Guide vane structure suitable for variable-speed pump turbine

Abstract

The invention relates to a guide vane structure of a variable-speed pump turbine, and provides a movable guide vane with non-uniform thickness, which is structurally characterized in that the movable guide vane is of a unique structure with a thick middle part and two thin ends along the axial direction of the movable guide vane. A smooth normal distribution curve is adopted to carry out thickness change design on the area where the movable guide vane is transited from the thick middle part to the thin parts at the two ends. According to the transition mode, sharp edges or sudden changes are avoided, and the continuity and uniformity of thickness changes are ensured. The movable guide vane adopts a streamline section airfoil design, and the front edge of the movable guide vane is blunt so as to reduce water flow impact and separation phenomena; and the rear edge is designed to be a streamline which is gradually narrowed, so that water flow is optimized, and turbulence and energy loss are reduced. The invention further provides a design scheme for refitting the fixed guide vane, the angle of the fixed guide vane can be adjusted in real time according to the real-time water head, the real-time flow, the variable rotating speed working condition and the like, the overall performance and the operation efficiency of the unit are improved, and the maintenance and overhaul cost is reduced.

Description

Technical Field

[0001] This invention relates to the design of guide vane structures for variable speed water pump turbines, specifically a movable guide vane structure and a method for modifying fixed guide vanes for variable speed water pump turbines. Background Technology

[0002] Against the backdrop of global energy transition, hydropower, as a renewable and clean energy source, is receiving increasing attention. Modern hydropower projects place increasingly higher demands on the comprehensive performance of pump-turbine units. Variable-speed pump-turbines can dynamically adjust speed and flow according to grid demand, enabling the unit to operate efficiently and stably over a wide range of operating conditions.

[0003] The guide vanes of a pump-turbine include movable and fixed guide vanes. As a key component in variable-speed pump-turbines for regulating flow and speed, the performance of the movable guide vanes determines the efficiency, stability, and operating range of the entire unit. With the development of variable-speed pump-turbines towards higher head and larger capacity, the hydrodynamic loads on the movable guide vanes are increasing, necessitating improvements in their structural strength and reliability to prevent deformation and breakage under the impact of high-pressure, high-speed water flow, thus ensuring the safe and stable operation of the unit.

[0004] Fixed guide vanes, as an important water intake component of pump-turbines, guide water from components such as the volute into the runner at a specific angle and direction, allowing for better interaction between the water flow and the runner. While fixed guide vanes with a fixed angle are suitable for the rated speed and operating conditions of constant-speed units, they cannot adapt to the frequent operating condition changes of variable-speed pump-turbines. When actual operating conditions deviate from design conditions, the angle between the water flow and the guide vanes may no longer be optimal, leading to increased hydraulic losses, decreased efficiency, and unit vibration.

[0005] Existing technology 1 The existing movable guide vanes have a uniform thickness distribution along the axial direction. This uniform thickness performs well under conditions with relatively stable load variations and is generally suitable for situations where head and flow rates are relatively stable. Under these conditions, fluctuations in water velocity, pressure, and other parameters are minimal, preventing severe impacts and complex forces on the guide vanes. In terms of pump-turbine unit operation, it can basically meet the power station's control requirements for flow rate and direction during peak shaving, frequency and phase regulation, and emergency standby operations.

[0006] Disadvantages of existing technology 1 Uniform thickness movable guide vanes have significant performance limitations and are difficult to adapt to the complex operating conditions of variable speed pump-turbine units. Specifically, these limitations are manifested in the following aspects: When the speed and load fluctuate significantly, the uniform thickness of the movable guide vane cannot maintain efficient and stable operation. Especially under off-design conditions, its efficiency drops significantly, making it difficult to meet the high-efficiency operation requirements of variable speed pump turbines.

[0007] Under varying speed and flow rate conditions, the movable guide vanes exhibit poor flow adaptability and flow regime performance. Especially under low flow rate conditions, water flowing through the guide vanes is prone to flow separation and vortex phenomena, which not only increases energy loss but also leads to flow turbulence, further reducing the overall efficiency of the pump-turbine.

