KR102315522B1 - Gaseous fuel supply system and method for operating the gaseous fuel supply system - Google Patents

Abstract

A system for supplying pressurized gaseous fuel to the main engine of a marine vessel and other gaseous fuel consumers of the marine vessel and a method of operating the gaseous fuel supply system.

Description

GASEOUS FUEL SUPPLY SYSTEM AND METHOD FOR OPERATING THE GASEOUS FUEL SUPPLY SYSTEM

The present invention relates to a gaseous fuel supply system for providing a supply of pressurized gaseous fuel to a large two-stroke uniflow scavenge internal combustion engine having a crosshead and a method of operating the gaseous fuel supply system.

A large two-stroke turbocharged single flow scavenging internal combustion engine with a crosshead is used as a propulsion system for a large marine vessel or a prime mover for a power plant. The two-stroke diesel engine is constructed differently from other internal combustion engines because of its enormous size.

Such large two-stroke turbocharged single flow scavenging internal combustion engines are increasingly using gaseous fuels such as, for example, liquefied natural gas (LNG) or liquefied petroleum gas (LPG) as fuel instead of, for example, marine diesel oil or heavy oil. This shift to gaseous fuels is driven primarily by the desire to reduce emissions and provide greener engines.

The evolution of gaseous fuel has led to the development of two different types of large two-stroke turbocharged internal combustion engines using gaseous fuel as the main fuel.

The first type of engine is a direct injection type in which gaseous fuel is injected at high pressure around top dead center (TDC) and ignited by compression (by high temperature by compression), and these engines operate according to a diesel cycle. The gaseous fuel is ignited at the moment it is injected into the combustion chamber, and there is no concern related to pre-ignition due to a low excess air rate or misfire due to a high excess air rate. The effective compression ratio of a gaseous fuel operated large two-stroke turbocharged internal combustion engine of the first type is equal to or higher than that of a conventional liquid fuel operated large two-stroke turbocharged internal combustion engine. Typically, the effective compression ratio of this type of engine is approximately 15-17, while the geometric compression ratio is approximately 30. The advantage of type 1 engines is that they are very fuel efficient due to their high compression ratio. Another advantage is the much lower risk of pre-ignition and misfire compared to type 2 engines.

However, to be able to inject gaseous fuel at or near TDC, the pressure of the gaseous fuel supplied to the fuel valve that injects the gaseous fuel into the fuel chamber must be significantly higher than the compression pressure in the combustion chamber. In practice, the gaseous fuel should be injected into the combustion chamber at a pressure of at least 250 bar, preferably at least 300 bar. The pump or pumping station increases the pressure of the liquefied gaseous fuel to, for example, 300 bar, and then the high-pressure liquefied fuel is vaporized in the high-pressure evaporation unit and delivered in gaseous form at high pressure to the fuel injection valve of the main engine. This supply system is expensive compared to the conventional liquid fuel supply system.

Gas fuels such as natural gas have very low energy density compared to conventional fuels. To be used as a convenient energy source, the density must be increased. This is done by cooling the gaseous fuel to cryogenic temperatures to produce natural gas, such as liquefied natural gas (LNG).

A gaseous fuel supply system for such a gas operated engine includes an insulated tank in which liquefied gas is stored and maintained in a liquid state for a long period of time. However, the heat flux generated in the surrounding environment raises the temperature inside the tank and vaporizes the liquefied gas. The gas produced in this process is called boil-off gas (BOG). Evaporation in the tank causes a significant steady flow of the gaseous fuel, which must be removed from the tank and disposed of. The amount of BOG that has to be processed by 180,000 m ³ LNG carriers is several tons per hour, typically about 3,000 kg/hour, and the gas power generation demand of this type of LNG carrier main engine is about 4,000 kg/hour (when all of the energy of the main engine is practically assumed to be natural gas).

Increasing the pressure of this boil-off gas to an injection pressure of about 300 bar using a compressor is technically very demanding, so BOG cannot be used as a fuel for a large two-stroke turbocharged internal combustion engine with high-pressure gas injection of the first type.

A compressor can be used to increase the pressure of the BOG to eg 10-20 bar, and at this pressure it is possible to run on gaseous fuel, for example a generator set associated with a large two-stroke turbocharged internal combustion engine typically installed on marine vessels. (The generator set is a four-stroke internal combustion engine significantly smaller than a large two-stroke turbocharged internal combustion engine, and the generator set is used to drive a generator/alternator for power and heat production for marine vessels).

Alternatively, the boil-off gas may be liquefied back to, for example, a cryogenic generator. However, reliquefaction requires expensive equipment and consumes a significant amount of energy.

