CN112879069B - Model test device for researching internal airflow characteristics of high and large vertical shaft - Google Patents
Model test device for researching internal airflow characteristics of high and large vertical shaft Download PDFInfo
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- CN112879069B CN112879069B CN202110092925.3A CN202110092925A CN112879069B CN 112879069 B CN112879069 B CN 112879069B CN 202110092925 A CN202110092925 A CN 202110092925A CN 112879069 B CN112879069 B CN 112879069B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F1/00—Ventilation of mines or tunnels; Distribution of ventilating currents
- E21F1/02—Test models
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F1/00—Ventilation of mines or tunnels; Distribution of ventilating currents
- E21F1/006—Ventilation at the working face of galleries or tunnels
Abstract
The invention discloses a model test device for researching the characteristics of airflow in a tall and big vertical shaft. The centrifugal frequency conversion blower and the bidirectional axial flow type frequency conversion fan are respectively positioned at two sides of the vertical shaft model test section, and the air quantity can be adjusted by connecting a frequency converter; the upper part of the vertical shaft model test section along the longitudinal direction is provided with grid clamping grooves at equal intervals for placing resistance grids, and the local resistance of the resistance grids is used for equivalently simulating the on-way resistance of the long and large vertical shaft direct-current section; and measuring holes are respectively formed in two sides of the series of grid clamping grooves and used for measuring wind speed and static pressure. By adjusting the wind speed and the wind direction of the bidirectional axial flow type variable frequency fan and setting different numbers of resistance grids, the internal airflow characteristics of the ventilation system can be simulated when the (forward or reverse) chimney effect is considered in a high and large vertical shaft, and the requirement of carrying out a physical model test under the limited indoor conditions is met.
Description
Technical Field
The invention relates to a test device, in particular to a model test device for researching the internal airflow characteristics of a high and large vertical shaft.
Background
Tall shafts are widely used in ventilation systems in above-ground and underground spaces. In a deeply buried underground space such as an underground pumped storage power station, an air exhaust shaft is required to be arranged to exhaust heat emitted by equipment and personnel in an underground plant; mountain highway tunnel need set up the vertical shaft of airing exhaust and carry out tunnel ventilation in order to discharge dirty air. Due to the huge energy storage effect of surrounding rock masses, the temperature of the wall surface of the tall and big vertical shaft can be basically regarded as constant, and a heat exchange process exists between the wall surface along the way and internal airflow. For the exhaust of the deep buried underground space, the temperature of the wall surface of the vertical shaft is lower than the temperature of the exhaust airflow at the inlet of the vertical shaft due to the need of exhausting waste heat, so that the airflow ascending process is cooled along the way, the temperature is reduced, and a reverse chimney effect is generated. For the mountainous tunnel shaft, the temperature of the wall surface of the shaft is higher than the temperature of air discharged from the inlet of the shaft in winter, and the air flow is heated in the rising process, so that a positive chimney effect is generated. In the positive chimney effect, airflow is heated by the wall surface, the density is reduced, the buoyancy lift force is generated, the outflow of the airflow is promoted, and the effect of offsetting the resistance to a certain degree is achieved. The airflow is cooled along the flowing way in the reverse chimney effect, the density is increased, and the resistance of the airflow flowing out of the vertical shaft is increased. Different from a long and large horizontal tunnel, the chimney effect is strong due to the large height difference of the inlet and the outlet of the high and large vertical shaft. Although the tall and big vertical shaft is provided with a mechanical ventilation system for exhausting air, the influence of the forward or reverse chimney effect must be considered in the ventilation system design and the internal airflow characteristic analysis process, and the fan model selection is further adjusted.
When the scale model test is carried out on the airflow characteristics of the high and large ventilation vertical shaft, such as the distribution of different section pressures and speeds, the model height is too large even if the scale model is strictly reduced according to equal proportion, and the difficulty in measuring the airflow characteristic parameters along the height is large. Therefore, the ventilation model experiment by selecting the equivalent simulation method is a feasible mode.
