CN113901635A - Method for calculating circulation airflow circulation path in straight-flow vertical shaft structure - Google Patents

Method for calculating circulation airflow circulation path in straight-flow vertical shaft structure Download PDF

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CN113901635A
CN113901635A CN202110963114.6A CN202110963114A CN113901635A CN 113901635 A CN113901635 A CN 113901635A CN 202110963114 A CN202110963114 A CN 202110963114A CN 113901635 A CN113901635 A CN 113901635A
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air
air pressure
gas
flow
pipe
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魏佳芳
芦三强
赵文举
龙丽丽
马亮军
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Lanzhou University of Technology
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Abstract

The invention provides a method for calculating a circulating airflow circulation path in a straight-flow vertical shaft structure, wherein a vertical partition plate is arranged at the radial position of a vertical shaft with a sealed top end, one end of the vertical partition plate is connected with the top end of the vertical shaft, so that the vertical shaft is divided into a wet pipe section and an air pipe section, the wet pipe section is connected with a water inlet pipe, and the air pipe section is connected with an air pipe; and respectively calculating the air pressure distribution of each section in the wet pipe and the air pressure distribution in the air pipe under a certain amount of water, and obtaining an air pressure intersection point of the wet pipe section and the air pipe section, namely an air pressure critical value, wherein the position of the air pressure critical value is a critical position, and when one end of the partition plate is placed at the critical position or any position between the critical position and the top end of the vertical shaft, the air flow in the vertical shaft can form internal circulation air flow. The method of the invention can obtain the specific placement position of the clapboard when forming the internal circulation airflow, thereby effectively preventing the downstream of the sewage pipeline from being pressurized and providing theoretical guidance for the structure optimization and design of the vertical shaft.

Description

Method for calculating circulation airflow circulation path in straight-flow vertical shaft structure
Technical Field
The invention relates to the technical field of municipal engineering sewage pipes, in particular to a method for calculating a circulating airflow circulation path in a straight-flow vertical shaft structure.
Background
The vertical shaft is one of the most important drop structures in the urban drainage system and mainly plays a role in intensively guiding sewage in a plurality of drainage pipelines close to the ground surface to an underground drainage main canal buried deeper through the vertical shaft. A series of changes can occur in the process that the water flow falls freely from the vertical shaft, the main change is that the initially complete continuous flaky water flow gradually collides, is crushed and is decomposed after falling for a certain height, and most of the water flow is in a water drop shape when the water flow approaches the bottom of the vertical shaft. In this case, the phenomenon of shaft suction is often accompanied, resulting in an excessive pressure gradient in the shaft, and odor generated in the sewage pipes escapes outside the pipes at the pressure, causing serious odor and environmental problems.
Research has shown that the main reason for the air suction of the vertical shaft is that the water flow is broken and decomposed into a large number of small water drops in the falling process, when the flaky complete water flow is changed into water drops, although the volume of the water flow is not changed, the surface area of the water flow is much larger than that of the original water flow, the contact area between the water flow in the water drop state and the air in the vertical shaft is obviously much larger than that of the original water flow, and therefore, the more air can be dragged downwards; secondly, the size of the shaft is also the main reason for influencing the air suction of the shaft, and the larger the diameter of the shaft is, the more the air suction is; the higher the shaft, the more complete the break up of the water stream into droplets and the more air is sucked in.
Chinese patent publication No. CN108104242A discloses a straight-flow drop structure for reducing the amount of inhaled gas, which comprises a water inlet pipe, an air inlet, a partition plate, an air pipe, a water pipe and a flow outlet pipe, wherein the partition plate is arranged in the middle of the shaft, an upper orifice is reserved at a distance from the top of the drop structure, and a lower orifice is reserved at a distance from the bottom of the drop structure, so as to form gas circulation inside the drop structure. Although the above-described shaft structure can reduce the shaft suction to some extent, the structure does not have a specific algorithm for guiding the opening at a specific position, so that the efficiency is greatly reduced, and the effect is not ideal.
In view of this, the present invention provides a calculation method capable of guiding the design and improvement of installing a structure similar to a circulating airflow in a shaft.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for calculating the circulating airflow flow path in a straight-flow type vertical shaft structure, which can obtain the specific placement position of a partition plate when forming the internal circulating airflow, effectively prevent the downstream of a sewage pipeline from being pressurized and provide theoretical guidance for the structure optimization and design of a vertical shaft.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for calculating a circulating airflow path in a straight-through shaft structure,
first, the following model was built: arranging a vertical partition plate at the radial position of a vertical shaft with a sealed top end, wherein one end of the vertical partition plate is connected with the top end of the vertical shaft, so that the vertical shaft is divided into a wet pipe section and an air pipe section, the wet pipe section is connected with a water inlet pipe, the air pipe section is connected with a vent pipe, and the wet pipe section below a nappe is sequentially divided into a nappe blocking section, a constant section and a linear lengthening section by taking the nappe as a base point;
and respectively calculating the air pressure distribution of each section in the wet pipe and the air pressure distribution in the air pipe under a certain amount of water, and obtaining an air pressure intersection point of the wet pipe section and the air pipe section, namely an air pressure critical value, wherein the position of the air pressure critical value is a critical position, and when one end of the partition plate is placed at the critical position or any position between the critical position and the top end of the vertical shaft, the air flow in the vertical shaft can form internal circulation air flow.
