Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 03041179 2019-04-18
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Nozzle of a Ship Propeller
Description:
The invention relates to a nozzle of a ship propeller that can rotate about an
axis of rotation, comprising a nozzle casing extending along the axis of
rotation
and surrounding the ship propeller, and having inner and outer surfaces, which
together form a flow profile, and having at least one sacrificial anode
arranged
on the outer surface of the nozzle casing.
Arrangement of a nozzle as a casing around a ship propeller has been known
for many years, and is also known as a Kort nozzle. The nozzle casing
comprises a flow profile similar to a wing, and serves to reduce losses of
flow
on the ends of the propeller blades, and to generate a higher mass flow. This
leads to an increase of the efficiency of such a ship propeller. But like the
ship
propeller itself, the nozzle casing is usually made of metal, and must be
protected against electrolytic corrosion, In particular, when using the ship
propeller in seawater, there is otherwise, due to high conductivity of the
seawater and its suitability as an electrolyte and galvanic element, the risk
of a
heavy electrolytic corrosion and premature wear and tear as a result, of
component parts of the propulsion system comprising the ship propeller
including the associated nozzle.
Therefore it is usual for the purpose of corrosion protection to attach a
determined number of sacrificial anodes projecting from the outer surface of
the
nozzle casing. But the sacrificial anodes are interference members in the
fluid
flow occurring along the outer surface increasing the nozzle resistance during
travel. As a consequence, nozzle thrust decreases and thus the ship propeller
as a whole becomes less efficient.
It is the objective of the invention to suggest a nozzle of a ship propeller,
which
overcomes the disadvantages of the State of the Art, is easy to manufacture,
and for which a replacement of the sacrificial anodes after their consumption
is
easy to handle.
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Said objective is achieved in accordance with the invention with a nozzle
according to the features of the present disclosure.
Advantageous embodiments and developments of the nozzle according to the
invention are the subject matter of the present disclosure.
For achieving the objective, it is suggested that the outer surface of the
nozzle
casing has at least one recess that is deepened in relation to the flow
profile,
and the at least one sacrificial anode is designed correspondingly to the
recess
so that it can be introduced into the recess such that it substantially fills
the
recess. In this manner it is possible to arrange a sufficient number and/or a
sufficient volume of sacrificial anodes in the area of the outer surface of
the
nozzle casing which due to their arrangement in the deepened recess do not
project from the flow profile or at most slightly project from the flow
profile. The
at least one sacrificial anode is not subject to any further restrictions,
therefore
they can be anodes of almost any contour, in particular also standard designs
as long as they substantially fill the deepened recess. By "substantially fill
the
deepened recess" is meant a filling of the space in the area of the deepened
recess, wherein the received anode does not or only slightly project from the
adjacent flow profile.
According to one suggestion of the invention, the at least one sacrificial
anode
is configured such that after introduction into the recess it smoothly
continues
the contour of the flow profile of the inventive nozzle adjacent to the
recess, and
thus, due to a design corresponding to the flow profile, forms part of the
flow
profile itself. According to the invention, interference of the fluid flow
around the
nozzle casing due to the sacrificial anodes is reduced according to the
invention
to a minimum in this way, and nozzle thrust during travel is not impaired
despite
the existence of the sacrificial anodes.
In principle, there is no restriction regarding the arrangement and
positioning of
the recess and the sacrificial anodes positioned therein, and it can be
selected
by the person skilled in the art depending on the conditions on the nozzle.
Not
Date Recue/Date Received 2022-07-14
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only an arrangement of the recess, extending entirely around the nozzle
circumference, and the sacrificial anodes positioned in the recess but also an
arrangement only in partial segments, for example, a circumferential section
of
1800 around the outer nozzle casing, can be provided.
According to a suggestion of the invention, the recess is formed in the nozzle
back area seen in flow direction of the fluid through the nozzle, preferably
close
to the outlet opening of the nozzle casing behind the ship propeller.
