JPS6323959B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention allows the vortex generated by the catamaran and the propeller to interact effectively with each other in a catamaran stern boat, thereby improving propulsion efficiency and reducing fuel consumption. This relates to a means for doing so.

So-called stern catamarans, which have a normal hull shape at the bow and a twin hull at the stern, have significantly reduced vortex components, although the flooded area at the stern increases and friction with the water increases. However, the hull resistance is lower than that of normal single-shaft ships, which is a remarkable effect, and the twin-shaft propulsion unique to catamaran stern ships can achieve high propeller efficiency with a propeller of a not-so-large diameter, so cavitation, propeller It is possible to avoid various problems associated with single-shaft large-diameter propellers, such as hull vibration caused by ballast movement and air intake during ballast voyage, and the adoption of a two-engine, two-shaft, two-rudder system increases navigation safety and reliability, which is advantageous for energy saving issues. It has a unique hull shape.

On the other hand, even if the price of a single-shaft ship increases slightly, the length of the hull must be increased, that is, the L/B ratio must be increased to approximately 6 or more to reduce hull resistance and keep fuel consumption low. However, even in such long and slender ships, the propulsion efficiency remains at a low value, and even if an attempt is made to increase efficiency by increasing the diameter of the propeller at lower rotation speeds, the above-mentioned problems still occur. Therefore, it has not been possible to provide a fundamental solution.

Originally, the wider and thicker the catamaran stern becomes, the more advantageous it is over a single-shaft ship, but when such a catamaran stern is applied to a long and slender ship like the one mentioned above, the reduction in resistance is not so noticeable. However, it is very attractive that a significant increase in propulsion efficiency can result in a large energy saving effect, solve various problems such as cavitation, hull vibration, and air suction, and increase the safety and reliability of navigation. If a catamaran stern is applied to a long and slender ship, the catamarans will inevitably come close to each other, so this situation can be used to control the stern vortex that exists at the stern of a large ship and effectively guide it to the propeller. It is possible to further improve propulsion efficiency, and with this configuration, not only a two-engine, two-shaft system but also a single-engine, two-shaft system is possible, making it easy to adopt a long-stroke, low-speed engine with low fuel consumption. Together with this, it is possible to achieve a comprehensive energy saving effect.

The present invention was made based on such an idea,
The present invention will be described in detail below. When applying a catamaran stern to a long and slender hull, in principle each catamaran stern is brought close to each other to shorten the distance between the axes of the two propellers, and the shape of the catamaran is The propeller is formed to generate an internal vortex, which is a strong internal longitudinal vortex, and the propeller rotates outward to reduce the vortex component in the wake of the propeller and recover the energy lost by the vortex. By arranging a current plate (so-called center skeg) just before the ship, the outer flow and the bottom flow are easily merged, greatly improving propulsion efficiency (hull efficiency) and thereby significantly reducing fuel consumption. It can be used as a highly efficient means of propulsion in a catamaran stern boat that makes it possible to do this.

Next, an example of a specific implementation of the above-mentioned stern-shaped configuration will be described based on the drawings.

The stern twin-hulled parts 1, 1 are installed close to each other, and the distance between the propeller shafts 5, 5 of the twin-hulled parts is small, and this distance between the shafts is approximately 1.1 times the propeller diameter ( (preferably in the range of 1.0 to 1.1 times), and the outer rotation of each propeller 4, 4 is in the positive rotation direction during forward movement. In this state, the twin body parts 1, 1
Since the center bottom 2 between the two is narrow and deep, the center bottom 2 should have as little upward inclination toward the stern as possible. Propeller shaft 5 of twin body part 1
The angle θ between the so-called catamaran center plane 7 and the above-mentioned hull center plane 8 is approximately
The twin body parts are formed so that they intersect within the range of 45 to 90 degrees, and the shape is such that internal vortices are likely to occur around the twin body parts. Furthermore, the main hull is extended to provide a current plate 3 on the hull center plane 8 up to just before the propellers 4, 4.
Note that 6 indicates the rudder, and a single rudder or two rudder system is adopted.

By adopting this type of hull shape, (a) unlike normal twin-shaft ships, there is no addition to the hull such as bottoming or struts for supporting the propeller shaft, so separation of water flow from the outside to the propeller 4 occurs; (b) Each twin hull is shaped to project diagonally to the side from the center plane of the hull, and the outer flow S is The strong internal flow J reaches the propeller in this part, generating an internal vortex around the twin body, and the stream lines gather around the twin body, so the wake concentrates in this part, and these It effectively flows into the propeller. On the other hand, by using an external propeller, the internal vortex and the vortex generated by the propeller cancel each other out, and the propulsion efficiency (hull efficiency) is improved by reducing the vortex component in the wake of the propeller. (This effect is the same as that of a counter-rotating propeller or an asymmetric single-shaft stern.) (c) A rectifying plate (center skeg) 3 on the centerline of the hull.
By providing this, the outside flow from both sides and the bottom flow can be merged without difficulty and separation of water flows can be prevented, thereby producing the effects of (a) and (b), and at the same time improving maneuverability. By adopting the catamaran stern of the present invention even in long and slender vessels with L/B of 6 or more, fuel consumption can be reduced by 12 to 20% compared to ordinary single-shaft stern vessels. The technical idea of the present invention, which can significantly reduce operating costs without unnecessarily increasing construction costs, is not limited to the example of implementation described above, and any applications or diversions derived from these are not limited to the above embodiments. It goes without saying that all of these are included within the technical scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is an explanatory side view of essential parts in one embodiment of the present invention, and FIG. 2 is an explanatory front view of the port stern showing one specific example. 1... Twin hull, 2... Center bottom, 3... Current plate, 4... Propeller, 5... Propeller shaft, 6...
Rudder, 7... Center plane of catamaran, 8... Center plane of hull, J
...Strong inner flow, S...Outer flow.

Claims (1)

[Claims] 1. In a catamaran stern boat with a normal ship-shaped bow and a twin-hulled stern: The spacing between the stern twin-hulled sections is such that the axial distance of the propeller shafts of the twin-hulled sections is 1.1 times the diameter of each propeller. The stern twin hulls extend diagonally downward from the main hull, and the surfaces that pass through the axis of the propeller shafts of the twin hulls, extend in the longitudinal direction of the respective hulls, and slope toward the center plane of the hull, and the above-mentioned hull. The twin hull is formed so that the angle with the center plane intersects within the range of approximately 45 to 90 degrees; the slope of the center bottom toward the stern is gentle, and it extends just before the propeller on the center plane of the main hull. A shape with a center skeg as a rectifying plate; by making the outer flow reach the propeller as a strong inner flow, an internal vortex is generated in the twin body part, and at the same time streamlines are gathered around the twin body part and this part By concentrating the wake into the propeller and causing it to flow into the propeller; by making each propeller rotate around the outside, the internal vortex and the vortex generated by the propeller cancel each other out, reducing the vortex component in the wake of the propeller. A hull shape for obtaining high efficiency propulsion in a catamaran stern boat characterized by the following structure: