JPS604490A - Marine reverse skew propeller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a marine propeller, which has a skew angle in the opposite direction to that of conventional high skew propellers.

In a conventional high skew propeller, the skew angle is distributed so that the blade elements near the tip of the blade pass the wake peak later. In this case, when the volume y of the cavity generated in the blade element at each radial position is expressed with respect to the angular position θ of the blade, it becomes as shown in FIG. In Figure 1, the propeller radius is R, and the radius is shown in order from ``-'' to 0.9H, 0.8H, and 0.7H, and the bottom diagram shows the entire propeller. . Further, the case of a conventional propeller is shown by a dotted line curve, and the case of a conventional high skew propeller is shown by a solid line curve. In other words, the wing element near the wing tip is
The volume y of the cavity is delayed and peaks. However, since the peak of the cavity volume y is generally higher in the blade elements near the blade tip, the variation in cavity volume across the entire blade surface is lower than that of a conventional propeller, as shown in the bottom diagram. , the slope is gentle when it increases (see curve a), and the slope 1·qd is steep when it decreases (see curve ib). therefore,
The above-mentioned characteristics of conventional no-skew propellers are undesirable from the viewpoint of erosion and cavitation noise caused by rapid extinction of cavitation.

The present invention reduces the peak volume of the cavity over the entire blade surface compared to a conventional propeller, similar to the conventional I-skew propeller, and also slows down the disappearance of the cavity, thereby reducing cavitation noise, vibration, and erosion. It is an object of the present invention to provide a marine propeller that can reduce the amount of damage.

Therefore, the configuration of the present invention is characterized in that the skew angle at the propeller blade tip is in the same direction as the rotation of the blade.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows the first embodiment of the present invention, in which 1 is a propeller blade, 2 is a blade tip, 3 is a leading edge, 4 is a trailing edge, 5 is a generatrix, and 6 is a skew line ( 7 is the propeller boss, 8 is the arrow indicating the direction of propeller rotation, 9
is a conventional propeller blade, R is the propeller radius, RB is the propeller boss radius, ψ, (R) is the skew angle at the blade tip. In other words, the skew angle ψB(R) at the blade tip 2 is
In the rotational direction 8, as will be described later, the blade elements near the tip of the blade are made to pass through the high wake region faster than the blade elements near the root of the blade. In this embodiment, if the skew angle at the radial position r is 98(r), the skew angle ψ1l(r) is always on the side of the rotational direction from the generatrix 5, and from the boss 7 to the blade tip 2. As it goes, the skew angle ψ5(r)
is increasing.

FIG. 3 shows a second embodiment of the present invention, which also has the following features:
The skew angle ψ, (R) at the blade tip 2 is set in the rotational direction 8 relative to the generatrix 5, but in this embodiment, the aforementioned skew angle ψ8(r) is set in the opposite direction to the rotational direction 8 at the blade root. , near the wing tip, in the same direction as the rotation direction 8.

Figure 4 shows the cavity volume y described above with respect to the angular position θ of the reverse skew propeller blade 1 and the conventional propeller blade 9 shown in Figure 2, and is just the opposite of Figure 1. It has become. That is, in FIG. 4, the reverse skew propeller blade 1 is shown by a solid line curve, and the conventional propeller blade 9 is shown by a dotted line curve, and in a reverse skew propeller, the volume y of the cavity generated in each blade element is The peak occurs at an earlier angular position θ than that of a type propeller. Therefore, as shown in the bottom diagram of Figure 4, the cavity volume y of the entire wing surface has a peak value lower than that of a conventional propeller, and has a steep slope when increasing (see curve C), and when decreasing The slope of (see curve d) shows gentle fluctuations.

In this way, by slowing down the disappearance of the cavity, it is possible to reduce noise, vibration, and erosion caused by cavitation. Note that the reverse skew propeller blade 1 shown in FIG. 3 also has the same characteristics as the solid line curve in FIG. 4.

As described above, the present invention sets the skew angle at the blade tip in the same direction as the rotation of the blade, so that the peak value of the cavity volume of the entire blade surface can be adjusted as compared to that of a conventional high-skew propeller. Therefore, in terms of reducing stern water pressure fluctuations, it is as effective as a conventional no-skew propeller, and the gradual disappearance of the cavity prevents rapid cavity disappearance. This has the effect of reducing noise, vibration, and erosion caused by this.

[Brief explanation of the drawing]

Fig. 1 is a comparative explanatory diagram of the functions of a conventional is-skew propeller and a normal type propeller, Fig. 2 is a front view showing a part of the first embodiment of the present invention, and Fig. 3 is a diagram illustrating the operation of a conventional is-skew propeller and a normal type propeller. FIG. 4 is a front view showing a part of the second embodiment, and is a comparative illustration of the effects of the reverse skew propeller of FIG. 2 and the normal type propeller. DESCRIPTION OF SYMBOLS 1...Propeller blade, 2...Blade tip, 6...Skew line, 8...Rotation direction arrow, ψ8(R)...Skew angle at the blade tip. 1st 1Ea Child 3 Figure 2 Lamb 4 times

Claims (1)

[Claims] 1. A reverse skew propeller for ships, characterized in that the skew angle at the blade tip is in the same direction as the rotation of the blade.