[0008] Under high head and high flow conditions, the water pressure and impact force on the middle part of the movable guide vane increase significantly, leading to uneven stress distribution on the guide vane surface and a tendency for localized stress concentration. This not only affects the service life of the guide vane but may also jeopardize the operational safety of the unit, failing to meet the structural reliability and stable operation requirements of variable speed pump-turbines.

[0009] In summary, the uniform thickness of the movable guide vane is significantly insufficient when dealing with the complex operating conditions of variable speed pump turbines, and it is difficult to meet the requirements of high efficiency, stable operation and structural reliability.

[0010] Existing technology 2 Under stable load and head operating conditions, existing fixed guide vanes can guide water flow into the runner in a suitable direction and speed, effectively converting the kinetic and potential energy of the water flow into the mechanical energy of the runner. This allows the turbine to maintain stable output and efficiency, enabling it to operate stably near its rated operating conditions for extended periods. The performance of fixed guide vanes is optimal when operating parameters such as head and flow rate are close to their design values.

[0011] Fixed guide vanes can, to some extent, guide and rectify the water flow, giving it a more regular flow pattern before it enters the impeller, which helps improve the impeller's working efficiency and stability.

[0012] Disadvantages of existing technology 2 The fixed guide vane angle is not adjustable, which has the following main limitations: The angle of the fixed guide vanes cannot be adjusted according to the requirements of head, flow rate and pressure, which limits the operating range and performance improvement of the unit and makes it difficult to meet the requirements of variable speed pump turbines for frequent changes in operating conditions.

[0013] When operating under unbalanced conditions, the boundary layer of the fixed guide vane is prone to flow separation, which increases water flow resistance and flow loss, resulting in a decrease in the overall efficiency of the pump turbine.

[0014] The inability to adjust the angle according to different operating conditions can intensify the interaction between the water flow and the impeller under certain conditions, resulting in large pressure pulsations, affecting the stability of the unit, and may also cause vibration and noise.

[0015] If the guide vanes are worn or corroded, the entire guide vane assembly often needs to be replaced or repaired during maintenance and repair. This is difficult to do and may require a long downtime, affecting the normal operation of the equipment. Summary of the Invention

[0016] To adapt to the complex and varied operating conditions and environment of variable speed pump turbines and overcome the limitations of existing movable guide vanes in maintaining high efficiency under non-design conditions, this invention proposes a movable guide vane structure adapted to variable speed pump turbines. It aims to solve problems such as poor water flow adaptability under variable speed conditions and local stress concentration on the surface of the movable guide vane under high flow conditions.

[0017] A movable guide vane structure suitable for variable speed water pump turbines, wherein the movable guide vane has a structure that is thick in the middle and thin at both ends along its central axis, and the leading edge of the movable guide vane is blunt and the trailing edge is a streamlined shape that gradually narrows.

[0018] Furthermore, the thickness of the movable guide vane is gradually varied from the middle to the upper and lower ends using a normal distribution curve.

[0019] Furthermore, the cross-sections of the movable guide vanes at all positions have the same airfoil chord length; at any corresponding position of the airfoil chord length, the thickness of the same cross-section of the movable guide vane is the same multiple of the thickness of the upper and lower end faces.

[0020] Furthermore, the thickness of the cross-section at the middle of the active guide vane at any airfoil chord position is 1.5 times the thickness of the upper and lower end faces.

[0021] Furthermore, the foremost point of the leading edge and the rearmost point of the trailing edge of the movable guide vane are both straight lines, parallel to the central axis of the rotating shaft; the central axis of the rotating shaft coincides with the center point of the upper and lower end faces of the movable guide vane.

[0022] The present invention provides a movable guide vane with non-uniform thickness, the most significant structural feature of which is a unique structure that is thick in the middle and thin at both ends along the axial direction of the movable guide vane.

