NL2032831B1

NL2032831B1 - Francis turbine

Info

Publication number: NL2032831B1
Application number: NL2032831A
Authority: NL
Inventors: Yan Chenkai; Xie Yunding; Wu Hao; Xue Feng
Original assignee: Ningde Shangbaishi Water Conservancy Project Co Ltd
Priority date: 2022-05-24
Filing date: 2022-08-23
Publication date: 2023-12-07
Also published as: CN114992031A; ZA202209720B

Abstract

A Francis turbine includes a casing (300), a main shaft (100) inserted into the casing (300), a first runner (210) and a second runner (220) respectively disposed inside the casing (300) coaxially with the main shaft (100), and fixedly disposed on the main shaft (100) at an interval. The casing (300) includes a first volute (310) disposed on the first runner (210) in a sleeving manner and a second volute (320) disposed on the second runner (220) in a sleeving manner in sequence in the axial direction of the main shaft (100). A first inIet (3101) from a water inIet end to a nose end of the first volute (310) is formed in a side wall, facing the first runner (210). A second inIet (3201) from a water inIet end to a nose end of the second volute (320) is formed in a side wall, facing the second runner (220).

Description

FRANCIS TURBINE

TECHNICAL FIELD

[0001] The disclosure relates to the technical field of turbines, in particular to a

Francis turbine.

Background

[0002] A Francis turbine is the most widely used type of turbine at present. Its main components include a volute, a seat ring, water guide mechanisms, a top cover, runners, a main shaft, a guide bearing, a bottom ring, a draft tube, etc. The main function of the volute as a water guide part of the turbine is to lead water flows to the water guide mechanisms in front of the runners with minimum hydraulic loss, make the water flows enter into the water guide mechanisms evenly and axisymmetrically, and at the same time, make the water flows have a certain velocity circulation in order to improve the running stability of effective water energy acting on the runners. A method of independently changing opening degrees of guide vanes is to adjust the opening degrees of the guide vanes of the turbine by using a speed control system according to deviation of a unit speed or frequency caused by load changes, so that a power moment of the turbine and a resistance moment of a generator can be recovered to balance in time, and the speed and frequency can be maintained within a specified range.

Summary

[0003] The disclosure aims to provide a Francis turbine. The Francis turbine includes a first runner and a second runner disposed in an axial direction of a main shaft, a first volute corresponding to the first runner, and a second volute corresponding to the second runner. The first runner and the second runner are controlled to rotate by controlling the water inflows of the first volute and the second volute, so as to adjust a changing load and frequency, and small load and frequency fluctuations are adjusted to meet the requirements for connection and disconnection between a unit and a power grid.

[0004] In order to achieve the above objective, the disclosure provides a Francis turbine. The Francis turbine includes a casing, a main shaft, a first runner and a second runner. The main shaft is inserted into the casing, and the first runner and the second runner are disposed inside the casing coaxially with the main shaft, and are fixedly disposed on the main shaft at an interval in an axial direction of the main shaft;

[0005] The casing includes a first volute disposed on the first runner in a sleeving manner and a second volute disposed on the second runner in a sleeving manner in sequence in the axial direction of the main shaft; a first inlet from a water inlet end to a nose end of the first volute is formed in a side wall, facing the first runner, of the first volute, so that water entering the first volute from the water inlet end is discharged from the first inlet, and pushes the first runner and the main shaft to rotate;

[0006] A second inlet from a water inlet end to a nose end of the second volute is formed in a side wall, facing the second runner, of the second volute, so that water entering the second volute from the water inlet end is discharged from the second inlet, and pushes the second runner and the main shaft to rotate.

[0007] Optionally, the casing further comprises a seat ring, and the seat ring comprises a first seat ring part and a second seat ring part;

[0008] the first seat ring part is disposed at the first inlet of the first volute, a plurality of first seat ring inlets are formed in an outer side of the first seat ring part at intervals in a circumferential direction, and a plurality of first adjusting guide vanes which are disposed at intervals in the circumferential direction and are adjustable in opening degree are disposed on an inner side of the first seat ring part; and

[0009] the second seat ring part is disposed at the second inlet of the second volute, a plurality of second seat ring inlets are formed in an outer side of the second seat ring part at intervals in the circumferential direction, and a plurality of second adjusting guide vanes which are disposed at intervals in the circumferential direction and are adjustable in opening degree are disposed on an inner side of the second seat ring part.

