JPS59106398A - Method of improving propulsive performance by donut-shaped wake distribution and fin shape therefor - Google Patents

Abstract

PURPOSE:To increase the wake coefficient of water flow guided to a propeller by arranging a laminar hindrance body that increases the friction between the water flow and hull surface on the hull surface of the upperstream area of the propeller in the stern shape of a low speed swollen ship such as a tanker. CONSTITUTION:An annular type fin 5 is provided at the position that is adjacent to a propeller 6 and at the upperstrem side position of the propeller 6 in the bottoms of a ship such as a tanker. For this annular type fin 5, suppose that the radius of gyration of the propeller 6 is R and the diameter of the propeller 6 is DP, the radius of the fin is set to approximately 0.7-0.9R or desirably to 0.8R and the horizontal distance d between the propeller 6 and fin 5 is set to 0.5- 2.0DP. In addition, when a bilge eddy is especially large, a blade fin 10 is provided additionally along a potential streamline 9. As a result, wake coefficient is increased and the distribution of the wake coefficient of the water flow guided to the propeller 6 can be uniformalized and propulsive performance is improved.

Description

[Detailed Description of the Invention] The present invention relates to means for reducing propeller excitation force and improving propulsion performance by improving the wake distribution regarding the stern shape of a so-called low-speed enlarged ship. .

As shown in Figure 1, in low-speed, enlarged ships such as tankers, bulk carriers, and membrane cargo ships, a bilge vortex (2) is generated at the stern (1) and the wake becomes uneven. When examining the wake distribution on the propeller rotation plane, as shown in Fig. 2 on the symmetrical port side, a hill-like distribution (3) of the wake appears due to the influence of the bilge vortex.

When the ship speed is VB and the speed of water flowing into the propeller is Va, the wake coefficient ω is expressed by the following formula.The wake coefficient is large near the eye above,
In other words, the phenomenon is that the propeller inflow speed is small.

If a propeller operates in such a wharf, the fluid force acting on the propeller blades becomes unsteady, resulting in propeller cavitation or a large propeller excitation force, which may affect the safety of the ship and the crew environment. There is a need for a solution to this problem.

It is no secret that the stern shape, including the frame line shape, was improved at the basic design stage in order to solve this problem, but on the other hand, it is possible to improve the stern shape, including the frame line shape, by attaching an appendix to the stern of the conventional shape. The measures to solve the above-mentioned problems by improving flow distribution can be applied to conventional ships and can be said to be extremely practical.

The inventors of the present invention proposed a patent application filed in 1986-1958 as a practical device that could improve the wake distribution and improve the propulsion performance, and did not require a complicated structure due to its large width.
No. 80 and Japanese Patent Application No. 57-162591 disclosed two inventions. The former is a means to improve the propulsion performance of the propeller and reduce hull vibration by increasing and uniformizing the wake flowing into the propeller, thereby creating a ship with a remarkable energy saving effect. The wake coefficient of the water flow introduced into the propeller can be increased by arranging a laminar flow obstacle that increases the friction between the water flow and the hull surface on the hull surface in the upstream area of the propeller. The technical idea is to configure the stern section so that the distribution of vortices is uniform.The latter also aims to control the stern vortices without depending on the shape of the frame line, and the latter aims to control the stern vortices without depending on the shape of the frame line. In order to introduce it into the propeller rotating surface area in the optimum state to obtain it, a fin is provided inside the stern boundary layer of the hull to absorb the potential streamline, and it eliminates the stern longitudinal vortex or makes it extremely weak, thereby reducing the separation line. It was also an invention that eliminated attached lines.

It has been confirmed through water tank tests on single-shaft and twin-shaft ships that both are extremely effective in simultaneously satisfying the intended objectives of improving wake distribution and improving propulsion performance. It was done.

Therefore, for ships that have problems with propeller excitation force, by adding the laminar flow impediment or stern fin, or a combination thereof, as shown in the above two inventions, propeller excitation force can be improved while improving propulsion performance. For the latter stern fin, the bilge vortex is reduced and the propulsion performance is improved, but on the other hand, the 8th fin
As shown in the figure (the starboard side is omitted due to symmetry), a fin wake part (4) appears in the wake distribution, which hinders the uniformity of the wake distribution, and the excitation force decreases compared to the mother ship type. There were times when it was difficult.

The present invention was made in consideration of the current situation, and aims to provide a means for obtaining a wake distribution that combines the effects of the laminar flow obstruction body and the effect of the stern fin of the above invention, and furthermore, The ultimate objective is to provide a stern appendix that can generate wakes exhibiting such behavior.

Hereinafter, one example of implementation of the present invention will be described based on the drawings.

As shown in Figure 4, if we look at the movement of water at a certain passing point The combination of the start speed (II), and the
Since the propeller generates the largest thrust in the donut-shaped region of 0.7R to 0.9H, where R is the radius, the diagram of the propeller kick-off speed is thought to have a shape like (If).

Therefore, as shown in Figure 5, the wake (1) caused by the ship's hull is
If we assume that the wake distribution (■)' has a shape that matches the above-mentioned propeller shedding speed (I[), then (IY and (
II) and the wake (g) are significantly smaller, offsetting each other.
The loss of momentum energy at the end of the jet will be much smaller, and the number of horsepower required for propulsion will naturally be reduced.In other words, such a wake is a donut-shaped 4u equivalent to the maximum thrust area of the propeller. This is caused by the wake distribution (I)'.

