Method for controlling rotation speed of propeller for ship to reduce cavitation

Abstract

According to the present invention, when cavitation occurs in a ship in operation, a propeller rotation angle region corresponding to a cavitation occurrence section is identified, and the rotation speed of a propeller is increased or decreased in the identified propeller rotation angle region corresponding to the cavitation occurrence section such that the cavitation can be controlled to be reduced. Therefore, the cavitation can be reduced simply by controlling the rotation speed of the propeller without changing the structure of the propeller.

Description

Method for controlling the rotation speed of a ship propeller to reduce cavitation

[0001] The present invention relates to a method for controlling the rotation speed of a ship propeller to reduce cavitation, and more particularly, to a control method for reducing cavitation by identifying a propeller rotation angle region corresponding to a cavitation occurrence section when cavitation occurs in a ship in operation and increasing or decreasing the rotation speed of the propeller in the identified propeller rotation angle region corresponding to the cavitation occurrence section.

[0002]

[0003] In modern society, thanks to the development of industry and transportation, more people and goods are moving around than in the past.

[0004] In particular, in our country, which is bordered by the sea on three sides, most of the goods are imported and exported through the sea, and large ships are operated to import and export goods, and the ships are operated using the propulsion power generated by rotating the ship's propeller.

[0005] At this time, swirling air bubbles are created around the propeller rotating underwater. This phenomenon is called cavitation, and cavitation is the main cause of noise and hull vibration.

[0006] In particular, noise and hull vibration caused by cavitation have a negative impact on the ship, which reduces the durability of the ship and, in severe cases, can damage the propeller and cause a ship accident, so there is a need to reduce cavitation.

[0007] Additionally, in the case of military vessels such as naval ships or submarines, the need to reduce cavitation is even greater because the noise generated by military vessels acts as a factor that exposes their location to the enemy.

[0008] In the past, cavitation-reducing propellers were developed by improving the structure of the blades that make up the propeller. However, although the conventional cavitation-reducing propellers with improved blade structures have the effect of reducing cavitation, they also have the disadvantage of weakening propulsive power due to structural changes.

[0009] Therefore, it will be necessary to develop a method to reduce cavitation without changing the structure of the propeller so that the thrust is not reduced.

[0010] Accordingly, the present invention is intended to address the above-mentioned necessity and to solve the conventional problems, and proposes a control method for reducing cavitation by identifying a propeller rotation angle region corresponding to a cavitation occurrence section when cavitation occurs in a ship in operation and increasing or decreasing the rotation speed of the propeller in the identified propeller rotation angle region corresponding to the cavitation occurrence section. The following are prior art techniques related to this.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 0001) 1. Republic of Korea Patent Publication No. 10-2012-0008497 Device and method for controlling ship vibration due to variable pressure of propeller

[0014] (Patent Document 0002) 2. Republic of Korea Utility Model Registration No. 20-0480458 Propeller Cavitation Phenomenon Observation Blade Angle Adjustment Device

[0015] (Patent Document 0003) 3. Republic of Korea Patent Publication No. 10-2111521 Compressed air injection current fixed blade and cavitation damage prevention system of propeller using the compressed air injection current fixed blade

[0016]

[0017] The purpose of the present invention is to identify a propeller rotation angle region corresponding to a cavitation occurrence section when cavitation occurs in a ship in operation, and to control the rotation speed of the propeller to reduce cavitation by increasing or decreasing it in the propeller rotation angle region corresponding to the identified cavitation occurrence section.

[0018]

[0019] In order to achieve the above purpose, the present invention provides a method for controlling the rotation speed of a ship propeller to reduce cavitation.

[0020] A first step (S100) of generating cavitation information regarding cavitation occurring when the propeller (1) rotates;

[0021] After generating cavitation information, the second step (S200) is to measure the rotation angle of the propeller (1) in real time;

[0022] A third step (S300) for changing the rotation speed of a ship propeller to reduce cavitation occurrence by using the cavitation information generated through the first step (S100) and the propeller rotation angle information measured in real time through the second step (S200),

[0023] The above cavitation information is characterized in that it includes information on the propeller rotation angle when cavitation occurs.

[0024]

[0025] The present invention can control to reduce cavitation by identifying a propeller rotation angle region corresponding to a cavitation generation region when cavitation occurs in a ship in operation and increasing or decreasing the rotation speed of the propeller in the identified cavitation generation region, thereby providing an effect of reducing cavitation simply by controlling the rotation speed of the propeller without changing the structure of the propeller.

[0026]

[0027] Figure 1 is a conceptual diagram of the present invention.

[0028] Figure 2 is a configuration flowchart of the present invention.

[0029] Figures 3a to 3c are exemplary diagrams illustrating the first step of the present invention.

[0030] Figures 4a and 4b are exemplary diagrams illustrating the first step of the present invention.

[0031] Figures 5a and 5b are exemplary diagrams illustrating the second step of the present invention.

[0032]

[0033] An embodiment of the present invention is described in detail with reference to the attached drawings.

