Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Hydraulic Machine
This invention relates to a hydraulic machine, in particular a hydro turbine,
pump turbine
or pump. These may be machines of the Francis
design, the Kaplan design, or other machines. The essential thing is that
these are
machines with a spiral housing.
By way or example, reference is made to US-A-4 496 282 or DE 199 50 228 Al.
The spiral housing of such a machine surrounds the wheel and is positioned at
a plane
vertical to the wheel's axis. Since the axis of the wheel generally extends
vertically, this
is a horizontal plane.
The spiral housing is open on the inside facing the wheel. It features a slit
circling the
inner circumference of the spiral housing so that the medium can flow from the
spiral
housing through the slot to the wheel around the entire inner circumference.
Thus, the slit
is defined by two circumferential edges.
The said slit is connected in the direction or the flow to a ring of crossbars
comprising
two crossbar ring decks arranged concentrically in relation to the axis of the
wheel and
are evenly spaced in the axial direction. The decks are connected via tie-
bars, i.e., the so-
called crossbars. In addition, each of the above-mentioned circumferential
edges of the
spiral casing is firmly connected to one of the two crossbar ring decks,
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The crossbar ring serves to prevent the spiral casing from expanding under the
high
20 internal pressure.
Thus, the above-mentioned tie-bars, as well as the point of connection between
each
respective crossbar ring deck and the associated circumferential edge of the
spiral
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housing, are exposed to certain forces. The connection must have an absolutely
reliable
design that is capable of resisting extreme force. It must also be taken into
account that
pressure fluctuations or oscillations may occur.
Substantial efforts have been made to provide a permanent and stable design
for the
connection while using as little material as possible. Generally, this is a
welded
connection between the respective circumferential edge of the spiral housing
and the
associated crossbar ring deck. This connection has proven to be expensive and
time-
consuming to produce.
The underlying task of this invention is to design a hydraulic machine of the
type
to mentioned above, featuring a spiral housing and a crossbar ring. it
should be designed in
such a way that the connection between the circumferential edges of the slit
in the spiral
housing and the associated crossbar ring deck is even safer than with
previously known
machines.
Accordingly. in one of its aspects, the present invention provides a hydrolic
machine comprising:
1.1 with a wheel (1) featuring a multitude of blades (1.1):
1.1 with a spiral housing (3) surrounding the wheel (1) and lacing it with a
circumferential slit formed by
two eircJinferential edges (3.1. 3.2):
1.3 with a crossbar ring (4) comprising two crossbar ring decks (4.1,4.2)
connected via tie-bars (4.3);
1.4 the spiral housing (3) is connected to the crossbar ring decks (4.1, 4.2)
in the area of the
circumferential edges (3.1. 3.2):
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characterized by the famine properties:
20 1.5 the areas of the circumferential edges are designed in such a way or
are arranged in such a way that
they both extend parallel to the axis (2) of the wheel (I) or form an angle,
a, of no more than I I degrees
µvith the axis of the wheel.
According to the said claim, the sections of the circumferential edges of the
spiral
housing ¨ viewed as an axial section ¨ are formed in such a way that they are
25 approximately parallel to the axis of the wheel. A minor deviation from
parallelism is
permissible. However, it should not be more than it degrees. A small deviation
of 1, 2, 3,
4, S. 6 degrees can be advantageous given that the circumferential edge shows
a minor
inclination towards the axis of the wheel. In practice, the variation will be
between Sand
1 degrees.
30 The spiral housing is usually composed of segments. Viewed in an axial
cross-section,
the segments are roughly circular in shape, except, of course, for the edge
areas. Outside
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the edge areas, however, the shape of the segments may also deviate from the
circular
shape, as can be seen in the figures.
The invention presents the following advantages:
The stresses in the entire spiral housing are largely uniform. The forces and
momentums
5 exercised on the crossbars are at a minimum. At the point of connection
between the
edges of the spiral housing and the crossbar rings, the flexural stresses that
occur are
minor.
Due to the even distribution of stress, all components involved can be
provided with an
optimized design. This results in a minimized wall strength of the spiral
casing and the
cross-sections of the crossbars.
This can be achieved as follows:
The relevant edge area of the spiral housing is designed in such a way that,
due to the
edge, an area tangential to the spiral housing is nearly parallel to the
turbine axis. In that
ease, the cross-section of the spiral housing deviates from the circular shape
it normally
takes, at least in the connection area.
