Hyperbolic mixed flow runner blade, preparation method and mixed flow runner

Abstract

The present invention discloses a hyperbolic mixed flow runner blade, a preparation method and a mixed flow runner, belonging to the technical field of water turbines. The hyperbolic mixed flow runner blade comprises a blade head and a blade tail, wherein the blade head and the blade tail are integrally formed, and the blade head is a gradient type, wherein the blade head comprises an upper gradient section, a middle gradient section and a lower gradient section, wherein the upper gradient section, the middle gradient section and the lower gradient section are integrally formed head to tail in sequence. The present invention obtains the maximum thickness distribution law of the blade inlet airfoil section by comprehensively considering the unit operating parameters and the runner blade inlet geometric parameters, and can effectively improve the flow state of the blade inlet, is suitable for large head amplitude variation and wide load operation requirements, improves the flow uniformity of the runner inlet between the upper crown and the lower ring under biased working conditions, reduces the pressure pulsation value of the bladeless area under biased working conditions, improves the overall rigidity level of the runner, and improves the operating stability of the unit.

Description

Technical Field

[0001] The present invention relates to the technical field of water turbines, and in particular to a hyperbolic Francis runner blade, a preparation method and a Francis runner. Background Art

[0002] In recent years, new energy sources such as wind power and photovoltaic power have developed rapidly. However, due to the inflexibility of these new energy sources, conventional hydropower units are becoming increasingly important in ensuring the safety and stability of the power grid. Both power grid dispatchers and power station manufacturers require hydropower units to have a wide, efficient and stable operating range to adapt to peak load and frequency regulation.

[0003] The existing mixed flow turbine is a single-regulating turbine because its runner is fixed-blade. When the unit is running away from the optimal point of the turbine, the impact flow at the runner inlet and the circulation at the runner outlet will produce complex flow disturbance phenomena such as vortex separation, tailwater vortex, blade channel vortex, Karman vortex street, secondary flow or runner outlet return flow. For turbines with large head and variable amplitude, the more it deviates from the optimal working condition, the more serious the flow separation is, and an obvious low-pressure area is formed at the blade head, especially near the back of the blade and the lower ring, inducing the appearance of cavitation at the blade head, and the cavitation is more serious, which is easy to cause cavitation and erosion damage of the blade. Relevant research shows that optimizing the geometric parameter distribution of the runner blade inlet and the blade head airfoil is conducive to suppressing the flow separation at the back of the runner blade inlet, and is more suitable for the flow at the active guide vane outlet, thereby delaying the initiation and development of the blade channel vortex caused by the flow separation at the back of the runner blade in the small flow area, reducing the cavitation level at the blade head, and thus widening the efficient and stable operation area of ​​the unit. At the same time, the overall rigidity level of the real machine runner is closely related to the irregular distribution of the runner blade airfoil thickness. How to effectively avoid the occurrence of cracks at the connection between the upper crown and the lower ring through the special runner blade airfoil thickness regularity design requires the best matching of the operating parameters and geometric parameters of the wide-load running unit. Therefore, it is very important to design and develop a Francis turbine blade head that can adapt to the requirements of large head amplitude and wide load operation.

[0004] A Chinese patent document with publication number CN113266504A and publication date August 17, 2021 discloses a mixed flow turbine with bionic tadpole-shaped blades, including a volute, with fixed guide vanes and movable guide vanes installed downstream of the volute, a runner installed at the outlet of the movable guide vane, a tailwater pipe installed below the runner, and bionic tadpole-shaped blades installed in the runner.

[0005] The Francis turbine with bionic tadpole blades disclosed in the patent document increases the thickness of the runner inlet blades, reduces the incoming flow angle, reduces the separation vortex strength, increases the pressure at the vortex center, and reduces the area of ​​the low-speed zone and the low-pressure zone by designing the bionic tadpole shape of the runner blades. However, the thickness distribution of the bionic tadpole blades is determined by defining a polynomial function related to the streamline position, which is only applicable to runners with specific parameter levels. The design of the turbine runner requires the input of external parameters, such as the head section of the hydropower station, the output level of the unit, the size of the head amplitude, and the stability index requirements, which will affect the determination of geometric parameters, such as the relative guide vane height, the nominal diameter of the runner, and the length of the runner blades, and then affect the range of the streamline position defined in the above patent document. Therefore, the accuracy of the thickness distribution of the designed bionic tadpole blades is easily affected, affecting the flow uniformity between the upper crown and the lower ring at the runner inlet under biased conditions, as well as the overall rigidity level of the runner, and cannot be applied to large head amplitude and wide load operation requirements. Summary of the invention

[0006] In order to overcome the defects of the above-mentioned prior art, the present invention provides a hyperbolic mixed flow impeller blade, a preparation method and a mixed flow impeller. The present invention obtains the maximum thickness distribution law of the blade inlet airfoil section by comprehensively considering the unit operating parameters and the impeller blade inlet geometric parameters, which can effectively improve the flow state at the blade inlet, is suitable for large head amplitude variation and wide load operation requirements, improves the flow uniformity between the upper crown and the lower ring at the impeller inlet under biased conditions, reduces the pressure pulsation value of the bladeless area under biased conditions, improves the overall rigidity level of the impeller, and improves the operating stability of the unit.

