Patent Application
20160325810
The present invention relates to a propulsion device for a proximity twin-screw vessel having a shaft bracket, and a ship.
Priority is claimed on Japanese Patent Application 2014-233258, filed Nov. 18, 2014, the content of which is incorporated herein by reference.
A propulsion device of a ship generally obtains a propulsive force by rotating a propeller using a main engine.
In the case of a ship known as a single screw vessel including one main engine and one propeller, when the ship is increased in size, a load level applied to the one propeller is increased. In order to obtain a sufficient propulsive force, a rotational speed of the propeller should be increased or a diameter of the propeller should be increased. Accordingly, since a circumferential speed of the propeller is increased, a pressure in the vicinity of a propeller blade end is lowered, and cavitation that is a phenomenon in which bubbles are generated in water may excessively occur. When cavitation occurs, the hull is vibrated through the stern and the bottom of the ship. In addition, erosion occurs in the propeller due to the cavitation and exerts a bad influence on durability of the propeller.
Here, it is known that the above-mentioned problems can be solved in a ship known as a twin-screw vessel including two main engines and two propellers. In a twin-screw vessel, a load level per propeller can be reduced to improve propeller efficiency, and cavitation can be suppressed.
As examples in which two propellers are disposed at the stern, an overlapping propeller (OLP) type, an interlock propeller type, a type in which propellers are arranged at left and right sides in parallel, and so on, are provided.
Among these, in the OLP type, the two propellers are disposed to be deviated at front and rear sides thereof, and at least portions of the two propellers when seen from the stern are disposed to overlap each other. The propulsion performance can be improved by 5 to 10% than the single screw vessel by employing the OLP type.
In the interlock propeller type, a blade of the other propeller is disposed to enter between blades of one propeller.
In the type in which the propellers are arranged at left and right sides in parallel, the propellers are disposed at the same position in a vessel longitudinal direction in parallel.
However., when the OLP type is used, the propeller disposed at the rear side alternately passes through a fast flow accelerated by the front propeller and a slow flow in the vicinity of a center in a vessel widthwise direction (a widthwise direction of the vessel) during one rotation. For this reason, a load applied to propeller blades of the rear propeller is largely varied. As a result, in the twin-screw vessel using the OLP type, in comparison with the single screw vessel, a bearing force applied to a bearing of a propeller shaft of the rear propeller may become excessive.
In addition, since a rotational flow having a high velocity is newly formed by rotation of the front propeller, the rear propeller should be operated in an extremely complicated flow, which widens a range in which cavitation occurs. As a result, excessive vibration may be generated. Further, when tip vortex cavitation (blade end vortex cavitation) occurs from front ends of propeller blades of the front propeller, erosion may occur in the propeller blades due to burst of the generated bubbles on propeller blade surfaces of the rear propeller.
In addition, in the case of the interlock propeller type, rotation of both of the propellers should be controlled such that the blades of one propeller and the blades of the other propeller do not interfere with each other and roll control becomes difficult. In to addition, in the worst case, when the blades of one propeller interfere with the blades of the other propeller, the propeller may be damaged.
The present invention is directed to provide a propulsion device for a proximity twin-screw vessel having a shaft bracket and a ship that are capable of improving propulsion performance while suppressing cavitation, erosion, or the like.
According to a first aspect of the present invention, there is provided a propulsion device for a proximity twin-screw vessel having a shaft bracket, the propulsion device includes: a port propeller and a starboard propeller installed at a stern hull; one rudder disposed at a center in a vessel widthwise direction of the stern hull or two rudders constituted by a port rudder and a starboard rudder in rear of the port propeller and the starboard propeller; and shaft brackets installed in front of the port propeller and the starboard propeller, respectively, and configured to rotatably support propeller shafts of the port propeller and the starboard propeller, wherein a distance between a tip end of a propeller blade of the port propeller and a tip end of a propeller blade of the starboard propeller at a center in the vessel widthwise direction is larger than 0 in and equal to or smaller than 1.0 m, and a rotational direction of the port propeller and the starboard propeller becomes an outer track rotating from the center in the vessel widthwise direction toward the outside over the port propeller and the starboard propeller.
In this way, since the starboard propeller and the port propeller are disposed to approach the vicinity of the center in the vessel widthwise direction (referred to as the proximity twin-screw type), a longitudinal vortex in the vicinity of the center in the vessel widthwise direction can be efficiently recovered, and propulsion performance can be improved. In addition, the starboard propeller and the port propeller do not interfere with each other like an interlock propeller. Then, since the starboard propeller and the port propeller are disposed in parallel, in comparison with the OLP type, risks such as an excessive bearing force in the rear propeller, expansion of a cavitation range, erosion, can be largely suppressed.
