JP5850507B2 - Air bubble entrainment prevention device for ships - Google Patents

Description

  The present invention relates to a bubble entrainment prevention apparatus that eliminates a decrease in propeller efficiency due to entrainment of bubbles in propeller means in a ship frictional resistance reduction apparatus that reduces the frictional resistance of a hull by ejecting bubbles into water.

  As a study of ship drag reduction, many achievements have been obtained for wave resistance, but friction resistance, which is said to account for about 80% of the total resistance of large ships, is related to complex turbulence phenomena. Until now, no outstanding results have been obtained. During the navigation of a ship, a turbulent boundary layer develops along the hull surface below the waterline, and frictional resistance acts on the hull surface, reducing propulsion performance. As a means for reducing the frictional resistance of the hull surface, a bubble ejection method in which fine bubbles are injected into a boundary layer along the surface has recently attracted attention and research as a promising measure for reducing frictional resistance. The bubble jet method has a remarkable effect of reducing frictional resistance, is relatively resistant to pollution, and has no problem of environmental pollution to the ocean or water system. It is considered a method.

  However, this bubble ejection method requires power because it overcomes the water pressure from the ship side and the bottom of the water and generates bubbles, increasing the net reduction effect considering both frictional resistance reduction effect and bubble generation power. Consideration was necessary. In addition, ships navigating oceans and rivers are subject to various disturbances such as waves and currents, and are also affected by the state of cargo and navigation, how to effectively reduce frictional resistance. It was said. The research so far has mainly been research using laboratory levels and model ships, and has not been considered taking into account these disturbances and navigational conditions. The inventors of the present application used an actual ship for the current state of such research, and investigated the relationship between the bubble ejection and the frictional resistance reduction effect in a situation where the ship situation, navigational state, sea state, etc. are close to reality, A lot of knowledge has been obtained in search of increasing the net reduction effect. Moreover, in the investigation using such an actual ship, it has been clarified that the blown out bubbles are caught in the propeller means, reducing the propeller efficiency, and worsening the net frictional resistance reduction effect. .

  On the other hand, in the field of patents, there is no specific countermeasure against the bubble impinging on the propeller means in the method of reducing the frictional resistance of the ship using fine bubbles. However, Patent Documents 1 and 2 can be cited as related ones.

  This Patent Document 1 is an enlarged ship having a square coefficient of 0.6 to 1.0, and includes a microbubble jet port disposed at a predetermined position just below the water line on both sides of the bow, and the predetermined position is: At the normal navigation speed, the streamline on the hull surface that passes through this position is the position where the streamline located at the top of the streamline passing through the bow hull surface to the bottom of the hull parallel part, and the propeller wing sweep at the stern The propeller propulsion efficiency is prevented from lowering so as not to interfere with the excessive circle C.

  Because of this configuration, the streamline itself can be constant only under the conditions of air bubble ejection, ship navigation conditions, and the water system being very stable, so it cannot be practical. It was a thing. In other words, it is affected by the state of the gas outlet, the amount of bubble ejection, the speed of the ship and the load condition, and the waves, winds and tidal currents in the ocean. The result was a drop immediately.

  Further, in Patent Document 2, the contact of water with the outer surface of the hull of the ship 10 that is normally associated with water is reduced by the advantageous introduction of air or gas pressurized or compressed so as to cover the outer surface. The compressed air is maintained on the outer surface by various grooves 30, channels 66 or half-planes 124 that extend in the longitudinal direction of the ship's bottom, in certain applications vertical sides. They prevent the flow of compressed gas to the water surface. Compressed air or gas is recovered before exiting the stern or stern side and recirculated to the bow via the energy efficient regenerators 34, 36, 37, 38, and thus the compressed air spilled from the bow to the stern. Alternatively, gas energy is recovered.

  Because of this structure, the original purpose is to capture and regenerate compressed air that passes under the hull so as to avoid loss of energy stored in compressed air and gas, and to prevent air bubbles from getting into the propeller. There was nothing to consider about. Also, there was no consideration for disturbances such as waves and tidal currents and the use of water taken.

JP 2007-26041 A Special table 2001-524421 gazette

  The present invention solves the above-mentioned problems of the prior art, effectively reduces the frictional resistance even when the navigational state of the ship and the situation of the ship change, prevents entrainment of bubbles in the propeller means, An object of the present invention is to provide a device for preventing bubble entrainment in a ship, which prevents a decrease in efficiency and improves the effect of reducing the net frictional force.

  In order to achieve such an object, the present invention provides a ship, a gas outlet for ejecting bubbles to at least the bottom of the ship, an air supply means for supplying gas to the gas outlet, and a hull of the ship. A propeller means provided at the stern, and an entrainment preventing structure comprising a bulge portion having a curved surface capable of separating the air bubbles, which prevents the entrainment of the air bubbles into the propeller means at least on the bottom of the stern side behind the gas ejection port. And the raised portion is a substantially V-shaped mound extending left and right around the plane center line of the hull, and has a structure in which the front is slightly lower and the rear is raised. Good.

  Here, the air supply means refers to a blower, a turbine driven compressor, a pneumatic supply source pre-installed in the ship, a pressurized engine exhaust gas, etc. that can secure an effective air supply amount for generating bubbles. That is, it is particularly preferable that the amount of air supply is small even when the discharge side pressure fluctuates. In addition to an electric motor that drives the air supply means, an engine that is driven by liquid fuel or gas fuel, a turbine that obtains a rotational force using exhaust from an engine of a ship, and a hydraulic pressure that is driven by hydraulic pressure or air pressure Includes motors and pneumatic motors.

  The propeller means refers to a screw propeller, a high-speed cube propeller, a variable pitch propeller, a pod type propulsion device, a Z drive, an impeller driven water jet, or the like.

  Further, the entrainment prevention structure refers to a structural countermeasure that prevents entrainment of bubbles in the propeller means, and includes a raised portion having a curved surface, a V-shaped mound, a bubble protector, a porous body, etc. It refers to all structures that effectively prevent air bubbles from getting into the propeller means, and those that increase little resistance when propelling a ship are preferred.

  By being configured as described above, air bubbles sent from the air feeding means and ejected from the gas jetting outlet are released by an entrainment prevention structure provided at least on the bottom of the ship so as not to get caught in the propeller means. Is.

Moreover, the said structure WHEREIN: The said entrainment prevention structure is good also as what is comprised as a protruding part with the curved surface which can isolate | separate a bubble.

  By being configured in this way, bubbles are released so as not to be caught in the propeller means by the raised portion having a curved surface raised from at least the ship bottom on the stern side behind the gas jet port.

Moreover, the said structure WHEREIN: The said protruding part is good also as what is comprised as a V-shaped mound which spreads right and left centering | focusing on the plane centerline of the said hull.

  By being configured in this way, the bubbles are symmetrically released by a V-shaped mound spreading left and right around the plane center line of the hull so that the bubbles are not caught in the propeller means.

