WO2015031987A1

WO2015031987A1 - Spiral casing for a hydraulic turbine and method for arranging a spiral casing

Info

Publication number: WO2015031987A1
Application number: PCT/CA2014/050741
Authority: WO
Inventors: Nigel Murry; Christine Monette; Normand Desy
Original assignee: ANDRITZ HYDRO Ltd
Current assignee: ANDRITZ HYDRO Ltd
Priority date: 2013-09-05
Filing date: 2014-08-07
Publication date: 2015-03-12
Anticipated expiration: 2016-03-05
Also published as: RU2016112544A3; RU2016112544A; CA2922196A1; CN105849405A; CN105849405B; RU2668189C2

Abstract

A spiral casing for a hydraulic turbine has been conceived including: an array of spiral segments defining a passage to direct liquid entering the casing to a runner in the turbine, the spiral segment extending at least partially around the runner and having an inner perimeter defining an opening to receive the runner, the cross- sectional areas of the spiral segments gradually decrease from an inlet one of the spiral segments to a last one of the spiral segments, wherein each of the spiral segments includes a gap aligned with the opening and the cross sections of the spiral segment do not correspond to a circular cross section; an inlet segment defining a passage to receive liquid to flow into the spiral segments, wherein the inlet segment is circular in cross section, and a transition segment connecting the inlet segment to one of the spiral segments and defining a passage to direct liquid passing from the inlet segment to the spiral segments, wherein the transition segment is non-circular in cross section along at least a portion of its length.

Description

SPIRAL CASING FOR A HYDRAULIC TURBINE AND METHOD FOR ARRANGING A SPIRAL CASING

BACKGROUND

[0001] The present invention relates to a spiral casing for a turbo-machine and particularly to a spiral casing for a hydraulic turbine, such as Francis, Kaplan and Pelton turbines.

[0002] FIG. 1 shows a conventional Francis turbine 10 that includes a spiral casing 12, an annular array of stay vanes 14, an annular array of guide vanes 15, a runner 16 and a draft tube 18. The spiral casing 12 forms an enclosed passage for water entering the turbine 10. The inner circumference 20 of the spiral casing 12 is open to water flowing from the spiral casing 12 towards the runner 16. The stay vanes 14 and guide vanes 15 orient the flow of water as it enters the runner 16. The water rotates the runner 16 about an axis 19 that is commonly a vertical axis. The rotation drives a shaft 22 that may be coupled to an electrical generator. Water passing through the runner 16 is turned from a generally circular flow in the spiral casing 12 to a generally helical flow in the draft tube 18. The axis of the helical flow is concentric with the axis 19 of the runner.

[0003] FIG. 1 shows a conventional spiral casing 12 which is substantially circular in cross section. The non-circular portion corresponds to the opening at the inner circumference 20 of the casing. The spiral is often an assembly of segments arranged around the axis of the runner. Each segment may be a metal panel(s) shaped to form a wall of the passage. Each segment may include one or more of the stay vanes 14.

[0004] The diameters of each segments decrease successively as the assembly of segments progresses around the axis. Thus, the flow passage through the spiral casing 12 has a large diameter (Dl) at an inlet segment 26. The diameters (see D2) of the successive segments gradually decrease as the casing wraps around the outer circumference of the guide vanes 14 and runner 16. The spiral casing 12 typically wraps one circumference or nearly one circumference around the guide vanes 15 and runner 16.

[0005] FIG. 2 shows a conventional spiral casing 12 seated in a chamber 24 formed by concrete walls in a power house. A center cylindrical opening 31 in the spiral casing 12 receives the guide vanes 15 and the runner 16. The inlet segment 26 of the spiral casing 12 is aligned with a water inlet to the chamber 24. The inlet segment 26 conventionally has a straight axis 28 and is circular in cross-section throughout its length. The inner sidewall of the inlet segment 26 is tangent line 30 to the circumference of the cylindrical opening 31. Each segment may also have a straight axis, but the axes of the segments are not on a common axis. Rather, the axis of each segment may be angled with respect to the axes of the preceding and succeeding segment.

[0006] The inlet segment 26 to the spiral casing 12 defines a first outer edge 33 of the spiral casing 12. The distance (D3) from the first outer edge to the opposite outer edge 35 is often thirty feet (10m) or greater. The width and length of the chamber 24 is sized to receive the spiral casing 12. The chamber 24 is typically a large concrete structure that may be 20 to 60 feet high (8 to 20 meters) and 50 to 80 feet (12 to 18 meters) in length and width. The chambers 24 must be

constructed on site of the power house where the water turbine is to operate.

