CN114357586B - Method for calculating cross-sectional area of exhaust channel at lower flat section of tunnel plug flood discharge tunnel - Google Patents
Method for calculating cross-sectional area of exhaust channel at lower flat section of tunnel plug flood discharge tunnel Download PDFInfo
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- CN114357586B CN114357586B CN202210020575.4A CN202210020575A CN114357586B CN 114357586 B CN114357586 B CN 114357586B CN 202210020575 A CN202210020575 A CN 202210020575A CN 114357586 B CN114357586 B CN 114357586B
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Abstract
The invention relates to a method for calculating the cross-sectional area of an exhaust channel at the lower flat section of a hole plug flood discharge tunnel, belonging to the hole plug of a hydropower stationThe technical field of flood discharge tunnel structure design. The time required from the opening of the inlet control gate to the filling of the lower flat Duan Gang is set as t, the state of filling the lower flat Duan Gang in the invention means that the water surface at the starting end of the lower flat section is flush with the top of the hole at the position, and the orifice drainage capacity of the inlet control gate is Q Feeding in The outlet pressure slope orifice leakage capacity is Q Out of . The method for judging that the lower flat section of the hole plug flood discharge tunnel is full of water comprises the following steps: the outlet control gate orifice has a bleed capacity not less than the outlet pressure ramp orifice. The invention can accurately estimate the cross-sectional area of the exhaust channel in the early design stage, is used for guiding the design of hydraulic model test schemes, and reduces the number of comparison schemes of the hydraulic model test, thereby saving the test cost and the test time of the hydraulic model test.
Description
Technical Field
The invention relates to a method for calculating the cross-sectional area of an exhaust channel at the lower flat section of a hole-plug flood discharge tunnel, and belongs to the technical field of structural design of hole-plug flood discharge tunnels of hydraulic and hydroelectric engineering.
Background
The hole plug flood discharging tunnel is characterized in that a hole plug energy dissipater is arranged in the tunnel, the diameter of a section of the hole plug is reduced, and the water flow is utilized to flow through the hole plug to generate sudden shrinkage and sudden expansion to cause severe turbulence of water flow so as to dissipate water flow energy, thereby reducing the flow velocity of water flow at the downstream of an outlet and relieving the flushing of a downstream river bed.
The hole plug flood discharge tunnel has the characteristics of stable water flow state, simple structure, flexible arrangement and the like, and is suitable for downstream high water level conditions. The diversion tunnel in the engineering has low elevation, and can often meet the condition of being reconstructed into a tunnel plug flood discharge tunnel. In addition, the tunnel plug flood discharging tunnel has the advantages of simple structure, convenient reconstruction construction and saving engineering investment compared with other reconstruction types, so that the tunnel plug flood discharging tunnel is generally used for reconstructing the diversion tunnel into a permanent flood discharging tunnel.
The tunnel plug flood discharging tunnel generally comprises an inlet control section, an upper flat section, a vertical shaft section, a lower flat section and an outlet, wherein the lower flat section is often divided into a tunnel plug energy dissipation section and a water drainage tunnel, and can be also fully arranged as the tunnel plug energy dissipation section. The dissipater is generally comprised of a multi-stage vertical plug disposed in the shaft section and a multi-stage horizontal plug disposed in the horizontal section. In order to ensure that enough positive pressure exists in the hole plug so as to prevent water flow cavitation and cavitation damage of a tunnel structure, a pressure slope structure is usually arranged at the tail end of an energy dissipation section of the hole plug.
In order to reduce the scale of the working gate, the working gate is generally arranged at an inlet, when the downstream water level is lower and the water flow is not full of the lower flat section of the tunnel, the gate is opened, a pressure air bag is formed by gas at the upper part of the lower flat section under the pressure action before the water flow is sealed up at the orifice of the outlet slope pressing section, and the pressure air bag moves to the orifice of the slope pressing section to generate the air explosion phenomenon under the carrying action of the water flow. In order to avoid the occurrence of the gas explosion phenomenon, it is generally necessary to provide an exhaust passage at the lower flat section. For a specific structural scheme of the hole plug flood discharge hole, reference is made to patent document with publication number CN 209429070U.