The research idea comprises the following steps: 1) because the tall and big air exhaust vertical shaft is basically a straight pipe section along the way, the air flow and the wall surface form along-the-way resistance as the main part, a resistance grid is arranged at the proper part of the model according to the friction resistance equivalent theory, and the grid obtains the local resistance to equivalently replace a certain direct current length; 2) the vertical placing device is high in testing difficulty, and the horizontal placing device is adopted to equivalently simulate the airflow parameter change in the vertical direction. Aiming at the problem that the simulation of the chimney effect cannot be realized when the device is placed transversely, a bidirectional axial flow type variable frequency fan is arranged on the side of an air outlet of a vertical shaft model, and the influence caused by the chimney effect is simulated by adjusting the air speed and the air direction; 3) in the measurement of the airflow characteristics of the ventilation shaft, the main measurement parameter is the pressure change at different heights, and the main reason of the on-way pressure change is the on-way resistance of the airflow and the chimney effect in the tall shaft to form the pressure change. Through reasonable pressure distribution simulation, the distribution rule of the airflow parameters in the vertical direction of the vertical shaft device can be equivalently analyzed through the measurement result of the airflow parameter distribution in the horizontally placed device, which is the focus of the research idea of the invention.
With regard to resistance characteristic tests and experimental studies of air ducts, a large amount of work has been carried out by domestic scholars. The patent of resistance grilles (CN 204359506) in a tunnel ventilation physical model experiment, chemering et al, proposes to install resistance grilles in appropriate parts of a model tunnel to obtain equivalent resistance to obtain corresponding lengths. The equivalent coefficient of friction resistance of the utility tunnel ventilation system of the liuchengdong et al patent (CN 107291984a) proposes a method for determining the equivalent coefficient of friction resistance of a long and narrow spatial utility tunnel. In an intensive mine ventilation resistance calculation method (CN 107083983A), Weilianjiang and the like, two ends of a long pipeline are respectively connected with two measuring ports of a differential pressure sensor, so that the ventilation resistance of a roadway can be obtained. The method (CN108386647A) of adjusting the resistance of the ventilating dust-removing pipeline is proposed by the balance of money and the like, and the resistance balance is adjusted by designing an adjustable orifice plate type resistance balancer. And performing dimensionless simulation on the orifice plate plug-in units with different aperture ratios in the pipeline to obtain resistance values under the aperture ratios, and further calculating local resistance coefficients. But no relevant report is found in the experimental study of the airflow characteristic simulation of the tall and big vertical shaft.
The proportional model experimental device provided by the invention has the characteristics that: 1) the vertical ventilation shaft model is horizontally placed, so that the test measurement difficulty is reduced; 2) arranging a bidirectional axial flow type variable frequency fan at the air outlet side of the vertical shaft model test section to equivalently simulate two chimney effects in a vertical shaft by adjusting the air speed and the air direction; 3) by adjusting the arrangement mode of the resistance grids, different heights of the vertical shaft model are simulated equivalently, so that the speed and static pressure distribution of the sections of the vertical shaft model with different heights can be measured.
Disclosure of Invention
The invention aims to provide a proportioning device for a deep-buried vertical shaft ventilation model test, which has a simple structure and can meet the test requirements, aiming at the defects of the air flow characteristic technology of the existing vertical shaft with high and large air exhaust in an underground space.
In order to achieve the purpose, the invention adopts the following technical scheme: the device comprises a centrifugal frequency conversion blower, a bidirectional axial flow type frequency conversion fan, a frequency converter and a vertical shaft model test section. The centrifugal frequency conversion blower is arranged on the side of an air supply outlet of a test section of the vertical shaft model, and the mechanical air exhaust effect in the vertical shaft model under different conditions can be simulated by adjusting the air supply quantity controlled by the connected frequency converter; the bidirectional axial flow type variable frequency fan is positioned at the air outlet side of the vertical shaft model test section, can simulate the effect of strengthening the air exhaust of the vertical shaft when the wind direction is towards the outdoor air exhaust, can simulate the effect of hindering the air exhaust of the vertical shaft under the effect of a reverse chimney when the wind direction is opposite, and can control the air quantity by adjusting the connected frequency converter, thereby meeting the requirements of different chimney effects; a pressure stabilizing box and a honeycomb rectifier are connected to the side of the air supply outlet of the vertical shaft model test section; the vertical shaft model test section is respectively provided with a pressure measuring hole, a wind speed measuring hole and grid clamping grooves at equal intervals along the longitudinal direction;
