CN107270982B - An experimental device for airflow measurement with a moving measuring device - Google Patents

Abstract

The invention provides an air flow measurement experimental device in which the measurement device moves, including an air flow generation device, a Pitot static pressure tube system, a Venturi flowmeter system, an orifice flowmeter system, a flow control system and a flow channel; the air flow generation device generates The airflow flowing in the flow channel, the flow control system controls the size of the airflow, the Pitot static pressure tube system, the Venturi flowmeter system, and the orifice flowmeter system are installed on the flow channel to measure the airflow in the flow channel. flow, the flow control system, pitot static pressure pipe system, venturi flowmeter system, and orifice flowmeter system are respectively connected with the data acquisition controller, and the data acquisition controller is connected with the data display device, and the data acquisition controller is connected with the data display device. Pitot static tube system includes pitot tube and pitot tube moving device, the moving device can make the pitot tube move freely in the measured section. The pitot tube can be moved on the guide rail of the mobile device, which increases the flow rate of the measurement at different positions, improves the measurement accuracy, and at the same time, it is convenient to observe the change of the flow velocity at different positions, and it is convenient for teaching.

Description

An experimental device for airflow measurement with a moving measuring device

technical field

The invention relates to a gas heat exchanger and an air flow measurement experimental device used in the heat exchanger, belonging to the field of heat exchange and fluid mechanics.

Background technique

When the gas heat exchanger performs heat exchange, the heat exchange effect is obviously different due to the uneven inlet temperature of the hot fluid, and the heat exchange effect is not ideal due to the measurement error of the hot fluid flow.

In addition, the measurement of gas velocity and flow is a fundamental measurement of fluid mechanics. In various fields of experimental research and engineering applications, various flow velocity measurement problems are raised, such as determining the air flow rate of the intake manifold controlled by the ECU, determining the airspeed of the aircraft, etc. Usually, the application principles and methods of flowmeters we use to measure the flow of fluids are different. Among them, differential pressure flowmeters are widely used, and the commonly used types include Venturi flowmeters, orifice flowmeters, Pitot static pressure tubes, etc. . Different types of flowmeters have different use methods and advantages. Even at different airflow rates, different measurement methods will show different accuracy. For example, there will be flow measurement devices on boilers and other air supply equipment. Through the measurement and comparison of the device, guidance can be provided for it, and different flow measurement devices can be selected for different air volumes to obtain more accurate measurement results. Therefore, in the teaching process, it is necessary to invent an experimental device that can intuitively compare the similarities and differences of various measurement methods, which is convenient for students to learn.

SUMMARY OF THE INVENTION

In view of the above problems, the purpose of the present invention is to provide a gas heat exchanger that can reach an ideal temperature, and also to provide an experimental device that can comprehensively measure various flowmeters, so as to be used in the gas heat exchanger.

The technical scheme of the present invention is as follows:

An experimental device for measuring gas flow conditions, comprising an airflow generating device, a Pitot static pressure tube system, a Venturi flowmeter system, an orifice flowmeter system, a flow control system and a flow channel; the airflow generating device generates an airflow flowing in the flow channel , the flow control system controls the size of the airflow, the Pitot static pressure tube system, the Venturi flowmeter system, and the orifice flowmeter system are installed on the flow channel to measure the flow of the airflow in the flow channel, and the flow control The system, the pitot static pressure tube system, the venturi flowmeter system, and the orifice plate flowmeter system are respectively connected with the data acquisition controller, and the data acquisition controller is connected with the data display device.

Preferably, along the direction of the airflow, an airflow generating device, a Pitot static pressure tube system, a Venturi flowmeter system, an orifice flowmeter system and a flow control system are sequentially arranged in the flow channel.

Preferably, the airflow generating device comprises a centrifugal blower, a conical air inlet pipe and an air flow channel, the air flow channel is connected with the conical air inlet pipe, and the blower is connected with the air flow channel; wherein the flow channel where the Pitot static pressure pipe system is located is Square section, the flow channel where the Venturi flowmeter system and the orifice plate flowmeter system are located are all circular.

Preferably, the pitot-static tube system includes a pitot-static tube and a pitot tube moving device, and the moving device can make the pitot tube move freely within the measured section.

Preferably, in the venturi flowmeter system, the length of the front air passage at the installation position of the venturi flowmeter is greater than five times the diameter of the flow passage, and the length of the rear end is greater than three times the diameter of the flow passage.

Preferably, the flow control system is a baffle and a moving device installed at the end of the airflow channel, and the airflow is controlled by controlling the distance between the baffle and the outlet of the channel.

Preferably, the side length of the inner section of the square channel of the pitot-static pipe system is L, and the radius of the circular channel is R, then the minimum distance between the pitot-static pipe system and the venturi flowmeter system S1>=a* ((R/2)2+L2)(1/2), where a is a parameter, 22.54<a<32.18;

The distance between the Venturi flowmeter system and the orifice flowmeter system S2>=b*R, where b is a parameter, 10<b<23.

Compared with the prior art, the present invention has the following advantages:

1) The pitot tube can be moved on the guide rail of the mobile device, which increases the flow rate of the measurement at different positions, improves the accuracy of the measurement, and at the same time, it is convenient to observe the change of the flow rate at different positions, which is convenient for teaching.

2) By setting up multiple flow rate measuring devices on one test bench, multiple flow meters can work at the same time, and the measurement data can be displayed through the display device, which is convenient for data comparison, and can quickly select the measuring devices with small errors under different flow rates.

3) The purpose of completing the measurement of airflow flow rate in multiple methods on one experimental device is realized, and the similarities and differences of different flow meters can be compared intuitively. The operation is simple and the teaching is convenient.

4) Through a large number of experiments, the optimal distance between each measurement device is determined, which avoids the increase of errors caused by the gas disturbance between the various measurement devices, thereby greatly increasing the measurement accuracy.

Description of drawings

Fig. 1 is the structure schematic diagram of the heat exchanger of the present invention;

Fig. 2 is the schematic diagram of the experimental apparatus of the present invention;

Fig. 3 is the overall plan view of the experimental device of the present invention;

Fig. 4 is the schematic diagram of the pitot-static pipe system of the present invention;

Fig. 5 is the side view of the pitot tube moving device of the present invention;

Fig. 6 is the schematic diagram of the venturi flowmeter system of the present invention;

Fig. 7 is the schematic diagram of the orifice plate flowmeter system of the present invention;

8 is a schematic diagram of a tilting pressure gauge system and a digital display system of the present invention;

Fig. 9 is the schematic diagram of the control system of the present invention;

Fig. 10 is a schematic view of the airflow generating device of the present invention.

The reference numbers are as follows:

1 conical intake pipe, 2 centrifugal fan, 3 pitot static pressure pipe system, 4 venturi flowmeter system, 5 orifice plate flowmeter, 6 tilting pressure gauge, 7 flow control system, 8 pitot tube, 9 Pitot Managed mobile device, 10 air passages, 11 high pressure pressure measuring tubes, 12 low pressure pressure measuring tubes, 13 Venturi flowmeters, 14 high pressure pressure measuring tubes, 15 low pressure pressure measuring tubes, 16 tilting pressure gauges, 17 thermometers, 18 gears Board, 19 control knobs, 20 digital display devices, 21 data acquisition controllers, 22 heat pipe condensation ends, 23 heat pipe evaporation ends, 24 cold air runners, 25 hot gas runners, 26 bumps, 27 grooves

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a gas heat exchanger. As shown in the figure, the gas heat exchanger includes a hot gas flow channel 25, a cold air flow channel 24 and a heat pipe. The heat pipe includes an evaporation end 23 and a condensation end 22, so The evaporation end 23 is located in the hot gas flow channel 25, and the condensation end 22 is located in the cold air flow channel 24. The inlet of the hot gas flow channel 25 is provided with a temperature sensor and a flow sensor for measuring the gas temperature and flow rate entering the hot gas flow channel. Gas flow, a valve is set at the inlet of the cold air flow channel 24 to control the flow of cold air entering the cold air flow channel, the heat exchanger also includes a controller, the controller is connected to a temperature sensor, a flow sensor, and a control valve Data connection, the controller automatically controls the opening of the valve according to the measured gas temperature and gas flow.

The controller controls the valve according to the combination of gas temperature and gas flow. The specific control method is as follows: control parameter Q=(gas temperature-reference temperature)*gas flow, if the measured control parameter Q increases, it will automatically increase The opening of the valve, if the measured control parameter Q decreases, the opening of the valve is automatically reduced.

Through the above-mentioned intelligent control, the flow of cold air participating in heat exchange can be controlled with the change of the airflow temperature and flow rate of the hot fluid, so that the outlet temperature of the cold and cold air can be kept consistent, and the temperature of the cold air outlet can be prevented from being too high or too low. Thus affecting the use effect.