Preferably, according to the established model, the specific calculation steps are as follows:
s1, calculating the air pressure distribution in the wet pipe
(1) Air pressure at the inlet pipe
Figure BDA0003222973430000021
Wherein, PaDenotes atmospheric pressure, pa; p0Indicates the air pressure above the nappe, pa; kILoss factor of air inflow at the air inlet; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
Figure BDA0003222973430000025
The average flow velocity of the gas in the gas inlet pipe is m/s;
(2) air pressure (P) of nappe blocking section0～P1)
Figure BDA0003222973430000022
In the formula:
Figure BDA0003222973430000023
representing dimensionless incoming water flow, QwM is the amount of the inflow3/s，DsDiameter of the shaft wet pipe section, m; p1Represents the air pressure under the water tongue, pa; vaRepresents the average flow velocity of the gas in the wet tube, m/s; a and b are constants related to the vertical shaft structure;
(3) constant section air pressure (P)1～P3)
P1＝P3 (4)
(4) Linear growth section pressure (P)3～P8)
The gradient of the air pressure change in the linear growth section is as follows:
Figure BDA0003222973430000024
in the formula: cd0.4 represents a drag system when a water droplet fallsCounting; d-2 represents the diameter of the water drop, mm; v ═ 6 denotes the average speed at which the water droplets fall, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；VaRepresents the average flow velocity of the gas in the wet tube, m/s,
Figure BDA0003222973430000031
Figure BDA0003222973430000032
is the average flow velocity of the gas in the inlet pipe, m/s, DsDiameter of the shaft wet pipe section, m; dIDenotes the diameter of the inlet pipe, m;
s2, calculating the air pressure distribution in the trachea
(1) Determining average gas velocity in trachea
Figure BDA0003222973430000033
Figure BDA0003222973430000034
In the formula:
Figure BDA0003222973430000035
average velocity of gas in trachea, m3/s；DcRepresents the equivalent diameter of the trachea, m; dIDenotes the diameter of the inlet pipe, m;
Figure BDA0003222973430000036
the average flow velocity of the gas in the gas inlet pipe is m/s;
(2) determining the air pressure of a reference point for calculating the air pressure in the trachea
Figure BDA0003222973430000037
In the formula: p'downThe air pressure value, pa, of the air pipe side at the bottom of the partition board is shown; pdownThe air pressure value pa at the wet pipe at the bottom of the partition is shown; k is a radical ofbIndicating the passage of air flowLoss factor at the bottom of the vertical partition; vaRepresents the average flow velocity of the gas in the wet tube, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
(3) Gradient expression of air pressure in trachea
Figure BDA0003222973430000038
In the formula: delta PcRepresents the air pressure difference value between two points in the trachea, pa; dcRepresents the equivalent diameter of the trachea, m; f represents the friction coefficient of the tracheal wall; l distance between any two points in the trachea, m; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
Figure BDA0003222973430000039
Average velocity of gas in trachea, m3/s；
S3, determining a critical value of air pressure
According to the air pressure distribution of the wet pipe section obtained in the step S1 and the air pressure distribution of the air pipe section obtained in the step S2, the equal air pressure value between the wet pipe section and the air pipe section is the air pressure critical value;
s4, determining a circulation path capable of forming an internal circulation airflow
Determining the position of the air pressure critical value in the shaft corresponding to the air pressure critical value determined in the step S3, namely, the position is a critical position, and when one end of the partition plate is placed at the critical position or placed at any position between the critical position and the top end of the shaft, the air flow in the shaft can form an internal circulation air flow;
preferably, the circulation airflow circulation path in the straight-flow shaft structure has an optimal circulation path: among the paths through which the internal circulation gas flow can be formed, when the partition plate is placed at different positions, the path with the least influence on the shaft suction and the upstream and downstream pressure difference during the gas flow is the optimal flow path.
Preferably, by calculating the amount of intake air in the intake pipe
Figure BDA0003222973430000041
And the pressure difference delta P between the upstream and the downstream of the vertical shaft, and determining the influence of gas circulation on the air suction of the vertical shaft and the pressure difference between the upstream and the downstream.
