Design method for water outlet edge of runner blade, runner and application

Abstract

The invention discloses a runner blade water outlet edge design method, a runner and application, and belongs to the technical field of water turbines.The runner blade water outlet edge design method comprises the following steps that S1, thickened sections of blade water outlet edges close to an upper crown and a lower ring are determined; s2, calculating and determining water outlet edge thickness distribution in different sections of the water outlet edge of the blade; and S3, smooth transition is conducted on molded lines between different sections of the water outlet edge of the blade. The stress level of the runner blade at the joint of the upper crown and the lower ring can be effectively reduced, the risk that cracks appear at the weld joints of the water outlet edge of the blade and the upper crown and the lower ring is greatly reduced, and then the stable operation range of a water turbine unit can be remarkably widened.

Description

Technical Field

[0001] The present invention relates to the technical field of water turbines, and in particular to a method for designing the outlet edge of a runner blade, a runner and applications thereof. Background Art

[0002] Conventional mixed-flow hydropower units are the main force for peak and frequency regulation of the power grid. After participating in automatic power generation control, even if measures are taken to add reinforcing triangle blocks at the water outlet edge of the upper crown and lower ring, the turbine runner blades will often crack at the welds between the water outlet edge of the blades and the upper crown and lower ring. The power station needs frequent maintenance to repair the runner cracks, which also affects the safe and stable operation of the unit.

[0003] There are many reasons for cracks in runner blades, including external and internal factors, but the problems mainly focus on material selection, design, process, operation and crack repair. For example, since the unit will often operate under partial load conditions and the load changes frequently, the runner will be subjected to large alternating stresses caused by pressure pulsation and load changes, or the resonance of high-frequency flow separation of Karman vortices and blades; casting defects, welding stress and imperfect post-weld heat treatment are the sources of induced cracks; unreasonable selection design and structural design make the runner poor in stability and lack sufficient rigidity margin. When it operates in the vibration zone for a long time, it will cause material fatigue stress, causing cracks in the stress concentration areas of the blades.

[0004] The primary cause of runner cracks is the insufficient ability of the runner blades to withstand dynamic loads. To achieve higher efficiency levels, the runner blades of older power plants currently have a very small and nearly uniform thickness at the water outlet. This results in high stress levels and significant stress concentration in the weld areas of the upper crown and lower ring. Furthermore, during the design phase, it was impossible to quantify the relationship between the thickness variation of the runner blades at the water outlet and the head section, head amplitude, and flow amplitude under specific development conditions, thereby optimizing the runner blade design.

[0005] The Chinese patent document with publication number CN102562415A and publication date July 11, 2012, discloses a water outlet edge of a Francis turbine runner blade, wherein the blade includes a blade body, a stress-reducing triangular block at the upper crown and a stress-reducing triangular block at the lower ring, and an additional triangle is provided near the upper crown and the lower ring; the spatial distance between P1 and P2 is D1 / 40-D1 / 20 and not less than 75mm; D1 is the nominal diameter of the Francis runner inlet, the spatial distance between P1 and P3 is D1 / 30-D1 / 15 and not less than 100mm; the spatial distance between P4 and P5 is 1 / 2 of the spatial distance between P1 and P2; the spatial distance between P4 and P6 is The distance is 1 / 2 of the spatial distance from P1 to P3; the thickness of the stress-reducing triangular block at the upper crown is selected as 0.007-0.008 times D1, and the thickness of the stress-reducing triangular block at the lower ring is selected as 0.005-0.006 times D1; ​​the portion between the water outlet points P3 to P6 of the blade adopts the shape of an anti-Karmán vortex, the thickness of the water outlet edge of the blade is H, the water outlet edge guide angle is 45°, and the water outlet edge guide radius R is 3-4 times H; during the processing and manufacturing of the blade, the water outlet edge shape of the corresponding positions of P2 and P5 is square. After the runner welding is completed, the water outlet edges from P3 to P2 and P6 to P5 should be polished to a smooth transition from the anti-Karmán vortex water outlet edge to the semicircular water outlet edge.

