NO338393B1

NO338393B1 - Kaplan runner with stiffener

Info

Publication number: NO338393B1
Application number: NO20150431A
Authority: NO
Inventors: Patrik Nilsson; Emil Larsson
Original assignee: Rainpower Tech As
Priority date: 2015-04-10
Filing date: 2015-04-10
Publication date: 2016-08-15
Also published as: SE541372C2; SE1650479A1; NO20150431A1

Description

The invention relates to a Kaplan runner, comprising a hub with an inner and outer portion, trunnions inside the hub, blades attached to or integral with the trunnions, and a trunnion control mechanism for regulating the trunnions and thereby the blades as described in GB 1069627 and JP H0874721.

Kaplan runners form part of Kaplan turbines which mainly are used as drivers for electric generators in hydroelectric power plants.

US 6139272 describes a Kaplan runner, comprising: a hub with a longitudinal hub axis, the hub has an inner portion and a radially spaced outer portion, the inner and outer portions are structurally interconnected in an upper area of the hub; trunnions inside the hub, spaced in the circumferential direction of the hub, each trunnion has a longitudinal trunnion axis extending radially to the hub axis; trunnion bearings, comprising trunnion radial bearings for allowing the trunnions to rotate around the trunnion axes, and trunnion axial bearings for preventing the trunnions from moving away from the hub axis; blades outside the hub, each blade is attached to a trunnion, for rotating the trunnions and thereby the hub around the hub axis; a trunnion control mechanism for regulating the rotational position of the trunnions around the trunnion axes, for regulating the blades.

Kaplan runners have historically had a large hub diameter compared to the runner diameter. This is due to the fact that the trunnion control mechanism is space consuming if it is to have a long life.

To achieve high efficiency at high flows at a given runner diameter, Kaplan runner hub diameters have in general been continually reduced throughout the history of their development. The reduction in Kaplan runner hub diameters has resulted in weaker hubs. Also, major changes in the trunnion bearings have been made. These two factors combined result in large deformations of both hub and trunnions, resulting in higher contact pressures in the bearings and large deformations of sealings and runner blades. This can cause failed bearings, leaking seals and runner blades hitting the runner chamber.

The purpose of the invention is to overcome or reduce the above discussed problem. The purpose is achieved by the features of the description, drawings and claims.

The invention thus relates to a Kaplan runner, comprising:

a hub with a longitudinal hub axis, for coupling to a runner shaft, the hub has an inner portion and a radially spaced outer portion, the inner and outer portions are structurally interconnected in an upper area of the hub;

trunnions inside the hub, spaced in the circumferential direction of the hub, each trunnion has a longitudinal trunnion axis extending radially to the hub axis;

trunnion bearings, comprising trunnion radial bearings for allowing the trunnions to rotate around the trunnion axes, and trunnion axial bearings for preventing the trunnions from moving away from the hub axis;

blades outside the hub, each blade is attached to or integral with a trunnion, for rotating the trunnions and thereby the hub around the hub axis by the action of flowing water;

a trunnion control mechanism for regulating the rotational position of the trunnions around the trunnion axes, for regulating the blades.

According to the invention a stiffener connects the inner and outer portion of the hub. The stiffener preferably spans the space between the inner and outer portion of the hub, and it is also preferred that the stiffener is located below the trunnion axis. It is further preffered that the stiffener is connected to the inner portion of the hub close to the trunnion inner radial bearings, and to the outer portion of the hub close to the trunnion axial bearings.

In a particularly preferred embodiment the trunnion bearings also comprise, for each trunnion, a trunnion inner axial bearing located at the inner portion of the hub, for preventing the trunnion from moving towards the hub axis. The trunnion inner axial bearing is preferably located between the inner portion of the hub and the trunnion.

A further explanation of the invention and its advantages will be provided in the detailed part of the description.

