U.S. patent application number 10/538957 was filed with the patent office on 2007-01-11 for method and device for reducing pressure fluctuations in an induction pipe of a water turbine or water pump or water-pump turbine.
Invention is credited to Peter Faile, Thomas Scherer.
Application Number | 20070009352 10/538957 |
Document ID | / |
Family ID | 32477653 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070009352 |
Kind Code |
A1 |
Faile; Peter ; et
al. |
January 11, 2007 |
Method and device for reducing pressure fluctuations in an
induction pipe of a water turbine or water pump or water-pump
turbine
Abstract
The invention relates to a turbine or pump or pump turbine,
comprising a rotor which has a plurality of rotating blades and a
hub, a housing which has a distributor for regulating the currents
flowing into the rotor, and an induction pipe for guiding the water
flowing out of the rotor, comprising an inlet diffusor. The
inventive turbine or pump or pump turbine is characterized by the
following characteristics; an elongate displacement body is
arranged in the induction pipe and the upstream end of the
displacement body is arranged in the region of the hub of the
rotor.
Inventors: |
Faile; Peter; (Giengen,
DE) ; Scherer; Thomas; (Heldenheim, DE) |
Correspondence
Address: |
OHLANDT, GREELEY, RUGGIERO & PERLE, LLP
ONE LANDMARK SQUARE, 10TH FLOOR
STAMFORD
CT
06901
US
|
Family ID: |
32477653 |
Appl. No.: |
10/538957 |
Filed: |
December 4, 2003 |
PCT Filed: |
December 4, 2003 |
PCT NO: |
PCT/EP03/13664 |
371 Date: |
August 31, 2006 |
Current U.S.
Class: |
415/203 |
Current CPC
Class: |
Y02E 10/223 20130101;
Y02E 10/20 20130101; F03B 3/02 20130101; Y02E 10/226 20130101; F03B
11/04 20130101 |
Class at
Publication: |
415/203 |
International
Class: |
F01D 1/02 20060101
F01D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2002 |
DE |
10258557.1 |
Claims
1-7. (canceled)
8. A turbine for pumping a medium comprising: a runner having one
or more rotor blades and a hub; a housing having a distributor that
regulates flow of the medium into the runner; a draft tube that
guides the medium flowing out from the runner and having an inlet
diffuser; and a displacement unit in the draft tube and having an
upstream end in proximity to the hub, wherein the displacement unit
has a variable width.
9. The turbine of claim 8, wherein the width of the displacement
unit increases in the direction of flow of the medium.
10. The turbine of claim 8, wherein between the hub and the
upstream end of the displacement unit is a distance that is between
0.5 mm and 50 mm.
11. The turbine of claim 8, wherein the displacement unit is
supported by rods connected to the draft tube.
12. The turbine of claim 8, wherein the displacement unit is
supported on the hub of the runner.
13. The turbine of claim 8, wherein the displacement unit is
integrally formed with the hub of the runner and rotates with the
hub.
14. The turbine of claim 8, wherein the draft tube runs along a
substantially straight line.
15. The turbine of claim 8, wherein the draft tube is curved.
16. The turbine of claim 8, wherein the displacement unit extends
substantially longitudinally in the draft tube.
17. The turbine of claim 8, wherein the width of the displacement
unit is tapered in the direction of flow of the medium.
18. The turbine of claim 8, wherein the medium being pumped is
water.
19. A method of reducing pressure fluctuations in a turbine that
pumps a medium, the method comprising: regulating flow of the
medium into a runner via a distributor in a turbine housing;
guiding the medium flowing out from the runner via a draft tube;
and reducing swirling of the medium by varying an inner
cross-sectional area of the draft tube in proximity to the
runner.
20. The method of claim 19, wherein the inner cross-sectional area
of the draft tube is varied by positioning a displacement unit of
varying width in the draft tube.
21. The method of claim 20, wherein the width of the displacement
unit increases in the direction of flow of the medium.
22. The method of claim 21, wherein between a hub of the runner and
an upstream end of the displacement unit is a distance that is
between 0.5 mm and 50 mm.
23. The method of claim 20, wherein the displacement unit is
supported by rods connected to the draft tube.
24. The method of claim 20, wherein the displacement unit is
integrally formed with the hub of the runner and rotates with the
hub.
25. The method of claim 20, wherein the draft tube runs along a
substantially straight line.
26. The method of claim 20, wherein the draft tube is curved.
27. The method of claim 19, wherein the medium being pumped is
water.
Description
[0001] The invention relates to a turbine or pump or pump turbine,
particularly to the suction pipe thereof which serves for guiding
the water flowing out of the turbine to the downstream water. The
invention primarily relates to Francis type machines, but also
Kaplan type turbines may come into consideration.
[0002] Regarding water turbines such as Francis turbines there is
an increasing demand for higher efficiencies as well as for an
extended range of operation as well as for a higher flexibility
regarding the rate of flow between partial load and overload. The
efficiency should be high over the whole range of operational
parameters, and at the same time the vibration of the turbine
should be low.
