CN117052582A

CN117052582A - Mixed-flow water turbine

Info

Publication number: CN117052582A
Application number: CN202311012175.XA
Authority: CN
Inventors: 王正伟; 黄星星; 李辉楚
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2023-08-11
Filing date: 2023-08-11
Publication date: 2023-11-14

Abstract

The application relates to a mixed-flow water turbine, comprising: a volute and a runner. The runner includes: upper crown, lower ring, a plurality of original blades, a plurality of adjustment blades. In the mixed flow water turbine, the original blades are cut from the outlet edge to the middle streamline of the inlet edge by a certain distance and parallel to the outlet edge, so that the adjusting blades are manufactured, the length of the middle streamline of the original blades is larger than that of the middle streamline of the adjusting blades, the quantity of the plurality of original blades is equal to that of the adjusting blades, the original blades and the adjusting blades are alternately arranged along the circumferential direction of the rotating wheel in sequence, the efficiency of the water turbine is improved, the relative speeds of the blades are uniform, the inner streamline is smooth, the silt resistance and the wear resistance are good, the comprehensive performance of the water turbine is improved, and the abrasion condition of silt to the rotating wheel is improved.

Description

Mixed-flow water turbine

Technical Field

The application relates to the technical field of fluid machinery and engineering equipment, in particular to a mixed-flow water turbine.

Background

Existing hydroelectric turbines include impulse turbines and francis turbines. The impulse turbine is suitable for high water head conditions, especially for water heads greater than 700m, but the impulse turbine has the following disadvantages: firstly, as the impulse turbine runner is exposed out of the water surface and works under the atmospheric pressure, the jet speed of the nozzle and the rotating speed of the bucket runner are high, the single-machine capacity of the impulse turbine is limited by the runner material, and the maximum single-machine capacity of the impulse turbine is 423MW at present; secondly, when the water head is higher than 700m and the sediment content of the river is larger, the sediment abrasion problem of the impulse turbine is serious, and the equipment maintenance period and the service life are greatly shortened.

Therefore, the mixed-flow turbine is operated frequently in a liquid flow containing a large amount of suspended sediment, and the sediment abrasion degree is often the most important factor for determining the maintenance period and the maintenance workload of the mixed-flow turbine. The maintenance period of the mixed-flow water turbine of some power stations with serious sediment abrasion is shortened to one year, and the maintenance period is increased by three times compared with the specified overhaul frequency. Such downtime maintenance would result in loss of manpower and material resources. Sediment almost comes simultaneously with a flood peak of a river, and a water turbine is overhauled in a large scale simultaneously after the flood peak flood period, so that the power supply of an electric power system is stressed, and the production electricity and the life electricity of a user are limited. In the case of a francis turbine, the flow through components of the turbine will promote the local disturbance of the flow and the development of cavitation after being worn, and may further exacerbate the vibration of the turbine. The water leakage amount is increased after the water guide blades are worn, and even the normal shutdown is impossible.

Disclosure of Invention

Based on the above, it is necessary to provide a francis turbine against the problem that the water leakage amount increases after the water guide blades are worn and even the normal stop is impossible.

The mixed flow hydraulic turbine is characterized by comprising a runner and a rotating shaft;

the wheel includes: an upper crown, a lower ring, a plurality of original blades, a plurality of adjustment blades;

the number of the original blades is equal to that of the adjusting blades, and the original blades and the adjusting blades are alternately arranged in turn along the circumferential direction of the rotating wheel; the original blade and the adjusting blade are provided with an inlet edge and an outlet edge, the rotating shaft penetrates through the upper crown and the lower ring, and the outlet edge is close to the rotating shaft relative to the inlet edge; the original blade and the adjusting blade are positioned between the upper crown and the lower ring, and the upper crown and the lower ring are fixed relative to the original blade and the adjusting blade;

defining a line from the midpoint of the inlet edge to the midpoint of the outlet edge as a medial streamline; the length of the intermediate streamline of the original blade is greater than the length of the intermediate streamline of the adjusting blade, and the distance from the outlet edge of the original blade to the rotating shaft is smaller than the distance from the outlet edge of the adjusting blade to the rotating shaft; the distance from the inlet edge of the original blade to the rotating shaft is equal to the distance from the inlet edge of the adjusting blade to the rotating shaft.

