Model experiment device for measuring airflow resistance characteristic of cable channel

Abstract

The utility model provides a model experiment device for measuring airflow resistance characteristics of a cable channel. The model experiment device comprises a frequency conversion blower, a rectification section, a first damping section, a reduced-size cable channel experiment section, a second damping section, an axial flow fan, a wind speed measuring device, a signal collector, a controller and an upper computer, the variable-frequency air feeder, the rectification section, the first damping section, the reduced-size cable channel experiment section, the second damping section and the axial flow fan are sequentially assembled and installed according to the flow direction of air flow. The device can simply and accurately complete multiple groups of working condition experiments, and has the advantages of high resistance characteristic test result accuracy, low construction cost and low operation cost. Besides, the reduced-size cable channel experiment section is arranged to be a replaceable part, and the corresponding reduced-size cable channel experiment section can be replaced conveniently, so that the simulation test of actual cable galleries with different spatial structure characteristics and section shapes can be completed, the manufacturing cost of the experiment device is further reduced, the investment cost of the model device is low, and the operation cost is low.

Description

Technical Field

[0001] This utility model belongs to the field of ventilation system testing technology, specifically relating to a model experimental device for measuring the airflow resistance characteristics of cable channels. Background Technology

[0002] With the development of power systems, the construction of cable channels is increasing, such as the power compartments of underground utility tunnels in cities and the underground outgoing line tunnels of pumped storage power stations. Since cables dissipate heat within cable channels, ventilation systems are required to dissipate this heat. Therefore, the study of the ventilation resistance characteristics of cable channels is of great significance for ventilation system design.

[0003] In various pipeline engineering designs, ventilation resistance loss is divided into friction loss and local resistance. Friction loss considers wall roughness, while local resistance considers the shape changes of local obstacles. Unlike general ventilation ducts, cable channels have cable supports on their sidewalls, which affect airflow. However, this effect differs from the mechanism by which wall roughness affects flow. Therefore, traditional formulas for local resistance and friction loss in ventilation ducts cannot be directly applied to the ventilation resistance of cable channels.

[0004] Currently, engineering design commonly uses empirical estimation methods to determine the resistance coefficient, thereby estimating the resistance value of the cable tunnel ventilation system, and selecting the pressure head of the ventilation equipment based on the estimated value. However, the estimation of the ventilation system resistance value is usually conservative, resulting in the selection of an excessively large ventilation system pressure head, leading to excessive energy consumption during ventilation system operation.

[0005] To effectively guide the design of ventilation systems for cable tunnels, a feasible approach is to use model testing devices to test the airflow resistance characteristics of the cable tunnels. However, existing model testing devices generally have fixed structures and are only suitable for testing the ventilation system resistance of cable tunnels with a single shape, which has significant limitations. Utility Model Content

[0006] In view of the shortcomings of the existing technology, this utility model provides a model experimental device for measuring the airflow resistance characteristics of cable channels, which can effectively solve the above problems.

[0007] The technical solution adopted in this utility model is as follows:

[0008] This utility model provides a model experimental device for measuring the airflow resistance characteristics of a cable channel, comprising: a variable frequency blower (1), a rectifier section (2), a first damping section (3), a scaled-down cable channel experimental section (4), a second damping section (5), an axial flow fan (6), a wind speed measuring device (7), a signal acquisition device (8), a controller (9), and a host computer (10).

[0009] According to the airflow direction, the variable frequency blower (1), the rectifier section (2), the first damping section (3), the reduced-size cable channel test section (4), the second damping section (5), and the axial flow fan (6) are assembled and installed in sequence; wherein, the air inlet and air outlet sections of the reduced-size cable channel test section (4) are each provided with multiple measuring holes (4-1); one end of the wind speed measuring device (7) is connected to the measuring hole (4-1), and the other end is connected to the input end of the signal collector (8); the output end of the signal collector (8) is connected to the input end of the host computer (10); the output end of the host computer (10) is connected to the input end of the controller (9); the output end of the controller (9) is connected to the variable frequency blower (1) and the axial flow fan (6) respectively.

[0010] Preferably, the reduced-size cable channel test section (4) adopts a detachable structure.

[0011] Preferably, the cross-sectional shape of the reduced-size cable channel experimental section (4) is rectangular or semi-circular.

[0012] Preferably, the air inlet of the reduced-size cable channel test section (4) is connected to the air outlet of the first damping section (3) through the first diameter changing device (11); the air outlet of the reduced-size cable channel test section (4) is connected to the air inlet of the second damping section (5) through the second diameter changing device (12).

