JPH052558B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a fin provided at the rear of a ship's propulsion propeller. (Prior Art) A technique for providing a finned valve behind a propeller is described in Japanese Utility Model Publication No. 13760/1983. The publication describes that in the stern section where the propeller and rudder are arranged, as shown in Figure 9, the structure is located close to the propeller behind the propeller, and its center line is approximately aligned with the axis of the propeller, and its maximum diameter is A finned valve is described in which a valve is provided in the form of a rotating body that is larger than at least the propeller hub diameter, and a plurality of fins are provided radially protruding from the outer circumference near the maximum diameter of the valve. (Problem to be solved by the invention) When fins are placed behind a ship's propeller to recover the rotational energy released from the propeller into the wake of the ship and improve propulsion efficiency, It is important to understand the wake characteristics of the operating propeller and design effective fins that match these characteristics. Up until now, the propeller wake has been replaced with an axisymmetric average flow field that corresponds to the propeller wake in a uniform flow, and when a fin system with an axisymmetric shape and arrangement that matches this is adopted. There were many. However, the wake characteristics of a propeller operating in a wake are very complex and have significant non-uniformity, so the conventional ones are not necessarily optimal from the standpoint of rotational energy recovery. In view of the above, an object of the present invention is to provide a fin attachment means that can best recover rotational energy through detailed experiments and careful calculations. (Means for Solving the Problems) The present invention provides a valve disposed close to the rear downstream side of a propulsion propeller and substantially aligned with the propeller axis, which is point symmetrical with respect to the valve axis. Fins are provided radially protruding from the valve in the starboard upper half region and port lower half region for a right-handed rotating propeller, and in the port upper half region and starboard lower half region for a left-handed rotating propeller, respectively. In addition, the length of the fins provided in the upper half region from the valve axis is at least smaller than the diameter of the propeller, and the fins provided in the lower half region are formed to be longer than the fins provided in the upper half region. This is an asymmetrical fin characterized by the following. (Operation and Examples) The operation of the above-mentioned means will be clarified in detail through the examples shown below. However, we will consider the case where the propeller rotates to the right, and in the case of counterclockwise rotation, the explanation will be omitted because the left and right relationship is simply reversed. Figure 2 shows the wake distribution measured at the propeller position for a certain ship type (tanker ship type). The directional component is represented by a vector. When the propeller is rotated at a certain rotation speed, the wake distribution of the propeller becomes the speed distribution shown in FIG. The arrow Vyz is a velocity vector in a plane perpendicular to the propeller axis, and the constant velocity line Vx is the velocity in the axial direction. If the inflow velocity distribution is determined based on these velocity distributions, the state shown in Fig. 4 will be obtained, and the inflow angle β
is given by tan ^-1 (Vt/Vx). however
Vt is the circumferential velocity component determined from Vyz. The thrust force distribution is as shown in Figure 5. The thrust distribution curve t is approximately calculated by (t=√ ₂ + ₂ ·Vt). Therefore, if we calculate the thrust distribution of FIG. 5 by 360° clockwise from the top position of the propeller, that is, the amount of thrust generated when the fin is placed at the angle θ, we obtain FIG. 6.
Thrust force t from the base of the fin to the tip (0.65R)
The integral value of is plotted on the vertical axis. It can be seen from this figure that the valid positions of the fins are 0-90° and 180-270°. Furthermore, if the state of thrust generation is illustrated in terms of the position in the radial direction from the valve, the state shown in Fig. 7 is obtained. This is the amount that indicates how much thrust is likely to be extracted. From FIG. 7, it can be seen that the latent thrust is quite unevenly distributed, and there is a possibility of obtaining a large thrust in the upper half region on the starboard side and in the lower half region on the port side. FIG. 7 shows the radial thrust distribution (dotted line) on the θ=60° and 240° lines in FIG. 5 and the result of integrating them in the radial direction (solid line). From Figure 7, the thrust distribution is 60°
The tendency is different at 240°, and when θ = 60°, a fairly large thrust is distributed at the inner radial position, but there is almost no distribution at the outer radial position. on the other hand,
When θ = 240°, the density is somewhat smaller than when 60°, but the distribution extends to the outer radial position, so the integral value in the r direction (the length direction of the fin) (the fin up to that radial position) When θ = 60°, there is almost no increase when r/R>0.7 (proportional to the thrust obtained by It can be seen that the effect on the fin length is different depending on the port and starboard sides. Figure 8 is “How to analyze a three-dimensional blade in non-uniform flow”
(Kohei Ueda, Kazuaki Yasuda: One-numerical solution method of lift surface theory: Kyushu University Engineering Bulletin Vol. 51, No. 5) This is a diagram of the values calculated based on the fin length relative to the propeller diameter. The horizontal axis is the ratio, and the vertical axis is the thrust value. Solid line is 60~120° Dotted line is 240~285°
When the fin-to-propeller diameter ratio becomes 0.7 or more, there is almost no further increase on the starboard side, whereas on the port side, the thrust increases as the fin-to-propeller diameter ratio increases. From this figure, it can be seen that the thrust values are high in the upper starboard region and the lower port region. It is confirmed that the same tendency as in FIG. 7 is observed. FIG. 1 is a rear view of an embodiment of the present invention designed based on the above experiments and careful calculations, and is compared with the conventional example shown in FIG. Assume that the outer diameter position of the propeller rotation is 2 for the outer diameter 1 of the valve. In the upper starboard region, a plurality of fins 3 are radially fixed to the valve 1 and are arranged shorter than the propeller outer diameter position 2. In addition, in the lower port side area, there are multiple blades that reach the propeller outer diameter position, that is, in the starboard upper half area for the right-handed propeller, which are located at a point symmetrical position with respect to the axis of valve 1 (almost coincident with the axis of propeller 2). Fins 3 and 4 are provided radially protruding from the bubble 1 in the lower half region of the port side (the upper half region of the port side and the lower half region of the starboard side for the left-handed rotating propeller), respectively, as shown in FIG. The length of the fins 3 provided in the upper half region (distance from the valve axis to the tip of the fin) is at least smaller than the propeller diameter, and the fins 3 provided in the upper half region are provided in the lower half region. The fins 4 are formed long. The conventional model to be compared is shown in Figure 10, in which fins 3 and 4 are arranged symmetrically on the starboard and port sides, and the propulsion efficiency of the one in Figure 10 is improved by 3% compared to the one without any fins. On the other hand, in the case of the one shown in Figure 1, the propulsion efficiency is improved by about 10%. The specific size and arrangement of the fins and their rate of increase in propulsion efficiency are shown in the table below. In the figure, A, B, and C correspond to FIG. 10, and D and E correspond to FIG. 1.