[0007] The present invention is achieved through the following technical solutions:

[0008] A hyperbolic mixed flow runner blade comprises a blade head and a blade tail, wherein the blade head and the blade tail are integrally formed, the blade head is a gradient type, and the blade head comprises an upper gradient section, a middle gradient section and a lower gradient section, wherein the upper gradient section, the middle gradient section and the lower gradient section are integrally formed end to end in sequence.

[0009] The blade head is gradually changed in space, specifically, the blade head airfoil section of the upper gradual section near the upper crown is thick, the blade head airfoil section of the lower gradual section near the lower ring is thick, and the blade head airfoil section of the middle gradual section is thin.

[0010] The gradient means that the maximum thickness distribution of the airfoil section at the blade head shows thick upper crown and lower ring in the span direction, and thin in the middle.

[0011] The maximum thickness refers to the maximum value of the distance between the front profile line of the blade head airfoil section and the blade bone line or the maximum value of the distance between the back profile line of the blade head airfoil section and the blade bone line.

[0012] The span direction refers to the height direction of the blade.

[0013] The upper transition section refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0≤ When the blade head is less than 0.35, the middle gradient section is located between the upper gradient section and the lower gradient section. The middle gradient section refers to the position of the axial projection of the airfoil section of the blade head in the span direction of 0.35≤ ≤0.75 for the blade head, the lower gradient section refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0.75< The blade head is ≤1.

[0014] The maximum thickness of the airfoil section of the blade head includes the maximum thickness of the front airfoil section and the maximum thickness of the back airfoil section.

[0015] The maximum thickness of the front airfoil section refers to the maximum value of the distance between the front profile line of each airfoil section of the blade and the blade bone line.

[0016] The maximum thickness of the back airfoil section refers to the maximum value of the distance between the back profile line of each airfoil section of the blade and the blade bone line.

[0017] The maximum thickness of the front airfoil section is calculated by formula 1;

[0018] Formula 1;

[0019] in, is the maximum thickness of the front airfoil section, is the span direction, that is, the position of each blade head airfoil section relative to the upper crown, is the maximum water head, is the minimum water head, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade inlet placement angle, is the blade inlet wrap angle, is the inlet radius of the blade head airfoil section, is the optimal unit speed, is the maximum unit speed.

[0020] The maximum thickness of the back airfoil section is calculated by formula 2;

[0021] Formula 2;

[0022] in, is the maximum thickness of the back airfoil section, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the minimum unit speed.

[0023] The unit speed is calculated by formula 3;

[0024] Formula 3;

[0025] in, is the unit speed, is the rotation speed, is the nominal diameter of the runner inlet, For the water head.

[0026] The connection between the upper gradient section and the middle gradient section is a smooth transition.

[0027] The connection between the middle gradient section and the lower gradient section is a smooth transition.

[0028] The maximum thickness of the upper gradient section is greater than the maximum thickness of the lower gradient section.

[0029] The maximum thickness of the lower gradient section is greater than the maximum thickness of the middle gradient section.

[0030] A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0031] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0032] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0033] S3. A gradient blade head is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail and the gradient blade head are integrally formed.

[0034] In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

[0035] The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

[0036] The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

[0037] In S1, the blade inlet geometric parameters include the guide vane height, the inlet radius of the blade head airfoil section, the blade inlet wrap angle and the blade inlet placement angle.

[0038] In S2, the distribution ratio refers to the ratio of the length of each airfoil section of the blade along the airfoil flow direction of the blade to the airfoil length of the blade.

[0039] In S2, the distribution ratio includes the distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil and the distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil.

[0040] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0041] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of the back side of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0042] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil is calculated by formula 4;

[0043] Formula 4;

[0044] in, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade airfoil length, is the span direction, that is, the position of each blade head airfoil section relative to the upper crown, is the coefficient, and its value is , is the guide vane height, is the runner throat diameter, is the blade inlet placement angle, is the maximum water head, is the minimum water head, is the rated unit flow rate, is the optimal unit flow rate.

[0045] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil is calculated by formula 5;

[0046] Formula 5;

[0047] in, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the coefficient, and its value is .

[0048] The unit flow rate is calculated by formula 6;

[0049] Formula 6;

[0050] in, is the unit flow rate, For flow.

