"Tunnel transverse thrust apparatus for steering a ship and ship, in particular a cruise ship, with such thrust apparatus"

FIELD OF APPLICATION

[0001] . The present invention relates to a tunnel transverse thrust apparatus for steering a ship and ship, in particular a cruise ship, with such thrust apparatus.

STATE OF THE ART

[0002]. The tunnel transverse thrust apparatus for steering a ship (known in technical jargon as tunnel thrusters) make it possible to · control the ship in confined waters limiting the use of tugs.

[0003] . Such apparatus are normally installed at the bow and/or stern. Each apparatus comprises a tunnel, which crosses the hull transversally, and a propeller thruster installed inside the tunnel. The number, dimensions and power of such apparatus varies in relation to the size of the ship and the performance required of the specific ship by the shipping company.

[0004] . As is known, all thrust apparatus generate high levels of noise and vibrations when functioning. This. may be particularly problematic in cruise ships. Depending on the arrangement of the ship's general layout, the standards of comfort for passenger cabins, crew or public areas may in fact be invalidated. High levels of vibrations may also cause damage to such thrusters..

[0005] . A need is therefore widely felt to eliminate or at least significantly attenuate the creation of noise and vibrations related to functioning of the tunnel thrusters.

PRESENTATION OF THE INVENTION

[0006] . Consequently, the purpose of the present invention is to eliminate or at least attenuate the drawbacks of the prior art mentioned above, by making available a Tunnel transverse thrust apparatus for steering a ship which generates lower levels of noise and vibrations compared to similar traditional apparatus.

[0007] . A further purpose of the present invention is to make available a tunnel thruster for ships which is operatively more reliable.

[0008] . A further purpose of the present invention is to make available a tunnel thruster for ships, which is not considerably more expensive than the traditional apparatus .

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] . The technical characteristics of the invention, according to the aforesaid purposes, can be seen clearly from the contents of the following claims and the advantages of the same will be more clearly compreherisible from the detailed description below, made with reference to the attached drawings, showing one or more embodiments by way of non-limiting examples, wherein:

[0010] . - Figure 1 shows a schematised view of a side of a cruise ship provided at bow and stern with a plurality of tunnel transverse thrust apparatus for steering according to the invention;

[0011] . - Figure 2 shows an enlarged view of a detail of the ship in Figure 1, relative to three thrust apparatus according to the invention, wherein the propellers have not been shown in so as to better illustrate other parts;

[0012] . - Figure 3 is a cross-section view of a thrust apparatus in Figure 2 according to the section plane III- III indicated therein;

[0013] . - Figures 4 and 5 are two cross-section views of the thrust apparatus in Figure 2 respectively according to the section planes IV-IV and V-V indicated therein, where the respective engines have not been shown;

[0014] . - Figure 6 is a schematic cross section view of a detail in Figure 5, relative to a protuberance of the tunnel;

[0015] . - Figure 7 is a schematic cross section view of detail in Figure 2, relative to a protuberance of the tunnel;

[0016] . - figure 8 is a perspective view of the three thrust apparatus in Figure 2, taken on the other side of the ship to that shown in Figure 1;

[0017] . - figure 9 is an enlarged perspective view of one of the three thrust apparatus in Figure 8; and

[0018] . - figures 10 and 11 respectively show the flow lines and velocity fields in a traditional tunnel transverse thrust apparatus for steering and in a thrust apparatus according to one embodiment of the invention.

DETAILED DESCRIPTION

[0019] . With reference to the appended drawings, reference numeral 1 globally denotes a tunnel transverse thrust apparatus for steering a ship according to the invention and reference numeral 100 a ship provided with one or more of such thrust apparatus.

[0020] . Here and henceforth in the description and the claims, reference will be made to the thrust apparatus 1 and to the ship 100 in conditions of use. The references to an upper or lower position or horizontal or vertical direction should therefore be understood in this sense.

[0021] . According to a general embodiment of the invention, the tunnel transverse thrust apparatus for steering 1 comprises:

[0022] . - a tunnel 10, which extends in a longitudinal direction X between a first 11 and a second aperture 12 and is destined to fully cross the hull from one side to the other of the ship;

[0023] . - a thruster 20 having a propeller 21 positioned inside the tunnel 10 between the aforesaid two apertures 11, 12.

[0024]. As shown in particular in Figure 3,4 and 5, the thruster 20 comprises a gear body 22 which supports the propeller 21 at one of its ends 22'.

[0025] . The propeller faces onto a first aperture 11 of the tunnel, while the gear body 22 faces onto the second aperture of the tunnel, opposite the first aperture 11, with its second end 22".

