a steady-pressure small-flow wind speed and air volume measuring device, which avoids the problem of missing measurement signals due to small differential pressure, so as to realize the air volume and wind speed measurement of small flow fluids.

The utility model is achieved in that:

The pressure-stabilized small-flow wind speed and air volume measuring device is used to measure the gas flow rate and flow in the air duct, including: a dynamic pressure regulator tank, a static pressure regulator tank, a differential pressure transmitter and two pressure-taking units, the two described The pressure taking unit is arranged in the air duct, the dynamic pressure stabilizing tank, the static pressure stabilizing tank, and the differential pressure transmitter are all located outside the air duct, and each of the pressure taking units includes an inner A Venturi tube, an outer Venturi tube, a dynamic pressure measuring tube for measuring the inner Venturi tube and a static pressure measuring tube for measuring the outer Venturi tube, the inner Venturi tube is coaxially sleeved on the Inside the outer venturi;

The dynamic pressure measuring tubes of the two pressure taking units communicate with each other and the dynamic pressure stabilizing tank, and the static pressure measuring tubes of the two pressure taking units communicate with each other and communicate with the static pressure stabilizing tank, The dynamic pressure stabilizing tank and the static pressure stabilizing tank are also respectively connected to the differential pressure transmitter.

Preferably, the two pressure-taking units are arranged symmetrically along the axis of the air duct. The two pressure-taking units distributed axisymmetrically can measure the pressure information of the same fluid movement section, making the measured data more accurate and consistent.

Preferably, it also includes: a dynamic pressure three-way pipe and a static pressure three-way pipe, the dynamic pressure stabilizing tank is connected to the dynamic pressure measuring pipes of the two pressure-taking units through the dynamic pressure three-way pipe, and the The static pressure stabilizing tank is connected with the static pressure measuring tubes of the two pressure taking units through the static pressure three-way pipe. The three-way pipe has a simple structure and is easy to use. It is used to mix fluids in different pipelines and change the direction of fluid movement.

Preferably, the dynamic pressure measuring tube communicates with the inner venturi tube, and the static pressure measuring tube communicates with the outer venturi tube.

Preferably, the throat of the inner Venturi tube is provided with an inner pressure tapping hole, the throat of the outer Venturi tube is provided with an outer pressure tapping hole, and the dynamic pressure measuring tube extends through the inner pressure tapping hole. into the inner Venturi tube, and the static pressure measuring tube extends into the outer Venturi tube through the outer pressure-taking hole.

Preferably, it further includes: two connectors, the dynamic pressure stabilizing tank and the static pressure stabilizing tank are respectively connected to the differential pressure transmitter through one of the connectors. The positive and negative voltage regulator tanks are connected through the connectors, which can be connected conveniently and quickly, avoiding the separation of the positive and negative voltage regulator tanks from the differential pressure transmitter.

Preferably, it also includes: a sleeve rod, the outer Venturi tube is connected to the inner Venturi tube through the sleeve rod, the sleeve rod is arranged along the radial direction of the inner Venturi tube, the One end of the socket rod is connected to the outer wall of the inner Venturi tube, and the other end of the socket rod is connected to the inner wall of the outer Venturi tube. The socket rod connects the outer Venturi tube and the inner Venturi tube as a whole, preventing relative movement between the two tubes during the measurement process, thereby reducing the interference received during the fluid movement and ensuring the accuracy of the measurement data.

Preferably, it also includes: a fixing rod, the outer Venturi tube is arranged in the air duct through the fixing rod, the fixing rod is arranged along the radial direction of the outer Venturi tube, one end of the fixing rod is connected to The outer tube wall of the outer Venturi tube is connected, and the other end of the fixing rod is connected with the air duct. The air duct and the outer Venturi tube are connected by a fixed connection, which is suitable for an environment where the air duct is relatively small, and can avoid the influence of the fixed rod on the normal flow of the fluid.

Preferably, a wing plate is also included, and the outer Venturi tube is connected in the air duct through the wing plate. The connection of the wing plates is more firm and stable, and the outer Venturi tube is less likely to shake.

Preferably, both the dynamic pressure measuring tube and the static pressure measuring tube are made of steel. The steel has high strength, is not easy to damage, can withstand the impact of external fluids, and prolongs the service life.