[0023] The thickness variation of the guide vane, transitioning from a thicker central section to thinner ends, is designed using a smooth normal distribution curve. This transition method avoids sharp angles or abrupt changes, ensuring the continuity and uniformity of the thickness variation.

[0024] The movable guide vane adopts a streamlined cross-section airfoil design, with a blunt leading edge to reduce water flow impact and separation; the trailing edge is designed as a gradually narrowing streamline to optimize water flow and reduce turbulence and energy loss.

[0025] The shaft is made of high-hardness alloy steel, and chrome plating on the surface of the shaft further enhances its wear resistance and corrosion resistance.

[0026] Since the angle of the fixed guide vanes is designed for rated speed or flow rate, when the speed or flow rate deviates from the design point, the angle at which the water enters the guide vanes and impeller is no longer optimal. This results in impact and eddies, leading to a sharp drop in efficiency and limiting the operating range and performance improvement of the variable speed pump-turbine, making it difficult to meet the requirements of frequent changes in operating conditions. Therefore, this invention proposes a design scheme to modify the fixed guide vanes. By adjusting the angle of the fixed guide vanes, it ensures that the water enters the guide vanes at the optimal angle of attack even at non-rated speeds and flow rates, improving the flow state of the water and enabling the unit to maintain high efficiency and stability under a wide range of operating conditions, including low head and partial load.

[0027] A method for modifying a fixed guide vane includes the following steps: The fixed guide vane is located between the movable guide vane and the volute. By removing the original fixed connecting parts between the fixed guide vane and the fixed support structure inside the turbine volute, a suitable rotating shaft mounting hole is machined at the connection point between the fixed guide vane and the support structure. The guide vane rotating shaft is installed, and the rotating shaft is made of high-strength alloy steel. The rotating shaft is connected to the fixed guide vane by welding to ensure a firm connection between the rotating shaft and the fixed guide vane. One end of the rotating shaft is connected to the control ring via a connecting rod, and the other end is connected to the fixed support structure (bottom ring) via a bearing to ensure that the fixed guide vane can smoothly rotate around the rotating shaft to open and close.

[0028] Furthermore, the surface of the rotating shaft is treated with chrome plating for corrosion resistance and wear resistance.

[0029] Furthermore, a hydraulic drive device is used to adjust the opening of the fixed guide vane by driving the servo drive, the servo drive piston rod, the control ring, and the connecting rod.

[0030] Furthermore, the hydraulic drive device includes two drive relays and two relay piston rods; the two relay piston rods are respectively connected to two positions 180 degrees apart on the control ring, and are respectively connected to one drive relay.

[0031] Furthermore, the hydraulic drive device is controlled by a computer monitoring system to start / stop and adjust its opening.

[0032] The beneficial effects of the present invention are: (1) A movable guide vane with a thick middle and thin ends that is adapted to a variable speed water pump turbine can adapt to the pressure distribution of water flow under various working conditions, optimize the water flow guidance effect and ensure structural strength.

[0033] (2) The increased thickness of the guide vane enhances its strength during high-load operation and can effectively resist the impact of water flow.

[0034] (3) The thickness of the guide vane is gradually changed from the middle to both ends by using the normal distribution curve, so that the water flow can smoothly transition when it flows through the guide vane, reducing the flow resistance of the water flow in the transition area, effectively suppressing the water flow turbulence and energy loss caused by the sudden change in thickness, and at the same time reasonably balancing the pressure distribution on the surface of the guide vane.

[0035] (4) The material of the movable guide vane shaft is alloy steel with high hardness, and the surface is chrome-plated to further enhance wear resistance and corrosion resistance.