In an embodiment, the ratio of the length of the intermediate streamline of the original blade and the intermediate streamline of the adjustment blade is 3: 2. 4: 3. 5:4.

In an embodiment, the ratio of the intermediate streamline of the original blade and the intermediate streamline of the adjustment blade is 5:4.

in an embodiment, the upper surface of the upper crown is provided with an annular protrusion, and a surface of the annular protrusion, which is far away from the lower ring, is provided with a plurality of hanging rings.

In an embodiment, a plurality of the hanging rings are symmetrically arranged along the radial direction of the annular protrusion.

In one embodiment, the nominal tensile strength of the plurality of hanging rings reaches 1200 MPa; the nominal yield strength is 1080 MPa.

In an embodiment, a plurality of pairs of hanging holes corresponding to the hanging rings one by one are formed in the surface, away from the lower ring, of the annular protrusion, each hanging ring is arc-shaped, and two hanging holes of each pair of hanging holes are respectively in threaded fit with two ends of the hanging ring, so that the hanging ring is fixed to the annular protrusion.

In one embodiment, the francis turbine includes: the top cover is positioned on the upper side of the rotating wheel, and the bottom ring is positioned on the lower side of the rotating wheel;

the volute surrounds the rotating wheel, and the side wall of the volute is provided with an open slot so that water flowing in the volute can drive the rotating wheel to rotate around the rotating shaft through the open slot;

the seat ring is positioned between the rotating wheel and the volute, and the outer side of the seat ring is communicated with the open slot;

the upper part of the inner side of the seat ring is connected with the top cover, a first abutting groove is formed in the surface, facing the bottom ring, of the outer side of the top cover, the inner side of the upper part of the seat ring is abutted with the inner wall, close to the rotating wheel, of the first abutting groove, and smooth transition is carried out between the inner wall, close to the rotating wheel, of the first abutting groove and the surface, facing the bottom ring, of the top cover;

the lower part of the inner side of the seat ring is connected with the bottom ring, a second abutting groove is formed in the outer side of the bottom ring towards the surface of the top cover, the inner side of the lower part of the seat ring is abutted to the inner wall of the rotating wheel close to the second abutting groove, and smooth transition is performed between the inner wall of the rotating wheel close to the second abutting groove and the surface of the bottom ring towards the top cover.

In one embodiment, the francis turbine further includes a diaphragm;

the volute comprises an inlet end and an outlet end, the volute gradually tapers from the inlet end to the outlet end, one end of the partition plate is connected with the junction of the inlet end and the outlet end, and the other end of the partition plate faces the rotating wheel and cuts off the junction of the inlet end and the outlet end.

In an embodiment, the francis turbine further comprises a guide vane, one end of the guide vane is connected with the partition plate, the other end of the guide vane faces the rotating wheel, and arc-shaped protrusions are respectively arranged on the upper side and the lower side of the guide vane, so that water flow from the inlet end is split by the arc-shaped protrusions to drive the rotating wheel along the extending direction of the volute.

In the mixed flow water turbine, the volute surrounds the rotating wheel, the side wall of the volute is provided with the open slot, so that water flowing in the volute can pass through the open slot and wash the original blades and the adjusting blades between the upper crown and the lower ring, and the rotating wheel can be driven to rotate around the rotating shaft due to the fact that the upper crown and the lower ring are fixed relative to the original blades and the adjusting blades, and finally the purpose of generating electricity is achieved.

The method comprises the steps that an original blade is cut from an outlet edge to an inlet edge along a middle streamline at a certain distance and parallel to the outlet edge, so that an adjusting blade is manufactured, the length of the middle streamline of the original blade is larger than that of the middle streamline of the adjusting blade, and the distance from the outlet edge of the original blade to a rotating shaft is smaller than that from the outlet edge of the adjusting blade to the rotating shaft; the distance from the inlet edge of the original blade to the rotating shaft is equal to the distance from the inlet edge of the adjusting blade to the rotating shaft, so that the distance from the inlet edge of the original blade to the inlet edge of the adjusting blade is equal to the distance from the water flow to the inlet edge of the adjusting blade, the balance of water flow to flushing of the original blade and the adjusting blade is ensured, the inlet edge of the adjusting blade is prevented from shrinking radially inwards, the abrasion of sediment caused by water flow to the original blade is increased by more flushing of the sediment caused by the original blade, the quantity of the original blades and the adjusting blade is equal through calculation, the original blades and the adjusting blade are sequentially and alternately arranged along the circumferential direction of the rotating wheel, the efficiency of the water turbine is improved, the relative speed of the blades is uniform, the internal streamline is smooth, the sediment resistance and the abrasion resistance are good, the comprehensive performance of the water turbine is improved, and the abrasion condition of the sediment to the rotating wheel is improved.

