FI20225121A1

FI20225121A1 - A flow guide arrangement of a rectracable thruster, a rectracable thruster, and a system

Info

Publication number: FI20225121A1
Application number: FI20225121A
Authority: FI
Inventors: Henri Moilanen
Original assignee: Kongsberg Maritime Finland Oy
Priority date: 2022-02-11
Filing date: 2022-02-11
Publication date: 2023-08-12
Also published as: EP4227210A1

Abstract

A flow guide arrangement of a retractable thruster unit (1), the retractable thruster unit comprising a thruster housing (2) and a stem (3) for connecting the thruster housing (2) to a support and lifting structure, wherein the thruster housing (2) is arranged rotatable around an axis (V) of the stem (3), a propeller (4) arranged rotatable relative to a longitudinal axis (L) of the thruster housing (2), and a drive means for rotating the propeller. The flow guide (10) is arranged on the periphery of the thruster housing (2) on a side opposite to the propeller (4).

Description

A FLOW GUIDE ARRANGEMENT OF A RECTRACABLE THRUSTER, A

RECTRACABLE THRUSTER, AND A SYSTEM

FIELD OF THE INVENTION

The invention relates to a flow guide ar- rangement of a retractable thruster of a marine ves- sel.

The invention relates also to a retractable thruster unit of a marine vessel.

The invention relates also to a system.

BACKGROUND OF THE INVENTION

Marine vessels use various propulsion systems or units. The main propulsion system unit or units is/are normally arranged in the aft part of the ship.

The main propulsion system may be either a fixed pro- peller arrangement creating a thrust force in the lon- gitudinal direction of the marine vessel, or it may be a pod or thruster, i.e. a propeller arrangement that may be rotated round a vertical axis.

The marine vessels have also other propulsion arrangements that are mainly used when manoeuvring a ship in a port, for instance. One type of such propul- sion arrangements is a tunnel thruster, which may be used both at the bow or at the stern of a ship. The

N tunnel thruster may be arranged in a horizontal tunnel

N running transverse to the longitudinal direction of

S the marine vessel through the hull of the marine ves- - 30 sel for assisting in moving the entire ship or one end = of the ship sideways for instance for docking purpos- - es.

N The tunnel thrusters have been developed fur- a ther by making such retractable i.e., the thruster

N 35 unit may be kept within the hull, but it may be low- ered below the hull i.e., below the baseline of the marine vessel. When the thruster unit is in a lowered position, it may be rotated round a vertical axis, and it may thus be used to generate thrust in any desired direction for driving and steering purposes. These re- tractable thrusters having a tunnel mode and a drive mode may be called as combi thrusters.

One possible problem of these combi thrusters may be that a part of flow in when the thruster is in a tunnel mode may bypass the propeller. Particularly marine vessels having a well for receiving and moving the thruster unit in connection with the tunnel may lead to a leak of the flow from the tunnel to the well and pass the propeller of the thruster unit. This may cause inefficiency to the thrust of the thruster. It may also increase noise and fuel consumption. Another drawback of prior art may be flow resistance of the structures that may hamper an efficiency and a steera- bility of the thruster in the drive mode in a lowered position. An examples of prior art retractable thrust- ers are shown in US 3,550,547 and US 5,522,335A.

OBJECTIVE OF THE INVENTION

The objective of the invention is to allevi- ate the disadvantages mentioned above.

SUMMARY

N According to first aspect, the present inven-

N tion provides a flow guide arrangement of a retracta-

N ble thruster unit, the retractable thruster unit com- = 30 prising a thruster housing and a stem for connecting

I the thruster housing to a support and lifting struc- & ture, wherein the thruster housing is arranged rotata-

N ble around an axis of the stem, a propeller arranged jo rotatable relative to a longitudinal axis of the

O 35 thruster housing, and a drive means for rotating the propeller.

According to the invention the flow guide is arranged on the periphery of the thruster housing on a side opposite to the propeller. In an embodiment the flow guide may be arranged on the periphery of the thruster housing on a side opposite to the propeller in relation to a plane that is parallel to a plane perpendicular to the longitudinal axis L of the thruster housing and aligned with the axis V of the stem. In an embodiment the flow guide may be arranged on the periphery of the thruster housing on a side op- posite to the propeller in relation to the axis of the stem.

According to a second aspect the present in- vention provides a retractable thruster unit compris- ing a thruster housing and a stem for connecting the thruster housing to a support and lifting structure, wherein the thruster housing is arranged rotatable around an axis of the stem, a propeller arranged ro- tatable relative to a longitudinal axis of the thrust- er housing, and a drive means for rotating the propel- ler, and a nozzle arranged on the thruster unit around the propeller.

According to a third aspect the present in- vention provides a system comprising a retractable thruster unit and a well for receiving the retractable thruster unit for marine vessel comprising a hull and a through hole i.e., a tunnel from a first side of the

N hull to the second side of the hull, wherein the well

N is arranged cross the tunnel, an opening is arranged

S 30 from the well to outside the hull for moving the - thruster unit outside of the hull, wherein the system = comprises the retractable thruster unit with a flow ” guide arrangement according to any one of the embodi-

N ments mentioned below or above alone or together with a 35 any other embodiment.