[0051] A mixed flow runner comprises an upper crown and a lower ring, wherein a plurality of hyperbolic mixed flow runner blades are arranged between the upper crown and the lower ring.

[0052] The number of the hyperbolic mixed flow runner blades is 13-17, and the hyperbolic mixed flow runner blades are evenly distributed on the upper crown in a spiral shape.

[0053] The beneficial effects of the present invention are mainly manifested in the following aspects:

[0054] 1. The present invention obtains the maximum thickness distribution law of the blade inlet airfoil section by comprehensively considering the unit operating parameters and the runner blade inlet geometric parameters, which can effectively improve the flow state at the blade inlet, is suitable for large head amplitude and wide load operation requirements, improves the flow uniformity between the upper crown and the lower ring at the runner inlet under biased conditions, reduces the pressure pulsation value of the bladeless area under biased conditions, improves the overall rigidity level of the runner, and improves the operating stability of the unit.

[0055] 2. In the present invention, the maximum thickness distribution law of the gradient blade head can well adapt to the large head variable amplitude operation, effectively reduce the incoming flow angle, increase the adaptability of the impeller to the incoming flow, guide the water flow to flow in more smoothly, reduce the internal vortex caused by the blade inlet flow separation, improve the impeller operation efficiency, and reduce the possibility of cavitation near the back of the blade inlet and the lower ring.

[0056] 3. The present invention can effectively reduce the pressure pulsation value of the bladeless area under biased operating conditions and significantly expand the stable operating range of the unit.

[0057] 4. In the present invention, the maximum thickness of the upper gradient section is greater than the maximum thickness of the lower gradient section. According to engineering experience and the actual operation of the power station turbine, the risk of cracks occurring at the connection between the blade and the upper crown is higher than that at the connection between the blade and the lower ring of the runner. Therefore, by setting the maximum thickness of the upper gradient section to be greater than the maximum thickness of the lower gradient section, the overall thickness of the upper crown airfoil section is increased, thereby improving the rigidity level and fatigue damage resistance of the runner.

[0058] 5. In the present invention, the maximum thickness of the lower gradient section is greater than the maximum thickness of the middle gradient section, and in the spanwise direction, the maximum thickness of the middle gradient section is less than the maximum thickness of the lower gradient section, which can avoid disturbing the uniformity of the incoming flow and reduce the pressure pulsation in the bladeless area.

[0059] 6. The present invention defines the maximum thickness distribution law of the blade airfoil head in different span directions, which is suitable for the design of runners with different head sections and different optimal unit parameter levels, and has better applicability.

[0060] 7. Compared with the current turbine runner design scheme of old power stations, the present invention adopts a gradient blade head maximum thickness distribution law under the same parameter level conditions of the runner, and the airfoil thickness at the upper crown and lower ring is increased, which can improve the overall rigidity level and fatigue damage resistance of the runner, and effectively reduce the risk of cracks in the runner.

[0061] 8. The present invention has good adaptability to the flow from the movable guide vane outlet at any guide vane height, can reduce the large pressure gradient change inside the impeller caused by the flow separation on the back side of the blade inlet, and can initiate the blade vortex in the small load area. The blade vortex development phenomenon can be further away from the long-term stable operation area, thereby ensuring the stability of the impeller operation.

[0062] 9. In the present invention, since the flow separation phenomenon at the back side of the turbine blade inlet with a low head section and a large guide vane height is very sensitive to the change of the unit speed, a gradient blade head maximum thickness distribution law is adopted, which can make the flow separation line at the back side of the turbine further away from the normal operating range, which is beneficial to ensuring the reliability of the runner operation.

[0063] 10. The present invention further increases the airfoil thickness at the upper crown and the lower ring, thereby greatly improving the rigidity level of the runner and further reducing the risk of cracks in the runner.

[0064] 11. The present invention fully considers the limitations of turbine design boundaries of different head sections, different operating ranges and optimal unit parameter levels, further enhances the adaptability to incoming flow, reduces unstable flow in non-optimal operating areas, and can meet the current operating requirements of wide head amplitude and wide load of hydropower stations, thereby improving the flexibility of peak and frequency regulation of power stations.

