Impeller for improving working condition cavitation erosion performance of water pump of pump turbine

Abstract

The utility model relates to the technical field of fluid mechanical equipment, in particular to an impeller for improving the working condition cavitation erosion performance of a water pump of a pump turbine, which comprises an upper crown and a lower ring which are correspondingly arranged up and down, a plurality of optimized blades are fixedly connected onto the lower ring, and each optimized blade comprises a basic blade layer and an offset blade layer. The basic blade layer and the offset blade layer are connected through an optimized blade layer, and the lower ring and the upper crown are both in a horn shape. By optimizing the offset blade layer structure of the blade, the inlet angle of the blade can be further increased, so that the bending of the blade is reduced, the flow area of the inlet of the blade is increased, and the extrusion of the blade is reduced, thereby improving the cavitation performance of the pump during operation under different flows and ensuring the working performance of the water pump.

Description

Technical Field

[0001] This utility model relates to the field of fluid machinery equipment technology, specifically to an impeller that improves the cavitation performance of water pump turbines under operating conditions. Background Technology

[0002] A pump-turbine is a special hydraulic machine that integrates the functions of a pump and a turbine, and is an important component and core of energy conversion in pumped storage units. However, the cavitation characteristics of a pump-turbine directly affect the excavation depth of a power station and the selection of the unit. Its cavitation and cavitation erosion characteristics mainly depend on the pump operating conditions. This is primarily because the flow separation zone after the impact between the pump blade tip and the water flow, as well as the low-pressure zone along the blade surface, occur at the blade inlet, resulting in a relatively large dynamic pressure drop and poor cavitation performance. Generally, the operating range of a pump is parallelogram-shaped, while the primary cavitation curve is U-shaped, surrounding the outside of the operating range. Therefore, the maximum and minimum flow conditions within the operating range are the two most dangerous points, where cavitation performance is most difficult to guarantee. Therefore, in order to ensure the efficient operation of the pump turbine under multiple operating conditions and improve its cavitation performance, it is necessary to further optimize the blade airfoil in order to improve the flow state at the impeller inlet under pump operating conditions, gradually increase the impeller inlet velocity, reduce flow separation, leave sufficient cavitation margin, improve flow stability, and thus reduce the formation of cavitation.

[0003] For example, Chinese patent publication number CN 220815874 U discloses a water pump turbine runner with a biomimetic blade inlet edge design, including an upper crown with a plurality of blades evenly distributed in a spiral pattern. Each blade has a biomimetic leading edge designed on its high-pressure edge. This utility model effectively reduces pressure pulsation in the bladeless region between the runner and the movable guide vanes by modifying the boundary layer separation of the high-pressure edge inlet section of the blades, improving the pressure distribution at the blade leading edge, enhancing the blades' anti-cavitation characteristics, and improving the hydraulic characteristics of the runner. However, a drawback is that the pump blades exhibit poor anti-cavitation and anti-erosion performance under maximum and minimum flow conditions. Utility Model Content

[0004] To address the problem of poor cavitation and cavitation erosion resistance of existing pump blades under maximum and minimum flow conditions, an impeller that can improve pump cavitation and enhance impeller cavitation erosion performance is proposed.

[0005] To achieve the above-mentioned technical effects, this utility model proposes:

[0006] An impeller for improving the cavitation performance of a water pump turbine includes an upper crown and a lower ring arranged correspondingly at the top and bottom. A plurality of optimized blades are fixedly connected to the lower ring. The optimized blades include a basic blade layer and an offset blade layer. The basic blade layer and the offset blade layer are connected through the optimized blade layer. Both the lower ring and the upper crown are trumpet-shaped.

[0007] By deflecting the basic blade layer to form an offset blade layer, and by optimizing the blade layer to connect the basic blade layer and the offset blade layer into a whole structure, the blade inlet angle can be further increased, thereby reducing blade bending, increasing the blade inlet flow area, reducing blade displacement, thereby improving the cavitation performance of the pump under different flow rates and ensuring the working performance of the pump; the optimized blade is fixedly connected to the inner side of the lower ring and connected to the outer side of the upper crown.

[0008] The portion of the offset blade layer near the water inlet edge is formed by rotating the first 2 / 5 of the blades of the base blade layer counterclockwise along the rib line.

