Optimization method for S characteristic of pump turbine

Abstract

The invention relates to an optimization method of S characteristics, in particular to an optimization method of S characteristics of a pump turbine. The invention aims to solve the problems of complex S characteristic optimization process and long consumed time in the prior art. During S characteristic optimization, an S characteristic curve of a turbine runner is obtained firstly, then N turbulent flow rods are installed in a vaneless area between a movable guide vane and the runner according to the sudden change of the S characteristic curve, and the turbulent flow rods are arranged on a reference circle with the diameter being Dr. When fluid flows through the turbulent flow rods, water flow at the inlet of the rotating wheel collides with the turbulent flow rods, wake flow formed by collision extrudes inlet backflow vortexes, the shapes of the inlet backflow vortexes are lengthened, the inlet backflow vortexes extend towards the center of the rotating wheel, the size occupied by the inlet backflow vortexes at the inlet of the rotating wheel is reduced, and the inlet backflow vortexes can be improved or restrained. And the flow capacity of the runner is improved, so that the S characteristic of the pump turbine is further improved. The invention belongs to the technical field of water turbine S characteristic optimization.

Description

Technical Field

[0001] The invention relates to an S characteristic optimization method, in particular to an S characteristic optimization method for a water pump turbine, and belongs to the technical field of turbine S characteristic optimization. Background Art

[0002] When the pump-turbine is running at a small flow rate under power generation conditions, the full characteristic curve is S-shaped, which is called the S characteristic of the pump-turbine, that is, the full characteristic curve has an obvious mutation phenomenon in the first quadrant.

[0003] Research and engineering practice have shown that the S characteristic is closely related to the poor flow state at the runner inlet (such as the inlet recirculation vortex). As the water flow further decreases, the volume occupied by the poor flow state at the runner inlet increases, which reduces the flow capacity of the runner, leading to strong vibration and noise in the unit. Therefore, the mutation zone of the S characteristic poses a threat to the operating stability of the unit.

[0004] During the hydraulic design stage, the S characteristic should be eliminated by optimizing the geometric parameters of the runner and channel. However, the optimization process is highly dependent on the designer's experience and takes a long time.

[0005] In summary, how to propose a new optimization method for the above-mentioned technical problems has become an urgent problem to be solved by technicians in this field. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for optimizing the S characteristics of a pump turbine.

[0007] The technical solution of the present invention is: a method for optimizing the S characteristics of a pump turbine, which is specifically carried out in the following steps:

[0008] Step 1, obtaining the S characteristic curve of the turbine runner;

[0009] Step 2: According to the size of the sudden change of the S characteristic curve, N spoiler rods are installed in the bladeless area between the movable guide vane and the runner;

[0010] The spoiler rod is arranged on a pitch circle with a diameter of Dr. The value range of Dr must satisfy D 1 <Dr<D 3 ;

[0011] Among them, D 1 D is the outer diameter of the crown on the runner; 3 D is the diameter of the inscribed circle at the tail of each movable guide vane when the movable guide vane opening is maximum. 1 , Dr and D 3 For concentric circles.

[0012] Further, step 2 includes a first movable guide vane and a second movable guide vane, the first movable guide vane is the movable guide vane closest to the volute tongue, the second movable guide vane is arranged adjacent to the first movable guide vane, and the volute tongue, the first movable guide vane and the second movable guide vane are arranged in sequence clockwise;

[0013] When the opening of each movable guide vane is the largest, the line connecting the tail of the first movable guide vane and the center of the dividing circle is L 1 , the line connecting the tail of the second movable guide vane and the center of the dividing circle is L 2 ;

[0014] When N=1, the spoiler rod is arranged at L 1 With L 2 The angle between

[0015] When N>1, the spoiler rods are distributed at equal angles in the circumferential direction of the pitch circle, and the position of one of the spoiler rods is the same as when N=1.

