JP2883006B2 - Skewed propeller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skewed propeller, and more particularly to a rake distribution shape of a propeller blade as a whole.
Reverse S-shaped rake distribution curve
Reduces excessive stress on the trailing edge of the propeller blade during rotation
A skewed propeller that can be used . In addition,
The present invention is applicable to blades having a relatively large aspect ratio (aspect ratio of 1.0 or more), such as fans such as fans and ventilation fans, and turbine blades.

[0002]

2. Description of the Related Art A screw propeller in which the cross section of a propeller blade is shifted in the direction opposite to the rotational direction along the screw surface toward the tip (skew back) is conventionally called a skewed propeller, It is widely used because it has the advantage that wings rotating in the immediate vicinity of the shaft bracket can be prevented from simultaneously approaching over the entire length, reduce sudden fluctuations in impact and torsional moments, and can rotate smoothly.

In a conventional skewed propeller, as shown in FIG. 8, a propeller blade 30 is mounted on a boss 33a perpendicular to the propeller axis aa [rake (blade inclination) 0] or designated by reference numeral 31. The boss 33 is attached to the boss 33 with a constant positive inclination (positive rake) or a constant negative inclination (negative rake) as indicated by reference numeral 32. In each of these cases, the bending moment due to the centrifugal force is determined according to the direction and amount of rotation and inclination of the propeller, and is in the same direction in any radial direction of the blade.

[0004]

In the skewed propeller, the skew of the thrust (thrust) generated on the tip side of the wing due to the skew back to the trailing edge side of the wing profile at the tip of the wing, which is a characteristic of the wing shape. Since the reaction force acts not only on the blade root side section as bending stress but also on the torsional stress, the combined stress on the trailing edge side of the blade tends to be excessive.

In conventional skewed propellers, to prevent such a phenomenon, the wing thickness is increased and the stress value is reduced. However, like a recent container ship, a high horsepower engine is equipped for speeding up. As the skew propeller progresses, it is required to adopt a large skew angle to achieve low vibrating force and to reduce the bearing pressure on the stern bearing. There is a demand for realizing a skewed propeller that avoids the occurrence of excessive stress in the skewed propeller.

An object of the present invention is to provide a skewed propeller satisfying such a demand. That is, in general, the thrust (thrust) generated on a propeller blade
In addition to the fluid force, which is the reaction force of the propeller, and the centrifugal force generated by the rotation of the propeller around its axis, the propeller blades with a constant positive or negative inclination have the bias amount associated with the inclination with the moment arm. Bend moment acting.

[0007] In addition, in the case of a skewed propeller, a torsional stress is generated with the generation of a bending moment using a bias amount corresponding to a skewback amount as a moment arm. The present invention changes the rake ( blade inclination) of a propeller blade from the blade root to the blade tip, and as a whole, an inverted S-shape
As a rake distribution curve, skewed propeller specific twisting stress by balancing the bending stress due to centrifugal force, in particular reverse times to reduce the level of combined tensile stress
An object of the present invention is to provide a skewed propeller capable of relieving excessive stress on the trailing edge side of a retreating surface of a propeller blade during rotation .

[0008]

According to a first aspect of the present invention, there is provided a skewed propeller comprising a propeller boss and a propeller blade attached to the propeller boss. The rake distribution shape of the propeller blade has a convex portion on the advancing surface side from the blade root portion to the 60% radius position, and a convex portion on the reversing surface side from the 60% radius position to the blade tip portion. Hold the above reverse side
Rake distribution from the convex part to the wing tip to the forward
Inclined to the surface side, the convex portion toward the advance surface side, and the reverse surface
Rake distribution curve connecting the convex part to the side and the tip of the wing
Are characterized by forming an inverted S-shaped curve .

In the skewed propeller according to a second aspect of the present invention, the convex portion on the forward surface side and the convex portion on the reverse surface side are balanced in a propeller axial direction about a reference line of the propeller blade. It is characterized by being arranged.

[0010]

According to the skewed propeller of the present invention described above, (1) excessive tensile stress (40% to 50% radius position) on the trailing edge side (40-50% radius position) of the skewed propeller blade advance surface during steady forward movement (propeller forward rotation). (Tension stress caused by forward thrust and centrifugal force caused by forward thrust generated on the tip side), the centrifugal bending moment caused by centrifugal force The generated compressive stress is applied to this portion to suppress generation of excessive stress on the blade. (2) Further, regarding the excessive tensile stress generated on the trailing edge side (near the 80% radius position) of the skewed propeller blade during the reverse rotation of the propeller, the center of gravity of the cross section located on the tip side is set to the blade advance surface side. Position the rake distribution curve
Since the whole is formed in an inverted S-shape, the compressive stress generated by the bending moment due to the centrifugal force acts on this portion to suppress the generation of excessive stress on the blade.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A skewed propeller according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the shape of the blade rake distribution, and FIG. FIG. 3 is a development view of FIG.
FIG. 4 is a schematic view showing the relationship between the forward surface stress and the rake distribution during the forward rotation, FIG. 5 is an expanded view thereof, FIG. 6 is a blade stress distribution diagram on the forward surface during the forward rotation, and FIG. It is a blade stress distribution figure of the reversing surface at the time.