[0036] (5) The fixed guide vane with adjustable opening is more suitable for the frequent working condition changes of variable speed water pump turbine. The modification scheme is relatively simple. The opening of the movable guide vane is changed by using a separate hydraulic drive system, which can ensure the stability of power transmission. Attached Figure Description

[0037] Figure 1 This is an isometric schematic diagram of the three-dimensional structure of the movable guide vane of the present invention; Figure 2 This is a front view schematic diagram of the movable guide vane of the present invention; Figure 3 This is a top view schematic diagram of the movable guide vane of the present invention; Figure 4 This is a side view schematic diagram of the movable guide vane of the present invention; Figure 5 This is a diagram of the hydraulic drive system modified from the fixed guide vane of the present invention; Figure 6 This is a schematic diagram of the guide vane in the fully closed state of the fixed guide vane of the present invention; Figure 7 This is a schematic diagram of the guide vane in the fully open state of the fixed guide vane of the present invention.

[0038] In the figure: 11-Modible guide vane body, 12-Upper end face of movable guide vane, 13-Lower end face of movable guide vane, 14-Middle cross-section of movable guide vane, 15-Modible guide vane pivot, 16-Central axis of movable guide vane pivot, 17-Leading edge of movable guide vane, 18-Trail edge of movable guide vane; 21-Vortex casing, 22-Fixed guide vane, 23-Fixed guide vane rotating shaft, 24-Connecting rod, 25-Control ring, 26-Relay device, 27-Relay device piston rod. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] This invention provides a movable guide vane adapted to a variable speed water pump turbine, with the structure as follows: Figure 1As shown, it includes: a movable guide vane shaft 15; a central axis 16 of the movable guide vane shaft; a movable guide vane body 11; an upper end face 12 of the movable guide vane; a lower end face 13 of the movable guide vane; a central cross-section 14 of the movable guide vane; a leading edge 17 of the movable guide vane; and a trailing edge 18 of the movable guide vane. Along the axial direction, the movable guide vane has a unique structure that is thicker in the middle and thinner at both ends. The airfoil thickness is greatest in the central cross-section 14 of the movable guide vane, and smallest in the upper end face 12 and the lower end face 13 of the movable guide vane. The increased thickness in the middle of the guide vane is to enhance its strength under high load operation to resist the impact force of the water flow. Based on a comprehensive analysis of the water flow pressure distribution, velocity changes, and mechanical stress of the guide vane under different operating conditions of the variable speed pump turbine, this structure aims to achieve a dual improvement in hydraulic performance and structural strength.

[0041] During the operation of a water pump turbine, the pressure distribution on the surface of the movable guide vanes is uneven. When water flows through the guide vanes, it rubs and collides with the vane surface, resulting in energy loss. Because the water flow velocity is higher in the central region, the friction and collision with the guide vane surface are stronger, converting energy loss into increased pressure; therefore, the pressure in the central region is relatively high. At the two ends near the shaft, the water flow velocity is lower, the interaction with the guide vane surface is weaker, and the pressure is correspondingly lower. Designing the movable guide vanes to be thicker in the middle and thinner at both ends allows the structural strength of the guide vanes to better match this pressure distribution. Simultaneously, the thicker middle section can better guide the mainstream water flow, allowing the water to enter or leave the turbine at the expected angle when passing through the guide vanes. Therefore, the movable guide vane structure, thicker in the middle and thinner at both ends, ensures structural strength and improves water flow adaptability under variable speed conditions.

[0042] The movable guide vane shaft 15 is connected to the upper and lower end faces 12 and 13 of the movable guide vane, with the center of the shaft located at the center point of the end face of the movable guide vane. As a key component supporting the guide vane and transmitting torque, the shaft must possess sufficient strength to reduce deformation under stress and ensure the positional accuracy and precise movement of the movable guide vane. Water pumps and turbines typically operate in water environments containing certain impurities, and particles such as silt in the water flow can cause wear on the shaft. Therefore, the shaft is made of alloy steel, which has high surface strength and hardness, and chrome plating further enhances its wear resistance and corrosion resistance, ensuring stable torque transmission during frequent guide vane opening adjustments while resisting erosion from water flow silt.