As seen in conventional ducted propellers and their improved examples, the fins used to obtain such a doughnut-shaped wake distribution improve the propulsion performance by the rectifying effect of the duct and the thrust generated by the duct, and improve the propulsion performance from the propeller rotation circle. Unlike the prior art, which has a duct with a slightly larger diameter, the wake of the fin can be used as a wake and this can reach the part of the propeller that generates the largest thrust. Therefore, it is better to have a ring shape, a shape close to it, or a part thereof, and a diameter smaller than the propeller rotation circle.

That is, as shown in FIG. 6 or FIGS. 7(a) and 7(b), the radius of the annular fin (5) is 0.8R out of approximately 0.7 to 0.9R, which produces a wake that satisfies the above requirements. (R is the radius of the propeller rotation circle) The propeller (6
) and the horizontal distance (d) from 0.5Dp to 2. It is preferably about ODp (Dp is the diameter of the propeller (6)), and the position on the hull is around 8.8.V2.

The annular fin obtained as the method of the present invention and its embodiment has the above-mentioned configuration, and the effects of the fin of the present invention are as follows: .7~0.9R1 This can increase the wake especially around 0.8R. (b) Due to the speed increasing effect of the fins, the propeller's 0.7R
Within the area and outside the propeller rotation circle, the wake is small υ,
These areas are where the thrust of the propeller is small, so there is little need to create a wake. (c) The fins prevent the descent of the critical streamline and their own rectifying effect reduces bilge vortices. These effects were clearly recognized, and as a result, the wake distribution was made uniform in the circumferential direction, and the propulsion performance was improved, making it possible to achieve a comprehensive performance improvement.

In the annular fin according to the present invention, it is thought that it is better to make the cross section of the annular part essentially into a wing surface shape in order to cope with the fluid, but even if a flat plate is simply curved to form an annular shape, it will create a donut-shaped fin. It is an advantage of the present invention that such a structure can be achieved, which is well suited for the purpose of increasing the flow, and which presents fewer problems in terms of workmanship and construction.

In addition, when it is necessary to control the fin wake due to factors such as propeller rotation speed or stern shape, and when equipped with a fin blade,
It is possible to take measures such as protruding radially inwardly or outwardly from the annular fin, or disposing the fin internally to also serve as a support, and such a configuration can produce a reaction effect. Furthermore, as another example, if the bilge vortex is particularly large, the potential streamline (9) shown in FIG.
If the sibylge vortex is reduced by combining with the blade fins attached to the blade fins, the desired flow rectification can be achieved in the trailing stream by the annular fins (5). Although the annular fins have the effect of rectifying the bilge vortex and concentrating the wake at the part where the propeller produces the most thrust, if it also has the effect of increasing the wake by adding to the wake, it is difficult to propel. Efficiency can be greatly increased.

The present invention can be applied not only to single-shaft ships but also to multi-shaft ships such as twin-shaft ships. Figure 8 shows an example of an annular fin (5) attached to a two-shaft ship, which was said to have poor propulsion efficiency due to the lack of wake at the propeller position and low wake gain, to support the propeller shaft. It is provided so as to surround the bossing (6) part, and a laminar flow impediment (b) is provided on its outer surface.
is installed.

As explained above, the means of the present invention significantly improves propulsion performance despite being simple in construction, and as long as the gist is followed, the technical idea is not limited to the above-mentioned embodiments. Needless to say, all diversions, applications, and modifications derived from these are included within the technical scope of the present invention.

[Brief explanation of drawings]

Figure 1 is a state diagram of the bilge vortex of a conventional ship type, Figure 2 is a wake distribution diagram for the case of Figure 1, Figure 8 is a wake distribution diagram of a ship with a stern fin, and Figure 4 is a diagram of the wake distribution of a ship with a stern fin. FIG. 5 is a diagram showing the movement of water during navigation; FIG. 5 is a diagram showing the movement of wake obtained by the method of the present invention; FIG. 6 is a diagram showing one embodiment of the present invention; FIG. (
a) is a view from the stern of the embodiment shown in FIG. 6, and (b) is a view of the embodiment shown in FIG.
FIG. 8 is a perspective view showing an example in which an annular fin provided with a laminar flow obstruction is applied to a two-shaft ship. (1) Stern (2) Bilge vortex (3) Hill-like distribution (4) Fin wake (5) Annular fin (6)
・Propeller (7)...Propeller shaft (8)・
... Propeller rotation circle (9) ... Potential flow, vs
(10...Blade fin Figure 1 Figure 1 Figure 21' Figure 4 shows Iπ III Figure 5

Claims (1)

[Claims] 1. By rectifying the bilge vortices that tend to occur in low-speed enlarged ships into a stern flow that shows a donut-shaped wake distribution, the wake corresponds to the donut-shaped annular region where the thrust generated by the propeller is the largest. A method for improving propulsion performance using a doughnut-shaped wake distribution, characterized in that the propulsion efficiency is improved by increasing the wake distribution and causing water flow with such a wake distribution to flow into a propeller. 2. It has a radius of approximately 0.7 to 0.9 times the propeller radius and an appropriate length along the length of the ship, and is substantially formed in an annular shape that shares the axis with the propeller rotation axis. , the horizontal distance between the rear end and the propeller is 0.
A fin shape that produces a donut-shaped wake distribution characterized by a structure that is added to the stern in a range corresponding to 5 to 2.0 times.