[0010] Optionally, the first seat ring part and the second seat ring part are formed integrally.

[0011]Optionally, the Francis turbine further comprising a first opening degree adjusting mechanism, the first opening degree adjusting mechanism comprises a first drive unit, a first control ring, and first connecting assemblies, the plurality of first adjusting guide vanes are connected to the first control ring via the first connecting assemblies, and the first drive unit is connected to the first control ring and is used to adjust the opening degree of the plurality of first adjusting guide vanes by driving the first control ring to rotate in the circumferential direction of the main shaft.

[0012] Optionally, the Francis turbine further comprising a second opening degree adjusting mechanism, the second opening degree adjusting mechanism comprises a second drive unit, a second control ring, and second connecting assemblies, the plurality of second adjusting guide vanes are connected to the second control ring via the second connecting assemblies, and the second drive unit is connected to the second control ring and is used to adjust the opening degree of the plurality of second adjusting guide vanes by driving the second control ring to rotate in the circumferential direction of the main shaft.

[0013] Optionally, the first connecting assemblies comprise first crank arms and first connecting rods; and

[0014] one ends of the first crank arms are connected to the first adjusting guide vanes, one ends of the first connecting rods are rotatably connected to ends, away from the first adjusting guide vanes, of the first crank arms, and the other ends of the first connecting rods are rotatably connected to the first control ring; and/or

[0015] the second connecting assemblies comprise second crank arms and second connecting rods; and

[0016] one ends of the second crank arms are connected to the second adjusting guide vanes, one ends of the second connecting rods are rotatably connected to ends, away from the second adjusting guide vanes, of the second crank arms, and the other ends of the second connecting rods are rotatably connected to the second control ring.

[0017] Optionally, the casing further comprises a top cover assembly and a bottom cover assembly;

[0018] the top cover assembly is disposed on a side, away from the second volute, of the first volute, and the bottom cover assembly is disposed on a side, away from the first volute, of the second volute;

[0019]the main shaft extends into the casing via an opening in the top cover assembly to be connected to the first runner and the second runner; and

[0020] a draft tube is connected to an opening in the bottom cover assembly.

[0021] Optionally, an upper sealing ring is disposed between the first runner and the top cover assembly for sealing between the first runner and the top cover assembly;

[0022] a middle sealing ring is disposed between the first runner and the second runner for sealing between the first runner and the seat ring and sealing between the second runner and the seat ring; and

[0023] a lower sealing ring is disposed between the second runner and the bottom cover assembly for sealing between the second runner and the bottom cover assembly.

[0024] Optionally, the first volute and the second volute have different flow areas.

[0025] Optionally, a width of the first inlet gradually increases from the water inlet end to the nose end of the first volute; and/or,

[0026]a width of the second inlet gradually increases from the water inlet end to the nose end of the second volute.

[0027] Through the above technical solution, that is, in the Francis turbine provided by the disclosure, one end of the main shaft is inserted into the casing, the first runner and the second runner are fixedly disposed at an interval in the axial direction of the main shaft, and the casing includes the first volute disposed on the first runner in the sleeving manner in the circumferential direction, and the second volute disposed on the second runner in the sleeving manner, so that water entering from the water inlet end of the first volute can be discharged from the first inlet and pushes the first runner and the main shaft to rotate, and water entering from the water inlet end of the second volute can be discharged from the second inlet and pushes the second runner and the main shaft to rotate. When the turbine unit is started, water can be introduced into the first volute and pushes the first runner and the main shaft to rotate, so that a controlled unit can be within a potential head range under no-load operating conditions, and the fluctuation value of the unit can be less than the standard requirement by adjusting the rotation speed of the unit, which is conductive to quickly connecting the unit with the power grid. When the controlled unit is connected with the power grid for operation, due to the complicated changes in load capacity and properties of the power grid, by introducing water into the first volute and the second volute at the same time and pushing the first runner, the second runner and the main shaft to rotate, the effective power of the controlled unit can be equal to a given value, and the stability of lifting loads is improved. When the controlled unit is disconnected from the power grid or operates in an independent small power grid, the transitional smoothness of a rotation speed of the main shaft is improved by adjusting water inflows in the first volute and the second volute, and the unit can have good dynamic performance in a recovery process by adjusting the frequency and load of the controlled unit according to frequency deviation.

