CN215285160U

CN215285160U - Air lubrication system for ship

Info

Publication number: CN215285160U
Application number: CN202121672468.7U
Authority: CN
Inventors: 南棅晫; 吴东珍; 朴根; 田承玟
Original assignee: Daewoo Shipbuilding and Marine Engineering Co Ltd
Current assignee: Hanhua Ocean Co ltd
Priority date: 2020-07-24
Filing date: 2021-07-22
Publication date: 2021-12-24
Anticipated expiration: 2031-07-22
Also published as: CN113968306A

Abstract

Disclosed herein is an air lubrication system for a ship that can achieve high energy efficiency when compared to a typical air lubrication system driven by a power generation engine. The air lubrication system includes: a speed governor connected to a main propeller shaft, the main propeller shaft being connected to a main engine of the ship, the speed governor changing a rpm of the main propeller shaft and outputting the changed rpm; at least one air compressor connected to the speed regulator and rotating at a rpm output from the speed regulator to supply compressed air via compression of the air; an air ejector disposed on a bow of the ship and discharging compressed air supplied from the at least one air compressor to an outside of the ship; and an air delivery pipe through which compressed air supplied from the at least one air compressor is delivered to the air ejector.

Description

Air lubrication system for ship

Technical Field

The present invention relates to an air lubrication system for a ship, and more particularly, to an air lubrication system for a ship that can achieve high energy efficiency when compared with a typical air lubrication system driven by a power generation engine.

Background

During navigation of a ship, the hull of the ship is subjected to wave resistance, viscous resistance and air resistance. To reduce these resistances, most ships are streamlined.

The wave resistance is caused by a regular wave generated by the bow of the ship passing through water during the propulsion of the ship, and it acts perpendicular to the entire region of the hull, causing energy loss of the ship. Viscous drag is due to the viscosity of water and is generally classified into frictional drag and form drag. Frictional resistance refers to the drag that impedes the travel of the ship due to the viscous adhesion of seawater to the wetted surfaces of the hull.

In order to reduce frictional resistance, various solutions have been proposed, such as the design of hydrofoils adapted to minimize the contact area between seawater and the hull, the design of air-lubricated ships adapted to improve the conditions of the wetted surfaces and bottoms of the hull, and the design of supercavitation underwater vehicles.

As another solution to reduce frictional resistance, an air lubrication system has been proposed which can reduce energy loss due to viscosity of seawater by forming an air layer on a hull surface to prevent the hull surface from contacting the seawater.

A general air lubrication system reduces frictional resistance by generating air cavities on the surface of a hull to reduce a wet surface area of a ship, and is thus very environmentally friendly and easily applied to a real ship.

FIG. 1 is a diagram of a typical air lubrication system.

Referring to fig. 1, the air lubrication system includes: an air ejector 11 disposed at the bow of the hull 20; two

air compressors

13, 14 disposed adjacent to the air ejector 11; and two

motors

15, 16 disposed adjacent to the air ejector 11 to drive the

air compressor

13, 14. In addition, the air lubrication system may include a power board 17 to drive the

motors

15, 16. Further, the air lubrication system includes an air delivery pipe AP connected between the air injector 11 and the

air compressor

13 and 14.

The power generation engine GE is disposed at the stern of the hull. The distribution board 17 receives electric power from the generator motor GE and distributes the received electric power to the motor 15 and the motor 16. In addition, the main engine ME may be disposed at the stern of the hull.

The power generation engine GE may include a plurality of power generation engines. Here, a switchboard SB may be provided to manage the power generated by the power generation motor GE. That is, the distribution board SB may be electrically connected to the distribution board 17.

Although not shown, the air lubrication system may further include a device for adjusting the amount of air discharged from the air ejector 11 as needed.

< related document >

< patent document >

(patent document 1) Korean patent laid-open publication No. 10-2020-0063398 (2020.06.05.)

SUMMERY OF THE UTILITY MODEL

An object of the present invention is to provide an air lubrication system for a ship that can achieve high energy efficiency when compared with a typical air lubrication system driven by a power generation engine.

