Ship propulsion system and method for operating the same

Abstract

A ship propulsion system (10) comprising at least one internal combustion engine (11) having cylinders (12) in which exhaust gas is generated during the combustion of fuel, wherein the respective internal combustion engine (11) interacts with at least two exhaust gas turbochargers (13a, 13b), namely at least one high-pressure exhaust gas turbocharger (13a) having a high-pressure turbine (14a) and a high-pressure compressor (15a), and one low-pressure exhaust gas turbocharger (13b) having a low-pressure turbine (14b) and a low-pressure compressor (15b), such that the exhaust gas (A) of the cylinders (12) can be expanded in the turbine (14a, 14b) of the respective exhaust gas turbocharger (13a, 13b), and that energy obtained during the expansion of the exhaust gas (A) in the turbine (14a, 14b) of the respective exhaust gas turbocharger (13a, 13b) can be used to drive the compressor (15a, 15b) of the respective exhaust gas turbocharger (13a, 13b) for compressing charge air (L) to be supplied to the cylinders (12).The ship's propulsion system (10) comprises an air lubrication system (16) having a plurality of nozzles (17) through which air bubbles can be expelled beneath a ship's bottom to reduce the ship's resistance. The respective internal combustion engine (11) is coupled to the air lubrication system (16) via branch lines such that charge air (L) compressed in the high-pressure compressor (15a) can be supplied to the air lubrication system (16) via a first branch line (18a) and charge air (L) compressed in the low-pressure compressor (15b) can be supplied via a second branch line (18b), which can be expelled as charge air bubbles beneath the ship's bottom via the nozzles (17) of the air lubrication system (16).The branch lines (18a, 18b) are operatively connected to a respective valve (19a, 19b) in such a way that when the respective valve (19a, 19b) is closed, the respective branch line (18a, 18b) is closed, and when the respective valve (19a, 19b) is open, the respective branch line (18a, 18b) is opened in order to supply a portion of the charge air (L) to the air lubrication system (16), wherein the air lubrication system (16) has at least one compressor (20) for compressing air for the air lubrication system (16), wherein the at least one compressor (20) is operable when the respective valve (19a, 19b) is closed.

Description

[0001] The invention relates to a ship propulsion system. Furthermore, the invention relates to a method for operating a ship propulsion system.

[0002] A marine propulsion system comprises at least one internal combustion engine. Each internal combustion engine has cylinders in which fuel is burned. The combustion of the fuel produces exhaust gas. Each internal combustion engine interacts with at least one exhaust gas turbocharger. For example, an internal combustion engine can interact with a high-pressure exhaust gas turbocharger and a low-pressure exhaust gas turbocharger. An exhaust gas turbocharger comprises a turbine and a compressor. Exhaust gas from the cylinders is expanded in the turbine of the respective exhaust gas turbocharger. The energy gained during the expansion of the exhaust gas in the turbine of the respective exhaust gas turbocharger is used to drive the compressor of the respective exhaust gas turbocharger to compress the charge air supplied to the cylinders.The respective internal combustion engine can, for example, drive a generator to generate electrical energy, which is then used to drive at least one ship's propeller via at least one electric machine. It is also possible to drive a ship's propeller directly via the at least one internal combustion engine.

[0003] A ship's propulsion system also features an air lubrication system. This type of system is also called an air lubrication system. Through this system, air bubbles are expelled beneath the ship's hull, reducing the ship's drag and thus its friction in the water. To generate the air for the air lubrication system, an air lubrication system typically uses electrically driven compressors to provide the required compressed air. Driving the compressors requires a lot of energy.

[0004] DE 10 2020 117 399 A1 discloses a marine propulsion system with at least one internal combustion engine and an air lubrication system. Exhaust gas leaving the cylinders of the internal combustion engine can be extracted via a wastegate upstream of a turbine of an exhaust gas turbocharger and fed to the air lubrication system to expel exhaust gas bubbles as air bubbles beneath the ship's bottom via the air lubrication system.