the distance between every two adjacent grating clamping grooves is 1.5 times of the diameter De of the vertical shaft model test section; the resistance grids are of inclined net structures, the inclination angles of the net structures are 45 degrees, and the diameters of iron wires in the resistance grids are smaller than or equal to 2 mm;
furthermore, a semicircular annular grating blocking cover is welded on the outer edge of the upper half part of the resistance grating to play a role in fixing; when the resistance grating is not placed in the grating clamping groove, the annular cover is used for shielding;
furthermore, the width of the opening of the grating clamping groove is 1.5 times of the thickness of the resistance grating; the width of the grating blocking cover is 2 times of the width of the opening of the grating clamping groove; the width of the annular cover is 3 times of the width of the opening of the grating clamping groove;
pressure measuring holes and wind speed measuring holes are formed in the two sides of the air inlet and the air outlet of the vertical shaft model test section, and a pitot tube and a wind speed measuring instrument are used for measuring pressure and wind speed respectively; the distance between the measuring holes on the air inlet side and the air inlet is 7.5 times of De, the distance between the measuring holes on the air outlet side and the air outlet side is 5 times of De, the distance between the two measuring holes on the same side is 0.5 times of De, and the distance between the measuring holes and the adjacent grating clamping groove is 5 times of De;
compared with the prior art, the invention has the following technical advantages: by adjusting the air quantity and changing the wind direction of the bidirectional axial flow type variable frequency fan, the enhancing effect on the ventilation of the vertical shaft in the case of a forward chimney effect and the blocking effect on the ventilation of the vertical shaft in the case of a reverse chimney effect under different conditions can be simulated approximately; different heights of the vertical shaft model can be equivalently simulated by adjusting the installation number and the installation mode of the resistance grids, so that the wind speed and the pressure distribution at any height position of the vertical shaft model can be measured. The device has simple structure and convenient adjustment, can simulate the ventilation phenomenon when the chimney effect is considered in a high and deep buried vertical shaft, and meets the requirement of carrying out a physical model test under the condition of limited indoor conditions.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of a resistance grid according to the present invention;
FIG. 3 is a schematic view showing the connection relationship between the resistance grating, the annular cover and the test section of the shaft model according to the present invention;
FIG. 4 is a schematic view of a measuring well according to the present invention.
Wherein: 1 is a centrifugal frequency conversion blower; 2 is a first soft connection; 3 is a voltage stabilizing box; 4 is a first frequency converter; 5 is a honeycomb rectifier; 6 is a vertical shaft model test section; 7 is a pressure measuring hole; 8 is a first wind speed measuring hole; 9 is a wind speed measuring instrument; 10 is a grating clamping groove; 11 is a resistance grating; 12 is a grating cover; 13 is an annular cover; 14 is a pressure measuring hole; 15 is a second wind speed measuring hole; 16 is a second flexible connection; 17 is a bidirectional axial flow type variable frequency fan; and 18 is a second frequency converter.
Detailed Description
The present invention is described in further detail below with reference to the attached drawings.
Referring to the attached drawings 1-4, the invention comprises a centrifugal frequency conversion blower 1, a bidirectional axial flow type frequency conversion fan 15, frequency converters 4 and 18 and a shaft model test section 6. The centrifugal frequency conversion blower 1 is arranged at the side of an air supply outlet at the 6-section of a vertical shaft model test, and the mechanical air exhaust effect in the vertical shaft model under different conditions can be simulated by adjusting the air supply quantity controlled by the connected first frequency converter 4; the bidirectional axial flow type variable frequency fan 17 is positioned at the side of an exhaust port of the vertical shaft model test section 6, can simulate the strengthening effect of the vertical shaft exhaust air when the wind direction is towards the outdoor exhaust air, can simulate the blocking effect of the vertical shaft exhaust air under the reverse chimney effect when the wind direction is opposite, and can control the air quantity by adjusting the connected frequency converter 16, thereby meeting the requirements of different chimney effects; a pressure stabilizing box 3 and a honeycomb rectifier 5 are connected to the side of an air supply outlet of the vertical shaft model test section 6; and the vertical shaft model test section 6 is respectively provided with a pressure measuring hole 7, a first wind speed measuring hole 8 and grid clamping grooves 10 at equal intervals along the longitudinal direction. The grating clamping grooves 10 are used for placing resistance gratings 11, and the distance between every two adjacent grating clamping grooves 10 is 1.5 times of the diameter De of the vertical shaft model test section 6; resistance grid 11 is slope network structure, and network structure inclination is 45, and the iron wire diameter less than or equal to 2mm in each resistance grid 11. A semicircular annular grating baffle cover 12 is welded on the outer edge of the upper half part of the resistance grating 11 to