In the propulsion device for the proximity twin-screw vessel having the shaft bracket, provided that propeller diameters of the port propeller and the starboard propeller are Dp, a distance between a central position of the port propeller and the starboard propeller and a front edge of the rudder at a central height of the port propeller and the starboard propeller may be equal to or less than 1.0 Dp.
According to the above-mentioned configuration, a front edge of the rudder can approach the starboard propeller and the port propeller, and a slip stream from the starboard propeller and the port propeller can securely abut a rudder surface. Accordingly, control effectiveness of the rudder and propulsion performance can be improved.
In the propulsion device for the proximity twin-screw vessel having the shaft bracket, the stern hull may be a stern structure of a single screw vessel type.
According to the above-mentioned configuration, when the stern structure of the single screw vessel type is provided, an effect of the above-mentioned aspects can be particularly remarkably exhibited. In addition, in the stern structure of the single screw vessel type, in comparison with the case in which a skeg serving as the stern structure of the twin-screw vessel type is provided, a longitudinal vortex turning inward in the vicinity of the center in the vessel widthwise direction can be strengthened, and in the starboard propeller and the port propeller rotating along the outer track, the flow can be efficiently recovered and the propulsion performance can be improved.
In the propulsion device for the proximity twin-screw vessel having the shaft bracket, the shaft bracket may include a shaft support section configured to rotatably support the propeller shafts of the port propeller and the starboard propeller, and a strut configured to connect the shaft support section and the stern hull, and the strut may be formed to provide flows in an opposite direction of a rotational direction of the port propeller and the starboard propeller in upper sections of the port propeller and the starboard propeller.
According to the above-mentioned configuration, since flows in an opposite direction of the rotational direction of the port propeller and the starboard propeller are provided by the strut, a velocity in the rotational direction of the flows of the port propeller and the starboard propeller (10R) is relatively increased. Accordingly, in the starboard propeller (10R) and the port propeller, forward thrust can be further exhibited, and the propulsion performance can be improved.
In the propulsion device for the proximity twin-screw vessel having the shaft bracket, the shaft bracket may include a shaft support section configured to rotatably support the propeller shafts of the port propeller and the starboard propeller, and a strut configured to connect the shaft support section and the stern hull, the shaft support section may include one or more fins radially extending from an outer circumferential section of a lower section thereof, and each of the fins may be formed to provide flows in an opposite direction of a rotational direction of the port propeller and the starboard propeller in lower sections of the port propeller and the starboard propeller.
According to the above-mentioned configuration, since the flows in the opposite direction of the rotational direction of the port propeller and the starboard propeller are provided by the fins, a velocity in the rotational direction of the flows of the port propeller and the starboard propeller is relatively increased. Accordingly in the starboard propeller and the port propeller, forward thrust can be further exhibited, and the propulsion performance can be improved.
According to a second aspect of the present invention, a ship includes the propulsion device for the proximity twin-screw vessel having the shaft bracket according to any one of the above-mentioned aspects.
According to the above-mentioned configuration, as the starboard propeller and the port propeller are disposed to approach the vicinity of the center in the vessel widthwise direction, the propulsion performance can be improved. Risks such as generation of a bearing force, cavitation, erosion, and so on, in the starboard propeller and the port propeller can be largely suppressed.
According to the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship of the present invention, the propulsion performance can be improved while suppressing cavitation, erosion, the like.
Hereinafter, a propulsion device for a proximity twin-screw vessel having a shaft bracket and a ship of an embodiment of the present invention will be described with reference to the accompanying drawings.
Here, a twin-screw vessel (a ship, a proximity twin-screw vessel) 1 having a stern structure of a single screw vessel type that is a kind of multi-screw vessel is exemplarily described as a ship.
As shown in
The starboard propeller 10R is installed under a starboard side of the bottom 4 of the stern hull 3 of the ship, that is, the stern of the hull. The starboard propeller 10R is connected to one end of a starboard propeller shaft 12R. A starboard main engine 18R is installed at a starboard side in the stern hull 3. The starboard propeller shaft 12R passes through the stern hull 3 via a bossing 11R formed in the bottom 4 of the ship, and the other end is connected to the starboard main engine 18R. The starboard main engine 18R rotates the starboard propeller 10R via the starboard propeller shaft 12R.