[0006] The water outlet edge of the Francis turbine runner blade disclosed in the patent document is Stress-reducing triangular blocks were added to the upper crown and lower ring of the blades. A Karman vortex-resistant outlet edge shape was adopted, and the thickness and radius of the outlet edge were adjusted. Finite element analysis was used to optimize the blade's structural strength and shape, reducing stress and flow energy. Although the structural strength of the blade outlet edge was improved, cracks were still prone to forming at the welds connecting the outlet edge to the upper crown and lower ring, affecting the unit's stable operating range. Summary of the Invention

[0007] In order to overcome the defects of the above-mentioned prior art, the present invention provides a method for designing the water outlet edge of a runner blade, a runner and its application. The present invention can effectively reduce the stress level of the runner blade at the connection between the upper crown and the lower ring, greatly reducing the risk of cracks occurring at the welds between the water outlet edge of the blade and the upper crown and the lower ring, thereby significantly widening the stable operation range of the turbine unit.

[0008] The present invention is achieved through the following technical solutions: A method for designing the water outlet edge of a runner blade comprises the following steps: S1. Determine the thickened section of the blade outlet edge near the upper crown and lower ring; S2. Calculate and determine the thickness distribution of the water outlet edge of the blade in different sections of the water outlet edge; S3. Make smooth transitions between the contour lines of different sections of the blade outlet edge.

[0009] In the above-mentioned S1, the thickened section of the water outlet edge of the blade includes an arc section of the water outlet edge thickened along the upper crown and an arc section of the water outlet edge thickened along the lower ring.

[0010] The arc length of the waterside interval along the thickened upper crown is calculated by formula 1; Formula 1; in, is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, is the diameter of the blade water inlet side at the lower ring, is the diameter of the blade at the water outlet.

[0011] The arc length of the water outlet section along the thickened lower ring is calculated by formula 2; Formula 2; in, is the arc length of the thickened water outlet section along the lower ring, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0012] In said S2, the different sections of the blade water outlet edge include the blade water outlet edge section close to the upper crown section, the blade water outlet edge middle section and the blade water outlet edge section close to the lower ring section.

[0013] In said S2, the thickness distribution of the blade outlet edge in different sections is as follows: the thickness of the blade outlet edge close to the upper crown section is thick, the thickness of the blade outlet edge middle section is thin, and the thickness of the blade outlet edge close to the lower ring section is thick.

[0014] The thickness of the blade near the upper crown at the water outlet is calculated using Formula 3; Formula 3; in, is the thickness of the blade near the upper crown at the water outlet edge, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the maximum water head, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, The arc length of the water side.

[0015] The thickness of the middle section of the blade outlet edge is calculated by formula 4;

[0016] Formula 4; in, is the thickness of the middle section of the blade at the water outlet, is the rated unit flow rate, is the optimal unit flow rate, is the maximum unit speed, is the minimum unit speed, is the maximum water head, is the high pressure side diameter of the model runner, for According to the real machine high pressure side diameter converted from the scale, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, It is the arc length of the water outlet section along the thickened lower ring.

[0017] The unit speed is calculated by formula 5; Formula 5; in, is the unit speed, is the rotation speed, is the water head, is the diameter of the blade at the water inlet edge at the lower ring.

[0018] The unit flow rate is calculated by formula 6; Formula 6; in, is the unit flow rate, For traffic, is the diameter of the blade water inlet edge at the lower ring, For the water head.

[0019] The thickness of the blade outlet edge near the lower ring section is calculated by formula 7; Formula 7; in, is the thickness of the blade near the lower ring section at the water outlet, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the water side, is the arc length of the thickened water outlet section along the lower ring, is the maximum water head.

[0020] A runner comprises an upper crown and a lower ring, wherein a plurality of runner blades are arranged between the upper crown and the lower ring.

[0021] The runner blade comprises a blade body, a blade water inlet edge and a blade water outlet edge, and the blade water inlet edge, the blade body and the blade water outlet edge are integrally formed.