[0034] The present invention relates to a method for controlling the rotation speed of a ship propeller for reducing cavitation (hereinafter referred to as the present invention), which, when cavitation occurs in a ship in operation, identifies a propeller rotation angle region corresponding to a cavitation occurrence section, and controls the rotation speed of the propeller to increase or decrease in the propeller rotation angle region corresponding to the identified cavitation occurrence section so as to reduce cavitation, thereby providing an effect of reducing cavitation simply by controlling the rotation speed of the propeller without changing the structure of the propeller.

[0035] Specifically, the method for controlling the rotation speed of a ship propeller for reducing cavitation according to the present invention is as shown in FIGS. 1 and 2.

[0036] A first step (S100) of generating cavitation information regarding cavitation occurring when the propeller (1) rotates;

[0037] After generating cavitation information, the second step (S200) is to measure the rotation angle of the propeller (1) in real time;

[0038] A third step (S300) for changing the rotation speed of a ship propeller to reduce cavitation occurrence by using the cavitation information generated through the first step (S100) and the propeller rotation angle information measured in real time through the second step (S200),

[0039] The above cavitation information is characterized in that it includes information on the propeller rotation angle when cavitation occurs.

[0040] When a propeller rotates underwater, swirling air bubbles form on the blade surface. This phenomenon is called cavitation, and cavitation is the main cause of noise and hull vibration.

[0041] At this time, the noise and hull vibration generated by cavitation have a negative effect on the ship, which reduces the durability of the ship, and if cavitation is severe, it can damage the propeller and cause a ship accident. In addition, in the case of military ships such as naval ships or submarines, the noise generated by the military ship acts as a factor that exposes the ship's location to the enemy, so there is a need to reduce cavitation.

[0042] In particular, cavitation does not occur in all rotation angle ranges of a rotating propeller, but occurs in some rotation angle ranges. The present invention generates cavitation information including information on the rotation angle of a propeller when cavitation occurs through the first step (S100), measures the rotation angle of a propeller (1) in real time through the second step (S200), and reduces cavitation by adjusting the rotation speed of the propeller using the cavitation information and the real-time measured propeller rotation angle information through the third step (S300).

[0043] The present invention, which controls the rotation speed of a ship propeller for reducing cavitation, is achieved through a control device consisting of a cavitation information generation unit (100) and a rotation speed control unit (200) installed on a ship, as illustrated in Fig. 1. That is, the cavitation information generation unit (100) is the entity that performs the first step (S100) and the second step (S200) of the present invention, and the rotation speed control unit (200) is the entity that performs the third step (S300) of the present invention.

[0044] The above cavitation information generation unit (100) is configured to generate cavitation information regarding cavitation that occurs when a ship propeller (1) rotates, and to provide the generated cavitation information and propeller rotation angle information to a rotation speed control unit (200). The unit includes a pressure detection unit (110) that measures the fluctuating pressure applied to the rear of a ship located underwater due to cavitation that occurs on the surface of a propeller blade (2) when the ship propeller (1) rotates, a rotation angle measuring unit (120) that measures the rotation angle of a rotating propeller, and a data processing unit (130) that generates cavitation information using the fluctuating pressure information and the propeller rotation angle information.

[0045] In addition, the rotation speed control unit (200) is configured to change the rotation speed of a ship propeller (1) using cavitation information and propeller rotation angle information provided by a cavitation information generation unit (100), and is configured to include an information receiving module (210) that receives cavitation information and propeller rotation angle information from the cavitation information generation unit (100), a control information generation module (220) that calculates speed control information, and a speed control module (230) that changes the rotation speed of the ship propeller.

[0046] The first step (S100) above is a step for generating cavitation information regarding cavitation that occurs when the propeller (1) rotates. The cavitation information generated through the first step (S100) includes information regarding the propeller rotation angle at the time of cavitation occurrence, and the first step (S100) is performed through a cavitation information generating unit (100).

[0047] Specifically, the first step (S100) is, as illustrated in FIG. 2,

[0048] Step 1-1 (S110) of measuring the fluctuating pressure applied to the rear of a ship located underwater due to cavitation occurring on the surface of the propeller blade (2) when the propeller (1) rotates;

[0049] To generate cavitation information, the first and second steps (S120) measure the rotation angle of the rotating propeller,

[0050] It is characterized by including steps 1-3 (S130) of generating cavitation information using information on the fluctuating pressure applied to the measured stern of a ship and information on the rotation angle of the measured propeller.

[0051] The above 1-1 step (S110) is a step for measuring the variable pressure applied to the stern of a ship located underwater due to cavitation occurring on the surface of a propeller blade (2) when the propeller (1) rotates, and specifically, it is characterized by measuring the first variable pressure applied to the stern of a ship located underwater on the side where the descending propeller blade (2) is located due to cavitation occurring on the surface of the descending propeller blade (2) when the propeller (1) rotates, and the second variable pressure applied to the stern of a ship located underwater on the side where the rising propeller blade (2) is located due to cavitation occurring on the surface of the rising propeller blade (2).