[0005] US 2023 / 0 331 349 A1 and US 2023 / 0 143 335 A1 also disclose ship propulsion systems with at least one internal combustion engine and an air lubrication system.

[0006] Based on this, the present invention is based on the object of being able to operate an air lubrication system efficiently even at low loads. This object is achieved by a ship propulsion system according to claim 1. According to the invention, the respective internal combustion engine is coupled to the air lubrication system via branch lines in such a way that charge air compressed in the high-pressure compressor can be supplied to the air lubrication system via a first branch line and charge air compressed in the low-pressure compressor via a second branch line, wherein the respective charge air can be expelled as charge air bubbles beneath the ship's bottom via the nozzles of the air lubrication system.

[0007] The present invention proposes, in a ship propulsion system whose respective internal combustion engine has at least one high-pressure exhaust turbocharger and one low-pressure exhaust turbocharger, supplying charge air from the high-pressure compressor of the high-pressure turbocharger and / or from the low-pressure compressor of the low-pressure turbocharger to the air lubrication system in order to expel charge air bubbles as air bubbles beneath the ship's bottom. In the ship propulsion system according to the invention, charge air from the at least one internal combustion engine is supplied to the air lubrication system, rather than exhaust gas. This reduces the energy required to drive the compressors in air lubrication systems known from the prior art. Furthermore, there is no risk of contamination for the nozzles of the air lubrication system.

[0008] The branch lines are operatively connected to a respective valve in such a way that when the respective valve is closed, the respective branch line is closed, and when the respective valve is open, the respective branch line is opened to supply a portion of the charge air to the air lubrication system. This allows the charge air to be supplied to the air lubrication system in a particularly advantageous and simple manner from the high-pressure compressor of the high-pressure exhaust turbocharger and from the low-pressure compressor of the low-pressure exhaust turbocharger.

[0009] The ship's propulsion system preferably has a control device which opens or closes the respective valve depending on the load state of the respective internal combustion engine and / or depending on the amount of air required by the air lubrication system and / or depending on the air pressure required by the air lubrication system. This allows the internal combustion engine and the air lubrication system of the ship's propulsion system according to the invention to be operated advantageously with a high degree of efficiency. Depending on the load state of the respective internal combustion engine and / or depending on the amount of air required by the air lubrication system and / or depending on the air pressure required by the air lubrication system, the control device opens or closes the respective valve in order to open or close the respective branch line. If there is no excess charge air in the area of ​​the internal combustion engine or the amount of excess charge air orIf their pressure is too low to operate the air lubrication system, additional compressed air can be provided for the air lubrication system via the at least one compressor. The air lubrication system has at least one compressor to compress air for the air lubrication system. The at least one compressor can be operated when the respective valve is closed, and preferably when the amount of charge air flowing through the respective branch line is too low when the valve is open.

[0010] The invention allows a particularly efficient operation of a ship propulsion system, namely the respective internal combustion engine and the air lubrication system of the ship propulsion system.

[0011] The method for operating a ship propulsion system is defined in claim 7.

[0012] Preferably, when the load of the respective internal combustion engine is less than a limit value, preferably greater than a first limit value and less than a second limit value, charge air is taken downstream of the high-pressure compressor and supplied to the air lubrication system. Then, when the load of the respective internal combustion engine is greater than the limit value, preferably greater than the second limit value, charge air is preferably taken downstream of the low-pressure compressor and supplied to the air lubrication system. In particular, when the load of the respective internal combustion engine is less than the first limit value, no charge air is taken and supplied to the air lubrication system. This allows for particularly advantageous operation of the ship's propulsion system. When the load of the respective internal combustion engine is relatively low, charge air can preferably be taken downstream of the high-pressure compressor.At a relatively high load on the respective internal combustion engine, especially at or near full load, charge air can preferably be extracted downstream of the low-pressure compressor and fed to the air lubrication system. This avoids excessive work on the high-pressure compressor, particularly at high loads, which would later be lost through throttling to adjust the boost pressure to the pressure requirements of the air lubrication system. Throttling losses can be efficiently avoided by alternately branching the charge air either downstream of the low-pressure compressor or downstream of the high-pressure compressor. This allows both the respective internal combustion engine and the air lubrication system, and thus ultimately the ship's propulsion system, to operate at high efficiency.

[0013] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1: A schematic of a section of a ship propulsion system.

[0014] Fig. Figure 1 shows a highly schematic representation of a ship's propulsion system 10. The ship's propulsion system 10 of the Fig. 1 comprises an internal combustion engine 11 with a plurality of cylinders 12. Fuel is combusted in the cylinders 12 of the internal combustion engine. The combustion of the fuel in the cylinders 12 produces exhaust gas A, which is discharged from the cylinders 12 and fed to an exhaust gas turbocharger system 13 with two exhaust gas turbochargers 13a, 13b. The internal combustion engine 11 can be a gas engine, a dual-fuel engine, a diesel engine, a methanol engine, an ammonia engine, or a hydrogen engine.

[0015] The exhaust gas turbocharger 13a is a high-pressure exhaust gas turbocharger with a high-pressure turbine 14a and a high-pressure compressor 15a. The exhaust gas turbocharger 13b is a low-pressure exhaust gas turbocharger with a low-pressure turbine 14b and a low-pressure compressor 15b. Exhaust gas A, which leaves the cylinders 12 of the internal combustion engine 11, first flows through the high-pressure turbine 14a of the high-pressure exhaust gas turbocharger 13a and then through the low-pressure turbine 14b of the low-pressure exhaust gas turbocharger 13b. Mechanical energy is generated in the turbines 14a, 14b of the exhaust gas turbochargers 13a, 13b, which is used to drive the respective compressor 15a, 15b of the respective exhaust gas turbocharger 13a, 13b. The high-pressure turbine 14a of the high-pressure exhaust gas turbocharger 13a drives the high-pressure compressor 15a and the low-pressure turbine 14b of the low-pressure exhaust gas turbocharger 13b drives the low-pressure compressor 15b.In the compressors 15a, 15b, charge air L is compressed, whereby the charge air L is first compressed in the low-pressure compressor 15b and then in the high-pressure compressor 15a.

[0016] Fig. Figure 1 further shows an air lubrication system 16 of the ship propulsion system 10 according to the invention. The air lubrication system 16 has several nozzles 17, by means of which air bubbles B can be blown or expelled beneath a ship's bottom. This can reduce the ship's resistance, i.e., the ship's friction in the water.

[0017] In accordance with the invention, the respective internal combustion engine 11 is coupled to the air lubrication system 16 via the exhaust gas turbocharger system 13 thereof, namely via the Fig. 1 shown branch lines 18a, 18b.

[0018] Compressed charge air in the high-pressure compressor 15a can be supplied to the air lubrication system 16 via a first branch line 18a, and compressed charge air in the low-pressure compressor 15b can be supplied via a second branch line 18b, with the respective charge air being expelled as charge air bubbles beneath the ship's bottom via the nozzles 17 of the air lubrication system 16. Thus, charge air from the high-pressure compressor 15a can be supplied to the air lubrication system 16 via the first branch line 18a, and charge air from the low-pressure compressor 15b can be supplied via a second branch line 18b. The first branch line 18a branches off downstream of the high-pressure compressor 15a, viewed in the flow direction of the charge air L, and the second branch line 18b branches off downstream of the low-pressure compressor 15b in the direction of the air lubrication system 16.

[0019] A valve 19a, 19b is operatively connected to each of the two branch lines 18a, 18b. When valve 19a, which is operatively connected to the first branch line 18a, is closed, the first branch line 18a is closed. When valve 19b, which is operatively connected to the second branch line 18b, is closed, the second branch line 18b is closed. However, if valve 19a is open, the first branch line 18a is open. If the second valve 19b is open, the second branch line 18b is open.

[0020] When the respective valve 19a, 19b is open, a portion of the charge air can be taken downstream of the respective compressor 15a, 15b of the respective exhaust gas turbocharger 13a, 13b via the respective open branch line 18a, 18b and fed to the air lubrication system 16.

[0021] The two branch lines 18a, 18b interact with a common air line 22. In this air line 22, Fig. 1, the valves 19a, 19b are integrated. At least one compressor 20 also cooperates with the air line 22. For example, if both valves 19a, 19b and thus both branch lines 18a, 18b are closed, air can be compressed via the at least one compressor 20 and supplied to the nozzles 17 of the air lubrication system 16.

[0022] Fig.1 further shows a control device 21, which is a component of the ship's propulsion system 10. The valves 19a, 19b can be controlled to open and close via the control device 21. The control of the valves 19a, 19b to open and close by the control device 21 preferably occurs depending on the load state of the respective internal combustion engine 11 and / or depending on the air quantity required by the air lubrication system 16 and / or depending on the air pressure required by the air lubrication system 16. Furthermore, the control device 21 also serves, in particular, to control the at least one compressor 20.

[0023] When the load of the respective internal combustion engine 11 is less than a limit value, preferably greater than a first limit value and less than a second limit value, it is provided in particular that the control device 21 controls the valve 19a to open and the valve 19b to close, so that charge air can then be taken downstream of the high-pressure compressor 15a and supplied to the air lubrication system 16, namely when the amount of charge air present downstream of the high-pressure compressor 15a is not fully required by the internal combustion engine 11.

[0024] When the load of the respective internal combustion engine 11 is greater than a limit value, preferably greater than the second limit value, i.e., when the respective internal combustion engine 11 is operating at a relatively high load, in particular at or near full load, the control device 21 controls valve 19a to close and valve 19b to open. In this case, charge air is then extracted, in particular downstream of the low-pressure compressor 15b, and supplied to the air lubrication system 16.

[0025] The branching of the charge air downstream of the low-pressure compressor 15b and downstream of the high-pressure compressor 15a preferably only occurs when the exhaust gas turbochargers 13a, 13b, with the valves 19a, 19b closed, would provide a charge air quantity that is not required by the respective internal combustion engine 11, i.e., when excess charge air is present. By selectively extracting the charge air downstream of the low-pressure compressor 15b or downstream of the high-pressure compressor 15a, the ship's propulsion system can be operated efficiently. This makes it possible to avoid excessive compression work by the high-pressure compressor 15a, particularly when the internal combustion engine 11 is operating at a relatively high load, particularly at or near full load. Furthermore, throttling losses can be avoided, which would otherwise arise if the charge air extracted downstream of the high-pressure compressor 15a for the air lubrication system 16 had to be throttled.

[0026] If no excess charge air is generated in the area of ​​the exhaust gas turbochargers 13a, 13b, namely in the area of ​​their compressors 15a, 15b, the valves 19a, 19b remain closed and the air for the air lubrication system 16 is provided exclusively via the at least one compressor 20. This is particularly the case when the load of the internal combustion engine 11 is less than the first limit value.

[0027] Also, if the amount of charge air discharged downstream of the low-pressure compressor 15b or downstream of the high-pressure compressor 15a in the direction of the air lubrication system 16 is too small, the at least one compressor 20 can be operated to supply the air lubrication system 16 with a sufficient amount of air having a corresponding pressure.

[0028] It is preferable to always open only one of the valves 19a, 19b. Therefore, if valve 19a is open, valve 19b is preferably closed. If, however, valve 19b is open, valve 19a is preferably closed. However, it is also possible to open both valves 19a, 19b simultaneously within a defined load range of the internal combustion engine 11, in which case valve 19a throttles the pressure of the charge air taken downstream of high-pressure compressor 15a to the pressure of the charge air taken downstream of low-pressure compressor 15b.

[0029] Particularly at full load, it is possible to operate the air lubrication system 16 exclusively via charge air, which is taken downstream of the low-pressure compressor 15b with the valve 19a closed and the valve 19b open and fed to the air lubrication system 16 via the second branch line 18b. In this case, at least one compressor 20 can be shut down or remain shut down.

