CN104234019A - Cross-section-variable pressure regulating chamber - Google Patents

Abstract

The invention discloses a surge chamber with variable cross-section. The cave body sequentially includes a first surge chamber section, a section with a gradual change in cross-sectional area and a second surge chamber section along the height direction, and the section with a gradual change in cross-sectional area is connected with the first surge chamber section. and the second surge chamber section, wherein the section area of the first surge chamber section is the stable section area of the surge chamber corresponding to the downstream low water level, and the section area of the second surge chamber section is the stable section area of the surge chamber corresponding to the full flow Area, under special circumstances, no gradient section of cross-sectional area is required. The invention is suitable for the open flood tail water system, can reduce the scale of the downstream surge chamber, is beneficial to the stability of the underground cavern group, reduces the excavation and support engineering quantity of the cavern, and reduces the engineering cost.

Description

variable section surge chamber

technical field

The invention relates to a structural type of a surge chamber of a hydropower station, in particular to a variable-section surge chamber suitable for an open flood tail water system.

Background technique

With the development of hydropower resources in Southwest my country, many giant and large-scale hydropower stations under planning, design and construction are located in steep terrain and narrow valleys. The riverbed can only be used to arrange water retaining and flood discharge structures, while water transmission and power generation Buildings for water diversion, diversion and some flood discharge must be arranged in the mountains on both banks, which is a typical overall layout of the hub.

When the hydropower station adopts the head type and middle type development methods, the tailrace tunnel is relatively long, and generally a downstream surge chamber (3) needs to be installed to meet the minimum absolute pressure of the inlet section (4) of the draft tube of the hydropower station to meet the requirements of the code and design. In practice, in order to reduce the engineering volume of the tailrace tunnel and the tailwater outlet slope, avoid the excavation support and stability problems of artificial high and steep slopes, and reduce the damage to the surface vegetation and the environment, it is often necessary to consider the "permanent combination ", that is, make full use of the combination of temporary buildings and permanent buildings during the construction period, carry out unified layout and design, and combine the power station tailwater tunnel with the diversion tunnel, which may become a more advantageous layout scheme.

The combined tunnel section (9) of the tailrace tunnel and diversion tunnel of the power station should be of flat slope type as much as possible to take into account and adapt to the outflow requirements of the tailrace tunnel and diversion tunnel of the power station. In the water conveyance system of the tailrace tunnel, when the downstream tailwater level changes from low water level to high water level, the water flow states of open flow, open full flow and full flow appear in the tailrace tunnel, and the length of the pressure section of the tailwater is correspondingly determined by The minimum length at the lowest tailwater level reaches the full length of the tailrace tunnel at full flow. According to the water flow state and hydraulic characteristics of the tailrace tunnel, the tunnel body section of the downstream surge chamber (3) can break through the conventional equal-section type, and adopt variable-section types with different areas and shapes, in order to reduce the scale of the downstream surge chamber, which is beneficial to The stability of the underground cavern group reduces the amount of cavern excavation and support works, and reduces the project cost.

According to the "Code for Design of Surge Chambers of Hydropower Stations", the stable cross-sectional area F of the downstream surge chamber is:

F=KF _Th (1)

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Th</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Lf</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; g\&alpha;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; wm</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In formula (1)～(2):

F _Th is the critical stable section area of Thomas, unit: m ² ;

L is the length of the pressure tailrace, unit: m; the said pressure tailrace is the pressure waterway between the downstream surge chamber and the open-flood interface or the tailwater outlet;

f is the cross-sectional area of the pressure tailrace, unit: m ² ;

H ₀ is the minimum gross water head for power generation, unit: m;

α is the head loss coefficient from the downstream surge chamber to the downstream channel or reservoir, including local head loss and head loss along the way, α=h _w0 /v ² ;

v is the average velocity of the pressure tailrace, unit: m/s;

h _w0 is head loss of pressure tailrace, unit: m;

h _wm is the total head loss of the upstream pipeline of the downstream surge chamber, including the head loss of the pressure pipe and the extension section of the draft tube, unit: m;

K is a coefficient, which is generally selected within 1.0 to 1.1. When K<1.0 is selected, there should be a reliable argument;

g is gravitational acceleration, unit: m/s ² .

