CN110023187B

CN110023187B - Flow guide pipe of ship propeller

Info

Publication number: CN110023187B
Application number: CN201680091203.3A
Authority: CN
Inventors: 克劳斯·特威德尔; 迪特里赫·本克
Original assignee: Schottel GmbH
Current assignee: Schottel GmbH
Priority date: 2016-11-28
Filing date: 2016-11-28
Publication date: 2021-06-15
Anticipated expiration: 2036-11-28
Also published as: BR112019006498A2; CN110023187A; CA3041179A1; WO2018095548A1; RU2722082C1; BR112019006498B1; EP3544887A1; EP3544887B1; CA3041179C

Abstract

The invention relates to a draft tube (1) for a marine thruster (19) which is rotatable about an axis of rotation (A), having a draft tube housing (10) which extends along the axis of rotation (A) and surrounds the marine thruster (19), which has inner and outer surfaces (11, 12) which together form a streamline, and which has at least one sacrificial anode (2) which is arranged on the outer surface (12) of the draft tube housing (10), wherein the outer surface (12) of the draft tube housing (10) has at least one receptacle (13) which is recessed with respect to the streamline, and the at least one sacrificial anode (2) is designed such that it can be inserted into the receptacle (13) in such a way that it substantially fills the receptacle (13).

Description

Flow guide pipe of ship propeller

Technical Field

The invention relates to a draft tube for a marine propeller which is rotatable about an axis of rotation, said draft tube having a draft tube housing which extends along said axis of rotation and surrounds said marine propeller, said draft tube housing having an inner surface and an outer surface which together form a streamline, and said draft tube having at least one sacrificial anode arranged on said outer surface of said draft tube housing.

Background

Draft tubes have long been arranged as enclosures around ship propellers, also known as kort draft tubes. The nozzle shroud has a wing-like streamline shape for reducing flow losses at the tip of the propeller blades and producing higher mass flow. This improves the efficiency of the marine propulsion system. However, as with the marine propulsor itself, the nozzle shrouds are typically made of metal and must be protected from electrolytic corrosion. In addition to this, particularly when marine propellers are used in seawater, the conductivity of seawater is high and it is suitable for use as an electrolyte and galvanic element, thus presenting the risk of severe electrolytic corrosion, with consequent premature wear of the components of the propulsion system of the marine propeller and of the related draft tubes.

Therefore, for the purpose of corrosion protection, a number of sacrificial anodes protruding from the outer surface of the nozzle boot are typically attached. However, these sacrificial anodes act as obstacles in the flow along the outer surface, increasing the resistance of the flow conduit during operation. This results in a reduction in the propulsion of the draft tube and thus in a reduction in the overall efficiency of the marine vessel propeller.

Disclosure of Invention

The invention aims to provide a draft tube of a ship propeller, which can overcome the defects in the prior art, is simple and convenient to manufacture, and is easy to replace after an anode is sacrificed to be worn.

The solution of the invention to achieve the above object is a flow guide tube according to the features of claim 1.

Advantageous embodiments and improvements of the flow guide tube according to the invention are subject matter of the dependent claims.

In order to achieve the object, the invention proposes that the outer surface of the nozzle dome has at least one receptacle which is recessed with respect to the streamline and that the at least one sacrificial anode is designed in such a way that it can be inserted into the receptacle in such a way that it substantially fills the receptacle. In this way, a sufficient number or a sufficient volume of sacrificial anodes can be arranged in the region of the outer surface of the flow guide sleeve, which sacrificial anodes do not protrude or at most slightly protrude beyond the streamline as a result of being arranged in the recessed receptacles. The at least one sacrificial anode is not subject to any further restrictions and therefore the at least one sacrificial anode may be an anode of almost any profile, in particular of standard configuration, as long as they are able to substantially fill the recessed receptacles. A receptacle substantially filling a recess refers to a space within the receptacle region of a recess, wherein the received anode does not protrude or protrudes only slightly beyond the adjacent streamline.

The invention proposes that the at least one sacrificial anode is designed such that it, after insertion into the receptacle, smoothly continues the streamlined contour of the flow duct according to the invention adjacent to the receptacle and, due to its design corresponding to the streamline, forms itself as a part of the streamline. In this way, the invention makes it possible to minimize the disturbance of the flow around the nozzle housing caused by the sacrificial anode and to avoid the influence of the thrust of the nozzle during operation despite the sacrificial anode.

The arrangement and positioning of the receptacles and the sacrificial anodes positioned therein is in principle not subject to any restrictions and can be selected accordingly by the person skilled in the art depending on the actual conditions of the flow conduit. The receptacles and the sacrificial anodes positioned therein can be arranged either all the way around the circumference of the draft tube or only in segments, for example, around a 180 ° circumferential section of the draft tube housing.