[0043] Figure 2 This is a front view schematic diagram of a non-uniform thickness movable guide vane proposed in this invention. The cross-sections of the movable guide vane at each position have the same length of chord. Therefore, the leading edge 17 and the trailing edge 18 of the movable guide vane are both straight lines and parallel to the central axis 16 of the movable guide vane's rotation axis. The upper end face 12, the lower end face 13, and the middle cross-section 14 of the movable guide vane are parallel to each other.

[0044] Figure 3 This is a top view schematic diagram of the movable guide vane proposed in this invention. The leading edge of the movable guide vane is blunt-nosed, which helps the water flow to smoothly bypass the leading edge of the guide vane, effectively reducing the pressure peak during water flow impact and reducing the possibility of water flow separation. The trailing edge is designed as a gradually narrowing streamline, which helps the water flow on the upper and lower surfaces of the movable guide vane to quickly converge at the trailing edge of the guide vane, causing the water flow to leave the guide vane smoothly, reducing eddies in the wake, reducing the degree of turbulence on the guide vane surface, and improving hydraulic efficiency. The upper end face 12 of the movable guide vane and the middle cross section 14 of the movable guide vane have the same airfoil chord length. At any corresponding position of the airfoil chord length, the airfoil thickness of the middle cross section 14 of the movable guide vane is 1.5 times that of the upper end face 12 of the movable guide vane.

[0045] Figure 4 This is a side view of the movable guide vane proposed in this invention. In the transition region from the central cross-section 14 of the movable guide vane to the upper and lower end faces 12 and 13, the guide vane thickness transitions using a smooth normal distribution curve. The thickness of the central cross-section at any chord length is 1.5 times the thickness of the corresponding end face, and the airfoil thickness at any chord length of the cross-section is the same multiple of the thickness of the corresponding end face. Therefore, this method can determine a unique normal distribution curve to achieve a gradual change in guide vane thickness. This gradual thickness change reduces flow resistance in the transition region, prevents flow separation, and allows for a smooth transition of water flow as it passes through the guide vane, effectively suppressing turbulence and energy loss caused by abrupt changes in thickness.

[0046] This invention proposes a modification scheme for a fixed guide vane structure. The specific modification steps are as follows: Remove the original fixed connecting parts between the fixed guide vane and the fixed support structure, such as welded or bolted connections. Machine a suitable rotating shaft mounting hole at the connection point between the fixed guide vane and the support structure. Install the guide vane rotating shaft, which is made of high-strength alloy steel to ensure its structural strength and connection stability. Connect the rotating shaft to the fixed guide vane by welding to ensure a secure connection. One end of the rotating shaft is connected to the control ring via a connecting rod, and the other end is connected to the fixed support structure via a bearing, ensuring that the fixed guide vane can smoothly rotate around the rotating shaft to open and close.

[0047] Figure 5This is a diagram of the hydraulic drive system for the modified fixed guide vane of this invention. The structure includes: a fixed guide vane 22; a fixed guide vane rotation shaft 23; a connecting rod 24; a control ring 25; a servo drive 26; and a servo drive piston rod 27. The hydraulic drive system achieves the opening change of the fixed guide vane by driving the servo drive, the servo drive piston rod, the control ring, and the connecting rod, providing power for the opening and closing of the guide vane. The hydraulic drive has a large driving force and can be applied to large water pumps and turbines. A hydraulic cylinder and hydraulic lines are installed. The piston rod of the guide vane servo drive is connected to the control ring through a suitable connector. The control ring is connected to the rotation shaft of the fixed guide vane through a connecting rod, which transmits power to the guide vane, realizing the rotation of the guide vane.