The beneficial effects of the utility model:

The utility model provides a pressure-stabilizing small-flow wind speed and air volume measuring device. The device includes two sets of pressure-taking units, a dynamic pressure-stabilizing tank, and a static-pressure stabilizing tank. Each group of pressure-taking units includes two A venturi tube. The device can obtain stable differential pressure when the fluid flow rate is low, so that the differential pressure transmitter can accurately obtain differential pressure data, and then obtain measurement data such as wind speed and air volume. It adopts a double venturi tube structure that is socketed as one. The outer venturi tube rectifies the airflow entering the inner venturi tube, and the air flow in the inner venturi tube is more stable, which is conducive to measurement. The setting of the dynamic pressure stabilizing tank and the static pressure stabilizing tank enables the measuring device to obtain sufficient pressure difference when the air flow in the air duct is small, so that the differential pressure transmitter can work normally.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following drawings will be briefly introduced in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention. Therefore, it should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained according to these drawings without creative work.

Fig. 1 is the structural schematic diagram of the outer Venturi tube in the pressure-stabilized small flow rate air volume measuring device provided by the embodiment of the utility model;

Fig. 2 is the schematic diagram of the axial section structure of the outer Venturi tube in Fig. 1;

Fig. 3 is a structural schematic diagram of the inner Venturi tube in the pressure-stabilized small flow velocity air volume measuring device provided by the embodiment of the present invention;

Fig. 4 is a schematic diagram of the axial section structure of the inner Venturi tube in Fig. 3;

Fig. 5 is a structural schematic diagram of the pressure-taking unit in the pressure-stabilizing small flow rate air volume measuring device provided by the embodiment of the utility model; (not including the socket rod)

Fig. 6 is a structural schematic diagram of the pressure-taking unit in the pressure-stabilized small-flow rate air volume measuring device provided by the embodiment of the present invention;

Fig. 7 is a structural schematic diagram of a pressure-stabilized small flow rate air volume measuring device provided by an embodiment of the present invention.

Explanation of reference signs

Outer Venturi 101; second equal-diameter inlet section 102; second constriction section 103;

second constant diameter throat section 104; second diverging section 105; inner venturi tube 201;

The first constriction section 202; the first equal-diameter throat section 203; the first diverging section 204;

Static pressure measuring tube 301; dynamic pressure measuring tube 302; differential pressure transmitter 401;

Dynamic pressure surge tank 402; static pressure surge tank 403; air duct 501.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the utility model more clear, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the utility model. Obviously, the described The embodiments are some embodiments of the present utility model, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" The orientation or positional relationship indicated by etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that is usually placed when the product of the utility model is used. It is only for the convenience of describing the utility model and simplifying the description, rather than Any indication or implication that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should not be construed as limiting the invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In the description of the present utility model, it should also be noted that, unless otherwise specified and limited, the terms "setting", "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection , can also be detachably connected, or integrally connected; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediary, and can be internal communication between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present utility model in specific situations.

When measuring small flow and low velocity gas, the flow of fluid can pass through the pressure difference at a certain point in the section of the fluid flow direction, and then measure the flow of fluid passing through the section within a certain period of time. However, due to the small pressure difference of low-speed fluid flowing through a certain interface, it is not easy to be measured, and due to the small flow rate, the pressure signal may be unstable or even lost. In order to solve the above problems, it is usually necessary to amplify the pressure difference and keep the pressure difference stable, so as to accurately measure the flow rate and flow rate of low flow rate and small flow fluid. The present inventor, through research, proposed a measuring device for measuring the wind speed and air volume of fluids with small flows, and realized the measurement of fluids with low velocity and small flows.

Referring to FIG. 1 to FIG. 7 , this embodiment provides a small-flow wind speed and air volume measuring device with constant pressure, which is used to measure the gas flow rate and flow rate in the air duct. The measuring device includes: a dynamic pressure stabilizing tank 402, a static pressure stabilizing tank 403, a differential pressure transmitter 401 and two pressure-taking units. Wherein, two pressure-taking units are arranged in the air duct 501 , and the dynamic pressure stabilizing tank 402 , the static pressure stabilizing tank 403 , and the differential pressure transmitter 401 are all located outside the air duct 501 .