As a last resort, you can simply burn the boil-off gas.

WO2016058611A1 discloses a large two-stroke turbocharged single flow scavenging internal combustion engine of the first type.

DK201670361A1 discloses a gas supply system for delivering high-pressure gaseous fuel for high-pressure injection into a combustion chamber together with a large two-stroke turbocharged single flow scavenging internal combustion engine of the first type.

An engine of the second type is a so-called low pressure gas engine in which gaseous fuel is mixed with scavenging air, and this second type of engine compresses a mixture of gaseous fuel and scavenging air in a combustion chamber. In this second type of engine, gaseous fuel is introduced by means of a fuel valve disposed inward along the length of the cylinder liner. That is, it flows in during the upward stroke of the piston before the exhaust valve closes. The piston compresses a mixture of gaseous fuel and scavenging air in the combustion chamber, and ignites the compressed mixture at or near top dead center (TDC) with a timed ignition means such as, for example, pilot oil injection. The advantage of this type 2 engine is that it can be operated with gaseous fuel supplied at a relatively low pressure (eg 15 bar). This is because the pressure in the combustion chamber is relatively low when gaseous fuel is introduced. Thus, the second type of engine can be operated with increased pressure BOG using a compressor station. Accordingly, a gas supply system for an engine of the second type may be less expensive than a gas supply system required for an engine of the first type. In particular, the gas supply system for the first type of engine must be able to handle the BOG stream produced by the tank, but the boiler and generator sets can only handle a portion of this BOG stream, so the relatively expensive liquefaction system of the first type It must be installed and operated in the engine's gas fuel supply system.

However, because the second type of engine compresses the mixture in the combustion chamber, it is necessary to operate with a significantly lower effective compression ratio compared to the first type of engine. Generally, engines of the first type operate with an effective compression ratio of about 15 to about 17, while engines of the second type operate with an effective compression ratio of about 7 to about 9, and the geometric compression ratio of engines of the second type is approximately 13.5. am. Significantly lower geometrically determined compression ratios result in significantly lower energy efficiency of engines of the second type compared to engines of the first type, and also a lower maximum for engines of the second type compared to engines of a first type of similar size. resulting in continuous rated output.

In addition, the second type of engine generally requires a prechamber and a timed ignition system to provide stable ignition.

Other disadvantages of type 2 engines are to avoid pre-ignition due to (locally) too low an excess air rate and/or too high bulk temperature and to avoid misfire due to too high an air excess rate and/or too low bulk temperature. During the upstroke, the excess air rate in the combustion chamber and the bulk temperature must be controlled very precisely. Proper mixing to produce a homogeneous mixture is important to avoid local conditions that can cause pre-ignition or misfire in the combustion chamber. Controlling these conditions in the combustion chamber is particularly difficult in transient operation.

KR20130051539 discloses an engine according to the preamble of claim 1 and a method according to the preamble of claim 6 .

No. DK201770703 discloses a large two-stroke turbocharging single flow scavenging internal combustion engine comprising the second type.

Consequently, there is a need for a large two-stroke turbocharged single flow scavenging internal combustion engine capable of operating on gaseous fuel as a primary fuel that overcomes or at least reduces the disadvantages of the first and second type engines described above.

In addition, gas to a large two-stroke turbocharged single-flow scavenging internal combustion engine that provides gaseous fuel at a pressure that can be used for combustion of a large two-stroke turbocharged single flow scavenging internal combustion engine that overcomes or at least reduces the disadvantages of the gas supply system described above. A gas supply system is required to supply fuel.

Patent Document 1: WO 2016058611A1 Patent Document 2: DK No. 201670361A1 Patent Document 3: DK No. 201770703 Patent Document 4: Republic of Korea Patent Publication No. 10-2013-0051539

It is an object to provide a method as well as an engine and gaseous fuel supply system that overcomes or at least reduces the aforementioned problems.

The above and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims and from the detailed description and drawings.