Construction of the chambers 24 tends to be costly and labor intensive.

SUMMARY OF INVENTION

[0007] There is a long felt need to reduce the cost and labor required to install a Francis water turbine and the chamber for the turbine. The size of the chamber depends on the overall size of the spiral casing. Reducing the external dimension (D4 - FIG. 3) of the spiral casing would allow the size of the chamber to be reduced. The spiral casings disclosed herein may be applied to various types of hydro-turbines, including Francis, Kaplan, Pelton and diagonal flow type turbines.

[0008] The external dimension (D4) of the spiral casing may be reduced by shaping the cross-sectional shapes of the spiral segment of the casing, shifting inward the inlet segment and adding a transition segment between the inlet and the spiral segments. The inlet segment may be shifted by moving the inlet laterally towards the rotational axis of the turbine as shown in FIG. 3. The inlet segment may also be effectively shifted by rotating the turbine with respect to the axis of the powerhouse machines as shown in FIG. 4. If the turbine is rotated, the inlet segment may be kept perpendicular to the machine axis 73 by rotating the non- radial segments about their attachment points to the other segments.

[0009] The cross-sectional shapes of the spiral and transition segments are non- circular. The cross sections of the spiral and transition segments may be elliptical, parabolic or hyperbolic segment shape or other non-circular shape with a continuous tangent. The continuous tangent indicates that the cross section is continuously curved. These cross-sectional shapes may have a narrower width (perpendicular to the rotational axis of the turbine) and a greater height (parallel to the rotational axis) than the circular cross sections in conventional spiral casings. The non-circular cross sections of the spiral segment are configured to have sufficient area for the water needed for the turbine. By shaping the cross sections of the segments of a spiral, the overall dimension (D4) of the spiral segment may be reduced as compared to the dimension (D3) of a spiral casing having segments all with substantially circular cross sections.

[0010] The transition segment is between the end of the inlet segment and the first spiral segment. The transition segment forms a passage for water moving from the inlet segment to the spiral segments. The cross sections of the transition segment may be non-circular, such as elliptical, parabolic or hyperbolic. The transition segment may gradually change from having a circular cross section at its coupling to the inlet segment to a non-circular cross section at its coupling to the first spiral segment.

[0011] A spiral casing for a hydraulic turbine has been conceived including: an array of spiral segments defining a passage to direct liquid entering the casing to a runner in the turbine, the spiral segment extending at least partially around the runner and having an inner perimeter defining an opening to receive the runner, the cross-sectional areas of the spiral segments gradually decrease from an inlet one of the spiral segments to a last one of the spiral segments, wherein each of the spiral segment includes a gap aligned with the opening and the cross sections of the spiral segment do not correspond to a circular cross section; an inlet segment defining a passage to receive liquid to flow into the spiral segments, wherein the inlet segment is circular in cross section, and a transition segment connecting the inlet segment to one of the spiral segments and defining a passage to direct liquid passing from the inlet segment to the spiral segments, wherein the transition segment is non-circular in cross section along at least a portion of its length.

[0012] The machine may be rotated by an angle in a range of 5 degrees to 40 degrees, for example, with respect to the axis of the powerhouse machine and about the rotational axis of the runner blades. The powerhouse machine axis is in a horizontal plane. The inlet segment may be laterally shifted towards a rotational axis of the turbine. The cross-sectional shapes of the spiral and transition segments may be elliptical, parabolic or hyperbolic segment shape.

[0013] A spiral casing for a hydraulic turbine has been conceived comprising: an assembly of spiral segments joined end-to end to define a passage to direct water entering the spiral casing to a runner in the hydraulic turbine, wherein the assembly of spiral segments defining an inner opening configured to receive an array of vanes and a runner of the hydraulic turbine and each spiral segment in the assembly has a gap aligned with the inner opening and has a non-circular cross- sectional shape; an inlet segment defining a passage to receive the water to flow into the assembly of spiral segments, wherein the inlet segment is circular in cross section along an entire length of the inlet segment, and a transition segment connecting the inlet segment to the assembly of spiral segments and defining a passage to direct water passing from the inlet segment to the assembly of spiral segments, wherein the transition segment is non-circular in cross section along at least a portion of a length of the transition segment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a side view, shown partially in cross section, of a conventional Francis type hydraulic turbine.