Each pressure-taking unit comprises an inner Venturi tube 201, an outer Venturi tube 101, a dynamic pressure measuring tube 302 for measuring the inner Venturi tube 201, and a static pressure measuring tube 301 for measuring the outer Venturi tube 101. The Venturi tube 201 is coaxially sleeved in the outer Venturi tube 101 . The dynamic pressure measuring tubes 302 of the two pressure taking units communicate with each other and the dynamic pressure stabilizing tank 402, the static pressure measuring tubes 301 of the two pressure taking units communicate with each other and communicate with the static pressure stabilizing tank 403, and the dynamic pressure stabilizing tank 403 communicates with each other. The tank 402 and the static pressure stabilizing tank 403 are also respectively connected to the differential pressure transmitter 401 .

Differential pressure transmitter is a kind of equipment commonly used in industrial practice. It is widely used in various industrial automatic control environments, involving hydraulic, electric power, petrochemical and other fields. Differential pressure transmitter is a kind of equipment that measures the pressure difference of conveying medium in various pipeline systems, and converts the measured differential pressure value into current signal output through data conversion. Differential pressure transmitters are different from ordinary pressure transmitters. They all have two pressure ports, positive pressure end and negative pressure end, and the two ports correspond to fluid inputs of different pressures.

The Venturi tube is made based on the Venturi effect, and generally includes an equal-diameter inlet section, a constriction section, an equal-diameter throat section, and a diverging section connected in sequence. The diameter of the constriction section gradually decreases from the equal-diameter inlet section to the equal-diameter throat section; the diameter of the diverging section increases as it gradually moves away from the equal-diameter throat section. By measuring the pressure difference in the pipeline, the flow rate can be obtained. For liquids, the Venturi tube is directly installed with a pressure measuring tube to measure the pressure difference. For gases, the pressure of the fluid needs to be output to the pressure measurement device through the pipeline, and the pressure measurement device is used to measure the pressure difference. In this embodiment, the inner venturi tube 201 includes a first constriction section 202, a first equal-diameter throat section 203, and a first diverging section 204, and the outer venturi tube 101 includes a second equal-diameter inlet section 102, a second constriction section 103 , the second equal-diameter throat section 104 and the second diverging section 105 . The outer Venturi tube 101 acts as a suction and rectifier to the inner Venturi tube 201. The fluid enters the inner Venturi tube 201 and moves toward its throat section. In the contraction section, the fluid is compressed. , the pressure of the fluid stabilizes, and the measuring device obtains an increase in pressure difference.

The working principle of the measuring device is: the pressure taking unit is used to lead out the air in the air duct 501, and then amplifies and stabilizes the delivery pressure of the fluid through the surge tank, so as to prevent the flow and velocity of the fluid in the air duct from being too small to Effective working pressure is generated to ensure that the differential pressure transmitter 401 can obtain accurate differential pressure. The air pressure amplified and stabilized by the surge tank enters the differential pressure transmitter 401, and the pressure directly acts on the diaphragm of the differential pressure transmitter 401, causing the diaphragm to produce a micro-displacement proportional to the medium pressure, so that The resistance value of the sensor inside the differential pressure transmitter 401 changes and is finally converted into a differential pressure signal.

In order to facilitate the connection of the inner Venturi tube 201 and the outer Venturi tube 101 in the pressure taking unit, the pressure-stabilized small-flow wind speed and air volume measuring device also includes a sleeve rod, and the outer Venturi tube 101 is connected to the inner Venturi tube through the sleeve rod. 201 connection. The sleeve rod is arranged along the radial direction of the inner Venturi tube 201 , one end of the sleeve rod is connected with the outer tube wall of the inner Venturi tube 201 , and the other end of the sleeve rod is connected with the inner tube wall of the outer Venturi tube 101 . The sleeve rod arranged radially connects the inner Venturi tube 201 and the outer Venturi tube 101, and the relative movement between the two is not easy to occur, and the disturbance is small when the air flows through the two, and the stable air pressure is conducive to improving the accuracy of measurement .

Preferably, the pressure-stabilized small-flow wind speed and air volume measuring device further includes a fixed rod, and the outer Venturi tube 101 is arranged in the air duct 501 through the fixed rod. The fixed rod is arranged along the radial direction of the outer Venturi tube 101 , one end of the fixed rod is connected with the outer tube wall of the outer Venturi tube 101 , and the other end of the fixed rod is connected with the air duct 501 . As another implementation, the pressure-stabilized small-flow wind speed and air volume measurement device also includes a wing plate, the outer Venturi tube 101 is connected to the air duct 501 through the wing plate, and the outer Venturi tube 101 can be fixed more firmly by the wing plate In the air duct 501, the shaking of the outer Venturi tube 101 is reduced, so that the pressure taking unit can be fixed.