[0026] . Advantageously, the tunnel 10 consists of a tubular body 13, preferably made from sheet metal.

[0027] . According to a preferred embodiment solution, shown in the appended drawings, the tunnel has a circular- shape transversal cross-section (orthogonal to ^' the direction of longitudinal extension X) .

[0028] . Preferably, the longitudinal extension axis X of the tubular body is straight. Alternative solutions may be envisaged however (not shown in the appended Figures) in which such extension axis is not straight but is, for example, curved.

[0029] . In particular according to a preferred embodiment, shown in the appended drawings, the tubular body 13 comprises a main body 14 (of a tubular shape) , inside which the propeller 21 and the gear body 22 are positioned, and at each of the two apertures 11 and 12, a portion of outer rim 15, which defines a radially divergent surface from the main body. Such portion of outer rim 15 is suitable for connecting the main body to the hull of the ship. In particular such rim portion 15 is a semi-conical shape.

[0030] . According to a preferred embodiment solution, the thruster 20 comprises a motor 25 (preferably electric) which is positioned externally to the tunnel, inside the hull of the ship. The motor 25 is mechanically connected to the gear body by transmission means 26 (shown schematically in figure 3) which enter the tunnel inside a containment body 27· which preferably extends in a diametrical direction of the tunnel and is connected in turn to said gear body.

[0031] . Preferably, the gear body 22 is connected to the walls of the tunnel 10 by at least two support wings 23 and 24, which extend radially from the gear body as far as the tunnel walls in the lower area of the tunnel. In particular the two wings are positioned symmetrically to a vertical diametrical plane of the tunnel, at an angular distance from each other which in a preferred example is approximately 120°.

[0032] . According to the present invention, the tunnel 10 has a protuberance 30 on one its inner walls next to the second aperture 12, which protuberance extends along at least a perimetral section of the tunnel 10. Transversal cross-section is taken to mean a cross-section orthogonal to the direction of longitudinal extension X of the tunnel.

[0033] . From a functional point of view, such protuberance 30 creates an accelerated flow area next to the second aperture 12 when the propeller 21 generates an incoming flow in the tunnel through the second aperture 12.

[0034] . Detailed studies conducted by the Applicant on different ship constructions have, in fact, shown that the high levels of noise and vibrations generated by the traditional tunnel thrusters are characteristic of a cavitating propeller.

[0035] . The main source of cavitation proved to be the non-uniformity of the flow of water striking the functioning thruster. In particular separations of flow from the walls of the tunnel next to the second aperture 12 and a consequent extremely poor operating condition of the thruster propeller occur when the propeller 21 generates an incoming flow in the tunnel through the second aperture 12 (i.e. the aperture opposite the one which the propeller faces onto) . [0036] . The accelerated flow area generated by the protuberance 30 makes it possible to minimise the separation of the confined flow entering the tunnel at the second aperture 12. This makes it possible to improve the operating condition of the propeller and thereby reduce the creation of vibrations and noise during the functioning of the thrust apparatus 1.

[0037 ] . Preferably, the aforesaid protuberance 30 is positioned in the lower area of the tunnel. "Lower area" is taken to mean the area of the tunnel which with the thrust apparatus installed onboard is closest -to the baseline 2 of the ship, that is, closest to the keel of such ship.

[0038] . The studies conducted have, in fact, pointed out that it is precisely at the lower area of the tunnel that a severe separation of flow and consequent very poor operating condition of the thruster propeller occurs. It therefore proves particularly advantageous to position the aforesaid protuberance 30 in the lower area of the tunnel to create an accelerated flow area precisely in that part of the tunnel.

[0039] . Preferably, as shown in particular in Figures 5 and 6, the protuberance 30 has a cross-section with a bevelled or rounded outer profile in relation to the longitudinal extension direction X of the tunnel. In particular such outer profile is curved (for example, defined by a circular arc or by an elliptical arc) .

[0040] . · As shown in the appended drawings and in particular in Figure 9, the protuberance is elongated in a transversal . direction to the longitudinal extension direction X of the tunnel. The protuberance _, thus forms a hump next ^' to the second aperture 12 entering the tunnel 12.

[0041] . Preferably, as shown in particular in Figure 2, the protuberance 30 is positioned symmetrically to a diametrical vertical plane V of the tunnel.

[0042] . Preferably, the protuberance 30 extends along a circular arc (or elliptical arc) having an extension of 120° to 180°. Solutions may however be envisaged wherein the protuberance extends along a circular arc of less than 120° or more than 180°. Solutions may also be envisaged wherein the protuberance covers the entire perimetral extension of the tunnel, extending for 360°.

