CN110616689B

CN110616689B - Anti-corrosion inner flow orifice plate energy dissipater

Info

Publication number: CN110616689B
Application number: CN201910824097.0A
Authority: CN
Inventors: 白瑞迪; 罗晶; 许唯临; 李健薄; 周茂林; 翟俨伟
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2021-04-27
Anticipated expiration: 2039-09-02
Also published as: CN110616689A

Abstract

The invention provides a novel internal flow orifice plate energy dissipater capable of resisting cavitation erosion in a pressure flood discharge tunnel, which mainly comprises an orifice type orifice plate arranged in the flood discharge tunnel and a vortex elimination ring arranged on the upstream side of the orifice plate. The position of the flow separation area behind the orifice plate is controlled by high-speed water flow flowing through the pre-punched position, so that the energy dissipation efficiency of the orifice plate energy dissipater is ensured, and the cavitation erosion risk of the orifice plate energy dissipater with a smaller contraction ratio is reduced.

Description

Anti-corrosion inner flow orifice plate energy dissipater

Technical Field

The invention belongs to the technical field of flood discharge and energy dissipation in hydraulic engineering, and relates to a novel internal flow orifice plate energy dissipater capable of resisting cavitation erosion in a pressure flood discharge tunnel.

Background

Flood discharge energy dissipation is a key technical problem in dam construction, wherein flood discharge refers to the discharge of excess water quantity at the upstream of a dam, and energy dissipation refers to the elimination of potential energy at the upstream and the downstream of the dam. The reasonable selection of the type and energy dissipation mode of the flood discharge building has very important significance for the safe and efficient operation of the whole hydraulic engineering.

Generally, a high dam with more than one hundred meters has the characteristics of large single-width flow and large flood discharge power of a flood discharge building due to high water head, large flow and narrow river valley, so that combined flood discharge and energy dissipation modes such as dam body water discharge and flood discharge tunnel drainage are mostly adopted for discharging flood together. Energy dissipaters in the flood discharge tunnel mainly have three forms: shaft, orifice plate, and bore plug. The orifice plate energy dissipater utilizes water flow to generate sudden shrinkage and sudden expansion before and after passing through the orifice plate under the condition of pressure driving, so that a flow line is forced to be sharply bent, and the purpose of eliminating braking energy is achieved.

Although the traditional orifice plate internal flow energy dissipater has the characteristics of strong flow capacity, good energy dissipation effect (the energy dissipation rate can reach 40% -60%), economy and practicality, and is applied to practical engineering. However, due to the sharp bend of the water flow line passing through the orifice plate, the water flow is separated from the main flow after the orifice plate, so that cavitation phenomenon often occurs in the area. This cavitation phenomenon is a potential threat to the self-safe operation of energy-dissipating buildings (cavitation occurs in the side walls of buildings to produce cavitation erosion).

Therefore, how to exert the energy dissipation effect of the orifice plate energy dissipater to the maximum extent and ensure the self safety of the energy dissipation facility becomes a difficult point for research on flood discharge and energy dissipation under pressure.

Disclosure of Invention

The invention aims to solve the problems of the existing energy dissipater in the orifice plate in the pressure relief flood tunnel, and provides a corrosion-resistant inner orifice plate energy dissipater which can reduce or even eliminate the potential safety hazard of self operation of an energy dissipation building caused by cavitation while ensuring the energy dissipation efficiency.

The invention has the main concept that holes are pre-punched on the traditional hole type pore plate, and the energy of water flow flowing through the pre-punched position of the pore plate is utilized to drive a cavitation generation area, in which a main flow and a backflow area are strongly sheared mutually, behind a downstream pore plate to be far away from the inner wall of a flood discharge hole behind the pore plate, so that the energy dissipation efficiency of a pore plate energy dissipater can be ensured, and the potential cavitation risk of the pore plate energy dissipater can be avoided. The invention is especially suitable for the energy dissipater of the hole type orifice plate with smaller contraction ratio.

The invention provides a corrosion-resistant inner flow orifice plate energy dissipater, which comprises an orifice type orifice plate arranged on the section surface of a flood discharge tunnel and an eddy eliminating ring arranged on the incident flow surface of the orifice plate, wherein the cross section of the eddy eliminating ring is in the shape of a right-angled triangle, and a plane corresponding to the hypotenuse of the right-angled triangle forms a contraction ring surface along the water flow direction.

