Aerofoil guide vane for controlling hydraulic instability of a pump-turbine

Abstract

The present application belongs to the technical field of mechanical energy storage and hydroelectric power generation, and discloses a wing type flow guide component for controlling the hydraulic instability of a pump-turbine. The wing type flow guide component installed in the draft tube enables the pump-turbine to work stably in the power generation condition and the water pumping condition, and relieves the spiral vortex band and pressure pulsation in the draft tube. The wing type flow guide component in the middle of the straight conical section of the draft tube is connected to the wall surface of the draft tube by an anchor chain. The spiral vortex band enters the flow guide component, and first, due to the limitation of the wall surface, the vortex band cannot move radially, and after impacting the wall surface, it is broken into a large number of small vortex structures. Secondly, the device separates the dead water area from the main flow area, and the vortex band cannot obtain the speed compensation of the main flow area, resulting in the decrease of the peripheral velocity and the eccentricity. This method can simultaneously relieve the hydraulic instability of the pump-turbine in the power generation condition and the water pumping condition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluid machinery and hydropower, and particularly relates to a wing-type flow guide device for controlling the hydraulic instability of a pump-turbine. BACKGROUND

[0002] As a core component of a pumped storage power station, the stable operation of a pump-turbine unit is directly related to the safety of the power station. The design of the pump-turbine unit not only needs to meet the pumping condition, but also needs to take into account the power generation condition, so it is extremely difficult to ensure that the unit is in an optimal performance range in both pump and turbine conditions. With the increasing task of peak and frequency regulation of the pump-turbine and the shortening of the regulation period, the instability problem caused by the spiral vortex band in the draft tube of the pump-turbine seriously affects the normal operation of the unit.

[0003] When the pump-turbine operates in the turbine condition, the water flow direction is the same as the rotation direction of the runner. However, when operating in a small opening condition, the water flow no longer flows according to the optimal condition, and under the action of the runner and the centrifugal force, it quickly deflects downward around the ring. This causes a large circumferential velocity of the water flow at the inlet of the draft tube, resulting in a low central pressure and a high peripheral pressure inside the draft tube, forming a dead water area at the central position. Finally, a large-scale eccentric spiral vortex band is formed in the straight conical section and even the elbow section of the draft tube.

[0004] When the pump-turbine operates in the pump condition, the draft tube acts as the water inlet at this time, and the internal flow pattern will affect the flow downstream. In the small flow condition, the water flow in the draft tube still spirals downstream, and then backflow occurs, and the low-frequency, high-amplitude pressure pulsation and non-steady excitation force generated will produce noise, and in severe cases, it may even cause fatigue fracture of the blades.

[0005] The low-frequency pressure pulsation caused by the vortex band in the draft tube is an important factor affecting the stability of the operation of the turbine unit, which is not conducive to the long-term safe and stable operation of the unit. The wing-type flow guide component used in this method can prevent the spiral vortex band from spiraling in, break the large-scale vortex band using the wall surface, reduce the circumferential velocity and eccentricity of the vortex band, and thus ensure the stability of the operation of the unit. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the present application proposes a wing-type flow guide device for controlling the hydraulic instability of a pump-turbine, which can improve the pressure distribution in the draft tube and achieve the purpose of suppressing large-scale spiral vortex bands and low-frequency high-amplitude pressure pulsations induced thereby, regardless of whether the pump-turbine is in the pump condition or the turbine condition.

[0007] In order to achieve the above-mentioned purposes, the application discloses a wing-shaped guide device for controlling the hydraulic instability of a water pump turbine, characterized in that the wing-shaped guide device for controlling the hydraulic instability of the water pump turbine comprises a wing-shaped guide component (2), a conventional water pump turbine draft tube (1) and an anchor chain (3); the draft tube (1) comprises a straight taper section (11), a bent elbow section (12) and a diffusion section (13); the wing-shaped guide component (2) is a symmetrical rotary body wing-shaped flow component designed by an asymmetric wing-shaped structure, is installed in the middle of the straight taper section (11) of the draft tube and has a center axis which is collinear with the center axis of the straight taper section (11) of the draft tube; the tail water pipe flow field distribution characteristics of the power generation working condition and the water pumping working condition of the water pump turbine are changed by the wing-shaped guide component (2), so that the large-scale spiral vortex belt in the draft tube and the low-frequency high-amplitude pressure pulsation induced thereby are inhibited.

[0008] Further, the wing-shaped guide component (2) has a shape with a large upper opening, a large lower opening and a small middle opening, the upper end surface is parallel to the lower end surface, the diameter D3 of the lower end opening is larger than the diameter D1 of the upper end opening, and the diameter D2 of the middle part is the smallest.

[0009] Further, the height H2 of the wing-shaped guide component (2) is (0.11-0.15)H, the inlet diameter D1 is (0.1-0.12)D, the distance H1 between the inlet of the wing-shaped guide component (2) and the inlet of the draft tube (1) is (0.02-0.05)H, the angle alpha between the chord length of the wing-shaped guide component (2) and the central axis of the straight taper section (11) of the draft tube is 2.5-4 degrees, and the maximum thickness t1 of the wing-shaped guide component (2) is 15-20 cm.

[0010] Further, the wing-shaped guide component (2) is fixed to the inner wall surface of the straight taper section (11) of the draft tube by a plurality of anchor chains (3), the plurality of anchor chains (3) are respectively welded and fixed to the sections at 0.2H1 and 0.8H1 of the wing-shaped guide component (2), the plurality of anchor chains (3) on each section are symmetrically distributed in the circumferential direction, and the anchor chains (3) are arranged in the same way at the sections.

[0011] Further, the anchor chain (3) has a certain flexibility, can withstand a large water flow impact resistance when the water pump turbine is switched between working conditions, and can also adaptively correct and adjust the working state of the wing-shaped guide component (2) by a small amplitude.

[0012] The application has the following advantages after adopting the above technical scheme:

[0013] (1) because the cross-sectional shape of the airfoil guide component is airfoil, not only can reduce the resistance of the guide device, in the water turbine working condition and the water pump working condition can play a two-way guide effect, reduce the vibration problem caused by the frequent change of working condition, help to improve the overall stability of the unit;

[0014] (2) the pressure pulsation amplitude in the draft tube can be reduced by 1 / 3 to 1 / 2, the frequency is reduced, the eccentric distance of the vortex band is effectively reduced, and the control effect of pressure pulsation is obvious;

[0015] (3) the airfoil guide component separates the dead water area from the main flow area, the dead water area cannot be compensated by the speed of the main flow area, thereby reducing the peripheral speed, reducing the eccentricity of the vortex band, and causing the vortex band to develop movement to the periphery;

[0016] (4) when the vortex band enters the airfoil guide component, the pressure gradually decreases, and the axial velocity increases. The increase of the axial velocity slows down the formation of the dead water area, thereby improving the pressure distribution and effectively relieving the pressure pulsation in the center of the draft tube;

[0017] (5) the vortex band entering the airfoil guide device will hit the wall of the device due to the limited space inside the device and the shape of large at the top and small in the middle, causing the vortex band to break, eliminating part of the large scale vortex band, thereby fundamentally relieving the pressure pulsation;

[0018] (6) the present application does not affect the efficiency of the normal operation of the pump-turbine, the airfoil guide device is simple in structure, does not need additional energy supply device and complex control system, and does not involve the replacement of other parts of the hydropower station, solving the problem of unit vibration induced by spiral vortex band under partial load working condition. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present application will be further described in detail below in combination with the drawings and specific embodiments;

[0020] Figure 1 is a schematic diagram of the overall device of the present application;

[0021] Figure 2 is a top view (top view direction) of the overall device of the present application;