[0003] The adjustment of Francis turbines to variable operational
parameters is made by respective positioning of guide vanes.
Nevertheless there are instable flow conditions, particularly at
partial load, which result in heavy vibrations at the turbine. As a
consequence, there may occur damages to specific components,
particularly in case the characteristic frequencies of such
components coincide with the said frequencies. Also, vibrations of
the said kind may be particularly disadvantageous with large
machines in that the said vibrations may affect the electric
network. Rotational instabilities will be fed into the electric
power supply via the generator, thereby resulting in voltage
fluctuations. This necessitates disadvantageous limitations of the
operational range of the turbine. Critical partial load ranges
during start up of the turbine have to be run through rapidly.
[0004] When operated optimumly, the water flows from the inlet
gates of a Francis turbine axially symmetrically into the runner,
where it is deviated by the guide vanes such that it flows axially
into the suction pipe and further to the downstream water. The flow
in the suction pipe at optimum conditions will be irrotational. At
operational conditions of the turbine outside of the optimum,
however, there will be torsion of the flow downstreams of the
runner. There is no firm knowledge of the dependence between the
rotational component of the flow in the suction pipe and the
vibrations of the machine. For stabilizing the flow in the suction
pipe and for suppressing the torsion guide fins were used, arranged
along the suction pipe. Such guide fins may be oriented in the
axial direction. Thereby the flow torsion in the suction pipe will
be suppressed, but at the same time the efficiency will be
lowered.
[0005] To solve the said problem, variable guide fins are used,
which according to the flow conditions may be moved in and out.
Further, there are used guide fins oriented parallel to the wall
surfaces of the suction pipe in order to stabilize the flow by
avoiding the separation of the flow. However, also structures of
the said type will reduce the efficiency of the turbine. Further,
fixed as well as variable finns will increase the costs of
manufacture and maintenance of the turbine.
[0006] A further approach for the reduction of a torsion of the
flow and its detrimental effect under partial load conditions is to
feed air or water into the non-stable flow. There have become known
structures whereby air is blown into the runner or into the suction
pipe either from the wall of the suction pipe or from the axis of
the runner.
[0007] Further, it has become known to arrange a chamber filled
with water or with air around the suction pipe, which chamber
communicates with the flow in the suction pipe by openings in the
suction pipe wall. Thereby, air respectively water is introduced
respectively removed depending on the pressure conditions in the
suction pipe flow. Here again, the costs of manufacture are
increased by the said pressure chamber as well as by a respective
control unit for the pressure in the chamber.
[0008] It is the objective of the invention to provide a suction
pipe for a Francis turbine which develops advantageous over the
prior art. More in detail, the suction pipe should minimize the
effect of pressure variations such as occur at partial load
conditions. The said objective will be achieved by a suction pipe
according to claim 1.
[0009] The inventors have acknowledged that with a Francis turbine
under partial load conditions there will be created a zone of
recirculation downstreams of the runner. Within the said zone of
transition and the main flow there are heavy gradients of velocity.
Hydrodynamic instabilities of the Kelvin-Helmholtz-type will result
in the formation of vortexes which due to the overall rotation of
the flow comprise a rotative component. A rotating vortex of the
said type will result in a rotating pressure which in the region of
the elbow of the suction pipe generates a force acting in the axial
direction, and further results in pressure variations which also
act in the axial direction and therefore in the direction of the
turbine. It is further possible that such axial pressure variations
in combination with the helically shaped vortex--called
"rope"--will result in boundary layer burbling at the wall of the
elbow, thereby increasing the effect of the axially acting pressure
variations. This explains the generation of pressure variations in
the suction pipe depending on the rotational speed of the
runner.
[0010] A further component of so-called stochastic pressure
variations may be developed by the fact that due to the helical
vortex rope local pressures below the vapour pressure will be
created, thereby leading to cavitation. Additional pressure pulses
will occur upon bursting of the cavitation blisters.
[0011] According to the invention there is arranged in the suction
pipe an elongated displacement body. The upstream end thereof is in
the vicinity of the hub of the runner.
[0012] The displacement body may be rotationally symmetrically, e.
g. cylindrical. Also, it may have the shape of a truncated cone
which tapers in respectively against the direction of flow. It is
arranged such that its outer surface is contacted by flowing water.
In general, its length axis will coincide with the length axis of
the suction pipe.
[0013] Numerous embodiments may be possible. The displacement body
may e. g. be a projection of the hub of the runner and therefore be
part of the hub. Also, it may be located at a minimum distance from
the hub. The said distance may be a few millimeters only, e. g. 1,
2, 3, 5 mm, but also 10 to 50 mm.
[0014] A further embodiment may consist in making the hub longer as
usual, as seen in the direction of flow, e. g. twice or three times
or five times as long as what could be deemed usual, so that the
hub itself would form the displacement body. A further part will
follow, located in the direction of flow. The said further part is
independent of the hub, so that the said further part will not
rotate.