[0009] The portion of the offset blade layer away from the inlet edge consists of 3 / 5 of the blades of the basic blade layer away from the inlet edge.

[0010] The offset blade layer is deflected relative to the base blade layer at an angle ranging from 1° to 3°.

[0011] The optimized blade layer is formed by splicing the pressure surface profile of the basic blade layer and the suction surface profile of the offset blade layer.

[0012] The optimized blade layer is connected to the basic blade layer and the offset blade layer via bridging curves.

[0013] The bridging curves include spline curves a, b, c, and d.

[0014] The spline curves a, b, c, and d satisfy the following equations:

[0015] Spline curve a: y = 0.3628x 2 +55.584x+2158.8;

[0016] Spline curve b: y = 3.0026x 2 +452.99x+17116;

[0017] Spline curve c: y = 25.881x 2 +3906.8x+147460;

[0018] Spline curve d: y = 11.659x 3 +2629.6x 2 +197702x+5E+06.

[0019] The optimized blades and the lower ring are integrally cast. The integrally cast structure enhances fatigue resistance and adapts to high-speed and high-head operating conditions.

[0020] The beneficial effects of this utility model are:

[0021] It improves pump cavitation and enhances impeller cavitation performance; it adapts to the maximum and minimum flow conditions within the pump's operating range. Attached Figure Description

[0022] Figure 1 A schematic diagram of the overall structure of the impeller used to improve the cavitation performance of a water pump turbine.

[0023] Figure 2 This is a three-dimensional profile diagram of the offset blade layer.

[0024] Figure 3 A schematic diagram of the three-dimensional profile for optimizing the blade layer.

[0025] Figure 4 This is a schematic diagram of the distribution of spline curves in a rectangular coordinate system.

[0026] Icon labels:

[0027] 1. Lower ring; 2. Upper crown; 3. Optimized blades; 4. Basic blade layer; 5. Offset blade layer; 6. Optimized blade layer; Detailed Implementation

[0028] This utility model provides an impeller for improving the cavitation performance of a water pump turbine under pump conditions. The preferred embodiment of the impeller for improving the cavitation performance of a water pump turbine under pump conditions is described below.

[0029] Example 1

[0030] This embodiment provides an impeller for improving the cavitation performance of a water pump turbine under pump operating conditions. It makes the flow pattern at the impeller inlet more uniform and stable during the pump's operation at Qmax and Qmin conditions within its operating range, improving the uniformity of the impeller inlet velocity distribution, reducing pressure drop and hydraulic losses at the blade inlet, thereby improving pump cavitation and enhancing impeller cavitation performance. The following specific embodiments illustrate the implementation of this invention. Those skilled in the art can easily understand other advantages and effects of this invention from the content disclosed in this specification.

[0031] Reference Appendix Figure 1 , 2The impeller for improving the cavitation performance of the water pump turbine includes an upper crown 2 and a lower ring 1 arranged vertically and vertically. Both the upper crown 2 and the lower ring 1 are trumpet-shaped and arranged symmetrically in parallel, forming an annular flow channel space. Optimized blades 3 are connected between the upper crown 2 and the lower ring 1. The optimized blades 3 are evenly distributed along the annular flow channel space, with their roots fixedly connected to the lower ring 1 and their tops extending to the inner surface of the upper crown 2. The optimized blades 3 include a basic blade layer 4 and an offset blade layer 5. The inlet edges of the basic blade layer 4 and the offset blade layer 5 are connected by an optimized blade layer 6, forming an integral blade. The front half of the offset blade layer 5 is formed by rotating the front 2 / 5 of the blades of the basic blade layer 4 counterclockwise by 1° to 3° along the rib line. The rear half of the offset blade layer 5 consists of the 3 / 5 of the blades of the basic blade layer 4 furthest from the inlet edge. The suction surface of the offset blade layer 5 is misaligned with the inlet edge of the base blade layer 4, and the two are connected by an optimized blade layer 6. The optimized blade layer 6 is formed by splicing the pressure surface profile of the base blade layer 4 and the suction surface profile of the offset blade layer 5, resulting in a smooth curved surface transition. The optimized blade layer 6 is connected to the base blade layer 4 and the offset blade layer 5 by a bridging curve, which is a continuous cubic spline curve to ensure fluid flow without separation.