Drawings

Fig. 1 is a schematic structural view of a francis turbine according to an embodiment.

Fig. 2 is a cross-sectional view of the francis turbine of fig. 1.

Fig. 3 is a schematic structural view of the wheel of fig. 1.

Fig. 4 is a schematic view of the original blade and the alignment of the adjustment blades in fig. 3.

FIG. 5 is a schematic view of the original blade and the tuning blade of FIG. 4 at the intermediate streamline.

Fig. 6 is a schematic view of a structure of a lifting ring or a lifting hole according to an embodiment.

FIG. 7 is a schematic structural view of a vane of an embodiment.

Fig. 8 is an enlarged view at a in fig. 2.

FIG. 9 is a schematic structural view of a vane and separator plate of an embodiment.

Reference numerals illustrate:

100-mixed-flow water turbine;

110-a rotating wheel; 111-crown; 112-lower ring; 113-original leaves; 114-adjusting the blade; 115—an inlet side; 116-outlet side; 117-intermediate flow line;

120-rotating shaft;

130-annular protrusion; 131-hanging rings; 132-hanging hole;

140-top cap; 141-a first abutment groove; 142-smooth transition;

150-a bottom ring; 151-a second abutment groove;

160-seat ring;

170-volute; 171-open slot; 172-an inlet end; 173-an outlet end;

180-separator;

190-guide vanes; 191-arc-shaped protrusions; 192-inscribed circle.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that, if any, these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., are used herein with respect to the orientation or positional relationship shown in the drawings, these terms refer to the orientation or positional relationship for convenience of description and simplicity of description only, and do not indicate or imply that the apparatus or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the application.

Furthermore, the terms "first," "second," and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the terms "plurality" and "a plurality" if any, mean at least two, such as two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly. For example, the two parts can be fixedly connected, detachably connected or integrated; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present application, unless expressly stated or limited otherwise, the meaning of a first feature being "on" or "off" a second feature, and the like, is that the first and second features are either in direct contact or in indirect contact through an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that if an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. If an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein, if any, are for descriptive purposes only and do not represent a unique embodiment.

Referring to fig. 1-5, fig. 1 shows a schematic structural diagram of a francis turbine 100 according to an embodiment of the present application, and the francis turbine 100 according to an embodiment of the present application includes: a volute 170 and a rotor 110.

The wheel 110 includes: an upper crown 111, a lower ring 112, a plurality of original blades 113, a plurality of tuning blades 114.

The number of the original blades 113 is equal to that of the adjustment blades 114, and the original blades and the adjustment blades are alternately arranged in sequence along the circumferential direction of the rotating wheel 110. The original blade 113 and the adjusting blade 114 have an inlet edge 115 and an outlet edge 116, and the rotating shaft 120 is disposed through the upper crown 111 and the lower ring 112, and the outlet edge 116 is close to the rotating shaft 120 relative to the inlet edge 115. The original blade 113 and the adjustment blade 114 are located between the upper crown 111 and the lower ring 112, and the upper crown 111 and the lower ring 112 are fixed relative to the original blade 113 and the adjustment blade 114.

The line defining the midpoint of the inlet edge 115 to the midpoint of the outlet edge 116 is a medial streamline 117. The length of the intermediate flow line 117 of the original blade 113 is greater than the length of the intermediate flow line 117 of the regulator blade 114, and the distance from the outlet edge 116 of the original blade 113 to the axis of rotation 120 is less than the distance from the outlet edge 116 of the regulator blade 114 to the axis of rotation 120. The distance from the inlet edge 115 of the original blade 113 to the rotation axis 120 is equal to the distance from the inlet edge 115 of the adjusting blade 114 to the rotation axis 120.

