JPH1081299A - Marine rotary thruster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any damage to propeller due to cavitation being liable to occur on the propeller upper side offsetting a propeller center downward in relation to a duct center, and enlarging a clearance with a duct inner surface in the propeller upper position, in a propeller rotating surface. SOLUTION: A duct 1 surrounding a propeller 2 is formed into a blade section and therefore a thrust is produced on sail. Since there is a strut 4 in front of this duct 1, such a part as being slow in flow velocity is produced at the rearward, and cavitation is apt to occur on a duct upper inner surface and a propeller backside. Accordingly, the propeller 2 is designed so as to be installed by means of offsetting a propeller center O2 downward as far as Δin relation to a duct center O1 on a propeller rotating surface. Therefore, such a clearance different in the upper and lower sides is produced in space between the duct inner surface and a rotational locus at the propeller tip. In brief, since a large clearance δ+Δ is formed in the duct upper part, a possibility of damage to the propeller 2 due to cavitation is lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a revolving thruster for ships, which is mounted on a ship and controls propulsion and steering.

[0002]

2. Description of the Related Art As shown in FIG.
Is widely used mainly for tugboats B because high thrust and thrust direction can be changed by 360 ° within a plane. This swiveling thruster T includes a duct 1, a propeller 2, a pod 3,
The strut 4 includes a power transmission mechanism 5 and a turning mechanism 6 (see FIG. 2). As shown in FIG.
When the difference between a and the propeller outer diameter 2a is 2δ, the center of the duct and the center of the propeller are adjusted so that the gap δ between the duct 1 and the tip of the propeller 2 becomes as uniform as possible over the entire circumference of the duct 1 in the propeller rotation plane. The propellers 2 are arranged in the duct 1 so as to coincide with each other (the common center O). This is because the center O is adjusted to be axially symmetric to eliminate problems in performance, vibration, and the like. This type of prior art includes "THE ROYAL
INSTITUTIONOF NAVAL ARCHITECTS 1973 (p. 30).

[0003]

However, in general, there is a strut that supports a propeller and a duct and has a built-in power transmission shaft to the propeller, just above the propeller.
Inhibiting seawater inflow. Further, since the seawater static pressure is small at the upper part of the propeller (duct) and the thruster mounting position is at the bottom of the ship, turbulent flow enters due to the influence of the hull at the upper part of the propeller, so that cavitation is likely to occur in the propeller. To explain this point in FIG. 4 (a) (b), (a) the blade section of a propeller lower position, (b) shows a blade section of a propeller upper position, Vr _1, Vr ₂ is the propeller rotational speed , Va ₁ , Va ₂ are the seawater inflow rates to the propeller, w ₁ , w ₂
Is the relative velocity on the blade section, and α ₁ and α ₂ are the attack angles. When the propeller rotates upward and Va ₂ becomes larger than Va ₁ , cavitation tends to occur on the rear side of the propeller. In addition, since the cavity collapses on the inner surface of the duct, the upper portion of the inner surface of the duct is susceptible to cavitation damage.

[0004] For this reason, it is conceivable to increase the inner diameter of the duct to increase the distance from the cavity or to consider the attenuation due to air blowing.
Issues remain in terms of weight and cost.

[0005] In addition, the propeller may be damaged due to the entrainment of the floating material. However, in the case of the variable pitch propeller, each of the blades cannot be removed unless the duct is removed (as shown in FIG. 2). The propeller root is fitted in the boss), which makes it difficult to speed up the replacement operation and save labor.

[0006]

According to the present invention, the propeller center is offset downward with respect to the duct center on the propeller rotating surface of the swiveling thruster to increase the gap between the propeller upper position and the duct inner surface. Prevents cavitation damage to propellers.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As an embodiment of a marine revolving thruster according to the present invention, a propeller center is offset downward with respect to a duct center on a propeller rotating surface of the revolving thruster. Eventually, the gap with the tip of the propeller (rotation locus) is large at the upper part of the duct and smaller at the lower part of the duct, but it is possible to suppress the damage due to cavitation at the upper part of the propeller without affecting the performance.

In this case, the offset amount Δ of the propeller center with respect to the duct center is 0 <Δ <δ, where the difference between the duct inner diameter and the propeller outer diameter is 2δ. Since the average gap on the inner circumference of the duct is the same as the conventional one, there is no inferior performance. Here, δ is a value when the gap between the inner peripheral surface of the duct and the trail of the propeller tip is uniform on the circumference.

Further, in the above configuration, even when the propeller of the revolving thruster is a variable pitch propeller, the propeller can be removed and replaced without removing the duct as in the case of the fixed pitch propeller. .

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a rotary thruster according to an embodiment of the present invention. FIG. 1 is a side view of the swivel thruster T of the present application provided on a tugboat B, FIG. 2 is an enlarged side sectional view of the swivel thruster T, and FIG.
(a) and (b) are a side view and a front view of a swiveling thruster T showing a positional relationship between the duct 1 and the propeller 2.