The invention proposes that the receptacle is constructed in a rear region, viewed in the flow direction of the fluid through the draft tube, preferably close to the outflow opening of the draft tube housing behind the ship propeller.

The invention proposes that the receptacle can be designed as an annularly encircling step in the outer surface of the flow tube housing and that a plurality of sacrificial anodes are embedded annularly around the step, so that the desired step volume proportion can be filled by the sacrificial anodes and the streamline of the flow tube housing is smoothly continued by the sacrificial anodes bridging the step. In this case, it is not necessary to completely fill the total volume fraction of the terraces with sacrificial anodes, but such complete filling is extremely effective in terms of flow technology. However, it is also possible to fill the receptacle only partially with the anode, which, surprisingly, is not accompanied by a significant loss in efficiency. It is only important that the anode is located in the receptacle without filling up with significant resistance along the flow line.

Alternatively, a plurality of discrete receptacles can also be provided, introduced into the outer surface in the form of rings, in each of which a corresponding sacrificial anode is embedded. In this embodiment, a web remains between the adjacent sacrificial anode and the associated receptacle, which extends in the region of the outer surface along a streamline and reinforces the outer surface of the flow tube housing in the manner of a reinforcing rib.

The invention further proposes that the at least one sacrificial anode is removably inserted into the receptacle, for example removably fixed thereto, suitably by means of screws. This not only simplifies assembly, but the sacrificial anode can be easily replaced with a new sacrificial anode after wear.

For the functionality of the sacrificial anode, it is necessary to electrically conductively connect the sacrificial anode to the component to be protected, in particular the nozzle dome. To this end, the invention proposes that at least one sacrificial anode has an electrically conductive carrier plate with protruding fastening tabs for fastening to the flow guide sleeve. The sacrificial anode may for example be cast from a suitable metal, wherein the carrier sheet may be cast into the sacrificial anode directly during its manufacture, which enables a reasonable manufacture and good electrical connection.

For example, the at least one sacrificial anode may be made on the basis of zinc, magnesium or aluminium or a combination of the above, while the carrier sheet may be made of, for example, commercial structural steel or other suitable electrically conductive material.

The invention further provides that the at least one sacrificial anode is fastened in the receptacle in such a way that a gap remains between the sacrificial anode and the flow tube housing. By means of this gap, a favorable circulation around the sacrificial anode can also be achieved at the bottom surface of the sacrificial anode by achieving recirculation, with a concomitant cleaning action of the sacrificial anode surface. In order to further enhance this effect, the gap may be gradually widened toward the inflow opening of the draft tube.

The draft tube of the present invention can be used in both conventional propeller systems with fixed vessel propellers in various marine vessels, and in rudder propellers supported for rotation about their vertical axis and capable of directly controlling the vessels so driven, including various water jet propulsion devices, such as the "linear jet" developed by Voith corporation.

Drawings

Further aspects and details of the invention are explained below with reference to the drawings showing an embodiment. In the figure:

figure 1 is a perspective view of a rudder propeller having a draft tube according to the present invention,

figure 2 is a detail view of the draft tube shown in figure 1,

fig. 3 is an enlarged cross-sectional view of the draft tube shown in fig. 2.

Detailed Description

Fig. 1 shows a perspective view of a known rudder propeller comprising a ship propeller 19 which can be rotated about an axis of rotation a by means of a drive (not shown). The rudder propeller is rotatable about its vertical axis H in order to control a water-craft equipped with such a rudder propeller.

The propeller blades 190 of the marine propeller 19 are surrounded by a draft tube 1 which extends along the axis of rotation a and has a draft tube shroud 10 which tapers in the flow direction S through the draft tube 1, with an inflow opening 100 and an outflow opening 101 for the fluid (i.e. water) accelerated by the marine propeller 19.

As shown in the cross-sectional view with reference to fig. 3, the nozzle boot 10 surrounding the marine propeller 19 has an inner surface 11 and an outer surface 12 which together form a streamline shape like a wing. The water flowing in the flow direction S is in turn divided into partial flows S1 inside the flow conduit 1 and partial flows S2 outside the flow conduit 1, wherein the boundary layer to the flow conduit 1 is guided along the inner surface 11 and the outer surface. The streamlining is designed to be as smooth as possible to avoid flow losses along the inner and

outer surfaces

11, 12.

Adjacent to the outflow opening 101, in the region of the outer surface 12 of the nozzle hood 10, a receptacle 13 in the form of an annularly encircling step is extended which is recessed along the outer surface 12 with respect to the streamline. This accommodation 13 formed by terraces is occupied by a plurality of sacrificial anodes 2, which are built in correspondence with the accommodation 13 and substantially fill the accommodation 13, which are shaped such that they not only substantially fill the accommodation 13 but also continue smoothly streamlined along the outer surface 12. In this way, the streamlining obtained along the outer surface 12 minimizes the impact to which the sacrificial anode 2 is exposed despite its placement. In view of this, the sacrificial anode 2 is part of a streamlined shape in the region of the outer surface 12 of the nozzle boot 10.