The invention will now be described with reference to the accompanying drawings, wherein: Fig. 1 is a cutaway side view of a hydroelectric power plant using a Kaplan turbine with a Kaplan runner; Fig. 2 is a cutaway side view through a Kaplan runner hub according to prior art; Fig. 3 is cutaway side view through the Kaplan runner hub of fig. 2, seen in direction ni; Fig. 4 is a cutaway side view through a Kaplan runner hub according to the invention; Fig. 5 is a cutaway view from above of a Kaplan runner hub according to the

invention; and

Fig. 6 illustrates a cross section through a stiffener of fig. 5.

Directional terms, e.g. "upper", "lower", "below", "above", refers to the position of the Kaplan runner in fig. 1.

Fig. 1 is a cutaway side view of a hydroelectric power plant using a Kaplan turbine with a Kaplan runner 1. A concrete foundation 43 supports an electric generator with its stator 49 and rotor 50. A generator shaft 51 extends down from the rotor 50 to a radial bearing 48 and thrust bearing 53, which in turn are supported by a bearing support 54, supported by the concrete foundation 43. The generator shaft 51 is via a coupling 52 connected to a runner shaft 3, which via a coupling 4 is connected to and carries the runner 1. The runner shaft 3 is radially supported by a radial bearing 57, which in turn is supported by a floor structure 58 supported by the concrete foundation 43.

The runner 1 is located in a runner chamber 41, and comprises a hub 2 with blades 8. Water supplied from a not illustrated source enters an inlet chamber 42 and flows down the runner chamber 41 as a water flow 9. A control apparatus 55 with actuators 56 regulates the water flow 9. The water flow acts on the blades and causes the blades 8 and thereby the hub 2, the runner 1, the runner shaft 3, the generator shaft 51 and the generator rotor 50 to rotate around a common axis 5, from now named the hub axis 5.

Fig. 2 is a cutaway side view through a Kaplan runner 1 with a hub 2 according to prior art, which can be coupled to a runner shaft by bolt holes 69. The hub is relatively weak with a relatively small diameter, as discussed in the general part of the invention. The hub has an inner portion 6 and a radially spaced outer portion 7, and the inner and outer portions are structurally interconnected by an are 59 in an upper area of the hub. Trunnions 10, one for each blade 8, are arranged inside the hub 2. A lever 22, the function of which will be described later, is tightly fixed around the trunnion. Each trunnion has a longitudinal trunnion axis 11 extending radially or essentially radially to the hub axis 5. Each trunnion 10 is rotatable about its axis 11 by means of an inner radial bearing 20 between the inner portion 6 of the hub and an inner portion 12 of the trunnion, and an outer radial bearing 21 between the outer portion 7 of the hub and an outer portion 13 of the trunnion. An axial bearing 19 between the outer portion 7 of the hub and the lever prevents the trunnion from moving away from the hub axis 5.

Each blade 8 is attached to a trunnion 10 by means of trunnion bolts 68 extending from the blade 8, through the outer portion 13 of the trunnion and into the lever 22. The outer portion 13 of the trunnion is thereby clamped between the blade 8 and the lever 22, and the blade, the outer portion of the trunnion and the lever thereby forms a stiff unit. The blades are thereby rotatable together with the trunnions, around the trunnion axis 11. Other ways of fastening the blades 8 to the trunnions 10 are possible, and the trunnions and the blades may also be integral. As illustrated in fig. 1, the blades 8 are arranged in the circumferential direction around the outside of the hub 2. The trunnions are correspondingly spaced in the circumferential direction of the hub.

The hub also comprises a trunnion control mechanism for regulating the rotational position of the trunnions 10 around the trunnion axes 11, for regulating the rotational position of the blades 8. This mechanism consists of a central piston 66 fixed to or integral with the inner portion 6 of the hub, and a cylinder 63 movable in the vertical direction. Pressurizing a lower cylinder chamber 65 causes the cylinder 63 to move down, while pressurizing an upper cylinder chamber 64 causes the cylinder 63 to move up. Crossheads 62 formed by extensions of the cylinder 63 is via pivots 67 rotatably connected to upwardly extending links 61.