play a role in fixing; when the resistance grating 11 is not placed in the grating clamping groove 10, the annular cover 13 is used for shielding. The opening width of the grating clamping groove 10 is 1.5 times of the thickness of the resistance grating 11; the width of the grating blocking cover 12 is 2 times of the opening width of the grating clamping groove 10; the width of the annular cover 13 is 3 times of the opening width of the grating clamping groove 10. Pressure measuring holes 7 and a first wind speed measuring hole 8 are formed in the two sides of an air inlet and an air outlet of the vertical shaft model test section 6, and a pitot tube and a wind speed measuring instrument 9 are used for measuring pressure and wind speed respectively; the distance between the measuring holes at the air inlet side and the air inlet is 7.5 times of De, the distance between the measuring holes at the air outlet side and the air outlet is 5 times of De, the distance between the two measuring holes at the same side is 0.5 times of De, and the distance between the measuring holes and the adjacent grid clamping groove 10 is 5 times of De;
example of the implementation
The first embodiment is as follows:
the forward chimney effect caused by the temperature rise of the exhausted air along the way in the air exhaust vertical shaft of the mountainous area tunnel in winter is simulated, and the wind speed and pressure distribution at each height inside the air exhaust vertical shaft under the condition of generating the reinforcing effect on mechanical air exhaust is researched. According to attached figures 1-4, firstly, a centrifugal frequency conversion blower 1 is connected with a first frequency converter 4, and a blower outlet is connected with a vertical shaft model test section 6 through a first flexible connection 2, a voltage stabilizing box 3 and a honeycomb rectifier 5; a bidirectional axial flow type variable frequency fan 17 is connected with a second frequency converter 18, and an induced draft port of the fan is connected with an air outlet section of the vertical shaft model test section 6 through a second flexible connection 16; starting a centrifugal frequency conversion blower 1, and enabling the air supply speed of an air supply outlet of a vertical shaft model test section 6 to be the mechanical exhaust air speed v required by a vertical shaft model by adjusting a first frequency converter 4, so as to simulate the mechanical exhaust of the vertical shaft;
according to the air temperature T at the air exhaust inlet of the air exhaust shaft of the prototype highway tunnel0And density ρ0Calculating the air temperature T at the outlet of the vertical shaft according to the total height H of the vertical shaft model and the wall temperature of the vertical shaft and the heat convection theorysThe hot pressing delta P generated in the shaft due to the positive chimney effect can be obtained by the following formula (1),
substituting the hot pressure delta P into an empirical formula (2) to obtain the air flow velocity v' driven by the positive chimney effect in the vertical shaft, wherein CDThe flow coefficient is generally 0.6;
at the moment, the bidirectional axial flow type variable frequency fan 17 is started, the wind direction is set to discharge air from the vertical shaft model, namely, the air exhaust in the vertical shaft model is enhanced, and the wind speed of the fan is enabled to be v' by adjusting the second frequency converter 18, so that the forward chimney effect driven by hot pressing in the air exhaust vertical shaft of the highway tunnel in winter is equivalently simulated.
After all fans are started for ventilation, when the wind speed and the pressure distribution at the H' section with any height in the vertical shaft model need to be measured, the equivalent friction resistance theory is adopted
Calculation formula of equivalent resistance coefficient of resistance grating 11 required by obtaining equivalent substituted H' height
Substituting the equivalent diameter De of 6 in the test section of the vertical shaft model and the on-way resistance coefficient lambda to obtain the required resistance coefficient value of the grating, and adjusting the number and the relative position of the resistance gratings 11 by pressureThe measuring holes 7 and 14 and the first wind speed measuring hole 8 and the second wind speed measuring hole 15 measure the corresponding pressure P1、P2And wind speed v1、v2And substituting the measured value into the calculation formula
The calculated value xi 'is equal to the value of the grid resistance coefficient xi required by the equivalent height of H', and at the moment, the wind speed v2And pressure P2The average wind speed and pressure of the section at the height of H' are obtained; when the speed and pressure distribution at other heights are required to be measured, the parameter distribution at the height can be obtained by repeating the steps, so that the requirement of measuring the wind speed and pressure distribution at any height of the vertical shaft by using a model test device under the condition of considering the enhancement effect of the positive chimney effect on the exhaust air is met.
The second embodiment:
the reverse chimney effect caused by the temperature drop of the discharged air along the way in the deep-buried underground pumped storage power station exhaust shaft is simulated, and the wind speed and pressure distribution at each height in the exhaust shaft under the condition of generating the blocking effect on mechanical exhaust are researched. In the same step as the first embodiment, the air supply speed of the centrifugal frequency conversion blower is adjusted to the mechanical air exhaust speed v required by the test, and the mechanical air exhaust effect is simulated.