【table】

[Table] (Effects) As stated above, the present invention utilizes recoverable rotational energy by arranging asymmetrically formed fins in the most effective area in the wake (downstream) of the propeller. It can be collected effectively and most efficiently. As a result, significant savings in propulsion horsepower can be obtained and the propulsion efficiency of ships can be significantly improved, satisfying the energy saving requirements of the shipping industry. In addition, by providing fins on a rotating body-shaped valve provided in the wake of the propeller, the function of the fins can be further improved, that is, the recovery efficiency of rotational energy can be further improved.

[Brief explanation of the drawing]

Fig. 1 is a rear view showing an example for explaining the present invention, Fig. 2 is a wake distribution diagram showing experimental results, Fig. 3 is a propeller wake distribution diagram, Fig. 4 is an inflow angle distribution diagram, Figure 5 is a thrust distribution diagram, Figure 6 is a circumferential thrust distribution diagram, Figure 7 is a radial thrust distribution diagram, Figure 8 is a fin radial thrust distribution diagram, Figure 9 is a perspective view of the conventional example, FIG. 10 is a rear view of the conventional example compared to FIG. 1. 1...Valve outer diameter, 2...Propeller rotation outer diameter,
3... Starboard side fin, 4... Port side fin.

Claims (1)

[Claims] 1 In a case where a valve is provided close to the rear downstream side of the propulsion propeller and almost coincident with the propeller axis, for a right-handed propeller that is located in a point symmetrical position with respect to the valve axis, the starboard upper half area Fins are provided radially protruding from the valve in the lower half region of the port side and in the lower half region of the port side, and in the upper half region of the port side and the lower half region of the starboard side for the left-handed rotating propeller, respectively, and the valve shaft of the fin provided in the upper half region is provided. An asymmetrical fin, characterized in that the length from the center is smaller than at least the propeller diameter, and the fins provided in the lower half region are longer than the fins provided in the upper half region.