According to a first aspect, there is provided a system for supplying pressurized gaseous fuel to a main engine of a marine vessel and other consumers consuming gaseous fuel in the marine vessel, the system comprising:

A storage tank for storing liquefied gaseous fuel under cryogenic conditions; a high-pressure cryogenic pump unit having an inlet connected to the storage tank for supplying the liquefied gaseous fuel to the high-pressure pump; and a first supply conduit connected to an outlet of the high-pressure cryogenic pump unit; and a high-pressure carburetor; and a boil-off gas conduit connecting the boil-off gas outlet of the storage tank to the inlet of the compressor unit to convey the boil-off gas stream to the compressor unit; and a first heat exchanger; and a stream of pressurized gaseous fuel. a compressor unit for increasing the pressure of the boil-off gas stream to produce a second supply conduit connected to the outlet of the compressor unit for conveying a first portion of the pressurized gaseous fuel stream to one or more pressurized gaseous fuel consumers; connected to the outlet of the compressor unit for passing a second portion of the pressurized gaseous fuel stream through a first heat exchanger exchanging heat with boil-off gas flowing through the first heat exchanger, followed by a second portion of the pressurized gaseous fuel stream a reliquefaction conduit for passing through the high pressure carburetor to exchange heat with a stream of high pressure liquefied or vaporized gaseous fuel flowing through the high pressure carburetor, wherein the first supply conduit extends from the outlet of the high pressure cryogenic pump unit and the high pressure passing the high pressure carburetor and passing the stream of high pressure liquefied gaseous fuel through the carburetor into a high pressure gaseous fuel stream for the main engine to carry the liquefied gaseous fuel stream; The boil-off gas conduit is characterized in that it passes through the first heat exchanger for exchanging the stream of boil-off gas in the first heat exchanger.

By cooling a portion of the pressurized gaseous fuel stream from the compressor using the boil-off gas stream in a heat exchanger and the vapor of the high-pressure gaseous fuel in a high-pressure vaporizer, a portion of the boil-off gas is converted into complex and expensive dedicated reliquefaction equipment. It can be reliquefied without the use of thermal energy and heat energy that would otherwise be wasted can be used in the reliquefaction process.

In a possible implementation form of the first aspect, the system comprises a throttling device, such as an expansion valve, in a reliquefaction conduit downstream of the high pressure vaporizer for dispensing a stream of the second portion of the pressurized gas stream. By passing a stream of pressurized gaseous fuel through throttling, the temperature and pressure of the gaseous fuel are greatly divided, increasing the reliquefaction fraction.

In a possible implementation form of the first aspect, the system is a throttle or downstream of the high pressure carburetor for collecting the liquefied gaseous fuel produced by the cooling effect of the high pressure carburetor and/or throttling process and for separating the excess gaseous fuel from the reliquefied gaseous fuel. and a separation vessel connected to the reliquefaction conduit downstream of the ring apparatus.

In a possible implementation form of the first aspect, the system connects the liquid outlet of the separation vessel to the inlet of the storage tank for carrying the reliquefied gaseous fuel to the storage tank and comprising a gas recirculation conduit connecting the gas outlet of the separation vessel to a boil-off gas conduit. and a reliquefaction gas conduit connecting to the

In a possible implementation form of the first aspect, the system comprises a heater in the first feed conduit downstream of the high pressure carburetor for heating the stream of high pressure gaseous fuel prior to feeding the stream of high pressure gaseous fuel to the main engine.

In a possible implementation form of the first aspect, the main engine is one of the consumers of pressurized gaseous fuel.

According to a second aspect, supplying the high-pressure gaseous fuel in the marine vessel main engine, there is provided a method for supplying a stream of pressurized gas fuel consumer to consume the pressurized gaseous fuel in the marine vessel, the method comprising the following steps: include

storing the liquefied gaseous fuel at cryogenic conditions; and pumping the liquefied gaseous fuel stream obtained from the stored liquefied gaseous fuel with a high pressure pump to produce a stream of high pressure liquefied gaseous fuel; and gasifying the high pressure liquefied gaseous fuel stream. vaporizing a stream of fuel; supplying a stream of high pressure gaseous fuel to a main engine; and directing a boil-off gas stream from the stored liquefied gaseous fuel through a compressor to produce a stream of pressurized gaseous fuel. and supplying a first portion of the pressurized gaseous fuel stream from the compressor to a pressurized gaseous fuel consumer; and directing a second portion of the pressurized gaseous fuel stream from the compressor into a reliquefaction conduit; exchanging the second part with the boil-off gas stream and then exchanging the second part with the stream of high-pressure liquefied gaseous fuel.

The advantages of the method according to the second aspect are the same as those of the system according to the first aspect.

In a possible implementation form of the second aspect, the method comprises reliquefying at least a third portion of the second portion and feeding the third portion to the stored liquefied gaseous fuel.

In a possible implementation form of the second aspect, the method comprises adding a residual gas portion of the second portion to the boil-off gas stream.

In a possible implementation form of the second aspect, the method comprises passing the second part through a throttling device.

As described above, according to the present invention as described above, there is an advantage in that it is possible to provide a method as well as an engine and gaseous fuel supply system that overcomes or at least reduces the above-described problems.