[0032] The beneficial effects of this embodiment are that the staggered design of the offset blade layer 5 disperses the local high-pressure area at the water inlet edge, reducing the risk of cavitation erosion; the optimized curved splicing of the blade layer 6 reduces fluid separation and suppresses eddy current generation; and the bridging curve transition is smooth, avoiding stress concentration on the blade surface.

[0033] Example 2

[0034] Reference Appendix Figure 3 and 4 In this embodiment, the front 2 / 5 region of the base blade layer 4 is rotated counterclockwise by 2° to form an offset blade layer 5, with a wedge-shaped gap between its suction surface and the base blade layer 4. An optimized blade layer 6 covers the junction area of ​​the base blade layer 4 and the offset blade layer 5, and is smoothly connected to both the base blade layer 4 and the offset blade layer 5 via bridging curves. The bridging curves include spline curves a, b, c, and d, which are distributed sequentially in the regions L1, L2, L3, and L4 in a rectangular coordinate system. The spline curves a, b, c, and d are fitted and satisfy the following equation:

[0035] Spline curve a: y = 0.3628x 2 +55.584x+2158.8;

[0036] Spline curve b: y = 3.0026x 2 +452.99x+17116;

[0037] Spline curve c: y = 25.881x2 +3906.8x+147460;

[0038] Spline curve d: y = 11.659x 3 +2629.6x 2 +197702x+5E+06.

[0039] The bridging curves employ a segmented design, each corresponding to the connection requirements of different regions of the blade. Spline curve a, located at the blade root, has a gentle curvature, suitable for high-velocity regions. Spline curve b connects the middle of the blade, with a gradually increasing curvature, guiding the fluid towards the offset blade layer 5. The spline curve near the blade tip has the maximum curvature, matching the rotation angle of the offset blade layer 5. Spline curve d covers the blade trailing edge, with a rapidly decreasing curvature, preventing backflow at the trailing edge. The suction surface of the optimized blade layer 6 and the pressure surface of the offset blade layer 5 form a continuous surface, and the curvature change of the bridging curves is synchronized with the flow channel contraction rate.

[0040] The beneficial effects of this embodiment are that the segmented bridging curve adapts to different flow velocity gradients and reduces flow separation; the wedge gap guides the fluid to diffuse evenly and weakens the impact of cavitation collapse; and the curvature gradient design reduces pressure pulsation on the blade surface and extends fatigue life.

[0041] Example 3

[0042] The cavitation characteristics of a pump-turbine directly affect the excavation depth and unit selection of a power station, and its cavitation and cavitation erosion characteristics mainly depend on the pump operating conditions. The maximum and minimum flow rates within the pump's operating range are the two most dangerous points, where cavitation erosion performance is most difficult to guarantee. Existing optimizations of blade airfoils do not provide good anti-cavitation performance under the maximum and minimum flow rates within the pump's operating range. This embodiment provides an impeller that improves the cavitation erosion performance of a pump-turbine under pump operating conditions, making the impeller inlet flow more uniform and stable during Qmax and Qmin operating conditions within the pump's operating range, improving the uniformity of the impeller inlet velocity distribution, reducing blade inlet pressure drop and hydraulic losses, thereby improving pump cavitation and enhancing impeller cavitation erosion performance. The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0043] In a preferred embodiment, an impeller for improving the cavitation performance of a water pump turbine includes an upper crown 2, a lower ring 1, and optimized blades 3. The optimized blades 3 include a basic blade layer 4, an offset blade layer 5, and an optimized blade layer 6. The optimized blades 3 and the lower ring 1 are cast as a single unit, eliminating weak points in the connection and improving the blades' resistance to cavitation. The original blades of a pumped-storage unit model impeller have the drawback that the cavitation characteristics do not meet requirements when the pump operates under both high and low flow conditions. The offset blade layer 5 is formed by fixing the rear 3 / 5 of the blades of the basic blade layer 4 and using the position of the blade rib line of the front 2 / 5 of the inlet edge of the basic blade layer 4 as a base point. The front 2 / 5 of the blade inlet edge is rotated counterclockwise around this base point by a certain angle (2° in this embodiment). The optimized blade layer 6 is formed by splicing the pressure surface profile of the basic blade layer 4 and the suction surface profile of the offset blade layer 5, and bridging the connection point with a transition curve to ensure the smoothness of the blades.