[0065] 12. In the present invention, since the lower the water head is and the higher the guide vane height is, the greater the flow difference in the spanwise direction of the water flow from the movable guide vane outlet to the runner inlet is, a specific design of the runner blade head can effectively increase the adaptability to the incoming flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0067] Figure 1 It is a schematic structural diagram of a hyperbolic mixed flow runner blade of the present invention;

[0068] Figure 2 It is a schematic diagram of the axial projection of the airfoil section of the hyperbolic mixed flow runner blade head of the present invention;

[0069] Figure 3 It is a schematic diagram of the airfoil section of the hyperbolic mixed flow runner blade head of the present invention;

[0070] Figure 4 It is a schematic structural diagram of a hyperbolic mixed flow runner blade of the present invention;

[0071] Figure 5 It is a structural schematic diagram of the mixed flow runner of the present invention;

[0072] Figure 6 for Figure 4 Schematic diagram of the maximum thickness change of the blade head at the middle viewing angle A;

[0073] Figure 7 for Figure 4 A partial enlarged view of point C in the middle;

[0074] Markings in the figure: 1, blade head, 2, blade tail, 3, upper gradient section, 4, middle gradient section, 5, lower gradient section, 6, upper crown, 7, lower ring;

[0075] is the spanwise direction, i.e. the position of each blade head airfoil section relative to the upper crown; The blade inlet placement angle; is the blade inlet wrap angle; is the inlet radius of the airfoil section at the blade head; is the nominal diameter of the runner inlet; is the runner throat diameter; is the guide vane height; is the maximum thickness of the front airfoil section; The length of the maximum thickness of each airfoil section of the blade along the airfoil flow direction; is the maximum thickness of the back airfoil section; The length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction; is the blade airfoil length. DETAILED DESCRIPTION

[0076] Example 1

[0077] See also Figure 1-Figure 7 A hyperbolic mixed flow runner blade comprises a blade head 1 and a blade tail 2, wherein the blade head 1 and the blade tail 2 are integrally formed, the blade head 1 is a gradient type, and the blade head 1 comprises an upper gradient section 3, a middle gradient section 4 and a lower gradient section 5, wherein the upper gradient section 3, the middle gradient section 4 and the lower gradient section 5 are integrally formed head to tail in sequence.

[0078] This embodiment is the most basic implementation method. By comprehensively considering the unit operating parameters and the geometric parameters of the runner blade inlet, the maximum thickness distribution law of the blade inlet airfoil section is obtained, which can effectively improve the flow state at the blade inlet, is suitable for large head amplitude and wide load operation requirements, improves the flow uniformity at the runner inlet between the upper crown 6 and the lower ring 7 under biased conditions, reduces the pressure pulsation value of the bladeless area under biased conditions, improves the overall rigidity level of the runner, and improves the operating stability of the unit.

[0079] Example 2

[0080] See also Figure 1-Figure 7 A hyperbolic mixed flow runner blade comprises a blade head 1 and a blade tail 2, wherein the blade head 1 and the blade tail 2 are integrally formed, the blade head 1 is a gradient type, and the blade head 1 comprises an upper gradient section 3, a middle gradient section 4 and a lower gradient section 5, wherein the upper gradient section 3, the middle gradient section 4 and the lower gradient section 5 are integrally formed head to tail in sequence.

[0081] Preferably, the blade head 1 is gradually changed in space, specifically, the blade head airfoil cross-section of the upper gradual section 3 near the upper crown 6 is thick, the blade head airfoil cross-section of the lower gradual section 5 near the lower ring 7 is thick, and the blade head airfoil cross-section of the middle gradual section 4 is thin.

[0082] This embodiment is a preferred implementation method. The distribution law of the maximum thickness of the gradient blade head can well adapt to the large head variable amplitude operation, effectively reduce the incoming flow angle, increase the adaptability of the impeller to the incoming flow, guide the water flow to flow in more smoothly, reduce the internal vortex caused by the blade inlet flow separation, improve the impeller operation efficiency, and reduce the possibility of cavitation near the back of the blade inlet and the lower ring 7.

[0083] Example 3

[0084] See also Figure 1-Figure 7 A hyperbolic mixed flow runner blade comprises a blade head 1 and a blade tail 2, wherein the blade head 1 and the blade tail 2 are integrally formed, the blade head 1 is a gradient type, and the blade head 1 comprises an upper gradient section 3, a middle gradient section 4 and a lower gradient section 5, wherein the upper gradient section 3, the middle gradient section 4 and the lower gradient section 5 are integrally formed head to tail in sequence.

[0085] The blade head 1 is gradually changed in space, specifically, the blade head airfoil section of the upper gradual section 3 near the upper crown 6 is thick, the blade head airfoil section of the lower gradual section 5 near the lower ring 7 is thick, and the blade head airfoil section of the middle gradual section 4 is thin.

[0086] The gradual change means that the maximum thickness distribution of the airfoil section at the blade head shows that the upper crown 6 and the lower ring 7 are thick, and the middle is thin in the span direction.

[0087] The maximum thickness refers to the maximum value of the distance between the front profile line of the blade head airfoil section and the blade bone line or the maximum value of the distance between the back profile line of the blade head airfoil section and the blade bone line.

[0088] The span direction refers to the height direction of the blade.

[0089] This embodiment is another preferred implementation method, which can effectively reduce the pressure pulsation value of the bladeless area under abnormal working conditions and significantly expand the stable operation range of the unit.