[0022] The blade water outlet edge includes the blade water outlet edge close to the upper crown section, the blade water outlet edge middle section and the blade water outlet edge close to the lower ring section. The blade water outlet edge close to the upper crown section, the blade water outlet edge middle section and the blade water outlet edge close to the lower ring section are integrally formed.

[0023] The thickness of the blade's water outlet edge close to the upper crown section and the blade's water outlet edge close to the lower ring section are both greater than the thickness of the blade's water outlet edge middle section.

[0024] The invention discloses an application of a water outlet edge of a runner blade, which is suitable for the runner blades of a water turbine.

[0025] The invention discloses an application of a runner, which is suitable for a Francis turbine with a head range of 50-500m.

[0026] The beneficial effects of the present invention are mainly manifested in the following aspects: 1. Compared with the prior art, the present invention can effectively reduce the stress level of the runner blades at the connection between the upper crown and the lower ring, greatly reducing the risk of cracks at the welds between the water outlet edge of the blades and the upper crown and lower ring, thereby significantly widening the stable operating range of the turbine unit. 2. By adopting specific segmented thickening for the water outlet edge of the blade, the present invention effectively reduces the stress level at the connection between the upper crown and the lower ring of the runner blade compared to conventional runners with uniform blade thickness at the water outlet edge. Calculation results show that the maximum reductions in static stress value and dynamic stress amplitude under typical operating conditions within the full load range are 42% and 61%, respectively. See Table 1.

[0027] 3. In the present invention, the thickened section of the water outlet edge of the blade includes an arc section of the water outlet edge thickened along the upper crown and an arc section of the water outlet edge thickened along the lower ring. The thickening is performed on the high stress areas of the water outlet edge of the blade close to the upper crown and the lower ring, which significantly improves the stiffness and fatigue resistance and cavitation damage resistance of the blade at these key positions, and enhances the overall structural reliability of the blade.

[0028] 4. The present invention effectively guides the water flow by precisely controlling the thickness distribution and smooth profile transition of the blade outlet edge, reduces the wake vortex, secondary flow and flow separation phenomena at the blade outlet edge, optimizes the hydraulic performance, reduces hydraulic loss and improves operating efficiency.

[0029] 5. The present invention comprehensively considers the geometric parameters of the runner and the operating parameters of the turbine unit, which are important parameters that actually affect the wide-load operating capability of the turbine unit, and then adopts segmented thickening of the water outlet edge of the runner blades, so that the geometric parameters of the runner and the operating parameters of the turbine unit are well optimized and matched, which is beneficial to reducing the dynamic stress level under partial load.

[0030] 6. The present invention effectively enhances the structural strength and fatigue resistance of the blade edge and improves the operational reliability of the runner by optimizing the thickness distribution of the blade outlet edge and achieving a smooth transition.

[0031] 7. In the present invention, the rigidity level of the runner at the connection between the upper crown and the lower ring is enhanced, which reduces or even avoids the risk of runner cracks caused by fatigue damage to the runner when the turbine unit is running at low load, and effectively improves the operating stability of the unit.

[0032] 8. In the present invention, the water outlet edge of the blade includes a section close to the upper crown of the blade, a middle section of the water outlet edge of the blade, and a section close to the lower ring of the blade. The section close to the upper crown of the blade, the middle section of the water outlet edge of the blade, and the section close to the lower ring of the blade are integrally formed, which not only enhances the fatigue resistance and cavitation resistance of the high stress area to extend the life of the blade, but also effectively suppresses flow separation and vortex through smooth lines, reduces hydraulic loss, and ultimately achieves coordinated optimization of reliability and energy conversion efficiency.

[0033] 9. In the present invention, the thickness of the blade outlet edge near the upper crown section and the blade outlet edge near the lower ring section are both greater than the thickness of the middle section of the blade outlet edge. By thickening the high stress area to enhance fatigue resistance and cavitation resistance, and thinning the middle section of the blade outlet edge to optimize the streamline shape, the hydraulic loss is significantly reduced while ensuring the reliability of the blade structure. This not only suppresses the risk of cracks caused by stress concentration at the end, but also reduces the wake vortex and flow separation at the blade outlet edge, thereby improving the energy conversion efficiency of the runner, and achieving a dual optimization effect of strength and flow state.