Fig. 3 is a cutaway side view through the Kaplan runner hub of fig. 2, seen in direction III. Fig. 3 particularly illustrates the control mechanism. Continuing from the description of fig. 2, each link 61 is via a pivot 71 connected to the lever 22. The link 61 and the lever 22 form a crank. A downwardly movement of the cylinder 63 causes the trunnion 10 to rotate clockwise, while an upwardly movement of the cylinder 63 causes the trunnion 10 to rotate counter-clockwise. Fig. 3 also illustrates bolt holes 70 for the bolts 68 in the outer portion 13 of the trunnion. Also illustrated is a lower shell 72 for protecting the internals of the hub 2 against the surrounding water.

For a further explanation of the prior art and problems related to prior art, reference is again made to fig. 2. During operation the water flow 9 a ets on the blade 8. The shape of the blade causes water pressure Pw due to the water flow 9 to rotate the trunnions and thereby the hub 2 around the hub axis 5. The water pressure Pw also creates a bending moment Mb around an axis orthogonal to the paper plane. The rotational velocity of the runner creates a centrifugal force Fc, forcing the trunnion 10, lever 22 and blade 8 outwards against the axial bearing 19, which in turn forces the outer portion 7 of the hub outwards. The combination of the bending moment Mb and the centrifugal force Fc result in high bearing contact pressure Pax in the upper part of the axial bearing 19 and low bearing contact pressure in the lower part of the axial bearing. In some runners, the lower part of the axial bearing 19 may lose contact with its counter surface.

Fig. 4 is a cutaway side view through a Kaplan runner hub according to the invention. Items identical in fig. 2 and 4 will not be described. According to the invention a stiffener 15 connects the inner 6 and outer portion 7 of the hub 2. This stiffener increases the stiffness of the hub 2, and reduces radial and tangential deformation of the outer portion 7 of the hub. The stiffener also greatly reduces the radial expansion of the runner 1 during runaway, making it possible to use a smaller radial play between the runner blades 8 and the runner chamber 41, which increase the efficiency of the Kaplan turbine. The increased stiffness of the hub in turn reduces the high contact pressure of the bearings, and evens the contact pressure. It is seen that the stiffener spans the space between the inner 6 and outer 7 portion of the hub 2. Further the stiffener 15 is located below the trunnion axis 11. Fig. 4 further illustrates that the stiffener 15 is connected to the inner portion 6 of the hub 2 close to the trunnion inner radial bearing 20, and also that the stiffener 15 is connected to the outer portion 7 of the hub 2 close to the trunnion axial bearing 19. The stiffener 15 extends obliquely to the trunnion axis 11, downwardly from the inner portion 6 to the outer portion 7 of the hub 2.

The stiffener may be a welded construction, made from plates or beams of carbon steel or stainless steel, or the stiffener may be a casting, made from east iron or east steel. It is also within the invention to forge the stiffener.

The stiffener 15 may be a single piece extending all the way around the hub 2, or a number of segments or separate items extending circumferentially of the hub 2, each segment extends a part of the way around the hub. As an example, the stiffener 15 may consist of plate segments, each plate segment may be located between and below two adjacent trunnions 10. The stiffener may also consist of separate bars or beams spaced circumferentially of the hub 2, typically between and below two adjacent trunnions 10. The favourable effects of the invention are not dependent upon a ny particular design of the stiffener.

Fig. 5 is a cutaway view from above of a Kaplan runner hub according to the invention. The stiffener 15 is here made from plate, and extends all the way around the hub 2. This stiffener also extends obliquely to the trunnion axis 11, downwardly from the inner portion 6 to the outer portion 7 of the hub 2, like in fig. 4. As seen from fig. 4, most of the trunnion control mechanism is located below the stiffener 15. The stiffener has openings 60 for the links 61 and the crossheads 62, so they can extend through the stiffener 15 and rotate the lever 22.