[0028] Other features and benefits of the disclosure will be described in detail in the subsequent detailed description. 5

Brief Description of the Drawings

[0029] The accompanying drawings are intended to provide a further understanding of the disclosure, form a part of the description, and are used to explain the disclosure together with the following detailed description, but do not constitute a limitation of the disclosure. In the accompanying drawings:

[0030] Fig. 1 is a partial cross-sectional view of a Francis turbine provided by some examples of the disclosure.

[0031] Fig. 2 is a radial cross-sectional view of a Francis turbine provided by some examples of the disclosure.

Detailed Description

[0032] The detailed implementation of the disclosure will be described in detail below in combination with the accompanying drawings. It can be understood that the detailed implementation described herein is merely used to illustrate and explain the disclosure and are not used to limit the disclosure.

[0033] In the disclosure, unless otherwise stated, directional words such as “up” and “down” generally refer to the relative “up” and “down” in the direction of gravity when the corresponding component is in use. In addition, the terms “first”, “second”, etc. in the disclosure are used to distinguish one element from another and are not of order or importance. Furthermore, in the following description, when referring to the drawings, unless otherwise explained, the same reference numerals in different accompanying drawings refer to the same or similar elements. The above definitions are merely used to explain and illustrate the disclosure, and are not intended to be construed as limiting the disclosure.

[0034] An existing volute is designed with a one-way water inlet, and the section of a volute structure segment is gradually reduced to form a necessary circulation in front of the water guide mechanism. When a water flow passes through an inlet section of the volute to a nose section, a change of a tangential velocity of the water flow is greatly influenced by a section size. In addition, by setting all sections of a volute structure segment to be elliptical, that is, a tail segment of the volute structure segment is also elliptical, axisymmetric potential flow cannot be formed ideally. Complex changes in load capacity and nature of a power grid are not conducive to connection and disconnection of a unit and the power grid.

[0035] As shown in Fig. 1 and Fig. 2, in order to achieve the above objective, the disclosure provides a Francis turbine. The Francis turbine includes a casing 300, a main shaft 100, a first runner 210, and a second runner 220. The main shaft 100 is inserted into the casing 300. The first runner 210 and the second runner 220 are disposed inside the casing 300 coaxially with the main shaft 100, and are fixedly disposed on the main shaft 100 at an interval in an axial direction of the main shaft 100. The casing 300 includes a first volute 310 disposed on the first runner 210 in a sleeving manner and a second volute 320 disposed on the second runner 220 in a sleeving manner in sequence in the axial direction of the main shaft 100. A first inlet from a water inlet end to a nose end of the first volute 310 is formed in a side wall, facing the first runner 210, of the first volute 310, so that water entering the first volute 310 from the water inlet end is discharged from the first inlet, and pushes the first runner 210 and the main shaft 100 to rotate. A second inlet from a water inlet end to a nose end of the second volute 320 is formed in a side wall, facing the second runner 220, of the second volute 320, so that water entering the second volute 320 from the water inlet end is discharged from the second inlet, and pushes the second runner 220 and the main shaft 100 to rotate.

[0036] The Francis turbine is provided with the first runner 210 and the second runner 220 which are disposed on the main shaft 100 at an interval in the axial direction of the main shaft 100, the first volute 310 corresponding to the first runner 210, and the second volute 320 corresponding to the second runner 220. The first runner 210 and the second runner 220 are controlled to rotate by controlling a water inflow of the first volute 310 and the second volute 320, so as to push the main shaft 100 to rotate. By adjusting the water inflows of the first volute 310 and the second volute 320, the load and frequency are adjusted, and small load and frequency fluctuations are adjusted to meet the needs for connection and disconnection between a unit and a power grid.