[0043] . Advantageously, as shown in particular in Figure 2, in the case in which the gear body is connected to the tunnel by the aforementioned support wings 23 and 24, the protuberance 30 extends in a transversal direction between such two wings.

[0044] . Preferably, as shown in Figures 3, 4, 5 and 9, when the tunnel 10 is provided with a portion of external rim 14 defining a radially divergent surface, the protuberance 30 is positioned on the main body 14 of the tunnel next to such portion of outer rim 15.

[0045] . Preferably, the protuberance 30 consists of a solid sheet metal shaped so as to have a conformation corresponding to the wall of the tunnel. In particular with a tunnel having a circular cross-section, the sheet metal (already shaped to have a bevelled or rounded transversal cross-section) is calendered so as to be easily welded onto the tunnel. Installation takes place in dry dock by performing full penetration welding 31 all around the perimeter of the element (as shown in Figures 6 and 7 ) .

[0046] . This construction method is entirely preferred in that it makes it easy to fit the protuberance onto existing ships too, as part of retrofitting operations. Alternative construction methods may however also be envisaged, such as the shaping of the protuberance directly on the tubular body of the tunnel, for example by embossing.

[0047] . The protuberance (when consisting of an element applied to the tunnel) is preferably made from metal, but may also be made from plastic material.

[0048] . Preferably, in the case of a tunnel with a circular cross-section of 1.8 to 3.5m and a propeller thruster of a power of 800 to 3500Kw, with reference to a transversal cross-section (as shown in Figure 6) the protuberance 30 has a maximum height H of 30 to 60mm, a width L of 150 to 300 mm and a curvature radius R of 200 to 270 mm. In the particular case of a tunnel with a diameter of approximately 2.45 m, the protuberance has a maximum height H of 50mm, a width L of 270mm and a curvature radius ^* R of 250mm. The protuberance has a transversal extension of about 120°.

[0049] . The above stated in relation to the advantageous fluidodynamic effects given by the protuberance 30 is confirmed by computerised fluid dynamic simulations on different types of tunnel thruster.

[0050] . Figures 10 and 11 show the results of such fluid dynamic simulations performed for a tunnel thruster, with a tunnel having a circular cross-section of 2.457 m in diameter (as illustrated in Figure 4, shown in scale). The protuberance is positioned in the lower area of the tunnel and has a maximum height H of 50mm, a width L of 270mm and a curvature radius R of 250mm; the transversal extension is about 120°. The thruster has a nominal power of 1720 kW. The simulations were performed with reference to prevalent operating conditions, that is to say maximum power of the thruster engine, absence of speed of advancement of the ship and minimum transversal drift speed, normally 0.25 m/s.. An incoming flow through the second aperture 12 was considered.

[0051] . In particular figure 10 shows the flow lines and velocity fields in a traditional tunnel transverse thrust apparatus for steering, while Figure 11 shows the flow lines 'and velocity fields in a tunnel transverse thrust apparatus for steering according to a preferred embodiment of the invention (identical to the traditional except for the presence of the protuberance 30) .

[0052] . More specifically, in Figure 10 one may observe how in the lower area of the tunnel at the second aperture 12 a flow separation area is present, while in Figure 11 one may observe how in the lower area of the tunnel at the second aperture 12, where the protuberance 30 according to the present invention is positioned, an accelerated flow area is present and the separation phenomenon of the confined flow is greatly attenuated.

[0053] . The present invention also relates to a ship, in particular a cruise ship, which comprises one or more tunnel transverse thrust apparatus for steering 1 according to the invention. Preferably, the thrusters 1 are positioned at bow and/or stern, as shown for example in Figure 1.

[0054] . The invention makes it possible to achieve numerous advantages, some of which already described above .

[ 0055] . The tunnel transverse thrust apparatus for steering 1 according to the invention generates lower levels of noise and vibrations compared to similar traditional thrusters, due to the improvement of the characteristics of the flow to the propeller given by the presence of the protuberance next to the second aperture of the tunnel.

[0056] . The tunnel thrust apparatus according to the invention is operatively more reliable, inasmuch as less subject to damage over time related to vibration phenomena .

[0057] . The tunnel thrust apparatus according to the invention has a cost entirely comparable to traditional apparatus. The protuberance may, in fact, be made from a shaped metal sheet, easily applicable in dry dock by welding. The invention may also advantageously be applied to existing thrust apparatus, as part of retrofitting operations .

[0058] . The invention thus conceived thereby achieves the intended objectives.

[0059] . Obviously, its practical embodiments may assume forms and configurations different from those described while remaining within the sphere of protection of the invention. [0060] . Furthermore, all the parts may be replaced with technically equivalent parts and the dimensions, shapes and materials used may be varied as required.