[0013] Preferably, both ends of the first diameter reducing device (11) are respectively assembled and connected to the reduced-size cable channel test section (4) and the first damping section (3) through flanges (13); both ends of the second diameter reducing device (12) are respectively assembled and connected to the reduced-size cable channel test section (4) and the second damping section (5) through flanges (13).

[0014] Preferably, according to the airflow direction, the cross-section of the first diameter changing device (11) gradually expands, and the cross-section of the second diameter changing device (12) gradually shrinks.

[0015] Preferably, the wind speed measuring device (7) is an anemometer and a Pitot tube.

[0016] Preferably, the anemometer is a retractable anemometer; the Pitot tube is a retractable Pitot tube.

[0017] The model experimental device for measuring the airflow resistance characteristics of cable channels provided by this utility model has the following advantages:

[0018] This device can easily and accurately complete multiple sets of working condition experiments, and has the advantages of high accuracy in resistance characteristic test results, low construction cost, and low operating cost. In addition, the scaled-down cable channel test section is designed as a replaceable component, which facilitates the replacement of the corresponding scaled-down cable channel test section, thereby completing the simulation test of actual cable corridors with different spatial structural features and cross-sectional shapes. Therefore, it further reduces the manufacturing cost of the experimental device, resulting in low investment cost and low operating cost for the model device. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of the model experimental device for measuring the airflow resistance characteristics of a cable channel provided by this utility model;

[0020] Figure 2 This is a schematic diagram of the measurement principle of a retractable wind speed measuring device.

[0021] Figure 3 An internal structural diagram of a scaled-down cable channel experimental section provided by this utility model;

[0022] Figure 4 An internal structural diagram of a scaled-down cable channel experimental section provided by this utility model;

[0023] Figure 5 An internal structural diagram of a scaled-down cable channel experimental section provided by this utility model;

[0024] Figure 6 An exploded view of the reducing device and the flanges at both ends provided by this utility model.

[0025] The components include: 1. Variable frequency blower; 2. Rectifier section; 3. First damping section; 4. Test section of reduced-size cable channel; 4-1. Measuring hole; 5. Second damping section; 6. Axial flow fan; 7. Wind speed measuring device; 8. Signal acquisition device; 9. Controller; 10. Host computer; 11. First diameter changing device; 12. Second diameter changing device; 13. Flange; 14. Cable; 15. Outer wall of cable channel. Detailed Implementation

[0026] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit this utility model.

[0027] This invention provides a model experimental device for measuring the airflow resistance characteristics of cable channels, enabling convenient, fast, economical, and accurate measurement of the airflow resistance characteristics of cable channels.

[0028] See Figure 1This utility model provides a model experimental device for measuring the airflow resistance characteristics of cable channels, including: a variable frequency blower 1, a rectifier section 2, a first damping section 3, a scaled-down cable channel experimental section 4, a second damping section 5, an axial flow fan 6, a wind speed measuring device 7, a signal acquisition unit 8, a controller 9, and a host computer 10.

[0029] According to the airflow direction, the variable frequency blower 1, rectifier section 2, first damping section 3, reduced-size cable channel test section 4, second damping section 5, and axial flow fan 6 are assembled and installed in sequence. Among them, the air inlet and outlet sections of the reduced-size cable channel test section 4 are each provided with multiple measuring holes 4-1. The measuring holes 4-1 are used to insert the wind speed measuring device 7, which can be a hot-wire anemometer or a Pitot tube. One end of the wind speed measuring device 7 is connected to the measuring hole 4-1, and the other end is connected to the input end of the signal acquisition unit 8. The output end of the signal acquisition unit 8 is connected to the input end of the host computer 10. The output end of the host computer 10 is connected to the input end of the controller 9. The output end of the controller 9 is connected to the variable frequency blower 1 and the axial flow fan 6 respectively.

[0030] The variable frequency blower 1 delivers air to the experimental device, while the rectifier section 2, the first damping section 3, the second damping section 5, and the axial flow fan 6 can eliminate eddies and achieve uniform airflow in the experimental section 4 of the reduced-size cable channel.

[0031] Specifically, the variable frequency fan 1 is installed at the air outlet of the entire device, and the air volume is controlled by the control system 9 to simulate tunnel ventilation under different requirements. The variable frequency fan 1 can be a centrifugal variable frequency fan.

[0032] The rectifier section 2 is installed between the variable frequency blower 1 and the reduced-size cable channel test section 4 to rectify the air supplied by the variable frequency blower 1 into the system and deliver it smoothly and evenly into the reduced-size cable channel test section 4.

[0033] The wind speed measuring device 7 includes a hot-wire anemometer and a Pitot tube. The hot-wire anemometer is used to measure the cross-sectional wind speed; the Pitot tube measures the pressure difference between the front and rear sections of the channel. The test results are sent to the host computer 10 via the signal acquisition unit 8; the host computer 10 can be a computer. The host computer 10 then controls the controller 9, which in turn controls the variable frequency fan 1 and the axial flow fan 6 to achieve airflow regulation.

[0034] The controller 9 is mainly responsible for the frequency conversion control of the variable frequency blower 1 to obtain the wind speed in the experimental section 4 of the reduced-size cable channel and the frequency control of the axial flow fan 6. During the experiment, the operating frequencies of the variable frequency blower 1 and the axial flow fan 6 should be kept consistent. By using the "push-pull" airflow organization method, the uniformity of the cross-sectional airflow in the experimental section 4 of the reduced-size cable channel is maximized, and the eddy current phenomenon in the experimental section 4 of the reduced-size cable channel is avoided due to poor ventilation.

[0035] Therefore, after the air supplied by the variable frequency blower 1 is processed by the rectifier section 2, it is sent into the reduced-size cable channel test section 4. The signal acquisition device 8 collects the test results of the hot-wire anemometer and Pitot tube on the front and rear sides of the reduced-size cable channel test section 4 and inputs them into the host computer 10. Finally, the resistance characteristics of the reduced-size cable channel test section 4 can be obtained.

[0036] As an optimization, in this invention, the scaled-down cable channel experimental section 4 adopts a detachable structure, that is, it is a replaceable component. The cross-sectional shape of the scaled-down cable channel experimental section 4 is rectangular or semi-circular, etc., which is the same as the cross-sectional shape of the actual cable channel.

[0037] The air inlet of the reduced-size cable channel test section 4 is connected to the air outlet of the first damping section 3 via the first diameter changing device 11; the air outlet of the reduced-size cable channel test section 4 is connected to the air inlet of the second damping section 5 via the second diameter changing device 12. The cross-section of the first diameter changing device 11 gradually increases in the direction of airflow, while the cross-section of the second diameter changing device 12 gradually decreases.

[0038] Specifically, both ends of the first diameter reducing device 11 are respectively assembled and connected to the reduced-size cable channel test section 4 and the first damping section 3 via flanges 13; such as Figure 6 The two ends of the second reducing device 12 are respectively assembled and connected to the reduced-size cable channel test section 4 and the second damping section 5 via flanges 13. The flanges 13 enable the detachable installation of the reduced-size cable channel test section 4. Therefore, the reduced-size cable channel test section 4 can be replaced with [other components] depending on the actual scenario. Figure 3 , Figure 4 , Figure 5 The diagram shows channel models of different shapes, etc.

[0039] As an optimized solution, the wind speed measuring device 7 comprises an anemometer and a Pitot tube, wherein the anemometer is a retractable anemometer, and the Pitot tube is a retractable Pitot tube. For example... Figure 2 As shown, the retractable structure allows for the measurement of data at different locations on the cross-section through the same measuring hole 4-1, thus improving the comprehensiveness of the measurement data.

[0040] This invention provides a model experimental device for measuring the airflow resistance characteristics of cable channels, which has the following features:

[0041] 1) This device establishes a scaled-down cable channel test section based on the Reynolds similarity principle and actual design scheme. The scaled-down ratio is generally 1:10, so that the size of the scaled-down cable channel test section is proportionally reduced to the actual cable channel, while the cross-sectional shape of the scaled-down cable channel test section is the same as that of the actual cable channel, thereby improving the accuracy of the simulation of the airflow resistance characteristics of the cable channel.

[0042] 2) The scaled-down cable tunnel test section is designed as a replaceable component, using a variable diameter device and a flange connection to the ventilation duct damping section. Therefore, based on the actual spatial structure characteristics and cross-sectional shape (rectangular, semi-circular, etc.) of the cable tunnel, the corresponding scaled-down cable tunnel test section can be easily replaced. This allows for simulation testing of actual cable tunnels with different spatial structure characteristics and cross-sectional shapes. Thus, while retaining the rest of the experimental system, only the scaled-down cable tunnel test section needs to be replaced to conduct ventilation resistance tests on cable tunnels with different cross-sectional shapes, reducing the manufacturing cost of the experimental device. The model device has low investment costs and low operating expenses. It also has the advantages of wide applicability and ease of use.

