JPS58199291A - Varying pressure shutoff construction for propeller for the purpose of prevention of vibration in the stern - Google Patents

Abstract

PURPOSE:To prevent vibration of stern by inserting a shutter plate between propeller and the hull surface at the stern and thereby preventing the varying pressure on the propeller from transmission directly to the hull surface. CONSTITUTION:A varying pressure shutter plate 2 is installed in the recess 9 formed at the stern, right over the propeller 1. This shutter plate 2 is mounted on the hull surface 6 with a lief spring 3, coil spring 4 and rod 5, being provided with elasticity so as to displace vertically. According to this arrangement, the varying pressure on the propeller 1 produced by rotating vanes 7 is caught by this shutter plate 2 and absorbed, so that no varying pressure will be transmitted to the hull surface 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Most ships have a screw propeller attached to the rear end of the ship, and this propeller is rotated by an engine installed inside the ship.

At that time, the propeller generates propulsive force to propel the ship. However, a screw propeller is composed of multiple blades and a boss that supports the blades at the center, but when such a propeller rotates, fluctuations occur in the surrounding water with a frequency mainly equal to the number of blades x the number of revolutions. Pressure is generated. Since the rear end of the hull and the propeller are located quite close to each other, the fluctuating pressure induced by the propeller is transmitted to the stern surface via the surrounding water, which is one of the major causes of stern vibration. A cavitation phenomenon called propeller cavitation appears on the blades of most ship propellers, with few exceptions. Under conditions where this phenomenon becomes severe, cavities develop and become larger, and propeller hull chimp vortex cavitation (string-like cavitation centered on a lightning-like flow system running between the propeller and the hull) often occurs. , generally PI (
(abbreviated as v) begins to occur, the fluctuating pressure becomes significantly larger, and the stern vibration increases accordingly5.
It has extremely negative effects on the comfort of mariners, the performance of navigational equipment, the performance of automated equipment, and the strength of ship structural materials.

One of the conventional studies that have been conducted to deal with the propeller fluctuation pressure that causes such adverse effects is to prevent the occurrence of large stern vibrations at the shipbuilding design stage. The following are countermeasures to be taken when the former occurs. The distance between the propeller and the hull, which is called the tip clearance, must be sufficiently large; the propeller design must be designed to reduce propeller fluctuation pressure; and the severe occurrence of propeller cavitation that increases propeller fluctuation pressure. In order to suppress this, the hull shape is suitable for this purpose and the flow that enters the propeller is adjusted, each of which has been effective to some extent either individually or in combination. In the latter case, propellers with different numbers of blades may be replaced, and in order to equalize the speed of the flow entering the propeller and suppress the occurrence of cavitation on a small scale, various types of rectifying plates called fins may be installed on the surface of the ship's stern hull. Various types of reinforcement may be applied to prevent vibrations in various parts, but these are symptomatic treatments and are rarely effective.

Thus, no effective means for preventing propeller pressure fluctuations has yet been found.

The present invention has a stern structure in which a baffle plate is installed between the propeller and the stern hull surface, and this stern structure allows the fluctuating pressure of the propeller, which is the main cause of stern vibration, to be applied directly to the hull surface. This is to prevent In other words, if the shingle plate is attached to the hull in a flexible and resilient manner so that it is separated from the hull in terms of strength, the fluctuating pressure will be transmitted to the shiyahei plate and then most of it will be absorbed by the shiyahei plate. be done. Furthermore, if the space between the hull and the shingle plate is filled with water or a filling material with high vibration-proofing properties, this water or vibration-proofing material will further inhibit the propagation of fluctuating pressure.

This invention will be explained based on the drawings. Figure 1 shows a propeller variable pressure shield structure that was adopted from the design stage of the ship for the purpose of preventing stern vibration, with a propeller variable pressure shield plate placed directly above the propeller l. As shown in Figure 2, this flexible plate includes a plate spring 3, a coil spring,
It is attached to the hull surface A using a rod J, but the important thing here is to give the stiffness plate elasticity so that it can move in the -F direction. In this way,
Since the fluctuating pressure generated by the rotation of the propeller blades 7 can be stopped and absorbed by the shield plate, it is possible to prevent the fluctuating pressure from being transmitted to the hull surface A. If this flexible structure is taken into consideration from the design stage, the upper four parts of the -7° lobera shown in Figure 1 can be placed, smoothing the flow at the stern, and there is no need to worry about increased resistance due to the adoption of this structure. .

As a countermeasure when a completed ship experiences severe stern vibrations, as shown in Figure 3, a variable pressure baffle plate can be installed from the hull surface above the propeller in the same manner as in Figure 1 to reduce stern vibrations. It can be significantly reduced.

The effect brought about by the present invention is first to prevent stern vibration, which is the original purpose, but furthermore, when considering the effectiveness of this fluctuating pressure structure, the degree of freedom in designing the stern is expanded. Even if the stern bottom is made completely flat, the usability of the flattened stern compartment can be increased without worrying about occurrence of stern vibration. Furthermore, in the past, from the viewpoint of fluctuating pressure, it was not possible to reduce the distance between the propeller and the bottom of the ship as shown in Figure 3, the tip clearance IO, below a certain limit, but by adopting the shielding structure of the present invention, this clearance can be reduced. Therefore, it becomes possible to expand the stern compartment volume. From the perspective of energy conservation, the use of low co-rotating, large-diameter propellers with high propulsion efficiency is being considered, but this reduces tip clearance and there are concerns about stern vibration due to large fluctuating pressures. However, the interference structure according to the present invention eliminates this concern and makes it possible to realize a highly efficient ship with reduced stern vibration.

V Explanation of the Drawings Figure 1 shows the propeller variable pressure shoring structure, which was adopted from the design stage of the ship to prevent stern vibration. The details of the mounting part are shown, and Figure 3 shows an example in which the hon-jahei structure is adopted as a countermeasure when a completed ship is subjected to severe stern vibration.

／・・・Propeller, ・・・・Propeller variable pressure blocking plate, 3・-1・Flat spring, gli coil spring・・・・・・・・・・・・Propeller variable pressure blocking plate, 3・-1・Leaf spring, gli coil spring ・・・・・・・・・・・Propeller, etc. ...Bone stern hull surface, 7...Propeller blade, t...Propeller boss, Ri...Four parts of the upper part of the propeller, IO...
・E-chitsubu clearance procedure amendment document Showa! Director General of the Japan Patent Office, June 3, 2006, Mr. l. Case description: 1981 Patent Application No. 0913j 2 Title of the invention: Propeller variable pressure structure for preventing stern vibration 3 Relationship with the amended person's case: Patent application Address: Shinkawa-chome 3g, Mitaka-shi, Tokyo No./No. V Date of procedural amendment order: Showa! Year 831, year r Drawings subject to amendment

Claims (1)

[Claims] 1. Propeller fluctuating pressure shield structure adopted from the ship design stage to prevent stern vibrations 2. Propeller fluctuating pressure shield structure adopted as a countermeasure when a completed ship experiences severe stern vibrations