  Moreover, the said structure WHEREIN: The said entrainment prevention means is good also as what is comprised as a bubble guard provided in the said propeller means vicinity.

  By being configured in this way, bubbles are sent from the air supply means, ejected from the gas outlet and reach the vicinity of the propeller means, and the propeller means to be caught in this is protected by the bubble protector provided nearby. To do.

  In the above configuration, the bubble protector may have a large number of apertures and be provided in a substantially V shape so as to prevent at least the bubble from being caught in the lower portion of the propeller means.

  By being configured as described above, the bubble protector with a large number of apertures allows the bubbles to escape to the outside, preventing at least the entrainment of bubbles at the bottom of the propeller means, and inhibiting the inflow of water into the propeller means It is something to avoid.

In order to achieve the above object, a ship bubble entrainment prevention apparatus according to claim 1 of the present invention includes a gas jet port for jetting bubbles at least to the bottom of the ship, and gas is supplied to the gas jet port. An air supply means, a propeller means provided at the stern of the hull of the ship, a bubble suction means for sucking the bubbles provided in front of the propeller means at the rear of the gas outlet, and behind the bubble suction means. The rear part is raised from the bottom of the ship and the front part is formed to be slightly lower than the rear part, thereby speeding up the water flow and separating the remaining portion of the bubbles from the ship bottom. And an entanglement preventing structure having a raised portion having a curved surface which can be further lowered from the bottom of the ship and can lower the flow velocity of the lower portion of the propeller means .

  Here, the means for sucking bubbles is a blower that sucks bubbles, a compressor, a pump that sucks water mixed with bubbles, an ejector, etc., which is operated using dedicated power, a thing using existing facilities of a ship, etc. Say.

  By configuring as described above, the bubbles ejected from the gas ejection port are sucked by the bubble sucking means provided in front of the propeller means so as not to be caught in the propeller means, and the sucked bubbles are affected by the propeller means. There is no discharge to the outside.

  Further, in addition to the above configuration, the bubble suction means may have a gas-liquid separation mechanism that separates the sucked bubbles and water, and may be configured by using the separated water for other purposes of the ship.

  Here, the gas-liquid separation mechanism is the one that uses the buoyancy to reduce the flow rate of the water sucked together with the bubbles and separates the bubbles from the water, the one that uses centrifugal force, the one that uses fluid force, and the resistance of the perforated plate And those using chemical materials, etc., including the related mechanisms in the vicinity.

  By being configured in this way, the bubbles and water sucked by the gas-liquid separation mechanism are separated, and the separated water is used for other uses of the ship such as engine cooling water.

Further, as described above, the rear part is raised from the bottom of the ship and the front part is formed to be slightly lower than the rear part in order to prevent air bubbles from getting into the propeller means further behind the bubble suction means. A curved surface capable of speeding up the water flow and separating the remaining portion of the bubbles from the bottom of the ship, further reducing the flow velocity of the lower part of the propeller means, while making the streamline of the water flow further downward from the ship bottom. It is good also as a structure which provided the entanglement prevention structure with the raised part which it had.

By being configured in this way, even if bubbles are left unabsorbed due to a disturbance due to disturbance, the rear part rises from the bottom of the ship and the front part is formed to be slightly lower than the rear part. The curved surface can separate the remaining portion of the bubble from the bottom of the ship by speeding up the water stream, further lowering the flow rate of the water stream from the bottom of the ship and slowing down the flow velocity of the lower part of the propeller means . The entanglement preventing structure having the raised portion allows air bubbles to escape and prevents the entanglement of the propeller means.

  The present invention also relates to a ship, a gas jet port for ejecting bubbles to at least the bottom of the ship, an air supply means for sending gas to the gas jet port, and a propeller provided on the stern side of the hull of the ship. And a bubble entrainment detecting means for detecting entrainment of bubbles in the propeller means, and when the entrainment of bubbles is detected by the bubble entrainment detecting means, the ejection condition and / or the air supply of the gas ejection port You may make it comprise by changing the driving | running condition of a means.

  Here, the bubble entrainment detection means is, for example, a sensor that detects that the driving force of the propeller has changed as a result of bubbles being entrained in the propeller means as a change in thrust force or torque of the propeller drive shaft, This refers to a vibration sensor that detects vibrations generated in the means, an acoustic sensor that detects sound generated by the entrainment of bubbles and changes thereof, an imaging means that detects entrainment of bubbles as an image with a video camera or the like.

  By configuring as described above, when bubbles ejected from the gas ejection port are caught in the propeller means, the ejection conditions of the gas ejection port and / or the operating conditions of the air feeding means are changed to change the propeller of the bubbles. This reduces the entrainment of the means.

  The present invention also relates to a ship, a gas jet port for ejecting bubbles to at least the bottom of the ship, an air supply means for sending gas to the gas jet port, and a propeller provided on the stern side of the hull of the ship. And a bubble entrainment detecting means for detecting entrainment of bubbles in the propeller means. When the entrainment of bubbles is detected by the bubble entrainment detecting means, the operation condition of the propeller means is changed. You may make it do.

  By being configured as described above, when bubbles ejected from the gas outlet are caught in the propeller means, for example, the rotational speed is decreased, or the rotational speed is increased or variable to ensure propulsion. In the pitch propeller, the operating conditions of the propeller means are changed, such as changing the angle of the blades, to reduce the influence of bubble entrainment.

  According to the above configuration, since the bubbles sent from the air supply means are ejected from the gas outlet provided on the ship bottom, the rise of the bubbles is hindered by the ship bottom itself, and the bubble holding effect can be sustained, and effective with a small amount of bubbles. In addition, the frictional resistance can be reduced. In particular, when the ship is used in the ocean, the influence of the waves cannot be ignored, but the influence of the waves is mitigated at the bottom of the ship, and bubbles can be stably ejected. In addition, the entrainment prevention structure that prevents entrainment of air bubbles in the propeller means allows the air bubbles to escape without being affected by waves and tidal currents so that they are not entrained in the propeller means. Can be prevented, and the effect of reducing the net frictional force can be improved.

  Note that, in addition to the ejection of bubbles from the bottom of the ship, the same effect can be obtained by ejecting from other than the bottom of the ship. Further, the same effect can be obtained by providing an entrainment prevention structure other than the ship bottom.

  Further, according to the above configuration, since the bubbles are escaped by the raised portion having a curved surface which is an entrainment preventing structure and the bubbles are not caught in the propeller means, the efficiency of the propeller means and the propulsion force are prevented from being lowered. it can. Further, the raised portion having the curved surface can be configured with a simple structure and does not become an obstacle when entering the dock. In addition, since the flow along the bottom of the ship changes gently at the raised portion having a curved surface, it is possible to effectively prevent the entrainment of bubbles without increasing the frictional resistance of the hull. Further, since the streamline is directed downward at the raised portion having a curved surface and the flow velocity at the lower portion of the propeller means is lowered, improvement of propeller efficiency can be expected.