[0043] 3) This device can measure the resistance characteristics of cable channels more accurately: by setting up a retractable anemometer and Pitot tube, more sets of data can be measured on the same section, thereby obtaining a more accurate cross-sectional air volume and improving the accuracy of the cable channel resistance characteristic measurement results.

[0044] 4) This device avoids the impact of turbulent airflow at the outlet of the variable frequency blower on the measurement of experimental data by setting up a rectification section. An axial flow fan is used for exhaust at the end of the air outlet of the experimental section. The operating frequency of the variable frequency blower and the axial flow fan are kept consistent. By using the "push-pull" airflow organization method, the eddy current phenomenon caused by poor exhaust is avoided, and the uniformity of airflow in the cross section of the cable channel experimental section is maximized, so as to obtain more accurate experimental results.

[0045] This invention does not limit the method by which the host computer 10 calculates the airflow resistance characteristics of the cable channel based on the measurement results of the wind speed measuring device 7. Only two embodiments are listed below:

[0046] Example 1: Wind speed measurement:

[0047] 1) Before the experiment, turn on the variable frequency blower 1 and set the frequency to 50Hz.

[0048] 2) The scaled-down cable channel experimental section 4 is a semi-circular cable channel model, as shown in Figure 1, with cables 14 arranged on the upper side of the channel. First, the wind speed at section A near the air inlet of the cable channel model is measured, according to... Figure 2 At the indicated measuring points, the probe of the telescopic hot-wire anemometer, placed in measuring hole 4-1, is positioned at the center of each measuring point to measure the average wind speed at each point on section A. After the hot-wire anemometer readings stabilize, the wind speed is recorded every 10 seconds. The average of six readings (one minute) is taken as the wind speed at that measuring point. The wind speeds at the ten measuring points are designated as v1, v2, ..., v... 10 The average wind speed of the cross section is calculated using the following formula.

[0049]

[0050] Among them, v1, v2, ..., v 10 Let be the wind speed at each measuring point on section A.

[0051] 3) Repeat steps 1) to 2) for 3 experiments, and take the average value of the three experiments as the cross-sectional wind speed.

[0052] 4) Repeat steps 1) to 3) to measure the wind speed at section B near the air outlet side of the cable channel model.

[0053] 5) Adjust the frequency of the variable frequency blower 1 (50HZ, 40HZ, 30HZ) by the controller 9 to change the air outlet velocity v of the variable frequency blower 1. Adjust the frequency of the axial flow fan 6 at the end of the experimental section accordingly to change the exhaust velocity. Perform 3 experiments to obtain the characteristic curve of the air flow velocity.

[0054] Example 2: Measurement of airflow resistance characteristics in cable channels:

[0055] This model uses an indirect measurement method for total pressure. The static pressure of the cross section is measured by a static pressure probe, and the dynamic pressure of the cross section is calculated using wind speed. The two are added together to obtain the total pressure of the cross section.

[0056] 1) Before the experiment, turn on the variable frequency blower 1 and set the frequency to 50Hz.

[0057] 2) such as Figure 1 As shown, the probe of the telescopic hot-wire anemometer located at measuring hole 4-1 is placed at the center of each measuring point to measure the average wind speed at each measuring point on the cross section. After the reading of the hot-wire anemometer stabilizes, the wind speed is recorded, and the average wind speed of the cross section is calculated using formula (1). Repeat this step to obtain the cross-sectional wind speeds at sections A and B before and after the cable channel model.

[0058] 3) Using the cross-sectional wind speed obtained in step 2), substitute it into the following formula:

[0059]

[0060] The dynamic pressure h of the two cross sections is obtained. A h B .

[0061] 4) such as Figure 2 As shown, the arrangement of measuring points in the static pressure measurement experiment is the same as that in the wind speed measurement experiment. The static pressure at the center of each measuring point is measured using a Pitot tube. After the reading of the Pitot tube at measuring orifice 4-1 stabilizes, the static pressure is recorded every 10 seconds. The average of six readings over one minute is taken as the static pressure at that measuring point. The static pressures at the ten measuring points are designated as p1, p2, ..., p... 10 The cross-sectional average wind speed and static pressure are calculated using the following formula.

[0062]

[0063] Among them, p1, p2, ..., p 10 The static pressure is measured at the point on section A of the experimental segment.

[0064] 5) Repeat step 4) to obtain the static pressure of section B.

[0065] 6) Add the dynamic pressure obtained in step 3) to the static pressure obtained in step 4) to obtain the total pressure P at sections A and B. AB1 P AB2 Subtracting the two yields the total pressure difference ΔP between the two sections. AB

[0066] 7) Substitute the above data into the following formula:

[0067]

[0068] Calculate the resistance characteristic λ of the cable channel. e Where: L is the length of the reduced-size cable channel experimental section 4; ρ is the airflow density; and de is the diameter of the reduced-size cable channel experimental section 4.