[0037] Through the above technical solution, that is, in the Francis turbine provided by the disclosure, one end of the main shaft 100 is inserted into the casing 300, the first runner 210 and the second runner 220 are fixedly disposed at an interval in the axial direction of the main shaft, and the casing 300 includes the first volute 310 disposed on the first runner 210 in the sleeving manner in the circumferential direction, and the second volute 320 disposed on the second runner 220 in the sleeving manner, so that water entering from the water inlet end of the first volute 310 can be discharged from the first inlet and pushes the first runner 210 and the main shaft 100 to rotate, and water entering from the water inlet end of the second volute 320 can be discharged from the second inlet and pushes the second runner 220 and the main shaft 100 to rotate. When the turbine unit is started, water can be introduced into the first volute 310 and pushes the first runner 210 and the main shaft 100 to rotate, so that a controlled unit can be within a potential head range under no-load operating conditions, and the fluctuation value of the unit can be less than the standard requirement by adjusting the rotation speed of the unit, which is conductive to quickly connecting the unit with the power grid. When the controlled unit is connected with the power grid for operation, due to the complicated changes in load capacity and properties of the power grid, by introducing water into the first volute 310 and the second volute 320 at the same time and pushing the first runner 210, the second runner 220 and the main shaft 100 to rotate, active power of the controlled unit can be equal to a given value, and the stability of lifting loads is improved. When the controlled unit is disconnected from the power grid or operates in an independent small power grid, the transitional smoothness of a rotation speed of the main shaft 100 is improved by adjusting the water inflows in the first volute 310 and the second volute 320, and the unit can have good dynamic performance in a recovery process by adjusting the frequency and load of the controlled unit according to the frequency deviation.

[0038] It needs to be noted that the first runner 210 and the second runner 220 may be constructed in any suitable manner, and may also be designed with structures disclosed in the related art, which are not limited in the disclosure.

[0039] The casing 300 may be constructed in any suitable manner. As shown in

Fig. 1 and Fig. 2, in some examples of the disclosure, the casing 300 may further include a seat ring 330, and the seat ring 330 includes a first seat ring part 331 and a second seat ring part 332. The first seat ring part 331 and the second seat ring part 332 are connected in the axial direction of the main shaft 100. The first seat ring part 331 is disposed at the first inlet 3101 of the first volute 310. A plurality of first seat ring inlets 3311 are formed in an outer side of the first seat ring part 331 at intervals in a circumferential direction. A plurality of first adjusting guide vanes 410 which are disposed at intervals in the circumferential direction and are adjustable in opening degree are disposed on an inner side of the first seat ring part 331. The outer side of the first seat ring part 331 is configured to be provided with a plurality of fixed guide vanes disposed at intervals, and each first seat ring inlet 3311 is formed between corresponding two adjacent fixed guide vanes, so that water in the first volute 310 can enter and be guided to the first runner 210 from the first seat ring inlets 3311 to push both the first runner 210 and the main shaft 100 connected to the first runner 210 to rotate.

[0040] The second seat ring part 332 is disposed at the second inlet 3201 of the second volute 320. A plurality of second seat ring inlets 3321 are formed in an outer side of the second seat ring part 332 at intervals in the circumferential direction. A plurality of second adjusting guide vanes 420 which are disposed at intervals in the circumferential direction and are adjustable in opening degree are disposed on an inner side of the second seat ring part 332. The outer side of the second seat ring part 332 may also be configured to be provided with a plurality of fixed guide vanes disposed at intervals, and each second seat ring inlet 3321 is formed between corresponding two adjacent fixed guide vanes, so that water in the second volute 320 can enter and be guided to the second runner 220 from the second seat ring inlets 3321 to push both the second runner 220 and the main shaft 100 connected to the second runner 220 to rotate.

[0041] The first seat ring part 331 and the second seat ring part 332 may be manufactured separately and be connected via connecting assemblies. In some examples, the first seat ring part 331 and the second seat ring part 332 may be formed integrally, for example, may be cast integrally.

[0042] In order to adjust the opening degree of the first adjusting guide vanes 410 and the second adjusting guide vanes 420 to achieve different loads and frequencies, so as to meet the needs of different working conditions, the Francis turbine further includes a first opening degree adjusting mechanism. The first opening degree adjusting mechanism may be constructed in any suitable manner.

As shown in Fig. 2, in some examples of the disclosure, the first opening degree adjusting mechanism includes a first drive unit 413, a first control ring 412, and first connecting assemblies 411. The plurality of first adjusting guide vanes 410 are connected to the first control ring 412 via the first connecting assemblies 411. The first drive unit 413 is connected to the first control ring 412 and is used to adjust the opening degree of the plurality of first adjusting guide vanes 410 by driving the first control ring 412 to rotate in the circumferential direction of the main shaft 100. The first drive unit 413 may be configured as a telescopic cylinder or a telescopic rod,

and the first drive unit 413 may be fixed to a first base 414. The main shaft 100 is sleeved with the first control ring 412. The first drive unit 413 may drive the first control ring 412 to rotate around the main shaft 100, and the plurality of first adjusting guide vanes 410 are each connected to the first control ring 412 via the first connecting assemblies 411 respectively. The plurality of first adjusting guide vanes 410 may be driven to rotate by rotating the first control ring 412, so as to adjust the opening degree.

[0043] The Francis turbine further includes a second opening degree adjusting mechanism. The second opening degree adjusting mechanism may also be constructed in any suitable manner. As shown in Fig. 2, in some examples of the disclosure, the second opening degree adjusting mechanism includes a second drive unit (not shown in the figure), a second control ring 422, and second connecting assemblies 421. The plurality of second adjusting guide vanes 420 are connected to the second control ring 422 via the second connecting assemblies 421. The second drive unit is connected to the second control ring 422 and is used to adjust the opening degree of the plurality of second adjusting guide vanes 420 by driving the second control ring 422 to rotate in the circumferential direction of the main shaft 100. The second drive unit may be configured as a telescopic cylinder or a telescopic rod, and the second drive unit may be fixed to a second base (not shown in the figure). The main shaft 100 is sleeved with the second control ring 422. The second drive unit may drive the second control ring 422 to rotate around the main shaft 100, and the plurality of second adjusting guide vanes 420 are connected to the second control ring 422 via the second connecting assemblies 421 respectively. The plurality of second adjusting guide vanes 420 may be driven to rotate by rotating the second control ring 422, so as to adjust the opening degree.

[0044] In order to connect the first adjusting guide vanes 410 with the first control ring 412, so as to enable the first control ring 412 to drive the plurality of first adjusting guide vanes 410 to rotate for adjusting the opening degree, as shown in

Fig. 2, in some examples, each first connecting assembly 411 includes a first crank arm 4111 and a first connecting rod 4112. One ends of the first crank arms 4111 are connected to the first adjusting guide vanes 410. One ends of the first connecting rods 4112 are rotatably connected to ends, away from the first adjusting guide vanes 410, of the first crank arms 4111, and the other ends of the first connecting rods 4112 are rotatably connected to the first control ring 412. The plurality of first adjusting guide vanes 410 are rotatably disposed on the inner side of the first seat ring part 331. The lower ends of the first crank arms 4111 are connected to the first adjusting guide vanes 410. The upper ends of the first crank arms 4111 protrude out of the casing, and are hinged to one ends of the first connecting rods 4112. The other ends of the first connecting rods 4112 are hinged to the first control ring 412. The plurality of first adjusting guide vanes 410 may be driven to rotate by rotating the first control ring 412.

[0045] In order to connect the second adjusting guide vanes 420 with the second control ring 422, so as to enable the second control ring 422 to drive the plurality of second adjusting guide vanes 420 to rotate for adjusting the opening degree, as shown in Fig. 2, in some examples, each second connecting assembly 421 includes a second crank arm 4211 and a second connecting rod 4212. One ends of the second crank arms 4211 are connected to the second adjusting guide vanes 420. One ends of the second connecting rods 4212 are rotatably connected to ends, away from the second adjusting guide vanes 420, of the second crank arms 4211, and the other ends of the second connecting rods 4212 are rotatably connected to the second control ring 422. The plurality of second adjusting guide vanes 420 are rotatably disposed on the inner side of the second seat ring part 332. The lower ends of the second crank arms 4211 are connected to the second adjusting guide vanes 420. The lower ends of the second crank arms 4211 protrude out of the casing, and are hinged to one ends of the second connecting rods 4212. The other ends of the second connecting rods 4212 are hinged to the second control ring 422. The plurality of second adjusting guide vanes 420 may be driven to rotate by rotating the second control ring 422.

[0046] As shown in Fig. 1 and Fig. 2, in some examples, the casing 300 further includes a top cover assembly 340 and a bottom cover assembly 350. The top cover assembly 340 is disposed on a side, away from the second volute 320, of the first volute 310. The bottom cover assembly 350 is disposed on a side, away from the first volute 310, of the second volute 320. The main shaft 100 extends into the casing 300 via an opening in the top cover assembly 340 to be connected to the first runner 210 and the second runner 220. A draft tube 500 is connected to an opening in the bottom cover assembly 350. The draft tube 500 is open in a direction away from the second runner 220.

[0047] In order to realize the sealing between the first runner 210 and the top cover assembly 340, sealing between the second runner 220 and the bottom cover assembly 350, and sealing between the first runner 210 and the second runner 220 and the seat ring 330, as shown in Fig. 1 and Fig. 2, in some examples, an upper sealing ring 361 is disposed between the first runner 210 and the top cover assembly 340 for sealing between the first runner 210 and the top cover assembly 340; a middle sealing ring 362 is disposed between the first runner 210 and the second runner 220 for sealing between the first runner 210 and the seat ring 330 and sealing between the second runner 220 and the seat ring 330; and a lower sealing ring 363 is disposed between the second runner 220 and the bottom cover assembly 350 for sealing between the second runner 220 and the bottom cover assembly 350. The specific structures of the upper sealing ring 361, the middle sealing ring 362 and the lower sealing ring 363 can be designed and installed with reference to structures known in the related art as long as the above functions can be realized, which are not specifically limited in the disclosure.

[0048] In order to achieve different water inflows in the two volutes to further meet the requirements of different working conditions, in some examples, the first volute 310 and the second volute 320 have different flow areas. The flow area of the first volute 310 is smaller than the flow area of the second volute 320, and at the same time, the area of the first seat ring inlets 3311 of the seat ring 330 is smaller than the area of the second seat ring inlets 3321.

[0049] When the turbine is started, water is introduced into the first volute 310 merely, and the opening degree of the first adjusting guide vanes 410 is controlled by the first opening degree adjusting mechanism. As the first volute 310 and the first seat ring inlets 3311 have smaller area flows, the controlled unit can be within the potential head range under no-load operating conditions by controlling the first adjusting guide vanes 410, and the fluctuation value of the unit can be less than the standard requirement by adjusting the rotation speed of the unit, which is conductive to quickly connecting the unit with the power grid.

[0050] When the controlled unit is connected with the power grid for operation, due to the complicated changes in load capacity and properties of the power grid, water is introduced into the first volute 310 and the second volute 320, the effective power of the controlled unit can be equal to a given value separately by quickly adjusting the second adjusting guide vanes 420, and the stability of lifting loads is improved.

[0051] When the controlled unit is disconnected from the power grid or operates in an independent small power grid, the control smoothness is better by adjusting the first adjusting guide vanes 410 and the second adjusting guide vanes 420 at the same time, and the unit can have good dynamic performance in the recovery process by adjusting the frequency and load of the controlled unit according to the frequency deviation.

[0052] The first volute 310 and the second volute 320 may be constructed in any suitable manner. In some examples, the width of the first inlet gradually increases from the water inlet end to the nose end of the first volute 310; and/or, the width of the second inlet gradually increases from the water inlet end to the nose end of the second volute 320. The widths of the first inlet and the second inlet can be set in the form of gradually increasing from the water inlet end to the nose end, so that water can be distributed on the first adjusting guide vanes 410 and the second adjusting guide vanes 420 more evenly in the flow direction while flowing in a pipeline, and the running stability of the effective water energy acting on the runners can be further improved.

[0053] The preferred examples of the disclosure are described in detail above in combination with the accompanying drawings. However, the disclosure is not limited to the specific details of the above examples. Within the scope of the technical concept of the disclosure, a variety of simple modifications can be made to the technical solutions of the disclosure, and these simple modifications belong to the protection scope of the disclosure.

[0054]In addition, it needs to be noted that the specific technical features described in the above detailed description can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, various possible combination methods will not be described separately in the disclosure.

Claims

Conclusions

A Francis turbine, comprising: a housing (300), a main shaft (100) inserted into the housing (300), a first runner (210) and a second runner (220), respectively coaxial with the main shaft (100) ) are mounted in the housing (300), and are fixedly arranged on the main axis (100) at an interval in an axial direction from the main axis (100); wherein the casing (300) comprises a first volute (310) mounted on the first runner (210) in a wraparound manner and a second volute (320) mounted on the second runner {220) in a wraparound manner sequentially in the axial direction of the main axis (100); wherein a first inlet (3101) from a water inlet end to a nose end of the first volute (310) is formed in a side wall, facing the first runner (210), of the first volute (310), so that water entering the first volute (310) 310) entering from the water inlet end is discharged from the first inlet (3101), and pushes the first runner (210) and the main shaft (100) to rotate; and wherein a second inlet (3201) from a water inlet end to a nose end of the second volute (320) is formed in a side wall, facing the second runner (220), of the second volute (320), so that water entering from the second volute (320) of the water inlet end is discharged from the second inlet (3201), and pushes the second runner (220) and the main shaft (100) to rotate.