Preferably, the hot gas is boiler exhaust gas. Used in boiler flues, it can also avoid low temperature corrosion. By controlling the flow of cold air, the exhaust gas temperature can be prevented from being too high or too low, resulting in heat waste or low-temperature corrosion.

Preferably, the hot gas is hot air.

Preferably, the reference temperature is 20-30°C.

It has been found in the operation practice of heat exchangers that not all other measuring devices are suitable for measuring flow in heat exchangers, and some measuring devices are used in different environments and will produce large errors, especially because of the gas velocity. The resulting error is more different, resulting in poor operation effect. Therefore, in order to ensure good operation effect, appropriate measurement tools must be selected in different heat exchange environments. Therefore, it is necessary to develop a new experimental device in order to test the error of measurement tools in different environments, so as to select a measurement tool with a small error.

Figure 2 shows a simple schematic diagram of a new experimental setup for airflow measurement. The gas flow measurement experimental device shown in Figure 2 includes an airflow generation device, a Pitot static pressure tube system 3, a Venturi flowmeter system 4, an orifice flowmeter system 5, a flow control system 7 and a flow channel; The device generates the airflow flowing in the flow channel, the flow control system 7 controls the size of the airflow, the Pitot static pressure tube system 3, the Venturi flowmeter system 4, and the orifice flowmeter system 5 are installed on the flow channel, using In order to measure the flow rate of the air flow in the flow channel, the flow control system 7, the Pitot static pressure tube system 3, the Venturi flowmeter system 4, and the orifice flowmeter system 5 are respectively connected with the data acquisition controller 21 for data connection. The acquisition controller 21 is connected 20 to the data display device.

Through the above-mentioned flow velocity measurement experimental device, the airflow velocity measurement of various devices can be completed on one experimental device, and each measurement data can be displayed through the display device, which is convenient for comparing the advantages and disadvantages of the given measurement tools, and also facilitates teaching, so that students can Can intuitively observe various speed measuring tools and speed measuring methods.

Preferably, as shown in FIG. 9 , the flow control system 7 includes a baffle 18 and a moving device control knob 19 installed at the end of the airflow channel. The baffle is connected to the outlet of the airflow channel through a screw, and the baffle is changed by rotating the control knob. The distance from the channel outlet controls the airflow. In addition, the air flow can also be controlled by other reasonable means, such as using a variable frequency air pump or controlling the air flow at the inlet.

Preferably, the experimental device includes a high-precision gas flowmeter. Preferably, the high-precision gas flowmeter is arranged between the baffle 18 of the airflow channel 10 and the orifice plate flowmeter system, and the high-precision gas flowmeter is connected to the orifice flowmeter system. The data acquisition controller 21 is connected with data, the flow control system 7 can control the gas flow, and the gas flow measured by the high-precision gas flow meter is displayed on the display device 20 . The data measured by the high-precision gas flowmeter is comparative data, and the data measured by the Pitot static pressure pipe system 3, the Venturi flowmeter system 4, and the orifice flowmeter system 5 are respectively compared with the data measured by the high-precision gas flowmeter. , to determine the size of the error, in order to determine the appropriate flowmeter for use in different applicable environments.

Because it is used as a comparison data, the high-precision gas flow meter requires high precision, that is, the error is small, and the measurement error is within 0.5%, and preferably, the error is within 0.2%.

Preferably, the high-precision gas flow meter can be arranged in other positions of the gas flow channel 10, for example, arranged between the gas flow generating device and the Pitot static pipe system.

Preferably, as shown in Figure 3, in order to ensure that each measuring device does not affect each other, the flow channel is a segmented structure, divided into four sections, Pitot static pressure pipe system, Venturi flowmeter system, orifice flow rate The meter system is installed between the air passages in sequence, and each part is connected by flanges. By setting the flow channels in sections, it can be ensured that the airflow from each flow channel will not interfere with the subsequent measuring devices.

As shown in FIG. 3 , the pitot static pressure tube system includes a pitot tube and a tilting pressure gauge 6 , the pitot tube is connected to the tilting pressure gauge 6 , and the tilting pressure gauge 6 is connected to the data acquisition controller 21 . The data connection is performed, and the flow rate of the gas is obtained through the data acquisition controller 21 .