[0044] Reference Appendix Figure 2 In this embodiment, the optimized blade 3 is divided into 11 layers with equal spacing from the upper crown 2 to the lower ring 1 (only the two layers closest to the upper crown 2 are shown in the figure). Along the flow direction, the front and back of the blade are divided into 5 segments of equal arc length, i.e.: A⌒B=B⌒C=C⌒D=D⌒E=E⌒F=l. At 2 / 5 arc length near the inlet edge, the same division point on the front and back of the blade is connected, and the midpoint OC=OG is taken. The midpoint of each layer is connected as the rotation axis OO'. After fixing the blade with 3 / 5 arc length, the blade head is rotated counterclockwise by 2° to obtain the offset blade layer 5.

[0045] References and Supplements Figure 3 This embodiment features an optimized blade layer 6 that simultaneously improves Qmax and Qmin cavitation erosion. The pressure surface profile of the base blade layer 4 is spliced ​​with the suction surface profile of the offset blade layer 5, and the broken part in the middle is bridged with a smooth spline to obtain the optimized blade layer 6.

[0046] By rotating the blade head counterclockwise by a certain angle, an offset blade layer 5 is obtained, thereby reducing the negative angle of attack of the pump under high flow conditions, making the velocity distribution at the head more uniform, which is beneficial to improving cavitation at high flow rates. On this basis, by bridging and splicing the basic blade layer 4 and the offset blade layer 5, the blade inlet angle can be further increased, thereby reducing blade bending, increasing the blade inlet flow area, reducing blade displacement, and thus improving the cavitation performance of the pump under different flow rates, ensuring the working performance of the pump.

[0047] Reference Appendix Figure 4The bridging curves include spline curves a, b, c, and d, which are distributed sequentially in the regions L1, L2, L3, and L4 in the rectangular coordinate system. Fitting the four contour lines yields the following equation:

[0048] Spline curve a: y = 0.3628x 2 +55.584x+2158.8;

[0049] Spline curve b: y = 3.0026x 2 +452.99x+17116;

[0050] Spline curve c: y = 25.881x 2 +3906.8x+147460;

[0051] Spline curve d: y = 11.659x 3 +2629.6x 2 +197702x+5E+06.

[0052] The beneficial effects of this embodiment are that the biased blade layer 5 disperses the high-pressure area at the inlet side, the optimized blade layer 6 improves the local velocity distribution, and the bridging curve eliminates flow separation. The three work together to reduce the probability of cavitation generation. The integrated casting, segmented bridging curve, and composite blade design enhance fatigue resistance and adapt to high speed and high head conditions. The continuous transition of the blade surface and the curvature matching design reduce energy loss and improve the efficiency of the pump.

[0053] Example 4

[0054] In this embodiment, the impeller for improving the cavitation performance of the water pump turbine includes an upper crown 2, a lower ring 1, and optimized blades 3. The optimized blades 3 include a basic blade layer 4, an offset blade layer 5, and an optimized blade layer 6. The optimized blades 3 and the lower ring 1 are cast as a single unit, eliminating weak points in the connection and improving the blades' resistance to cavitation. The offset blade layer 5 is formed by fixing the rear 3 / 5 of the blades of the basic blade layer 4 and using the position of the blade rib line of the front 2 / 5 of the inlet edge near the basic blade layer 4 as a base point, rotating the entire front 2 / 5 of the blades counterclockwise around this base point by a certain angle (3° in this embodiment). The optimized blade layer 6 is formed by splicing the pressure surface profile of the basic blade layer 4 and the suction surface profile of the offset blade layer 5, and bridging the connection point with a transition curve to ensure the smoothness of the blades.

[0055] Continue to refer to the appendix Figure 2Based on the basic blade layer 4, the offset blade layer 5 divides the blade from the upper crown 2 to the lower ring 1 into 11 equally spaced layers (only the two layers closest to the upper crown 2 are shown in the diagram). Along the flow direction, the front and back of the blade are divided into 5 segments of equal arc length, i.e.: A⌒B=B⌒C=C⌒D=D⌒E=E⌒F=l. At 2 / 5 arc length near the inlet edge, the same dividing point on the front and back of the blade is connected, and the midpoint OC=OG is taken. The midpoints of each layer are connected as the rotation axis OO'. After fixing the blade with 3 / 5 arc length, the blade tip is rotated counterclockwise by 3° to obtain the offset blade layer 5.