N The technical effect is that with the flow guide a flow leakage i.e., a bypass flow, and/or tur-

bulent flow can be minimized when the retractable thruster is in a tunnel position. In a drive mode, when the thruster unit is outside the hull, a low flow resistance and a good steerability may be achieved.

The flow guide arrangement, the retractable thruster unit, and the system are characterized by what is stated in the independent claims.

Some other embodiments are characterized by what is stated in the other claims. Inventive embodi- ments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims.

The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub- tasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the fol- lowing claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodi- ments.

In an embodiment of the flow guide arrange- ment the flow guide may comprise a front face and a back face and a guide wall connecting the front face to the back face. An advantage for the flow guide is

N that by arranging the flow guide a thrust in the tun-

N nel mode may be enhanced and a leak to the well in the

S 30 tunnel position of the retractable thruster may be ef- —- ficiently minimized. The steering properties in the = drive mode i.e., when the retractable thruster is out- + side the hull, may be maintained at a high level. A

N flow resistance may be kept at a low level. a 35 In an embodiment of the flow guide arrange-

N ment the flow guide may have at least one of an oval shape, an annular shape, a ring-like shape, or polygo-

nal shape in a plane perpendicular to the longitudinal axis of the thruster housing. An advantage of this is that an oval shape, an annular shape, a ring-like shape, or a polygonal shape is easy to manufacture. 5 They may be used alone and/or with combination with at least one other shape. Their flow guiding properties are high.

In an embodiment of the flow guide arrange- ment the flow guide may comprise at least one of a semi-oval shape, a semi-annular shape, a semi-ringlike shape, or an open polygonal shape or a combination of at least one other shape in a plane perpendicular to the longitudinal axis of the thruster housing. An ad- vantage is that flow guide may be configured rather small in size and the flow resistance may be minimized in drive mode and at the same time the flow guiding ability may be kept at a high level. Furthermore, a plurality of these kind of flow guides may be used to- gether.

In an embodiment of the flow guide arrange- ment the flow guide may be a one-piece part. An ad- vantage is that it is easy to manufacture and assem- ble. Its strength may be optimized.

In an embodiment of the flow guide arrange- ment the flow guide may comprise multiple parts. An advantage of this is that the flow guide may be ar- ranged of a plurality of different parts possibly hav-

N ing different properties and/or shapes. Its adaptabil-

N ity for use with different kind of applications is

S 30 good. In an embodiment the polygonal shape of the flow - guide may be made for example by combining a plurality = of plate-like pieces to form a flow guide. In an em- ” bodiment of the flow guide plate-like pieces may be

N combined for example by welding or by glueing. In an a 35 embodiment flow guide may comprise plate like pieces

N combined by using fixing members e.g. nuts and bolts, an/or rivets.

In an embodiment of the flow guide arrange- ment the flow guide may be arranged at a distance from the longitudinal axis. An advantage is that the flow may effectively be guided at a distance from the lon- gitudinal axis, and this effectively minimize the leak flow in the tunnel position. Furthermore, it operates effectively when the propeller is rotated in forward and in reverse directions.

In an embodiment of the flow guide arrange- ment the flow guide may comprise a first end and a second end and wherein a central angle from the longi- tudinal axis between the first end and the second end may be about 20 to 360 degrees. An advantage is that a size of the flow guide of this type may be easily var- ied according to a need of the application.

In an embodiment of the flow guide arrange- ment the distance from the longitudinal axis to the flow guide may be shorter than a distance from the longitudinal axis to a nozzle possible arranged around the propeller in a plane perpendicular to longitudinal axis. An advantage is that when the flow guide size may be arranged small, the flow resistance may be min- imized, and at the same time the flow control proper- ties may be maintained at a high level.

In an embodiment of the flow guide arrange- ment the flow guide may be arranged on the thruster housing coaxially with the longitudinal axis of the

N thruster housing. An advantage is that the flow is ef-

N fectively guided between the flow guide and the

S 30 thruster housing. In an embodiment the flow guide may - be arranged on the thruster housing in an inclination = with the longitudinal axis of the thruster housing. An ” advantage is that arranging flow guide in an inclina-

N tion with the flow guide may be suitable solution for a 35 some applications in guiding the flow.

N In an embodiment of the flow guide arrange- ment a distance from the back face to a lower part and/or an upper part of the front face of the flow guide is longer than the distance from the back face to other part of the flow guide in a plane parallel to a plane comprising the longitudinal axis of the thruster housing and the axis of the stem. An ad- vantage for this is that the flow guide guides the flow effectively for example in embodiments in which the well is of a cylindrical form.