[0034] 10. The present invention is suitable for mixed-flow turbines with a head range of 50-500m. Through the differentiated design of zoning the water outlet edge of the blade, within the head range of 50-500m, the thickened water outlet edge of the blade close to the upper crown section and the water outlet edge of the blade close to the lower ring section can effectively resist high stress and cavitation damage, ensure structural reliability, and the thinned middle section of the water outlet edge of the blade can optimize the water flow state, reduce hydraulic loss, and achieve wide-load, efficient and stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments: Figure 1 Schematic diagram of the structure of the runner of the present invention; Figure 2 It is a schematic structural diagram of the runner blade of the present invention; Figure 3 This is a schematic diagram of the thickness distribution of the water outlet edge of the blade of the present invention; Markings in the figure: 1, upper crown, 2, lower ring, 3, blade outlet edge, 4, blade inlet edge, 5, blade outlet edge section close to the upper crown, 6, blade outlet edge middle section, 7, blade outlet edge section close to the lower ring, 8, runner blade, 9, blade body; , the thickness of the blade near the upper crown section at the water outlet, , the length of the arc segment along the thickened waterside of the upper crown, , the thickness of the middle section of the blade at the water outlet, , the arc length of the water outlet section along the thickened lower ring, It is the thickness of the blade's water outlet section close to the lower ring. DETAILED DESCRIPTION

[0036] Example 1 See also Figure 1 A method for designing the water outlet edge of a runner blade comprises the following steps: S1, determining the thickened section of the blade outlet edge 3 near the upper crown 1 and the lower ring 2; S2. Calculate and determine the thickness distribution of the blade outlet edge in three different sections; S3. Smoothly transition the contour lines between the three different sections of the blade outlet edge.

[0037] This embodiment is the most basic implementation method. Compared with the existing technology, it can effectively reduce the stress level of the runner blade 8 at the connection between the upper crown 1 and the lower ring 2, greatly reducing the risk of cracks occurring at the weld between the blade outlet edge 3 and the upper crown 1 and the lower ring 2, thereby significantly widening the stable operation range of the turbine unit. Example 2 See also Figure 1-Figure 3 A method for designing the water outlet edge of a runner blade comprises the following steps: S1, determining the thickened section of the blade outlet edge 3 near the upper crown 1 and the lower ring 2; S2. Calculate and determine the thickness distribution of the blade outlet edge in three different sections; S3. Smoothly transition the contour lines between the three different sections of the blade outlet edge.

[0038] In the above-mentioned S1 , the thickened section of the water outlet edge 3 of the blade includes an arc section of the water outlet edge thickened along the upper crown 1 and an arc section of the water outlet edge thickened along the lower ring 2 .

[0039] The arc length of the thickened waterside arc segment along the upper crown 1 is calculated by formula 1; Formula 1; in, is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0040] The arc length of the thickened water outlet arc along the lower ring 2 is calculated by formula 2; Formula 2; in, is the arc length of the thickened water outlet section along the lower ring, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0041] This embodiment is a preferred implementation method. By adopting specific segmented thickening for the water outlet edge 3 of the blade, the stress level of the runner blade 8 at the connection between the upper crown 1 and the lower ring 2 is effectively reduced compared with the conventional runner with the blade outlet edge 3 of equal thickness. The calculation results show that the maximum reduction in the static stress value and the dynamic stress amplitude under typical working conditions within the full load range is 42% and 61% respectively.

[0042] Example 3 See also Figure 1-Figure 3 A method for designing the water outlet edge of a runner blade comprises the following steps: S1, determining the thickened section of the blade outlet edge 3 near the upper crown 1 and the lower ring 2; S2. Calculate and determine the thickness distribution of the blade outlet edge in three different sections; S3. Smoothly transition the contour lines between the three different sections of the blade outlet edge.

[0043] In the above-mentioned S1 , the thickened section of the water outlet edge 3 of the blade includes an arc section of the water outlet edge thickened along the upper crown 1 and an arc section of the water outlet edge thickened along the lower ring 2 .