1 is a front view of a large two-stroke engine according to an exemplary embodiment;
Fig. 2 is a side view of the large two-stroke engine of Fig. 1;
3 is a first schematic view of a large two-stroke engine according to FIG. 1 ;
4 is a cross-sectional view of the cylinder frame and cylinder liner of the engine of FIG. 1 including the cylinder cover and the exhaust valve mounted to the cylinder cover and the piston shown in both TDC and BDC.
5 is a graph illustrating gas exchange and fuel injection cycles.
6 is a schematic diagram of a gaseous fuel supply system according to an embodiment;
7 is a schematic diagram of a gaseous fuel supply system according to another embodiment;
8 is a cross-sectional view of a cylinder frame and a cylinder liner according to another embodiment.

In the following detailed description, the internal combustion engine will be described with reference to a large two-stroke low-speed turbocharged internal combustion crosshead engine of an exemplary embodiment. 1 , 2 and 3 show an embodiment of a large low speed turbocharged two-stroke internal combustion engine with a crankshaft 8 and a crosshead 9 . 1 and 2 are a front view and a side view, respectively. 3 is a schematic diagram of a large low-speed turbocharged two-stroke diesel engine with intake and exhaust system; In this exemplary embodiment, the engine has four cylinders arranged in rows. Large, low-speed turbocharged two-stroke internal combustion engines typically have four to fourteen cylinders in rows, supported by an engine frame (11). This engine can be used, for example, as a stationary engine for operating a main engine of a marine vessel or a generator of a power plant. The total power of this engine may range, for example, from 1,000 to 110,000 kW. The engine combines gaseous fuel as the main fuel for the diesel cycle and Otto cycle in operating mode. This is because it compresses the air-fuel mixture which is ignited by compression but forms a first amount of pressurized gaseous fuel that is introduced during the compression stroke of the piston 10 . The compressed air-fuel mixture is ignited when a second amount of high pressure gas house fuel is injected at or near the TDC.

Other modes of operation of the engine may operate according to the diesel cycle in which no fuel is introduced during the compression stroke and all fuel is injected at or near TDC, this mode may also have gaseous fuel as the main fuel. In another mode of operation, the engine may be operated according to an Otto cycle in which all gaseous fuel is mixed with scavenging and the air-fuel mixture is compressed during a compression stroke and temporal ignition is provided at or near TDC.

The engine, in this exemplary embodiment, is a two-stroke single flow scavenging type engine with a scavenging port 18 in the lower region of the cylinder liner 1 and a central exhaust valve 4 at the top of the cylinder liner 1 . . Accordingly, the combustion chamber is divided into a cylinder liner 1, a piston 10 and a cylinder cover 22 arranged to reciprocate in the cylinder liner between bottom dead center BDC and top dead center TDC.

The scavenging air passes from the scavenging receptacle 2 through the scavenging port 18 at the bottom of the individual cylinder 1 when the piston is below the scavenging port 18 . When the piston is moving upward and before passing through the fuel valve 30 , gaseous fuel is introduced from the gaseous fuel inlet valve 30 under the control of the electronic controller 60 . The fuel valve 30 is preferably uniformly distributed around the circumference of the cylinder liner and is arranged somewhere in the central region of the length of the cylinder liner 1 . Thus, the inflow of gaseous fuel occurs when the compression pressure is relatively low, ie when the piston reaches TDC and is much lower than the compression pressure.

A piston (10) in the cylinder liner (1) compresses the charge gaseous fuel and scavenging, and at or near the TDC, the high-pressure gaseous fuel is injected through the fuel injection valve (50). Ignition is triggered according to the diesel principle by high temperature caused by high pressure near the combustion chamber or TDC and is injected with gaseous fuel by means of a fuel injection valve 50 or a dedicated pilot oil preferably arranged in the cylinder cover 22 . It may be assisted by a third small amount of pilot oil (or any other suitable ignition fluid) delivered by fuel valve 51 (not shown).

“At or near TDC” means the range including the injection of gaseous fuel where the piston begins at the earliest at about 15 degrees before TDC and ends at about 40 degrees after TDC at the latest.

Then, combustion proceeds and exhaust gas is produced. An alternative type of ignition system, such as a prechamber (not shown), laser ignition (not shown) or glow plug (not shown), may be used instead of or in addition to the pilot oil fuel valve 50 . It can also be used to start ignition.