[0090] Example 4

[0091] See also Figure 1-Figure 7 A hyperbolic mixed flow runner blade comprises a blade head 1 and a blade tail 2, wherein the blade head 1 and the blade tail 2 are integrally formed, the blade head 1 is a gradient type, and the blade head 1 comprises an upper gradient section 3, a middle gradient section 4 and a lower gradient section 5, wherein the upper gradient section 3, the middle gradient section 4 and the lower gradient section 5 are integrally formed head to tail in sequence.

[0092] The blade head 1 is gradually changed in space, specifically, the blade head airfoil section of the upper gradual section 3 near the upper crown 6 is thick, the blade head airfoil section of the lower gradual section 5 near the lower ring 7 is thick, and the blade head airfoil section of the middle gradual section 4 is thin.

[0093] The gradual change means that the maximum thickness distribution of the airfoil section at the blade head shows that the upper crown 6 and the lower ring 7 are thick, and the middle is thin in the span direction.

[0094] The maximum thickness refers to the maximum value of the distance between the front profile line of the blade head airfoil section and the blade bone line or the maximum value of the distance between the back profile line of the blade head airfoil section and the blade bone line.

[0095] The span direction refers to the height direction of the blade.

[0096] Further preferably, the upper transition section 3 specifically refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0≤ <0.35, the middle gradient section 4 is located between the upper gradient section 3 and the lower gradient section 5, and the middle gradient section 4 refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0.35≤ ≤0.75 for the blade head, the lower gradient section 5 refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0.75< The blade head is ≤1.

[0097] The maximum thickness of the airfoil section of the blade head includes the maximum thickness of the front airfoil section and the maximum thickness of the back airfoil section.

[0098] The maximum thickness of the front airfoil section refers to the maximum value of the distance between the front profile line of each airfoil section of the blade and the blade bone line.

[0099] The maximum thickness of the back airfoil section refers to the maximum value of the distance between the back profile line of each airfoil section of the blade and the blade bone line.

[0100] The maximum thickness of the front airfoil section is calculated by formula 1;

[0101] Formula 1;

[0102] in, is the maximum thickness of the front airfoil section, is the spanwise direction, i.e. the position of each blade head airfoil section relative to the upper crown 6, is the maximum water head, is the minimum water head, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade inlet placement angle, is the blade inlet wrap angle, is the inlet radius of the blade head airfoil section, is the optimal unit speed, is the maximum unit speed.

[0103] The maximum thickness of the back airfoil section is calculated by formula 2;

[0104] Formula 2;

[0105] in, is the maximum thickness of the back airfoil section, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the minimum unit speed.

[0106] The unit speed is calculated by formula 3;

[0107] Formula 3;

[0108] in, is the unit speed, is the rotation speed, is the nominal diameter of the runner inlet, For the water head.

[0109] The connection between the upper gradient section 3 and the middle gradient section 4 is a smooth transition.

[0110] The connection between the middle gradient section 4 and the lower gradient section 5 is a smooth transition.

[0111] The maximum thickness of the upper gradient section 3 is greater than the maximum thickness of the lower gradient section 5 .

[0112] The maximum thickness of the lower gradient section 5 is greater than the maximum thickness of the middle gradient section 4 .

[0113] This embodiment is another preferred implementation mode. The maximum thickness of the upper gradient section 3 is greater than the maximum thickness of the lower gradient section 5. According to engineering experience and the actual operation of the power station turbine, the risk of cracks occurring at the connection between the blade and the upper crown 6 is higher than that at the connection between the blade and the lower ring 7 of the runner. Therefore, by setting the maximum thickness of the upper gradient section 3 to be greater than the maximum thickness of the lower gradient section 5, the overall thickness of the airfoil section of the upper crown 6 is increased, thereby improving the rigidity level and fatigue damage resistance of the runner.

[0114] The maximum thickness of the lower gradient section 5 is greater than the maximum thickness of the middle gradient section 4. In the spanwise direction, the maximum thickness of the middle gradient section 4 is less than the maximum thickness of the lower gradient section 5, which can avoid disturbing the uniformity of the incoming flow and reduce the pressure pulsation in the bladeless area.

[0115] The maximum thickness distribution law of the blade airfoil head in different span directions is defined, which is suitable for the runner design with different head sections and different optimal unit parameter levels and has better applicability.

[0116] Example 5

[0117] See also Figure 1-Figure 7 A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0118] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0119] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0120] S3. A gradient blade head 1 is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail 2 and the gradient blade head 1 are integrally formed.

[0121] This embodiment is another preferred implementation method. Compared with the current turbine runner design scheme of old power stations, under the same parameter level conditions of the runner, a gradient blade head 1 maximum thickness distribution law is adopted, and the airfoil thickness at the upper crown 6 and the lower ring 7 is increased, which can improve the overall rigidity level and fatigue damage resistance of the runner, and effectively reduce the risk of cracks in the runner.