In an embodiment of a retractable thruster unit comprising a thruster housing and a stem for con- necting the thruster housing to a support and lifting structure, wherein the thruster housing may be ar- ranged rotatable around an axis of the stem, a propel- ler arranged rotatable relative to a longitudinal axis of the thruster housing, and means for rotating the propeller, and a nozzle arranged on the thruster unit around the propeller. The retractable thruster unit may comprise a flow guide arrangement of any one of the embodiments mentioned above lone or in a combina- tion with other embodiment (s). An advantage is that a retractable thruster unit may be provided with effec- tive flow guiding properties in the tunnel mode and at the same time good steerability and low flow re- sistance of the thruster unit may be achieved.

In an embodiment of the retractable thruster unit the retractable thruster unit is configured to be moved in a space i.e., a well arranged in a hull of

N the marine vessel between two positions: a retracted

N position in which the thruster unit is arranged to op-

S 30 erate in a tunnel of a hull of the marine vessel and a - second position in which the thruster unit is arranged = to operate outside of the hull of the marine vessel. ” In an embodiment the system may comprise a

N retractable thruster unit and a well for receiving the a 35 retractable thruster unit for a marine vessel compris-

N ing a hull and a through hole i.e., a tunnel from a first side of the hull to the second side of the hull.

The well may be configured to be arranged in the hull of the marine vessel cross the tunnel. An opening may be arranged from the well to outside the hull for mov- ing the thruster unit outside of the hull. The system may comprise the retractable thruster unit with a flow guide arrangement according to any one of the embodi- ments mentioner above or below, alone or together with any other embodiment.

In an embodiment a wall structure may be ar- ranged to extend from a side wall plane of the well a distance in the space of the well for guiding the flow. An advantage is that the tunnel wall structure extending to the well may also guide flow between the side wall of the well and the retractable thruster unit with the flow guide. This may bring added thrust and further minimize the leak flow to the well.

In an embodiment the marine vessel may com- prise the retractable thruster unit with a flow guide arrangement according to any one of the embodiments mentioned above alone or combined with other embodi- ment (s).

In an embodiment of the marine vessel the tunnel may comprise a tunnel wall structure extending from a side wall plane of the well a distance in the space of the well. An advantage is that the tunnel wall structure extending to the well may also guide flow between the side wall of the well and the re-

N tractable thruster unit with the flow guide. This may

N bring added thrust and further minimize the leak flow

S 30 to the well.

E BRIEF DESCRIPTION OF THE DRAWINGS

= The accompanying drawings, which are included 0 to provide a further understanding of the invention

N 35 and constitute a part of this specification, illus-

N trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

Figure 1 is a schematical perspective view of an embodiment of a flow guide arrangement and a re- tractable thruster unit,

Figure 2 is a schematical side view of an em- bodiment of the flow guide arrangement and the re- tractable thruster unit,

Figure 3 is a schematical face view of an em- bodiment of the flow guide arrangement and the re- tractable thruster unit as seen from a direction of an arrow A of Figure 2,

Figure 4 is a schematical perspective view of an embodiment of a flow guide arrangement and a re- tractable thruster unit,

Figure 5 is a schematical a side view of an embodiment of the flow guide arrangement and the re- tractable thruster unit,

Figure 6 is a schematical a face view of an embodiment of the flow guide arrangement and the re- tractable thruster unit as seen from a direction of an arrow A of Figure 5,

Figure 7 is a schematical perspective view of an embodiment of a retractable thruster unit in a tun- nel position, and a portion of the tunnel and a well partially cut in vertical plane,

Figure 8 is a schematical perspective view of

N an embodiment of a flow guide arrangement and a re-

N tractable thruster unit,

S 30 Figure 9 is a schematical partial side view - of an embodiment of the retractable thruster unit in a = retracted position, a tunnel position, and a portion ” of the tunnel and a partial cross section the well in

N vertical plane, a 35 Figure 10 is a schematical partial side view

N of an embodiment of the retractable thruster unit in an extended position, a lower operating position, and a portion of the tunnel and the well partially cut in vertical plane,

Figure 11 is a schematical side view of a ma- rine vessel provided with an embodiment of the re- tractable thruster unit, and

Figure 12 is a schematical perspective view of an embodiment of the retractable thruster unit in an extended position, a lower operating position, and a portion of the tunnel and the well.

DETAILED DESCRIPTION

Figure 11 illustrates an embodiment of a ma- rine vessel 100. The marine vessel 100 may be provided with a retractable thruster unit 1. In an embodiment the marine vessel 100 may be provided with a tunnel 20 arranged in a hull 101 of the marine vessel 100. In an embodiment the tunnel 20 may be arranged to extend from a first side, for example from a starboard side, of the hull 101 to the second side, for example to a port side, of the hull. In an embodiment the tunnel 20 may be a through hole from a first side to the second side of the hull 101 of the marine vessel 100. In an embodiment the retractable thruster unit 1 may be ar- ranged to be moved between a retracted position (fig- ure 9) and an extended position (figure 10). In the retracted position i.e., in a tunnel position, the

N thruster unit 1 may be arranged to able to operate as

O a tunnel thruster. In the extended position i.e., in a

A drive position, the thruster unit 1 may be arranged to ? 30 able to operate as an azimuth thruster. In the drive

T position the thruster unit 1 may be arranged to rotate = around an axis V. In an embodiment the axis V may be a = vertical axis. In an embodiment the axis V may be axis

D of a stem 3. In the extended position the thruster

N 35 unit 1 may be arranged outside the hull 101 as in fig-

N ure 11. In an embodiment the thruster unit 1 may be arranged to operate as a combi thruster having two op-

erating modes: a tunnel mode in the retracted posi- tion, and a drive mode in the extended position, in which the thruster unit is arranged outside the hull.