[0044] The arc length of the thickened waterside arc segment along the upper crown 1 is calculated by formula 1; Formula 1; in, is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0045] The arc length of the thickened water outlet arc along the lower ring 2 is calculated by formula 2; Formula 2; in, is the arc length of the thickened water outlet section along the lower ring, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0046] In the above-mentioned S2, the different sections of the blade outlet edge 3 include the blade outlet edge section 5 close to the upper crown, the blade outlet edge middle section 6 and the blade outlet edge section 7 close to the lower ring.

[0047] In said S2, the thickness distribution of the water outlet edge in different sections of the blade water outlet edge 3 is as follows: the thickness of the blade water outlet edge close to the upper crown section 5 is thick, the thickness of the blade water outlet edge middle section 6 is thin, and the thickness of the blade water outlet edge close to the lower ring section 7 is thick.

[0048] The thickness of the blade outlet edge near the upper crown section 5 is calculated by formula 3; Formula 3; in, is the thickness of the blade near the upper crown at the water outlet edge, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the maximum water head, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, The arc length of the water side.

[0049] The thickness of the middle section 6 of the blade outlet edge is calculated by formula 4;

[0050] Formula 4; in, is the thickness of the middle section of the blade at the water outlet, is the rated unit flow rate, is the optimal unit flow rate, is the maximum unit speed, is the minimum unit speed, is the maximum water head, is the high pressure side diameter of the model runner, for According to the real machine high pressure side diameter converted from the scale, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, It is the arc length of the water outlet section along the thickened lower ring.

[0051] This embodiment is another preferred implementation method. The thickened section of the water outlet edge 3 of the blade includes an arc section of the water outlet edge thickened along the upper crown 1 and an arc section of the water outlet edge thickened along the lower ring 2. The high stress areas of the water outlet edge 3 of the blade close to the upper crown 1 and the lower ring 2 are thickened, which significantly improves the stiffness and fatigue resistance and cavitation damage resistance of the blade water outlet edge 3 in these key positions, and enhances the overall structural reliability of the blade.

[0052] Example 4 See also Figure 1-Figure 3 A method for designing the water outlet edge of a runner blade comprises the following steps: S1, determining the thickened section of the blade outlet edge 3 near the upper crown 1 and the lower ring 2; S2. Calculate and determine the thickness distribution of the blade outlet edge in three different sections; S3. Smoothly transition the contour lines between the three different sections of the blade outlet edge.

[0053] In the above-mentioned S1 , the thickened section of the water outlet edge 3 of the blade includes an arc section of the water outlet edge thickened along the upper crown 1 and an arc section of the water outlet edge thickened along the lower ring 2 .

[0054] The arc length of the thickened waterside arc segment along the upper crown 1 is calculated by formula 1; Formula 1; in, is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0055] The arc length of the thickened water outlet arc along the lower ring 2 is calculated by formula 2; Formula 2; in, is the arc length of the thickened water outlet section along the lower ring, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

[0056] In the above-mentioned S2, the different sections of the blade outlet edge 3 include the blade outlet edge section 5 close to the upper crown, the blade outlet edge middle section 6 and the blade outlet edge section 7 close to the lower ring.

[0057] In said S2, the thickness distribution of the water outlet edge in different sections of the blade water outlet edge 3 is as follows: the thickness of the blade water outlet edge close to the upper crown section 5 is thick, the thickness of the blade water outlet edge middle section 6 is thin, and the thickness of the blade water outlet edge close to the lower ring section 7 is thick.

[0058] The thickness of the blade outlet edge near the upper crown section 5 is calculated by formula 3; Formula 3; in, is the thickness of the blade near the upper crown at the water outlet edge, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the maximum water head, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, The arc length of the water side.

[0059] The thickness of the middle section 6 of the blade outlet edge is calculated by formula 4;

[0060] Formula 4; in, is the thickness of the middle section of the blade at the water outlet, is the rated unit flow rate, is the optimal unit flow rate, is the maximum unit speed, is the minimum unit speed, is the maximum water head, is the high pressure side diameter of the model runner, for According to the real machine high pressure side diameter converted from the scale, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, It is the arc length of the water outlet section along the thickened lower ring.