According to the air temperature and the density T at the air exhaust inlet of the air exhaust shaft (namely the air exhaust outlet of the underground powerhouse)0And ρ0Shaft outlet air temperature TsAnd the total height H of the shaft model, and obtaining the hot pressing delta P 'generated in the shaft due to the reverse chimney effect from the formula (3)'
Substituting the hot pressing delta P 'into an empirical formula (4) to obtain the air flow velocity v' driven by the reverse chimney effect in the vertical shaft:
starting a bidirectional axial flow type variable frequency fan 17, setting the wind direction to be that air is sent into the vertical shaft model from the outside, namely, the air exhaust in the vertical shaft model is blocked, and adjusting a second frequency converter 18 to enable the wind speed of the fan to be v ", so that the reverse chimney effect driven by hot pressing in the air exhaust vertical shaft of the underground pumped storage power station is equivalently simulated;
according to the first phase synchronization step of the embodiment, the wind speed distribution and the pressure distribution of the cross section at different heights in the vertical shaft model can be measured, so that the requirement of measuring the wind speed and the pressure distribution at any height of the vertical shaft by using a model test device under the condition of considering the blocking effect of the reverse chimney effect on the exhaust air is met.
Claims (4)
1. A model test device for researching the air flow characteristics in a tall and big vertical shaft is characterized by comprising a centrifugal frequency conversion blower (1), a bidirectional axial flow type frequency conversion fan (17), a first frequency converter (4), a second frequency converter (18) and a vertical shaft model test section (6); the centrifugal frequency conversion air feeder (1) is arranged on the air feeding port side of the vertical shaft model test section (6), and the air feeding amount is controlled by adjusting the connected first frequency converter (4) to simulate the mechanical air discharging effect in the vertical shaft model under different conditions;
the bidirectional axial flow type variable frequency fan (17) is positioned on the side of an exhaust port of the vertical shaft model test section (6), and the air quantity is controlled by adjusting the second frequency converter (18), so that the requirements of simulating the effects generated by the forward and reverse chimney effects under different conditions are met.
2. The model test device for studying the characteristics of the air flow in the tall and big shaft according to claim 1, wherein the model test device simulates the effect of enhancing the shaft exhaust air when the wind direction is to exhaust air to the outside by simulating the effect of a forward chimney, and simulates the effect of blocking the shaft exhaust air by the effect of a reverse chimney when the wind direction is reversed.
3. The model test device for researching the air flow characteristics in the interior of the tall and big shaft according to claim 1 or 2, characterized in that the shaft model test section (6) is respectively provided with a pressure measuring hole (7), a first wind speed measuring hole (8) and grid clamping grooves (10) at equal intervals along the longitudinal direction; the grid clamping grooves (10) are used for placing the resistance grids (11), and the distance between every two adjacent grid clamping grooves (10) is 1.5 times of the diameter De of the vertical shaft model test section (6).
4. A model test device for studying the air flow characteristics in the interior of a tall and big shaft according to claim 3, characterized in that a semicircular annular grid baffle cover (12) is welded on the outer edge of the upper half part of the resistance grid (11) for fixing; when the resistance grating (11) is not placed in the grating clamping groove (10), the annular cover (13) is used for shielding; the opening width of the grating clamping groove (10) is 1.5 times of the thickness of the resistance grating (11); the width of the grating blocking cover (12) is 2 times of the opening width of the grating clamping groove (10); the width of the annular cover (13) is 3 times of the opening width of the grating clamping groove (10).
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| CN113916487A (en) * | 2021-10-18 | 2022-01-11 | 水利部交通运输部国家能源局南京水利科学研究院 | Large wind flow generation physical model wind field simulation system |
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| CA2599471A1 (en) * | 2007-08-31 | 2009-02-28 | Alexandre Cervinka | Underground communication network system for personal tracking and hvac control |
| CN102735415B (en) * | 2012-06-08 | 2015-04-08 | 中国科学技术大学 | Underground highway tunnel fire disaster experiment simulating device adopting vertical shaft to carry out natural smoke extraction |
| CN104564120B (en) * | 2014-11-11 | 2017-02-08 | 中国矿业大学 | Operation state control decision making method of mine ventilation system |
| CN204359506U (en) * | 2014-12-23 | 2015-05-27 | 长安大学 | Resistance grid in a kind of tunnel ventilation physical experiments |
| CN209818098U (en) * | 2019-05-08 | 2019-12-20 | 上海进贤机电科技有限公司 | Natural ventilation system for long and large tunnel shaft |
| CN111985168A (en) * | 2020-08-24 | 2020-11-24 | 河海大学 | Method for researching air exhaust effect of underground workshop air exhaust system of pumped storage power station |
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