Preferably, an intake air amount in the intake pipe
Figure BDA0003222973430000042
And the shaft upstream and downstream differential pressure Δ P are calculated as follows:
Figure BDA0003222973430000043
in the formula: a. theIDenotes the cross-sectional area of the intake pipe, m2；
Figure BDA0003222973430000044
The average flow velocity of the gas in the gas inlet pipe is m/s;
ΔP＝P8-P0 (10)
in the formula: Δ P represents the pressure difference upstream and downstream in the shaft; p0Indicates the air pressure above the nappe, pa; p8The gas pressure at the flow tube, pa, is shown.
Preferably, when one end of the baffle plate is positioned below the gas inlet pipe and the circulating gas is caused to circulate from a position on the baffle plate parallel to the gas inlet pipe, the resulting flow path is the optimum flow path.
The working principle is as follows: the vertical shaft structure is divided into a wet pipe section and a gas pipe section by a partition plate, the wet pipe is used for passing water and gas, the gas pipe is only used for passing gas, in order to find the optimal position of circulating gas flow flowing from the partition plate, the gas pressure distribution in the wet pipe section and the gas pipe section is respectively calculated, the gas pressure distribution in the wet pipe section and the gas pipe section has an intersection point, the gas pressure corresponding to the intersection point is critical gas pressure, and according to the gas pressure change rule in the gas pipe and the wet pipe: above the critical air pressure, the air pressure in the air duct is greater than the air pressure in the wet tube, and just below the critical air pressure, the opposite is true, so that the circulating air flow can flow from the air duct to the wet tube at any point above this intersection.
Meanwhile, in order to minimize the suction capacity of the vertical shaft, when the circulating airflow passes through an opening on the partition plate at a position parallel to the air inlet pipe (namely one end of the partition plate is positioned below the air inlet pipe), the influence on the suction capacity of the vertical shaft and the pressure difference between the upstream and the downstream is minimized, and the path of the circulating airflow from the position is the optimal path.
The invention has the beneficial effects that:
the invention obtains the equal air pressure in the wet pipe section and the air pipe section, namely the critical value of the air pressure, by accurately calculating the air pressure distribution in the wet pipe section and the air pipe section, and then obtains the path capable of forming the circulation of the internal circulation gas according to the circulation path of the internal circulation gas, and obtains the position of the clapboard which has the minimum influence on the air suction and the upstream and downstream pressure difference of the vertical shaft during the gas circulation, thereby obtaining the optimal circulation path, the circulation gas flow can furthest reduce the air suction of the vertical shaft and the upstream and downstream pressure difference of the vertical shaft under the path, the downstream of the sewage discharge pipeline can be effectively prevented from being pressurized, the problem of escaping the bad smell gas in the sewage discharge pipeline is better solved, therefore, when the optimization design of the vertical shaft structure is carried out, the position of the clapboard can be directly obtained according to theoretical calculation, the optimal air suction reducing effect can be obtained, thereby better guiding the practical application, improving the construction efficiency and the use effect, and the construction and use cost is reduced.
Drawings
Fig. 1 is a schematic diagram of the straight-flow shaft structure model of the present invention.
FIG. 2 is a graph showing the distribution of air pressure in the wet tube and the air tube in the example; the solid line in the figure represents the air pressure distribution in the wet tube and the dotted line represents the air pressure distribution in the trachea.
FIG. 3 is a comparison of the air intake of the circulating air flow under the optimal flow path and other paths in the embodiment.
Fig. 4 is a comparison of the air pressure Δ P of the circulating air flow at the difference between the pressure upstream and downstream of the shaft in the optimal flow path and other paths in the embodiment of the present invention;
FIG. 5 is a schematic diagram showing the position of the partition plate in the optimum circulation path structure of the circulating air flow according to the embodiment.
In the figure: 10. the air pipe 20, the water inlet pipe 30, the vertical partition plate 40, the wet pipe 50, the air pipe 60, the outlet pipe 70 and the optimal circulation path are opened at the upper part of the partition plate.
Detailed Description
In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.
In this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways.
The circulating airflow, namely the air in the wet pipe bypasses the lower part of the partition plate and enters the air pipe and then enters the wet pipe from the opening on the partition plate, if the partition plate is opposite to the opening formed at the top of the vertical shaft, the airflow cannot flow into the wet pipe from the air pipe, namely the airflow cannot form internal circulating airflow, and therefore the downstream of the sewage discharge pipeline cannot be effectively prevented from being pressurized.
In view of this, the present invention provides a method for calculating a circulation airflow circulation path in a straight-flow vertical shaft structure, which finds a critical value of air pressure by calculating the air pressure distribution in a wet pipe and an air pipe, and determines a path through which the inner circulation air can flow.