The pressure output end of the dynamic pressure stabilizing tank and the pressure output end of the static pressure stabilizing tank are respectively connected to the positive pressure end interface and the negative pressure end interface of the differential pressure transmitter 401, and the pressures of different sizes of the two interfaces act on the differential pressure Pressure transmitter 401, and then convert the pressure difference into electrical signal output. In order to facilitate the connection of the dynamic pressure stabilizing tank, the static pressure stabilizing tank and the differential pressure transmitter 401, the stabilizing type small flow wind speed and air volume measuring device also includes: two connectors, the dynamic pressure stabilizing tank 402, the static pressure The pressure-stabilizing tanks 403 are respectively connected to the differential pressure transmitter 401 through a connection head. The connector can be a quick connector for air or a threaded steel pipe. Both the dynamic pressure stabilizing tank and the static pressure stabilizing tank have an air inlet port and an air outlet port for stabilizing the pressure output; when the pressure is too low, the pressure output can be adjusted. The surge tank is a commercially available device, and this embodiment does not describe its specific structure in detail.

Preferably, the two pressure-taking units are arranged symmetrically along the axis of the air duct 501 . Since the two pressure measuring units are arranged side by side in the air duct 501 in parallel, and both are in the same cross section of the air duct 501, the pressures at the measurement points of the two pressure measuring units are kept consistent, and the obtained pressure is more accurate. When the inner diameter of the air duct 501 is constantly changing, the flow rate, flow velocity, pressure, etc. of the air in the air duct 501 will change. The pressure measured by the two pressure measuring units is inconsistent, resulting in inaccurate pressure data, which may lead to inaccurate measurement of fluid flow and flow velocity. In addition, the two pressure-taking units are arranged symmetrically along the axis of the air duct 501, the air in the air duct 501 passes through the two pressure-taking units at the same time, and leaves the two pressure-taking units at the same time, thereby avoiding the gap between the two pressure-taking units. The mutual interference of the airflow makes the measured air volume and wind speed accurately reflect the real situation of the air in the air duct 501 .

In order to measure fluid with a small flow rate, the dynamic pressure measuring tubes 302 of the two pressure-taking units are connected, and the static pressure measuring tubes of the two pressure-taking units are connected. Because the two dynamic pressure measuring tubes 302 are connected, the airflows obtained by the two dynamic pressure measuring tubes 302 can be combined together, thereby improving the measured value of the dynamic pressure; correspondingly, because the two static pressure measuring tubes are connected, the two The pressures obtained by the static pressure measuring tubes can be combined to improve the negative pressure measurement. As an implementation, the dynamic pressure measuring tube 302 can be a trident tube, the two tubes of the trident tube are respectively connected to an inner Venturi tube 201, and the third tube is connected to the dynamic pressure stabilizing tank 402; the static pressure measurement The pipe 301 can also be a trifurcated pipe, two branch pipes of the trifurcated pipe are respectively connected to an outer Venturi tube 101 , and the third branch pipe is connected to the static pressure surge tank 403 . As another implementation, the pressure-stabilized small-flow wind speed and air volume measurement device also includes: a dynamic pressure three-way pipe, a static pressure three-way pipe, and two pressure-taking units. The dynamic pressure three-way pipe is connected, and the static pressure measuring pipe 301 and the static pressure stabilizing tank 403 of the two pressure taking units are connected through the static pressure three-way pipe. The use of the three-way pipe enables the dynamic pressure measuring tubes 302 of the two pressure taking units to be set relatively independently, and the static pressure measuring tubes 301 of the two pressure taking units can also be set relatively independently, thereby reducing the pressure of the dynamic pressure measuring tubes 302. 1. The difficulty of laying the static pressure measuring tube 301, the installation position and installation attitude of the dynamic pressure measuring tube 302 and the static pressure measuring tube 301 can be adaptively adjusted according to the structural characteristics of the air duct 501 and the external installation environment.