When the exhaust valve 4 is opened, the exhaust gas flows to the exhaust gas receiving part 3 through the exhaust duct coupled to the cylinder 1, and continues through the first exhaust conduit 19 of the turbocharger 5. After flowing into the turbine 6 , this exhaust gas is discharged to the outlet 21 and the atmosphere via the economizer 20 through the second exhaust conduit. The turbine 6 drives a compressor 7 to which fresh air is supplied via an air inlet 12 via a shaft. This compressor 7 delivers pressurized scavenging air to the scavenging air conduit 13 leading to the scavenging air receiver 2 . The scavenging air in this conduit 13 passes through an intercooler 14 for cooling of the scavenging air.

If the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2 , ie under low or partial load conditions of the engine, the cooled scavenging air presses the scavenging air flow in the electric motor 17 . ) passes via an auxiliary blower 16 driven by At higher engine loads, the turbocharger compressor (7) delivers sufficiently compressed scavenging air, and then the auxiliary blower (16) is bypassed via the non-return valve (15).

3 shows a controller 60, for example an electronic control unit, connected to the engine components controlled by the controller 60 and sensors providing information about the operating conditions of the engine to the controller via signal lines or other communication channels. show One of the sensors is shown in the form of a crank angle sensor, which informs the controller 60 of the rotation angle of the crankshaft 8 . The controller 60 controls the operation of the fuel inlet valve 30 , the fuel injection valve 50 , and the exhaust valve 4 .

A controller 60 is connected to and controls the fuel inlet valve 30 and the fuel injection valve 50 , wherein the controller 60 controls at least one from the second pressurized gaseous fuel source 35 during the piston stroke from BDC to TDC. actuating the fuel inlet valve to introduce a first amount of gaseous fuel into the combustion chamber and a second from a pressurized first high pressure gaseous fuel source 35 into the at least one combustion chamber when the piston 10 is at or near the TDC. configured to actuate the fuel injection valve 50 to inject a quantity of gaseous fuel.

4 shows a cylinder liner 1 generally designated for large two-stroke crosshead engines. Depending on the engine size, the cylinder liner 1 can be manufactured in different sizes, typically with a cylinder bore in the range from 250 mm to 1000 mm and a corresponding typical length in the range from 1000 mm to 4500 mm. In Fig. 4, the cylinder liner 1 is shown mounted on a cylinder frame 23 with a cylinder cover 22 disposed on top of the cylinder liner 1 with an airtight interface therebetween.

4 , the piston 10 is schematically shown with dashed lines at both bottom dead center (BDC) and top dead center (TDC), but of course these two positions do not occur simultaneously and are separated by a 180 degree rotation of the crankshaft 8 it is clear that it will be The cylinder liner 1 is provided with a cylinder lubrication hole 25, which provides a supply of cylinder lubricating oil when the piston 10 passes through the lubrication line 24, and a cylinder lubrication line 24, followed by a piston ring (not shown). city) distributes cylinder lubricating oil to the working surface of the cylinder liner.

A fuel injection valve 50 (typically two or three fuel injection valves 50 distributed circumferentially around the exhaust valve 4 per cylinder) is mounted to the cylinder cover 22 to provide a first supply conduit ( It is connected to a first high pressure gaseous fuel source 35 via 36 ) and to a supply of pilot oil 27 via a pilot line 28 .

The amount of the third ignition liquid forms less than 5%, preferably less than 3% of all fuel heating value delivered to the combustion chamber during a given engine cycle.

The fuel injection valve 50 may be of the type disclosed in DK178519B1, which can inject a significant amount of high-pressure gaseous fuel into the combustion chamber along with a small amount of pilot oil.

The timing of injection of high-pressure gaseous fuel and pilot oil by the fuel injection valve 50 is controlled by the controller 60, and the controller 60 operates the fuel injection valve 50 through a signal line schematically indicated by a dotted line in FIG. is connected to

The fuel inlet valve 30 is installed in the cylinder liner in which the nozzle/inlet opening is substantially flush with the rear end of the fuel valve 30 protruding from the inner surface of the cylinder liner 1 and the outer wall of the cylinder liner 1 . Typically, each cylinder liner 1 distributed circumferentially around the cylinder liner 1 is provided with one or two, or possibly up to three or four fuel inlet valves 30 . The fuel inlet valve 30 is arranged substantially midway along the length of the cylinder liner 1 in one embodiment.

The inflow of medium pressure gaseous fuel by the fuel inlet valve 30 is controlled by the controller 60, and the controller 60 in one embodiment through the signal line schematically shown in FIG. 3 through the fuel inlet valve ( 30) is connected.

The engine is configured to introduce a first amount of pressurized gaseous fuel and inject a second amount of high pressure gaseous fuel within a single engine cycle, ie.