[0122] Example 6

[0123] See also Figure 1-Figure 7 A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0124] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0125] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0126] S3. A gradient blade head 1 is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail 2 and the gradient blade head 1 are integrally formed.

[0127] In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

[0128] The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

[0129] The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

[0130] The present embodiment is another preferred implementation mode, which has good adaptability to the inflow from the movable guide vane outlet at any guide vane height, can reduce the large pressure gradient changes inside the impeller caused by the flow shedding on the back side of the blade inlet, and can initiate the blade path vortex in the small load area. The blade path vortex development phenomenon can be further away from the long-term stable operation area, thereby ensuring the stability of the impeller operation.

[0131] Example 7

[0132] See also Figure 1-Figure 7 A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0133] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0134] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0135] S3. A gradient blade head 1 is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail 2 and the gradient blade head 1 are integrally formed.

[0136] In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

[0137] The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

[0138] The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

[0139] In S1, the blade inlet geometric parameters include the guide vane height, the inlet radius of the blade head airfoil section, the blade inlet wrap angle and the blade inlet placement angle.

[0140] In S2, the distribution ratio refers to the ratio of the length of each airfoil section of the blade along the airfoil flow direction of the blade to the airfoil length of the blade.

[0141] In S2, the distribution ratio includes the distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil and the distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil.

[0142] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0143] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of the back side of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0144] This embodiment is another preferred implementation method. Since the flow separation phenomenon on the back side of the turbine blade inlet with a low head section and a large guide vane height is very sensitive to the change of the unit speed, the maximum thickness distribution law of the gradient blade head 1 is adopted to make the flow separation line on the back side of the turbine further away from the normal operating range, which is beneficial to ensure the reliability of the runner operation.

[0145] Example 8

[0146] See also Figure 1-Figure 7 A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0147] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0148] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0149] S3. A gradient blade head 1 is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail 2 and the gradient blade head 1 are integrally formed.

[0150] In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

[0151] The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

[0152] The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

[0153] In S1, the blade inlet geometric parameters include the guide vane height, the inlet radius of the blade head airfoil section, the blade inlet wrap angle and the blade inlet placement angle.

[0154] In S2, the distribution ratio refers to the ratio of the length of each airfoil section of the blade along the airfoil flow direction of the blade to the airfoil length of the blade.

[0155] In S2, the distribution ratio includes the distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil and the distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil.

[0156] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0157] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of the back side of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0158] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil is calculated by formula 4;

[0159] Formula 4;

[0160] in, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade airfoil length, is the spanwise direction, i.e. the position of each blade head airfoil section relative to the upper crown 6, is the coefficient, and its value is , is the guide vane height, is the runner throat diameter, is the blade inlet placement angle, is the maximum water head, is the minimum water head, is the rated unit flow rate, is the optimal unit flow rate.

[0161] This embodiment is another preferred implementation mode. Since the airfoil thickness at the upper crown 6 and the lower ring 7 is further relatively increased, the rigidity level of the runner is greatly improved, which can further reduce the risk of cracks in the runner.

[0162] Example 9

[0163] See also Figure 1-Figure 7 A method for preparing a hyperbolic mixed flow runner blade comprises the following steps:

[0164] S1. Obtaining unit operating parameters and blade inlet geometric parameters;

[0165] S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil;

[0166] S3. A gradient blade head 1 is processed according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail 2 and the gradient blade head 1 are integrally formed.

[0167] In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

[0168] The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

[0169] The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

[0170] In S1, the blade inlet geometric parameters include the guide vane height, the inlet radius of the blade head airfoil section, the blade inlet wrap angle and the blade inlet placement angle.

[0171] In S2, the distribution ratio refers to the ratio of the length of each airfoil section of the blade along the airfoil flow direction of the blade to the airfoil length of the blade.

[0172] In S2, the distribution ratio includes the distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil and the distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil.

[0173] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0174] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of the back side of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

[0175] The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil is calculated by formula 4;

[0176] Formula 4;

[0177] in, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade airfoil length, is the spanwise direction, i.e. the position of each blade head airfoil section relative to the upper crown 6, is the coefficient, and its value is , is the guide vane height, is the runner throat diameter, is the blade inlet placement angle, is the maximum water head, is the minimum water head, is the rated unit flow rate, is the optimal unit flow rate.

[0178] The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil is calculated by formula 5;

[0179] Formula 5;

[0180] in, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the coefficient, and its value is .

[0181] The unit flow rate is calculated by formula 6;

[0182] Formula 6;

[0183] in, is the unit flow rate, For flow.