[0061] The unit speed is calculated by formula 5; Formula 5; in, is the unit speed, is the rotation speed, is the water head, is the diameter of the blade at the water inlet edge at the lower ring.

[0062] The unit flow rate is calculated by formula 6; Formula 6; in, is the unit flow rate, For traffic, is the diameter of the blade water inlet edge at the lower ring, For the water head.

[0063] The thickness of the blade outlet edge near the lower ring section 7 is calculated by formula 7; Formula 7; in, is the thickness of the blade near the lower ring section at the water outlet, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the water side, is the arc length of the thickened water outlet section along the lower ring, is the maximum water head.

[0064] This embodiment is another preferred implementation method. By precisely controlling the thickness distribution and smooth profile transition of the blade outlet edge 3, the water flow is effectively guided, the wake vortex, secondary flow and flow separation phenomena of the blade outlet edge 3 are reduced, the hydraulic performance is optimized, the hydraulic loss is reduced, and the operating efficiency is improved.

[0065] By comprehensively considering the geometric parameters of the runner and the operating parameters of the turbine unit, which are important parameters that actually affect the wide-load operating capability of the turbine unit, the water outlet edge 3 of the runner blade 8 is thickened in sections, so that the geometric parameters of the runner and the operating parameters of the turbine unit are well optimized and matched, which is beneficial to reducing the dynamic stress level under partial load. Example 5 See also Figure 1 and Figure 2 A runner comprises an upper crown 1 and a lower ring 2, wherein a plurality of runner blades 8 are arranged between the upper crown 1 and the lower ring 2.

[0066] This embodiment is another preferred implementation method. By optimizing the thickness distribution of the blade outlet edge 3 and achieving a smooth transition, the structural strength and fatigue resistance of the blade edge are effectively enhanced, and the operating reliability of the runner is improved.

[0067] Example 6 See also Figure 1 and Figure 2A runner comprises an upper crown 1 and a lower ring 2, wherein a plurality of runner blades 8 are arranged between the upper crown 1 and the lower ring 2.

[0068] The runner blade 8 includes a blade body 9, a blade water inlet edge 4 and a blade water outlet edge 3. The blade water inlet edge 4, the blade body 9 and the blade water outlet edge 3 are integrally formed.

[0069] The blade outlet edge 3 includes a blade outlet edge close to the upper crown section 5, a blade outlet edge middle section 6 and a blade outlet edge close to the lower ring section 7. The blade outlet edge close to the upper crown section 5, the blade outlet edge middle section 6 and the blade outlet edge close to the lower ring section 7 are integrally formed.

[0070] This embodiment is another preferred implementation method. The rigidity level of the runner at the connection between the upper crown 1 and the lower ring 2 is enhanced, which reduces or even avoids the risk of runner cracks caused by fatigue damage to the runner when the turbine unit is running at low load, and effectively improves the operating stability of the unit.

[0071] The blade outlet edge 3 includes the blade outlet edge close to the upper crown section 5, the blade outlet edge middle section 6 and the blade outlet edge close to the lower ring section 7. The blade outlet edge close to the upper crown section 5, the blade outlet edge middle section 6 and the blade outlet edge close to the lower ring section 7 are integrally formed, which not only enhances the fatigue resistance and cavitation resistance of the high stress area to extend the life of the blade, but also effectively suppresses flow separation and vortex through smooth lines, reduces hydraulic loss, and ultimately achieves the coordinated optimization of reliability and energy conversion efficiency.

[0072] Example 7 See also Figure 1-Figure 3 A runner comprises an upper crown 1 and a lower ring 2, wherein a plurality of runner blades 8 are arranged between the upper crown 1 and the lower ring 2.

[0073] The runner blade 8 includes a blade body 9, a blade water inlet edge 4 and a blade water outlet edge 3. The blade water inlet edge 4, the blade body 9 and the blade water outlet edge 3 are integrally formed.