In a specific embodiment, first, the following model is built: as shown in fig. 1, a vertical partition plate is arranged at a radial position of a shaft with a sealed top end, one end of the vertical partition plate is connected with the top end of the shaft, so that the shaft is divided into a wet pipe section 40 and a gas pipe section 50, the wet pipe section 40 is connected with a water inlet pipe 20, the gas pipe section 50 is connected with an air inlet pipe 10, and the wet pipe section below the nappe is sequentially divided into a nappe blocking section, a constant section and a linear increasing section by taking the tail end of the air inlet pipe 20 as a base point.
And respectively calculating the air pressure distribution of each section in the wet pipe and the air pressure distribution in the air pipe under a certain amount of water, and obtaining an air pressure intersection point of the wet pipe section and the air pipe section, namely an air pressure critical value, wherein the position of the air pressure critical value is a critical position, and when one end of the partition plate is placed at the critical position or any position between the critical position and the top end of the vertical shaft, the air flow in the vertical shaft can form internal circulation air flow.
In a preferred embodiment, the specific calculation steps, based on the established model, are as follows:
s1, calculating the air pressure distribution in the wet pipe
(1) Air pressure at the inlet pipe
Figure BDA0003222973430000061
Wherein, PaDenotes atmospheric pressure, pa; p0Indicates the air pressure above the nappe, pa; kILoss factor of air inflow at the air inlet; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
Figure BDA0003222973430000062
Is the average flow velocity of the gas in the inlet line, m/s.
(2) Air pressure (P) of nappe blocking section0～P1)
Figure BDA0003222973430000063
In the formula:
Figure BDA0003222973430000064
representing dimensionless incoming water flow, QwM is the amount of the inflow3/s，DsDiameter of the shaft wet pipe section, m; p1Represents the air pressure under the water tongue, pa; vaRepresents the average flow velocity of the gas in the wet tube, m/s; a and b are constants related to the shaft structure.
(3) Constant section air pressure (P)1～P3)
P1＝P3 (4)
It will be understood that the jet will break down completely into water droplets after passing through the constant section.
(4) Linear growth section pressure (P)3～P8)
The gradient of the air pressure change in the linear growth section is as follows:
Figure BDA0003222973430000065
in the formula: cdTaking 0.4 as a dragging coefficient when the water drop falls; d-2 represents the diameter of the water drop, mm; v ═ 6 denotes the average speed at which the water droplets fall, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；VaRepresents the average flow velocity of the gas in the wet tube, m/s,
Figure BDA0003222973430000066
Figure BDA0003222973430000067
is the average flow velocity of the gas in the inlet pipe, m/s, DsDiameter of the shaft wet pipe section, m; dIDenotes the diameter of the inlet pipe, m.
S2, calculating the air pressure distribution in the trachea
(1) Determining average gas velocity in trachea
Figure BDA0003222973430000068
Figure BDA0003222973430000069
In the formula:
Figure BDA00032229734300000610
average velocity of gas in trachea, m3/s；DcRepresents the equivalent diameter of the trachea, m; dIDenotes the diameter of the inlet pipe, m;
Figure BDA0003222973430000071
is the average flow velocity of the gas in the inlet line, m/s.
(2) Determining the air pressure of a reference point for calculating the air pressure in the trachea
Figure BDA0003222973430000072
In the formula: p'downThe air pressure value, pa, of the air pipe side at the bottom of the partition board is shown; pdownThe air pressure value pa at the wet pipe at the bottom of the partition is shown; k is a radical ofbRepresenting the loss factor of the gas flow through the bottom of the vertical partition; vaRepresents the average flow velocity of the gas in the wet tube, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3。
(3) Gradient expression of air pressure in trachea
Figure BDA0003222973430000073
In the formula: delta PcRepresents the air pressure difference value between two points in the trachea, pa; dcRepresents the equivalent diameter of the trachea, m; f represents the friction coefficient of the tracheal wall; l distance between any two points in the trachea, m; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
Figure BDA0003222973430000074
Average velocity of gas in trachea, m3/s。
S3, determining a critical value of air pressure
According to the air pressure distribution of the wet pipe section obtained in the step S1 and the air pressure distribution of the air pipe section obtained in the step S2, the equal air pressure value between the wet pipe section and the air pipe section is the air pressure critical value.
S4, determining a circulation path capable of forming an internal circulation airflow
And determining the corresponding position of the air pressure critical value in the shaft according to the air pressure critical value determined in the step S3, namely the critical position, wherein when one end of the partition plate is placed at the critical position or placed at any position between the critical position and the top end of the shaft, the air flow in the shaft can form internal circulation air flow.