[0030] The invention relates to the ship's propulsion system 10 and a method for operating the same. Depending on the load state of the respective internal combustion engine 11 and / or depending on the air quantity required by the air lubrication system 16 and / or depending on the air pressure required by the air lubrication system 16, charge air compressed in the high-pressure compressor 15a and / or charge air compressed in the low-pressure compressor 15b is expelled as charge air bubbles beneath the ship's bottom via the nozzles 17 of the air lubrication system 16.

[0031] Depending on the pressure level required by the air lubrication system 16 and the load condition of the respective internal combustion engine, charge air can be taken from or downstream of the high-pressure compressor 15a and / or downstream of the low-pressure compressor 15a and supplied to the air lubrication system 16.

[0032] The method for operating the ship's propulsion system provides, in particular, that when the respective internal combustion engine 11 is operated at a load greater than a limit value, preferably greater than a second limit value, compressed charge air is extracted downstream of the low-pressure compressor 15 and supplied to the air lubrication system 16. If the load is less than a limit value, preferably less than the second limit value but greater than a first limit value, compressed charge air is extracted downstream of the high-pressure compressor 15a and supplied to the air lubrication system 16. If the load of the respective internal combustion engine 11 is less than the first limit value, charge air is preferably not extracted downstream of the low-pressure compressor 15b or downstream of the high-pressure compressor 15a and supplied to the air lubrication system 16.If the load of the respective internal combustion engine 11 is lower than the first limit value, no excess charge air is generated in the area of ​​the exhaust turbochargers 13a, 13b. All charge air is then supplied to the cylinders 12. If no charge air is extracted and supplied to the air lubrication system 16 either downstream of the high-pressure compressor 15a or downstream of the low-pressure compressor 15b, and / or if the extracted charge air quantity and / or its charge air pressure supplied to the air lubrication system 16 is too low, air is supplied to the air lubrication system 16 via the at least one compressor 20 of the air lubrication system 16. List of reference symbols 10 Ship propulsion system 11 Internal combustion engine 12 cylinders 13 Exhaust gas turbocharger system 13a High-pressure exhaust turbocharger 13b Low-pressure exhaust turbocharger 14a High-pressure turbine 14b Low-pressure turbine 15a High-pressure compressor 15b Low-pressure compressor 16 Air lubrication system 17 Nozzle 18a branch line 18b branch line 19a Valve 19b Valve 20 compressor 21 Control device 22 Air line