Contents of the invention

The object of the present invention is to provide a variable-section surge chamber suitable for the open flood tail water system, which can reduce the scale of the middle and downstream surge chambers of the open flood tail water system, which is beneficial to the stability of the underground cavern group, reducing Cavern excavation and support works, reducing project cost.

To achieve the above object, the technical scheme of the present invention is as follows:

A surge chamber with a variable cross-section, the cave body includes a first surge chamber section, a section with a gradual change in cross-sectional area, and a second surge chamber section from bottom to top along the height direction, and the gradual change in cross-sectional area is connected to the first surge chamber section and the second surge chamber section. The second surge chamber section, wherein the cross-sectional area of the first surge chamber section is the stable cross-sectional area of the surge chamber corresponding to the downstream low water level, and the cross-sectional area of the second surge chamber section is the stable cross-sectional area of the surge chamber corresponding to the full flow ;The section shapes of the first surge chamber section and the second surge chamber section are the same or different, and the section shape is designed according to actual needs; the bottom and top elevations of the section area gradient section are based on the downstream low water level and tail water outlet flow channel of the actual project The elevation of the top of the hydropower station is set to ensure that the regulation parameters of the hydropower station meet the requirements of the specification and design under various working conditions.

The cross-sectional shapes of the first surge chamber section, the cross-sectional area transition section and the second surge chamber section are rectangular, circular, elliptical or semi-elliptical.

Another type of surge chamber with variable cross-section, the cave body includes the first surge chamber section and the second surge chamber section from bottom to top along the height direction, and the cross-sectional area of the first surge chamber section is from the surge chamber to the full The length of the outlet of the inclined section of the tail water tunnel is the stable cross-sectional area of the surge chamber calculated from the length of the pressure tailrace, and the cross-sectional area of the second surge chamber is the corresponding stable cross-sectional area of the surge chamber at full flow; The cross-sectional shape of the surge chamber section and the second surge chamber section is the same or different, and the cross-sectional shape is designed according to actual needs; the top elevation of the first surge chamber section is based on the open-full flow tailwater tunnel of the inclined tunnel connected with the flat tunnel type in the actual project The elevation of the entrance of the middle connection section is set, and the adjustment guarantee parameters of the hydropower station under various working conditions meet the requirements of the specification and design.

When the open full flow tailrace tunnel of the inclined tunnel connected to the flat tunnel does not include the connecting section, the top elevation of the first surge chamber section is set according to the top elevation of the tailwater outlet flow channel of the actual project, and ensures that the regulation of the hydropower station under various working conditions Ensure parameters meet specifications and design requirements.

The cross-sectional shapes of the first surge chamber section and the second surge chamber section are rectangular, circular, elliptical or semi-elliptical.

Mingmanliu tail water system refers to a hydropower station tail water delivery system consisting of successively connected draft pipes, downstream surge chambers, Mingmanliu tailwater tunnels and tailwater outlets. When the hydropower station adopts the open-flow tailwater system, especially when some sections of the open-flow tailwater tunnel are flat tunnels, it is possible to break through the conventional equal-section surge chamber and adopt a variable-section surge chamber, that is, the surge chamber along the height Different cross-sectional areas and cross-sectional shapes are used in different directions in order to reduce the scale of the downstream surge chamber, which is beneficial to the stability of the underground cavern group, reduces the amount of cavern excavation and support works, and reduces the project cost.

Description of drawings

Figure 1 is a schematic diagram of the longitudinal section of the open flood tail water system of the inclined tunnel type;

Figure 2 is a schematic diagram of the longitudinal section of the open flood tailwater system of the type of inclined tunnel connected to the flat tunnel;

Figure 3 is a schematic structural diagram of a surge chamber with a gradual change in the downstream section, where Figure (a) is a cross-sectional view of the surge chamber along the water flow direction, Figure (b) is a cross-sectional view of the surge chamber A-A in Figure (a), and Figure (c) Figure (a) is a sectional view of surge chamber B-B, and figure (d) is a sectional view of surge chamber C-C in figure (a);

Figure 4 is a schematic diagram of the structure of the surge chamber with gradual changes on both sides, where Figure (a) is a cross-sectional view of the surge chamber along the water flow direction, Figure (b) is a D-D cross-sectional view of the surge chamber in Figure (a), and Figure (c) It is the E-E sectional view of the surge chamber in figure (a), and the figure (d) is the F-F sectional view of the surge chamber in figure (a);