  Moreover, according to the said structure, since it can prevent that a bubble is caught in a propeller means by the V-shaped mound which spreads right and left centering | focusing on the plane centerline of the hull which is a protruding part, it was provided on the plane centerline It is possible to escape bubbles symmetrically and effectively with respect to the propeller means having a symmetric shape. Moreover, since the mound is V-shaped, the effect of escaping bubbles is further promoted, and an increase in the frictional resistance of the flow along the ship bottom can be prevented. Furthermore, since it is symmetrical, manufacturing is also easy.

  Further, according to the above configuration, only the bubbles reaching the vicinity of the propeller means are prevented from entering the propeller means by the bubble protector provided in the vicinity of the propeller means. For this reason, the entrainment of bubbles can be prevented without inhibiting the inflow of water into the propeller means.

  Further, according to the above configuration, the air bubble protector having a large number of apertures and provided in a substantially V shape has an aperture portion lower than the propeller means that is likely to entrain air bubbles with a substantially V-shaped flow velocity distribution. Can effectively prevent entrainment by acting as a resistance against bubbles. Further, since the air bubble protector has a large number of apertures and the substantially V-shaped upper part is vacant, the inflow of water into the propeller means is not hindered and the propulsion efficiency does not decrease.

According to the present invention, the air bubble sucking means provided in front of the propeller means sucks the air bubbles to be caught in the propeller means, and the rear part is raised from the bottom of the ship and the front part is formed slightly lower than the rear part. A curved surface capable of speeding up the water flow to separate the remaining portion of the bubbles from the bottom of the ship, further reducing the flow velocity of the lower part of the propeller means, while making the streamline of the water flow further downward from the bottom of the ship Since the air bubbles are prevented from reaching the propeller means portion by the entrainment preventing structure having the raised portions having the air bubbles, it is possible to surely prevent the air bubbles from being entrained. Furthermore, since the bubble suction means is provided in the vicinity of the propeller means, the effect of reducing friction due to the bubbles ejected to the ship bottom can be sufficiently exhibited.

  Further, according to the present invention, since the bubble suction means separates the bubbles sucked by the gas-liquid separation mechanism and the water, mixing of water into the bubble suction means such as a blower, a compressor or a pump is eliminated, Can be demonstrated stably. Moreover, the water separated by the gas-liquid separation mechanism can be used for other uses of the ship such as cooling water and anti-rolling tank.

In addition, according to the present invention, the rear part is raised from the bottom of the ship and the front part is formed to be slightly lower than the rear part in order to prevent entrainment of the air bubbles behind the air bubble suction means. It has a raised portion having a curved surface that separates the remaining portion of bubbles from the bottom of the ship , has a streamline of the water flow further downward from the bottom of the ship, and can slow down the flow velocity at the bottom of the propeller means. By providing the entrainment prevention structure, even if the unabsorbed bubbles flow out of the bubble suction means due to various disturbances, the entrapment prevention structure can reliably prevent the bubbles from being caught in the propeller means. In addition, for example, when the amount of bubbles is small, or depending on the state of the ship or the sailing state, it is possible to stop the bubble suction means and operate only the entanglement prevention structure, and it is possible to prevent the efficiency of the propeller means from being lowered and the propulsion force from being reduced more precisely.

  According to the above configuration, when the bubble entrainment detection means detects the entrainment of bubbles in the propeller means, the ejection conditions of the gas outlet and / or the operating conditions of the air supply means are changed, and therefore further entrainment of bubbles This can prevent the propeller efficiency from continuing to decline. Further, vibration and noise are prevented from occurring in the propeller means accompanying bubble entrainment, damage to the propeller means can be reduced, and harmful effects on the ship can be prevented.

  According to the above configuration, when the bubble entrainment detecting means detects the entrainment of bubbles in the propeller means, the propulsive force is reduced when the propeller propulsion power drops due to the entrainment of bubbles by changing the operating conditions of the propeller means. Therefore, it is possible to increase the rotational speed in order to maintain the above, or to decrease the rotational speed in order to reduce entrainment of bubbles. In addition, in order to prevent vibration and noise, in the case of variable pitch propellers, change the operating conditions of the propeller means, such as changing the blade angle and changing to a condition that has less effect on air bubbles, and entrain the bubbles. It is possible to reduce the influence of.

(a) A side view of a ship to which the device for preventing bubble entrainment in the first embodiment of the present invention is applied, (b) a top view of the ship, (c) a bottom view of the ship The perspective view of the air spout used for the bubble entrainment prevention apparatus of the ship in the 1st Embodiment of this invention The block diagram of the bubble entrainment prevention apparatus of the ship in the 1st Embodiment of this invention Action | operation conceptual diagram of the air jet used for the bubble entrainment prevention apparatus of the ship in the 1st Embodiment of this invention Flow rate distribution diagram of water in the propeller section of the ship in the first embodiment of the present invention The bottom view of the ship which applied the bubble entrainment prevention device of the ship in the 2nd embodiment of the present invention Sectional drawing of the principal part of the gas-liquid separation system used for the 2nd Embodiment of this invention The bottom view of the ship which applied the bubble entrainment prevention device of the ship in the 3rd embodiment of the present invention Conceptual diagram of operation of air inlet used in ship bubble entrainment prevention device in third embodiment of the present invention (a) A perspective view of a bubble protection plate used in a bubble entrainment prevention device for a ship in a fourth embodiment of the present invention, (b) a rear front view of the bubble protection plate

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the following, the range necessary for the description for achieving the object of the present invention is schematically shown, and the range necessary for the description of the relevant part of the present invention will be mainly described. Are according to known techniques.

(First embodiment)
FIG. 1 shows an example in which a ship bubble entrainment prevention device according to an embodiment of the present invention is applied to a ship used in the ocean. 1 (a) shows a side view of the ship, FIG. 1 (b) shows a top view thereof, and FIG. 1 (c) shows a bottom view. Let me express.

  Blowers 10, 11, 12, 13, and 14 as air supply means are installed side by side on the deck 2 of the ship 1, and the intake air is pressurized and air supply pipes 16, 17, and 18 having bent portions, respectively. , 19 and 20 are led to air jets 21, 22, 23, 24 and 25 which are gas jets installed in the vicinity of the ship bottom 3. In the case of this embodiment, the air jets 21, 22, 23, 24, 25 are arranged substantially in a line symmetrically with respect to the plane center line CL of the hull 4 at the front portion of the ship bottom 3. The provision of the air outlets 21, 22, 23, 24, 25 on the bottom 3 is for the purpose of prolonging the stay of the ejected bubbles on the bottom 3 and mitigating pressure fluctuations caused by waves or the like. Is provided for the purpose of allowing the ejected bubbles to stay on the bottom 3 as much as possible.

  The blowers 10, 11, 12, 13, and 14 are Roots type positive displacement blowers. Since they are positive displacement types, they can supply a fixed amount of air stably even if there is a pressure fluctuation. ing. Roots-type blower can pressurize air almost continuously, has less pulsation, smooth rotation, less vibration and noise, and is less likely to generate resonance in the lower cabin even when placed on deck 2 It has become.

