Marine propulsion – Screw propeller – Having means to control flow around propeller
Reexamination Certificate
2002-06-20
2004-01-27
Avila, Stephen (Department: 3617)
Marine propulsion
Screw propeller
Having means to control flow around propeller
Reexamination Certificate
active
06682377
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a propulsion apparatus for a vessel which comprises a main screw and a POD propeller, and in particular comprises a push type POD propeller.
2. Description of the Related Art
Recently, in a propulsion apparatus for a vessel, installation of a POD propeller rearward of a main screw has been proposed in order to add a further propulsive force when the propulsive force generated by the main screw is insufficient.
FIG. 5
shows a conventionally proposed example of a propulsion apparatus for a vessel. In
FIG. 5
, reference numeral
1
denotes a rear portion of the bottom of the vessel, reference numeral
2
denotes a main screw for generating a main propulsive force for moving the vessel, and reference numeral
10
denotes a push type POD propeller. The main screw is provided so as to rotate by a driving force generated by an engine such as a diesel engine (not shown).
The push type POD propeller
10
used in the above propulsion apparatus is composed of a casing
11
, a POD screw
12
, a strut
13
, and a supporting rod
14
.
The casing
11
is formed in a cylindrical shape and the POD screw
12
is provided rearward thereof. The POD screw
12
generates a propulsive force by rotating, and an electric motor (not shown) for driving the POD screw
12
is provided in the casing
11
.
The strut
13
has a wing-shaped section and is provided on the upper side of the casing
11
, and the supporting rod
14
which acts as a rotational axis of the POD propeller
10
stands upright from the upper end of the strut
13
. The supporting rod
14
is connected to a driving mechanism in a hull (not shown), and as a result, the POD propeller
10
is rotatably installed on the rear portion of the bottom of the vessel
1
through the supporting rod
14
.
The vessel having the propulsion apparatus for a vessel is moved by the propulsive force obtained by only rotating the main screw
2
or the POD screw
12
, or rotating both the main screw
2
and the POD screw
12
. Furthermore, when turning the POD propeller
10
around the supporting rod
14
, the strut
13
functions as a rudder and a steering force is generated, and as a result; the vessel can be turned.
However, in the conventional propulsion apparatus for a vessel, since the POD propeller
10
is provided rearward of the main screw
2
, the propulsive force obtained by the main screw
2
is reduced by the effect of a vortex (hereinafter called “hub vortex”) generated on a front end portion of the casing
11
by the main screw
2
itself, and the propulsion efficiency of the main screw
2
is decreased.
Furthermore, when the vessel is moved, a rotating flow remains in a slipstream of the main screw
2
. This means that the energy given to the main screw
2
is partly consumed as energy for generating the rotating flow, and a problem occurs in that the propulsion energy of the main screw
2
is decreased.
The present invention is provided in consideration of the above circumstances, and an object of the present invention is to improve the propulsion efficiency of the propulsion apparatus for a vessel by reducing the hub vortex or by utilizing the energy for the rotating flow generated by the main screw.
SUMMARY OF THE INVENTION
In the present invention, the following features are provided in order to solve the above problems.
A first aspect of the propulsion apparatus for a vessel of the present invention comprises a main screw and a push type POD propeller which is provided rearward of the main screw a. A plurality of grooves, which extend along the flow directions of a hub vortex generated by the main screw, are provided on a front end portion of a casing of the POD propeller.
According to the propulsion apparatus for a vessel having the above-described features, the hub vortex generated by the main screw rearward of the main screw is weakened by diffusing the hub vortex along the grooves which are provided on the front end portion of the casing of the POD propeller. Therefore, the propulsion efficiency of the propulsion apparatus for a vessel is improved.
A second aspect of the propulsion apparatus for a vessel of the present invention comprises a main screw and a push type POD propeller which is provided rearward of the main screw, wherein a plurality of stator fins are provided on a front end portion of a casing of the POD propeller.
According to the propulsion apparatus for a vessel having the above-described features, the rotating flow generated by the main screw rearward of the main screw is converted to a propulsive force by the stator fins which are provided on the front end portion of the casing of the POD propeller. Therefore, the propulsion efficiency of the propulsion apparatus for a vessel is improved.
A third aspect of the propulsion apparatus for a vessel of the present invention comprises a main screw and a push type POD propeller which is provided rearward of the main screw, wherein the main screw and POD propeller have the same axes, and a hub portion of the main screw and a front end portion of the POD propeller form a continuous rough spindle shape.
According to the propulsion apparatus for a vessel, having the above-described features, the rotating flow generated by the main screw rearward of the main screw is removed to the outside along the surfaces of the hub portion of the main screw and the front end portion of the POD propeller which form the continuous rough spindle shape. Therefore, the generation of a hub vortex is prevented, and the propulsion efficiency of the propulsion apparatus for a vessel is improved.
A fourth aspect of the propulsion apparatus for a vessel of the present invention comprises a main screw and a push type POD propeller which is provided rearward of the main screw, wherein at least a pair of fins having wing-shaped sections are provided on both sides of a casing of the POD propeller.
According to the propulsion apparatus for a vessel having the above-described features, the rotating flow generated by the main screw rearward of the main screw is converted to a propulsive force by the fins which are provided on both sides of the casing of the POD propeller. Therefore, the propulsion efficiency of the propulsion apparatus for a vessel is improved.
In this case, it is preferable that a leading edge portion of each fin be twisted along the direction of the water flow which is generated by the main screw.
REFERENCES:
patent: 4470364 (1984-09-01), Kitaura et al.
patent: 5505642 (1996-04-01), Theophanides
patent: 4-212695 (1992-04-01), None
patent: 6-56082 (1994-06-01), None
patent: 9-240586 (1997-09-01), None
Hoshino Tetsuji
Ishikawa Satoru
Sakamoto Toshinobu
Avila Stephen
Mitsubishi Heavy Industries Ltd.
LandOfFree
Propulsion apparatus for a vessel does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Propulsion apparatus for a vessel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Propulsion apparatus for a vessel will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3233154