Figure 5 is a schematic diagram of the structure of the surge chamber with a sudden change in the downstream side section, where Figure (a) is a cross-sectional view of the surge chamber along the flow direction, Figure (b) is a G-G cross-sectional view of the surge chamber in Figure (a), and Figure (c) It is the H-H sectional view of the surge chamber in the figure (a), and the figure (d) is the I-I sectional view of the surge chamber in the figure (a);

Figure 6 is a schematic diagram of the structure of the surge chamber with a sudden change in cross-section on both sides, where Figure (a) is a cross-sectional view of the surge chamber along the flow direction, Figure (b) is a cross-sectional view of the surge chamber J-J in Figure (a), and Figure (c) Figure (a) is a cross-sectional view of surge chamber K-K, and figure (d) is a cross-sectional view of surge chamber L-L in figure (a).

Among them, 1-underground powerhouse, 2-main transformer tunnel, 3-downstream surge chamber, 4-draft pipe inlet section, 5-draft pipe, 6-branch pipe section, 7-oblique section of Mingmanliu tailrace tunnel, 8- Connecting section, 9-flat section of the full-flow tailwater tunnel, 10-tailwater outlet, 11-downstream low water level, 12-downstream middle water level, 13-downstream high water level, 14-open-full flow interface, 15-pressure tail Length L1 of the channel section, 16-the length L2 of the non-pressure open flow section, 17-the length L of the open full flow tailrace tunnel, 18-the first surge chamber section, and 19-the second surge chamber section.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of the longitudinal section of the open flooded tail water system of the inclined tunnel type. The open flooded tail water system includes a draft pipe (5), a downstream surge chamber (3), and an open flooded tail water tunnel (7) connected in sequence. And the tailwater outlet (10), the Mingmanliu tailwater tunnel on the downstream side of the downstream surge chamber (3) is an inclined hole, that is, the oblique section (7) of the Mingmanliu tailwater tunnel. When the tailwater level rises from the downstream low water level (11) to the downstream middle water level (12) close to the tailwater outlet (10) cave top elevation, and then to the downstream high water level (13), the length of the pressure tailrace section L1 (15 ) gradually increases to the total length L of Mingmanliu tailrace tunnel. From formula (1) and formula (2), it can be known that the stable cross-sectional area of the downstream surge chamber increases from F1 to F2 and then to F, where F1 is the stable cross-sectional area of the downstream surge chamber corresponding to the downstream low water level (11), and F2 is The downstream medium water level (12) corresponds to the stable cross-sectional area of the downstream surge chamber, and F is the corresponding stable cross-sectional area of the downstream surge chamber at full flow. When calculating the stable cross-sectional area of the downstream surge chamber, the variables in formulas (1) to (2) are taken or calculated according to the actual situation.

For the inclined tunnel type open flood tailwater system shown in Fig. 1, in the calculation of the stable cross-sectional areas F1 and F2 of the surge chamber corresponding to the downstream low water level and downstream middle water level, the length of the pressure tailrace is the downstream surge chamber ( 3) The length of the clear and full flow tailrace tunnel between the open and full flow interface (14) corresponding to the corresponding tailwater level; in the calculation of the stable section area F of the surge chamber corresponding to the full flow, the length of the pressure tailrace channel is the open and full flow The total length L of the tailrace tunnel is the length of the open flood tailrace tunnel between the downstream surge chamber (3) and the tailwater outlet (10).