According to an aspect of the present invention, an air lubrication system includes: a speed governor connected to a main propulsion shaft connected to a main engine of the ship, the speed governor changing a rpm of the main propulsion shaft and outputting the changed rpm; at least one air compressor connected to the speed regulator and rotating at a rpm output from the speed regulator to supply compressed air via compression of the air; an air ejector disposed on a bow of the ship and discharging compressed air supplied from the at least one air compressor to an outside of the ship; and an air delivery pipe through which compressed air supplied from the at least one air compressor is delivered to the air ejector.

The speed governor may comprise at least one gear train adapted to vary the rpm of the main propulsion shaft.

The governor may further include a clutch adapted to resist the output of the varying rpm.

The air lubrication system may further comprise: at least one control valve disposed on the at least one air compressor and regulating an air supply pressure of the at least one air compressor.

The air lubrication system may further comprise: a temperature regulator disposed on the air delivery pipe and regulating a temperature of the compressed air supplied from the at least one air compressor.

According to another aspect of the present invention, an air lubrication system comprises: a speed governor connected to a main propulsion shaft connected to a main engine of the ship, the speed governor changing a rpm of the main propulsion shaft and outputting the changed rpm; at least one rotary compressor connected to the speed governor and rotating at a rpm output from the speed governor to supply compressed air via compression of the air; at least one electrically driven compressor driven by electric power supplied from a power generation engine of the vessel to supply compressed air; an air ejector disposed on a bow of the ship and discharging compressed air supplied from the at least one rotary compressor and the at least one electrically driven compressor to the outside of the ship; and an air delivery pipe through which compressed air supplied from the at least one rotary compressor and the at least one electrically driven compressor is delivered to the air ejector.

The air delivery duct may allow compressed air supplied from the at least one rotary compressor to merge with compressed air supplied from the at least one electrically driven compressor before the compressed air is delivered to the air ejector.

The at least one electrically driven compressor may include a third air compressor and a fourth air compressor disposed at a stern of the hull, wherein the air lubrication system may further include: and a starter controlling current or voltage supplied to the third and fourth air compressors.

According to the present invention, the air lubrication system is connected to the main propeller shaft via the speed governor to operate without electric power generated by the generator engine as in the prior art, thereby achieving reduction in fuel consumption.

Additionally, the air lubrication system may operate the air compressor without using a separate electrical panel.

Furthermore, the air lubrication system can better utilize the internal space of a ship and reduce shipbuilding costs by using an engine having relatively low output power when compared with a typical air lubrication system, and can significantly reduce shipbuilding costs by reducing the costs of auxiliary equipment such as a fresh water coolant pump, a seawater coolant pump, a cooler and fuel oil pump, and an engine room blower.

Furthermore, the air lubrication system can reduce the weight of the ship and sufficient cargo space by using an engine having relatively low output power when compared with a typical air lubrication system.

Furthermore, the air lubrication system may achieve fuel savings at lower vessel speeds as well as at higher vessel speeds.

Drawings

The above and other aspects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings:

FIG. 1 is a diagram of a typical air lubrication system.

Fig. 2 is a diagram of an air lubrication system for a marine vessel according to an embodiment of the present invention.

Fig. 3 is a diagram of an air lubrication system for a marine vessel, showing a connection between an air compressor and an air injector via an air duct, according to an embodiment of the present invention.

Fig. 4 is an enlarged view of a portion of an air lubrication system for a marine vessel according to an embodiment of the present invention.

Fig. 5 is a diagram of an air lubrication system for a ship according to another example of the present invention.

Fig. 6 is a diagram of an air lubrication system for a marine vessel according to another embodiment of the present invention, showing the connection between the air compressor and the air ejector via the air delivery pipe.

Fig. 7 is an enlarged view of a portion of an air lubrication system for a ship according to another example of the present invention.

Description of the reference numerals

11. 110: an air ejector;

13. 14: an air compressor;

15. 16: an electric motor;

17: a distribution board;

20. 200: a hull;

100. 100 a: an air lubrication system;

120: a speed regulator;

122: a clutch;

124: a gear train;

130: a first air compressor;

140: a second air compressor;

150: a temperature regulator;

160: a control valve;

170: an emergency stop valve;

180: a third air compressor;

182: a first drive motor;

190: a fourth air compressor;

192: a second drive motor;

AP: an air delivery pipe;

GE: a power generation engine;

MA: a main propulsion shaft;

ME: a main engine;

STT: a starter;

SB: a panel board.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Descriptions of well-known functions and constructions that may unnecessarily obscure the subject matter of the present invention will be omitted.