[0052] When a ship propeller (1) rotates underwater, the velocity of water flowing along the surface of the propeller blade (2) constituting the ship propeller (1) increases compared to when the propeller is stationary, and as the velocity increases, the pressure applied to the surface of the blade (2) decreases according to Bernoulli's equation, and as the pressure decreases, swirling air bubbles, which are air bubbles, are generated on the surface of the blade (2), which is called cavitation.

[0053] At this time, when cavitation occurs, the flow of water changes due to cavitation, and the change in water flow causes a change in pressure applied to the stern of the ship.

[0054] That is, when cavitation occurs, a greater pressure is applied to the stern of the ship than would be applied to the stern if cavitation did not occur.

[0055] In order to detect the pressure applied to the stern of a ship, as shown in FIGS. 3a to 3c, a first pressure detection sensor (111) is installed on one side of the stern surface of the ship located underwater on the side where the propeller blade (2) that descends while rotating is located, above the propeller (1), and a second pressure detection sensor (112) is installed on one side of the stern surface of the ship located underwater on the side where the propeller blade (2) that ascends while rotating is located, above the propeller (1).

[0056] As illustrated in FIG. 3a, the first pressure detection sensor (111) measures the first variable pressure, which is the pressure applied to the stern of the ship (the stern of the ship located underwater on the side where the descending propeller blade (2) is located) due to cavitation occurring on the surface of the descending propeller blade (2) among the rotating blades (2), and provides the measured first variable pressure information (see FIG. 3a) to the data processing unit (130).

[0057] As illustrated in FIG. 3b, the second pressure detection sensor (112) measures the second variable pressure, which is the pressure applied to the stern of the ship (the stern of the ship located underwater on the side where the rising propeller blade (2) is located) due to cavitation occurring on the surface of the rising propeller blade (2) among the rotating blades (2), and provides the measured second variable pressure information (see FIG. 3b) to the data processing unit (130).

[0058] Therefore, through the above step 1-1 (S110), the change in pressure applied to the stern of the ship is detected to determine whether cavitation has occurred.

[0059] The above 1-2 steps (S120) are steps for measuring the rotation angle of a rotating propeller to generate cavitation information, and the rotation angle of the rotating propeller is measured through a rotation angle measuring device (120) installed on the propeller.

[0060] At this time, the rotation angle measuring device (120) measures the rotation angle of the rotating propeller (1) in real time and provides the measured propeller rotation angle information (see FIG. 3c) to the data processing unit (130) and the rotation speed control unit (200).

[0061] That is, when generating cavitation information, the rotation angle measuring device (120) provides propeller rotation angle information (see FIG. 3c) measured in real time to the data processing unit (130), and after generating cavitation information, when controlling propeller rotation, it provides propeller rotation angle information (see FIG. 3c) measured in real time to the rotation speed control unit (200).

[0062] The above 1-3 steps (S130) are steps for generating cavitation information using the measured pressure fluctuation information applied to the stern of the ship and the measured rotation angle information of the propeller.

[0063] Specifically, the first-third step (S130) synchronizes the first variable pressure information and the rotation angle information of the propeller applied to the stern of the ship located underwater on the side where the descending propeller blade (2) is located due to cavitation occurring on the surface of the descending propeller blade (2) when the propeller (1) rotates, and generates first cavitation information regarding cavitation occurring on the side where the descending propeller blade (2) is located, using the time-synchronized first variable pressure information and the rotation angle information of the propeller, and synchronizes the second variable pressure information and the rotation angle information of the propeller applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) is located due to cavitation occurring on the surface of the ascending propeller blade (2) when the propeller (1) rotates, and generates second cavitation information regarding cavitation occurring on the side where the ascending propeller blade (2) is located, using the time-synchronized second variable pressure information and the rotation angle information of the propeller. It is characterized by generating cavitation information including first cavitation information and second cavitation information.

[0064] Steps 1-3 (S130) of generating cavitation information are performed by a data processing unit (130) installed inside the ship.

[0065] Below, the first cavitation information generation is described.

[0066] Step 1-3 (S130) performed through the data processing unit (130) is characterized by time-synchronizing the first variable pressure information provided by the first pressure detection sensor (111) of the pressure detection unit (110) and the propeller rotation angle information provided by the rotation angle measuring device (120), and generating the first cavitation information using the time-synchronized first variable pressure information and the propeller rotation angle information.

[0067] At this time, the first cavitation information is characterized in that it is propeller rotation angle area information when the pressure applied to the rear of the ship located underwater on the side where the descending propeller blade (2) is located is equal to or greater than a set value, or propeller rotation angle information when it is at a peak value. That is, the first cavitation information has two embodiments.

[0068] Below, a first embodiment of first cavitation information generation is described.

[0069] Figure 4a is an example diagram showing time synchronization of first variable pressure information provided by a first pressure detection sensor (111) and propeller rotation angle information provided by a rotation angle measuring device (120).