In an embodiment the thruster unit 1 may be kept with- in the hull 101 but it may be lowered below the hull 101 i.e., below the baseline of the marine vessel.

When the thruster unit is lowered position, it may be rotated round a vertical axis, and it may thus be used to generate thrust in any desired direction for driv- ing and steering purposes. In figure 11 the thruster unit 1 is in the drive mode. In an embodiment the re- tractable thruster may be arranged to be moved with a moving device between the retracted position and the extended position. In an embodiment the moving device may be for example a hydraulic moving device for mov- ing the thruster unit between the retracted position and the extended position. In an embodiment of figure 10 the moving and supporting devices are illustrated schematically as a moving and supporting unit 31. In on embodiment of figure 12 the moving and supporting unit 31 may comprise guides 33 and lifting device 34 for moving the thruster unit. The moving and support- ing unit 31 may also comprise a rotating device 35 of the thruster unit for rotating the thruster unit in relation to the axis V. In an embodiment the moving and supporting unit 31 may comprise a holding device for station keeping and/or holding the thruster unit

N in the retracted and/or lowered position. In an embod-

N iment a drive device for rotating the propeller 4,

S 30 such as a motor 36, may be arranged in connection with - the thruster unit. In an embodiment the moving and = supporting unit may be a rotation unit for rotating ” the thruster unit around a pivot point or a fulcrum

N between the tunnel position and the drive position. a 35 In figures 1 to 3 an embodiment of the

N thruster unit is illustrated. The thruster unit 1 may comprise a thruster housing 2. In an embodiment the thruster housing 2 may be a pod for example for an en- gine and or a transmission. In figures the thruster housing 2 has a first end i.e., a front end 9, and a second end i.e., a rear end. In a rear end of the thruster housing may be arranged a propeller 4. In an embodiment an axis L i.e., a longitudinal axis, is il- lustrated in the figures. In an embodiment the axis L may be parallel with a rotational axis of the propel- ler 4. A stem 3 may be arranged to extend from the thruster housing. In an embodiment the stem 3 may be arranged to extend from the thruster housing 2 to a support device of the thruster unit 1. In an embodi- ment the support device may be connected to a moving device. In an embodiment the moving device may be a lifting device. In the upper end of the stem 3 may be arranged a connecting device for connecting the thruster unit 1 to the moving device. The thruster may be arranged rotatable in relation to an axis V. In an embodiment the axis V is a vertical axis. In a rear end of the housing may be arranged a propeller 4. In an embodiment of the figures the propeller 4 may have several blades 8. In the figures the propeller 4 has four blades 8, but the propeller may have more blades 8 or less blades than in an embodiment of the figures.

In an embodiment of the thruster unit 1, the thruster housing 2 and the propeller 4 with the thruster housing 2 may be rotated to any horizontal

N angle around the axis V.

N In an embodiment the propeller 4 may be driv-

S 30 en by a driving motor possible via a driving shaft and - a gear. Part of the driving motor or the gear may be = situated in the thruster housing 2. In an embodiment ” the stem 3 may be a cylinder like structure having a

N space surrounded by the cylinder wall. In an embodi- a 35 ment part of the means for transmitting torque of the

N power to the propeller may be arranged to the space arranged in the stem 3. As mentioned above in an em-

bodiment the engine or motor may be arranged in the thruster housing 2.

In an embodiment a nozzle 5 may be arranged on the thruster unit. In an embodiment the nozzle 5 may be an annular structure arranged on the thruster unit. In an embodiment the nozzle 5 may be arranged coaxially with the propeller 4. In an embodiment the nozzle may have a front face 6 and a back face 7 and a surface between the front face and the back face of the nozzle. In an embodiment the nozzle opening may have a radial distance R1 from axis L. The nozzle 5 may be arranged to the thruster housing by arms 11.

In an embodiment of a flow guide arrangement a flow guide 10 is arranged to the thruster unit 1. In an embodiment the flow guide 10 may be a hydrodynamic device attached to the thruster unit 1 with a purpose to improve the hydrodynamic properties and to control the flow. In an embodiment the flow guide 10 may be arranged on the periphery of the thruster housing 2.

In an embodiment of the flow guide arrangement the flow guide 10 may be arranged to control the flow in tunnel conditions. The flow guide 10 may be arranged to work as a single flow control element or interact with other flow control elements. In an embodiment the other flow control elements may comprise one or more of the following: a thruster nozzle 5, a tunnel wall, a thruster housing 2, a stem 3, a propeller 4, an arm

N 11, and/or walls 26, 27, 28 of a space crossing the » tunnel 2 i.e., a well 22.