  The ship bottom 3 has end plates 5, 5 ′, 6, 6 ′, 7, 7 ′ for guiding the bubbles so as not to escape the bubbles ejected from the air outlets 21, 22, 23, 24, 25. They are arranged symmetrically with respect to the plane center line CL of the hull 4. In addition, a shear force sensor 50, 51, 52, 53, 54 for detecting a shear force acting on the hull 4 due to seawater or bubbles is provided on the bottom 3 of the ship.

  Relative speed sensors 55 and 56 are provided on the stern side. Another relative speed sensor 57 is provided on the ship side 8. These relative velocity sensors 55 and 56 are separated from the air jets 21, 22, 23, 24, and 25, and the relative velocity sensor 57 is provided at a location where there is no influence of bubbles on the ship side 8 even when close. In particular, the relative speed sensor 57 is installed below the ship side 8 so as not to be affected by waves.

  Video cameras 58 and 59 for monitoring the state of the jetted bubbles are provided at the rear and front of the ship bottom 3. The images taken by the video cameras 58 and 59 are monitored by a person and are useful for analyzing the ejection state of bubbles.

  Here, the stern 9 of the hull 4 of the ship 1 is provided with a screw type propeller 80, and a rudder 81 is attached to the rear part thereof. Inside the hull 4, a thrust torque gauge 83 for detecting the thrust force and torque is attached to the drive shaft 82 of the propeller 80, and a vibration sensor 84 for detecting vibration is attached to the vicinity of the drive shaft 82. . This thrust torque gauge 83 is composed of a strain gauge provided on the surface of the drive shaft 82 of the propeller 80, and takes out a signal using radio so that the line does not get tangled because the drive shaft 82 rotates. . The vibration sensor 84 is provided in a bearing near the drive shaft 82 and electrically extracts vibration.

In addition, the ship bottom 3, as ridges bubble entrainment prevention structure, V-shaped Ma und 190 extending to the left and right around the planar center line CL of the hull 4 is provided, this mound wraps around to the ship's side 8 It is formed with a turn-in part 191.

  FIG. 2 is a perspective view conceptually showing the detailed structure of the air jets 21, 22, 23, 24, 25. In FIG. 2, representative examples of a plurality of air pipes and air outlets are shown for the sake of simplicity. The air sent from the blower 14 through the air supply pipe 16 is bent at a right angle in the chamber portion 70 of the air outlet 21 connected to the air supply pipe 16. A distribution part 71 having a triangular cross section for dispersing the supplied air is provided immediately below the connection portion of the air supply pipe 16 and is bent at a right angle at this part. The structure distributed right and left is taken, and the distribution of the air in the left-right direction of the porous plates 72 and 73 is made uniform.

  The perforated plates 72 and 73 are provided with a large number of holes 74 and 75, but the positions of the holes in the left and right directions are shifted between the perforated plates 72 and 73, and the positions of the apertures are shifted. By disposing the perforated plates 72 and 73 with their opening positions shifted, the perforated plates 72 and 73 act as a so-called baffle plate that bends the flow of air and adds resistance. In addition to the uniform air, the vertical air is also uniformed and can be ejected from the front ejection opening 76.

  FIG. 3 is a control block diagram of this embodiment.

  The ship state determination unit 100 includes a GPS 101 that detects the position of the ship, a fuel measurement unit 102 that measures the fuel consumption of the engine of the ship 1, and an engine operation detection unit 103 that detects the operating state of the engine of the ship 1. ing. This ship condition determination unit 100 is a part that particularly determines the current state of the ship, and determines the current state of the ship that changes little or slowly during navigation.

  The GPS 101 is used to determine at what position or place on the map the bubble should be ejected or stopped. The fuel measuring unit 102 is used for measuring how much fuel the engine consumes per predetermined time, and stopping the ejection of bubbles when the fuel consumption falls below a predetermined fuel consumption. The engine operation detection unit 103 detects various operation states including the start / stop of the engine of the ship 1, and when the operation of the engine is stopped, stops the ejection of bubbles or starts the operation and a predetermined time has passed. Then, it is used to obtain information such as the start of bubble ejection. It is also used for detecting the number of revolutions of the engine and changing the number of air jets and / or the amount of bubble ejection.

  The navigation state detection unit A110 includes relative speed sensors 55, 56, and 57, a draft sensor 111 that detects a draft level of the hull, and a tilt sensor 112 that detects a so-called rolling in the right and left directions with respect to the traveling direction of the hull. . Apart from this, the shear force sensors 51, 52, 53, 54, and 55 constitute the navigation state detection unit B115. The navigation state detection unit A and the navigation state detection unit B detect physical quantities that are relatively easily changed or controlled for the purpose of changing the vessel 1.

  The sea state determination unit 120 includes a wave sensor 121, a wind sensor 122, and a tidal current sensor 123. The wave sensor 121 detects the wave height, direction, period, and the like. The wind sensor 122 detects the wind speed and direction of the wind. The tidal current sensor 123 detects the tidal speed, direction, height, and the like of the tide. This sea state determination unit takes into account the weather, etc. in addition to other information such as general weather information, such as waves, winds, tides, etc. It is used to make decisions such as generating bubbles.

  Further, the entrainment detection unit 180 is provided with a shaft thrust / torque gauge 83 provided on the drive shaft 82 of the propeller 80 and a vibration sensor 84 provided near the drive shaft 83. It is detected by these gauges and sensors that air bubbles are trapped in the propeller 80, and at least the operating conditions and ejection conditions of the blowers 10, 11, 12, 13, 14 and the air ejection ports 21, 22, 23, 24, 25 are determined. It is used for changing or changing the operating conditions of the propeller 80.

  Such information of the ship state determination unit 100 and the information of the sea state determination unit 120 are transmitted to the condition setting unit 130, and conditions for jetting bubbles to the ship bottom 3 are set comprehensively by the condition setting unit. These conditions are: bubble start / stop, which of the plurality of air outlets 21, 22, 23, 24, and 25, which bubbles are to be ejected, what is the amount of ejection, what is the timing of ejection, In addition, how to form a temporal bubble jetting sequence, when to stop jetting, etc.

Note that, in this condition setting unit 130, ejection conditions of the air ejection port 21, 22 and blowers 10, 11, 12, 13 due to the air bubble entrainment, operating conditions and the propeller 80 operating conditions A control threshold value for the thrust / torque gauge 83 and the vibration sensor 84 is also set. In addition to threshold values, jetting conditions based on the detected values of the thrust / torque gauge 83 and the vibration sensor 84, setting conditions for operating conditions, setting conditions for changing the operating conditions of the propeller 80, setting combination conditions, setting correction conditions, etc. Done. The condition setting unit 130 also receives a condition setting instruction 131 for reducing frictional resistance and a condition setting instruction 131 for preventing bubble entrainment.