The port propeller 10L is installed under the port side of the bottom 4 of the ship of the stern hull 3. The port propeller 10L is connected to one end of a port propeller shaft 12L. A port main engine 18L is installed at the port side in the stern hull 3. The port propeller shaft 12L passes through the stern hull 3 via a bossing 11L installed in the bottom 4 of the ship, and the other end is connected to the port main engine 18L. The port main engine I 8L rotates the port propeller 10L via the port propeller shaft 12L.
As shown in
The shaft brackets 13R and 13L includes tubular support sections 14R and 14L configured to rotatably support the starboard propeller shaft 12R and the port propeller shaft 12L, and a plurality of struts 15R, 16R, 15L and 16L extending upward from the tubular support sections 14R and 14L in a V shape and having upper ends connected to the bottom 4 of the stern hull 3.
The starboard propeller 10R and the port propeller 10L are symmetrically disposed with respect to a center C in a vessel widthwise direction to be spaced a distance from each other at which the propeller blades do not interfere with each other. That is, the twin-screw vessel 1 is a type in which the starboard propeller 10R and the port propeller 10L are disposed in parallel, rather than an OLP type or an interlock propeller type.
Here, a distance between the starboard propeller 10R and the port propeller 10L represents a distance d between propeller tips, which is a gap between the outermost circumferential section of the starboard propeller 10R and the outermost circumferential section of the port propeller 10L, at the center C side in the vessel widthwise direction. The distance d between the propeller tips may be set to be as small as possible while still avoiding any risk of contact between the propeller blades such that the starboard propeller 10R and the port propeller 10L are disposed to approach the vicinity of the center C in the vessel widthwise direction to capture the longitudinal vortex. The distance d between the propeller tips is determined as follows.
That is, since the twin-screw vessel 1 is a type in which the starboard propeller 10R and the port propeller 10L are arranged in parallel, the distance d between the propeller tips is set to be larger than 0 in. The distance d between the propeller tips may be equal to or larger than 0.1 m. This is so that the starboard propeller 10R and the port propeller 10L do not interfere with each other even when a machining error or an assembly error is considered.
In addition, the distance d between the propeller tips is preferably set to be equal to or less than 1.0 m, and more preferably equal to or less than 0.5 m. This is because reducing the distance d between the propeller tips as much as possible allows the longitudinal vortex close to the center C in the vessel widthwise direction to be captured and the propulsion performance to be further improved.
In
An example of this will be described below.
The starboard propeller 10R and the port propeller 10L can efficiently recover the longitudinal vortices V1 and V2 within regions S2 and S1 overlapping the region 80. Then, since an area obtained by summing the region S2 and the region S1 is increased as the distance d between the propeller tips is reduced, the propulsion performance can be further improved.
In addition, central heights of the starboard propeller 10R and the port propeller 10L may not be disposed at the same position. However, the central heights may be disposed at the same position in consideration of controllability of the twin-screw vessel 1.
In addition, front end sections 9 at the same heights as the starboard propeller 10R and the port propeller 10L of the stern hull 3 may be disposed closer to the bow side than the positions of the ends of the rotational surfaces of the starboard propeller 10R and the port propeller 10L near the bow side.
The rudder 40 is installed on the center C in the vessel widthwise direction in rear of the starboard propeller 10R and the port propeller 10L.
The rudder 40 is disposed closer to the rear side (the stern side) than the starboard propeller 10R and the port propeller 10L. The rudder 40 has a blade-shaped cross-sectional shape, and is attached to a rudder shaft 41 extending from the bottom 4 of the ship of the stern hull 3 in a vertical downward direction. The rudder 40 is rotated about the vertical axis together with the rudder shaft 41, and changes a course direction of the twin-screw vessel 1.
Here, a front edge 40f of the rudder 40, the starboard propeller 10R and the port propeller 10L may come as close to one another as possible. This is because rapid flows generated by the starboard propeller 10R and the port propeller 10L enter the rudder 40, and thus the control effectiveness of the rudder is improved. Specifically, when a propeller diameter of the starboard propeller 10R and the port propeller 10L is Dp, a distance L between a central position Pc of the starboard propeller 10R and the port propeller 10L and a front edge 40fp of the rudder 40 at a central height Ph of the starboard propeller 10R, and the port propeller 10L may be equal to or less than 1.0 Dp.
Accordingly, according to the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship of the above-mentioned first embodiment, since the starboard propeller 10R and the port propeller 10L are disposed to approach the vicinity of the center C in the vessel widthwise direction, the longitudinal vortex in the vicinity of the center C in the vessel widthwise direction can be efficiently recovered, and the propulsion performance can be improved. In addition, the starboard propeller 10R and the port propeller 10L do not interfere with each other like the interlock propeller type. Accordingly, the twin-screw vessel 1 can be easily manufactured. Then, since the starboard propeller 10R and the port propeller 10L are disposed in parallel, in comparison with the OLP type, risks such as an excessive bearing force of the rear-side propeller, expansion of a cavitation range, erosion, can be largely suppressed.