[0016] Compared with the prior art, the present invention has the following effects:

[0017] The present invention provides a spoiler bar 6 in the bladeless area to actively interfere with the water flow, namely:

[0018] After entering from the volute passage 1, the fluid flows through the fixed guide vane 2 and the movable guide vane 3 in sequence. When the fluid flows through the spoiler rod 6, the water flow at the inlet of the runner 4 collides with the spoiler rod 6. The wake flow formed by the collision squeezes the inlet return vortex, so that the shape of the inlet return vortex is elongated and extends toward the center of the runner 4, and the volume occupied by the inlet return vortex at the runner inlet is reduced, which can improve or suppress the inlet return vortex and enhance the flow capacity of the runner 4, thereby further improving the S characteristics of the pump turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a top view of the arrangement position of the spoiler rod 6 of the present invention;

[0020] Figure 2 yes Figure 1 A partial enlarged view of point Ⅰ in the middle;

[0021] Figure 3 It is a schematic diagram of the present invention in which a spoiler rod 6 is provided;

[0022] Figure 4 It is a schematic diagram of the present invention in which a plurality of spoiler rods 6 are provided;

[0023] Figure 5 Schematic diagram of the inlet return vortex at the inlet of the runner 4 when the spoiler rod 6 is not provided in the bladeless area, and the blue part in the figure represents the inlet return vortex;

[0024] Figure 6It is a schematic diagram of the inlet recirculation vortex at the inlet of the runner 4 when the spoiler rod 6 is provided in the bladeless area. The blue part in the figure represents the inlet recirculation vortex.

[0025] In the figure: 1, volute passage; 2, fixed guide vane; 3, movable guide vane; 4, runner; 5, tailwater pipe; 6, spoiler rod; 7, volute tongue. DETAILED DESCRIPTION

[0026] In order to make the purpose, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] Specific implementation method 1: Combination Figures 1 to 3 The present embodiment is described. The present embodiment is a method for optimizing the S characteristics of a pump turbine, which is specifically performed in the following steps:

[0028] Step 1, obtaining the S characteristic curve of the turbine runner;

[0029] Step 2: According to the size of the sudden change of the S characteristic curve, N spoiler rods 6 are installed in the bladeless area between the movable guide vane 3 and the runner 4;

[0030] The spoiler rod 6 is arranged on a pitch circle with a diameter of Dr. The value range of Dr must satisfy D 1 <Dr<D 3 ;

[0031] Among them, D 1 D is the outer diameter of the crown on the runner 4; 3 D is the diameter of the inscribed circle at the tail of each movable guide vane 3 when the movable guide vane 3 is opened to the maximum. 1 , Dr and D 3 For concentric circles.

[0032] Further, step 2 includes a first movable guide vane and a second movable guide vane, the first movable guide vane is the movable guide vane 3 closest to the volute tongue 7, the second movable guide vane is arranged adjacent to the first movable guide vane, and the volute tongue 7, the first movable guide vane and the second movable guide vane are arranged in sequence clockwise;

[0033] When the opening of each movable guide vane 3 is maximum, the line connecting the tail of the first movable guide vane and the center of the dividing circle is L 1 , the line connecting the tail of the second movable guide vane and the center of the dividing circle is L 2 ;

[0034] When N=1, the spoiler rod 6 is arranged at L 1 With L 2 The angle between

[0035] When N>1, the spoiler rods 6 are distributed at equal angles in the circumferential direction of the pitch circle, and the position of one of the spoiler rods 6 is the same as when N=1.

[0036] In step one of the present embodiment, the full characteristic curve is obtained by fitting the steady-state test data or performing numerical simulation. With this arrangement, the data obtained by fitting the steady-state test data are relatively stable and can more accurately reflect the true characteristics of the system with high accuracy. The method of obtaining the full characteristic curve by numerical simulation has the advantages of high flexibility, dynamic characteristic capture and low cost.

[0037] Specific implementation method 2: Combination Figures 2 to 3 To illustrate this embodiment, in step 2 of this embodiment, the cross section of the spoiler rod 6 is a circle or a regular polygon. Other components and connection relationships are the same as those of the specific embodiment 1.

[0038] Specific implementation method three: Combination Figures 2 to 3 In this embodiment, the radius of the spoiler rod 6 in step 2 of this embodiment is d, and the value range of d is 3 mm. <d<[(D 3 -D 1 ) / 2]mm.

[0039] Among them, D 1 D is the outer diameter of the crown on the runner 4. 3 is the diameter of the inscribed circle at the tail of each movable guide vane 3 when the movable guide vane 3 is opened to the maximum, and D 1 and D 3 For concentric circles.

[0040] The other components and connection relationships are the same as those in the first or second specific implementation.

[0041] Specific implementation method four: Combination Figures 2 to 3 In this embodiment, the side length of the spoiler rod 6 in step 2 of this embodiment is d, and the value range of d is 3 mm. <d<[(D 3 -D 1 ) / 2]mm.