In a preferred embodiment, the circulating airflow path within the straight-through shaft structure has an optimum path: among the paths through which the internal circulation gas flow can be formed, when the partition plate is placed at different positions, the path with the least influence on the shaft suction and the upstream and downstream pressure difference during the gas flow is the optimal flow path.
It will be appreciated that the circulation flow can be from any location above the critical pressure location, but in order to minimise shaft suction, the circulation flow should be such that the pressure at the inlet tends towards atmospheric pressure, so that the pressure differential across the inlet tends to be from a location on the partition parallel to the inlet to 0 pa.
In a specific embodiment, the intake air amount in the intake pipe is calculated
Figure BDA0003222973430000075
And the pressure difference delta P between the upstream and the downstream of the vertical shaft, and determining the influence of gas circulation on the air suction of the vertical shaft and the pressure difference between the upstream and the downstream.
Intake air amount in the intake pipe
Figure BDA0003222973430000076
And the shaft upstream and downstream differential pressure Δ P are calculated as follows:
Figure BDA0003222973430000077
in the formula: a. theIDenotes the cross-sectional area of the intake pipe, m2；
Figure BDA0003222973430000081
The average flow velocity of the gas in the gas inlet pipe is m/s;
ΔP＝P8-P0 (10)
in the formula: Δ P represents the pressure difference upstream and downstream in the shaft; p0Indicates the air pressure above the nappe, pa; p8The gas pressure at the flow tube, pa, is shown.
In another specific embodiment, when one end of the baffle plate is positioned below the gas inlet pipe and the circulating gas is caused to circulate from the baffle plate at a position parallel to the gas inlet pipe, the resulting flow path is an optimal flow path.
In practical application, if any upstream and downstream condition in the shaft is known, the air pressure distribution condition in the wet pipe and the air pipe in the shaft can be obtained, the air pressure critical value in the wet pipe and the air pipe is further obtained, and finally, the optimal path through which the circulating airflow can circulate is found.
For better understanding, the present invention is further described below with reference to specific examples, but the present invention is not limited thereto.
[ example 1 ]
Establishing a coordinate axis which takes the tail end of the water inlet pipe 20 as an origin (a nappe position) and is in a positive direction downwards as shown in figure 1; the shaft height is 7.72m (vertical distance from the bottom of the inlet pipe 20 to the bottom of the outlet pipe 60), and the equivalent diameter D of the wet pipe 40sEquivalent diameter D of the air tube 50cIs also 0.265m, the diameter D of the inlet pipe 10IIs 0.1m, the diameter of the outlet pipe 60 is 0.38m, and the diameter of the inlet pipe 20 is 0.19 m. The top of the shaft is sealed and gas can only enter through the inlet pipe 10 and water flows through the inlet pipe 20 to the wet pipe 40 and then flows out through the outlet pipe 60, and the outlet pipe 60 is communicated with the atmosphere.
Corresponding to, P0The air pressure at the air inlet pipe can be selected from the air pressure at the position Z being-0.64 m, namely the position 0.64m above the nappe.
It should be understood that the air pressure at the air inlet pipe is the air pressure above the nappe and around the air inlet pipe, and in practical application, P is the air pressure around the air inlet pipe, no matter how the size of the shaft changes0The corresponding position can be selected to be 0.64m above the nappe.
P1The air pressure below the nappe can be selected to be the air pressure at the position where Z is 0.64m, namely, the position 0.64m below the nappe, namely, the nappe blocking section (P) in the embodiment0～P1) From 0.64m above the nappy to 0.64m below the nappy.
In practice, P is no matter how the size of the shaft varies1The corresponding position can be selected to be 0.64m below the nappe.
In practical application, for the shaft structure with other heights, most of water flow is in a jet flow state when falling from the shaft, the jet flow is completely decomposed into water drops after falling to a certain height, the pressure change of the height in the jet flow decomposition process is not a constant pressure section, and the height of the section is expressed as:
H＝100D (11)
in the formula: h represents the height of jet break-up, m; d represents the diameter of the jet, m;
the height below H is the linear increasing section, the upper part is the nappe blocking section, H is P3The corresponding position.
In this embodiment, the jet diameter D is known to be 2.64cm, and according to the formula H being 100D, the height H of the jet which is completely decomposed into water droplets is known to be 2.64m, that is, P3The corresponding position of (2) is 2.64m below the nappe, i.e. the constant air pressure section (P) in this embodiment1～P3) Linear increasing section (P) of 0.64m to 2.64m below the nappe3～P8) 2.64m to 7.34m below the nappy.