[0022] Figure 3 is a cross-sectional view of the airfoil guide component (front view direction);

[0023] Figure 4 is a fixing method diagram of the airfoil guide component of the present application;

[0024] Figure 5 is a working principle diagram of the airfoil guide component of the present application;

[0025] Wherein: 1-tailwater pipe, including: 11-straight cone section, 12-bent elbow section, 13-diffuser section, 2-airfoil guide component, 21-airfoil, 3-anchor chain. Detailed Implementation

[0026] like Figures 1-4 As shown, an airfoil-shaped flow guide device for controlling the hydraulic instability of a pump-turbine is characterized in that: the airfoil-shaped flow guide component for controlling the hydraulic instability of a pump-turbine includes an airfoil-shaped flow guide component 2, a conventional pump-turbine draft tube 1, and an anchor chain 3; the draft tube 1 includes a straight conical section 11, a bend section 12, and a diffuser section 13; the airfoil-shaped flow guide component 2 is a symmetrical rotating airfoil flow-through component, designed with an airfoil 21 of an asymmetrical airfoil structure, installed in the middle of the straight conical section 11 of the draft tube, and its central axis is collinear with the central axis of the straight conical section 11 of the draft tube; the airfoil-shaped flow guide component 2 changes the flow field distribution characteristics of the draft tube under the power generation and pumping conditions of the pump-turbine, thereby suppressing the large-scale spiral vortex bands in the draft tube and the low-frequency high-amplitude pressure pulsations induced by them.

[0027] like Figure 4 As shown, in one embodiment, the airfoil guide component 2 is obtained by rotating the airfoil 21 360° around the central axis of the tailpipe conical section 11, exhibiting a symmetrical structure. The airfoil 21 is an asymmetric airfoil with good hydrodynamic performance. The airfoil guide component 2 has a shape with a large opening at the top and bottom and a small opening in the middle. The upper end face is parallel to the lower end face. The diameter D3 of the lower opening is larger than the diameter D1 of the upper opening, and the diameter D2 of the middle part is the smallest.

[0028] like Figure 1 As shown, in one embodiment, the distance H1 between the airfoil guide component 2 and the inlet of the tailwater pipe 1 is (0.02~0.05)H, where H is the height of the straight conical section 11 of the tailwater pipe, the height H2 of the airfoil guide component 2 is (0.11~0.15)H, the inlet diameter D1 is (0.1~0.12)D, where D is the inlet diameter of the tailwater pipe 1, the angle α between the chord length of the airfoil 21 and the central axis of the straight conical section 11 of the tailwater pipe is 2.5°~4°, and the maximum thickness t1 of the airfoil 21 is 15cm~20cm.

[0029] like Figure 1 , Figure 2 and Figure 4 As shown, in one embodiment, the airfoil guide component 2 is welded to the inner wall of the straight conical section of the tailrace pipe by eight anchor chains 3. Four anchor chains 3 are welded to the section at 0.2H1 of the airfoil guide component 2, and the other four anchor chains 3 are welded to the section at 0.8H1 of the airfoil guide component 2. The four anchor chains on each section are symmetrically distributed in the circumferential direction, and the included angle between any two anchor chains is 90°. The arrangement of the anchor chains on the upper and lower sections is exactly the same.

[0030] As Figure 4 shown, in an embodiment, the anchor chain (3) has a certain flexibility, which can withstand a large water flow impact resistance when the water pump turbine is in the working condition conversion, and can also adaptively correct and adjust the working state of the airfoil guide part (2) in a small amplitude.