[0070] The above 1-3 step (S130) uses time-synchronized information (see FIG. 4a) of the first variable pressure information provided by the first pressure detection sensor (111) and the propeller rotation angle information provided by the rotation angle measuring device (120), to identify the propeller rotation angle area when the pressure applied to the rear of the ship located underwater on the side where the descending propeller blade (2) is located is greater than a set value, and generates the identified propeller rotation angle area information as first cavitation information.

[0071] For example, in Fig. 4a, the propeller rotation angle area is determined to be a region where the pressure applied to the rear of the ship located underwater on the side where the propeller blade (2) descending in the 20 to 40 degree region is greater than the set value, and the information on the identified propeller rotation angle area of ​​20 to 40 degrees is generated as first cavitation information.

[0072] When cavitation occurs, the flow of water due to cavitation changes, and the change in the flow of water causes a change in the pressure applied to the stern of the ship. That is, when cavitation occurs, a pressure greater than the pressure applied to the stern of the ship when cavitation does not occur is applied to the stern of the ship. For example, in Fig. 4a, it can be seen that a pressure greater than the set value is applied to the stern of the ship located in the water on the side where the propeller blade (2) is located when the propeller rotation angle is 20 to 40 degrees. This means that cavitation has occurred in the propeller blade (2) that is descending in the range of the propeller rotation angle of 20 to 40 degrees.

[0073] Below, a second embodiment of the first cavitation information generation is described.

[0074] Figure 4a is an example diagram showing time synchronization of first variable pressure information provided by a first pressure detection sensor (111) and propeller rotation angle information provided by a rotation angle measuring device (120).

[0075] The above 1-3 step (S130) uses time-synchronized information (see FIG. 4a) of the first variable pressure information provided by the first pressure detection sensor (111) and the propeller rotation angle information provided by the rotation angle measuring device (120), to determine the propeller rotation angle when the pressure applied to the rear of the ship located underwater on the side where the descending propeller blade (2) is located is at a peak, and generates the determined rotation angle information as first cavitation information.

[0076] For example, in Fig. 4a, the propeller rotation angle is determined to be the peak pressure applied to the rear of the ship located underwater on the side where the propeller blade (2) descending at 32 degrees is located, and the determined propeller rotation angle information of 32 degrees is generated as first cavitation information.

[0077] When cavitation occurs, the flow of water changes due to cavitation, and the change in water flow causes a change in the pressure applied to the stern of the ship. In other words, when cavitation occurs, a greater pressure is applied to the stern of the ship than the pressure applied to the stern of the ship when cavitation does not occur, and the greatest pressure is applied to the stern of the ship at the time of maximum cavitation occurrence.

[0078] For example, in Fig. 4a, it can be seen that the greatest pressure is applied to the rear of the ship located underwater on the side where the propeller blade (2) is located at a propeller rotation angle of 32 degrees, which means that the highest intensity of cavitation occurs on the surface of the propeller blade (2) that is descending at a propeller rotation angle of 32 degrees.

[0079] Below, the generation of the second cavitation information is described.

[0080] Step 1-3 (S130) performed through the data processing unit (130) is characterized by time-synchronizing the second variable pressure information provided by the second pressure detection sensor (112) of the pressure detection unit (110) and the propeller rotation angle information provided by the rotation angle measuring device (120), and generating second cavitation information using the time-synchronized second variable pressure information and the propeller rotation angle information.

[0081] At this time, the second cavitation information is characterized in that it is propeller rotation angle area information when the pressure applied to the rear of the ship located underwater on the side where the rising propeller blade (2) is located is equal to or greater than a set value, or propeller rotation angle information when it is at a peak value. In other words, the second cavitation information also has two embodiments.

[0082] Below, a first embodiment of second cavitation information generation is described.

[0083] Figure 4b is an example diagram showing time synchronization of second pressure fluctuation information provided by a second pressure detection sensor (112) and propeller rotation angle information provided by a rotation angle measuring device (120).

[0084] The above 1-3 steps (S130) use time-synchronized information (see FIG. 4b) of the second variable pressure information provided by the second pressure detection sensor (112) and the propeller rotation angle information provided by the rotation angle measuring device (120) to identify the propeller rotation angle area when the pressure applied to the rear of the ship located underwater on the side where the rising propeller blade (2) is located is greater than a set value, and generate the identified propeller rotation angle area information as second cavitation information.

[0085] For example, in Fig. 4b, the propeller rotation angle region is identified as the region where the pressure applied to the rear of the ship located underwater on the side where the propeller blade (2) rising 280 to 300 degrees is located is greater than the set value, and the identified propeller rotation angle region information of 280 to 300 degrees is generated as second cavitation information.