P8The pressure at the outlet pipe, i.e. 7.34m below the nappe, is known to be open to the atmosphere, so P8＝0pa。
First, calculating the air pressure distribution in the wet pipe
1. Air pressure at air inlet pipe
Formula (1) gives formula 1.1:
Figure BDA0003222973430000091
the mass conservation can obtain that the gas flow in the gas inlet pipe and the vertical shaft is equal:
Figure BDA0003222973430000092
Then
Figure BDA0003222973430000093
namely, formula 1.2:
Figure BDA0003222973430000094
formula 1.1 and formula 1.2 give1.3，
Figure BDA0003222973430000095
2、P0～P1Water tongue separation section
Formula (3) gives formula 1.4:
Figure BDA0003222973430000096
3、P1～P3is a constant section of air pressure
Formula (4) gives formula 1.5: p1＝P3
4. Linear increasing section
Formula (5) gives formula 1.6:
Figure BDA0003222973430000097
p due to the outlet pipe opening to the atmosphere8(Z7.34 m) 0pa, and P1＝P3So that P is8And P3(Z ═ 2.64m) was obtained by substituting formula 1.6 with the following pressure difference:
Figure BDA0003222973430000098
after finishing, the formula is 1.7:
Figure BDA0003222973430000099
vertical combination 1.3, formula 1.4 and formula 1.7
Figure BDA0003222973430000101
Calculable P at different flow rates0、P1And VaThe results are shown in Table 1
TABLE 1 gas parameters found at different flow rates
Figure BDA0003222973430000102
According to the determined gas parameter P0、P1And VaIf Z is-0.64, 1.64, 2.64, 3.64, 4.64, 5.64, 6.64, 6.95, 7.34m and the like, 10 feature points are taken as the air pressure, and the air pressure of each of the 10 feature points is P0、P1、P2、P3、P4、P5、P6、P7、Pdown、P8And calculating the air pressure value according to the corresponding equation of each air pressure position, wherein the result is shown in the table 2:
TABLE 2 Wet pipe section pressure distribution
Figure BDA0003222973430000103
Note: in table P8Are all around 0pa, indicating that the algorithm is accurate.
Secondly, calculating the air pressure distribution of the air pipe section
1. Calculating the average gas velocity in the trachea
Figure BDA0003222973430000104
Formula (6) gives formula 2.1:
Figure BDA0003222973430000105
calculated in Table 2
Figure BDA0003222973430000106
By substituting formula 2.1, can be obtained
Figure BDA0003222973430000107
Figure BDA0003222973430000108
The corresponding values of (A) are shown in Table 2.
2. Determining the air pressure at a reference point for calculation of air pressure in the trachea
Formula (2.2) from formula (7):
Figure BDA0003222973430000109
Pdownthe calculation process is not repeated for the air pressure at the position where Z is 6.95m in the wet tube, and P is not described any moredownThe corresponding values are shown in Table 2
V in Table 1aAnd P calculated in Table 2downSubstitution formula 2.2, air pressure P 'at 6.95m of Z in trachea is obtained'downThe results are shown in Table 3
TABLE 3 air pressure values at the bottom of the separator on the air tube side
Figure BDA0003222973430000111
3. Gradient expression of air pressure in trachea
Formula (2.3) from formula (8):
Figure BDA0003222973430000112
knowing the expression of the air pressure gradient in the trachea, will be shown in equations 2.1 and 2.2
Figure BDA0003222973430000114
And P'downIn the formula 2.3, the air pressure in the air pipe was determined, and the air pressures in the air pipes corresponding to the 9 characteristic points in the wet pipe were P'0、P′1、P′2、P′3、P′4、P′5、P′6、P′7、P′downThe respective air pressure values were calculated according to the formula 2.3, and the results are shown in Table 4:
TABLE 4 gas pipe section pressure distribution
Figure BDA0003222973430000113
Thirdly, determining the critical air pressure value and forming the circulation path of the internal circulation air flow
According to the air pressure values in tables 2 and 4, the point position of the shaft is taken as the X axis, the air pressure corresponding to the point position is taken as the Y axis, and the graph is shown as figure 2, wherein the solid line represents the air pressure in the wet pipeThe broken line represents the air pressure in the air pipe, and the curves of the air pressure in the wet pipe and the air pipe have an intersection point corresponding to each flow, the air pressure at the intersection point is the critical air pressure, the position is the critical position, and the critical air pressure and the corresponding position are estimated according to the figure, for example, when Q iswWhen the critical air pressure is 11.6, 26.1 and 33.5L/s, the critical positions corresponding to the corresponding critical air pressure are 5.6, 5.7 and 6.3m, and the circulating air flow can flow from the air pipe to the wet pipe from any position above the critical positions Z is 5.6, 5.7 and 6.3 m.