That is, the second amount of high pressure gaseous fuel is injected in the first instance when the piston reaches TDC after introducing the first amount of pressurized gaseous fuel.

4 shows a first high-pressure gaseous fuel supply 35 connected to each fuel injection valve 50 in the cylinder cover 22 via a first supply conduit 36 and a fuel supply conduit 41 respectively. The gas supply system of an engine with a second medium pressure gaseous fuel supply 40 connected to the inlet of the gaseous fuel valve 30 is shown in a schematic and simplified manner.

In one embodiment, the high pressure P1 of the first high pressure gaseous fuel source 35 may be approximately 15-45 MPa (150-450 bar) such that the gaseous fuel overcomes the peak compression pressure and is injected at or near the TDC. make it possible In one embodiment, the intermediate pressure P2 of the second high pressure gaseous fuel source 35 may be approximately 1-3 MPa (10-30 bar), allowing gaseous fuel to be introduced during the compression stroke.

5 shows the opening and closing period of the scavenging port 18, the exhaust valve 4, the fuel inlet valve 30 (GA fuel valve) and the fuel injection valve 50 (GI fuel valve) at the crank angle (the angle of the crankshaft) 8)) as a function of the graph. The graph shows that the window for introducing the gaseous fuel is relatively short, allowing a very short time for the gaseous fuel to mix with the scavenging air in the combustion chamber. This very short window allows gaseous fuel. High-pressure gaseous fuel is injected into a window around the TDC. The total amount of gaseous fuel delivered (injected and injected) per engine cycle is determined by the engine load. The total amount of gaseous fuel delivered is the sum of a first amount of gaseous fuel entering the cylinder at pressure P2 and a second amount of high pressure gaseous fuel injected into the cylinder at pressure P1. In one embodiment, up to approximately 70 or 80% of the gaseous fuel heating value delivered to the cylinder is gaseous fuel introduced from the second pressurized gaseous fuel source 40 at pressure P2. In one embodiment, up to approximately 70 or 80% of the gaseous fuel heating value delivered to the cylinder is gaseous fuel injected from the second source of high pressure gaseous fuel 35 at pressure P2.

Accordingly, the ratio between the first gaseous fuel amount and the second gaseous fuel amount may be adjusted to match the available fuel amount of each gaseous fuel source. That is, when relatively little high-pressure fuel is available in the first source, the engine will inject a relatively large amount of medium-pressure gaseous fuel into the cylinder from the second pressurized gaseous fuel source 40 during the compression stroke and injected at or near the TDC. It can operate with relatively small amounts of high-pressure gaseous fuel. On the other hand, when relatively little intermediate pressurized gaseous fuel is available from the second pressurized gaseous fuel source 40 , the engine will produce a relatively large amount of high-pressure gaseous fuel from the first high-pressure gaseous fuel source injected into the cylinder at or near the TDC. and a relatively small amount of fuel from the second pressurized gaseous fuel source introduced into the cylinder during the compression stroke.

6 is a schematic diagram of a gas supply system that may be used to supply gaseous fuel to a large two-stroke turbocharged internal combustion engine, such as the engine shown in FIGS. The gas supply system is installed in one embodiment on a liquefied gas tanker, ie a marine vessel carrying large quantities of liquefied gaseous fuel, such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG).

The gas supply system uses the pressurized gaseous fuel to the main engine of a marine vessel and a set of generators for producing heat and power for other consumers of gas fuel in marine vessels, such as marine vessels (generator sets are usually significantly smaller than the main engine and require a generator/alternator). It is a four-stroke internal combustion engine powered by a gas engine), especially when the main engine is shut down (eg when a marine vessel is in port for cargo transport) or is configured to supply boilers running on gaseous fuel.

The gas supply system is also configured to supply the high pressure gaseous fuel to the main engine for injecting the gaseous fuel at or near the TDC.

Accordingly, the gas supply system comprises a second pressurized gaseous fuel source, denoted by reference numeral 40 (indicated by the dashed rectangle in FIG. 6 ) for providing gaseous fuel at a pressure P2 (eg 10-30 bar). Accordingly, the gas supply system comprises a first high-pressure gaseous fuel source, denoted by reference numeral 35 (indicated by the dashed rectangle in FIG. 6 ) for providing gaseous fuel at a pressure P1 (eg 150 to 30 bar).