The contraction ring surface means that the overflowing surface of the vortex elimination ring is an inverted trumpet-shaped curved surface gradually shrunk along the water flow direction, so that the water flow is smoothly transited to the hole of the pore plate.

Furthermore, a central overflowing hole is formed in the center of the orifice plate, and small holes are uniformly formed in the orifice plate around the overflowing hole. Preferably, the number of the small holes is four, and the small holes are uniformly and symmetrically distributed on the upper side, the lower side, the left side and the right side of the overflowing hole.

Further, the diameter of the inner edge of the vortex elimination ring meets the requirement that small holes are arranged on the pore plate in the inner edge range; furthermore, the inner edge of the vortex elimination ring is flush with the outer edge of the small hole of the pore plate, and the outer edge of the vortex elimination ring is flush with the outer edge of the hole type pore plate.

The vortex elimination ring can enable water flow to smoothly transit from the upstream of the pore plate to the central hole of the pore plate, and meanwhile, the structural strength of the pore plate can be improved.

Furthermore, the overflowing wall surface of the overflowing hole is an inclined surface, and a horn-shaped overflowing hole expanding outwards along the water flow direction is formed.

Preferably, the flow aperture wall surface is inclined at an angle of 30 °.

Furthermore, the axes of the small holes of the hole type hole plate are parallel to the axis of the flood discharge hole, and the circle center of the central overflowing hole is positioned on the axis of the flood discharge hole.

Further, the aperture of the 4 small holes is D '═ D)/12, wherein D is the diameter of the flood discharge hole, D is the aperture of the central overflowing hole, and D' is the aperture of the small hole.

Furthermore, the ratio eta of the aperture D of the hole type hole plate to the diameter D of the flood discharge hole is 0.3-0.5.

Furthermore, the thickness t of the hole type hole plate is 0.062-0.174D.

Furthermore, the dimensionless parameter 2b/(D-D) of the size of the vortex elimination ring is 0.55-0.62, b is the vertical distance between the inner edge and the outer edge of the vortex elimination ring, D is the diameter of the flood discharge hole, D is the aperture of the central overflowing hole, and D' is the aperture of the small hole.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the energy dissipater, the jet flow flowing through the small holes is used for impacting the position of the downstream flow separation area of the orifice plate, the water flow state of the area is changed, the cavitation generation area, in which the main flow and the backflow area are strongly sheared mutually, behind the downstream orifice plate is driven to be far away from the inner wall of the flood discharge hole behind the orifice plate, the low-pressure distribution state of the local water flow is effectively improved, and therefore the initiation and development of cavitation erosion are restrained. Not only ensures the energy dissipation efficiency, but also avoids the potential cavitation risk in the flood discharge tunnel, thereby greatly reducing the operation cost.

2. The invention has simple structure and low construction difficulty, the eddy eliminating ring can enable water flow to smoothly transit from the upstream of the pore plate to the central hole of the pore plate, and meanwhile, the structural strength of the pore plate can be enhanced.

Drawings

Figure 1 is a combined schematic diagram of a structure diagram of the novel corrosion-resistant inner flow orifice plate energy dissipater and a flood discharge tunnel.

Fig. 2 is a sectional view a-a of fig. 1.

Figure 3 is a pressure field diagram of a numerical simulation of an orifice plate dissipater.

Fig. 4 is a pressure field diagram of the numerical simulation of the energy dissipater of the novel anti-corrosion inner flow orifice plate.

Wherein, 1 flood discharging hole, 2 vortex eliminating ring and 3 hole type pore plates

Detailed Description

The present invention is further illustrated by the following specific embodiments.

