JPH0143677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to marine screw propellers, and more particularly to skewed propellers.

In general, so-called highly skewed propellers, which have a large skew in marine propellers, reduce the excitation force generated from the propeller, so they are effective in reducing ship vibration. It has been known.

In a conventional skewed propeller, as shown in FIG. 1, the skew line 2 of the propeller blade 1 extends from the cross-sectional midpoint B of the propeller blade 1 on the outer periphery of the propeller boss 3 rotating around the propeller axis center C. It is heading towards the tip A, and this skew line 2
is curved so as to point in the opposite direction to the propeller rotation direction R when the ship moves forward.

In addition, the skew line 2 connects the propeller blade 1 with
This is a line connecting the centers of the blade cross sections when cut by a concentric cylinder centered on the propeller axis center C.

Then, the skew S is defined as the skew angle θ (=∠
ACB) When expressed as S (%) = θ゜/(360゜/N) x 100 (N: number of propeller blades), a skewed propeller with a skew angle θ such that skew S is 50% or more is particularly It's called a high-rise skid propeller.

The number N of blades of a marine screw propeller is usually 3 to 6, and the corresponding skew angle θ° when the skew S=50% is 60° to 30°.

Figure 2 shows the change in the propeller excitation force when the skew S is changed, and the effect of reducing the excitation force begins to appear when S is approximately 50%, and becomes significant when S = 100%. It can be seen that there is an effect of

In this way, the high-lead propeller can reduce the vibrational force generated from the propeller, thereby effectively reducing hull vibration.

Note that the reference numeral in FIG. 1 indicates the angle formed by the tangent to the skew line 2 at the blade tip A and the line segment.

By the way, in the conventional skewed propeller as shown in FIG.
In addition to creating bending stress due to the lift generated in the wing section radially outward from this section A, torsional stress is also produced due to the influence of the force acting on the blade tip section B shown with diagonal lines. There is a problem in that the stress is higher than that at the blade root.

This can be said about other parts of the trailing edge of the blade, but it also has a relationship with the thickness of the propeller blade 1.
As shown in FIG. 3, the maximum stress often occurs at the trailing edge portion of the blade mentioned above.

Figure 3 is an iso-stress diagram (unit: Kg/
mm ² ).

Normally, when designing the propeller blade 1, the blade root part C is made thick so that the stress in the blade root part C does not exceed the allowable limit of the material, but when the aforementioned blade trailing edge part A becomes in a high stress state, There is a risk of damaging the propeller blade 1 in this part A.

In addition, when the propeller blade 1 is reversed, the center of lift shifts toward the trailing edge of the blade, and the tip A of the blade tends to bend when it hits an object in the water, creating even greater stress on the trailing edge portion A of the blade. There is a point.

The present invention attempts to solve these problems by sufficiently reducing the generation of excitation force by the propeller blades, while also preventing high stress from occurring at the trailing edge of the propeller blades. The purpose is to provide a skiud propeller that can be used.

Therefore, in the skewed propeller of the present invention, the skew line of the propeller blade from the blade root to the blade tip is oriented in the radial direction of the propeller at the blade root, or in the propeller rotation direction when the ship moves forward. The propeller blade is curved so that the intermediate portion of the propeller blade is oriented in the direction of rotation of the propeller, and the tip portion of the blade is curved so as to be oriented in a direction opposite to the direction of rotation of the propeller.

Hereinafter, a skewed propeller as an embodiment of the present invention will be explained with reference to the drawings. Fig. 4 is a front view of one propeller blade seen from the rear of the ship, and Fig. 5 shows the thrust in the radial direction of the propeller blade. It is a graph showing density.

As shown in Fig. 4, propeller blades 11 are arranged on the circumference.
The propeller boss 13, which has a propeller boss 13, rotates around a propeller axis center C, and the propeller rotation direction when the ship moves forward is as shown by an arrow R.

When the propeller blade 11 is cut by a concentric cylinder centered on the propeller axis center C, a skew line 12 connecting the centers of each blade cross section is located in the cross section of the propeller blade 11 on the circumference of the propeller boss 13. It curves toward the wing tip A from point B as shown in the figure.

That is, the skew line 12 is oriented in the opposite direction to the propeller rotation direction R at the blade root part C, oriented in the propeller rotation direction R at the intermediate part of the propeller blade 11, and oriented in the propeller rotation direction R again at the blade tip part B. It is curved so that it points in the opposite direction.

In addition, the skew line 12 is formed so that the angle Ψ measured from the tangent to the skew line 12 at point B to the line segment along the propeller rotation direction R is always positive (conventionally, Ψ = 0). be done.

In a conventional skewed propeller, this angle Ψ is zero.

Note that point D is the point in the skew line 12 where the phase in the propeller rotation direction R is most advanced.

Furthermore, the tangent to the skew line 12 at the blade tip A and the line segment form an angle.

The skew line 12 may be oriented in the radial direction of the propeller at the blade root C.

Since the skewed propeller of the present invention is configured as described above, the blade portion radially outside the trailing edge portion A of the propeller blade 11 can be made smaller, so that the above-mentioned bending stress acting on the trailing edge portion A of the propeller blade 11 can be made smaller. and torsional stress can be made sufficiently small.

Furthermore, as shown in FIG.
The effect of reducing the propeller excitation force due to skew, which was expressed as a parameter (see figure), can be represented by the angle ψ in Fig. 4.

In other words, if the corner is formed in the same way as the corner of a conventional skewed propeller (see FIG. 1), a sufficient effect of reducing the propeller excitation force can be obtained.

As detailed above, according to the skewed propeller of the present invention, the skew line of the propeller blade from the blade root to the blade tip is oriented in the radial direction of the propeller at the blade root, or the ship moves forward. The intermediate portion of the propeller blade is oriented in the direction of rotation of the propeller, and the tip portion of the blade is curved so as to be oriented in the direction opposite to the direction of rotation of the propeller. With this simple configuration, it is possible to sufficiently reduce the bending stress and torsional stress acting on the trailing edge of the propeller blade without impairing the propeller excitation force reduction effect of the skewed propeller. This has the advantage of preventing damage to the ship and increasing the safety of the ship.

[Brief explanation of drawings]

Figures 1 to 3 show a conventional skewed propeller. Figure 1 is a front view of one propeller blade seen from the rear of the ship, and Figure 2 shows the effect of reducing the propeller excitation force due to the skew. The graph shown in Figure 3 is a stress distribution diagram of the propeller blade, and Figures 4 and 5 are stress distribution diagrams of the propeller blade.
The figures show a skewed propeller as an embodiment of the present invention. Figure 4 is a front view of one propeller blade seen from the rear of the ship, and Figure 5 is the thrust density in the radial direction of the propeller blade. This is a graph showing. 11... propeller blade, 12... skew line, 13... propeller boss, A... blade tip, B...
...Cross-sectional midpoint of the propeller blade on the propeller boss circumference, C...Propeller axis center, R...Propeller rotation direction, Ψ...Angle, A...Blade trailing edge, R...
...wing tip, ha...wing root.

Claims (1)

[Claims] 1. The skew line of the propeller blade from the blade root to the blade tip is oriented in the radial direction of the propeller at the blade root or in the opposite direction to the propeller rotation direction when the ship moves forward, and The middle part of the propeller is oriented in the direction of rotation of the propeller,
A skewed propeller, wherein the tip of the blade is curved so as to point in a direction opposite to the direction of rotation of the propeller.