According to a suggestion of the invention, the recess can be formed as an
annularly extending stepped shoulder in the outer surface of the nozzle
casing,
and a plurality of sacrificial anodes is introduced into the stepped shoulder
in an
annularly extending manner so that a requested volume fraction of the stepped
shoulder is filled by the sacrificial anodes, and the flow profile of the
nozzle
casing is smoothly continued by bridging the stepped shoulder. Here, it is not
necessary to fill the entire volume fraction of the stepped shoulder with
sacrificial anodes, although such an entire filling is particularly efficient
in terms
of flow. But it can also be provided to fill the recess only partly with
anodes
which is surprisingly without considerable loss of efficiency. It is only
essential
that the anodes within the recess can be overflown along the flow profile
without
considerable resistance.
Alternatively, it can also be provided that a plurality of discrete recesses
introduced annularly into the outer surface is provided into which one
corresponding sacrificial anode each is introduced. Between adjacent
sacrificial
anodes and associated recesses, webs are maintained in this embodiment
extending along the flow profile in the area of the outer surface and
stiffening
the outer surface of the nozzle casing in the manner of reinforcing ribs.
According to another suggestion of the invention it is provided that the at
least
one sacrificial anode is releasably introduced into the recess, for example,
is
fixed in the same in an appropriate manner by means of screws. By this, not
only assembly is simplified but the sacrificial anode after its consumption
can be
easily replaced by a new sacrificial anode.
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For functioning of the sacrificial anode it is necessary that it is connected
with
the component parts to be protected, in particular the nozzle casing, in an
electrically conductive manner. For this purpose, it is suggested according to
the invention that the at least one sacrificial anode comprises an
electrically
conductive support plate with protruding fastening straps for fastening on the
nozzle casing. For example, the sacrificial anodes can be cast from a suitable
metal, wherein the support plate can be directly included in the casting when
manufacturing the sacrificial anodes, permitting an efficient production and a
good electrical connection.
For example, the at least one sacrificial anode can be produced based on zinc,
magnesium or aluminium or combinations thereof, whereas the support plate,
for example, can be produced from a commercial steel or any other suitable,
electrically conductive material.
According to another suggestion of the invention, the at least one sacrificial
anode is fixed in the recess such that a gap remains between the sacrificial
anode and the nozzle casing. Through said gap, an advantageous flow around
the sacrificial anode also on its underside by a recirculation, which
develops,
can be achieved which is also accompanied by a cleaning effect for the surface
of the sacrificial anode. For further increase of said effect, the gap can be
formed in such a way that it becomes larger in the direction of the inlet
opening
of the nozzle.
According to another aspect of the invention, there is provided a ship
propeller
having a nozzle, rotatable about an axis of rotation comprising a nozzle
casing
extending along the axis of rotation and surrounding the ship propeller, and
having inner and outer surfaces, which together form a flow profile, and
Date Recue/Date Received 2022-07-14
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having at least one sacrificial anode arranged on the outer surface of the
nozzle
casing, wherein the outer surface of the nozzle casing has at least one recess
that is deepened in relation to the flow profile, the at least one recess is
formed
in a downstream area of the nozzle seen in a flow direction of the nozzle, and
the at least one sacrificial anode is correspondingly configured to be
introduced
into the at least one recess so that it substantially fills the at least one
recess.
The nozzle according to the invention can be used not only in conventional
propeller systems with fixed ship propellers for watercrafts of any type but
also
in rudder propellers, wherein the ship propeller is rotatably mounted around
its
vertical axis, and directly permits control of a ship propelled in such a
manner,
including different types of water jet propulsion, for example, the linear jet
developed by the Voith company.
Further embodiments and details of the invention will be explained below by
means of the drawing representing an embodiment.
Date Recue/Date Received 2022-07-14
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Figure 1 shows in perspective view a rudder propeller with a nozzle
according to the invention,
Figure 2 shows the nozzle according to Figure 1 with representation of
individual components,
Figure 3 shows a section through the nozzle according to Figure 2 in an
enlarged scale.
Figure 1 shows in perspective view a rudder propeller known per se which
comprises a ship propeller 19 rotatable about an axis of rotation A by means
of a
propulsion not shown. For the purpose of control of a watercraft, which is
equipped by it, the rudder propeller is rotatable about its vertical axis H.
The propeller blades 190 of the ship propeller 19 are surrounded by a nozzle 1
extending along the axis of rotation A and comprising a nozzle casing 10,
conically tapering in flow direction S through the nozzle 1, with inlet
opening 100
and outlet opening 101 for the fluid accelerated by the ship propeller 19,
i.e.
water.