[0015] FIG. 2 is perspective view of a spiral casing for a Francis type water turbine positioned in a chamber for the turbine.

[0016] FIG. 3 is a schematic top down view of a spiral casing having a transition segment changing from a circular cross-section to a non-circular cross-section along its length and shifting the inlet segment.

[0017] FIG. 4 is a schematic top down view of a rotated spiral casing having a transition segment changing from a circular cross-section to a non-circular cross- section along its length.

[0018] FIG. 5 is a schematic end view of a spiral segment. DETAILED DESCRIPTION

[0019] FIG. 3 is a schematic top down view of a spiral casing 32 having a transition segment 34 between an inlet segment 36 and a spiral segment 37, 38. The inlet segment 36 is shifted laterally inwards towards the rotational axis 40 of the turbine. The cross sections of the spiral segments 37, 38 and transition segment 34 are non-circular, such as elliptical, parabolic or hyperbolic. [0020] The overall dimension (D4) of the spiral casing 32 may be five to ten percent smaller than the corresponding overall dimension (D3) of the conventional spiral casing 12 to be replaced by the spiral casing 32. The reduction in the overall dimension is achieved by shifting 41 the inlet segment 36 and making non-circular the cross sections of the spiral segments 37, 38 and transition segment 34.

[0021] The reduction in the overall dimension (D4) of the spiral casing 32 is evident from the differences between the solid lines showing the spiral casing with a shifted inlet segment, and the dashed lines that show the perimeter of a corresponding conventional spiral casing. The distances between the dashed and the solid lines provide an exemplary representation of the relative overall reduction in size of the spiral casing.

[0022] The inlet segment 36 has a circular cross-section throughout its length. The diameter of the circular cross-sections need not remain constant along the length of the inlet segment 36. For example, the inlet segment 36 may be cylindrical or may converge or expand along its length. A circular cross section of the inlet segment 36 is suited to withstand the extreme hydraulic pressure of the water flow through the inlet segment 36. The inlet segment 36 may have a straight axis 46 or may be curved.

[0023] The connection of the inlet segment 36 to the initial spiral segment 37 is achieved by the transition segment 34. The transition segment 34 provides a smooth transition of the water passage from the inlet segment 36 to the spiral segment 37. [0024] The transition segment 34 includes an inlet region having a circular cross section that connects to the inlet segment 36. The inlet to the transition segment 34 is circular in cross section to match and couple to the inlet segment 36. The outlet from the transition segment 34 has a cross-sectional shape that matches the inlet to the initial spiral segment 37. The cross-sectional shapes of the transition segment 34 at the outlet of the segment are generally non-circular, such as elliptical, parabolic or hyperbolic.

[0025] The transition segment 34 may be formed by rolling a steel plate into the desired shape. Alternatively, the transition segment 34 may be formed by combining end-to-end short tubular segments. Shaping the transition segment 34 is used to provide a connection between the laterally shifted inlet segment 37 and the initial spiral segment 38. Because of its lateral shift 41, the inlet segment 36 is not aligned with the inlet to the initial spiral segment 38. In a conventional spiral casing, the inlet segment is aligned with the initial spiral segment and both share similar cross-sectional shapes that allow the segments to be coupled together.

[0026] The spiral casing 32 may be formed by assembling end-to-end tubular sections each forming one of the spiral segments 38. The spiral segments 37, 38, as well as the transition segment 34 and the inlet segment 36, may be formed by rolling carbon steel plates. The segments may be shipped separately and

assembled at the chamber of the power house.

[0027] The cross-sectional area of the spiral segments 37, 38 gradually decreases in a direction of the water flow through the spiral casing 32. The cross-sectional shapes of the spiral segment 37, 38 may be, for example, elliptical, parabolic or hyperbolic. The cross sections of the spiral segments include a gap 20 and thus do not form a closed elliptical, parabolic, hyperbolic or other non-circular shape. The cross sections of the spiral segments and the transition segment are referred to as being non-circular because the profiles of the cross section do not conform to a circle. Rather, the profiles of the cross sections of the spiral and transition segments conform to a non-circular shape, such as a elliptical, parabolic or hyperbolic shape.

[0028] By shaping of the cross sections of the spiral segments 37, 38, the outer perimeter of the spiral casing 32 is shifted 43 radially inward towards the rotational axis 40 of the turbine. The shaping of the spiral segments 37, 38 may increase the height (parallel to the rotational axis 40) as compared to spiral segments that are circular in cross section. However, an increase in height of the spiral casing 32 may be acceptable to achieve a reduction in the over all dimension (D4 from D3) of the spiral casing.