[0184] This embodiment is another preferred implementation method, which fully takes into account the limitations of the turbine design boundaries of different head sections, different operating ranges and optimal unit parameter levels, further enhances the adaptability to incoming flow, and reduces unstable flow in non-optimal operating areas, thereby meeting the current operating requirements of hydropower stations with wide head variations and wide loads, and improving the flexibility of peak and frequency regulation of power stations.

[0185] Example 10

[0186] See also Figure 1-Figure 7A mixed flow runner comprises an upper crown 6 and a lower ring 7, wherein a plurality of hyperbolic mixed flow runner blades are arranged between the upper crown 6 and the lower ring 7.

[0187] There are 15 hyperbolic mixed flow runner blades, which are evenly distributed on the upper crown 6 in a spiral shape.

[0188] This embodiment is the best implementation method. Since the lower the water head and the higher the guide vane height, the greater the flow difference in the span direction of the water flow from the movable guide vane outlet to the impeller inlet. Therefore, a specific design of the impeller blade head 1 can effectively increase the adaptability to the incoming flow.

[0189] The basic principles of the present invention are as follows:

[0190] The flow pattern at the runner inlet is affected by the operating parameters of the unit and the geometric parameters of the runner. Generally speaking, the higher the guide vane height and the lower the operating head, the greater the difference in the runner inlet flow pattern in the spanwise direction. Therefore, the conventional design method of the maximum thickness of the blade airfoil head with equal thickness distribution and linear change law cannot adapt to the strong angle of attack changes of the inlet flow caused by large flow amplitude and large head amplitude. A large change in pressure gradient will occur at the runner inlet, affecting the downstream flow state, and causing a series of unstable flow phenomena such as blade inlet separation, secondary flow in the runner, blade inlet cavitation, and blade vortex, which will affect the operating stability of the turbine.

[0191] The present invention adopts the maximum thickness distribution law of the gradient blade head 1 to design the change of the maximum thickness of the front and back sides of the airfoil head of the runner blades with different cross-sections, and maintains the thick-thin-thick gradient transition change law in the upper crown 6-middle-lower ring 7, so as to achieve adaptive design for turbines with different head sections, different operating ranges and optimal unit parameter levels, and can better adapt to the difference in the incoming flow in different span directions, reduce the flow separation strength of the blade inlet under the biased working condition, reduce the possibility of cavitation at the blade inlet, and reduce the unstable flow phenomenon of the blade channel vortex.

Claims

1. A hyperbolic mixed flow runner blade, comprising a blade head (1) and a blade tail (2), characterized in that: The blade head (1) and the blade tail (2) are integrally formed, the blade head (1) is of a gradient type, the blade head (1) comprises an upper gradient section (3), a middle gradient section (4) and a lower gradient section (5), and the upper gradient section (3), the middle gradient section (4) and the lower gradient section (5) are integrally formed end to end in sequence; The gradient means that the maximum thickness distribution of the airfoil section at the head of the blade is thick at the top and bottom and thin in the middle in the span direction; The maximum thickness of the airfoil section of the blade head includes the maximum thickness of the front airfoil section and the maximum thickness of the back airfoil section; The maximum thickness of the front airfoil section is calculated by formula 1; Formula 1; in, is the maximum thickness of the front airfoil section, is the spanwise direction, i.e. the position of the airfoil section of each blade head relative to the upper crown (6), is the maximum water head, is the minimum water head, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade inlet placement angle, is the blade inlet wrap angle, is the inlet radius of the blade head airfoil section, is the optimal unit speed, is the maximum unit speed.

2. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The blade head (1) is gradually changed in space, specifically, the blade head airfoil section of the upper gradual change section (3) is thick, the blade head airfoil section of the lower gradual change section (5) is thick, and the blade head airfoil section of the middle gradual change section (4) is thin.

3. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The maximum thickness refers to the maximum value of the distance between the front profile line of the blade head airfoil section and the blade bone line or the maximum value of the distance between the back profile line of the blade head airfoil section and the blade bone line.

4. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The span direction refers to the height direction of the blade.

5. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The upper transition section (3) specifically refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0≤ When the blade tip is less than 0.35, the middle gradient section (4) is located between the upper gradient section (3) and the lower gradient section (5). The middle gradient section (4) refers to the position of the axial projection of the airfoil section of the blade tip in the span direction of 0.35≤ ≤0.75 for the blade head, the lower gradient section refers to the position of the axial projection of the airfoil section of the blade head in the span direction 0.75< The blade head is ≤1.

6. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The maximum thickness of the front airfoil section refers to the maximum value of the distance between the front profile line of each airfoil section of the blade and the blade bone line.

7. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The maximum thickness of the back airfoil section refers to the maximum value of the distance between the back profile line of each airfoil section of the blade and the blade bone line.

8. The hyperbolic mixed flow runner blade according to claim 7, characterized in that: The maximum thickness of the back airfoil section is calculated by formula 2; Formula 2; in, is the maximum thickness of the back airfoil section, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the minimum unit speed.

9. The hyperbolic mixed flow runner blade according to claim 7, characterized in that: The unit speed is calculated by formula 3; Formula 3; in, is the unit speed, is the rotation speed, is the nominal diameter of the runner inlet, For the water head.

10. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The connection between the upper gradient section (3) and the middle gradient section (4) is a smooth transition.

11. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The connection between the middle gradient section (4) and the lower gradient section (5) is a smooth transition.

12. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The maximum thickness of the upper gradient section (3) is greater than the maximum thickness of the lower gradient section (5).

13. The hyperbolic mixed flow runner blade according to claim 1, characterized in that: The maximum thickness of the lower gradient section (5) is greater than the maximum thickness of the middle gradient section (4).

14. A method for preparing a hyperbolic mixed flow runner blade according to claim 1, characterized in that: The following steps are involved: S1. Obtaining unit operating parameters and blade inlet geometric parameters; S2. Calculate and determine the distribution ratio of the maximum thickness of the airfoil section at the blade head along the blade airfoil; S3. A gradient blade head (1) is manufactured according to the distribution ratio of the maximum thickness of the blade head airfoil section along the blade airfoil and the maximum thickness of the blade head airfoil section, and then the blade tail (2) and the gradient blade head (1) are integrally formed.

15. The method for preparing a hyperbolic mixed flow runner blade according to claim 14, characterized in that: In S1, the unit operating parameters include water head amplitude, relative guide vane height, unit speed and unit flow rate, the unit speed includes minimum unit speed, optimal unit speed and maximum unit speed, and the unit flow rate includes rated unit flow rate and optimal unit flow rate.

16. The method for preparing a hyperbolic mixed flow runner blade according to claim 15, characterized in that: The relative guide vane height refers to the ratio of the guide vane height to the runner throat diameter.

17. The method for preparing a hyperbolic mixed flow runner blade according to claim 14, characterized in that: The unit operation parameters also include the ratio of the rated unit flow rate to the optimal unit flow rate.

18. The method for preparing a hyperbolic mixed flow runner blade according to claim 14, characterized in that: In S1, the blade inlet geometric parameters include the guide vane height, the inlet radius of the blade head airfoil section, the blade inlet wrap angle and the blade inlet placement angle.

19. The method for preparing a hyperbolic mixed flow runner blade according to claim 14, characterized in that: In S2, the distribution ratio refers to the ratio of the length of each airfoil section of the blade along the airfoil flow direction of the blade to the airfoil length of the blade.

20. The method for preparing a hyperbolic mixed flow runner blade according to claim 14, characterized in that: In S2, the distribution ratio includes the distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil and the distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil.

21. The method for preparing a hyperbolic mixed flow runner blade according to claim 20, characterized in that: The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

22. The method for preparing a hyperbolic mixed flow runner blade according to claim 20, characterized in that: The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil refers to the ratio of the length of the maximum thickness of the back side of each airfoil section of the blade along the flow direction of the blade airfoil to the length of the blade airfoil.

23. The method for preparing a hyperbolic mixed flow runner blade according to claim 20, characterized in that: The distribution ratio of the maximum thickness of the front airfoil section along the blade airfoil is calculated by formula 4; Formula 4; in, is the length of the maximum thickness of each airfoil section on the front side of the blade along the airfoil flow direction, is the blade airfoil length, is the spanwise direction, i.e. the position of the airfoil section of each blade head relative to the upper crown (6), is the coefficient, and its value is , is the guide vane height, is the runner throat diameter, is the blade inlet placement angle, is the maximum water head, is the minimum water head, is the rated unit flow rate, is the optimal unit flow rate.

24. The method for preparing a hyperbolic mixed flow runner blade according to claim 20, characterized in that: The distribution ratio of the maximum thickness of the back airfoil section along the blade airfoil is calculated by formula 5; Formula 5; in, is the length of the maximum thickness of the back side of each airfoil section of the blade along the airfoil flow direction, is the coefficient, and its value is .

25. The method for preparing a hyperbolic mixed flow runner blade according to claim 23, characterized in that: The unit flow rate is calculated by formula 6; Formula 6; in, is the unit flow rate, For flow.

26. A Francis runner, comprising the hyperbolic Francis runner blade according to claim 1, characterized in that: It also comprises an upper crown (6) and a lower ring (7), wherein a plurality of hyperbolic mixed flow runner blades are arranged between the upper crown (6) and the lower ring (7).

27. The Francis runner according to claim 26, characterized in that: The number of the hyperbolic mixed flow runner blades is 13 to 17, and the hyperbolic mixed flow runner blades are evenly distributed on the upper crown (6) in a spiral shape.

Images