  In accordance with the setting of the condition setting unit 130, the comparison unit 140 compares signals, and the blowers 10, 11, 12, 13, 14 and the propeller 80 are controlled via the controller 150. The controller 150 also controls valves 161, 162, 163, 164, 165 provided on the discharge side of the blowers 10, 11, 12, 13, 14. These valves 161 and 162 are used when controlling the amount of air below the control range of the motors of the blowers 10, 11, 12, 13, and 14, and when adjusting the draft level quickly using the signal from the draft sensor 111. , 163, 164 and 165 are added for the purpose of obtaining a desired amount of air.

  Further, the comparison unit 140 compares the detection signals of the thrust / torque gauge 83 and the vibration sensor 84 of the entrainment detection unit 180 with the threshold values set by the condition setting unit 130. When it is determined that bubbles are entrained exceeding the threshold, the ejection conditions of the air ejection ports 21, 22, 23, 24, 25 and / or the operating conditions of the blowers 10, 11, 12, 13, 14 are changed. The ejection state is changed to a condition in which the propeller 80 does not easily entrain the bubbles. In addition, when it is determined that air bubbles have exceeded the threshold, the operating conditions of the propeller 80 are changed to prevent the propeller efficiency from continuing to decline, and vibration and noise are generated and the propeller 80 is damaged. Reduced. Further, depending on the situation, the driving conditions of the propeller 80 are changed to maintain the propulsive force. These bubble ejection conditions, blower operating conditions, and propeller operating conditions may be changed singly or in combination. The priority condition, the changing procedure, and the like follow a condition setting instruction 131 for reducing frictional resistance and a condition setting instruction 131 for preventing bubble entrainment.

  Further, the signals of the shear force sensors 51, 52, 53, 54, 55 attached to the ship bottom 3 are fed back to the comparison unit 140, compared with the shear force value set in advance by the condition setting unit 130, and according to the deviation. The operating states of the blowers 10, 11, 12, 13, and 14 are finely adjusted via the controller 150 in accordance with predetermined rules, algorithms, and constants. Further, the relative speed between the hull 4 and the seawater is detected by the relative speed sensors 55, 56, and 57, subjected to predetermined statistical processing, and the representative value is sent to the comparison unit 140. In addition, signals from the draft sensor 111 and the inclination sensor 112 are also sent to the comparison unit 140.

Further, in the comparison section 140, comparison between the processed representative value with a set value previously set by the condition setting portion 130 of the relative velocity sensors 55, 56, 57 is performed, the ejection talkative and bubbles ejected amount, bubbles The ejection pattern is controlled.

Further, the comparing section 140, and the value detected by the draft sensor 111, comparisons are made between the set value set in advance the condition setting unit 130, control of the ejection number of units and bubbles ejected amount in accordance with the draft of the hull 4 Is done. Further, when a large wave swells, the valves 161, 162, 163, 164, 165 are controlled to quickly increase / decrease the pressure applied to the air jets 21, 22, 23, 24, 25.

In addition, the comparison unit 140 compares the inclination value of the hull 4 detected by the inclination sensor 112 with the set value set in advance by the condition setting unit 130, and the right and left air jets according to the inclination of the hull 4. Effectively reducing the frictional resistance by changing the outlet jetting location or increasing / decreasing the bubble jetting amount.

  Now, bubble ejection and propeller operation control using signals from the entrainment detection unit 180 will be described. When the bubbles are wound around the propeller 80, the apparent density of the seawater on which the propeller 80 acts is reduced, resulting in a reduction in propulsive force, and the thrust force and torque of the propeller drive shaft 82 change. These changes are detected by a thrust torque gauge 83 attached to the drive shaft 82. In this case, one may be detected, but in the present embodiment, both are detected and output for improving accuracy. In addition, the vibration sensor 84 detects and processes the propeller 80 in a region where the bubble entrainment is in a predetermined amount, and outputs it as a signal. In this embodiment, both the thrust torque gauge 83 and the vibration sensor 84 are used, but one may be used.

  In this embodiment, the thrust / torque gauge 83 is mainly used and the vibration sensor 84 is used as a slave to complement it. These signals of the entrainment detection unit 180 are transmitted to the comparison unit 140.

The detected values of the thrust / torque gauge 83 and the vibration sensor 84 are also used as detection signals when cavitation occurs in the propeller 80. In comparing section 140, which is set by the condition setting unit 130, the thrust force, and the threshold of a set value of the torque, thrust force detected by the trapping detection unit 180, and the value of the torque is compared. Further, the threshold value set as the vibration set value set by the condition setting unit 130 is compared with the detection value detected by the vibration sensor 84. When any one of the three detection values falls below or exceeds the threshold value, the number and location of the bubble ejection ports and the ejection amount are controlled.

  This bubble ejection control is performed by controlling the air ejection ports 21, 22, 23, 24, 25, the blowers 10, 11, 12, 13, 14, and the valves 161, 162, 163, 164, 165. The basic idea is to change the bubble ejection conditions when the occurrence of entrainment of bubbles in the propeller 80 is detected. For example, the valve 161, 162, 163, 164, 165 is controlled to finely adjust the amount of bubbles, or the blower 10, 11, 12, 13, 14 is controlled to reduce the amount of bubbles and the bubbles are caught in the propeller 80. Is lost. Alternatively, by changing the outlets of the air outlets 21, 22, 23, 24, 25, for example, stopping the ejection of bubbles from the air outlet 23 located in the middle, or stopping the air outlets 22, 23, 24, etc. It is. These air jets 21, 22, 23, 24, 25, blowers 10, 11, 12, 13, 14, valves 161, 162, 163, 164, 165, and the number and location of jets, and the control of the jet quantity are all combinations. Although it is possible, an optimal combination is determined in advance based on simulation, model experiment, and demonstration experiment, and the optimum control condition is set by the condition setting unit 130.

  In these optimum controls, signals from the sea state determination unit 120 and the ship condition determination unit 100 are also used. For example, when the tidal current detected by the tidal current sensor 123 is from diagonally right to diagonally left with respect to the traveling direction of the ship 1, bubbles are also slightly swept away by the tidal current. Even if it is a condition that air bubbles are caught in the propeller 80 and the air outlets 22, 23, and 24 are stopped under normal conditions, the condition is changed to a condition that the air outlets 21 and 22 are stopped. For example, when the engine operation detection unit 103 detects that the output of the engine that drives the propeller 80 has been changed, the thrust force and torque of the propeller drive shaft 82 naturally change. The threshold value set by the condition setting unit is corrected. This makes it possible to evaluate the correct thrust force and torque against bubble entrainment.