Fourthly, determining the optimal circulation path of the internal circulation airflow
When the internal circulation gas flows along a path parallel to the gas inlet pipe (the position of one end of the baffle plate is Z-0.6 m, which is called as position 1) and the other path (the position of one end of the baffle plate is Z-2 m, which is called as position 2), the gas in the wet pipe is circulated by the gas in the gas inlet pipe
Figure BDA0003222973430000121
And the internal circulation air flow in the air pipe
Figure BDA0003222973430000122
Two parts are composed, therefore
Figure BDA0003222973430000123
Namely, it is
Formula 4.1:
Figure BDA0003222973430000124
integrated 1.3, 1.4, 1.7 and 4.1, to obtain the gas parameters of the separator at position 1 (Table 5) and at position 2 (Table 6)
TABLE 5 gas parameters for circulating gas flow parallel to the inlet manifold
Figure BDA0003222973430000125
Table 6 gas parameters of the recycle gas stream in other paths
Figure BDA0003222973430000126
Calculating the air inflow of the air inlet pipe at different partition positions in the flow path of the internal circulation air flow
Figure BDA0003222973430000127
And the air inflow in the differential pressure delta P air inlet pipe between the upper stream and the lower stream of the vertical shaft
Figure BDA0003222973430000128
The calculation is as follows:
formula (4.2) from formula (9):
Figure BDA0003222973430000129
in the formula
Figure BDA00032229734300001210
See tables 5 and 6, AIThe cross-sectional area of the air inlet pipe is 0.00785m in the embodiment2；
2. Differential pressure delta P between upstream and downstream of vertical shaft
Formula (4.3) from formula (10): Δ P ═ P8-P0In the formula P0See tables and tables, and P8Calculated as 0 pa;
therefore, the calculated air inlet pipe air inflow of the circulating airflow from different path flows
Figure BDA00032229734300001211
And the pressure difference delta P between the upper part and the lower part of the shaft is shown in the table:
TABLE 7 intake air amount and upstream-downstream pressure difference at different routes
Figure BDA00032229734300001212
Figure BDA0003222973430000131
Combination drawing3 and 4, on the one hand, it can be seen that when the internal circulation flow circulates along a line parallel to the inlet pipe,
Figure BDA0003222973430000132
and the delta P has small fluctuation and is relatively stable; on the other hand, than under other paths
Figure BDA0003222973430000133
And deltap, when the internal circulation flow circulates along a line parallel to the inlet pipe,
Figure BDA0003222973430000134
and ap are reduced by about 56% and 81%, respectively, and other paths, although circulation of the circulating air stream may be formed, will obviously not improve the performance of the shaft as well as when the internal circulating air stream is circulated parallel to the inlet duct, and it can be determined that when the internal circulating air stream is circulated parallel to the inlet duct, i.e. with one end of the baffle below the inlet duct (as shown in figure 5), the resulting flow path is the optimum flow path.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims (6)

1. A method for calculating a circulation airflow path in a straight-through shaft structure,
first, the following model was built: arranging a vertical partition plate at the radial position of a vertical shaft with a sealed top end, wherein one end of the vertical partition plate is connected with the top end of the vertical shaft, so that the vertical shaft is divided into a wet pipe section and an air pipe section, the wet pipe section is connected with a water inlet pipe, the air pipe section is connected with a vent pipe, and the wet pipe section below a nappe is sequentially divided into a nappe blocking section, a constant section and a linear lengthening section by taking the nappe as a base point;
and respectively calculating the air pressure distribution of each section in the wet pipe and the air pressure distribution in the air pipe under a certain amount of water, and obtaining an air pressure intersection point of the wet pipe section and the air pipe section, namely an air pressure critical value, wherein the position of the air pressure critical value is a critical position, and when one end of the partition plate is placed at the critical position or any position between the critical position and the top end of the vertical shaft, the air flow in the vertical shaft can form internal circulation air flow.