Examples

As shown in fig. 1-2, the present embodiment provides a novel anti-corrosion inner flow orifice plate energy dissipater, which includes an orifice type orifice plate 3 disposed on a section surface of a flood discharge tunnel 1 and a vortex elimination ring 2 disposed on an incident surface of the orifice plate, wherein a cross-sectional shape of the vortex elimination ring along an axis of the flood discharge tunnel is a right triangle, and a surface corresponding to a hypotenuse of the right triangle forms a contracted ring surface along a water flow direction. The center of the pore plate is provided with a central overflowing hole, four small holes are uniformly arranged on the pore plate around the central overflowing hole, and the small holes are uniformly and symmetrically distributed on the upper side, the lower side, the left side and the right side of the central overflowing hole. The inner edge of the vortex elimination ring is flush with the outer edge of the small hole of the pore plate, and the outer edge of the vortex elimination ring is flush with the outer edge of the hole type pore plate. The overflowing wall surface of the central overflowing hole is an inclined surface, and a horn-shaped overflowing hole expanding outwards along the water flow direction is formed. The axis of the small hole of the hole type hole plate is parallel to the axis of the flood discharge hole, and the circle center of the central overflowing hole is positioned on the axis of the flood discharge hole.

The following optimizations were performed in this example: the hole type pore plate is provided with 4 small holes with the aperture of D' ═ D/12 in the pore plate; the aperture ratio eta of the central overflowing hole aperture D of the hole type pore plate to the hole diameter D is D/D is 0.4, and the top of the pore plate adopts a 30-degree chamfer angle; the thickness t of the hole type pore plate is 0.15D; and the dimensionless parameter b of the size of the deswirler ring is 0.14D.

A pressure field diagram 3 of the numerical simulation of the existing conventional orifice plate energy dissipater and a pressure field diagram 4 of the numerical simulation of the novel corrosion-resistant inner flow orifice plate energy dissipater in the embodiment are obtained through numerical simulation (by adopting a k-epsilon turbulence model of RNG and a finite volume discretization method, and according to a conventional method in the field). From figure 3, it can be seen that the low pressure area of the plate energy dissipater is close to the side wall of the flood discharge tunnel and has a large range, and the lowest pressure value is-710.5 kPa, while the low pressure area is obviously far away from the side wall of the flood discharge tunnel and has a small range compared with figure 3, and meanwhile, the lowest pressure value is-170.4 kPa, so that the risk of cavitation erosion is greatly reduced, and the safety and reliability of the orifice plate with a small contraction ratio are further improved.

It will be appreciated by those of ordinary skill in the art that the examples provided herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited examples and embodiments. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

Claims

1. The anti-corrosion type inner flow pore plate energy dissipater is characterized by comprising a pore type pore plate arranged on the section surface of a flood discharge tunnel and an eddy eliminating ring arranged on the incident flow surface of the pore plate, wherein the cross section of the eddy eliminating ring is in the shape of a right-angled triangle, the surface corresponding to the hypotenuse of the right-angled triangle forms a contraction ring surface along the water flow direction, the center of the pore plate is provided with a central overflowing hole, the pore plate around the central overflowing hole is uniformly provided with small holes, and the number of the small holes is four, and the small holes are uniformly and symmetrically distributed on the upper side, the lower side, the left; the diameter of the inner edge of the vortex elimination ring can meet the requirement that the small hole is arranged on the pore plate within the inner edge range, the inner edge of the vortex elimination ring is flush with the outer edge of the small hole of the pore plate, and the outer edge of the vortex elimination ring is flush with the outer edge of the pore plate.

2. The dissipater as claimed in claim 1, wherein the flow wall of said central overflow aperture is inclined to form a flared overflow aperture extending outwardly in the direction of flow.

3. An dissipater as claimed in claim 1, wherein the axes of the apertures of the apertured sheet are parallel to the axis of the tunnel, and the centre of the central overflow aperture is located on the axis of the tunnel.

4. An dissipater as claimed in claim 1, wherein the aperture of the 4 holes is D '═ (D-D)/12 where D is the diameter of the spillway tunnel, D is the aperture of the central overflow hole and D' is the aperture of the hole.

5. The dissipater according to claim 1, wherein the ratio η D/D of the diameter D of the central overflowing hole of the perforated plate to the diameter D of the flood discharge hole is 0.3-0.5.

6. An energy dissipater as claimed in any one of claims 1 to 5, wherein said apertured plate has a thickness t of 0.062 to 0.174D.

7. An energy dissipater according to any one of claims 1 to 5, wherein the dimensionless parameter 2b/(D-D) of the size of the vortex breaker is 0.55 to 0.62, b is the vertical distance of the inner edge of the vortex breaker from the outer edge, D is the diameter of the spillway hole, D is the aperture of the central overflow hole, and D' is the aperture of the small hole.