Figure 3-4 shows the pitot static pressure tube system of the device. The pitot tube moving device 9 is installed on the wall of the airway, and the pitot tube 8 can move freely in the measurement section with the assistance of the moving device 9 to realize multi-point measurement and take the average value. function.

As shown in FIG. 5 , the moving device 9 includes a slider, the pitot tube is arranged in the slider, and the slider includes a convex block 26 , and the convex block 26 is disposed in the concave cavity of the airway tube wall. In the groove 27 , the protrusion 26 can move in the groove 27 , and the free movement of the pitot tube 8 is realized by the movement of the protrusion 26 .

Preferably, after the free movement of the pitot tube 8, sealing measures are taken to prevent air leakage.

As shown in Figure 5, in order to reduce the influence of the device on the air flow in the airway, the moving device adopts sliding grooves on the wall surface of the airway to realize lateral movement, and lubricating oil is applied to the contact surface, which is convenient for movement at the same time. To achieve the purpose of increasing air tightness. In addition, the pitot tube can move up and down on the guide rail of the mobile device to realize the function of longitudinal movement.

Figure 6 shows the Venturi system of the device. The Venturi flowmeter 13 is directly installed between the two air flow passages. It should be noted here that when the Venturi flowmeter is installed, the length of the straight pipe section at the front end should be greater than 5 times the diameter. , the length of the straight pipe section at the rear end should be greater than 2 times the diameter. During measurement, the high-pressure measuring tube 11 of the Venturi flowmeter measures a larger value, and a tiltable pressure gauge with a larger range is selected, and the low-pressure pressure measuring tube 12 is connected to a pressure gauge with a smaller range.

Figure 7 shows the orifice flowmeter system of the device. The orifice flowmeter 10 is directly installed on the airflow channel, similar to the Venturi flowmeter. Tube 15 is connected to a pressure gauge of smaller range.

Figure 8 shows the tilting pressure gauge system and digital display system of the device. The shown tilting pressure gauge 16 is divided into two sizes with different ranges, which can easily read the air flow measured by the pitot tube and other measuring devices. Static pressure or differential pressure. During measurement, the inclination angle of the tiltable pressure gauge can be increased to obtain higher sensitivity, but at the same time, since the pressure measurement range decreases with the increase of the inclination angle, the operator needs to adjust the use according to the measured airflow. The thermometer 17 can measure the ambient temperature at that time when the experiment requires.

Preferably, the digital display device 20 includes a digital inspection instrument and a differential pressure transmitter. Through the differential pressure transmitter, the differential pressure measured by the measuring device can be converted into an electrical signal, and sent to the inspection instrument to realize the digital signal of the measurement result. show.

The tilting pressure gauge 16 is connected with the data acquisition controller 21 for data connection, and the flow rate of the gas is obtained through the data acquisition controller 21 .

Of course, for the convenience of presentation, Figure 3 only shows a tilting pressure gauge. But preferably, the Pitot static pressure pipe system 3, the Venturi flowmeter system 4, and the orifice plate flowmeter system 5 are respectively connected with different tilting pressure gauges, so that multiple sets of data can be measured at the same time.

Fig. 10 shows an airflow generating device of an airflow measuring device. The centrifugal fan 2 is connected with the conical air intake pipe 1, and supplies air to the whole device through a section 3 of the air passage. The airflow channel is connected to the conical air intake pipe 1, and the fan 2 is connected to the airflow channel.

Preferably, the flow channel where the pitot static pressure pipe system is located has a square cross section, and the flow channels where the Venturi flowmeter system and the orifice plate flowmeter system are located are all circular.

In practice, it is found that for Pitot static pressure pipe system 3, Venturi flowmeter system 4, orifice plate flowmeter system 5, the distance between them must be greater than a certain distance, otherwise the gas from the previous measuring tool will not flow sufficiently. As a result, the measurement results are inaccurate. Therefore, a distance must be set between each measurement tool to make the gas in the flow channel flow sufficiently to ensure the accuracy of the measurement.

Experiments found that the distance between the pitot static pressure pipe system 3, the venturi flowmeter system 4, the orifice plate flowmeter system 5, and the flow control system 7 is related to the diameter of the flow channel. Under normal circumstances, the distance between each measuring tool is longer and farther, but considering the cost problem, space problem and the error problem caused by gas leakage due to the consideration of the longer distance, the present invention obtains through a large number of experiments. the best distance formula.