[0042] Among them, D 1 D is the outer diameter of the crown on the runner 4. 3 is the diameter of the inscribed circle at the tail of each movable guide vane 3 when the movable guide vane 3 is opened to the maximum, and D 1 and D 3 For concentric circles.

[0043] The other components and connection relationships are the same as those of the first, second or third specific implementation modes.

[0044] How it works

[0045] like Figure 5As shown, when the pump turbine is operating in the S characteristic zone, due to the small water flow in the volute channel 1, there is a deviation between the flow angle of the water flow and the blade placement angle of the runner 4, which leads to the appearance of an inlet return vortex at the inlet of the runner 4. At the same time, as the water flow further decreases, the volume occupied by the inlet return vortex at the inlet of the runner 4 increases, causing the flow capacity of the runner to decrease.

[0046] like Figure 6 As shown, the present invention sets a spoiler bar 6 in the bladeless area to actively interfere with the water flow, that is:

[0047] After entering from the volute passage 1, the fluid flows through the fixed guide vane 2 and the movable guide vane 3 in sequence. When the fluid flows through the spoiler rod 6, the water flow at the inlet of the runner 4 collides with the spoiler rod 6. The wake flow formed by the collision squeezes the inlet return vortex, so that the shape of the inlet return vortex is elongated and extends toward the center of the runner 4, so that the volume occupied by the inlet return vortex at the runner inlet is reduced, which can improve or suppress the inlet return vortex and enhance the flow capacity of the runner 4, thereby further improving the S characteristics of the pump turbine. After completing the work, the fluid flows out along the tailwater pipe 5.

[0048] The present invention has been disclosed as above in the form of a preferred embodiment, but it is not intended to limit the present invention. Any simple modification, equivalent changes and modifications made to the above implementation cases by any professional and technical personnel who do not deviate from the content of the technical solution of the present invention and based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the S characteristics of a pump turbine, characterized in that: The method is specifically carried out in the following steps: Step 1, obtaining the S characteristic curve of the turbine runner; Step 2: According to the size of the sudden change of the S characteristic curve, N spoiler rods (6) are installed in the bladeless area between the movable guide vane (3) and the runner (4); The spoiler rod (6) is arranged on a pitch circle with a diameter of Dr. The value range of Dr must satisfy D1 <Dr<D3; Wherein, D1 is the outer diameter of the crown of the impeller (4); D3 is the diameter of the inscribed circle of the tail of each movable guide vane (3) when the movable guide vane (3) is at its maximum opening; D1, Dr and D3 are concentric circles.

2. The method for optimizing the S characteristics of a pump turbine according to claim 1, characterized in that: The second step includes a first movable guide vane and a second movable guide vane, wherein the first movable guide vane is the movable guide vane (3) closest to the volute tongue (7), and the second movable guide vane is arranged adjacent to the first movable guide vane, and the volute tongue (7), the first movable guide vane and the second movable guide vane are arranged in sequence clockwise; When the opening of each movable guide vane (3) is maximum, the line connecting the tail of the first movable guide vane and the center of the pitch circle is L1, and the line connecting the tail of the second movable guide vane and the center of the pitch circle is L2; When N=1, the spoiler bar (6) is arranged between the angles L1 and L2; When N>1, the spoiler rods (6) are distributed at equal angles in the circumferential direction of the pitch circle, and the position of one of the spoiler rods (6) is the same as when N=1.

3. The method for optimizing the S characteristics of a pump turbine according to claim 1, characterized in that: In the second step, the cross section of the spoiler rod (6) is circular or regular polygonal.

4. A method for optimizing the S characteristics of a pump turbine according to claim 3, characterized in that: The radius of the spoiler rod (6) in step 2 is d, and the value range of d is 3 mm. <d<[(D3-D1) / 2]mm; Wherein, D1 is the outer diameter of the crown of the impeller (4), D3 is the diameter of the inscribed circle of the tail of each movable guide vane (3) when the movable guide vane (3) is at its maximum opening, and D1 and D3 are concentric circles.

5. The method for optimizing the S characteristics of a pump turbine according to claim 3, characterized in that: The side length of the spoiler rod (6) in step 2 is d, and the value range of d is 3 mm. <d<[(D3-D1) / 2]mm; Wherein, D1 is the outer diameter of the crown of the impeller (4), D3 is the diameter of the inscribed circle of the tail of each movable guide vane (3) when the movable guide vane (3) is at its maximum opening, and D1 and D3 are concentric circles.

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