The Francis turbine of claim 1, wherein the housing (300) further comprises a seat ring (330), and the seat ring (330) comprises a first seat ring portion (331) and a second seat ring portion (332); wherein the first seat ring portion (331) is disposed at the first inlet (3101) of the first volute (310), a plurality of first seat ring inlets (3311) being formed in an exterior of the first seat ring portion (331) at intervals in a circumferential direction, and wherein a number of first regulating guide blades (410) arranged at intervals in the circumferential direction and adjustable in opening degree are arranged on an inner side of the first seat ring part (331); and wherein the second seat ring portion (332) is disposed at the second inlet (3201) of the second volute (320), a plurality of second seat ring inlets (3321) being formed in an exterior of the second seat ring portion (332) at intervals in the circumferential direction , and wherein a number of second regulating guide blades (420) arranged at intervals in the circumferential direction and adjustable in opening degree are arranged on an inner side of the second seat ring part (332).

The Francis turbine according to claim 2, wherein the first seat ring part (331) and the second seat ring part (332) are integrally formed.

The Francis turbine according to claim 2 or 3, wherein the Francis turbine further comprises a first opening degree adjustment mechanism, the first opening degree adjustment mechanism comprising a first drive unit (413), a first control ring (412) and first connection assemblies (411), wherein the plurality of first regulating guide blades (410) are connected to the first control ring (412) through the first connecting assemblies (411), and the first drive unit is connected to the first control ring (412) and is used to control the opening degree of the plurality of first regulating guide blades (410) by driving the first control ring (412) to rotate in the circumferential direction of the main shaft (100).

The Francis turbine according to claim 4, wherein the Francis turbine further comprises a second opening degree adjustment mechanism, the second opening degree adjustment mechanism comprising a second drive unit, a second control ring (422) and second connection assemblies (421), wherein the number of second regulating guide blades (420) is connected to the second control ring (422) through the second connecting assemblies (421), and the second drive unit is connected to the second control ring (422) and is used to adjust the opening degree of the plurality of second regulating guide blades (420) ) by driving the second control ring (422) to rotate in the circumferential direction of the main shaft (100).

The Francis turbine of claim 5, wherein the first connecting assemblies (411) include first crank arms (4111) and first connecting rods (4112); and one end of the first crank arms (4111) is connected to the first control guide blades (410), one end of the first connecting rods (4112) is rotatably connected to ends, away from the first control guide blades (410), of the first crank arms (4111), and the other ends of the first connecting rods (4112) are rotatably connected to the first control ring (412).

A Francis turbine according to claim 5 or 6, wherein the second connecting assemblies (421) include second crank arms (4211) and second connecting rods (4212); and one end of the second crank arms (4211) is connected to the second control guide blades (420), one end of the second connecting rods (4212) is rotatably connected to ends, away from the second control guide blades (420), of the second crank arms (4211), and the other ends of the second connecting rods (4212) are rotatably connected to the second control ring (422).

The Francis turbine according to any one of claims 2 to 7, wherein the housing (300) further comprises a top cover assembly (340) and a bottom cover assembly (350); wherein the top cover assembly (340) is disposed on a side away from the second volute (320), from the first volute (310), and the lower cover assembly (350) is disposed on a side away from the first volute (310), of the second cochlea (320); wherein the main shaft (100) extends into the housing (300) through an opening in the top cover assembly (340) to be connected to the first runner (210) and the second runner (220); and wherein a draft tube (500) is connected to an opening in the bottom cover assembly (350).

The Francis turbine of claim 8, wherein an upper seal ring (361) is provided between the first runner (210) and the top cover assembly (340) for sealing between the first runner (210) and the top cover assembly (340); wherein a middle sealing ring (361) is provided between the first runner (210) and the second runner (220) for sealing between the first runner (210) and the seat ring (330) and sealing between the second runner (220) and the seat ring (330); and wherein a lower sealing ring (363) is provided between the second runner (220) and the bottom cover assembly (350) for sealing between the second runner (220) and the bottom cover assembly (350).

A Francis turbine according to any one of claims 1 to 9, wherein the first volute (310) and the second volute (320) have different flow areas.

A Francis turbine according to any one of claims 1 to 10, wherein a width of the first inlet (3101) gradually increases from the water inlet end to the nose end of the first volute (310).

A Francis turbine according to any one of claims 1 to 11, wherein a width of the second inlet (3201) gradually increases from the water inlet end to the nose end of the second volute (320).