S 30 In an embodiment of the flow guide arrange- —- ment the flow guide 10 may be arranged to the thruster = unit 1 at a distance from the propeller end of the ” thruster unit in a direction of the axis L. In an em-

N bodiment the flow guide 10 may be arranged on a part a 35 of the thruster unit that is on the other end of the

N thruster unit than the propeller 4. In an embodiment the flow guide 10 may be arranged on the periphery of the thruster housing on a side opposite to the propel- ler in relation to a plane P (Fig 8) that is parallel to a plane perpendicular to the longitudinal axis L of the thruster housing 2 and aligned with the axis V of the stem 3. In an embodiment the flow guide 10 may be arranged on the periphery of the thruster housing 2 on a side opposite to the propeller 4 in relation to the axis V of the stem 3. In an embodiment the axis V of the stem 3 may be a vertical axis. In an embodiment the plane P may situated between the propeller 4 and the front end 9 of the thruster housing 2. In an em- bodiment the plane P may be aligned with the axis V of the stem 3. In an embodiment the plane P may be per- pendicular with the longitudinal axis L of the thrust- er housing 2.

In an embodiment of the flow guide arrange- ment the flow guide 10 may have a curved shape in a plane perpendicular to axis L. In an embodiment the shape of the flow guide may have a radius of RI i.e., a distance from the axis 1 in a plane perpendicular to axis L. In an embodiment the radius R1 may be a con- stant. In an embodiment the radius RI i.e., the dis- tance from the axis 1 in a plane perpendicular to axis

L may vary.

In an embodiment the flow guide may have a polygonal shape in a plane perpendicular to axis L. In an embodiment the polygonal shape of the flow guide

N may comprise several portions that may be arranged so

N that an angle is formed between the portions.

S 30 In an embodiment of the flow guide arrange- - ment the flow guide 10 may have an oval shape in a = plane perpendicular to axis L. In an embodiment of the ” flow guide arrangement the flow guide 10 may have an

N annular shape in a plane perpendicular to axis L. In a 35 an embodiment of the flow guide arrangement the flow

N guide 10 may have a ring-like shape in a plane perpen- dicular to axis 1.

In an embodiment of the flow guide arrange- ment the flow guide 10 may have a semioval shape in a plane perpendicular to axis L. In an embodiment the flow guide 10 may have a semi-annular shape in a plane perpendicular to axis L. In an embodiment the flow guide 10 may have a semiring-like shape in a plane perpendicular to axis L.

In an embodiment of the flow guide arrange- ment the flow guide 10 may be a one-piece part. In an embodiment the flow guide 10 may comprise multiple parts. In an embodiment the flow guide 10 may comprise a plurality of curved parts. An embodiment of the flow guide arrangement may comprise a plurality of single flow guides 10.

In an embodiment the flow guide 10 may be a tubelike part arranged on the thruster unit 1 as il- lustrated in figures 1 to 3 and 7 to 10.

In an embodiment of the flow guide arrange- ment the flow guide 10 may be arranged coaxially with the propeller axis and/or longitudinal axis L of the thruster housing 2 the thruster unit 1. In an embodi- ment the flow guide may be arranged to the thruster housing 2 with arms 11. In an embodiment of the flow guide arrangement the flow guide may be arranged on the stem 3 of the thruster unit.

In an embodiment of the flow guide arrange- ment the flow guide 10 may have a front face 12 and a

N back face 13. The flow guide 10 may have a guide wall

N 10’ connecting the front face 12 and the back face 13.

S 30 The guide wall 10’ may have a first side and a second - side. In an embodiment a first side and/or the second = side of the guide wall of the flow guide may have a ” curved form. In an embodiment the first side and/or

N the second side of the guide wall 10’ may have a con- a 35 vex form in a cross direction of the flow guide. In an

N embodiment the first side of the guide wall 10’ may have a convex form and the second side of the guide wall 10’ may have a concave form. In an embodiment the first side of the guide wall 10’ may have a concave form and the second side of the guide wall may have a convex form. In an embodiment the flow guide may have a wing like form. In an embodiment the guide wall 10” between the front face 12 and the back face 13 of the flow guide 10 may have extend a distance X in a plane parallel with the axis L. In an embodiment the dis- tance X in a plane parallel with the axis L may be constant between the front face 1? and the back face 13 of the flow guide 10. In an embodiment the front face 12 of the flow guide 10 may extend more from the back end 13 in lower part of the flow guide i.e., the distance X in a plane parallel with the axis L is longer in the lower part of the flow guide 10 than in the upper part of the flow guide 10. In an embodiment the front face 12 may extend more from the back end 13 in lower part of the flow guide i.e., the distance X in a plane parallel with the axis L is greater in the lower part of the flow guide 10 than in the middle part of the flow guide 10. In an embodiment the front face 12 and the surface of the flow guide 10 may ex- tend in an upper part of the flow guide 10 so that the distance X in a plane parallel with the axis L may be greater in the upper part of the flow guide than in the middle part of the flow guide 10. This form of the flow guide 10 may be useful especially with the well

N 22 having a cylinder like side wall. A distance be-

N tween the wall of the well 22 and the flow guide 10 of

S 30 the thruster unit 1 may be made short thus enhancing - the flow guiding abilities near the tunnel opening 30 = in the tunnel mode of the flow guide 10 of the thrust- - er unit 1.