The gaseous fuel supply system comprises one or more (adiabatic) storage tanks 26 and a high pressure cryogenic pump unit 37 for storing liquefied gaseous fuel in cryogenic conditions. The inlet of the high pressure cryogenic pump unit 37 is connected to a storage tank for supplying liquefied gaseous fuel to the high pressure cryogenic pump unit 37 . The stream of cryogenic liquefied gaseous fuel to the high pressure cryogenic pump generally has a pressure between slightly above zero and 10 bar, such as a pressure of about 5 bar and a temperature of, for example, about 110K.

A first supply conduit (36) is connected to the outlet of the high pressure cryogenic pump unit (37) and carries a high pressure liquefied gaseous fuel stream from the high pressure cryogenic pump unit (37) through a high pressure vaporizer (38), said high pressure vaporizer (38). In , a stream of high-pressure (vaporized) gaseous fuel passes through a heater 39 and then is conveyed to the high-pressure fuel injection system of the main engine. Heating the stream of high-pressure gaseous fuel in the heater 39 is optional, as the gaseous fuel delivered to the injection system of the main engine is processed by the injection system. It may be necessary to ensure that it warms up sufficiently (this often requires an increase in the temperature of the stream high pressure gaseous fuel, depending on the material used and the configuration of the injection system, as the injection system is generally not suitable for handling cryogenic temperatures). .

The stream of high pressure gaseous fuel leaving the high pressure cryogenic pump unit 37 generally has a temperature between 150 and 450 bar, such as 350 bar and for example about 119K.

The stream of high pressure (vaporized) gaseous fuel leaving the high pressure vaporizer 38 generally has a temperature between 150 and 450 bar, such as 350 bar and eg about 154K. After passing through heater 39, the temperature of the high-pressure gaseous fuel stream has a substantially unchanged pressure and, for example, a temperature of about 318K.

Thus, the stream of high pressure liquefied gaseous fuel in an embodiment has a pressure in excess of 150 bar and passes through a high pressure carburetor 38 to convert the high pressure liquefied gaseous fuel stream into a stream of high pressure gaseous fuel for injection in the main engine.

A boil-off gas conduit 42 connects the boil-off gas outlet of the storage tank to the inlet of the compressor unit 48 to convey the boil-off gas stream to the compressor unit. A first heat exchanger 43 is arranged in the boil-off gas conduit 42 to raise the temperature of the boil-off gas stream going to the compressor unit 48 . In one embodiment, the pressure of the boil-off gas in the boil-off gas conduit 42 is approximately 1 bar, for example, has a temperature of about 140K. After passing through the heat exchanger 43, the temperature rises to, for example, about 230K.

Compressor unit 48 raises the pressure of the boil-off gas stream to produce a stream of pressurized gaseous fuel at the outlet, for example at a pressure of about 15 bar and a temperature of about 318 K. Compressor unit 48 In one embodiment, it may be a compressor once or a multi-stage compressor unit (as shown) and includes a cooler 45 after each stage.

The second supply conduit 41 is for example connected to one or more consumers of pressurized gaseous fuel (eg, a main engine for the introduction of pressurized gaseous fuel during a compression stroke, or a generator set or boiler via generator supply conduit 47). It is connected to the outlet of the compressor unit 48 for carrying a first portion of the pressurized gaseous fuel stream.

A reliquefaction conduit 46 is also connected to the outlet of the compressor unit 48 and a second portion of the gaseous fuel stream pressurized through the heat exchanger 43 for exchanging heat with boil-off gas flowing through the heat exchanger 43 . and then passing the stream of pressurized gaseous fuel through the high pressure vaporizer 38 to exchange heat with the stream of high pressure liquefied or vaporized gaseous fuel flowing through the high pressure vaporizer 38 . After the stream of pressurized gaseous fuel has passed through the heat exchanger 43, for example, the temperature is 159 K and the substantially unchanged pressure is about 15 bar. After pressurizing a stream of pressurized gaseous fuel through a high-pressure vaporizer 38, it is cooled by the vaporized stream of high-pressure gaseous fuel, eg, having a temperature of 122 K and a substantially unchanged pressure of about 15 bar, and reliquefaction. Most of the pressurized gaseous fuel stream in conduit 46 is reliquefied.

Downstream of the high pressure vaporizer 38 , a reliquefaction conduit 46 is connected to the separation vessel 32 for collecting the liquefied gaseous fuel produced by the cooling effect of the high pressure vaporizer 38 . Separation vessel 32 separates the still gaseous fuel in the form of a reliquefied gaseous fuel. A reliquefaction gas conduit 33 connects the liquid outlet of the separation vessel 32 to the inlet of the storage tank 26 for conveying the reliquefied gaseous fuel to the storage tank 26 . A gas recirculation conduit 34 connects the gas outlet of the separation vessel 32 to a boil-off gas conduit 42 so that residual gaseous fuel can participate in another liquefaction cycle. 7 shows another embodiment of a gaseous fuel supply system essentially identical to the gas supply system according to the embodiment of FIG. 6 ; In the embodiment of FIG. 7 , structures and features that are the same as or similar to corresponding structures and features previously described or shown herein are denoted by the same reference numerals as previously used for the sake of simplicity.