[0015] In such a case, the said further part independent from the
hub has to be fixed inside the suction pipe. Such fixing may be
done by means of rods arranged perpendicularly to the flow
direction at the wall of the suction pipe. The said rods may be
arranged radially.
[0016] A further particularly interesting approach may consist in
journalling the upstream end of the displacement body at the hub of
the runner such that the displacement body will be additionally
stabilized.
[0017] The invention may be used for straight suction pipes as well
as for suction pipes comprising an elbow. With suction pipes with
an elbow there is an additional possibility of support by fixing
the displacement body in the region of the elbow at the suction
pipe respectively at the foundation thereof.
[0018] The invention as well as the prior art will be explained
more in detail by the figures:
[0019] FIG. 1 shows an axially cut Francis turbine.
[0020] FIG. 2 is a numeric flow simulation of the formation of a
vortex.
[0021] FIG. 3 is a suction pipe with a first embodiment of a
displacement body.
[0022] FIG. 4 is a suction pipe with an elbow comprising a second
embodiment of a displacement body.
[0023] FIG. 5 is a straight suction pipe comprising a further
embodiment of a displacement body.
[0024] FIG. 6 is a suction pipe with an elbow comprising a
displacement body similar to those according to FIGS. 3a and
3b.
[0025] FIG. 7 is a suction pipe with an elbow comprising a
displacement body similar to those according to FIGS. 4a and
4b.
[0026] FIG. 8 is a suction pipe with an elbow comprising a
displacement body which is solely fixed at the elbow.
[0027] The Francis turbine according to FIG. 1 comprises a runner 1
with a plurality of runner vanes 1.1. The runner is rotatably
journalled around runner axis 1.2.
[0028] Runner 1 is surrounded by a spiral housing 2. In front of
runner 1 there are provided guide vanes 3.
[0029] The turbine is provided with a suction pipe 4. Suction pipe
4 comprises a frustroconical inlet portion 4.1 having an axis
4.1.1, followed by an elbow 4.2, which again is followed by a
frustroconical outlet portion 4.3.
[0030] Inlet portion 4.1 may be shaped asymmetrical with regard to
runner axis 1.2. Many variations may be possible. Axis 4.1.1 of
inlet portion 4.1 may be offset against runner axis 1.1. Axis 4.1.1
of the inlet portion may be bowed. The wall of inlet portion 4.1
may comprise a bulb at one side thereof, related to the runner axis
1.2. The cross section of inlet portion 4.1 may be different from a
circle, e. g. elliptical.
[0031] The displacement body 5 according to the invention and the
hub of runner 1 may be one single piece, so that displacement body
5 is a projection of the hub in the direction of flow. Therefore,
displacement body 5 rotates together with runner 1.
[0032] FIG. 2 shows a numerical flow simulation of a conventional
Francis turbine at partial load operation, thereby demonstrating
the velocity distribution of the flow in the suction pipe due to
the formation of a helical vortex rope. The vortex rope is
disentangled at the elbow, thereby dissipating energy. With the
said process due to the rotating pressure field of the vortex rope
there will occur pressure variations which will propagate in the
axial direction to the turbine. The said instable flow condition
causes vibrations, depending on the speed of the runner.
[0033] FIGS. 3a and 3b show the inlet portion of a conventional
suction pipe, The said inlet portion is of circular cross section
as may be clearly seen from FIG. 3b. The axis of inlet portion is
straight and coincides with the runner axis.
[0034] The hub 1.3 of runner 1 (not shown) is followed by a
separate displacement body 5. There is a small distance between hub
1.3 and upper end face 5.1 of displacement body 5. Displacement
body 5 is supported by rods 6.1, 6.2, 6.3. The said rods are
fixedly connected to the suction pipe 4.1.
[0035] Displacement body 5 does not rotate together with the runner
1. As may be seen, its cross section is increasing in the direction
of flow.
[0036] In contrast to what is shown in FIGS. 3a and 3b, the
displacement body could be located such that there would be no gap
between hub 1.3 and displacement body 5, so that the upper face 5.1
of displacement body 5 could act as a support for hub 1.3. This
would contribute to the stability and to the secure positioning of
displacement body 5.
[0037] With the embodiment according to FIGS. 4a and 4b the suction
pipe again comprises an elbow. Thereby, the displacement body 5 is
of great axial length. Its upper end is located at the hub of the
runner (not shown) of a turbine, e. g. of a turbine of the Kaplan
type, and extends to the wall of elbow 4.2, where displacement body
5 is fixed. A further fixation may be necessary, either by means of
rods such as rods 6.1, 6.2 and 6.3, or by journalling the
displacement body at the hub of the runner.
[0038] In case displacement body 5 is made of one single piece with
hub 1.3 of runner 1, so that both parts will rotate together at the
same speed, displacement body 5 may be additionally supported at
suction pipe 4. The said rods 6.1, 6.2, 6.3 could journal
displacement body 5 rotatably. The same applies to the embodiment
according to FIGS. 4a and 4b at elbow 4.2.
[0039] The lowermost end of displacement body 5 may have the shape
of a shell. Alternatively, it may be rounded.
* * * * *