[0069] 8) By adjusting the fan frequency (50Hz, 40Hz, 30Hz), the frequency of the variable frequency blower 1 is changed, thereby changing the wind speed v. Three experiments are conducted. Through the above steps, the airflow resistance characteristic curves of the cable channel under different wind speeds can be obtained. Using similarity criteria, the airflow resistance characteristics of the actual cable channel can be obtained, that is, the equivalent resistance characteristic λ of the cable channel is determined. e value.

[0070] Therefore, this utility model provides a model experimental device for measuring the airflow resistance characteristics of cable tunnels, including a scaled-down cable tunnel experimental section 4, a variable frequency blower 1, a rectifier section 2, a testing device, and a control system. The scaled-down cable tunnel experimental section 4 includes a cable tunnel model and measuring holes for inserting a hot-wire anemometer or a Pitot tube. The variable frequency blower 1 is installed at the air outlet of the entire device, and the airflow is controlled by the control system to simulate tunnel ventilation under different requirements. The rectifier section 2 is installed between the variable frequency blower 1 and the scaled-down cable tunnel experimental section 4, rectifying the air supplied by the variable frequency blower 1 into the system and delivering it smoothly and evenly into the scaled-down cable tunnel experimental section 4. The measuring device includes a hot-wire anemometer and a Pitot tube. The hot-wire anemometer is used to measure the cross-sectional wind speed; the Pitot tube is used to measure the pressure difference between the front and rear sections of the tunnel. The test results are sent to the host computer 10 via a signal acquisition unit 8. The control system primarily controls the frequency conversion of the variable frequency fan 1 to obtain different wind speeds within the channel, and controls the frequency of the axial flow fan 2. Through a "push-pull" airflow organization method, it maximizes the uniformity of airflow across the cross-section of the experimental section 4 of the reduced-size cable channel. This device can easily and accurately complete multiple sets of operating condition experiments, and has the advantages of high accuracy in resistance characteristic test results, low construction cost, and low operating cost.

[0071] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A model experimental apparatus for measuring the airflow resistance characteristics of cable channels, characterized in that, include: Variable frequency blower (1), rectifier section (2), first damping section (3), reduced-size cable channel test section (4), second damping section (5), axial flow fan (6), wind speed measuring device (7), signal acquisition device (8), controller (9) and host computer (10); According to the airflow direction, the variable frequency blower (1), the rectifier section (2), the first damping section (3), the reduced-size cable channel test section (4), the second damping section (5), and the axial flow fan (6) are assembled and installed in sequence; wherein, the air inlet and air outlet sections of the reduced-size cable channel test section (4) are each provided with multiple measuring holes (4-1); one end of the wind speed measuring device (7) is connected to the measuring hole (4-1), and the other end is connected to the input end of the signal collector (8); the output end of the signal collector (8) is connected to the input end of the host computer (10); the output end of the host computer (10) is connected to the input end of the controller (9); the output end of the controller (9) is connected to the variable frequency blower (1) and the axial flow fan (6) respectively.

2. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 1, characterized in that, The reduced-size cable channel experimental section (4) adopts a detachable structure.

3. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 1, characterized in that, The cross-sectional shape of the reduced-size cable channel experimental section (4) is rectangular or semi-circular.

4. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 1, characterized in that, The air inlet of the reduced-size cable channel test section (4) is connected to the air outlet of the first damping section (3) through the first diameter changing device (11); the air outlet of the reduced-size cable channel test section (4) is connected to the air inlet of the second damping section (5) through the second diameter changing device (12).

5. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 4, characterized in that, Both ends of the first diameter reducing device (11) are respectively assembled and connected to the reduced-size cable channel test section (4) and the first damping section (3) through flanges (13); both ends of the second diameter reducing device (12) are respectively assembled and connected to the reduced-size cable channel test section (4) and the second damping section (5) through flanges (13).

6. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 4, characterized in that, According to the airflow direction, the cross-section of the first diameter changing device (11) gradually expands, while the cross-section of the second diameter changing device (12) gradually shrinks.

7. The model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 1, characterized in that, The wind speed measuring device (7) is an anemometer and a Pitot tube.

8. A model experimental apparatus for measuring the airflow resistance characteristics of a cable channel according to claim 7, characterized in that, The anemometer is a retractable anemometer; the Pitot tube is a retractable Pitot tube.

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