In FIG. 1, reference numeral A denotes a propeller blade of a skewed propeller mounted on a propeller boss B. Although only one propeller blade A is shown in FIG. 1, a plurality of propeller blades A are attached to the propeller boss B at equal intervals in this embodiment.

When the propeller blade A is close to the blade root, the rake distribution shape has a positive slope (positive rake, see FIG. 8 and description thereof) having a convex portion 2a directed toward the advancing surface (left side in FIG. 1). ), And near the front end, a negative slope (negative rake, see FIG. 8 and its description) having a convex portion 3a toward the reversing surface (right side in FIG. 1) is further formed.
Rake distribution shape from the convex part 3a to the wing tip
To form an inverted S-shaped rake distribution as shown by the rake distribution curve indicated by reference numeral 1.

That is, from the root of the blade to a position of approximately 60% radius (0.6R), a rake distribution is formed on a positive slope blade surface having a rake distribution as shown by a curve 2 having a convex portion 2a protruding toward the advancing surface. A portion between the 60% radius position and the tip of the blade is formed on a negatively inclined blade surface having a rake distribution as indicated by a curve 3 having a convex portion 3a on the reversing surface side. The rake distribution between the two wing surfaces is represented by a smooth curve connecting the rake distribution curves 2 and 3, and the rake distribution is balanced as a whole in the propeller axis direction around the propeller reference line 4.

FIGS. 2 and 3 show an excessive stress portion (propagating after the blade retreating surface) generated on the trailing edge side of the retreating surface of the propeller blade A during the reverse rotation caused by the adoption of the rake distribution at the blade tip indicated by reference numeral 3 in FIG. Near 80% radius position on the edge side, reference numeral 29 in FIG. 7)
2 shows the mechanism of stress relaxation in the above. That is, during the reverse rotation of the propeller, a reverse thrust 6 and a centrifugal force 7 are generated in the blade section (reference numeral 5 in FIGS. 2 and 3) at a position corresponding to the reference numeral 29 of the propeller blade A, and these forces are generated by the blade. Bending moment 8 and centrifugal force 7 due to thrust 6
Act as a bending moment 9 due to

In the case of this embodiment, FIG.
Since the rake distribution is fluctuated in an inverted S-shape as shown by, excessive stress at the tip of the blade shown in FIGS.
, The bending moment 9 acts so as to incline the tip of the blade toward the retreating surface, and the compressive stress 14 generated by the bending moment 9 causes the tensile stress 12 due to the reverse thrust 6 and the tensile stress 13 due to the centrifugal force 7 to change. The overstress in the overstress portion 29 is alleviated by acting to reduce the combined stress.
Reference numeral 10 in FIG. 3 indicates a forward plane, and reference numeral 11 indicates a reverse plane.

FIGS. 4 and 5 show excessively stressed portions (the trailing edge of the blade advance surface) generated on the trailing edge of the forward surface of the propeller blade A during forward rotation caused by the adoption of the rake distribution at the blade center indicated by reference numeral 2 in FIG. It shows the mechanism of stress relaxation at the 40-60% radius position, reference numeral 28) in FIG. In other words, the forward thrust 16 is applied to the blade section (reference numeral 15 in FIGS. 4 and 5) at the position corresponding to the reference numeral 28 of the propeller blade A during the forward rotation of the propeller.
And a centrifugal force 17 are generated, and these forces act as a bending moment 18 due to the forward thrust and a bending moment 19 due to the centrifugal force on the section 15.

Also in this case, since the center of gravity on the tip end side of the section indicated by the reference numeral 15 is located on the reverse side, the bending moment 19 due to the centrifugal force causes the compressive stress 24 as in FIGS. Is generated, and the compressive stress 24 acts to relieve the excessive stress in the excessive stress portion 28.

In FIG. 5, reference numeral 20 denotes a forward surface, and reference numeral 21 denotes a forward surface.
Indicates the reverse plane, and reference numeral 22 indicates the forward thrust 16
Indicates a tensile stress, and reference numeral 23 indicates a tensile stress due to the centrifugal force 17. In FIG. 6, reference numeral 25 denotes a skew back amount. Generally, in a skewed propeller, this amount is large and the wing leading edge 26 is phased backward with respect to the wing reference line 4 and the wing trailing edge 27 is , The excessive stress shown on the forward surface 28 during forward rotation, and the reverse stress on the reverse surface during reverse rotation.
It has a tendency to cause excessive stress as shown in 29.