In this way, according to the twin-screw vessel 1, the propulsion performance can be further improved while suppressing generation of cavitation, erosion, or the like.
In addition, as propeller shafts 12R and 12L are exposed by setting a length of the bossing 11R and 11L in a lower limit and rear end sections thereof are supported by the shaft brackets 13R and 13L, auxiliary section resistance can be suppressed to be small. This can also contribute to improvement of the propulsion performance.
In addition, according to the propulsion device of the twin-screw vessel 1, the distance L between the central position Pc of the port propeller 10L and the starboard propeller 10R, and the front edge 40fp of the rudder 40 at the central height Ph of the port propeller 10L and the starboard propeller 10R is set to be equal to or less than 1.0 Dp. Accordingly, the front edge 40fp of the rudder 40 can approach the starboard propeller 10R and the port propeller 10L, and a slip stream can enter the rudder 40 from the starboard propeller 10R and the port propeller 10L. Accordingly, control effectiveness of the rudder can be improved.
In addition, according to the propulsion device of the twin-screw vessel 1, when the stern hull 3 has a stern structure of the single screw vessel type, the above-mentioned effect can be particularly remarkably exhibited. Further, the stern structure of the single screw vessel type can strengthen the longitudinal vortex turning inward in the vicinity of the center C in the vessel widthwise direction in comparison with the case in which a skeg serving as the stern structure of the twin-screw vessel type is provided, and in the starboard propeller 10R and the port propeller 10L that rotate along the outer track, the flow can be efficiently recovered to improve the propulsion performance.
Further, in the first embodiment, while the stern hull 3 of the twin-screw vessel 1 has the stern structure of the single screw vessel type, the embodiment is not limited thereto. In the stern hull 3, the skeg extending along the center C in the vessel widthwise direction may be provided in front of the rudder 40.
Next, a second embodiment of the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship according to the present invention will be described. Since the second embodiment to be described below is different from the first embodiment only in the configurations of the shaft brackets 13R and 13L, the same components as the first embodiment are designated by the same reference numerals, and overlapping description thereof will be omitted.
As shown in
The starboard propeller shaft 12R and the port propeller shaft 12L are rotatably supported by the shaft brackets 13R and 13L in front of the starboard propeller 10R and the port propeller 10L. Further, in the embodiment, struts 25R, 26R, 25L and 26L of the shaft brackets 13R and 13L have a blade-shaped cross-sectional shape perpendicular to a direction extending from the bottom 4 of the ship toward the tubular support sections 14R and 14L. Further, the struts 25R, 26R, 25L and 26L are formed to provide flows in an opposite direction of the rotational direction of the starboard propeller 10R and the port propeller 10L in the upper sections of the starboard propeller 10R and the port propeller 10L. That is, the starboard propeller 10R and the port propeller 10L are rotated along the outer tracks R2 and R1 outward from the center C in the vessel widthwise direction over the starboard propeller 10R and the port propeller 10L. Here, the struts 25R, 26R, 25L and 26L are installed to generate flows FR1 and FL1 from the outside in the vessel widthwise direction toward the center C in the vessel widthwise direction over the starboard propeller 10R and the port propeller 10L. Specifically, the struts 25R, 26R, 25L and 26L are formed to be inclined from front edge sections 25f and 26f toward rear edge sections 25r and 26r to gradually approach the center C in the vessel widthwise direction from a propeller shaft direction Sp.
Accordingly, according to the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship of the above-mentioned second embodiment, the struts 25R, 26R, 25L and 26L of the shaft brackets 13R and 13L have a blade-shaped cross-sectional shape, and the flows FR1 and FL1 from the outside in the vessel widthwise direction opposite to the rotational direction of the starboard propeller 10R and the port propeller 10L are provided in the upper sections of the starboard propeller 10R and the port propeller 10L rotating along the outer tracks R2 and R1 toward the center C in the vessel widthwise direction. Accordingly, a velocity in the rotational direction of the flows of the port propeller 10L and the starboard propeller 10R is relatively increased. As a result, the slip stream that passes the struts 25R, 26R, 25L and 26L of the shaft brackets 13R and 13L can be efficiently recovered by the starboard propeller 10R and the port propeller 10L, and the propulsion performance can be improved.