[0086] Therefore, when cavitation occurs, the flow of water due to cavitation changes, and the change in the flow of water causes a change in the pressure applied to the stern of the ship. That is, when cavitation occurs, a pressure greater than the pressure applied to the stern of the ship is applied to the stern of the ship when cavitation does not occur. For example, in Fig. 4b, it can be seen that the pressure exceeding the set value is applied to the stern of the ship located in the water on the side where the propeller blade (2) is located when the propeller rotation angle is 280 to 300 degrees, which means that cavitation has occurred in the propeller blade (2) that rises in the region of the propeller rotation angle of 280 to 300 degrees.

[0087] Below, a second embodiment of second cavitation information generation is described.

[0088] Figure 4b is an example diagram showing time synchronization of second pressure fluctuation information provided by a second pressure detection sensor (112) and propeller rotation angle information provided by a rotation angle measuring device (120).

[0089] The above 1-3 steps (S130) use time-synchronized information (see FIG. 4b) of the second variable pressure information provided by the second pressure detection sensor (112) and the propeller rotation angle information provided by the rotation angle measuring device (120) to determine the propeller rotation angle when the pressure applied to the rear of the ship located underwater on the side where the rising propeller blade (2) is located is at a peak, and generate the determined rotation angle information as second cavitation information.

[0090] For example, in Fig. 4b, the propeller rotation angle is determined to be the peak pressure applied to the rear of the ship located underwater on the side where the propeller blade (2) rising at 288 degrees is located, and the determined propeller rotation angle information of 288 degrees is generated as second cavitation information.

[0091] When cavitation occurs, the flow of water changes due to cavitation, and the change in water flow causes a change in the pressure applied to the stern of the ship. In other words, when cavitation occurs, a greater pressure is applied to the stern of the ship than the pressure applied to the stern of the ship when cavitation does not occur, and the greatest pressure is applied to the stern of the ship at the time of maximum cavitation occurrence.

[0092] For example, in Fig. 4b, it can be seen that the greatest pressure is applied to the rear of the ship located underwater on the side where the propeller blade (2) is located at a propeller rotation angle of 288 degrees, which means that the highest intensity of cavitation occurs on the surface of the propeller blade (2) that rises at a propeller rotation angle of 288 degrees.

[0093] In addition, step 1-3 (S130) performed through the data processing unit (130) generates cavitation information including the first cavitation information and the second cavitation information when the first cavitation information and the second cavitation information are generated, and provides the generated cavitation information to the rotation speed control unit (200).

[0094] The above second step (S200) is a step of measuring the rotation angle of the propeller (1) in real time after generating cavitation information, and is performed using a rotation angle measuring device (120).

[0095] That is, when generating cavitation information, the rotation angle measuring device (120) provides propeller rotation angle information (see FIG. 3c) measured in real time to the data processing unit (130), and after generating cavitation information, when controlling propeller rotation, it provides propeller rotation angle information (see FIG. 3c) measured in real time to the rotation speed control unit (200).

[0096] The third step (S300) is a step for changing the rotation speed of a ship propeller to reduce cavitation occurrence by using the cavitation information generated through the first step (S100) and the propeller rotation angle information measured in real time through the second step (S200), and is implemented in the rotation speed control unit (200).

[0097] That is, the third step (S300) is characterized in that it calculates propeller (1) speed control information using the cavitation information generated through the first step (S100), and controls the rotation speed of the propeller (1) to change (accelerate or decelerate) at a specific propeller rotation angle using the calculated speed control information and the propeller rotation angle information measured in real time through the second step (S200), thereby controlling cavitation to be reduced.

[0098] Specifically, the third step (S200) is, as illustrated in FIG. 2,

[0099] Step 3-1 (S310) for generating speed control information including speed change area information and speed change value (△n) information for changing the propeller rotation speed using the cavitation information generated through Step 1 (S100),

[0100] It is characterized by including a step 3-2 (S320) for changing the rotation speed of a ship propeller by using the rotation angle information of the propeller measured in real time through the second step (S200) and the speed control information calculated through the third-1 step (S310).

[0101] The above 3-1 step (S310) is a step for calculating speed control information including speed change area information and speed change value (△n) information for changing the propeller rotation speed using the cavitation information generated through the 1st step (S100), and has two embodiments.

[0102] Below, a first embodiment of speed control information generation is described.

[0103] The speed change area included in the speed control information generated through the above-mentioned step 3-1 (S310) is an area of ​​(propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) included in the cavitation information is located is greater than or equal to the set value) and an area of ​​(propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) is located is greater than or equal to the set value), and the speed change value (△n) included in the speed control information generated through the above-mentioned step 3-1 (S310) is characterized in that it is a value within 5% of the propeller reference speed.

[0104] For example, if the propeller rotation angle area information when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) is located is greater than the set value, which is included in the cavitation information, is 20 to 40 degrees, and the propeller rotation angle area information when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) is located is greater than the set value, which is included in the cavitation information, is 280 to 300 degrees, then, as shown in FIG. 5a, 20 to 40 degrees and 280 to 300 degrees are calculated as speed change areas to be included in the speed control information, and, for example, if the reference speed (reference rotation speed) of the propeller (1) is 60 rpm, any one speed value (e.g., 2 rpm) between 0.1 and 3 rpm, which is a value within 5% of the propeller reference speed, is calculated as the speed change value (△n) to be included in the speed control information.