  In any case, when the entrainment detector 180 detects entrainment of bubbles in the propeller 80, the air jets 21, 22, 23, 24, 25, the blowers 10, 11, 12, 13, 14, and the valve 161, 162, 163, 164, 165 are controlled, and the operating conditions such as the number and location of the jet outlets and the amount of bubble jetting are changed, preventing further bubble entrainment in the propeller 80 and continuing reduction in propeller efficiency. Can be prevented. Furthermore, vibration and noise are prevented from occurring in the propeller 80 due to entrainment of bubbles, damage to the propeller 80 can be reduced, and adverse effects as the ship 1 are also prevented. As described above, the bubble ejection control improves the detected values of thrust force, torque, and vibration, and the bubble ejection is returned to the original control state when all the detected values exceed or fall below the threshold value.

  Next, control for changing the operating conditions of the propeller 80 when bubble entrainment is detected will be described. When the detected value detected by the thrust / torque gauge 83 falls below the threshold value and bubbles are caught in the propeller, when the output-oriented control is performed, the engine output is increased and the propeller drive shaft 82 rotates. Raise the thrust force and torque. In this case, the propeller efficiency is lowered and the engine efficiency is usually lowered, but the output of the propeller 80 is maintained, and the hull speed and the like are not lowered. Under the characteristics and conditions where the engine efficiency does not decrease even if the engine speed increases, the operation can be continued without reducing the engine efficiency. When driving the propeller 80 with an emphasis on efficiency, the engine output is reduced, the rotation of the propeller drive shaft 82 is lowered, and the thrust force and torque are further reduced. As a result, the entrainment of bubbles in the propeller 80 is reduced, the propeller efficiency is recovered overall, and the thrust force and torque do not need to be reduced so much that vibrations and noise associated with entrainment of the bubbles can be prevented.

  In this way, by changing the operating conditions of the propeller 80, when the propulsion force of the propeller 80 drops due to bubble entrainment, the rotational speed is increased, or the rotational speed is decreased for measures against vibration and noise. The operating conditions can be changed to reduce the influence of entrainment of bubbles. When cavitation occurs in the propeller 80, the detected values of the thrust / torque gauge 83 and the vibration sensor 84 are used to suppress the generation of vibration and noise in the propeller 80 and to prevent the propeller 80 from being damaged.

  Here, the operation of the V-shaped mound 190 and the wrap-around part 191 will be described.

  Bubbles ejected from the air ejection ports 21, 22, 23, 24, 25 to the ship bottom 3 flow along the ship bottom 3, and are guided by the end plates 5, 5 ′, 6, 6 ′, 7, 7 ′. Some rise to sea level along ship side 8. As the ship bottom 3 approaches the side of the propeller 80, the ship bottom 3 gradually narrows and the ship side 8 gradually begins to tilt. A part of the air bubbles flowing from the upstream along the inclined surface enter the inclined ship side 3 and rise to the water surface, but a considerable amount still flows along the ship bottom 3. When the bubbles reach the V-shaped mound 190, the V-shaped mound 190 moves away from the ship bottom 3 as shown in FIG. This is because the shape of the V-shaped mound 190 has a structure in which the front is slightly low and the rear is raised, and the air bubbles are separated from the ship bottom 3 by continuing gently. Bubbles that have circulated toward the ship side 3 at the V-shaped mound 190 part are guided toward the water surface by the wrap-around part 191 having a similar ridge, and are further prevented from flowing along the ship side 3 toward the propeller 80 side. The

  FIG. 5 shows the flow situation near the propeller 80. FIG. 5 shows how the flow velocity around the propeller 80 is distributed with respect to the navigation speed of the ship 1, and is a line that is 10%, 20%, and 30% slower than the navigation speed. Is expressed as a constant velocity line. As is apparent from FIG. 5, the flow velocity around the propeller 80 is distributed in a substantially V shape, and is faster at the lower part of the propeller 80 and slower at the upper part. The lower the flow velocity acting on the propeller 80 in the propulsion of the ship 1, the better the efficiency. However, comparing the upper and lower portions of the propeller 80, it can be said that the upper region is effective in terms of propulsion. On the other hand, as an action of the bubbles, the bubbles escape as a phenomenon in which the water pressure is low. When the flow is fast, the dynamic pressure increases and the static pressure decreases according to Bernoulli's theorem. That is, when compared at the same water depth level, it can be said that bubbles are likely to collect at a high flow velocity and escape easily at a low flow velocity.

As an action of the V-shaped mound 190, the V-shaped mound 190 has an action of separating the bubbles from the ship bottom 3 and causing the streamline to be further directed downward from the ship bottom 3 to slow down the flow velocity under the propeller 80. For this reason, the presence of the V-shaped mound 190 has the effect of separating the bubbles from the ship bottom 3 and wrapping around the ship side 8 quickly. Further, since the flow velocity in the lower part of the propeller 80 is slowed, the effect of making it difficult for bubbles to enter the propeller 80 and the effect of increasing the propulsion force of the propeller 80 are exhibited. Further, since the V-shaped mound is formed so as to spread left and right around the plane center line CL of the hull 4, it is symmetrical with respect to the symmetric propeller 80 provided on the plane center line CL. Bubbles can be effectively released. Moreover, since the mound is substantially V-shaped, it is possible to further prevent an increase in frictional resistance against the hull 4 of the flow along the ship bottom 3. Furthermore, since it is symmetrical, manufacturing is also easy. Further, as the utility of the mound, since the mound can be formed as a raised portion with a strength member on the bottom 3 of the ship, the work can proceed without any trouble when it is put on the pedestal when the ship 1 is docked. Further, by configuring the V-shaped mound 190 with a strength member, the strength in the front-rear direction of the ship bottom 3 increases, and the hull structure is strong against bending due to repeated wave forces (sagging, hogging) on the ship 1. It can be.
(Second Embodiment)

  FIG. 6 shows a second embodiment of the present invention. In the second embodiment, only differences from the first embodiment will be described, and the other parts will have the same configuration as that of the first embodiment.

  In FIG. 6, air jets 21, 22, 23, 24, and 25 for jetting bubbles are arranged on the bottom 3 of the ship 1. On the other hand, a bubble suction port 85 is provided in front of a propeller 80 provided at the stern 9 of the hull 4 for sucking seawater mixed with bubbles. Details of this part are shown in FIG. 7 together with a gas-liquid separator.