In addition, when an element is referred to as being "on," "connected to," "supported by," or "coupled to" another element, it can be directly formed on, connected to, supported by, or coupled to the other element, or intervening elements may also be "interposed" therebetween. Further, when a fluid is referred to as being "supplied to" or "delivered to" a component, the fluid may be supplied directly to or delivered to the component, or may be supplied to or delivered to the component via an intervening component.

Although specific terms are employed herein, they are used and are to be interpreted in a descriptive sense only and not for purposes of limitation. As used herein, the singular forms "a" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In addition, spatially relative terms such as "under …," "below," "above," "upper," "right," "left," and the like are based on the depictions in the figures and may be expressed differently when changing the orientation of the corresponding objects. For the same reason, some components are enlarged, omitted, or schematically shown in the drawings, and the depicted size of each component may not necessarily reflect its actual size.

It will be understood that, although the terms "first," "second," etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one element from another.

Furthermore, as used herein, the terms "comprises/comprising" and/or "comprising/includes" specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, and/or components.

Fig. 2 is a diagram of an air lubrication system for a marine vessel according to an embodiment of the present invention;

fig. 3 is a diagram of an air lubrication system for a marine vessel, showing the connection between the air compressor and the air injector via an air duct, according to an embodiment of the present invention; and fig. 4 is an enlarged view of a portion of an air lubrication system for a ship according to an embodiment of the present invention.

The air lubrication system 100 for a ship according to this embodiment discharges air generated by the

air compressors

130, 140 to the outside of the hull 200 via the air injectors 110.

Although the air lubrication system 100 according to this embodiment shown in fig. 2 to 4 includes two

air compressors

130, 140, it is to be understood that the present invention is not limited thereto and the number of air compressors may be changed as needed.

For convenience of description, the two air compressors will be referred to as a first air compressor 130 and a second air compressor 140, respectively.

Referring to fig. 2, the air lubrication system 100 according to this embodiment includes an air ejector 110, a governor 120, a first air compressor 130, a second air compressor 140, and an air delivery pipe AP.

The air ejector 110 discharges air generated by the first and

second air compressors

130 and 140 to the outside of the hull 200. The air ejector 110 may be disposed at the bow of the hull 200. The air ejector 110 may be provided with means for adjusting the amount of air ejected via the air ejector 110.

Here, the air ejector 110 may be provided with an emergency stop valve 170 to stop air from being delivered to the air ejector 110 in an emergency. When the air ejector 110 fails to eject air normally due to, for example, abnormal pressure of air delivered via the air delivery pipe AP, the emergency stop valve 170 may prevent air from being discharged to the outside of the hull 200.

The speed governor 120 is connected to a main propulsion shaft MA, which is connected to a main engine ME, as shown in fig. 4.

The governor 120 changes the rpm of the main propeller shaft MA rotated by the main engine ME to the required rpm of the first and

second air compressors

130 and 140. To this end, the governor 120 may include a clutch 122 and a gear train 124.

The clutch 122 serves to cut off power transmission when the first and

second air compressors

130 and 140 are not operated.

The gear train 124 changes the rpm of the main propulsion shaft MA to the desired rpm of the first and

second air compressors

130 and 140. The gear train 124 may include a plurality of gears to vary the rpm. The gear ratio of the gear train 124 may be varied as desired.

In this embodiment, the invention is described with reference to an example in which the governor 120 includes a pair of gear trains 124 for each of a total of four gear trains 124, a first air compressor 130, and a second air compressor 140. Here, the corresponding pair of gear trains 124 changes the rpm of the main propulsion shaft MA to a desired rpm of the first air compressor 130 or the second air compressor 140 according to a gear ratio of each gear train 124.

In this embodiment, assuming that the main propulsion shaft MA rotates at about 100 revolutions per minute, the governor 120 may allow the first and

second air compressors

130 and 140 to rotate at about 1,000 to 3,000 revolutions per minute.

The gear train 124 may have continuously variable gear ratios, or may have two or three gear ratios as desired. Alternatively, the gear 124 may have a single fixed gear ratio as desired.

Each of the first and

second air compressors

130 and 140 is disposed at an output side of the speed regulator 120 and rotates at a rpm output from the speed regulator 120 to supply compressed air to the air delivery pipe AP via the compressed air.