[0031] As Figure 5 shown, in an embodiment, the airfoil guide device operates in the water turbine working condition, the water flow flows from the draft tube inlet to the draft tube outlet, a large number of spiral vortex bands will enter the guide device from the upper opening of the airfoil guide device. First, due to the restriction of the wall surface, the vortex band cannot move radially, and after impacting the wall surface, it is broken into a large number of small vortex structures. Secondly, the wall surface separates the dead water area from the main flow area, and the vortex band cannot obtain the speed compensation of the main flow area, resulting in the decrease of the peripheral velocity and the eccentricity. When the airfoil guide device operates in the water pump working condition, the water flow flows from the draft tube outlet to the draft tube inlet, under the combined action of the backflow phenomenon and the runner rotation, the water flow in the draft tube still spirals downstream, and the airfoil guide device can still break the vortex band while reducing the peripheral velocity and eccentricity of the vortex band, thereby fundamentally reducing the pressure pulsation and unit vibration problem.

[0032] In the above embodiment, the purpose of the airfoil guide device for controlling the hydraulic instability of the water pump turbine can be achieved, and the person skilled in the art can select according to the actual situation. The airfoil guide device for controlling the hydraulic instability of the water pump turbine provided by the present application can be applied to the hydraulic stability control of the water pump turbine, and the reliability of the bidirectional operation of the water pump turbine can be enhanced.

[0033] The above is only an example and description of the structure of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the structure of the present application or exceed the scope defined by the present application, and should be within the protection scope of the present application.

Claims

1. An airfoil-shaped flow guide device for controlling the hydraulic instability of a water pump turbine, characterized in that: The airfoil guide device for controlling the hydraulic instability of a pump-turbine includes an airfoil guide component (2), a conventional pump-turbine draft tube (1), and an anchor chain (3); the draft tube (1) includes a straight conical section (11), a bend section (12), and a diffuser section (13); the airfoil guide component (2) is a symmetrical rotating airfoil flow-through component, designed with an asymmetrical airfoil structure (21), installed in the middle of the straight conical section (11) of the draft tube, and its central axis is collinear with the central axis of the straight conical section (11); the height H2 of the airfoil guide component (2) is (0.11~0.15)H, and the inlet diameter D1 is (0.1... ~0.12)D, where D is the inlet diameter of the tailrace pipe (1), the distance H1 between the inlet of the airfoil guide component (2) and the inlet of the tailrace pipe (1) is (0.02~0.05)H, where H is the height of the straight conical section (11) of the tailrace pipe; the angle α between the chord length of the airfoil (21) and the central axis of the straight conical section (11) of the tailrace pipe is 2.5°~4°, and the maximum thickness t1 of the airfoil (21) is 15cm~20cm; the tailrace flow field distribution characteristics of the pump turbine in the power generation and pumping conditions are changed by the airfoil guide component (2), thereby suppressing the large-scale spiral vortex band in the tailrace pipe and the low-frequency high-amplitude pressure pulsation induced by it.

2. The airfoil guide device for controlling the hydraulic instability of a water pump turbine according to claim 1, characterized in that: The airfoil guide component (2) has a shape with large openings at the top and bottom and a small opening in the middle. The upper end face is parallel to the lower end face. The diameter D3 of the lower end opening is larger than the diameter D1 of the upper end opening, and the diameter D2 of the middle part is the smallest.

3. The airfoil guide device for controlling the hydraulic instability of a water pump turbine according to claim 1, characterized in that: The airfoil guide component (2) is fixed to the inner wall of the tailpipe conical section (11) by multiple anchor chains (3). The multiple anchor chains (3) are welded and fixed to the cross sections at 0.2H1 and 0.8H1 of the airfoil guide component (2), and the multiple anchor chains (3) on each cross section are symmetrically distributed in the circumferential direction. The arrangement of the anchor chains (3) at the cross section is exactly the same.

4. The airfoil guide device for controlling the hydraulic instability of a water pump turbine according to claim 3, characterized in that: The anchor chain (3) has a certain degree of flexibility. When the pump turbine changes its operating conditions, it can withstand the large water flow impact resistance and also make small adaptive corrections and adjustments to the working state of the airfoil guide component (2).

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