JPH0155155B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a marine propulsion device.

[Prior art]

In a marine propulsion system, the ratio of the power effectively used to propel the ship, that is, the thrust power generated by the rotation of the blades and the power supplied to the propulsion device, is called the propulsion device's independent efficiency. is represented by the symbol η _O. This individual efficiency (hereinafter simply referred to as efficiency) η _O generally decreases slightly as the number of blades increases, so four-blade types are more widely used than six-blade types, but the overall area of the blade In a propulsion device with a large deployed area ratio a _E and a small load, the efficiency η _O of six blades is about 2% better than the efficiency η _O of four blades under the same design conditions. Ships with relatively low loads, such as ships and container ships, use six-blade propulsors.

On the other hand, since the wings rotate in the water behind the hull, the thrust power and torque generated is
Vibration occurs because it fluctuates periodically during rotation, and the period of this vibration differs between the case of four blades and the case of six blades. As mentioned above, when six blades are adopted to improve the efficiency η _O , if the period of vibration matches the natural frequency of the ship's hull or the torsional frequency of the blade's shaft system, extremely large hull vibrations and shaft system It is unavoidable to use four-winged blades even if the efficiency η _O is poor, as it often induces vibrations that can cause damage to the shaft system or crank, and the vibrations propagate to the living area, making the ride uncomfortable. Currently, it is being adopted.

[Summary of the invention]

The present invention was made in view of the above points, and by providing six blades: four blades and two of the blades and two blades having the same phase in the circumferential direction and different positions in the axial direction. The purpose of the present invention is to provide a marine propulsion device that is capable of achieving a high vibration frequency, thereby improving efficiency and living quarters environment, and preventing damage to the wing shaft system, etc. Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

1 to 4 show an embodiment of the marine propulsion device according to the present invention, FIG. 1 is a front view thereof, FIG. 2 is a side view thereof, and FIG. 3 is a relationship line between efficiency and output coefficient. FIG. 4 is a diagram showing the relationship between the rotation angle of the blade and the excitation force. In the figure, a propulsion shaft 2 of a propulsion device 1 is pivotally supported by a bearing 3 at the stern, and is drivingly connected to a prime mover (not shown). Four blades 6, 7, 8,
9 are protruded at positions that equally divide the circumferential direction, and furthermore, the blades 6 to 9 are provided near the bearing 3 of the blades 6 to 9.
Two blades 10 and 11 that are out of phase in the axial direction are protruded. The blades 10 and 11 are disposed in the same phase as two blades 6 and 8 among the four blades 6 to 9 in the circumferential direction.

With this configuration, the propulsion device 1 has the following performance. That is, FIG. 3 is a diagram showing the square root of the output coefficient √ on the horizontal axis and the optimal effect η _O on the vertical axis, where the solid line L ₁ indicates the conventional six-blade propulsion device and the propulsion device according to the present invention. The dotted line _L2 shows the curve of a conventional four-blade thruster. In this case, the deployed area ratio a _E of the wings of the thruster according to the present invention is 0.85, and the deployed area ratio a _E of the wings of the conventional propeller is 0.70. Note that the output coefficient Bp is given by the formula N・P _0.5 /V _2.5 , where the number of revolutions per minute of the propeller is N, the transmitted horsepower is P, and the forward speed of the propeller is V. This is commonly used in design. As is clear from the figure, the six-blade propulsion device according to the present invention has better efficiency. In addition, 6
A conventional six-blade propulsion device in which the blades are provided at the same position in the axial direction also has an efficiency approximately shown by the solid line.

FIG. 4 is a diagram showing the rotation angle θ of the propeller on the horizontal axis and the excitation force P of the propeller on the vertical axis,
The solid line L ₃ shows the curve for 4 blades, and the dotted line L ₄ shows the curve for 6 blades.
The curve for a wing is shown. The propeller according to the present invention has six blades, but since two of them overlap at the same position in the circumferential direction, the generation period of the excitation force is the same as in the case of four blades. , an excitation force is generated at the period indicated by the solid line in the figure. Therefore,
In the case where a six-winged vehicle resonates with the natural frequency of the ship's hull, this resonance can be avoided by adopting the propulsion device according to the present invention, and in terms of efficiency, it is possible to maintain the same efficiency as that of a six-winged vehicle. can do.

In this embodiment, an example was shown in which two blades 10 and 11 were arranged near the bearing 3, but four blades 6, 7,
8 and 9 may be arranged closer to the bearing 3.

〔Effect of the invention〕

As is clear from the above description, in the marine propulsion device according to the present invention, the propeller blades are composed of four blades and two of the blades, and two blades having the same phase in the circumferential direction and at different positions in the axial direction. By configuring it with wings, it is possible to obtain the periodicity of four wings in terms of vibration while maintaining efficiency equivalent to that of six wings, making it possible to ensure extremely good efficiency and reduce the natural vibration of the hull. Synchronization with the airfoils and the like can be avoided, thereby preventing damage to the wing shaft system, etc., and vibration in the living area can be reduced, improving the living area environment.

[Brief explanation of drawings]

1 to 4 show an embodiment of the marine propulsion device according to the present invention, FIG. 1 is a front view thereof, FIG. 2 is a side view thereof, and FIG. 3 is a relationship line between output coefficient and efficiency. FIG. 4 is a diagram showing the relationship between the rotation angle of the blade and the excitation force. 1... Propulsion device, 4... Propeller, 6, 7, 8,
9, 10, 11... wings.

Claims (1)

[Claims] 1 6 with 4 blades and 2 of them with 2 blades that are in the same phase in the circumferential direction and at different positions in the axial direction
A marine propulsion device characterized by being equipped with wings.