Because the hole plug flood discharging tunnel is still less in application in engineering practice, the design theory of the hole plug flood discharging tunnel is still to be further studied and perfected, and the method for calculating the sectional area of the lower flat section exhaust channel is not proposed at present. In the prior art, the cross-sectional area of the exhaust channel is mainly determined through a hydraulic model test, and due to the lack of a calculation method of the cross-sectional area of the exhaust channel, the design of the exhaust channel of the hole plug flood discharge tunnel is difficult to develop in the early design stage, a large number of hydraulic model test comparison schemes are required to be designed, and the test cost and the test time are increased.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the method for calculating the cross-sectional area of the exhaust channel of the lower flat section of the hole plug flood discharge tunnel can save the test cost and the test time of hydraulic model tests.
The technical scheme adopted by the invention for solving the technical problems is as follows: the method for calculating the cross-sectional area of the exhaust channel of the lower flat section of the hole plug flood discharge tunnel comprises the following steps:
1. the following process parameters are obtained in advance: inlet control gate orifice flow coefficient mu Feeding in Inlet control gate orifice width B, gate head H from orifice floor 0 Outlet flooding coefficient sigma s Area A of the cross section of the exit orifice of the pressure slope Out of Lower flat section starting head H from outlet floor elevation Upper part Outlet head H from outlet floor elevation Lower part(s) Gate lift rate v, exhaust passage allowable wind speed v w ]And a gas volume V enclosed at the top of the lower flat section hole; the gas volume V sealed at the top of the lower flat section is the volume of a cavity above the water surface between the hole plug sections when the lower flat section of the hole plug flood discharge hole is sealed by the water body at the slope pressing orifice;
2. the inlet control gate orifice opening height e is calculated according to the following formula:
wherein g is gravitational acceleration;
3. the time t required to fill the water from the inlet control gate opening to the lower level Duan Gang is calculated according to the following equation:
t＝e/v；
4. the exhaust passage cross-sectional area a is calculated according to the following formula:
further is: the lower Ping Duangang is full of water, and the water surface at the beginning end of the lower flat section is flush with the top of the hole at the position.
Further is: the gas volume V enclosed at the top of the lower flat section hole is calculated according to the following formula:
V＝∑A empty space L，
Wherein: a is that Empty space The area of the cavity above the water surface of the flow section of the lower flat section tunnel is;
l is the length of each section of the lower flat section tunnel.
The beneficial effects of the invention are as follows: the section area of the exhaust channel can be accurately estimated in the early design stage, and the section area is used for guiding the design of hydraulic model test schemes, and the number of comparison schemes of the hydraulic model test is reduced, so that the test cost and the test time of the hydraulic model test are saved.
Drawings
Fig. 1 is a schematic diagram of a hole plug flood discharge tunnel structure according to the present invention.
Fig. 2 is an enlarged view of the hole plug.
The marks in the figure: the device comprises a hole body 1, an inlet control section 11, an upper flat section 12, a shaft section 13, a lower flat section 14, a hole plug 2, an outlet pressure slope 3, a stilling pool 4, a tail sill 5, a gate 6 and an exhaust channel 7.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
Referring to fig. 1 and 2, the hole plug flood discharge tunnel comprises a tunnel body 1, wherein the tunnel body 1 comprises an inlet control section 11, an upper flat section 12, a vertical shaft section 13 and a lower flat section 14 which are sequentially arranged along the upstream-to-downstream direction, an outlet pressure slope 3 is arranged at the downstream end of the lower flat section 14, a hole plug 2 is arranged in each of the vertical shaft section 13 and the lower flat section 14, and an overflow hole is arranged in the middle of the hole plug 2; the top of the hole plug 2 is provided with a hole plug exhaust hole as an exhaust channel 7, and the exhaust channel 7 at the downstream end of the lower flat section 14 can extend out of the hole directly along the horizontal direction or can be vertically communicated out of the hole after turning. In order to enable the air in the tunnel body 1 to be smoothly discharged during flood discharge, the cross-sectional area of the air discharge channel 7 needs to be reasonably designed. The invention is applied to accurately estimating the cross-sectional area of the exhaust passage 7 in the early design stage. The specific calculation method of the invention is as follows:
1. the following process parameters are obtained in advance: inlet control gate orifice flow coefficient mu Feeding in Inlet control gate orifice width B, gate head H from orifice floor 0 Outlet flooding coefficient sigma s Lower plateau flow coefficient mu Lower part(s) Area A of the cross section of the exit orifice of the pressure slope Out of Lower flat section starting head H from outlet floor elevation Upper part Outlet head H from outlet floor elevation Lower part(s) Gate lift rate v, exhaust passage allowable wind speed v w ]And the gas volume V sealed at the top of the lower flat section is the volume of a cavity above the water surface between the hole plug sections when the lower flat section of the hole plug flood discharge hole is sealed by water body at the slope pressing orifice.
Wherein the inlet controls the width of the gate orificeB, front water head H from orifice bottom plate 0 Area A of the cross section of the exit orifice of the pressure slope Out of Lower flat section starting head H from outlet floor elevation Upper part Outlet head H from outlet floor elevation Lower part(s) Gate lifting rate v (inlet control gate is opened at constant speed), exhaust channel allowable wind speed v w ]Are all known parameters and can be directly known from a design drawing; inlet control gate orifice flow coefficient mu Feeding in Outlet flooding coefficient sigma s Lower plateau flow coefficient mu Lower part(s) Also known parameters, can be looked up by a specification or manual; the volume V of the gas enclosed at the top of the lower flat section hole can be calculated according to the following formula:
V＝∑A empty space L，
Wherein: a is that Empty space The area of the cavity above the water surface of the flow section of the lower flat section tunnel is;
l is the length of each section of the lower flat section tunnel.
2. The inlet control gate orifice opening height e is calculated according to the following formula:
wherein g is gravitational acceleration;
3. the time t required to fill the water from the inlet control gate opening to the lower level Duan Gang is calculated according to the following equation:
t＝e/v；
4. the exhaust passage cross-sectional area a is calculated according to the following formula:
the design principle of the calculation method is as follows: the time from the opening of the inlet control gate to the filling of the lower flat Duan Gang is set as t, the state of filling the lower flat Duan Gang in the invention means that the water surface at the starting end of the lower flat section is flush with the top of the hole at the position, and the orifice drainage capacity of the inlet control gate is Q Feeding in The outlet pressure slope orifice leakage capacity is Q Out of . Under the general condition, the flood discharging tunnel with the hole plug has larger water heads for the inlet and the outlet, and the inlet and the outlet are the outflow of the hole. Therefore, the method for judging whether the lower flat section of the hole plug flood discharge tunnel is full of water comprises the following steps: the outlet control gate orifice has a bleed capacity not less than the outlet pressure ramp orifice. I.e. at least Q should be satisfied Feeding in ＝Q Out of 。
Therefore, the invention adopts the formula of the step two to calculate the opening height e of the orifice of the inlet control gate.
Implementation case:
taking a monkey rock hydropower station as an example, calculating results of the inlet and outlet drainage capacities of the monkey rock hydropower station are shown in tables 1 and 2, calculating the drainage capacity of the lower flat section of the drainage tunnel according to a long pipe with pressure, and adopting a model test actual measurement value, namely 0.36, of the flow coefficient.