[0056] Continue to refer to the appendix Figure 3 This embodiment features an optimized blade layer 6 that simultaneously improves Qmax and Qmin cavitation erosion. The pressure surface profile of the base blade layer 4 is spliced ​​with the suction surface profile of the offset blade layer 5, and the broken part in the middle is bridged with a smooth spline to obtain the optimized blade layer 6.

[0057] Continue to refer to the appendix Figure 4 The bridging curves include spline curves a, b, c, and d, which are distributed sequentially in the regions L1, L2, L3, and L4 in the rectangular coordinate system. Fitting the four contour lines yields the following equation:

[0058] Spline curve a: y = 0.3628x 2 +55.584x+2158.8;

[0059] Spline curve b: y = 3.0026x 2 +452.99x+17116;

[0060] Spline curve c: y = 25.881x 2 +3906.8x+147460;

[0061] Spline curve d: y = 11.659x 3 +2629.6x 2 +197702x+5E+06.

[0062] This invention addresses the problem of poor cavitation resistance in existing technologies for blade airfoil optimization under maximum and minimum flow conditions within the pump's operating range. It provides an impeller that improves the cavitation performance of a water pump turbine under pump operating conditions, resulting in a more uniform and stable flow pattern at the impeller inlet during Qmax and Qmin conditions. This improves the uniformity of the inlet velocity distribution, reduces pressure drop and hydraulic losses at the blade inlet, and ultimately improves pump cavitation and impeller cavitation performance. First, by rotating the blade tip counterclockwise by a certain angle, an offset blade layer 5 is obtained, thereby reducing the negative angle of attack under high flow conditions and making the velocity distribution at the tip more uniform, which is beneficial for improving cavitation at high flow rates. Based on this, by bridging and splicing the basic blade layer 4 and the offset blade layer 5, the blade inlet angle can be further increased, thereby reducing blade bending, increasing the blade inlet flow area, and reducing blade displacement. This improves the cavitation performance of the pump under different flow rates and ensures the pump's operational performance.

[0063] The above description is a preferred embodiment of the present utility model, used to illustrate the specific structure and function of the present utility model. It should be noted that, without departing from the principle of the present utility model, those skilled in the art can make foreseeable improvements and modifications to the present utility model, and these improvements and modifications are also within the protection scope of the present utility model.

Claims

1. An impeller for improving the cavitation performance of a water pump turbine, comprising an upper crown and a lower ring arranged correspondingly at the top and bottom, characterized in that, Several optimized blades are fixedly connected to the lower ring. The optimized blades include a basic blade layer and an offset blade layer. The basic blade layer and the offset blade layer are connected through the optimized blade layer. Both the lower ring and the upper crown are trumpet-shaped.

2. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 1, characterized in that, The portion of the offset blade layer near the water inlet edge is formed by rotating the first 2 / 5 of the blades of the base blade layer counterclockwise along the rib line.

3. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 2, characterized in that, The portion of the offset blade layer away from the inlet edge consists of 3 / 5 of the blades of the basic blade layer away from the inlet edge.

4. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 2, characterized in that, The deflection angle of the offset blade layer relative to the base blade layer ranges from 1° to 3°.

5. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 2, characterized in that, The optimized blade layer is formed by splicing the pressure surface profile of the basic blade layer and the suction surface profile of the offset blade layer.

6. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 5, characterized in that, The optimized blade layer is connected to the basic blade layer and the offset blade layer via bridging curves.

7. The impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 6, characterized in that, The bridging curves include spline curves a, b, c, and d.

8. An impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to claim 7, characterized in that, The spline curves a, b, c, and d satisfy the following equations: Spline curve a: y = 0.3628x 2 + 55.584x + 2158.8; Spline curve b: y = 3.0026x 2 + 452.99x + 17116; Spline curve c: y = 25.881x 2 + 3906.8x + 147460; Spline curve d: y = 11.659x 3 + 2629.6x 2 + 197702x + 5E+06.

9. An impeller for improving the cavitation performance of a water pump turbine under pump operating conditions according to any one of claims 1 to 8, characterized in that, The optimized blade and the lower ring are integrally cast.

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