[0105] Below, a second embodiment of speed control information generation is described.

[0106] The speed change area included in the speed control information generated through the above-mentioned step 3-1 (S310) is an area of ​​(propeller rotation angle ±10 degrees when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) included in the cavitation information is located is at its peak) and an area of ​​(propeller rotation angle ±10 degrees when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) included in the cavitation information generated through the first step (S100) is at its peak), and the speed change value (△n) included in the speed control information generated through the above-mentioned step 3-1 (S310) is characterized in that it is a value within 5% of the propeller reference speed.

[0107] In particular, in calculating the speed change area, the reason why the speed change area is set as the area (propeller rotation angle ± 10 degrees when the pressure applied to the rear of the ship located in the water on the side where the descending (rising) propeller blade (2) is located is at its peak) is because the highest intensity cavitation occurs on the surface of the propeller blade (2) at the propeller rotation angle when the pressure applied to the rear of the ship is at its peak, and even in the rotation angle area around the propeller rotation angle when the pressure applied to the rear of the ship is at its peak, cavitation of a certain size occurs, although not at its highest.

[0108] For example, if the propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) is located, which is included in the cavitation information, is at its peak is 32 degrees, and if the propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) is located, which is at its peak is 288 degrees, then, as shown in FIG. 5b, the ±10 degree ranges of the peak angles of 32 degrees and 288 degrees, which are 22 to 42 degrees and 278 to 298 degrees, are calculated as speed change ranges to be included in the speed control information, and, for example, if the reference speed (reference rotation speed) of the propeller (1) is 60 rpm, any one speed value (e.g., 2 rpm) between 0.1 and 3 rpm, which is a value within 5% of the propeller reference speed, is calculated as the speed change value (△n) to be included in the speed control information.

[0109] The above 3-2 step (S320) is a step for changing the rotation speed of a ship propeller by using the rotation angle information of the propeller measured in real time through the 2nd step (S200) and the speed control information calculated through the 3-1 step (S310), and has two embodiments.

[0110] Cavitation occurrence is influenced by the propeller blade structure and the flow characteristics of the water in contact with the propeller blade.

[0111] Specifically, there is a propeller blade having a specific structure, and when the propeller rotates underwater, cavitation may or may not occur on the propeller blade depending on the angle (angle of attack) of the water hitting the propeller blade having a specific structure. In other words, there is a specific angle (angle of attack) of the water hitting the propeller blade that causes cavitation on the propeller blade having a specific structure.

[0112] Therefore, when cavitation occurs, cavitation can be prevented or reduced by changing the propeller blade structure or changing the angle of attack (angle of attack), which is the velocity flow characteristic of the water in contact with the propeller blade.

[0113] However, since it is impossible to change the propeller blade structure of a ship in operation, the rotational speed of the ship's propeller is changed at the propeller rotation angle at which cavitation occurs, in order to suppress the occurrence of cavitation by changing the angle of attack (angle of attack) of the water hitting the blade, which is the velocity flow characteristic of the water in contact with the propeller blade.

[0114] For example, when a propeller blade having a specific structure A rotates at a specific speed underwater, if there is an angle of attack (the angle of water hitting the propeller blade) a that causes cavitation in the propeller blade having a specific structure A, if the rotational speed of the propeller is changed (accelerated or decelerated), the angle of water hitting the propeller blade having a specific structure A (the angle of attack) changes from a to b, so that cavitation does not occur or is reduced in the propeller blade having a specific structure A.

[0115] First, the first embodiment of speed control is described.

[0116] Specifically, the step 3-2 (S320) according to the first embodiment of speed control is characterized in that it changes the rotation speed of a ship propeller by increasing or decreasing the speed of the propeller by a speed change value (△n) from the reference speed in all speed change areas included in the speed control information using an inverter and a motor, and by rotating the propeller at the reference speed in areas other than the speed change area.

[0117] For example, if the speed change area information included in the speed control information is (20 to 40 degrees, 280 to 300 degrees as shown in FIG. 5a or 22 to 42 degrees, 278 to 298 degrees as shown in FIG. 5b) and the speed change value (△n) information is 2 rpm, the 3-2 step (S320) according to the first embodiment of the speed control determines the current rotation angle of the ship propeller using the rotation angle information of the propeller measured in real time through the 2nd step (S200).

[0118] If the current rotation angle of the identified propeller is not an angle belonging to the speed change range (20 to 40 degrees, 280 to 300 degrees as shown in Fig. 5a or 22 to 42 degrees, 278 to 298 degrees as shown in Fig. 5b), the ship propeller is rotated at a reference speed (e.g., 60 rpm), and if the current rotation angle of the identified propeller is an angle belonging to the speed change range (20 to 40 degrees, 280 to 300 degrees as shown in Fig. 5a or 22 to 42 degrees, 278 to 298 degrees as shown in Fig. 5b), the ship propeller is accelerated or decelerated by a speed change value (△n) of 2 rpm from the reference speed (e.g., 60 rpm). That is, the ship propeller is accelerated to 62 rpm in all speed change ranges or decelerated to 58 rpm in all speed change ranges.

