JP2014169012A - Propeller inlet flow field improvement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for further improving propulsion performance in a technique for suppressing cavitation of a propeller.SOLUTION: A propeller inlet flow field improvement system comprises: a suction hole 5 sucking water flow of a stern 2 under an axis of a propeller 3; and a jet hole 9 jetting the water sucked by the suction hole 5 toward an upper end 10 of the propeller 3. On the stern 2, a peeling area 6 where peeling occurs easily exists on a ship body outer board near a skeg (bilge part) to which a stern tube is installed. On the peeling area 6, the suction hole 5 is provided.

Description

  The present invention relates to a technique for improving the propulsion efficiency of a ship.

  In order to improve the propulsion performance of a ship, a technique for supplying a jet to the upper end of a propeller is known. When the ship is traveling, cavitation that causes a reduction in propulsion efficiency may occur at the upper end of the propeller and the like. By injecting water to the location where cavitation of the propeller occurs, cavitation can be suppressed and propulsion efficiency can be improved.

  Patent Document 1 discloses a technique for preventing the occurrence of cavitation by ejecting seawater to a propeller.

JP 2010-280297 A

  A further means that can suppress cavitation and improve propulsion efficiency is desired.

  In one aspect of the present invention, the propeller inflow flow field improvement system includes a suction portion that sucks the water flow of the stern portion below the propeller shaft, and an injection portion that injects water sucked by the suction portion to the upper end portion of the propeller. Prepare.

  Additional means are provided that allow cavitation to be suppressed and propulsion efficiency to be improved.

FIG. 1 is an explanatory diagram of a bilge vortex. FIG. 2 is a side view of the hull. FIG. 3 shows the position of the release region. FIG. 4A is a side view of the hull near the stern. FIG. 4B is a cross-sectional view of the suction hole. FIG. 5 is a side view of the hull near the stern.

  Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. In general, it is known that a bilge vortex is generated in a stern tube at the stern during the navigation of a ship, with the flow of seawater separating on the hull surface. FIG. 1 is a side view of the stern. When the main machine 102 rotates the propeller 101 via the shaft 103, a propulsive force is generated. The propulsion direction is controlled by the rudder 104. While the ship is propelled, the flow of seawater along the hull is separated in the separation region 106, and a bilge vortex 105 is generated.

  The bilge vortex becomes a wake that flows into the propeller and contributes to the improvement of the propeller efficiency. On the other hand, it increases the resistance of the hull. Therefore, depending on the ship type, the propulsion performance can be improved by suppressing the occurrence of bilge vortices.

  Therefore, in one embodiment of the present invention, by sucking the water flow of the stern part and injecting it to the upper end of the propeller, the occurrence of cavitation in the propeller is suppressed, the separation of the water flow in the stern part is suppressed, and the generation of the bilge vortex is prevented. be able to. As a result, a technique is provided that can suppress the generation of bilge vortices and improve the propulsion performance together with cavitation.

  Below, the concrete means for achieving said effect is demonstrated. FIG. 2 is a side view of a hull to which the propeller inflow flow field improving system according to one embodiment of the present invention is applied. The hull 1 is propelled by the rotation of a propeller 3 provided on the stern 2. In the stern 2, a peeling region 6 where peeling is likely to occur is present on the hull outer plate near the skeg 4 where the stun tube is installed (bilge portion). A suction hole 5 is provided in the peeling region 6. A pump 8 is provided in the middle of the pipe 7 to generate a suction force in the direction of sucking water around the hull from the suction hole 5. However, if water is sufficiently taken into the pipe 7 by the water flow around the hull 1, the pump 8 may be omitted.

  The suction hole 5 is connected to the injection hole 9 via a pipe 7 provided in the ship. The injection hole 9 is provided on the upstream side (the bow side) of the upper end portion 10 of the propeller 3. The suction hole 5, the pipe 7, the pump 8, and the injection hole 9 constitute a propeller inflow field improvement system.

  When the hull 1 is propelled by the propulsion force of the propeller 3, the water (seawater) around the hull 1 is taken into the pipe 7 from the suction hole 5 by the suction force generated by the pump 8. The water in the boundary layer around the hull is sucked in from the suction hole 5 in the bilge portion, so that peeling is suppressed. As a result, the generation of bilge vortices can be suppressed and the resistance of the hull can be reduced.

  The water taken in from the suction hole 5 is jetted from the jet hole 9 and supplied to the upper end portion 10 (propeller tip) of the rotating surface of the propeller 3. The upper end portion 10 of the propeller 3 is a portion where cavitation is likely to occur when the hull 1 is propelled. By supplying water from the injection hole 9, the occurrence of cavitation at the upper end portion 10 of the propeller 3 is suppressed, and effects such as improvement of propulsion performance and reduction of vibration can be obtained.