  In FIG. 7, a gas-liquid separation chamber 86 that is a gas-liquid separation mechanism is formed inside the bubble suction port 85 provided on the ship bottom 3, and seawater mixed with bubbles sucked from the bubble suction port 85 The gas-liquid separation chamber 86 is entered via the body 87. The gas-liquid separation chamber 86 is formed with a sufficient volume, and the seawater mixed with bubbles that has flowed in is sufficiently decelerated, so that the bubbles rise and accumulate in the upper part as air. In this gas-liquid separation chamber 86, air is taken out from the air connection pipe 88 through the air valve 89 to discharge the air accumulated in the upper part by the blower 90 to the outside without causing the propeller 80 to re-entrain in the atmosphere or the like. A tube 91 is connected. In addition, an air discharge pipe 92 that draws air to the atmosphere is connected to the upper part, and this air discharge pipe 92 is also provided with an air valve 89 '. In addition, a bubble separation filter 93 having porosity is provided at the lower part of the gas-liquid separation chamber 86, and the bubbles that have not been raised are further separated by the porous resistance action. The seawater from which the bubbles have been separated is sucked by the pump 96 from the water take-out pipe 94 through the water valve 95, and is sent to the ship 1 as cooling water or anti-rolling tank applications through the water pipe 97. Further, the gas-liquid separation chamber 86 is provided with a water level sensor 98 for detecting the water level, and the rotational speed of the blower 90 is controlled so as to provide a constant air reservoir in the upper part. The blower 90 is made of a volume-type and corrosion-resistant material that can supply air even in bubbles mixed with seawater. The air connection pipe 88 faces below the upper surface of the gas-liquid separation chamber 86 to which the air discharge pipe 92 is connected, and air remains in the upper part even when the balance of the pump 96 and the blower 90 is lost. The pressure pulsation during operation of the pump 96 is absorbed. The bubble separation filter 93 is formed to have a conical shape and is installed obliquely when viewed in cross section, so that the bubble separation effect is high, and foreign matter from the ocean enters the pump 96 and the pipe 97. Can also be prevented. A bubble suction system is constituted by the bubble suction port 85, the gas-liquid separation chamber 86, the blower 90, the pump 96, and the like.

  By being configured in this manner, the bubbles sucked into the propeller 80 are sucked in front by the bubble suction port 85 provided in front of the propeller 80, and it is ensured that the bubbles do not reach the propeller 80 portion. The decline is prevented. Further, since the air bubble suction port 85 is provided in the vicinity of the propeller 80, the air bubbles are sucked in after being sufficiently exerted the friction reducing effect by the air bubbles ejected to the ship bottom 3, and discharged to the outside not causing re-entrainment. The friction reducing effect can be sufficiently exhibited. Also, in the event of trouble with either the blower 90 or the pump 96 of the bubble suction system, a certain amount of bubbles can be prevented by closing the valve of the system and opening the air valve 89 'of the air discharge pipe 92.

Further, since the seawater mixed with bubbles sucked from the bubble suction port 85 is separated into the bubbles sucked by the gas-liquid separator 86 and the water, the mixing of water into the blower 90 and the pump 96 is eliminated, and the function is stabilized. Can demonstrate. Further, the water separated by the gas-liquid separator 86 can be used for other uses of the ship 1 such as cooling water and makeup water for the anti-rolling tank.
(Third embodiment)

  8 and 9 show an example of the third embodiment of the present invention. The third embodiment is an example in which the previous V-shaped mound and the bubble suction system are combined.

  However, in the third embodiment, the bubble suction port 99 is disposed in a substantially V shape in accordance with the V-shaped mound 190 and in front of the V-shaped mound 190 as shown in FIG.

FIG. 9 shows details of the operation. By providing a V-shaped mound 190 that prevents the entrainment of bubbles behind the bubble suction port 99, the bubbles are released by the V-shaped mound 190 even if unsucked bubbles flow out of the bubble suction port 99 due to various disturbances. Entanglement to the propeller 80 can be reliably prevented. In addition, when the amount of bubbles is small, the blower 90 and the pump 96 can be stopped and only the V-shaped mound 190 can be operated depending on the state of the ship 1 and the navigation state, and further, the effect of reducing the fine net frictional force can be enhanced. it can. By providing the V-shaped mound 190 in the vicinity of the rear of the bubble suction port 99, in addition to the effect of the V-shaped mound 190 described above, the flow velocity drops in front of the V-shaped mound 190 , so that the bubbles are released. This has the effect of facilitating the sucking of the escaped bubbles from the bubble suction port 99.
(Fourth embodiment)

  FIG. 10 shows a fourth embodiment of the present invention. FIG. 10 (a) is a perspective view thereof, and FIG. 10 (b) is a front view of the rear portion thereof. Bubble protection plates 200 and 201 are provided symmetrically on the stern propeller mounting portion 9 ′ so as to spread in a substantially V shape from the boat bottom extension 3 ′ when viewed from the rear. The bubble protection plates 200 and 201 are also fixed to the ship side extension 8 ′ and are formed so as to spread toward the rear propeller 80. A large number of round holes 202 are formed in the bubble protection plate, and the bubbles that are ejected from the air ejection ports 21, 22, 23, 24, and 25, flow from the upstream side, and are likely to be sucked into the propeller 80. Is obstructed by the resistance of the bubble protection plates 200 and 201 and spreads around the propeller 80 along the shape of the bubble protection plates 200 and 201. On the other hand, when the propeller 80 rotates, the seawater enters the inside of the bubble protection plates 200 and 201 from the many round holes 202 opened in the bubble protection plates 200 and 201, and reaches the propeller 80. In this case, the flow velocity distribution in the lower portion of the propeller is slightly slower due to the presence of the bubble protection plates 200 and 201 than when the bubble protection plates 200 and 201 are not provided. As a result, it is possible to operate efficiently as a whole.

  In this way, the bubble protection plates 200 and 201 allow the bubbles to escape to the outside of the propeller 80, flow down the flow velocity of the seawater flowing along the hull 4, and slow the flow velocity distribution around the propeller 80. Accordingly, the flow velocity distribution in the lower portion of the propeller becomes slow, and the propeller efficiency is increased. In addition, the hole 202 may not be provided for the purpose of causing the bubbles to escape with the bubble protection plates 200 and 201 and preventing the efficiency of the propeller 80 from decreasing. Further, it may extend further upward and further rearward, or may be shortened further downward and further forward. In any case, the presence of the bubble protection plates 200 and 201 makes it possible to reduce the amount of bubbles entrained in the propeller 80, and to prevent the propeller propulsion efficiency from being lowered, even if there is a difference in degree. The meaning that a large number of round holes 202 are opened in the bubble protection plates 200 and 201 is that the shape having an edge portion such as a square hole is used. This is because stress corrosion is likely to occur due to residual stress in the part. As a countermeasure, a round hole with little residual stress at the time of pressing is formed. Further, since the air bubble protection plates 200 and 201 are provided at a place where the flow velocity in front of the propeller 80 is fast, entanglement of marine suspended matters and algae with the propeller 80 can be prevented.

  The effect in each embodiment as described above will be described below.

  First, air is supplied to the ship 1, the air outlets 21, 22, 23, 24, 25 that blow out bubbles to at least the bottom 3 of the ship 1, and the air outlets 21, 22, 23, 24, 25. To the blower 10, 11, 12, 13, 14, propeller 80 provided on the stern 9 of the hull 4 of the ship 1, and at least the bottom 3 on the stern side behind the air outlets 21, 22, 23, 24, 25 A substantially V-shaped mound 190 that prevents air bubbles from getting into the propeller 80 is provided.

