JPS6250357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a propeller device used in a high-speed boat.

Conventionally, ships operated at speeds of up to 30 kt usually use screw propellers with a wing-shaped or arc-shaped cross section, but when speeds exceed about 40 kt, cavitation occurs and efficiency is significantly reduced. This can lead to deterioration or damage to the propeller due to erosion, so as a means to prevent this, research has been conducted on supercavitation propellers, water jets, surf propellers, etc., and some of them have been put into practical use.

However, supercavitation propellers are inefficient at low to medium speeds and have the disadvantage of causing erosion at transition speeds (30 to 40kt) where cavitation begins to occur. In addition, improvements have been made to water jets in recent years, such as installing an inducer in front of the impeller to increase the water pressure and increase the speed at which cavitation occurs, but the efficiency is only about 60% at most. Also, cavitation becomes a problem at speeds over 50 kt.

In contrast, the so-called surf-s propeller, which rotates with the upper part of the propeller exposed above the water surface, has a "GAWN" that does not cause cavitation.
However, the thrust and torque per unit area of the propeller are small, and this tendency becomes more pronounced as the speed decreases, so when the speed is near zero, the propeller There is a risk that the propeller will spin and not reach the planned speed, and the propeller will intermittently hit the water surface, resulting in large fluctuations in thrust and torque.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional propeller system, and to provide a propeller device that is efficient at high speeds and operates well without causing side effects.

The present invention was made based on the fact that the back surface of the Surf S propeller sucks air from above the water surface and forms a cavity filled with air in contact with the back surface, so it is hardly affected by cavitation. The feature is that in order to open the rear of the propeller to the atmosphere in the forward state and make it easier for the back of the propeller to suck in air, a duct or channel is installed in the front of the propeller to apply water to almost the entire propeller. It is installed on the ship's hull, and the propeller's wake is released into the atmosphere above the water surface.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows the rear of a personal watercraft sailing to the left. Water is guided into a duct 3 from a water intake 2 protruding downward from the bottom 1, and a bearing fitting 4 is connected to the outlet at the rear end. A supported propeller 5 is provided. 6 is a propeller drive shaft. The inner surface of the duct 3 is brought close to the outer periphery of the propeller 5. V of the above structure
When a high-speed boat or the like is planing, the rear water surface 7 becomes lower than the propeller 5 at the stern, completely exposing the rear part of the propeller 5 to the atmosphere. As a result, the propeller 5 rotates in the water flow discharged from the duct 3 and having a free surface around it, and air is attracted from the free surface to the tip of the propeller, and as shown in FIG. (shown in cross section) back side 5
Since air is sucked into a to form a cavity 8, it has exactly the same properties as a Surf S propeller. It is a well-known fact that a propeller rotating close to a free surface often attracts air. At the same time, the water in the duct 3 hits the entire front surface of the propeller 5, so the thrust and torque are doubled compared to the Surf S propeller, and they do not fluctuate. Furthermore, while the cavity in a normal supercavitation state has a water vapor pressure close to a vacuum, the pressure in the cavity 8 is close to atmospheric pressure, so the impact pressure caused by this and the accompanying erosion occur. etc., and does not cause cavitation damage.

The water intake 2 in the above embodiment is of a ram type that protrudes below the bottom of the ship, but the embodiment shown in FIG. If the lower part of the wall is made into a convex surface with a small curvature and smoothly connected to the bottom of the ship, the duct 3a and propeller 5 are submerged in water when the ship is stationary, but when the ship is moving forward, the stern rises as the speed increases and water is efficiently drained due to the Coander effect. It is attracted into the duct 3a. In this embodiment as well, the inner surface of the duct 3a is close to the outer circumference of the propeller. In this embodiment, the propeller 5 is installed outside the rear end of the duct 3a, and is rotated via a gear box in a boss 9 by a drive shaft 6a passing through a bearing fitting 4a. The propeller 5 may be provided so that a portion thereof enters the duct 3a.