In the francis turbine 100, the volute 170 surrounds the runner 110, and the sidewall of the volute 170 is provided with the open groove 171, so that water flowing in the volute 170 can pass through the open groove 171 and wash the original blades 113 and the adjusting blades 114 between the upper crown 111 and the lower ring 112, and the upper crown 111 and the lower ring 112 are fixed relative to the original blades 113 and the adjusting blades 114, so that the runner 110 can be driven to rotate around the runner 120, and finally, the purpose of generating electricity is achieved.

The original blade 113 is cut along the intermediate flow line 117 from the outlet edge 116 to the inlet edge 115 at a distance parallel to the outlet edge 116, whereby the tuning blade 114 is made such that the length of the intermediate flow line 117 of the original blade 113 is greater than the length of the intermediate flow line 117 of the tuning blade 114 and such that the distance from the outlet edge 116 of the original blade 113 to the axis of rotation 120 is less than the distance from the outlet edge 116 of the tuning blade 114 to the axis of rotation 120. The distance from the inlet edge 115 of the original blade 113 to the rotating shaft 120 is equal to the distance from the inlet edge 115 of the adjusting blade 114 to the rotating shaft 120, so that the distance from the water flowing to the inlet edge of the original blade 113 to the water flowing to the inlet edge of the adjusting blade 114 is equal, the balance of the water flowing to the flushing of the original blade 113 and the adjusting blade 114 is ensured, the inlet edge of the adjusting blade 114 is prevented from shrinking radially inwards, the sand caused by the water flowing to the original blade 113 is increased, the quantity of the original blades 113 and the adjusting blade 114 is equal through calculation, the raw blades 113 and the adjusting blade 114 are alternately arranged along the circumferential direction of the rotating wheel 110, the efficiency of the water turbine is improved, the relative speed of the blades is uniform, the internal streamline is smooth, the sand resistance and the abrasion resistance are good, the comprehensive performance of the water turbine is improved, and the abrasion condition of the sand to the rotating wheel 110 is improved.

Specifically, the upper crown 111 face is connected to the face of the upper crown 111 adjacent to the lower ring 112, and the lower ring 112 face is connected to the face of the lower ring 112 adjacent to the upper crown 111

Specifically, the scroll casing 170 includes an inlet end 172 and an outlet end 173, the pipe diameter of the scroll casing 170 is gradually reduced from the inlet end 172 to the outlet end 173, the scroll casing 170 surrounds the rotating shaft 110, an open groove 171 is formed in the side wall of the scroll casing 170, water flows to the outlet end 173 through the inlet end 172, and the original blades 113 and the adjusting blades 114 are flushed through the open groove 171 to enable the rotating shaft 110 to rotate around the rotating shaft 120.

Specifically, the number of the original blades 113 and the number of the adjustment blades 114 are 6, and they exhibit superior anti-cavitation performance compared to the full original blades 113. The 6 original blades 113 and the 6 adjusting blades 114 are alternately arranged, so that the structure is simple and compact, the weight is light, and the manufacturing cost is reduced.

In one embodiment, the ratio of the length of the intermediate streamline 117 of the original blade 113 and the intermediate streamline 117 of the tuning blade 114 is HK: HG is 3: 2. 4: 3. 5:4.

The CFD analysis results of the ratio of HG to HK of the original blade to the tuning blade are shown in table 1.

TABLE 1 comparison of CFD analysis results of the influence of the ratio of HG to HK of the original blade to the adjusted blade on normalized Rate and normalized Power

Ratio of HK to HG	Maximum relative speed m/s of runner	Normalized power	Normalization efficiency
				3：2	30.1	0.99	0.97
4：3	30.9	1.00	0.99
				5：4	30.9	1.00	1.00