N In an embodiment the thruster housing 2 of a 35 the thruster may have a tapering shape, tapering to-

N wards a front end 9 of the thruster housing 2. In an embodiment the front end 9 of the thruster housing 2 may have a dome like shape. A wall of the thruster housing 2 may have a small radius i.e., radial dis- tance from the axis L, at least near the front end 9 of the thruster housing. The radial distance from the axis L to an outer surface of the wall of the thruster housing 2 may be vary in a plane perpendicular to axis

L, when moving from the front end 9 towards a middle part of the thruster housing 2. In an embodiment the radial distance from the axis L to an outer surface of the thruster housing may increase when moving from the front end 9 of the thruster housing towards a middle part of the thruster housing 2.

In an embodiment the radial distance RI to a guide surface 10’ of the flow guide 10 from axis L in a plane perpendicular to axis L may be small in rela- tion to the radial distance R2 to a wall of the nozzle 5 from axis L in a plane perpendicular to axis L. In an embodiment the radial distance RI] to a guide sur- face 10’ of the flow guide 10 from axis 1 in a plane perpendicular to axis L < radial distance R2 to a wall of the nozzle 5 from axis L in a plane perpendicular to axis L i.e., (R1 < R2).

In an embodiment the flow guide 10 may have a tapering form. In an embodiment the flow guide 10 may be configured to taper from the front face 12 towards back face 13. In an embodiment the flow guide may be configured to taper from the back face 13 towards the

N front face 12.

N In an embodiment the flow guide 10 may be ar-

S 30 ranged in an inclined position in a relation to the - longitudinal axis L. = As mentioned above in an embodiment of the ” flow guide arrangement the flow guide 10 may have a

N semioval shape in a plane perpendicular to axis L. In a 35 an embodiment the flow guide 10 may have a semi-

N annular shape in a plane perpendicular to axis L. In an embodiment the flow guide 10 may have a semiring-

like shape in a plane perpendicular to axis L. In fig- ures 4 to 6 illustrate an example of the flow guide forming a wing like structure. In an embodiment the flow guide may have a form of a section of a circle or a section of another ring-like form. If we approximate that the flow guide may have a form of a section of a circle in a plane perpendicular to axis L, as illus- trated in figure 6, then the length of an arc 1 of the flow guide in degrees may be 1 = 2mR10/360, where « is a central angle, R1 is the radius. In an embodiment the central angle o may vary according to the applica- tion. In an embodiment the central angle &« may be an angle between a line drawn from the axis L to a first end 14 of the flow guide 10 and a second line from the axis L to a second end 15 of the flow guide. In an em- bodiment the central angle o of the flow guide 10 may be for example 20 to 360 degrees. In an embodiment the central angle may be 20 to 270 degrees. In an embodi- ment the central angle may be 45 to 150 degrees.

In an embodiment of the flow guide arrange- ment of figures 4 to 6 the flow guide 10 is arranged to the thruster housing 2 of the thruster unit 1 via arms 11. In an embodiment the flow guide 10 may be ar- ranged on a lower portion of the thruster unit in a plane perpendicular to the axis 1, as illustrated for example in figure 6. However, in another embodiment of the flow guide arrangement the flow guide may be ar-

N ranged on other portions of the thruster unit in a

N plane perpendicular to the axis L. In an embodiment

S 30 the flow guide 10 or a part of the flow guide arrange- —- ment may be arranged on an upper portion of the = thruster unit in a plane perpendicular to the axis L. ” In an embodiment the flow guide or a part of the flow

N guide arrangement of the thruster unit may be arranged a 35 on a left side and/or on a right side of a vertical

N plane parallel of axis L in a plane perpendicular to axis L.

In an embodiment the thruster unit may be comprise a closing plate 23 arranged via a support to the thruster. The closing plate 23 may close and open an opening 21 arranged in the hull 101 for moving the retractable thruster between the first position and the second position. In an embodiment a first support 24 may be arranged from the thruster housing 2 to the closing plate. In an embodiment the first support 24 may be arranged from the nozzle 5 to the closing plate 23. In an embodiment a second support 25 may be ar- ranged to support the closing plate 23. In an embodi- ment the flow guide 10 may be arranged to be supported by the second support 25. In an embodiment there may be arranged a plurality of first supports 24 and/or second supports 25. In an embodiment the closing plate may be arranged to close the opening 21 arranged in the hull to prevent a flow through the opening when the thruster unit is in its retracted position i.e., in the tunnel position (Fig 9). In an embodiment the closing plate may significantly improve the perfor- mance of the thruster unit in the tunnel mode, while also reducing the drag of the vessel. Without a clos- ing plate the thruster may intake water through the opening of the bottom well in an inefficient manner, which may cause the thrust to be significantly re- duced. On open water conditions i.e., in the drive mode, the closing plate 23 may cause a small reduction

N in maximum thrust.