[0119] Next, a second embodiment of speed control is described.

[0120] The above 3-2 step (S320) uses an inverter and a motor to change the rotation speed of a ship propeller by increasing the speed of the propeller by a speed change value (△n) from the reference speed in a speed change area corresponding to the front rotation area (0 to 180 degrees) of the propeller among the speed change areas included in the speed control information, and by decreasing the speed of the propeller by a speed change value (△n) from the reference speed in a speed change area corresponding to the rear rotation area (180 to 360 degrees) of the propeller.

[0121] The invention is characterized in that, among the speed change areas included in the speed control information, the propeller is rotated at a reduced speed by a speed change value (△n) from the reference speed in the speed change area corresponding to the first rotation area (0 to 180 degrees) of the propeller using an inverter and a motor, and the propeller is rotated at a higher speed by a speed change value (△n) from the reference speed in the speed change area corresponding to the second rotation area (180 to 360 degrees) of the propeller, thereby changing the rotation speed of the ship propeller.

[0122] For example, if the speed change area information included in the speed control information is (20 to 40 degrees, 280 to 300 degrees as shown in FIG. 5a or 22 to 42 degrees, 278 to 298 degrees as shown in FIG. 5b) and the speed change value (△n) information is 2 rpm, the 3-2 step (S320) according to the second embodiment of speed control determines the current rotation angle of the ship propeller using the rotation angle information of the propeller measured in real time through the 2nd step (S200).

[0123] If the current rotation angle of the identified propeller is not an angle that falls within the speed change range (20 to 40 degrees, 280 to 300 degrees as shown in Fig. 5a or 22 to 42 degrees, 278 to 298 degrees as shown in Fig. 5b), the ship propeller is rotated at a reference speed (e.g., 60 rpm).

[0124] However, if the current rotation angle of the propeller that has been identified is an angle that belongs to a speed change area (20 to 40 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b) corresponding to the first rotation area (0 to 180 degrees) of the propeller among the speed change areas (20 to 40 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b), the propeller is rotated at 62 rpm, which is increased by 2 rpm of the speed change value (△n) from the reference speed (e.g., 60 rpm), and the current rotation angle of the propeller that has been identified is a speed change area that belongs to a second rotation area (180 to 360 degrees) of the propeller among the speed change areas (20 to 40 degrees as shown in FIG. 5a, 280 to 300 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b). If the angle is within the range of 280 to 300 degrees as shown in Fig. 5a or 278 to 298 degrees as shown in Fig. 5b, the ship propeller is rotated at 58 rpm, which is a speed change value (△n) of 2 rpm less than the reference speed (e.g., 60 rpm).

[0125] Also, in the opposite case, if the current rotation angle of the identified propeller is an angle belonging to a speed change area (20 to 40 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b) corresponding to the first rotation area (0 to 180 degrees) of the propeller among the speed change areas (20 to 40 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b), the propeller is rotated at 58 rpm, which is reduced by 2 rpm of the speed change value (△n) from the reference speed (e.g., 60 rpm), and the current rotation angle of the identified propeller is a second rotation area of ​​the propeller among the speed change areas (20 to 40 degrees as shown in FIG. 5a, 280 to 300 degrees as shown in FIG. 5a, or 22 to 42 degrees as shown in FIG. 5b). If the angle is within the speed change area (280 to 300 degrees as shown in Fig. 5a or 278 to 298 degrees as shown in Fig. 5b) corresponding to the area (180 to 360 degrees), the ship propeller is rotated at 62 rpm, which is increased by 2 rpm of the speed change value (△n) from the reference speed (e.g. 60 rpm).

[0126] Although the technical idea of ​​the present invention has been described above with the attached drawings, this is merely an example of a preferred embodiment of the present invention and does not limit the present invention. It is obvious that the scope of the rights of the present invention is not limited to the embodiments, but includes modifications made within the scope of the technical idea of ​​the present invention by a person of ordinary skill in the art.

[0127] [Explanation of symbols]

[0128] 1: Marine propeller

[0129] 2: Propeller blades

[0130] 100: Cavitation information generation unit

[0131] 200: Rotation speed control unit

Claims

1. A method for controlling the rotation speed of a ship propeller to reduce cavitation, A first step (S100) of generating cavitation information regarding cavitation occurring when the propeller (1) rotates; After generating cavitation information, the second step (S200) is to measure the rotation angle of the propeller (1) in real time; A third step (S300) for changing the rotation speed of a ship propeller to reduce cavitation occurrence by using the cavitation information generated through the first step (S100) and the propeller rotation angle information measured in real time through the second step (S200), but including: A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the cavitation information includes information on the rotation angle of the propeller when cavitation occurs.