Preferably, the ratio of the intermediate streamline 117 of the original blade 113 to the intermediate streamline 117 of the regulator blade 114 is 5: the abrasion of the francis turbine 100 is closely related to the relative flow velocity in the runner, and the abrasion amount is proportional to the relative flow velocity to more than the 3 rd power. The abrasion resistance of the francis turbine 100 is judged by the magnitude of the flow velocity at key locations in the runner. For hydropower stations running in medium and low water heads and with high sand content, the abrasion inside the rotating wheel 110 is most serious, particularly the abrasion of the outlet edge 116 area of the lower part of the blade of the rotating wheel 110 is most serious, and the relative flow rate of the unit near the lower ring 112 of the rotating wheel 110 is reduced by optimizing the flow fields in the blade and the rotating wheel 110, so that the abrasion degree of the abrasion-prone part is effectively reduced, and the abrasion of the rotating wheel 110 is effectively reduced. The smaller the runner 110 maximum relative velocity, the better the wear resistance. Where normalized power is the power for each condition, normalized efficiency is the efficiency divided by their respective maximum, when the ratio of the intermediate streamline 117 of the original blade 113 to the intermediate streamline 117 of the tuning blade 114 is 5:4, the normalized power and normalized efficiency are greater, so the wear reduction effect of the wheel 110 is best.

Referring to fig. 6, in an embodiment, an annular protrusion 130 is provided on an upper surface of the upper crown 111, and a plurality of hanging rings 131 are provided on a surface of the annular protrusion 130 away from the lower ring 112, so that the rotating wheel 110 can be conveniently lifted up through the hanging rings 131.

In an embodiment, the plurality of hanging rings 131 are divided into two groups, and the two groups of hanging rings 131 are symmetrically arranged along the radial direction of the annular protrusion 130, so that when the rotating wheel 110 is lifted, the lifting force can be more uniform, and the rotating wheel 110 is prevented from being skewed.

Specifically, the number of the hanging rings 131 is four, and the hanging rings are symmetrically arranged along the radial direction of the rotating wheel 110.

In one embodiment, the nominal tensile strength of the plurality of suspension rings 131 is up to 1200 MPa. The nominal yield strength is 1080MPa, so that when the hanging ring 131 is selected, the hanging ring 131 can be selected according to the performance grade, the hanging ring 131 with the same performance grade has the same performance no matter the material and the production place are different, and the high applicability of the material is realized by giving the performance grade standard.

In an embodiment, a plurality of pairs of hanging holes 132 corresponding to the hanging rings 131 one by one are formed on a surface of the annular protrusion 130 away from the lower ring 112, and two hanging holes 132 of each pair of hanging holes 132 are in an arc shape and are respectively in threaded fit with two ends of the hanging ring 131, so that the hanging ring 131 is fixed on the annular protrusion 130.

Specifically, the hanging hole 132 is a threaded hole, and two ends of the hanging ring 131 are respectively provided with external threads.

In another embodiment, the sling is U-shaped.

Referring to fig. 2 and 8, in one embodiment, the francis turbine 100 includes: the top cover 140, the bottom ring 150, the seat ring 160 and the volute 170, the top cover 140 is located on the upper side of the runner 110, and the bottom ring 150 is located on the lower side of the runner 110.

The scroll casing 170 surrounds the rotating shaft 110, and an opening groove 171 is formed in a side wall of the scroll casing 170, so that water flowing in the scroll casing 170 can drive the rotating shaft 120 to rotate around the rotating shaft 110 through the opening groove 171.

The seat ring 160 is located between the rotor 110 and the volute 170, with the outside of the seat ring 160 communicating with the open groove 171.

The upper part of the inner side of the seat ring 160 is connected to the top cover 140, a first contact groove 141 is formed in the surface of the outer side of the top cover 140 facing the bottom ring 150, the inner side of the upper part of the seat ring 160 is in contact with the inner wall of the first contact groove 141, which is close to the rotating wheel 110, and smooth transition is performed between the inner wall of the first contact groove 141, which is close to the rotating wheel 110, and the surface of the top cover 140 facing the bottom ring 150.