[0074] The blade outlet edge 3 includes a blade outlet edge close to the upper crown section 5, a blade outlet edge middle section 6 and a blade outlet edge close to the lower ring section 7. The blade outlet edge close to the upper crown section 5, the blade outlet edge middle section 6 and the blade outlet edge close to the lower ring section 7 are integrally formed.

[0075] The thickness of the blade outlet edge close to the upper crown section 5 and the blade outlet edge close to the lower ring section 7 are both greater than the thickness of the blade outlet edge middle section 6.

[0076] This embodiment is another preferred implementation method. The thickness of the blade outlet edge near the upper crown section 5 and the blade outlet edge near the lower ring section 7 are both greater than the thickness of the middle section 6 of the blade outlet edge. By thickening the high stress area to enhance fatigue resistance and cavitation resistance, and thinning the middle section 6 of the blade outlet edge to optimize the streamline shape, the hydraulic loss is significantly reduced while ensuring the reliability of the blade structure. This not only suppresses the risk of cracks caused by end stress concentration, but also reduces the wake vortex and flow separation of the blade outlet edge 3, thereby improving the energy conversion efficiency of the runner and achieving a dual optimization effect of strength and flow state.

[0077] Table 1 shows the comparison of the static stress value and dynamic stress amplitude of the runner blade 8 before and after the thickness of the blade outlet edge 3 of the runner blade 8 is improved, with the unit being MPa; wherein: Pr is the rated output of the turbine, 10% of the rated head Pr means that the turbine output is 10% of the rated output under the rated head, 45% of the rated head Pr means that the turbine output is 45% of the rated output under the rated head, and 100% of the rated head Pr means that the turbine output is 100% of the rated output under the rated head.

[0078] Table 1

[0079] The basic principles of the present invention are as follows: For the high-stress and corrosion-prone areas at the welds between the blade outlet edge 3 and the upper crown 1 and lower ring 2, the blade outlet edge 3 is thickened and strengthened in sections to improve structural reliability; the thinnest allowable thickness in the medium and low stress areas is calculated, and the thickness distribution is optimized to reduce wake vortexes and hydraulic losses, thereby optimizing hydraulic performance; and the flow separation caused by sudden thickness changes is eliminated through smooth transition of the profile line to maintain water flow adhesion.

[0080] By seeking the optimal balance between mechanical reliability and hydraulic efficiency, the blade outlet edge is structurally thickened to resist damage, streamlined thinning is used to guide flow, and smooth transition continuous lines are used to stabilize the flow state. Ultimately, while ensuring the blade's anti-fatigue and anti-cavitation capabilities, hydraulic losses are significantly reduced, achieving a synergistic improvement in the runner's strength and efficiency, and improving the runner's overall performance.

Claims

1. A method for designing the water-outlet edge of a runner blade, characterized in that: The following steps are involved: S1. Determine the thickened section of the water outlet edge (3) of the blade near the upper crown (1) and the lower ring (2); S2, calculating and determining the thickness distribution of the water outlet edge of the blade (3) in different sections; S3. Smooth transition of the profiles between different sections of the water outlet edge (3) of the blade.

2. The method for designing the water outlet edge of a runner blade according to claim 1, characterized in that: In the above-mentioned S1, the thickened section of the water outlet edge (3) of the blade includes an arc section of the water outlet edge interval thickened along the upper crown (1) and an arc section of the water outlet edge interval thickened along the lower ring (2).

3. The method for designing the water outlet edge of a runner blade according to claim 2, characterized in that: The arc length of the thickened water outlet arc segment along the upper crown (1) is calculated by formula 1; Formula 1; in, is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

4. The method for designing the water outlet edge of a runner blade according to claim 3, characterized in that: The arc length of the thickened water outlet arc along the lower ring (2) is calculated by formula 2; Formula 2; in, is the arc length of the thickened water outlet section along the lower ring, is the arc length of the water side, is the diameter of the blade water inlet edge at the lower ring, is the diameter of the blade at the water outlet.