In this embodiment, each of the first and

second air compressors

130 and 140 may be provided in the form of a centrifugal compressor, a screw compressor, or a positive displacement compressor.

In addition, each of the first and

second air compressors

130 and 140 may be provided at the inlet and outlet sides thereof with cross-sectional area adjusting means (not shown), such as guide vanes, which change the inlet and outlet cross-sectional areas of the air compressors.

Alternatively, each of the first and

second air compressors

130 and 140 may be provided with a device adapted to adjust its internal rpm.

Although the clutch 122 is disposed in the governor 120 in this embodiment, it should be understood that the present invention is not limited thereto. The clutch 122 may be disposed in each of the first and

second air compressors

130 and 140 as needed.

The air lubrication system 100 may further include a temperature regulator 150 to adjust the temperature of the air supplied from the first and

second air compressors

130 and 140. The temperature regulator 150 may reduce the temperature-dependent change by controlling the temperature of the air supplied from the first and

second air compressors

130 and 140.

Each of the first and

second air compressors

130, 140 may be provided with a control valve 160 to control the air supply pressure of the first or

second air compressor

130, 140. For example, the control valve 160 may be connected in parallel to the first air compressor 130, as shown in fig. 3.

The air delivery pipe AP is adapted to deliver air generated by the first and

second air compressors

130 and 140 to the air ejector 110. To this end, the air delivery pipe AP may include a section connected to the air ejector 110 and two sections diverging therefrom and connected to the first and

second air compressors

130 and 140, respectively.

In this embodiment, since the first and

second air compressors

130 and 140 are disposed at the stern of the hull 200 and the air ejector 110 is disposed at the bow of the hull 200, the air delivery pipe AP may extend from the stern of the hull 200 to the bow of the hull 200.

The air lubrication system 100 according to this embodiment may inject air at an air injection rate according to the speed of the ship. For this purpose, the pressure of the air compressed by the first and

second air compressors

130 and 140 may be determined according to a required air injection rate.

Accordingly, the pressure of the air compressed by the first and

second air compressors

130 and 140 may be controlled by adjusting the rpm output from the speed governor 120 connected to the main propulsion shaft MA.

In addition, the air supply pressure of the first and

second air compressors

130 and 140 may be regulated by a cross-sectional area adjusting device that changes inlet and outlet cross-sectional areas of the first and

second air compressors

130 and 140.

That is, the air lubrication system 100 according to this embodiment may further include a controller. The controller may vary the gear stages of the gear train 124 of the governor 120 to control the rpm output from the governor 120.

In addition, the controller may control a cross-sectional area adjusting device provided to each of the first and

second air compressors

130 and 140 to change inlet and outlet cross-sectional areas.

Further, the controller may control the control valve 160. That is, the controller may control the air supply pressure of the first and

second air compressors

130 and 140 via the control valve 160.

The controller may control the emergency stop valve 170. Accordingly, after the abnormal air pressure occurs in the air delivery pipe AP, the controller may stop the injection of the air through the air injector 110 by controlling the emergency stop valve 170.

The controller may be implemented by a computing device that includes a microprocessor, memory, and the like. Since a method of implementing this controller is well known to those skilled in the art, a detailed description thereof will be omitted.

Next, a method of operating an air lubrication system for a ship according to an embodiment of the present invention will be briefly described, wherein the air lubrication system further includes a control unit storing information on an optimal air injection rate according to a speed of the ship. The method comprises the following steps: determining a required air injection rate from the ship speed based on information stored in the control unit; determining an operating pressure of the air compressor based on the desired air injection rate; determining a rpm of the air compressor or an output rpm of a governor mounted on a main propeller shaft; and adjusting the pressure of the air to be injected outside the vessel.

Here, the step of adjusting the pressure of the air to be injected outside the ship may be performed by controlling guide vanes disposed at both inlet and outlet sides of the air compressor and a control valve disposed on a pipe connected between the inlet and outlet of the air compressor.

Thus, the air lubrication system according to the present invention may operate efficiently when compared to typical air lubrication systems driven by power generation engines, thereby providing improved fuel savings.

Fuel consumption comparison

The inventors of the present invention verified the reduction of the fuel consumption of the ship due to the use of the air lubrication system 100 according to this embodiment by calculating the fuel efficiency after applying the air lubrication system 100 according to this embodiment to the LNG carrier having the MEGI engine operating in the gas mode.

The following is a comparison between the fuel consumption of a ship employing a typical air lubrication system driven by a power generation engine (comparative example) and the fuel consumption of a ship employing the air lubrication system 100 according to this embodiment (example).

Here, the fuel efficiency is calculated for a ship speed of 18.5 knots.

In addition, a calculation was made regarding the fuel consumption of a ship employing a typical air lubrication system before the air lubrication system (comparative example 1) was operated and after the air lubrication system (comparative example 2) was operated, and the results are shown in table 1.

TABLE 1

	Comparative example 1	Comparative example 2	Example 1
				Fuel consumption (ton/day)	68.0	64.7	64.5
Rate of reduction of fuel consumption	--	4.853％	5.147％

In comparative example 1, the fuel consumption of the ship before operating the typical air lubrication system was calculated for a ship speed of 18.5 knots. The shaft power of the Main Engine (ME) was calculated as 16,950 kilowatts (ME load: 67%) before operating the typical air lubrication system. The specific fuel gas consumption (SGC) of the main engine calculated for 67% ME load is 129.0 grams/kWh.

Thus, the daily fuel consumption of the main engine is calculated to be 52.5 tons/day. In addition, the power generation engine is calculated to consume 15.5 tons of fuel per day, and thus the total daily fuel consumption of the ship is calculated to be 68.0 tons/day.

In comparative example 2, the fuel consumption of the ship after operating the typical air lubrication system driven by the power generation engine was calculated at the same ship speed as in comparative example 1. The shaft power of the main engine was calculated as 15,187.4 kilowatts (ME load: 60.3%). That is, a power savings of about 10.4% was recorded when compared to before operating the air lubrication system.

The SGC of the main engine calculated for an ME load of 60.3% is 129.2 grams/kilowatt-hour. Thus, the daily fuel consumption of the main engine was calculated to be 47.1 tons/day.

In addition, in comparative example 2, the load per power generation engine was increased as compared with comparative example 1 due to the operation of the air lubrication system. Calculating an additional gas consumption of the power generation engine based on the increase.

In operation there are 2 groups of power generating engines. The SGC for each power generation engine for the load before/after operation of the ALS is obtained. The obtained SGC value is multiplied by the horsepower of each power generation engine, and then subtracted from each other. Therefore, the additional fuel consumption of the power generation engine is calculated to be 2.1 tons/day. Thus, the total fuel consumption of the vessel after operating a typical air lubrication system is calculated to be 64.7 tons/day (47.1 tons/day +15.5 tons/day +2.1 tons/day).

In example 1, the fuel consumption of a ship after applying an air lubrication system according to an embodiment of the present invention was calculated. In operation of an air lubrication system according to an embodiment, 705(698/0.99) kilowatt power is increased to drive an air compressor connected to a governor. For a given vessel speed, the shaft power of the main engine is calculated to be 15,892.3 kilowatts (15,187.3 kilowatts +705 kilowatts).

This value corresponds to a ME load of 63%. The SGC of the main engine calculated for an ME load of 63% is 128.6 grams/kilowatt-hour.

Thus, the daily fuel consumption of the main engine was calculated to be 49.0 tons/day. Since there was no difference in fuel consumption of the power generation engine between example 1 and the comparative example, the daily fuel consumption of the power generation engine was calculated to be 15.5 tons/day. Thus, the total daily fuel consumption of the vessel is calculated to be 64.5 tons/day (49.0 tons/day +15.5 tons/day).

As shown in table 1, it can be seen that the fuel consumption of the ship employing the typical air lubrication system after operating the typical air lubrication system (comparative example 2) was reduced by 4.853% when compared to before operating the air lubrication system (comparative example 1).

In addition, it can be seen that the use of the air lubrication system according to the embodiment (example 1) can achieve a reduction in fuel consumption because the air lubrication system is connected to the main propeller shaft via the speed governor to operate without using the electric power generated by the power generation engine.

Further, it can be seen that the fuel consumption was reduced by 0.3% after the air lubrication system according to the embodiment (example 1) was used, when compared to after the typical air lubrication system (comparative example 2) was used.

That is, as in the prior art, the use of an air lubrication system according to embodiments of the present invention in a marine vessel may eliminate the need to increase the generator capacity for operating the compressor of the air lubrication system and the need for a separate starter. In addition, since the air lubrication system according to the embodiment allows air sucked from an engine room to be supplied to the air compressor unlike a typical air lubrication system in which an air compressor is disposed at the bow of a hull, an existing engine room FAN (ER FAN) may be used to supply air to the air compressor, thereby allowing the number of required equipment to be reduced and thus better utilization of the space inside the ship.

Fig. 5 is a diagram of an air lubrication system for a marine vessel according to another embodiment of the present invention;

fig. 6 is a diagram of an air lubrication system for a marine vessel according to this embodiment, showing the connection between the air compressor and the air ejector via the air delivery pipe; and fig. 7 is an enlarged view of a part of the air lubrication system for a ship according to this embodiment.

In the description of the air lubrication system 100a for a ship according to this embodiment, the same components will be denoted by the same reference numerals.

Referring to fig. 5 to 7, the air lubrication system 100a for a ship according to this embodiment includes an air ejector 110, a speed governor 120, a first air compressor 130, a second air compressor 140, and an air delivery pipe AP, similar to the air lubrication system according to the above-described embodiment.

Each of the first and

second air compressors

130 and 140 may be a rotary compressor disposed at an output side of the speed regulator 120, and rotates at a rpm output from the speed regulator 120 to supply compressed air to the air delivery pipe AP via compression of the air, as described above.

The air lubrication system 100a according to this embodiment may further include at least one of an electrically driven compressor 180, an electrically driven compressor 190 driven by the electric power supplied from the power generation engine GE.

Although the air lubrication system will be described as including two electrically driven compressors, it should be understood that the present invention is not so limited and the number of electrically driven compressors may vary as desired.

For convenience of description, the two electrically driven compressors will be referred to as a third air compressor 180 and a fourth air compressor 190, respectively.

The third air compressor 180 and the fourth air compressor 190 are driven by a first driving motor 182 and a second driving motor 192, respectively. The compressed air generated by the third air compressor 180 and the fourth air compressor 190 may be supplied to the air delivery pipe AP.

In this embodiment, the third and

fourth air compressors

180 and 190 may be connected to an air delivery pipe AP connected to the first air compressor 130 such that compressed air generated by the third and

fourth air compressors

180 and 190 is supplied to the air delivery pipe AP.

The first drive motor 182 and the second drive motor 192 are driven by the electric power generated by the generator motor GE. The first drive motor 182 drives the third air compressor 180 and the second drive motor 192 drives the fourth air compressor 190.

To this end, the air lubrication system according to this embodiment further includes a starter STT that controls a voltage or current supplied to the first and

second driving motors

182 and 192. The starter STT may be electrically connected to a switchboard SB of the generator engine GE.

In this embodiment, the third air compressor 180 and the fourth air compressor 190 may be disposed at the stern of the hull 200, similar to the first air compressor 130. Therefore, in the air lubrication system according to this embodiment, the starter STT may be located at a relatively short distance from the switchboard SB of the generator engine GE disposed at the stern of the hull 200 when compared with a typical air lubrication system.

The air lubrication system for a ship according to this embodiment can achieve a significant reduction in shipbuilding costs via the use of engines having relatively low output power and a reduction in the cost of auxiliary equipment (e.g., fresh water coolant pumps, seawater coolant pumps, coolers and fuel oil pumps, and engine room blowers) when compared to the air lubrication system according to the above-described embodiment.

In addition, the air lubrication system for a ship according to this embodiment may provide a reduction in weight of the ship and may ensure sufficient cargo space by better utilizing the internal space of the ship.

Further, the air lubrication system for a ship according to this embodiment can achieve fuel savings at low ship speeds as well as high ship speeds.

Next, a method of operating the air lubrication system for a ship according to this embodiment will be briefly described, wherein the air lubrication system further includes a control unit storing information on an optimal air injection rate according to a ship speed. The method comprises the following steps: determining a required air injection rate from the ship speed based on information stored in the control unit; determining an operating pressure of the air compressor based on the desired air injection rate; selecting at least one air compressor among the air compressors according to the ship speed and operating the selected air compressor; adjusting the rpm of an air compressor or the output rpm of a speed governor mounted on a main propeller shaft; and adjusting the pressure of the air to be discharged to the bottom of the ship.