[0029] The inlet segment 36 may have an outer surface 52 that is straight and aligned, such as coaxially, with the straight outer 54 of the transition segment 34. The outer surfaces of the inlet segment 36, transition segment 34 and spiral segments 37, 38 are the outermost surfaces of the spiral casing 32 in a plane perpendicular to the rotational axis 40 and extending through a mid-section of the guide vanes 56. Due to its shift 41, the inner surface 58 of the inlet segment 36 is not tangent to the circular opening 42 formed by the inner perimeter of the spiral casing 32. [0030] The thickness of the walls of the transition segment 34 and spiral segments 37, 38 may be increased as compared to the wall thickness of a conventional spiral casing. The thicker walls may be needed to withstand the hydraulic pressure and ensure that the transition and spiral segments retain their intended non-circular cross sectional shapes.

[0031] The opening 42 in the spiral casing 32 receives the runner (FIGURE 1) and an annular assembly of guide vanes 56. The angle of the guide vanes 56 may be adjusted to change the flow direction of the water entering the runner blades. The guide vanes 56 may be adjusted by being turned about their axes.

[0032] An annular assembly of stay vanes 62 is concentric with the assembly of guide vanes 56. The stay vanes 62 span the gap in the opening 61 formed in the sidewall of spiral segment 38. The opening 61 provides a passage for water flowing from the spiral segments 37, 38 to the guide vanes 56 and runner. The stay vanes 62 also provide structural support for the spiral segments 37, 38. The stay vanes 62 may be aligned to be parallel to the flow direction of the water passing from the spiral segments 37, 38 to the guide vanes 56.

[0033] A baffle plate 44 connects the end of the last spiral segment 38 to the side of the transition segment 34 and optionally to the inlet segment 36. The baffle plate 44 may be a carbon steel plate shaped to conform to the inner perimeter of the transition segment 34 and inlet segment 36, and to provide an end plate to the spiral segment 38. The baffle plate prevents water flowing from the last spiral segment into the transition or inlet segments. [0034] FIG. 4 is a schematic top down view of a spiral casing 64. The spiral casing may be designed by rotating a conventional casing shape (see dashed lines), such as a casing to be replaced. The shape of the spiral casing is rotated during design about an axis 73 of the hydraulic turbine for the casing. The effective rotation of the casing shape is an angle 70 of, for example, five to forty degrees (5° to 40°). Rotation of the inlet segment 68 assists in reducing the overall dimension (D5) of the spiral casing 64. The rotation and the non-circular cross-sections of the transition segment 66 and the spiral segments 72 reduce the overall dimension (D5) of the spiral casing 64. The overall all dimension (D5) is the outer surface of the spiral casing along line 74 which extends perpendicularly through the axis 73.

[0035] The inlet, transition and spiral segments may be each shaped to by rolling a respective carbon steel sheet or plate. The inlet segment 68 may have a circular cross section. The cross sections of the transition segment 66 and the spiral segments 72 may be entirely or partially non-circular, such as elliptical, parabolic or hyperbolic cross-sectional shapes. The axis of the inlet segment may be coaxial with the axis of the transition segment as shown in FIG. 4.

[0036] A spiral casing formed by rotating a spiral casing as shown in FIG. 4 may be further formed to having an inlet segment that is parallel to the inlet segment of the casing to be replaced. Such a spiral casing may have a shape as shown in FIG. 3. The transition segment for such a spiral casing would be similar to the transition segment 54 shown in FIG. 3. The axis of the inlet segment may be oblique with respect to the axis of the transition segment as shown in FIG. 3. [0037] FIG. 5 is a schematic diagram showing an end a spiral segment 82. The segment 82 has a metal sidewall 84 that defines a perimeter of a water passage 86. The cross section of the sidewall 84 along an axis 85 of the segment is non- circular is shown by the solid parallel lines in Figure 5. The cross-section may be, for example, elliptical, parabolic or hyperbolic segment shape. A circular cross section shown be dashed lines is in Figure 5 for purposes of comparison with the non-circular cross section of the segment.