Here, the boundary between the rake distribution 2 having a convex portion protruding toward the advancing surface and the rake distribution 3 having a convex portion protruding toward the reversing surface is defined by a 60% radial position (0.6R position) from the blade root. The reason for setting to is described. That is, in general, the boss diameter of the propeller is about 13% to 18% of the propeller blade diameter R, so that the length of the propeller wing is 82% to 87% of the propeller diameter.

Therefore, the radius x located near the center of the wing is x / R = (13-18) + (82-87) /2=54-61.5%.

From such a background, "approximately 60% radial position from the blade root" means near the center of the propeller blade, and in the present invention, "approximately 60% radial position" means "50 to 65% radial position". I do. Further, the radial position of the largest protruding portion (protruding portion 2a) in the protruding surface side is preferably a radial position of 30 to 50%,
In addition, the largest protruding portion (protruding portion 3a) in the protruding on the reversing surface side
Is preferably a 70-85% radius position.

The maximum protrusion amount of the convex portions 2a and 3a is the maximum value of the deviation from the propeller reference line, that is, the rake amount at the inflection point of the rake distribution, and
10% or more is desirable.

[0024]

As described above, according to the skewed propeller of the present invention, the following effects and advantages can be obtained. (1) At the time of forward rotation, a forward thrust and a centrifugal force are generated at an excessive stress portion on the trailing edge side of the forward surface of the propeller blade, and the bending moment due to the forward thrust and the centrifugal force with respect to the blade section of the excessive stress portion. bending and moment acts but can by generating compressive stress in the blade sections in bending moment by the centrifugal force, to alleviate overstressing of the overstress section. (2) at the time of reverse rotation, the rear advancing the thrust and the centrifugal force is generated overstress portion of the reverse surface trailing edge of the propeller blade, a bending moment due to the moment and the centrifugal force bending by the backward thrust of the overstress section Acts on the wing section, but the wing
Make the entire rake distribution curve an inverted S-shaped curve
With this configuration, a compressive stress is generated in the blade section by the bending moment due to the centrifugal force, and this compressive stress is
Between tensile stress due to binary thrust and tensile stress due to centrifugal force
It acts so as to reduce the synthetic stress, and can reduce the excessive stress in the excessive stress portion. (3) Due to the reasons (1) and (2), it is possible to alleviate the blade trailing edge stress of the propeller blade of the skewed propeller or to adjust the blade surface stress distribution while minimizing the blade thickness increase.

[Brief description of the drawings]

FIG. 1 is a shape diagram of a blade rake distribution of a propeller blade of a skewed propeller as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing the relationship between the reverse surface stress and the rake distribution during the reverse rotation.

FIG. 3 is an expanded view of the same.

FIG. 4 is a schematic diagram showing a relationship between a forward surface stress and a rake distribution during the forward rotation.

FIG. 5 is an expanded view of the same.

FIG. 6 is a blade stress distribution diagram on a forward surface during the forward rotation.

FIG. 7 is a blade stress distribution diagram on a forward surface during the reverse rotation.

FIG. 8 is a shape diagram showing a wing rake of a conventional skewed propeller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rake distribution 2 Rake distribution 2a convex part 3 Rake distribution 3a convex part 4 Blade reference line 5 Blade cross section 6 Reverse thrust 7 Centrifugal force 8 Bending moment by reverse thrust 9 Bending moment by centrifugal force 10 Forward surface 11 Reverse surface 12 By reverse thrust Tensile stress 13 Tensile stress due to centrifugal force 14 Compressive stress 15 Blade section 16 Forward thrust 17 Centrifugal force 18 Bending moment due to forward thrust 19 Bending moment due to centrifugal force 20 Forward plane 21 Reverse plane 22 Tensile stress due to centrifugal force 24 Compressive stress 25 Skew back Quantity 26 Leading edge of wing 27 Trailing edge of wing 28 Overstress (part) 29 Overstress (part)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B63H 1/26

Claims (2)

(57) [Claims] 1. A skewed propeller comprising: a propeller boss; and a propeller blade attached to the propeller boss, and the rake distribution shape of the propeller blade is set between a root portion and a 60% radius position on a forward surface side. A convex portion toward the retreating surface side from the 60% radius position to the tip of the wing, and a rake portion from the convex portion toward the retreating surface to the tip of the wing.
The cloth is inclined toward the advance surface, and the convex portion toward the advance surface is provided.
Between the convex portion toward the reverse surface and the tip of the wing.
A skewed propeller, wherein the rake distribution curve forms an inverted S-shaped curve . 2. The skewed propeller according to claim 1, wherein the protruding portion on the advancing surface side and the protruding portion on the reversing surface side are balanced in a propeller axial direction about a reference line of the propeller blade. A skewed propeller, characterized in that it is arranged as a skewed propeller.