Figure 2 is a schematic diagram of the longitudinal section of the open flood tail water system of the type of inclined tunnel connected to the flat tunnel. and the tailwater outlet, the Mingmanliu tailrace tunnel includes the oblique section (7) of the Mingmanliu tailwater tunnel, the connecting section (8) and the flat section (9) of the Mingmanliu tailwater tunnel, and the oblique section of the Mingmanliu tailwater tunnel (7) The outlet is connected to the entrance of the flat section (9) of the Mingmanliu tail water tunnel through the connecting section (8), and the downstream surge chamber (3) is connected to the entrance of the oblique section (7) of the Mingmanliu tailwater tunnel, and the Mingmanliu tail The outlet of the flat section (9) of the water tunnel is connected with the tail water outlet and the tail water ditch. When the tailwater level rises from the downstream low water level (11) to the downstream middle water level (12) near the tailwater outlet (10) cave top elevation, and then to the downstream high water level (13), the length of the pressure tailrace is changed from L1 (15 ) gradually increases to the total length L of Mingmanliu tailrace tunnel. Use formulas (1) to (2) to calculate the stable cross-sectional area of the surge chamber F1 corresponding to the downstream low water level, the stable cross-sectional area F2 of the surge chamber corresponding to the downstream mid-water level, and the stable cross-sectional area F of the surge chamber corresponding to the full flow. Considering that the oblique section (7) of the Mingmanliu tailrace tunnel is relatively short, while the flat section (9) of the Mingmanliu tailrace tunnel is relatively long, the cross-sectional area of the downstream surge chamber is smaller than the flat section of the Mingmanliu tailrace tunnel ( 9) There is a sudden change in the elevation of the cave roof. In order to simplify the design and reduce the difficulty of construction, the downstream surge chamber is divided into two sections: the first surge chamber section and the second surge chamber section, taking the inlet elevation of the connecting section (8) as the boundary. Pressure room section. When there is no connection section, the top elevation of the first surge chamber section can be selected to be slightly lower than the elevation of the top of the flat section (9) of the Mingmanliu tailwater tunnel. Taking the stable cross-sectional area F2 of the downstream surge chamber corresponding to the middle water level of the inlet elevation of the connecting section (8) as the cross-sectional area of the first surge chamber section, when calculating the stable cross-sectional area F2 of the downstream surge chamber, take the upstream of the inlet of the connecting section (8) The length of the open flood tailrace tunnel on the side is the length of the pressure tailrace, and the other variables in formulas (1) to (2) are taken or calculated according to the actual situation.

The specific embodiment of the present invention is as follows:

According to the actual layout of the water delivery system of the hydropower station, formulas (1) and (2) are used to calculate the stable cross-sectional area of the surge chamber corresponding to the downstream low water level, downstream mid-water level, and full flow, respectively. For the open flood tail water system layout shown in Fig. 1 and Fig. 2, the section area of the surge chamber changes gradually along the height direction (see Fig. 3 and Fig. 4) and the section area of the surge chamber changes along the height direction ( See Figure 5 and Figure 6) for two types of surge chambers.

As shown in Figures 3-4, the first type of surge chamber, the cave body includes the first surge chamber section, the section area gradient section and the second surge chamber section along the height direction, and the section area gradient section is connected to the first surge chamber section. chamber section and the second surge chamber section. This surge chamber type is suitable for the open flooded tail water system shown in Figure 1. The cross-sectional area of the first surge chamber is the stable cross-sectional area of the surge chamber corresponding to the downstream low water level, and the cross-sectional area of the second surge chamber is full The stable cross-sectional area of the surge chamber corresponding to the flow time. The bottom elevation of the cross-sectional area gradient section can be selected to be slightly lower than the downstream low water level, and the top elevation can be selected to be slightly lower than the top elevation of the tailwater outlet. The cross-sectional shape of the first surge chamber section, the cross-sectional area gradient section and the second surge chamber section is selected according to the actual engineering needs. The cross-sectional shape should be selected as much as possible to facilitate construction, improve and reduce the stress concentration of the surrounding rock, and be beneficial to the surrounding rock of the cavern. stable shape. Figure 3 and Figure 4 respectively show the structure of the surge chamber with gradual change on the downstream side and gradual change on both sides.

See Figures 5-6, the second surge chamber type, the cave body includes the first surge chamber section and the second surge chamber section in sequence along the height direction, this surge chamber type is suitable for the Mingman shown in Figure 2 Tail water system. In the calculation of the section area of the first surge chamber section, the length of the Mingmanliu tailrace tunnel from the surge chamber to the exit of the oblique section (7) of the Mingmanliu tailrace tunnel is used as the length of the pressure tailrace to calculate the corresponding stable section of the surge chamber area, and take the stable cross-sectional area of the surge chamber as the cross-sectional area of the first surge chamber. The cross-sectional area of the second surge chamber section is the corresponding stable cross-sectional area F of the surge chamber at full flow, and the length of the pressure tailrace is the length of the open-full flow tailrace tunnel between the downstream surge chamber (3) and the tailwater outlet (10). . The initial value of the top elevation of the first surge chamber section is set by the inlet elevation of the connecting section (8) or the top elevation of the tailwater outlet flow channel, and then adjusted according to the needs of the calculation of the hydraulic transition process of the actual project to ensure that the hydropower station under various working conditions Adjustments ensure that parameters meet specification and design requirements.