As shown in these figures, a turning thruster T projects downward from the bottom of a tugboat B, which is an example of an equipped ship, and controls the propulsion and steering of the ship. A strut 4 extends downward from a base 7 which is seated on a hull at the bottom of the hull. A pod 3 having a propeller shaft 8 and the like is provided below the strut 4, and a propeller 2 is mounted on one end of the pod 3. A duct 1 is provided so as to surround the propeller 2. The power of the main engine is controlled by a drive shaft 9 connected to the main engine.
And transmitted to the propeller 2 via the power transmission mechanism 5 of the upper bevel gear 10, the vertical shaft 11, the lower bevel gear 12, and the propeller shaft 8. A turning mechanism 6 is provided on the upper part of the strut 4.
The entire pod 3 including the duct 1 and the propeller 2
The vehicle turns around the turning center C shown in FIG. 3A, thereby exerting a steering function.

The duct 1 surrounding the propeller 2 has a wing cross section, and generates thrust during navigation. Since the strut 4 is provided in front of the duct 1, a portion having a low flow velocity is generated behind the strut 4. As described above, cavitation is likely to occur on the inner surface of the upper part of the duct and on the rear side of the propeller, as described above.

[0013] Therefore, in the present application, so as to equip the propeller 2 is offset (offset amount delta) and the propeller center O ₂ downward with respect to the duct center O ₁ in the propeller rotation plane as shown in FIG. 5 (b) ing. Therefore, there is a vertically different gap between the inner circumferential surface 1a of the duct and the rotation locus 2a of the propeller tip. That is, a large gap is formed in the upper part and a small gap is formed in the lower part. Since a large gap is formed in the upper part of the duct where cavitation is likely to occur, the possibility of damage to the propeller 2 due to cavitation is reduced.

Now, the duct inner diameter 1a and the propeller outer diameter 2a
Is set to 2δ, Δ may be determined in the range of 0 <Δ <δ. Δ + Δ gap at the top of the duct, δ at the bottom
The gap is -Δ. δ is a value when a uniform gap is provided on the inner circumference of the duct. For example, if Δ = 0.5δ, the upper gap is 1.5δ and the lower gap is 0.5δ.

By adopting the concept of offsetting the center of the propeller with respect to the center of the duct as described above, a duct having the same diameter as the duct for the fixed pitch propeller can be used for the variable pitch propeller as it is, and a large gap at the top is utilized. To remove and replace the propeller. Further, since the average gap on the circumference of the duct 2 is δ, there is no adverse effect on the performance.

[0016]

As in the embodiment of the present application, if the center of the propeller is offset downward from the center of the duct, a large gap is formed between the propeller and the upper part of the duct where cavitation is likely to occur, so that damage to the propeller due to cavitation can be suppressed. Can be. Since the average clearance on the duct circumference is the same as the conventional one, there is no inferior performance.

Further, when replacing a propeller damaged by suspended matters or the like, even if the propeller is a variable pitch propeller, each blade can be removed and replaced without removing the duct, so that work efficiency and labor saving can be achieved. Can be.

Further, since it is only necessary to design and manufacture a duct having the same diameter as the duct for the fixed pitch propeller, it is possible to quickly respond to demand by manufacturing and stocking a single type of duct. It is possible to prevent confusion at the site at the time.

[Brief description of the drawings]

FIG. 1 is a side view of a tug boat equipped with a swiveling thruster of the present application.

FIG. 2 is an enlarged sectional side view of the swiveling thruster.

FIGS. 3 (a) and 3 (b) are a side view and a front view of a swiveling thruster, respectively, showing a positional relationship between a duct and a propeller.

FIGS. 4 (a) and 4 (b) are diagrams showing operating states of blades (propeller blades) when a propeller comes to an upper portion and a lower portion of a duct, respectively.

5 (a) and 5 (b) are schematic diagrams of a relative positional relationship between a conventional duct and a propeller of the present application, respectively.

[Explanation of symbols]

 T: Swivel thruster 1: Duct 1a: Duct inner diameter (inner circumferential surface of duct) 2: Propeller 2a: Propeller outer diameter (rotation locus of propeller tip) 3: Pod 4: Strut 5: Power transmission mechanism 6: Swivel mechanism

Claims (3)

[Claims] 1. A marine revolving thruster, characterized in that the propeller center is offset downward with respect to the duct center on the propeller rotation surface of the revolving thruster. 2. The offset amount Δ of the propeller center with respect to the duct center is defined as the difference between the duct inner diameter and the propeller outer diameter is 2δ.
2. The marine revolving thruster according to claim 1, wherein 0 <Δ <δ. 3. The marine turning thruster according to claim 1, wherein a propeller of the turning type thruster is a variable pitch propeller.