The beneficial effect can be explained as follows: Minor force components of
tensile
force with a radial outwards or inwards effect occur, affecting the walls of
the spiral
housing.
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The current state of the art as well as the invention are explained in detail
based on the
20 drawing. The individual figures show as follows:
Figure 1: shows the essential components of a conventional Francis turbine
in a
meridian section.
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Figure 2: shows a meridian section of a spiral housing with both crossbar
ring decks
of a crossbar ring according to a first embodiment of the invention.
Figure 3: shows a meridian section of a spiral housing with both crossbar
ring decks
of a crossbar ring according to a second embodiment of the invention.
Figure 4: shows a three-dimensional representation of the first embodiment
of the
invention.
The Francis turbine shown in Figure 1 features a wheel (1) comprising a number
of
blades (1.1). The wheel (1) revolves around an axis (2).
The wheel ( I) is surrounded by a spiral housing (3). The spiral housing (3)
may feature a
circular cross-section, for example. It has a circumferential, slit-shaped
opening to the
wheel (1). The opening slit is limited by the circumferential edges (3.1,
3.2).
A crossbar ring (4) connects to the circumferential slit formed by the edges
(3.1, 12).
The crossbar ring features two crossbar ring decks (4.1 and 4.2). One crossbar
(4.3)
serves as a tic-bar.
The areas of the circumferential edges (3.1, 3.2) of the spiral housing are
welded to the
crossbar ring decks (4.1, 4.2).
Between the crossbar ring and the wheel is a guide vane apparatus with a vane
(5).
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A suction pipe (6) featuring multiple sections is connected to the wheel (1)
in the
direction of the flow.
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As can be seen, the spiral housing has a circular cross-section. The areas of
the
circumferential edges are tilted towards the vertical at the points of
connection to the two
crossbar ring decks (4,1, 4.2). This means that the edge areas of the spiral
housing do not
extend parallel to the axis (2) of the wheel (1). See angle a in Figure 1.1t
is at
approximately 15 to 40 degrees.
Figures 2 and 3 demonstrate two different embodiments of the invention. For
the rest, the
related hydraulic machinery can be designed the same way as the machine shown
in
Figure 1.
Both embodiments according to Figures 2 and 3 share the characteristic that
the spiral
housings stand nearly vertically on the connection areas of the related
crossbar ring decks
(4.1,4.2) in the area of the circumferential edges (3.1, 3.2).
In the embodiment shown in Figure 2, this is achieved through the deformation
of the
edge areas of the spiral housing (3) from the circular form. They extend
practically
parallel to the axis (2) according to Figure I. They are attached by means of
welded
seams (7).
In the second embodiment according to Figure 3, the crossbar rings (4.1, 4.2)
have a
conventional shape and arrangement. The edge areas (3.1, 3.2) stand vertically
on the
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crossbar ring decks (4.1, 4.2) and, accordingly, extend parallel to the axis
(2) of the wheel
(I). The remaining cross-section of the spiral housing (3) is roughly
elliptical.
From the viewpoint of the even distribution of stresses, the execution of
Figure 2 is
preferable over that of Figure 3.
The third embodiment of the invention, shown in Figure 4, features more or
less
conventional crossbar ring decks (4.1, 4.2). However, the cross-section of the
spiral
housing does not form a single circle but consists of three arcs: namely, a
first arc
15 [paragraph
continued on next page]
=
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(3.3) and a second and third arc (3.4, 3,5). The first arc (3.3) features a
relatively large
radius RI, while the other two arcs (3.4, 3.5) both feature a relatively small
arc R2.
The connection points between the spiral housing (3) ¨ in this case, the two
arcs (3.4,
3.5), on the one hand, and the crossbar ring decks (4.1, 4.2), on the other
hand ¨ are
nearly perpendicular.
The tie-bar (4.3) extends in the same direction as the two edge areas of the
circumferential edges (3.1, 32) of the spiral housing (3). The lines of the
tensile strengths
in the tie-bar (43) and the edge areas of the arcs (3.4, 3.5) are aligned.
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Reference List
1 Wheel
1.1 Blades
2 Axis
3 Spiral housing
3.1 Circumferential edge of the spiral housing
3.2 Circumferential edge of the spiral housing
3.3 First arc with large diameter
3.4 Second arc with smaller diameter
3.5 Third arc with smaller diameter
4 Crossbar ring
4.1 Crossbar ring deck
4.2 Crossbar ring deck
4.3 Crossbar
5 Vane
6 Suction pipe
7 Welded scams