  In order to supply to the upper end portion 10 of the propeller, water taken in from the suction hole 5 provided in the separation region 6 of the stern 2 is used. The separation region 6 is relatively short from the propeller 3. Therefore, the additional piping equipment for supplying the propeller with the water provided in the peeling region 6 can be relatively small.

  The water sucked from the suction hole 5 may be sufficient to suppress cavitation. For this reason, for example, a large amount of water is not required as the cooling water of the main engine, and a relatively small amount of water may be sucked. Therefore, the propeller inflow flow field improving system in the present embodiment can be realized by adding a relatively small facility.

  Next, the peeling region 6 will be described. The peeling portion 6 where the suction hole 5 is provided is usually below the shaft of the propeller 3 in the vertical direction when the hull 1 is in a horizontally stationary state. Moreover, the separation location where the separation of the water flow in the boundary layer that causes the bilge vortex changes according to the ship speed. Therefore, it is desirable to provide a plurality of suction holes 5 so as to be able to cope with the change in the peeling location when the boat speed changes. The peeling area 6 in FIG. 2 shows an area where a plurality of such suction holes 5 are provided, that is, an area where peeling can occur according to changes in ship speed. FIG. 3 shows a cross-sectional view of the skeg 4 as viewed from the stern direction. The peeling region 6 is located on the ship bottom side with respect to the shaft C of the propeller 3. Tangent lines L1 and L2 are drawn on the left and right sides of the hull with respect to the skeg 4 from the ship bottom direction, and a separation region 6 is drawn at the contact point with the tangent lines L1 and L2.

  Next, the modification regarding the suction hole 5 of a propeller inflow flow field improvement system is shown to FIG. 4A and FIG. 4B. 4A is a side view of the stern, and FIG. 4B is a cross-sectional view of the outer plate of the hull provided with the suction holes 5a as seen from above. In this modification, each suction hole 5a has a side surface 12 that inclines toward the stern direction from the outboard 13 toward the inboard 14. When the hull 1 is moving forward, water outside the outboard 13 flowing on the hull surface flows along the side surface 12 and is taken into the pipe 7. By such a suction hole 5a, water near the surface of the hull 1 in the peeling region 6 can be taken in more smoothly, and generation of bilge vortices can be suppressed.

  FIG. 5 shows still another modification of the propeller inflow flow field improvement system. In this modification, a compressor 15 is provided in the pipe 7. In FIG. 5, the suction pump 8 of FIG. 1 is not described, but a pump 8 may be provided. The compressor 15 controls the flow rate of water injected from the injection hole 9 by applying pressure to the water in the pipe 7.

  The compressor 15 can adjust the flow rate of water injected from the injection holes 9 based on a ship speed signal 16 output from a sensor or the like that measures the speed of the hull 1. For example, the compressor 15 indicates a pressure corresponding to the ship speed signal 16 based on a table or a function stored in advance in a storage device (indicating the relationship between the ship speed and the pressure that the compressor 15 applies to the water 7 in the pipe). Feed water into pipe 7. As a result, when performing high-speed operation in which cavitation is relatively likely to occur, it is possible to perform injection according to the ship speed, such as supplying water with a higher flow velocity from the injection hole 9.

DESCRIPTION OF SYMBOLS 1 Hull 2 Stern 3 Propeller 4 Skeg 5, 5a Suction hole 6 Peeling area 7 Piping 8 Pump 9 Injection hole 10 Upper end part 11 Outer plate 12 Inclined surface 13 Outboard 14 Inboard 15 Compressor 16 Ship speed signal 101 Propeller 102 Main engine 103 Shaft 104 Rudder 105 Bilge vortex 106 Separation area

Claims (5)

A suction part for sucking the water flow of the stern part below the axis of the propeller;
A propeller inflow flow field improvement system comprising: an injection unit that injects water sucked by the suction unit onto an upper end portion of the propeller. A propeller inflow flow field improving system according to claim 1,
The separation point where the separation of the water flow causing the bilge vortex occurs in the stern part changes according to the ship speed,
The said suction part is a propeller inflow flow field improvement system which sucks in the said water flow from the hole provided in the several position according to the change of the said peeling location. A propeller inflow flow field improving system according to claim 1 or 2,
The propeller inflow flow field improving system, wherein the suction part includes a pump for sucking the water flow. A propeller inflow flow field improving system according to any one of claims 1 to 3,
The suction part sucks the water flow through a hole provided in the stern part,
The said propeller inflow field improvement system which has a side surface which inclines toward a stern direction as it goes inside from the outer side of a hull. A propeller inflow flow field improving system according to any one of claims 1 to 4,
The propeller inflow flow field improvement system, wherein the injection unit performs injection on an upper end portion of the propeller at a flow velocity corresponding to a ship speed.

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