Claims

[1] Ship propulsion system (10), with at least one internal combustion engine (11), wherein the respective internal combustion engine (11) has cylinders (12) in which exhaust gas is produced during the combustion of fuel, wherein the respective internal combustion engine (11) cooperates with at least two exhaust gas turbochargers (13a, 13b), namely at least one high-pressure exhaust gas turbocharger (13a) having a high-pressure turbine (14a) and a high-pressure compressor (15a), and one low-pressure exhaust gas turbocharger (13b) having a low-pressure turbine (14b) and a low-pressure compressor (15b), such that the exhaust gas of the cylinders (12) can be expanded in the respective turbine (14a, 14b) of the respective exhaust gas turbocharger (13a, 13b), and that during the expansion of the exhaust gas in the respective turbine (14a, 14b) of the respective exhaust gas turbocharger (13a, 13b) energy obtained can be used to drive the respective compressor (15a, 15b) of the respective exhaust gas turbocharger (13a, 13b) for compression of the cylinders (12) to drive the supplied charge air, with an air lubrication system (16), wherein the air lubrication system (16) has a plurality of nozzles (17) through which air bubbles can be ejected under a ship's bottom in order to reduce the ship's resistance, characterized by , that the respective internal combustion engine (11) is coupled to the air lubrication system (16) via branch lines (18a, 18b) in such a way that charge air compressed in the high-pressure compressor (15a) can be supplied to the air lubrication system (16) via a first branch line (18a) and charge air compressed in the low-pressure compressor (15b) can be supplied via a second branch line (18b), wherein the respective charge air can be expelled as charge air bubbles under the ship's bottom via the nozzles (17) of the air lubrication system (16), wherein the branch lines (18a, 18b) are operatively connected to a respective valve (19a, 19b) in such a way that when the respective valve (19a, 19b) is closed, the respective branch line (18a, 18b) is closed, and that when the respective valve (19a, 19b) is open, the the respective branch line (18a, 18b) is opened to supply part of the charge air to the air lubrication system (16), the air lubrication system (16) having at least one compressor (20),to compress air for the air lubrication system (16), wherein the at least one compressor (20) is operable when the respective valve (19a, 19b) is closed. [2] Ship propulsion system (10) according to claim 1, characterized by that the at least one internal combustion engine (11) is a gas engine or a dual-fuel engine or a diesel engine or a methanol engine or an ammonia engine or a hydrogen engine. [3] Ship propulsion system (10) according to claim 1 or 2, characterized by that the first branch line (18a) branches off downstream of the high-pressure compressor (15a) and the second branch line (18b) branches off downstream of the low-pressure compressor (15b) in the direction of the air lubrication system (16). [4] Ship propulsion system (10) according to one of claims 1 to 3, characterized bythat the branch lines (18a, 18b) open into a common air line (22) via which the charge air can be guided in the direction of the nozzles (17) of the air lubrication system (16). [5] Ship propulsion system (10) according to one of claims 1 to 4, characterized by a control device (21) which opens or closes the respective valve (19a, 19b) depending on the load state of the respective internal combustion engine (11) and / or depending on the amount of air required by the air lubrication system (16) and / or depending on the air pressure required by the air lubrication system (16). [6] Ship propulsion system (10) according to one of claims 1 to 5, characterized by that the at least one compressor (20) can be operated when, with the valve (19a, 19b) open in each case, the amount of charge air flowing via the respective branch line (18a, 18b) is too small. [7] Method for operating a ship propulsion system (10) according to one of claims 1 to 6, characterized bythat depending on the load state of the respective internal combustion engine (11) and / or depending on the amount of air required by the air lubrication system (16) and / or depending on the air pressure required by the air lubrication system (16), charge air compressed in the high-pressure compressor (15a) and / or charge air compressed in the low-pressure compressor (15b) is ejected as charge air bubbles under the ship's bottom via the nozzles (17) of the air lubrication system (16). [8] Method according to claim 7, characterized by , that when the load of the respective internal combustion engine (11) is less than a limit value, charge air is taken downstream of the high-pressure compressor (15a) and fed to the air lubrication system (16), when the load of the respective internal combustion engine (11) is greater than the limit value, charge air is taken downstream of the low-pressure compressor (15b) and fed to the air lubrication system (16). [9] Method according to claim 7 or 8, characterized by , that when the load of the respective internal combustion engine (11) is greater than a first limit value and less than a second limit value, charge air is taken downstream of the high-pressure compressor (15a) and fed to the air lubrication system (16), when the load of the respective internal combustion engine (11) is greater than the second limit value, charge air is taken downstream of the low-pressure compressor (15b) and fed to the air lubrication system (16). [10] Method according to claim 9, characterized by that when the load of the respective internal combustion engine (11) is less than the first limit value, charge air is neither taken downstream of the low-pressure compressor (15b) nor downstream of the high-pressure compressor (15a) and fed to the air lubrication system (16). [11] Method according to one of claims 7 to 10, characterized bythat charge air is taken either downstream of the high-pressure compressor (15a) or downstream of the low-pressure compressor (15b) and fed to the air lubrication system (16). [12] Method according to one of claims 7 to 11, characterized by that when no charge air is extracted and fed to the air lubrication system (16) either downstream of the high-pressure compressor (15a) or downstream of the low-pressure compressor (15b), and / or when the charge air quantity extracted and fed to the air lubrication system (16) and / or its charge air pressure is too low, air for the air lubrication system (16) is compressed via the at least one compressor (20) of the air lubrication system (16).

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