[0048] Figure 6 and Figure 7 These are schematic diagrams of the fully closed and fully open states of the modified fixed guide vane of this invention, including: a volute 21; a fixed guide vane 22; a fixed guide vane rotation shaft 23; a connecting rod 24; and a control ring 25. A separate control system is configured for the hydraulic system, responsible for directly executing start and stop commands issued by the computer monitoring system. Its working principle is as follows: When the water pump turbine needs to switch from the running state to the stop state, the control system sends a stop signal to the hydraulic drive system control circuit, driving the servo piston rod to move towards the closed direction of the guide vane. When the guide vane reaches the fully closed position, it completely blocks the water flow, achieving the water flow cutoff function during shutdown. When the water pump turbine needs to start from the stop state and enter the running state, the control system sends a start signal to the control circuit, repeating the above transmission process, causing the guide vane to rotate to the fully open position. When the guide vane reaches the fully open position, the water flow can smoothly pass through the guide vane area into the impeller, driving the water pump turbine to operate normally. The guide vane opening can be adjusted in real time according to the actual operating conditions. During the process of changing speed, flow rate, head and unit operating conditions, the opening of the guide vanes can be adjusted to optimize the operating performance and efficiency and reduce maintenance costs.

Claims

1. A movable guide vane structure suitable for variable speed water pump turbines, characterized in that: The movable guide vane has a structure that is thick in the middle and thin at both ends along its central axis of rotation, and the leading edge of the movable guide vane is blunt and the trailing edge is a streamlined shape that gradually narrows.

2. The movable guide vane structure for a variable speed water pump turbine as described in claim 1, characterized in that, The thickness of the movable guide vane gradually changes from the middle to the upper and lower ends using a normal distribution curve.

3. The movable guide vane structure for a variable speed water pump turbine as described in claim 2, characterized in that, The cross-sections of the movable guide vanes at all positions have the same airfoil chord length; at any corresponding position of the airfoil chord length, the thickness of the same cross-section of the movable guide vane is the same multiple of the thickness of the upper and lower end faces.

4. The movable guide vane structure for a variable speed water pump turbine as described in claim 3, characterized in that, The thickness of the cross section at the middle of the movable guide vane at any airfoil chord position is 1.5 times the thickness of the upper and lower end faces.

5. A movable guide vane structure suitable for a variable speed water pump turbine as described in claim 3, characterized in that, The leading edge and trailing edge of the movable guide vane are both straight lines, parallel to the central axis of the rotating shaft; the central axis of the rotating shaft coincides with the center point of the upper and lower end faces of the movable guide vane.

6. A method for modifying a fixed guide vane, characterized in that, The variable speed water pump turbine includes a movable guide vane and a volute as described in any one of claims 1-5, with a fixed guide vane located between the movable guide vane and the volute. The original fixed connection between the fixed guide vane and the fixed support structure within the volute of the water pump turbine is removed. A suitable rotating shaft mounting hole is machined at the location where the fixed guide vane connects to the support structure. A rotating shaft for the guide vane is installed, and the rotating shaft is made of high-strength alloy steel. The rotating shaft is connected to the fixed guide vane by welding to ensure a secure connection between the rotating shaft and the fixed guide vane. One end of the rotating shaft is connected to the control ring via a connecting rod, and the other end is connected to the fixed support structure via a bearing, ensuring that the fixed guide vane can smoothly rotate around the rotating shaft to open and close.

7. A method for modifying a fixed guide vane as described in claim 6, characterized in that, The surface of the rotating shaft is treated with chrome plating for corrosion resistance and wear resistance.

8. A method for modifying a fixed guide vane as described in claim 6 or 7, characterized in that, A hydraulic drive device is used to adjust the opening of the fixed guide vane by driving the servo drive, the servo drive piston rod, the control ring and the connecting rod.

9. A method for modifying a fixed guide vane as described in claim 8, characterized in that, The hydraulic drive device includes two drive relays and two relay piston rods; the two relay piston rods are respectively connected to two positions 180 degrees apart on the control ring, and are respectively connected to one drive relay.

10. A method for modifying a fixed guide vane as described in claim 9, characterized in that, The hydraulic drive device is controlled by a computer monitoring system to start, stop, and adjust its opening.

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