CN109441691B - A draft tube with a rectifier plate Francis turbine - Google Patents

Abstract

The invention discloses a mixed-flow water turbine with a tail water pipe and a rectifying plate, wherein the flow passage region of the mixed-flow water turbine comprises a volute (1), a guide vane region (2), a rotating wheel (4) and tail water with the rectifying plate (8) which are sequentially connectedA pipe (7), wherein the diffusion angle of the straight conical section of the tail water pipe (7) is β₁6, be equipped with trapezoidal cross section cowling panel (8) of taking the circular arc side in the draft tube, each cowling panel (8) is arranged around pasting draft tube (7) inner wall circumference in the hydraulic turbine axis, and cowling panel (8) are close to axle head cone angle β₂The thickness control direction of the rectifying plate (8) is β degrees when the angle is 9 degrees₃The number of the rectifying plates (8) is 4-6. The invention improves the unsteady flow field of the rotating wheel to improve the running performance of the water turbine, and aims to improve the energy recovery coefficient of the draft tube and improve or eliminate the vortex phenomenon in the draft tube under the non-design working condition.

Description

A draft tube with a rectifier plate Francis turbine

technical field

The invention belongs to the technical field of hydraulic machinery, and in particular relates to a Francis turbine with a rectifier plate in a draft tube.

Background technique

As a renewable energy source, hydropower has less impact on the environment. In addition to providing cheap electricity, it also has the advantages of controlling flooding, providing irrigation water, and improving river navigation. Francis turbine is the standard and representative model for the research, design and manufacturing level of hydraulic turbines in the current hydropower generation system. While developing towards the goal of high efficiency and large capacity, it also affects the reliability, stability and safety of the whole machine. put forward higher requirements.

Chinese patent application 201210209725.2 discloses a turbine draft tube vortex generator, which is used to generate a series of small vortices to neutralize the vortex of the turbine draft tube itself. The structure is simple and the installation is flexible, but the device requires water to flow around to generate The vortex, and the neutralization of the new vortex and the draft tube's own vortex is an extremely complex process, which will produce secondary effect losses. Chinese Patent Application No. 201410243350.0 discloses a draft tube for a water turbine. In the channel of the draft tube, there are rectifier tubes with openings at the front and rear ends to suppress the generation and influence of the eccentric vortex. However, most research results show that the draft tube vortex The first position of the belt is close to the outlet of the runner. The position of the device can only affect the vortex at the end of the vortex belt, and the device needs to be connected with a fixed rod and the wall of the draft tube. On the one hand, the addition of additional components increases the complexity of the structure, on the other hand On the one hand, the connecting rod in the flow field will also affect the internal flow of the draft tube. For the second connection method, the connecting rod is fixed on the ground, which increases the sealing work between the internal flow and the outside world. Chinese patent application 201611243124.8 discloses a dual-turbine turbine for cooling towers with spherical helical blades. The spiral blades are arranged in the draft tube to increase the output as the runner rotates at the same speed, but its structure is complex and difficult to process. The cost is high, the additional runner has higher performance requirements for external structural components such as shafts, the additional water outlet pipe increases the space required for the unit, and the direction of the outflow speed of the runner blade hits the spiral blade, causing the loss of the flow section to increase. The instability of the inner flow field is enhanced and so on.

To sum up, on the basis of improving the flow characteristics in the turbine to improve the operation performance of the turbine, it is necessary to propose an effective method that can improve the energy recovery coefficient of the draft tube of the turbine and improve the stability of the internal flow field, aiming at the shortcomings of the existing technology. , Simple handling countermeasures.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies existing in the prior art, and to provide a draft tube with a rectifier plate Francis turbine, which can solve the problem of eddy current in the flow field in the draft tube of the turbine on the basis of realizing the efficient conversion of water flow energy, thereby Improve the operating stability of the unit.

The present invention adopts following technical scheme to realize:

A draft tube with a fairing plate Francis turbine, the flow area of the turbine includes a volute, a guide vane area, a runner and a draft tube with a fairing plate connected in sequence; wherein,

The divergence angle of the straight cone section of the draft tube is β ₁ =6°. The draft tube is provided with a trapezoidal section fairing plate with a circular arc side. Each fairing plate is circumferentially arranged around the turbine axis and attached to the inner wall of the draft tube, and the fairing plate is close to the shaft end cone. The angle β ₂ =9°, the thickness control direction of the rectifier plates is β ₃ =10°, and the number of rectifier plates is 4-6.

The further improvement of the present invention is that the cross section of the rectifying plate is a trapezoid, and the L1 is a busbar that rotates β3 around the turbine axis to obtain the L2 side, and the sweeping range is the thickness _of the rectifying plate; the L3 side of the rectifying plate is fitted with the draft tube, close to the turbine The L4 type line of the trapezoidal side on the axis side is y=3.335x+31.72, and the L5 side is flush with the draft tube outlet.