As can be seen from the sectional view according to Figure 3, the nozzle
casing
10 surrounding the ship propeller 19, comprises an inner surface 11 and an
outer surface 12 which together form a flow profile similar to a wing. The
water
flowing in in flow direction S divides into a partial flow S1 within the
nozzle 10
and a partial flow S2 outside the nozzle 10, wherein the boundary layers to
the
nozzle 10 are lead along the inner surface 11 and/or the outer surface. The
flow
profile is formed as smooth as possible along the nozzle inner and outer
surface
10, 11 in order to avoid flow losses.
Adjacent to the outlet opening 101, a recess 13, deepened in relation to the
flow
profile along the outer surface 12, in the form of an annularly extending
stepped
shoulder is formed in the area of the outer surface 12 of the nozzle casing
10.
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Said recess 13 formed by the stepped shoulder is occupied by a plurality of
sacrificial anodes 2 designed correspondingly to the recess 13 and
substantially
filling the recess 13 which sacrificial anodes 2 are formed such that they do
not
only substantially fill the recess 13 but also smoothly continue the flow
profile
along the outer surface 12. In this way, a flow profile along the outer
surface 12
is maintained which despite arrangement of the sacrificial anodes 2 is only
minimally impaired. Hence, the sacrificial anodes 2 are part of the flow
profile in
the area of the outer surface 12 of the nozzle casing 10.
The sacrificial anodes 2 themselves exist in such a number that there is a
volume and/or mass which for corrosion protection of the propulsion system
comprising the ship propeller 19 including the nozzle 1 has been calculated as
being sufficient.
The individual sacrificial anodes 2 are connected with the nozzle casing 10 by
means of fastening straps 21 protruding from the nozzle casing 10, for
example,
by means of a screw or weld connection, and therefore can be easily mounted
and replaced after consumption. As is shown, each sacrificial anode 2 can, for
example, be fastened on the recess 13 on both sides each via two fastening
straps 21 positioned at an angle of 90 , and associated screws.
Moreover, each sacrificial anode 2 can be arranged via the fastening straps 21
by leaving a gap to the nozzle casing 10 through which recirculation of the
flowing water occurs which does not only increase flushing of the surface of
the
sacrificial anode 2 but also exercises a cleaning effect on the surface of the
sacrificial anode 2. In order to increase said effect, the gap between the
sacrificial anode 2 and the nozzle casing 10 can be optimised regarding its
gap
width by increasing the same towards the inlet opening 100 of the nozzle 1.
The sacrificial anodes 2 are manufactured from a suitable metal, for example,
zinc, magnesium or aluminium or combinations thereof, in a casting process,
wherein during casting an electrically conductive support plate 20 is cast
into
the body of the sacrificial anodes 2, and thus integrally connected with the
sacrificial anodes 2. It is understood that the sacrificial anodes can be of
any
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shape and that it depends on the respective contour of the flow profile of the
nozzle casing 10 and the installation position in the nozzle casing 10. Also,
standard anodes in a size matching the recess 13 can be used.
It is also possible to arrange the sacrificial anodes 2 in a position further
in the
direction of the inlet opening 100. Moreover, if necessary, the clearances
between adjacent sacrificial anodes 2 can be closed with covers in accordance
with the desired flow profile or a plurality of discrete deepened recesses 13
are
provided into which one sacrificial anode 2 each is introduced to fill the
recess
and substantially continue the flow profile smoothly. The recesses 13 are then
similar to recess pockets and are delimited to adjacent recesses 13 each by
webs of the nozzle casing 10, whereby a higher stability can be achieved.
Generally it would also be imaginable to attach the sacrificial anodes in the
area
of the inner surface but in that case a major interference of the fluid flow
accelerated by the propeller blades along the inner surface has to be
expected,
and moreover modifications of the flow profile occur during consumption of the
sacrificial anodes 2 which have an adverse effect on efficiency of the ship
propeller 19.
The nozzle according to the invention explained above is suitable not only for
new manufacture of a ship propulsion system but also for retrofit of already
existing ship propellers, and replacement of existing nozzles on such a ship
propeller.