  With such a configuration, the rising of the bubbles is hindered by the ship bottom 3 itself and the effect of holding the bubbles can be maintained, and the frictional resistance can be effectively reduced with a small amount of bubbles. In addition, the air jets 21, 22, 23, 24, and 25 provided on the ship bottom 3 are less affected by waves compared to the case provided on the ship side, which can lead to a stable frictional resistance reduction effect of the hull 4. it can. In particular, the substantially V-shaped mound 190 separates bubbles flowing along the ship bottom 3 from the ship bottom 3 to prevent inflow into the propeller 80, and the substantially V-shaped mound 190 slows down the flow velocity below the propeller 80. In addition, re-entrainment of bubbles is unlikely to occur and the propeller propulsive force can be improved. In particular, the shape of the substantially V-shaped mound 190 has a structure in which the front is slightly low and the rear is raised, and these effects are remarkable due to the gentle continuation.

  Moreover, since the substantially V-shaped mound 190 can be formed as a raised portion with a strength member on the ship bottom 3, there is no trouble in placing it on the pedestal when the ship 1 is docked, and the work can be facilitated.

  In addition, since the mound is substantially V-shaped, the strength of the ship bottom 3 increases with the strength member, and the mound is strong against bending due to repeated wave forces applied to the ship 1. It can be a hull structure.

  Further, by providing the bubble protection plates 200 and 201 in the vicinity of the propeller 80 at a place with a fast flow velocity in front, the entanglement of marine suspended matters and algae with the propeller 80 can be prevented.

  Further, by forming the bubble protection plates 200 and 201 with a stainless porous plate having a round hole having corrosion resistance against seawater, the occurrence of stress corrosion due to the residual stress at the edge portion can be reduced and the corrosion resistance can be increased.

  In addition, a bubble suction port 85 for sucking at least bubbles is provided in front of the propeller 80 at the rear of the air jets 21, 22, 23, 24, 25, and the bubbles trapped in the propeller 80 are sucked in front. Since it does not reach and the sucked bubbles are discharged to the atmosphere or the outside where re-entrainment does not occur, entrainment can be surely prevented. Further, since the air bubble suction port 85 is provided in the vicinity of the propeller 80, the air blown into the blower 90 and the pump while reliably reducing the frictional resistance by sucking the air bubbles after sufficiently exerting the friction reducing effect by the air bubbles ejected to the ship bottom 3. In the case of 96 troubles, by opening the air valve 89 ′ of the air discharge pipe 92, it is possible to prevent entrainment of bubbles to some extent.

  In addition, the bubble separation filter 93 having a porosity provided in the lower part of the gas-liquid separation chamber 86 can enhance the separation effect of the bubbles and can prevent foreign matters from entering the pump 96 and the pipe 97 from the ocean.

Further, by providing a substantially V-shaped mound 190 in the vicinity of the rear of the bubble suction port 99, the flow velocity drops in front of the substantially V-shaped mound 190 , so that the bubbles are released and the escaped bubbles are sucked from the bubble suction port 99. It can be made easier.

  Further, a thrust torque gauge 83 and a vibration sensor 84 for detecting the entrainment of bubbles in the propeller 80 are provided, and when the entrainment of bubbles is detected by these gauges and sensors, the air outlets 21, 22, 23, 24, 25 are provided. Since the jetting conditions and / or the operating conditions of the blowers 10, 11, 12, 13, and 14 are changed, further bubble entrainment can be prevented and the reduction in the efficiency of the propeller 80 can be prevented from continuing. Furthermore, vibration and noise are prevented from occurring in the propeller 80 due to entrainment of bubbles, damage to the propeller 80 can be reduced, and adverse effects as the ship 1 are also prevented.

  Further, when the entrainment of bubbles is detected by the thrust torque gauge 83 or the vibration sensor 84 that detects entrainment of bubbles in the propeller 80, the driving conditions of the propeller 80 are changed, and therefore the propulsive force of the propeller 80 is accompanied by entrainment of bubbles. Is reduced, the rotational speed is increased, or the rotational speed is decreased for vibration and noise countermeasures, thereby increasing the frictional force reduction effect and preventing adverse effects on the navigation of the ship 1. Further, when cavitation occurs, the detected values of the thrust / torque gauge 83 and the vibration sensor 84 are used to suppress the generation of vibration and noise in the propeller 80 and to prevent the propeller 80 from being damaged.

  The ship bubble entrainment prevention apparatus according to the present invention is not limited to use in general oceans, but is used for propeller means in applications for reducing frictional resistance by ship bubble ejection methods used in all water systems such as rivers and lakes. It can be used for countermeasures against bubble entrainment.

  In addition, it can be widely applied to the application of frictional resistance reduction by bubble ejection methods such as navigating bodies, floating bodies, etc. that do not take the shape of a ship, solving problems such as reduced efficiency of propeller means due to bubble entrainment, vibration, noise, In terms of achieving energy conservation in ships, it will bring great benefits to society as a whole and various industries in general.

DESCRIPTION OF SYMBOLS 1 ... Ship, 3 ... Ship bottom, 11, 12, 13, 14, 15 ... Blower (air supply means), 21, 22, 23, 24, 25 ... Air jet (gas jet), 80 ... Propeller (propeller means) , 85 ... Bubble suction port (bubble suction means), 86 ... Gas-liquid separation chamber (bubble suction means, gas-liquid separation mechanism), 90 ... Blower (bubble suction means), 96 ... Pump (bubble suction means), 190 ... V-shaped mound (anti-entrainment structure), 200, 201 ... bubble protection plate (bubble protection body)

Claims (5)

A gas outlet for ejecting bubbles at least to the bottom of the ship, an air supply means for supplying gas to the gas outlet, a propeller means provided at the stern of the hull of the ship, and the rear of the gas outlet A bubble suction means for sucking the bubbles together with water provided in front of the propeller means, and a rear portion raised from the bottom of the ship and a front portion formed slightly lower than the rear portion provided behind the bubble suction means; It has a curved surface that speeds up the water flow and separates the remaining portion of the bubbles from the bottom of the ship, and makes the streamline of the water flow further downward from the bottom of the ship and slows down the flow velocity at the bottom of the propeller means. A device for preventing bubble entrainment in a ship, comprising an entrainment prevention structure having a raised portion.   2. The bubble entrainment prevention device for a ship according to claim 1, wherein the bubble suction port of the bubble suction means is provided substantially symmetrically with respect to a plane center line CL of the hull. Vessels bubble entrainment prevention device according to claim 1 or claim 2, wherein the draining the bubble sucked by the air bubble suction section to the atmosphere does not cause re-entrainment of the air bubbles into the front Symbol propeller.   4. The apparatus for preventing bubble entrainment in a ship according to claim 1, wherein the bubble suction means has a gas-liquid separation mechanism that separates the sucked bubbles and the water. 5.   5. The apparatus for preventing entrainment of bubbles in a ship according to claim 4, wherein the water separated by the gas-liquid separation mechanism is used for inboard use including cooling water for the ship or makeup water for an anti-rolling tank.