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S 30 In the tunnel position the thruster unit 1 - may be placed in a well 22. In an embodiment the well = 22 may be a space arranged in the hull 101. The well ” 22 may be arranged crossing the tunnel 20 arranged in

N the hull. The well 22 may have side wall(s), 26, 27, a 35 28 defining the space of the well. A tunnel opening 30

N of the tunnel 20 may be arranged to extend through the well 22. The space of the well may extend in a direc-

tion perpendicular to a longitudinal axis of the tun- nel. In an embodiment there may be openings between the walls of the well 22 and the thruster unit 1 when the thruster is in the tunnel position. When the pro- peller 4 of the thruster unit 1 is rotated by the mo- tor water starts to flow in the tunnel 20 from the first side to the second side. The flow guide 10 may guide the flow so that water may flow to the propeller 4 and by-pass flow passing the propeller 4 may be ef- fectively reduced. It has proved to be useful to ar- range the flow guide 10 to the thruster unit 1. In an embodiment flow may attach to in and outsides of the flow guide 10, which may guide the flow between tunnel and nozzle 5. Fast flow may be attached to the flow guide and guided from tunnel to the nozzle and to the propeller. In an embodiment an increase over 40 per- cent may be achieved in thrust. In an embodiment flow guide 10 may prevent the flow from diverting and being trapped to the well 22, thus greatly improving thrust.

It has been proved that the thruster unit with the flow guide 10 performs well also when the propeller 4 is driven in reverse when the thruster unit 1 is in the tunnel position. In an embodiment an increase over 25 percent may be achieved in thrust.

The flow guide may have several important benefits. The thruster unit with the flow guide 10 may give more thrust and/or with less fuel. Noise and vi-

N bration may be less. Moreover, the flow guide 10 may

N give further protection for the propeller.

S 30 In an embodiment of the flow guide operates —- also well in the drive mode i.e., the thruster unit 1 = moved outside the hull 101. The thruster unit with the ” flow guide 10 operates well when the propeller 4 is

N rotated with the motor in reverse direction in the a 35 drive mode. It has proven that the thruster unit with

N the flow guide operates well in the retractable thruster unit operated as a combi thruster i.e., in the tunnel mode and in the open water drive mode.

In an embodiment the tunnel 20 may have a wall portion extending a distance from the side wall of the well 22 a distance to the well space. In an em- bodiment may comprise a marine vessel 100 with the tunnel 20 extending from a first side of the hull to the second side of the hull wherein a well with side wall (s) forming a well space crossing the tunnel is arranged for receiving the retractable thruster unit with the flow guide as defined with above.

In an embodiment the disclosure relates also to a system comprising a retractable thruster unit 1 and a well 22 for receiving the retractable thruster unit 1 for a marine vessel 100 comprising a hull 101 and a through hole i.e., a tunnel 20 from a first side of the hull to the second side of the hull. The well 22 may be configured to be arranged in the hull of the marine vessel cross the tunnel 20. An opening 21 may be arranged from the well 22 to outside the hull 101, below the baseline of the hull, for moving the thrust- er unit 1 outside the hull. The system may comprise the retractable thruster unit 1 with a flow guide 10 arrangement according to any one of the embodiments alone or together with any other embodiment mentioned above or below.

In an embodiment a wall structure 32 may be

N arranged to extend from a side wall 26, 27 plane of

N the well 22 a distance in the space of the well 22 for

S 30 guiding the flow. In an embodiment the wall structure - may extend between the plane of the side wall 26, 27 = of the well 22 and the thruster unit 1 when the ” thruster unit is in a tunnel mode. In an embodiment

N the wall structure may be a tunnel extension. In an a 35 embodiment the tunnel extension may help guide the

N flow over the bottom well smoothly to the nozzle 5 and to the propeller 4, which results to higher thrust. In an embodiment there may be several tunnels and re- tractable thruster units arranged in the marine ves- sel. In an embodiment the tunnels and the retractable thruster units may be arranged grouped in the bow and/or in the stern of the vessel and/or spread on a length of a hull of the marine vessel.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

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REFERENCE SYMBOLS

1 Thruster unit 2 Thruster housing 3 Stem 4 Propeller 5 Nozzle 6 Front face of the nozzle 7 Back face of the nozzle 8 Propeller blade 9 Front end of the thruster housing 10 Flow guide 10’ Guide wall 11 Arm 12 Front face of the flow guide 13 Back face of the flow guide 14 First end of the flow guide 15 Second end of the flow guide

Tunnel 20 21 Opening 22 Well 23 Closing plate 24 First support

Second support 25 26 First side wall 27 Second side wall 28 Third side wall

S

N 30 Tunnel opening

S 30 31 Moving and supporting unit - 32 Wall structure

I 33 Guide + 34 Lifting device

N 35 Rotating device a 35 36 Motor

N

100 Marine vessel

101 Hull

IL Longitudinal axis

P Plane

V Vertical axis/Stem axis

X Length of the flow guide

R1 Radial distance to a wall of the flow guide from L in a plane perpendicular to axis L

