JPH0347237B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a hydrofoil, and more particularly to a method for controlling (operating) a hydrofoil attached to a ship's hull to prevent rolling of the ship.

In some cases, hydrofoils are attached to both sides of a ship, and the lifting force generated by these hydrofoils is used to prevent the ship from rolling. Hydrofoils used for this purpose are generally called fin stabilizers, etc., but conventionally, when controlling (operating) this type of hydrofoil, a separate stabilizer was used that only prevented rolling and corrected the hull attitude. No attempt has been made to prevent cavitation occurring in hydrofoils. As a result, large cavitation noise is generated as a result of controlling the hydrofoils, causing inconveniences such as hindering the proper use of underwater acoustic equipment on research vessels and the like.

An object of the present invention is to provide a method for controlling a hydrofoil that does not generate cavitation noise.

Therefore, the present invention prepares in advance a cavitation initiation curve (the specific curve shape depends on the shape of each hydrofoil) indicating the critical angle of the attack angle of a hydrofoil that causes cavitation to occur under a certain cavitation number, and stores it in a microcomputer. At the same time, a speed detection means and a static pressure detection means near the hydrofoil are installed in the hull, and the ship speed and the static pressure applied to the hydrofoil are measured with a pressure sensor (static pressure gauge). Calculate the current cavitation number using a microcomputer, etc., and calculate the cavitation-free range of the angle of attack of the hydrofoil under the current cavitation number, that is, the range of the angle of attack of the hydrofoil in which cavitation does not occur. The above objective is achieved by determining the cavitation initiation curve with reference to the curve, and by having the microcomputer control the rotary drive mechanism of the hydrofoil, so that the angle of attack of the hydrofoil is always maintained in a state where cavitation does not occur. This is what I am trying to do.

Embodiments of the present invention will be described below based on the drawings.

In FIGS. 1 and 2, hydrofoils 2 are provided on both sides of the underwater part of the hull 1, and each hydrofoil 2 has a third
As shown in the figure, a rotational drive mechanism 4 is connected via a rotation shaft 3, and the rotational drive mechanism 4 is connected to the hydrofoil 2.
The angle of attack α can be adjusted.

For example, near the upstream (bow side) of the hydrofoil 2, there is a ship speed detection means 5 such as a laser Doppler velocity meter (LDV) or a pitot tube, and a pressure sensor (static pressure sensor) that measures the static pressure P applied to the hydrofoil 2. A pressure gauge) 6 is arranged. Further, an angle of attack detection means 7 such as a potentiometer is attached to the rotating shaft 3, and the angle of attack α of the hydrofoil 2 is measured by this means 7. Here, the angle of attack α is the angle between the hydrofoil 2 and the flow direction.

FIG. 4 shows the control system in this embodiment. In the figure, a ship speed detection means 5, a pressure sensor (static pressure gauge) 6, and an angle of attack detection means 7 are connected to a microcomputer 8, and each value detected by each means 5, 7 and static pressure gauge 6 is sequentially The data is sent to the computer 8. Further, a rotational drive mechanism 4 is connected to the microcomputer 8, and a drive signal is sent to the drive mechanism 4, whereby the angle of attack α of the hydrofoil 2 is controlled based on commands from the microcomputer 8. .

The microcomputer 8 has an arithmetic function and is adapted to calculate the cavitation number σ. Here, the cavitation number σ is a number defined by cavitation number σ=P/1/2ρV ² , and since ρ is the density of water, if this density ρ is regarded as a constant, then the ship speed detection means 5 The ship speed V detected by the static pressure gauge 6
The static pressure P measured by the microcomputer 8
As a result, the cavitation number σ is calculated sequentially.

Further, the microcomputer 8 stores in advance a cavitation initial curve as shown in FIG. This cavitation initial curve is specifically determined by the shape of the hydrofoil 2,
This is a curve showing the critical angle of the angle of attack α of the hydrofoil 2 that causes cavitation to occur under a certain cavitation number σ, and in the figure, the lower side of the cavitation initiation curve (the axial side of the angle of attack α) is the cavitation generation region, The upper side of the cavitation initiation curve is a region where cavitation does not occur.

Next, the operation of this embodiment will be explained with reference to FIG.

Now, assume that the hull 1 is traveling at a speed Vi and a static pressure Pi is applied to the hydrofoil 2. When this system is operated, the cavitation number σi at this time is calculated by the microcomputer 8 using the formula σi=Pi/1/2ρVi ² . The critical angle of the angle of attack α of the hydrofoil 2 under the cavitation number σi calculated in this way is determined from the point S, which is the intersection of the straight line σ=σi in the figure and the cavitation initiation curve,
At this time, assume that the critical angle of the angle of attack α is αs.

On the other hand, the actual (current) angle of attack α is detected by the angle of attack detection means 7, and the critical angle αs of the angle of attack α is determined by referring to the detected actual angle of attack α and the cavitation initiation curve. For example, if the actual angle of attack is αA shown at point A in Figure 5, then the angle of attack α can be corrected to become the angle of attack αB shown at point B in the figure. A drive signal is issued from the microcomputer 8 to the rotational drive mechanism 4 to adjust the angle of attack α of the hydrofoil 2. As a result, the angle of attack α of the hydrofoil 2 moves out of the cavitation occurrence region and into the cavitation non-occurrence region, and cavitation occurrence is prevented.

According to this embodiment, since the occurrence of cavitation is avoided, the occurrence of cavitation noise can be effectively prevented. Therefore, no trouble will occur when using underwater acoustic equipment or the like.

Note that the cavitation initial curve is determined specifically through experiments and the like depending on the shape of the hydrofoil 2, and therefore, the cavitation initial curve is not limited to the shape shown in FIG.
Further, in the above description, the density ρ of water was taken as a constant, but in order to perform more accurate control, the density ρ of water may also be detected and used for calculating the cavitation number σ. Further, the calculation of the static pressure P may also take into account the saturated vapor pressure of water. moreover,
The automatic control is not limited to the microcomputer 8, but manual or semi-manual operation may also be performed.

As described above, according to the present invention, it is possible to provide a hydrofoil control method that does not generate cavitation noise.

[Brief explanation of drawings]

Fig. 1 is a front view showing an embodiment of a ship body to which the hydrofoil control method according to the present invention is applied, Fig. 2 is a plan view thereof, and Fig. 3 is a schematic diagram of a control device to which the above embodiment is applied. FIG. 4 is a control system diagram of the embodiment, and FIG. 5 is a diagram showing an example of a cavitation initial curve. 2...Hydrofoil, 3...Rotary shaft, 4...Rotary drive mechanism, 5...Ship speed detection means, 6...Pressure sensor (static pressure gauge), 7...Angle of attack detection means.

Claims (1)

[Scope of Claims] 1. A method for controlling a hydrofoil provided on a ship hull that can adjust the angle of attack in order to prevent rolling of the ship body, the method comprising: determining the critical angle of the angle of attack of the hydrofoil that causes cavitation to occur under a certain cavitation number; In addition to preparing in advance a cavitation initiation curve showing A cavitation-free area of the angle of attack of the hydrofoil under the calculated cavitation number is determined with reference to the cavitation initiation curve, and the hydrofoil is operated in the determined cavitation-free area. How to control the wings.