When using a corridor-type surge chamber, the structure of the variable-section surge chamber in Figure 3-6 can be selected; when using a cylindrical or semi-cylindrical surge chamber, depending on the actual situation, the first section of the surge chamber cavity can be changed. The cross-sectional radius or cross-sectional shape (such as ellipse or semi-ellipse) of a surge chamber section meets the area requirements of the first surge chamber section, and connects with the second surge chamber section through a gradual change section and a sudden change. When applied to the tail water system with multiple machines, one hole and one chamber, the branch pipe section (6) can be arranged on the downstream side of the surge chamber (see Fig. 3 and Fig. 5) or at the bottom of the surge chamber (see Fig. 4 and Fig. 6) ).

The invention is not only applicable to the hydraulic unit with multiple machines, one hole and one chamber, but also applicable to the hydraulic unit with one machine, one hole and one chamber.

In the two layout types of open flood tail water system provided by the present invention, the calculation method of the stable cross-sectional area of the downstream surge chamber is the same as the stable cross-sectional area of the surge chamber in the conventional layout type of tail water tunnel with pressure, and attention should be paid to other parameters in the calculation Maintain the correct correspondence when taking values.

Claims (5)

1. Variable cross-section surge chamber, characterized in that: The cavity body of the surge chamber with variable cross-section includes the first surge chamber section, the cross-sectional area gradient section and the second surge chamber section from bottom to top in the height direction, and the cross-sectional area gradual change section connects the first surge chamber section and the second surge chamber section chamber section, wherein, the cross-sectional area of the first surge chamber section is the stable cross-sectional area of the surge chamber corresponding to the downstream low water level, and the cross-sectional area of the second surge chamber section is the stable cross-sectional area of the surge chamber corresponding to the full flow; the first surge chamber section The cross-sectional shape of the pressure chamber section and the second surge chamber section is the same or different, and the cross-sectional shape is designed according to actual needs; the bottom and top elevations of the cross-sectional area gradient section are set according to the downstream low water level of the actual project and the top elevation of the tail water outlet flow channel and ensure that the regulation parameters of the hydropower station under various working conditions meet the specifications and design requirements. 2. The variable-section surge chamber according to claim 1, characterized in that: The cross-sectional shapes of the first surge chamber section, the cross-sectional area transition section and the second surge chamber section are rectangle, circle, ellipse or semi-ellipse. 3. Variable cross-section surge chamber, characterized in that: The variable-section surge chamber body consists of the first surge chamber section and the second surge chamber section from bottom to top along the height direction. The cross-sectional area of the first surge chamber section is the The length of the flow path at the outlet of the inclined section is the stable cross-sectional area of the surge chamber calculated from the length of the pressure tailrace, and the cross-sectional area of the second surge chamber is the corresponding stable cross-sectional area of the surge chamber at full flow; the first surge chamber and the second surge chamber The cross-sectional shape of the second surge chamber section is the same or different, and the cross-sectional shape is designed according to actual needs; the top elevation of the first surge chamber section is based on the inlet elevation of the middle connection section of the Mingmanliu tailrace tunnel in the form of inclined tunnels connected to flat tunnels in actual projects To set, and ensure that the hydropower station regulation guarantee parameters meet the requirements of specifications and designs under various working conditions. 4. The variable-section surge chamber according to claim 3, characterized in that: When the open full flow tailrace tunnel of the inclined tunnel connected to the flat tunnel does not include the connecting section, the top elevation of the first surge chamber section is set according to the top elevation of the tailwater outlet flow channel of the actual project, and ensures that the regulation of the hydropower station under various working conditions Ensure parameters meet specifications and design requirements. 5. The variable-section surge chamber according to claim 3, characterized in that: The section shapes of the first surge chamber section and the second surge chamber section are rectangular, circular, elliptical or semi-elliptical.