In addition, according to the propulsion device for the twin-screw vessel 1, like the first embodiment, since the starboard propeller 10R and the port propeller 10L are disposed in the vicinity of the center C in the vessel widthwise direction, the longitudinal vortex in the vicinity of the center C in the vessel widthwise direction can be efficiently recovered, and the propulsion performance can be improved. In addition, the starboard propeller 10R and the port propeller 10L do not interfere with each other like the interlock propeller type. Accordingly, the twin-screw vessel 1 can be easily manufactured. Then, since the starboard propeller 10R and the port propeller 10L are disposed in parallel, in comparison with the OLP type, risks such as an excessive bearing force in the rear-side propeller, expansion of a cavitation range, erosion, can be largely suppressed.
In this way, according to the twin-screw vessel 1, the propulsion performance can be improved while suppressing cavitation, erosion, or the like.
As shown in
Next, a third embodiment of the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship according to the present invention will be described. Since the third embodiment to be described below is different from the second embodiment only in the configurations of the shaft brackets 13R and 13L, the same components as the second embodiment are designated by the same reference numerals, and overlapping description thereof will be omitted.
As shown in
The starboard propeller shaft 12R and the port propeller shaft 12L are rotatably supported by the shaft brackets 13R and 13L in front of the starboard propeller 10R and the port propeller 10L. In the embodiment, the tubular support sections 14R and 14L of the shaft brackets 13R and 13L include one or more (in the embodiment, four) fins 45 extending in a radial direction and formed at outer circumferential sections of lower sections thereof.
The fins 45 have a blade-shaped cross-sectional shape perpendicular to a direction extending from the tubular support sections 14R and 14L toward the outer circumference. Further, the fins 45 are formed to provide flows in an opposite direction of the rotational direction of the starboard propeller 10R and the port propeller 10L in the lower sections of the starboard propeller 10R and the port propeller 10L. That is, the starboard propeller 10R and the port propeller 10L are rotated from the outside toward the center C in the vessel widthwise direction under the starboard propeller 10R and the port propeller 10L. Here, the fins 45 are formed to generate flows FR2 and FL2 from the center C in the vessel widthwise direction outward in the vessel widthwise direction under the starboard propeller 10R and the port propeller 10L. Specifically, the fins 45 are formed to be inclined from a front edge section 45f toward a rear edge section 45r and to gradually go away from the center C in the vessel widthwise direction outward in the vessel widthwise direction under the starboard propeller 10R and the port propeller 10L.
Accordingly, according to the propulsion device for the proximity twin-screw vessel having the shaft bracket and the ship of the above-mentioned third embodiment, the fins 45 installed at the shaft brackets 13R and 13L have a blade-shaped cross-sectional shape, and the flows FR2 and FL2 having a vortex shape from the center C in the vessel widthwise direction in an opposite direction of the rotational direction of the starboard propeller 10R and the port propeller 10L outward in the vessel widthwise direction can be provided in the lower sections of the starboard propeller 10R and the port propeller 10L. Accordingly, a velocity in the rotational direction of the flows of the port propeller 10L and the starboard propeller 10R is relatively increased. As a result, the slip stream that passes the fins 45 of the shaft brackets 13R and 13L can be efficiently recovered by the starboard propeller 10R and the port propeller 10L, and the propulsion performance can be improved.
In addition, according to the propulsion device for the twin-screw vessel 1, like the first and second embodiments, since the starboard propeller 10R and the port propeller 10L are disposed to approach the vicinity of the center C in the vessel widthwise direction, the longitudinal vortex in the vicinity of the center C in the vessel widthwise direction can be efficiently recovered, and the propulsion performance can be improved. In addition, the starboard propeller 10R and the port propeller 10L do not interfere with each other like the interlock propeller type. Accordingly, the twin-screw vessel 1 can be easily manufactured. Then, since the starboard propeller 10R and the port propeller 10L are disposed in parallel, in comparison with the OLP type, risks such as an excessive bearing force in the rear-side propeller, expansion of a cavitation range, erosion, can be largely suppressed.
in this way, according to the twin-screw vessel 1, the propulsion performance can be improved while suppressing cavitation, erosion, or the like.
Further, in the third embodiment, while the same struts 25R, 26R, 25L and 26L as in the second embodiment are provided, the embodiment is not limited thereto but the same struts 15R, 16R, 15L and 16L as in the first embodiment may be provided.
Further, the present invention is not limited to the above-mentioned embodiments but various modifications may be added to the above-mentioned embodiments without departing from the scope of the present invention. That is, the specific shapes, configurations, and so on, are exemplarily mentioned in the embodiments and may be appropriately modified.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-233258 | Nov 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/053372 | 2/6/2015 | WO | 00 |