5. The method for designing the water outlet edge of a runner blade according to claim 1, characterized in that: In the aforementioned S2, the different sections of the blade outlet edge (3) include a blade outlet edge section close to the upper crown section (5), a blade outlet edge middle section (6), and a blade outlet edge section close to the lower ring section (7).

6. The method for designing the water outlet edge of a runner blade according to claim 5, characterized in that: In the above-mentioned S2, the thickness distribution of the water outlet edge of the blade (3) in different sections is as follows: the thickness of the water outlet edge of the blade close to the upper crown section (5) is thick, the thickness of the middle section (6) of the water outlet edge of the blade is thin, and the thickness of the water outlet edge of the blade close to the lower ring section (7) is thick.

7. The method for designing the water outlet edge of a runner blade according to claim 5, characterized in that: The thickness of the blade outlet edge near the upper crown section (5) is calculated by formula 3; Formula 3; in, is the thickness of the blade near the upper crown at the water outlet edge, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the maximum water head, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, The arc length of the water side.

8. The method for designing the water outlet edge of a runner blade according to claim 5, characterized in that: The thickness of the middle section (6) of the blade outlet edge is calculated by formula 4; Formula 4; in, is the thickness of the middle section of the blade at the water outlet, is the rated unit flow rate, is the optimal unit flow rate, is the maximum unit speed, is the minimum unit speed, is the maximum water head, is the high pressure side diameter of the model runner, for According to the real machine high pressure side diameter converted from the scale, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the thickened waterside section along the upper crown, is the arc length of the water side, It is the arc length of the water outlet section along the thickened lower ring.

9. The method for designing the water outlet edge of a runner blade according to claim 8, characterized in that: The unit speed is calculated by formula 5; Formula 5; in, is the unit speed, is the rotation speed, is the water head, is the diameter of the blade at the water inlet edge at the lower ring.

10. The method for designing the water outlet edge of a runner blade according to claim 8, characterized in that: The unit flow rate is calculated by formula 6; Formula 6; in, is the unit flow rate, For traffic, is the diameter of the blade water inlet edge at the lower ring, For the water head.

11. The method for designing the water outlet edge of a runner blade according to claim 5, characterized in that: The thickness of the blade outlet edge close to the lower ring section (7) is calculated by formula 7; Formula 7; in, is the thickness of the blade near the lower ring section at the water outlet, is the diameter of the blade at the water outlet, is the diameter of the blade at the upper crown, is the ratio of the arc length relative to the crown position to the total arc length of the blade out of the water, , is the arc length of the water side, is the arc length of the thickened water outlet section along the lower ring, is the maximum water head.

12. A rotating wheel comprising an upper crown (1) and a lower ring (2), characterized in that: It also comprises the runner blade outlet edge as claimed in claim 1, wherein a plurality of runner blades (8) are arranged between the upper crown (1) and the lower ring (2).

13. The rotating wheel according to claim 12, characterized in that: The runner blade (8) comprises a blade body (9), a blade water inlet edge (4) and a blade water outlet edge (3), wherein the blade water inlet edge (4), the blade body (9) and the blade water outlet edge (3) are integrally formed.

14. The rotating wheel according to claim 13, characterized in that: The blade water outlet edge (3) comprises a blade water outlet edge close to an upper crown section (5), a blade water outlet edge middle section (6) and a blade water outlet edge close to a lower ring section (7); the blade water outlet edge close to the upper crown section (5), the blade water outlet edge middle section (6) and the blade water outlet edge close to the lower ring section (7) are integrally formed.

15. The rotating wheel according to claim 14, characterized in that: The thickness of the blade outlet edge close to the upper crown section (5) and the blade outlet edge close to the lower ring section (7) are both greater than the thickness of the blade outlet edge middle section (6).

16. An application of a runner blade at the water outlet, characterized by: The runner blade outlet edge as claimed in claim 1 is suitable for the runner blade (8) of a water turbine.

17. An application of a rotating wheel, characterized in that: The runner as claimed in claim 12 is suitable for Francis turbines with a head range of 50-500m.

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