2. In claim 1, The above first step (S100) is Step 1-1 (S110) of measuring the change in pressure applied to the rear of a ship located underwater due to cavitation occurring on the surface of the propeller blade (2) when the propeller (1) rotates; To generate cavitation information, the first and second steps (S120) measure the rotation angle of the rotating propeller, A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized by including a step 1-3 (S130) of generating cavitation information using information on the measured pressure fluctuation applied to the stern of a ship and information on the measured rotation angle of a propeller.

3. In claim 2, The above step 1-1 (S110) is A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized by measuring a first variable pressure applied to the stern of a ship located underwater on the side where a descending propeller blade (2) is located due to cavitation occurring on the surface of a descending propeller blade (2) when the propeller (1) rotates, and a second variable pressure applied to the stern of a ship located underwater on the side where a rising propeller blade (2) is located due to cavitation occurring on the surface of a rising propeller blade (2).

4. In claim 2, The above steps 1-3 (S130) are: When the propeller (1) rotates, the first variable pressure information and the rotation angle information of the propeller applied to the stern of the ship located in the water on the side where the descending propeller blade (2) is located are time-synchronized due to cavitation occurring on the surface of the descending propeller blade (2), and the first cavitation information regarding cavitation occurring on the side where the descending propeller blade (2) is located is generated using the time-synchronized first variable pressure information and the rotation angle information of the propeller. When the propeller (1) rotates, the second variable pressure information applied to the rear of the ship located underwater on the side where the rising propeller blade (2) is located due to cavitation occurring on the surface of the rising propeller blade (2) and the rotation angle information of the propeller are time-synchronized, and by using the time-synchronized second variable pressure information and the rotation angle information of the propeller, the second cavitation information regarding the cavitation occurring on the side where the rising propeller blade (2) is located is generated. A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized by generating cavitation information including first cavitation information and second cavitation information.

5. In claim 4, The above first cavitation information is, This is information on the propeller rotation angle area when the pressure applied to the rear of the ship located underwater on the side where the descending propeller blade (2) is located is greater than the set value or information on the propeller rotation angle when it is at the peak value. The above second cavitation information is, A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the pressure applied to the rear of a ship located underwater on the side where the rising propeller blade (2) is located is information on a propeller rotation angle area when the pressure is greater than a set value or information on the propeller rotation angle when it is at a peak value.

6. In claim 1, The third step (S300) above is: Step 3-1 (S310) for generating speed control information including speed change area information and speed change value (△n) information for changing the propeller rotation speed using the cavitation information generated through Step 1 (S100), A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized by including a third-second step (S320) for changing the rotation speed of the ship propeller by using the rotation angle information of the propeller measured in real time through the second step (S200) and the speed control information calculated through the third-first step (S310).

7. In claim 6, Speed ​​change included in the speed control information produced through the above step 3-1 (S310) The area is a (propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) included in the cavitation information is located is greater than the set value) area and a (propeller rotation angle when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) included in the cavitation information is located is greater than the set value) area. A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the speed change value (△n) included in the speed control information calculated through the above step 3-1 (S310) is a value within 5% of the propeller reference speed.

8. In claim 6, The speed change area included in the speed control information calculated through the above-mentioned step 3-1 (S310) is an area of ​​(propeller rotation angle ± 10 degrees when the pressure applied to the stern of the ship located underwater on the side where the descending propeller blade (2) included in the cavitation information is located is at the peak) and an area of ​​(propeller rotation angle ± 10 degrees when the pressure applied to the stern of the ship located underwater on the side where the ascending propeller blade (2) included in the cavitation information is located is at the peak). A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the speed change value (△n) included in the speed control information calculated through the above step 3-1 (S310) is a value within 5% of the propeller reference speed.

9. In claim 6, The above step 3-2 (S320) is A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the rotation speed of the ship propeller is changed by increasing or decreasing the speed of the propeller by a speed change value (△n) from a reference speed in all speed change areas included in the speed control information using an inverter and a motor, and by rotating the propeller at a reference speed in areas other than the speed change area.

10. In claim 6, The above step 3-2 (S320) is Using an inverter and a motor, among the speed change areas included in the speed control information, in the speed change area corresponding to the overall rotation area of ​​the propeller (0 to 180 degrees), the propeller is rotated at an increased speed by a speed change value (△n) from the reference speed, and in the speed change area corresponding to the latter rotation area of ​​the propeller (180 to 360 degrees), the propeller is rotated at a reduced speed by a speed change value (△n) from the reference speed, thereby changing the rotation speed of a ship propeller. A method for controlling the rotation speed of a ship propeller for reducing cavitation, characterized in that the rotation speed of the ship propeller is changed by reducing the rotation speed of the propeller by a speed change value (△n) from a reference speed in a speed change range corresponding to the front rotation range (0 to 180 degrees) of the propeller among the speed change ranges included in the speed control information using an inverter and a motor, and increasing the rotation speed of the propeller by a speed change value (△n) from a reference speed in a speed change range corresponding to the rear rotation range (180 to 360 degrees) of the propeller.

Images