Another embodiment shown in FIGS. 3a and 3b is a channel in which the bottom of the stern is recessed so that the rear end 10 is approximately semicircular so that the upper half of the water flow that hits the propeller becomes a free water surface near the tip of the propeller. 3b, and the coander effect due to the inner surface shape of the waterway is similar to that of the embodiment shown in FIG. Air is attracted to the back of the propeller, similar to the Surf S propeller. In this embodiment, a gear box 9b, a bearing fitting 4b, etc. that support the propeller 5 are provided behind the propeller 5, and the drive shaft 6b is guided from outside the ship into the inside of the ship.
In this way, since there is no structure in front of the propeller 5, propeller performance can be improved.

In another embodiment shown in FIGS. 4a and 4b, the bottom 1 extends horizontally to the rear end of the ship, and the rear bottom 1c has a molded member 1 with an open bottom and a semicircular shape at the rear.
1 is fixed and molds the rear water surface during high-speed skiing.
The propeller 5 is lowered as shown by the broken line by the lower slope 11a of the propeller 5, thereby exposing the upper half of the propeller 5 to the atmosphere to obtain the same effect as in FIG. This structure has the advantage of being able to be used as is on existing watercraft, and has an extremely wide range of applications.

Next, the blade shape of the propeller used in the present invention will be explained.

Figure 6a shows an airfoil type airfoil, which is the same as an airplane's airfoil, and is the airfoil type most commonly used for medium- and low-speed ships because of its high efficiency. Type b is an arcuate airfoil with the upper and lower surfaces forming arcs, and although its performance at medium and low speeds is inferior to the Aerofoil type, it is easier to manufacture and its cavitation is superior to the Aerofoil type, and is used in leisure boats and special high-speed boats.

Figure 6c, d, and e are airfoils used in the supercavitation area (hereinafter referred to as SC airfoils).
, c is a planar SC wing with a flat bottom surface, and d is Tulin
-Burkart wing, e is a typical airfoil shape of a 5-term wing. In addition, although not shown in the figure, there is also a type of wing called a trinomial wing, in which the lower surface of the wing is similar to the Tulin-Burkart wing.
It has a shape intermediate between that of the nuchal wing e. These Tulin
-Burkart blades, 3-term blades, and 5-term blades are known as high-performance blades and are used as high-speed hydrofoil blades and SC propellers. In contrast, the plane SC
Although the wings are said to have poor performance, arcuate wings and flat SC
In experimental results using a Tulin-Burkart wing propeller as a surf-s propeller, Tulin-
There are reports that Burkart blades have an efficiency of 70-75%, and flat SC blades have similar performance, while arc-shaped blades have an efficiency of only 60-65%. However, any of these airfoil type propellers can be used in the present invention. Incidentally, in order to improve ventilation on the back surface of the propeller, a bent oil type propeller as shown in FIG.

In addition, as mentioned above, in order to prevent the spinning phenomenon of the Surf-S propeller near zero speed, the propeller is installed in a position where it is submerged in water when it is stationary, and the shape of the rear exit of the waterway is designed so that the rear surface of the propeller is exposed to the atmosphere when it is sliding. The problem can be solved by selecting

The present invention has the above configuration, and prevents the occurrence of cavitation by opening the rear of the propeller to the atmosphere and applying water to the front of the propeller.
Moreover, it is highly efficient, with no fluctuations in thrust or torque,
It has excellent effects such as being able to operate stably at any speed, and the structure is extremely simple and easy to manufacture.As for the blade shape of the propeller used, existing hydrofoils and SC propeller materials can be used as is, so it can be used immediately. It has the advantage of being possible to implement.

[Brief explanation of the drawing]

1, 2, 3a, and 4a are partially sectional elevational views showing different embodiments of the present invention, and FIGS. 3b and 4b are respectively 3a and 4b. Figure 4a
FIG. 5 is a diagram illustrating the generation of cavities on the back surface of the propeller in the present invention, and FIGS. 6 a to 6 g are sectional views of various propeller airfoils that can be used in the present invention. 3, 3a...Duct, 3b...Waterway, 5...Propeller.

Claims (1)

[Claims] 1 At the rear bottom of the hull, when moving forward, water was sucked in an amount that hit almost the entire propeller exposed above the water surface, and was released into the open atmosphere above the water surface at the rear of the hull, so that the inner surface was close to the outer periphery of the propeller. A vented type characterized in that a duct or waterway is provided, the lower upper wall of the duct or waterway is a convex surface with a small curvature and smoothly connected to the bottom surface of the ship, and a propeller is operated in the water flow at the outlet of the duct or waterway. Propeller device.