A further improvement of the present invention lies in that the volute is a wrap-angle volute, its section is ellipse, and the ratio of the length of each ellipse is equal to 1.618, and the change trend equation of the ellipse cross-sectional area of the volute around the circumferential direction is: y=-0.041x+0.239 , the wrap angle of the volute is 315°～335°.

A further improvement of the present invention lies in that a number of curvature vanes are evenly distributed in the circumferential direction in the guide vane area, the number of guide vanes in a single row is 16, the ratio of the diameter of the guide vane distribution circle D _V to the diameter of the runner inlet D _I is 2.1916, and the throat of the guide vane is 2.1916. The ratio of the part diameter D _T to the runner inlet diameter D _I is 0.0825.

A further improvement of the present invention is that the ratio of the runner inlet height B3 to the runner inlet diameter D _I is 0.096, and the ratio of the runner outlet diameter D _P to the runner inlet diameter D _I is 0.513.

A further improvement of the present invention is that the runner blades are composed of several long blades and short blades at intervals, and the long blades and short blades of the runner are arranged at a 1:1 interval, the outflow diameter ratio of the long blades and the short blades is 0.336, and the long blades Wrap angle α=65°～85°.

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

First, the draft tube with fairing plate Francis turbine proposed by the present invention has stable operation, high conversion rate of water flow energy, and the arrangement of long and short blades can reduce the design size of the runner, thereby reducing the overall size of the turbine and reducing the cost. .

Second, the trapezoidal fairing plate structure in the draft tube proposed by the present invention improves the energy recovery coefficient of the draft tube, improves or even eliminates the eddy current phenomenon in the draft tube under non-design conditions, thereby reducing the loss of internal flow, and on the one hand, improving the hydraulic turbine. On the other hand, it improves the operation stability of the entire hydroelectric generating set and prolongs the life of the unit.

Third, the trapezoidal rectifying plate structure in the draft tube proposed by the present invention is universal, especially for various types of pumps, turbines and reversible pump-turbine units with draft tubes, the eddy current structure is separated and rectified at the outlet of the runner. It has a certain reference value for the stability research of various hydraulic machinery.

Description of drawings

FIG. 1 is a schematic structural diagram of a Francis turbine with a draft tube with a rectifier plate proposed by the present invention.

Figure 2 is a sectional view of a long blade of a runner.

Figure 3 is a front view of the long and short blades of the runner.

FIG. 4 is a schematic diagram of a guide vane profile line of a negative curvature blade profile.

Figure 5 is a top view of the draft tube.

Figure 6 is a front view of the draft tube.

Description of reference numerals: 1-volute, 2-guide vane field, 3-guide vane, 4-runner, 5-short vane, 6-long vane, 7-draught tube, 8-straightening plate.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

As shown in FIG. 1 , a draft tube with a rectifier plate Francis turbine provided by the present invention includes a volute 1, a guide vane region 2, a runner 4 and a draft tube 7 connected in sequence, and the cross section of the volute 1 is an ellipse The outlet annulus is connected with the inlet annulus of the guide vane domain 2; the guide vane domain 2 includes 16 negative-curvature vane-shaped guide vanes 3 evenly distributed in the circumferential direction, and the water flow enters the runner 4 through the throat of the guide vane 3, and the runner 4 is composed of 9 short blades 5 and 9 long blades 6 at intervals. The water flow works on the runner 4, so that the runner drives the shaft connected to the motor to rotate, and realizes the conversion of water flow energy into mechanical energy; The draft tube 7 flows out, the inner wall of the draft tube 7 is attached with a fairing plate 8, and the trapezoidal fairing plate 8 is arranged to prevent the formation of the vortex at the outlet of the runner, thereby improving the flow state in the draft tube and improving the energy recovery coefficient of the draft tube at the same time. , which is beneficial to improve the overall operational stability of the turbine.

The realization principle of the present invention is:

A draft tube with fairing plate Francis turbine proposed by the present invention, in order to improve the operation stability on the basis of improving the operation efficiency of the turbine, the runner 4 is provided with long blades 6 and short blades 5 arranged at intervals to improve the internal flow of the runner. Ingenious use of conical blades evenly distributed on the inner wall of the draft tube 7 in order to separate the circumferential speed of the runner outflow and organize the formation of eddy currents, and the conical blades have the function of guiding and rectifying, thus It solves the secondary effect of the internal flow of the draft tube caused by improving the characteristics of the runner flow field, and greatly improves the performance of the turbine.

Example

The present invention provides a further preferred solution for a draft tube with a rectifying plate Francis turbine: the diffusion angle of the straight cone section of the draft tube is β ₁ =6°, the draft tube is provided with a trapezoidal section rectifying plate with arc sides, and each The plates are arranged circumferentially around the axis of the turbine and are attached to the inner wall of the draft tube. The cone angle of the rectifier plate close to the shaft end is β ₂ =9°, the thickness control direction of the rectifier plate is β ₃ =10°, and the number of rectifier plates is 4.

The cross _- section of the rectifier plate is trapezoid, and the L2 side is obtained by rotating β3 around the axis with L1 as the busbar, and the sweep range is the thickness of the rectifier plate; the L3 side of the rectifier plate is attached to the draft tube, and the L4 type line equation of the trapezoidal edge on the side close to the turbine axis is: y=3.335x+31.72, the L5 side is flush with the draft tube outlet.

The section of the wrap angle volute is elliptical, and the length ratio of each ellipse is equal to 1.618. The trend equation of the oval cross section area of the volute around the circumferential direction is: y=-0.041x+0.239, and its wrap angle is 318°.

The long blade 6 of the runner is a three-dimensional twisted surface, which is divided into four sections in the direction of blade height according to the bone line, and the dotted line shows the profile of the blade of each section.

The short blade 5 is the same as the long blade 6, the long and short blades of the runner are arranged at a 1:1 interval, and the outflow diameter ratio of the long and short blades is 0.336, and the long blade wrap angle α=70°.

There are 16 guide vanes in a single row of negative curvature blade shape uniformly distributed in the circumferential direction. The ratio of the distribution circle diameter D _V of the guide vane 3 to the runner inlet diameter D _I is 2.1916, and the ratio of the throat diameter D _T of the guide vane 3 to the runner inlet diameter D _I is 0.0825.

The descriptions not involved in the specific implementation of the present invention belong to the known technology in the art, and can be implemented with reference to the known technology. The present invention has obtained satisfactory application effects through repeated tests and verification, and the idea of a draft tube with a fairing plate structure described in the embodiment is applicable to various hydraulic machines with draft tubes.

The above specific embodiments and examples are specific support for the technical idea of a draft tube with rectifier plate Francis turbine proposed by the present invention, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or equivalent modifications made on the basis of the technical solution belong to the protection scope of the technical solution of the present invention.

Claims (3)

1. A mixed-flow water turbine with a tail water pipe and a rectifying plate is characterized in that the flow area of the mixed-flow water turbine comprises a volute (1), a guide vane area (2), a rotating wheel (4) and a tail water pipe (7) with a rectifying plate (8) which are connected in sequence; wherein,

the diffusion angle of the straight conical section of the draft tube (7) is β₁6, be equipped with trapezoidal cross section cowling panel (8) of taking the circular arc side in the draft tube, each cowling panel (8) is arranged around pasting draft tube (7) inner wall circumference in the hydraulic turbine axis, and cowling panel (8) are close to axle head cone angle β₂The thickness control direction of the rectifying plate (8) is β degrees when the angle is 9 degrees₃The number of the rectifying plates (8) is 4-6;

the cross section of the rectifying plate (8) is trapezoidal, and the rectifying plate rotates β around the axis of the water turbine by taking L1 as a generatrix₃The L side is obtained, the swept range is the thickness of the rectifying plate (8), the side of the rectifying plate (8) L is attached to the draft tube (7), the line equation of the trapezoidal side L4 close to the axis side of the water turbine is that y is 3.335x +31.72, and the side L is flush with the outlet of the draft tube;

the volute (1) is an angle wrapping type volute, the cross section of the volute is elliptical, the length ratio of each ellipse is equal to 1.618, and the variation trend equation of the elliptical cross section area of the volute around the circumferential direction is as follows: y is-0.041 x +0.239, and the wrap angle of the volute (1) is 315-335 degrees;

the runner blade is composed of a plurality of long blades (6) and short blades (5) at intervals, the long blades (6) and the short blades (5) of the runner (4) are arranged at intervals of 1: 1, the outflow diameter ratio of the long blades (6) to the short blades (5) is 0.336, and the wrap angle α of the long blades (6) is 65-85 degrees.

2. The francis turbine of claim 1, wherein a plurality of negative curvature blade type guide vanes (3) are evenly distributed on the inner circumference of the guide vane area (2), the number of the single-row guide vanes (3) is 16, and the diameter D of the distribution circle of the guide vanes (3) is_VDiameter D of inlet of rotating wheel_IRatio of 2.1916, diameter D of throat of guide vane (3)_TDiameter D of inlet of rotating wheel_IThe ratio was 0.0825.

3. A francis turbine with a tailrace and a cowling panel in accordance with claim 1, wherein the runner (4) inlet height B3 and runner inlet diameter D_IThe ratio is 0.096, and the diameter D of the outlet of the rotating wheel_PDiameter D of inlet of rotating wheel_IThe ratio is 0.513.

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