For example, the step of adjusting the pressure of the air to be injected to the bottom of the vessel may be performed by controlling guide vanes at both the inlet and outlet sides of the air compressor and a control valve disposed on a pipe connected between the inlet and outlet of the air compressor.

In the step of selecting at least one air compressor and driving the selected air compressor, when the ship travels at a speed exceeding a predetermined value, the third air compressor 180 and the fourth air compressor 190 may be driven by the power generated by the on-board power generation engine GE (that is, the compressors are electrically driven); and the first air compressor 130 and the second air compressor 140 connected to the speed governor 120 may be driven when the ship travels at a speed less than or equal to a predetermined value.

Comparison of energy saving efficiency

Table 2 shows the results of comparing the fuel consumption and energy saving efficiency of a container ship equipped with a 66,200 kw 11 cylinder main engine before operating a typical Air Lubrication System (ALS) (comparative example 3) and after operating an ALS (comparative example 4).

TABLE 2

Referring to table 2, it can be seen that at a certain value (18 knots) or at vessel speeds above that value, the vessel records an energy savings of about 0.3% to 3.6%, while at vessel speeds at 17 knots or below 17 knots, the vessel records a negative energy savings, that is, a typical air lubrication system fails to provide an energy saving benefit.

Table 3 shows the results of comparing the fuel consumption between the case where the air lubrication system according to the embodiment is used for the same ship (example 2) and the case where the typical air lubrication system is used (comparative example 4).

TABLE 3

Referring to table 3, it can be seen that the air lubrication system according to the embodiment can achieve similar or significantly improved energy saving with a reduced engine output when compared with comparative example 4 in which a typical air lubrication system driven by electric power generated by a power generation engine is used.

In particular, typical air lubrication systems result in negative energy savings at ship speeds at or below a certain value, whereas air lubrication systems according to embodiments enable positive energy savings even at low ship speeds, thereby providing a reduction in fuel consumption when compared to typical air lubrication systems.

Although some embodiments have been described herein, it should be understood that the foregoing embodiments are provided for illustrative purposes only and are not to be construed as limiting the invention in any way. Accordingly, the scope of the present invention should be defined by the appended claims and equivalents thereof.

Claims

1. An air lubrication system, comprising:

a speed governor connected to a main propulsion shaft connected to a main engine of a ship, the speed governor changing a rpm of the main propulsion shaft and outputting the changed rpm;

at least one air compressor connected to the speed governor and rotating at the rpm output from the speed governor to supply compressed air via compression of air;

an air ejector disposed on a bow of the ship and discharging the compressed air supplied from the at least one air compressor to an outside of the ship; and

an air delivery pipe through which the compressed air supplied from the at least one air compressor is delivered to the air ejector.

2. The air lubrication system of claim 1, wherein the speed governor includes at least one gear train adapted to vary the rpm of the main propulsion shaft.

3. The air lubrication system of claim 2, wherein the governor further comprises a clutch adapted to prevent the output of the varying rpm.

4. The air lubrication system of claim 1, further comprising:

at least one control valve disposed on the at least one air compressor and regulating an air supply pressure of the at least one air compressor.

5. The air lubrication system of claim 1, further comprising:

a temperature regulator disposed on the air delivery pipe and regulating a temperature of the compressed air supplied from the at least one air compressor.

6. An air lubrication system, comprising:

at least one rotary compressor connected to the governor and rotating at the rpm output from the governor to supply compressed air via compression of air;

at least one electrically driven compressor driven by electric power supplied from a power generation engine of the vessel to supply compressed air;

an air ejector disposed on a bow of the ship and discharging compressed air supplied from the at least one rotary compressor and the at least one electrically driven compressor to an outside of the ship; and

an air delivery pipe through which compressed air supplied from the at least one rotary compressor and the at least one electrically driven compressor is delivered to the air ejector.

7. An air lubrication system according to claim 6, wherein the air delivery pipe allows compressed air supplied from the at least one rotary compressor to merge with compressed air supplied from the at least one electrically driven compressor before the compressed air is delivered to the air ejector.

8. The air lubrication system of claim 6, further comprising: a starter controlling a current or voltage supplied to the at least one electrically driven compressor.