The flow channel where the pitot static pressure pipe system is located is a square section, and the flow channel where the Venturi flowmeter system and the orifice plate flowmeter system are located are all circular. In this case, the square channel inner section of the pitot static pressure pipe system The length of the side is L and the radius of the circular channel is R, then the minimum distance S1>=a*((R/2) ² +L ² ) ^{(1/ 2)} , where a is a parameter, 22.54<a<32.18.

Preferably, 35.34*((R/2) ² +L ² ) ^(1/2) <=S1<=46.32*((R/2) ² +L ² ) ^(1/2) .

Preferably, the a increases as (R/2) ² +L ² increases. Preferably, the a increases with the increase of (R/2) ² +L ² .

It is found through experiments that the constant change of the amplitude of a with (R/2) ² +L ² will lead to more accurate results and greatly improve the accuracy of the measurement data.

Preferably, 25.52<a<28.24.

The distance between the Venturi flowmeter system and the orifice flowmeter system S2>=b*R, where b is a parameter, 10<b<23. Preferably, the b increases as R increases. Preferably, the b increases more and more with the increase of R.

Through experiments, it is found that the amplitude of b changes with R, which will lead to more accurate results and greatly improve the accuracy of measurement data.

Preferably, 15.3<b<18.2.

The distance between the orifice flowmeter system and the flow control system 7 is S3>=c*R, where c is a parameter, 4<c<13. Preferably, the c increases as R increases. Preferably, the c increases more and more with the increase of R.

Through experiments, it is found that the amplitude of c changes continuously with R, which will lead to more accurate results and greatly improve the accuracy of measurement data.

As a preference, 7.2<c<9.2.

The distance between the adjacent pitot static pressure pipe system 3, venturi flow meter system 4, orifice plate flow meter system 5, flow control system 7 is the last position of the system on the flow channel and the beginning position of the next system The distance between, preferably, Pitot static pressure pipe system 3, Venturi flowmeter system 4, orifice plate flowmeter system 5, flow control system 7 are fixed on the flow channel through flanges, and the distance between the adjacent systems is Take the distance between the end flange of the adjacent system and the beginning flange of the next system.

Although the present invention has been disclosed above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (4)

1. a kind of gas mobility status measurement experiment device, including gas flow generating device, Pitot static tube system, venturi flow Meter systems, orifice flow meter systems and flow control system and runner；Gas flow generating device generates the gas flowed in runner Stream, the size of the flow control system control air-flow, the Pitot static tube system, venturi flow meter systems, orifice plate Flowmeter system is mounted on runner, for measuring the flow of air-flow in runner, the flow control system, Pitot static tube system System, venturi flow meter systems, orifice flow meter systems carry out data connection with data acquisition controller respectively, and the data are adopted Collection controller is connect with data display equipment, which is characterized in that the Pitot static tube system includes that Pitot tube and Pitot tube move Dynamic device, Pitot tube mobile device can be such that Pitot tube moves freely in surveyed section；The flow control system is installation Baffle and mobile device in airflow channel end control air-flow size by controlling baffle at a distance from channel outlet；

Along the direction of air-flow, gas flow generating device, Pitot static tube system, Venturi meter system are set gradually in runner System, orifice flow meter systems and flow control system；

Runner where Pitot static tube system is square-section, where venturi flow meter systems, orifice flow meter systems Runner is circle；

The square passageway inner section side length of Pitot static tube system is L, and the radius of circular channel is R, then Pitot static tube system Minimum range S1 >=a* ((R/2) between system and venturi flow meter systems²+L²)^(1/2), wherein a is parameter, 22.54 < a < 32.18；

The distance between venturi flow meter systems, orifice flow meter systems S2>=b*R, wherein b is parameter, 10<b<23.

2. gas mobility status measurement experiment device as described in claim 1, which is characterized in that the installation of Pitot tube mobile device On runner wall surface, Pitot tube can move freely under mobile device auxiliary in measurement section, realize that multimetering takes The function of value.

3. gas mobility status measurement experiment device as claimed in claim 1 or 2, which is characterized in that the mobile device Including sliding block, the Pitot tube is arranged in sliding block, and the sliding block includes convex block, and runner tube wall is arranged in the convex block In groove, convex block can move in groove, and moving freely for Pitot tube is realized by the movement of convex block.

4. gas mobility status measurement experiment device as claimed in claim 1 or 2, which is characterized in that the mobile device is adopted Transverse shifting is realized with sliding groove is opened on runner wall surface, wherein applies lubricating oil on contact surface.