[0038] The reduction along a plane 88 through the spiral segment 82 is the distance 87 between the outer perimeter of the sidewall 84 and the circular illustrated by the dashed line. The horizontal plane 88 passes through the mid-span of the stay vanes 62 and includes the power house machine axis 73. All or most of the spiral segments 82 in the assembly of segments that form the spiral casing may have one or more stay vanes 62 that span a gap 90 at the inner perimeter 92 of the spiral segment 82. The gap 90 provides a passage for water flowing from the water passage 86, through the guide vanes and into the runner. The stay vanes 62 may be supported by annular flanges 94 at the upper and lower edges 96 of the gap 90. The flanges 94 may also support the edges 96 of the sidewall 84 forming the spiral segment 82. The flanges 94 may be secured to the chamber in the power house.

[0039] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A spiral casing for a hydraulic turbine comprising:

an array of spiral segments defining a passage to direct liquid entering the casing to a runner in the turbine, the spiral segment extending at least partially around the runner and having an inner perimeter defining an opening to receive the runner, the cross-sectional areas of the spiral segments gradually decrease from an inlet one of the spiral segments to a last one of the spiral segments, wherein each of the spiral segments includes a gap aligned with the opening and the cross sections of the spiral segment do not correspond to a circular cross section;

an inlet segment defining a passage to receive liquid to flow into the spiral segments, wherein the inlet segment is circular in cross section, and

a transition segment connecting the inlet segment to one of the spiral segments and defining a passage to direct liquid passing from the inlet segment to the spiral segments, wherein the transition segment is non-circular in cross section along at least a portion of its length.

2. The spiral casing of claim 1 wherein an axis of the inlet segment is oblique with respect to an axis of the transition segment.

3. The spiral casing of claim 2 wherein the axis of the inlet segment forms an angle in a range of 5 degrees to 40 degrees with respect to the axis of the transition segment.

4. The spiral casing of any of claims 1 to 3 wherein an axis of the inlet segment is coaxial to an axis of the transition segment.

5. The spiral casing of any of claims 1 to 4 wherein the inlet segment is laterally shifted towards a rotational axis of the turbine.

6. The spiral casing of any of claims 1 to 5 wherein the cross sections of the spiral segment are at least partially one of elliptical, parabolic and hyperbolic in shape.

7. The spiral casing of any of claims 1 to 6 wherein the cross sections of the transition segment include cross-sections having a height dimension greater than a width dimension.

8. The spiral casing of any of claims 1 to 7 wherein the cross sections of the transition segment include a circular-cross-section adjacent the inlet segment.

9. A spiral casing of a hydraulic turbine comprising:

an assembly of spiral segments joined end-to end to define a passage to direct water entering the spiral casing to a runner in the hydraulic turbine, wherein the assembly of spiral segments defining an inner opening configured to receive an array of vanes and a runner of the hydraulic turbine and each spiral segment in the assembly has a gap aligned with the inner opening and has a non-circular cross- sectional shape;

an inlet segment defining a passage to receive the water to flow into the assembly of spiral segments, wherein the inlet segment is circular in cross section along an entire length of the inlet segment, and

a transition segment connecting the inlet segment to the assembly of spiral segments and defining a passage to direct water passing from the inlet segment to the assembly of spiral segments, wherein the transition segment is non-circular in cross section along at least a portion of a length of the transition segment.

10. The spiral casing of claim 9 wherein a spiral segment in the assembly has a smaller diameter than a preceding spiral segment in the assembly.

11. The spiral casing of claim 9 or 10 wherein an axis of the inlet segment is oblique to an axis of the transition segment.

12. The spiral casing of claim 11 wherein the axis of the inlet segment forms an angle in a range of 5 degrees to 40 degrees to the axis of the transition segment.

13. The spiral casing of any of claims 9 to 12 wherein an axis of the inlet segment is coaxial to an axis of the transition segment.

14. The spiral casing of any of claims 9 to 13 wherein the inlet segment is laterally shifted towards a rotational axis of the turbine.

15. The spiral casing of any of claims 9 to 14 wherein the cross sections of the spiral segment are at least partially one of elliptical, parabolic and

hyperbolic in shape.

16. The spiral casing of any of claims 9 to 15 wherein the cross sections of the transition segment include cross-sections having a height dimension greater than a width dimension.

17. The spiral casing of any of claims 9 to 16 wherein the cross sections of the transition segment include a circular-cross-section adjacent the inlet segment.

18. The spiral casing of any of claims 9 to 17 wherein each of a plurality of the spiral segments includes a vane in the gap of the segment.

19. The spiral casing of any of claims 9 to 18 wherein a baffle plate joins the assembly of spiral segments to a sidewall of the inlet segment.