The sacrificial anode 2 itself may be used in a number that is set to a volume or mass that is calculated to be sufficient to prevent corrosion of the propulsion system including the marine propulsor 19 and the draft tube 1.

The individual sacrificial anodes 2 are connected to the nozzle housing 10 by means of fastening tabs 21 projecting from the nozzle housing 10, for example by means of screwing or welding, so that they can be easily assembled and replaced after wear. For example, as shown, each sacrificial anode 2 may be fastened on both sides to the housing 13 by means of two respective fastening tabs 21 and associated screws positioned at an angle of 90 °.

Besides, by fastening the tabs 21, each sacrificial anode 2 is arranged with a clearance from the manifold housing 10, whereby a recirculation of running water is achieved, which not only enhances the rinsing effect of the surface of the sacrificial anode 2, but also increases the cleaning action of the surface of the sacrificial anode 2. To increase this effect, the gap between the sacrificial anode 2 and the nozzle hood 10 can be optimized with regard to its gap width, in that it is configured to widen gradually towards the inflow opening 100 of the nozzle 1.

The sacrificial anode 2 is made of a suitable metal, such as zinc, magnesium or aluminium or a combination of the above, in a casting process, wherein during casting an electrically conductive carrier sheet 20 is cast into the body of the sacrificial anode 2 and integrally connected thereto. It goes without saying that the shape of the sacrificial anode is arbitrary and depends on the streamlined corresponding contour of the nozzle dome 10 and the installation position in the nozzle dome 10. Standard anodes sized to fit into the receptacle 13 may also be used.

The sacrificial anode 2 can also be arranged at a position closer to the direction of the inflow port 100. Furthermore, it is possible, if necessary, to close the gap between adjacent sacrificial anodes 2 with a coating, depending on the desired streamlining, or to provide a plurality of discrete recessed receptacles 13 into which the sacrificial anodes 2 are respectively filled and into which they are embedded in a manner that continues the streamlining substantially smoothly. The receiving areas 13 are then similar to receiving bags and are each delimited from the adjacent receiving area 13 by a web of the nozzle hood 10, as a result of which greater stability can be achieved.

It is also conceivable in principle to attach the sacrificial anode in the region of the inner surface, but when the loss of the sacrificial anode 2 causes a change in the streamlining, it is expected that more disturbances will occur caused by the propeller blades accelerating the flow along the inner surface, which will have a negative effect on the ship's propeller 19.

The draft tube of the present invention is suitable for both newly constructed ship drives and for retrofitting and replacing existing draft tubes on existing ship propellers.

Claims

1. A draft tube (1) for a marine thruster (19) rotatable about an axis of rotation (A), which draft tube has a draft tube shield (10) which extends along the axis of rotation (A) and surrounds the marine thruster (19), which draft tube shield has inner and outer surfaces (11, 12) which together form a streamline, and which draft tube has a plurality of sacrificial anodes (2) which are arranged on the outer surface (12) of the draft tube shield (10), characterized in that, in a rear region (101) as viewed in an overflow direction (S) of the draft tube (1), the outer surface (12) of the draft tube shield (10) has at least one accommodation site (13) which is recessed with respect to the streamline, which accommodation site (13) is constructed as an annularly encircling terrace in the outer surface (12) of the draft tube shield (10), and a plurality of correspondingly constructed sacrificial anodes (2) are embedded in the step in an annularly encircling manner in such a way that the receptacles (13) are filled.

2. The flow duct according to claim 1, characterized in that the sacrificial anode (2) is correspondingly constructed in such a way that it can be inserted into the receptacle (13) in a smoothly continuous fashion.

3. The flow duct of claim 1, characterized in that a plurality of discrete housing portions (13) are provided, introduced into the outer surface (12) in the form of a ring, each housing portion having embedded therein a corresponding sacrificial anode (2).

4. The flow duct of claim 1, characterized in that the sacrificial anode (2) is removably embedded in the housing (13).

5. The flow duct of claim 1, characterized in that the sacrificial anode (2) has an electrically conductive carrier sheet (20) with protruding fastening tabs (21) for fastening to the flow duct cover (10).

6. The flow duct of claim 1, characterized in that the sacrificial anode (2) forms the streamlined section.

7. The draft tube of claim 1, wherein the sacrificial anode (2) is made based on zinc, magnesium or aluminum or a combination thereof.

8. The flow guide tube of claim 1, characterized in that the sacrificial anode (2) is arranged in the accommodation (13) with a gap to the flow guide tube housing (10).

9. The draft tube of claim 1, characterized in that the marine propeller (19) is constructed as a rudder propeller.