The dynamic pressure measuring tube 302 communicates with the inner Venturi tube 201, the static pressure measuring tube 301 communicates with the outer Venturi tube 101, the dynamic pressure measuring tube 302 is used to measure the pressure at the throat of the inner Venturi tube 201, and the static pressure measuring tube 301 Used to measure the pressure at the inlet section of the outer venturi 101. Preferably, the inner venturi tube 201 is provided with an inner pressure tapping hole, the outer venturi tube 101 is provided with an outer pressure tapping hole, and the dynamic pressure measuring tube 302 extends into the inner venturi tube 201 through the inner pressure tapping hole, and the static pressure measurement The tube 301 extends into the outer Venturi tube 101 through the outer pressure sensing hole. By directly setting the pressure-taking holes at the measurement points, more accurate measurement values can be obtained, and troublesome installation of the dynamic pressure measurement tube 302 and the static pressure measurement tube 301 can be avoided. Since the dynamic pressure measuring tube 302 and the static pressure measuring tube 301 need to transmit the pressure of the air in the air duct 501, the change of the pipe diameter will affect the normal transmission of pressure. Therefore, the dynamic pressure measuring tube 302 and the static pressure measuring tube 301 are all made of steel Production, steel has high strength and bending resistance, which can reduce the occurrence of extrusion, bending, etc., so as to ensure the normal transmission of pressure.

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (10)

1. A pressure-stabilizing type small-flow wind speed and air volume measuring device, which is used to measure the gas flow rate in the air duct, is characterized in that it includes: a dynamic pressure stabilizing tank, a static pressure stabilizing tank, a differential pressure transmitter and two A pressure-taking unit, the two pressure-taking units are arranged in the air duct, the dynamic pressure stabilizing tank, the static pressure stabilizing tank, and the differential pressure transmitter are all located outside the air duct, each The pressure-taking units all include an inner venturi tube, an outer venturi tube, a dynamic pressure measuring tube for measuring the inner venturi tube and a static pressure measuring tube for measuring the outer venturi tube, the inner venturi tube The Venturi tube is coaxially sleeved in the outer Venturi tube; The dynamic pressure measuring tubes of the two pressure taking units communicate with each other and the dynamic pressure stabilizing tank, and the static pressure measuring tubes of the two pressure taking units communicate with each other and communicate with the static pressure stabilizing tank, The dynamic pressure stabilizing tank and the static pressure stabilizing tank are also respectively connected to the differential pressure transmitter. 2 . The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1 , wherein the two pressure-taking units are arranged symmetrically along the axis of the air duct. 3 . 3. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1 or 2, further comprising: a dynamic pressure three-way pipe and a static pressure three-way pipe, and the dynamic pressure surge tank passes through the The dynamic pressure three-way pipe is connected to the dynamic pressure measuring pipes of the two pressure-taking units, and the static pressure tank is connected to the static pressure measuring pipes of the two pressure-taking units through the static pressure three-way pipe. 4. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1, wherein the dynamic pressure measuring tube communicates with the inner Venturi tube, and the static pressure measuring tube communicates with the outer Venturi tube. The tube is connected. 5. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 4, wherein the inner Venturi tube is provided with an inner pressure-taking hole, and the outer Venturi tube is provided with an outer pressure-taking hole, so The dynamic pressure measuring tube extends into the inner venturi tube through the inner pressure-taking hole, and the static pressure measuring tube extends into the outer venturi tube through the outer pressure-taking hole. 6. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1, further comprising: two connectors, the dynamic pressure surge tank and the static pressure surge tank respectively pass through a The connector is connected to the differential pressure transmitter. 7. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1, further comprising: a sleeve rod, the outer Venturi tube is connected to the inner Venturi tube through the sleeve rod , the sleeve rod is arranged along the radial direction of the inner Venturi tube, one end of the sleeve rod is connected to the outer wall of the inner Venturi tube, and the other end of the sleeve rod is connected to the outer tube wall. The inner tube wall of the Turi canal is connected. 8. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 7, further comprising: a fixed rod, the outer Venturi tube is arranged in the air duct through the fixed rod, and the fixed rod The rod is arranged along the radial direction of the outer Venturi tube, one end of the fixed rod is connected with the outer tube wall of the outer Venturi tube, and the other end of the fixed rod is connected with the air duct. 9 . The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 7 , further comprising a wing plate, through which the outer Venturi tube is connected in the air duct. 10 . 10. The pressure-stabilized small-flow wind speed and air volume measuring device according to claim 1 or 9, wherein the dynamic pressure measuring tube and the static pressure measuring tube are both made of steel.