When the upstream water level is the upper flat section lining roof arch elevation, the drainage capacity is 332.8m 3 And/s, and inversely calculating the opening degree of the inlet gate orifice to be 1.28m according to the drainage capacity. The inlet working gate is a flat gate, the gate is opened at a constant speed, the gate lifting time from closing to full opening is 30min, the gate opening time corresponding to the 1.28m opening of the gate is 3.48min, namely the time required for filling the hole with water is basically consistent with the duration of the observed 'gas explosion' phenomenon.
When the lower flat section of the flood discharging tunnel is sealed by water, the air in the cavity above the water surface between the hole plug sections cannot be discharged freely, and 35m/s is taken according to the calculated water filling time, the calculated air volume of the cavity at the top of the tunnel and the allowable air speed in the air discharging channel, and the calculated cross section area of the air discharging channel is shown in Table 3.
TABLE 1 calculation results table of import bleeder capacity
Table 2 calculation results table for the drainage capacity of the exit pressure slope orifice
TABLE 3 calculation of exhaust passage cross-sectional area
Claims (2)
1. The method for calculating the cross-sectional area of the exhaust channel of the lower flat section of the hole plug flood discharge tunnel is characterized by comprising the following steps of: the method comprises the following steps:
1. the following process parameters are obtained in advance: inlet control gate orifice flow coefficient mu Feeding in Inlet control gate orifice width B, gate head H from orifice floor 0 Outlet flooding coefficient sigma s Lower plateau flow coefficient mu Lower part(s) Area A of the cross section of the exit orifice of the pressure slope Out of Lower flat section starting head H from outlet floor elevation Upper part Outlet head H from outlet floor elevation Lower part(s) Gate lift rate v, exhaust passage allowable wind speed v w ]And a gas volume V enclosed at the top of the lower flat section hole; the gas volume V sealed at the top of the lower flat section is the volume of a cavity above the water surface between the hole plug sections when the lower flat section of the hole plug flood discharge hole is sealed by the water body at the slope pressing orifice; the gas volume V enclosed at the top of the lower flat section hole is calculated according to the following formula:
V=ΣA empty space L，
Wherein: a is that Empty space The area of the cavity above the water surface of the flow section of the lower flat section tunnel is;
l is the length of each section of the lower flat section tunnel;
2. the inlet control gate orifice opening height e is calculated according to the following formula:
wherein g is gravitational acceleration;
3. the time t required to fill the water from the inlet control gate opening to the lower level Duan Gang is calculated according to the following equation:
t=e/v；
4. the exhaust passage cross-sectional area a is calculated according to the following formula:
2. the method for calculating the cross-sectional area of the exhaust channel of the lower flat section of the hole-plug flood discharge tunnel according to claim 1, wherein the method comprises the following steps: the lower Ping Duangang is full of water, and the water surface of the starting end of the lower flat section is flush with the top of the hole of the starting end of the lower flat section.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210020575.4A CN114357586B (en) | 2022-01-10 | 2022-01-10 | Method for calculating cross-sectional area of exhaust channel at lower flat section of tunnel plug flood discharge tunnel |
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| CN202210020575.4A CN114357586B (en) | 2022-01-10 | 2022-01-10 | Method for calculating cross-sectional area of exhaust channel at lower flat section of tunnel plug flood discharge tunnel |
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| CN114357586B true CN114357586B (en) | 2023-06-13 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101812832B (en) * | 2010-03-26 | 2011-05-11 | 四川大学 | Submerged cyclone shaft sluice tunnel |
| CN106381831B (en) * | 2016-09-05 | 2018-08-24 | 中国电建集团成都勘测设计研究院有限公司 | A kind of method of determining air entraining facilities venthole cross-sectional area |
| CN209429070U (en) * | 2018-11-29 | 2019-09-24 | 中国电建集团成都勘测设计研究院有限公司 | Fill in flood discharging tunnel figure in hole |
| CN110197001B (en) * | 2019-04-30 | 2022-09-16 | 华能澜沧江水电股份有限公司 | Combined optimization design method for ventilation holes and residual amplitude at top of spillway tunnel |
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