Fig. 4 and 5 also illustrates how the stiffener 15 is fastened via screw joints, formed by screw holes 73 for screwing the upper portion of the stiffener 15 to the inner portion 6 of the hub 2, and screw holes 74 for screwing the lower portion of the stiffener 15 to the outer portion 7 of the hub 2. Not illustrated screws press the upper and lower portion of the stiffener 15 against the inner 6 and outer portion 7 of the hub 2, respectively, and the friction of shear surfaces of the stiffener and the hub ensure that the stiffener 15 is kept in place. Alternatively, the stiffener 15 may be fastened via not illustrated cylindrical pins. Fig. 6 illustrates a cross section through the stiffener 15 of fig. 5, and illustrates the screw holes 73 and 74 discussed with reference to fig. 4 and 5. Fig. 4 also illustrates another aspect of the invention, namely that the trunnion bearings also comprise, for each trunnion 10, a trunnion inner axial bearing 18 fixed to the inner portion 6 of the hub 2, for preventing the trunnion from moving towards the hub axis 5. The inner axial bearing 18 counteracts a movement of the inner portion 12 of the trunnion due to the bending moment Mb, discussed with reference to fig. 2, and thus reduces the high contact pressure of the bearings discussed with reference to fig. 2. The contact pressure is also made more even. Preferably, as illustrated in fig. 4, the trunnion inner axial bearing 18 is located between the inner portion 6 of the hub 2 and the inner portion 12 of the trunnion 10, and thereby acts directly on the trunnion.

The invention is efficient in reducing deformations of the trunnion-lever-blade assembly using either the stiffener 15 or the inner axial bearing 18. However, when using both these aspects of the invention, the effect is to be considered synergetic.

Claims

1. A Kaplan runner (1), comprising: a hub (2) with a longitudinal hub axis (5), for coupling (4) to a runner shaft (3), the hub has an inner portion (6) and a radially spaced outer portion (7), the inner and outer portions are structurally interconnected (59) in an upper area of the hub; trunnions (10) inside the hub (2), spaced in the circumferential direction of the hub, each trunnion has a longitudinal trunnion axis (11) extending radially to the hub axis (5); trunnion bearings, comprising trunnion radial bearings (20, 21) for allowing the trunnions (10) to rotate around the trunnion axes (11), and trunnion axial bearings (19) for preventing the trunnions from moving away from the hub axis (5); blades (8) outside the hub (2), each blade (8) is attached to or integral with a trunnion (10), for rotating the trunnions and thereby the hub (2) around the hub axis (5) by the action of flowing water (9); a trunnion control mechanism (22, 61, 62, 63, 64, 65, 66) for regulating the rotational position of the trunnions (10) around the trunnion axes (11), for regulating the blades (8),characterized incomprising a stiffener (15) connecting the inner (6) and outer (7) portion of the hub (2).

2. A Kaplan runner (1) according to claim 1, wherein the stiffener (15) spans the space between the inner (6) and outer (7) portion of the hub (2).

3. A Kaplan runner (1) according to claim 1 or 2, wherein the stiffener (15) is located below the trunnion axis (11).

4. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is connected to the inner portion (6) of the hub (2) close to the trunnion inner radial bearings (20).

5. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is connected to the outer portion (7) of the hub (2) close to the trunnion axial bearings (19).

6. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) extends circumferentially of the hub (2).

7. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) extends all the way around the hub (2).

8. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) extends obliquely to the trunnion axis (11).

9. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) extends downwardly from the inner portion (6) to the outer portion (7) of the hub (2).

10. A Kaplan runner (1) according to any preceding claims, wherein at least some of the trunnion control mechanism (22, 61, 62, 63, 64, 65, 66) is located below the stiffener (15), and the stiffener has openings (60) for the trunnion control mechanism.

11. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is made from plate.

12. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is a welded construction.

13. A Kaplan runner (1) according to any of the claims 1-10, wherein the stiffener (15) is a casting.

14. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is fastened via screw joints (73, 74).

15. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is fastened via shear surfaces.

16. A Kaplan runner (1) according to any preceding claims, wherein the stiffener (15) is fastened via cylindrical pins.

17. A Kaplan runner (1) according to any preceding claims, wherein the trunnion bearings (19, 20, 21) also comprise, for each trunnion (10), a trunnion inner axial bearing (18) located at the inner portion (6) of the hub (2), for preventing the trunnion (10) from moving towards the hub axis (5).

18. A Kaplan runner (1) according to claim 17, wherein the trunnion inner axial bearing (18) is located between the inner portion (6) of the hub (2) and the trunnion (10).