The lower part of the inner side of the seat ring 160 is connected with the bottom ring 150, the surface of the outer side of the bottom ring 150 facing the top cover 140 is provided with a second abutting groove 151, the inner side of the lower part of the seat ring 160 is abutted against the inner wall of the second abutting groove 151 close to the rotating wheel 110, the inner wall of the second abutting groove 151 close to the rotating wheel 110 and the surface of the bottom ring 150 facing the top cover 140 are smoothly transited, so that the water flow in the volute 170 flushes the original blades 113 and the adjusting blades 114 through the space between the seat ring 160 and the bottom ring 150 and the top cover 140, the surface of the outer side of the top cover 140 facing the bottom ring 150 is provided with a first abutting groove 141, the inner side of the upper part of the seat ring 160 is abutted against the inner wall of the first abutting groove 141, the surface of the outer side of the bottom ring 150 facing the top cover 140 is provided with a second abutting groove 151, and the inner side of the lower part of the seat ring 160 is abutted against the inner wall of the second abutting groove 151 close to the rotating wheel 110, and the water flow cannot leak from a gap in the form of direct connection. Meanwhile, the first abutting groove 141 is close to the inner wall of the runner 110 and the surface of the top cover 140 facing the bottom ring 150 for smooth transition, and the second abutting groove 151 is close to the inner wall of the runner 110 and the surface of the bottom ring 150 facing the top cover 140 for smooth transition, so that the water flow is smoother, and the output and the efficiency of the water turbine can be improved.

Referring to fig. 9, in one embodiment, the francis turbine 100 further includes a diaphragm 180. The volute 170 comprises an inlet end 172 and an outlet end 173, the volute 170 is gradually reduced from the inlet end 172 to the outlet end 173, one end of the partition 180 is connected with the junction between the inlet end 172 and the outlet end 173, and the other end faces the rotating wheel 110 and cuts off the junction between the inlet end 172 and the outlet end 173, so as to prevent water flow of the inlet end 172 from directly entering the outlet end 173 without flowing through the rotating wheel 110, so that the original blades 113 and the adjusting blades 114 are not washed by the water flow, and therefore work is not applied to the rotating wheel 110, and the power generation efficiency is affected.

Referring to fig. 7 and 9, in an embodiment, the francis turbine 100 further includes a guide vane 190, one end of the guide vane 190 is connected to the partition plate 180, the other end faces the runner 110, and arc protrusions 191 are respectively disposed on the upper and lower sides of the guide vane 190, so that the water flow from the inlet end 172 is split by the arc protrusions 191 to drive the runner 110 along the extending direction of the volute 170, so that the water flow is smoother, and the guide vane 190 has high hydraulic efficiency and abrasion resistance when running in the sandy water flow.

Specifically, the cross section of the vane 190 has an inscribed circle to facilitate designing the vane 190, the vane 190 being tangential to this circle when the vane 190 is designed.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. The mixed flow hydraulic turbine is characterized by comprising a runner and a rotating shaft;

2. The francis turbine of claim 1, wherein a ratio of a length of the intermediate streamline of the original blade to the intermediate streamline of the tuning blade is 3: 2. 4: 3. 5:4.

3. The francis turbine of claim 2, wherein the ratio of the intermediate streamline of the original blade to the intermediate streamline of the tuning blade is 5:4.

4. the francis turbine of claim 1, wherein an upper surface of the crown is provided with an annular protrusion, and a surface of the annular protrusion remote from the lower ring is provided with a plurality of hanging rings.

5. The francis turbine of claim 4, wherein the plurality of lifting rings are divided into two groups, the two groups of lifting rings being symmetrically disposed along a radial direction of the annular protrusion.

6. The francis turbine of claim 5, wherein a nominal tensile strength of the plurality of lifting rings is up to 1200 MPa; the nominal yield strength is 1080 MPa.

7. The francis turbine of claim 5, wherein the surface of the annular protrusion away from the lower ring is provided with a plurality of pairs of hanging holes corresponding to the hanging rings one by one, the hanging rings are arc-shaped, and two hanging holes of each pair of hanging holes are respectively in threaded fit with two ends of the hanging ring so that the hanging ring is fixed on the annular protrusion.

8. The francis turbine of claim 1, wherein the francis turbine includes: the top cover is positioned on the upper side of the rotating wheel, and the bottom ring is positioned on the lower side of the rotating wheel;

9. The francis turbine of claim 8, further comprising a diaphragm;

10. The francis turbine of claim 9, further comprising a guide vane having one end connected to the partition plate and the other end directed toward the runner, the guide vane being provided with arc-shaped protrusions at upper and lower sides thereof, respectively, so that water flow from the inlet end is split by the arc-shaped protrusions to drive the runner in an extending direction of the volute.