R2 Radial distance to a wall of the nozzle from L in a plane perpendicular to axis L & Angle between a first end and a second end of an embodiment of the flow guide in a plane perpen- dicular to axis L

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Claims

1. A flow guide arrangement of a retractable thruster unit (1), the retractable thruster unit com- prising a thruster housing (2) and a stem (3) for con- necting the thruster housing (2) to a support and lifting structure, wherein the thruster housing (2) is arranged rotatable around an axis (V) of the stem (3), a propeller (4) arranged rotatable relative to a lon- gitudinal axis (L) of the thruster housing (2), and a drive means for rotating the propeller, wherein the flow guide (10) is arranged on the periphery of the thruster housing (2) on a side opposite to the propel- ler (4) in relation to a plane (P) that is parallel to a plane perpendicular to the longitudinal axis (L) of the thruster housing (2) and aligned with the axis (V) of the stem (3).

2. The flow guide arrangement of a retracta- ble thruster unit according to claim 1, wherein the flow guide comprises a front face (12) and a back face (13) and a guide wall (107) connecting the front face (12) to the back face (13).

3. The flow guide arrangement of a retracta- ble thruster unit according to claim 1 or 2, wherein the flow guide (10) comprises at least one of an oval shape, an annular shape, a ring-like shape or a poly- nomial shape, or any combination of two or more of N these shapes in a plane perpendicular to the longitu- O dinal axis (L) of the thruster housing (2).

N 4. The flow guide arrangement of a retracta- ? 30 ble thruster unit according to any one of claims 1 to T 3, wherein the flow guide (10) comprises at least one z of a semi-oval shape, a semi-annular shape, a semi- = ringlike shape or an open polynomial shape, or any D combination of two or more of these shapes in a plane N 35 perpendicular to the longitudinal axis (L) of the N thruster housing (2).

5. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to 4, wherein the flow guide (1) is a one-piece part.

6. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to 4, wherein the flow guide (10) comprises multiple parts.

7. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to 6, wherein the flow guide is arranged at a distance (R1) from the longitudinal axis (L).

8. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to 7, wherein the flow guide comprises a first end (14) and a second end (15) and wherein a central angle (o) from the longitudinal axis (L) between the first end (14) and the second end (15) is about 20 to 360 de- grees.

9. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to 8, wherein the distance (R1) from the longitudinal ax- is (L) to the flow guide (10) is shorter than the dis- tance (R1) from the longitudinal axis (L) to a nozzle (5) arranged around the propeller (4) in a plane per- pendicular to longitudinal axis (L).

10. The flow guide arrangement of a retracta- ble thruster unit according to any one of claims 1 to N 9, wherein the flow guide (10) is arranged on the N thruster housing (2) coaxially with the longitudinal S 30 axis (L) of the thruster housing (2). -

11. The flow guide arrangement of a retracta- = ble thruster unit according to any one of claims 1 to + 10, wherein a distance (X) from the back face (13) to N a lower part and/or an upper part of the front face a 35 (12) of the flow guide (10) is longer than the dis- N tance (X) from the back face (13) to other part of the flow guide in a plane parallel to a plane comprising the longitudinal axis (L) of the thruster housing and the axis (V) of the stem.

12. A retractable thruster unit comprising a thruster housing (2) and a stem (3) for connecting the thruster housing (2) to a support and lifting struc- ture, wherein the thruster housing (2) is arranged ro- tatable around an axis (V) of the stem (3), a propel- ler (4) arranged rotatable relative to a longitudinal axis (L) of the thruster housing (2), and a drive means for rotating the propeller, and a nozzle (5) ar- ranged on the thruster unit (1) around the propeller (4), wherein the retractable thruster unit comprises a flow guide arrangement according to any one of claims 1 to 11.

13. The retractable thruster unit according to claim 12, wherein the retractable thruster unit (1) is configured to be moved in a space i.e. a well (22) arranged in a hull (101) of the marine vessel (100) between two positions: a retracted position in which the thruster unit is arranged to operate in a tunnel (20) of a hull (101) of the marine vessel (100) and a second position in which the thruster unit is arranged to operate outside of the hull (101) of the marine vessel (100).

14. A system comprising a retractable thrust- er unit (1) and a well (22) for receiving the re- tractable thruster unit (1) for a marine vessel (100) N comprising a hull (101) and a through hole i.e., a N tunnel (20) from a first side of the hull to the sec- S 30 ond side of the hull, wherein the well (22) is config- —- ured to be arranged in the hull of the marine vessel = cross the tunnel (20), an opening (21) is arranged ” from the well to outside the hull (101) for moving the N thruster unit (1) outside of the hull, wherein the a 35 system comprises the retractable thruster unit (1) N with a flow guide (10) arrangement according to any one of claims 12 to 13.

15. The system according to claim 15, wherein a wall structure (32) is arranged to extend from a side wall (26, 27) plane of the well (22) a distance in the space of the well (22) for guiding the flow.

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