2. The method according to claim 1, wherein the calculation steps are as follows according to the established model:
s1, calculating the air pressure distribution in the wet pipe
(1) Air pressure at the inlet pipe
Figure FDA0003222973420000011
Wherein, PaDenotes atmospheric pressure, pa; p0Indicates the air pressure above the nappe, pa; kILoss factor of air inflow at the air inlet; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
Figure FDA0003222973420000014
The average flow velocity of the gas in the gas inlet pipe is m/s;
(2) air pressure (P) of nappe blocking section0～P1)
Figure FDA0003222973420000012
In the formula:
Figure FDA0003222973420000013
representing dimensionless incoming water flow, QwM is the amount of the inflow3/s，DsDiameter of the shaft wet pipe section, m; p1Represents the air pressure under the water tongue, pa; vaRepresents the average flow rate of gas in the wet tubeM/s; a and b are constants related to the vertical shaft structure;
(3) constant section air pressure (P)1～P3)
P1＝P3 (4)
(4) Linear growth section pressure (P)3～P8)
The gradient of the air pressure change in the linear growth section is as follows:
Figure FDA0003222973420000021
in the formula: cdTaking 0.4 as a dragging coefficient when the water drop falls; d-2 represents the diameter of the water drop, mm; v ═ 6 denotes the average speed at which the water droplets fall, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；VaRepresents the average flow velocity of the gas in the wet tube, m/s,
Figure FDA0003222973420000022
Figure FDA0003222973420000023
is the average flow velocity of the gas in the inlet pipe, m/s, DsDiameter of the shaft wet pipe section, m; dIDenotes the diameter of the inlet pipe, m;
s2, calculating the air pressure distribution in the trachea
(1) Determining average gas velocity in trachea
Figure FDA0003222973420000024
Figure FDA0003222973420000025
In the formula:
Figure FDA0003222973420000026
average velocity of gas in trachea, m3/s；DcRepresents the equivalent diameter of the trachea, m; dIDenotes the diameter of the inlet pipe, m;
Figure FDA0003222973420000027
the average flow velocity of the gas in the gas inlet pipe is m/s;
(2) determining the air pressure of a reference point for calculating the air pressure in the trachea
Figure FDA0003222973420000028
In the formula: p'downThe air pressure value, pa, of the air pipe side at the bottom of the partition board is shown; pdownThe air pressure value pa at the wet pipe at the bottom of the partition is shown; k is a radical ofbRepresenting the loss factor of the gas flow through the bottom of the vertical partition; vaRepresents the average flow velocity of the gas in the wet tube, m/s; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；
(3) Gradient expression of air pressure in trachea
Figure FDA0003222973420000029
In the formula: delta PcRepresents the air pressure difference value between two points in the trachea, pa; dcRepresents the equivalent diameter of the trachea, m; f represents the friction coefficient of the tracheal wall; l distance between any two points in the trachea, m; rhoaGas density in kg/m at standard atmospheric pressure at room temperature3；Va cAverage velocity of gas in trachea, m3/s；
S3, determining a critical value of air pressure
According to the air pressure distribution of the wet pipe section obtained in the step S1 and the air pressure distribution of the air pipe section obtained in the step S2, the equal air pressure value between the wet pipe section and the air pipe section is the air pressure critical value;
s4, determining a circulation path capable of forming an internal circulation airflow
And determining the corresponding position of the air pressure critical value in the shaft according to the air pressure critical value determined in the step S3, namely the critical position, wherein when one end of the partition plate is placed at the critical position or placed at any position between the critical position and the top end of the shaft, the air flow in the shaft can form internal circulation air flow.
3. Method for calculating a circulation flow path in a straight-through shaft structure according to claim 1 or 2, characterised in that the circulation flow path in the straight-through shaft structure has an optimal flow path: among the paths through which the internal circulation gas flow can be formed, when the partition plate is placed at different positions, the path with the least influence on the shaft suction and the upstream and downstream pressure difference during the gas flow is the optimal flow path.
4. The method for calculating the circulation air flow path in the straight-flow shaft structure as claimed in claim 3, wherein the calculation is performed by calculating the amount of intake air in the intake pipe
Figure FDA0003222973420000031
And the pressure difference delta P between the upstream and the downstream of the vertical shaft, and determining the influence of gas circulation on the air suction of the vertical shaft and the pressure difference between the upstream and the downstream.
5. The method for calculating the circulation flow path in the straight-flow shaft structure according to claim 4, wherein the amount of intake air in the intake pipe is set
Figure FDA0003222973420000032
And the shaft upstream and downstream differential pressure Δ P are calculated as follows:
Figure FDA0003222973420000033
in the formula: a. theIDenotes the cross-sectional area of the intake pipe, m2；
Figure FDA0003222973420000034
The average flow velocity of the gas in the gas inlet pipe is m/s;
ΔP＝P8-P0 (10)
in the formula: Δ P represents the pressure difference upstream and downstream in the shaft; p0Indicates the air pressure above the nappe, pa; p8The gas pressure at the flow tube, pa, is shown.
6. The method for calculating the flow path of the circulating gas in the straight-flow shaft structure according to claim 3, wherein when one end of the partition plate is positioned below the gas inlet pipe and the circulating gas is caused to flow from the partition plate at a position parallel to the gas inlet pipe, the resulting flow path is the optimum flow path.
CN202110963114.6A 2021-08-20 2021-08-20 Method for calculating circulation airflow circulation path in straight-flow vertical shaft structure Pending CN113901635A (en)

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