In this embodiment, the reliquefaction conduit 46 has a throttling device 29, such as an expansion valve 29, added between the vaporizer 38 and the separation vessel 32 to throttle a second portion of the pressurized gas stream. Submit to the ring course.

The throttling device 29 is an expansion valve 29 in one embodiment. The throttling device 29 provides an additional cooling effect, the Joule-Thomson effect (also called the Joule-Kelvin effect, also called the Kelvin-Joule effect). The Joule-Thomson effect forces the temperature change of a real gas or liquid (as distinct from an ideal gas) to be insulated through a valve or porous plug so that no heat is exchanged with the environment. This procedure is called the throttling process or the Joule-Thomson process. Gaseous fuels such as natural gas or petroleum gas are cooled by expansion by the Joule-Thomson process as they are throttled through an orifice. Gas cooling throttling processes are commonly used in cooling processes such as air conditioners, heat pumps and liquefaction units.

Liquefaction of boil-off gas in gaseous fuel supply systems is generally similar to the Hampson-Linde cycle used for liquefaction of gases. The Hampson-Linde cycle depends on the Joule-Thomson effect and performs the following steps:

1) heating the pressurized gaseous fuel by compression in the compressor unit 48 to provide what is needed to pass through the cycle by adding external energy;

2) cooling the gas by returning it from the next (and last) stage in the heat exchanger 43;

3) immersing the gas in a cooler environment and losing some of its heat (and energy) in the high pressure vaporizer 38;

4) Passing the gas through a Joule-Thompson orifice to remove heat but further cooling by conserving energy that is potential energy rather than kinetic energy.

Most of the gaseous fuel is reliquefied and the remaining gaseous fuel, which is the coolest in the current cycle, is recirculated and sent back to the compressor unit 48, heated as it participates as a coolant in the heat exchanger 43, and sent back to the next cycle. and is reheated by compression in the compressor unit (48).

The gas supply system consists of a compressor providing a pressure of about 10 to 20 bar capable of handling all boil-off gas generated by the storage tank and a high-pressure gasification system providing 30-50% of the total amount of fuel required by the engine at full engine load. It can be relatively simplified.

The gas supply system has inherent redundancy, reducing costs by avoiding separate redundant systems.

Fig. 8 shows another embodiment of a large two-stroke turbocharged internal combustion engine essentially identical to the gas supply system according to the embodiment of Figs. In the embodiment of FIG. 8 , structures and features that are the same as or similar to corresponding structures and features previously described or illustrated herein are denoted by the same reference numerals as previously used for the sake of simplicity. The main difference of this embodiment with respect to the embodiment of FIGS. 1-4 is that the gaseous fuel inlet valve 30 is arranged in the cylinder cover 22 . This embodiment allows all fuel valves 30 , 50 to be located within the cylinder cover 22 .

Various aspects and embodiments have been described in connection with various embodiments herein. However, other modifications to the disclosed embodiments may be understood and effected by those skilled in the art upon practicing the claimed subject matter upon a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plural. A single processor, controller, or other unit may perform the functions of several items recited in the claims. The mere fact that certain measures are recited in different dependent claims does not indicate that these combinations cannot be used to advantage. Reference signs used in the claims should not be construed as limiting the scope.

1: cylinder liner
4: exhaust valve
10: piston
18: Sogipot
26: storage tank
36: first supply conduit
37: high pressure cryogenic pump unit
38: high pressure carburetor
41: second supply conduit
42: boil-off gas conduit
43: first heat exchanger
46: reliquefaction conduit
48: compressor unit

Claims (9)

A system for supplying pressurized gaseous fuel to a main engine of a marine vessel and other consumers consuming the gaseous fuel of the marine vessel, the system comprising:
a storage tank 26 for storing liquefied gaseous fuel in cryogenic conditions;
the high pressure cryogenic pump unit (37) having an inlet connected to the storage tank for supplying liquefied gaseous fuel to the high pressure cryogenic pump unit (37);
a first supply conduit (36) connected to the outlet of the high pressure cryogenic pump unit (37);
high pressure vaporizer 38;
a boil-off gas conduit (42) connecting the boil-off gas outlet of the storage tank (26) to the inlet of a compressor unit (48) for conveying a stream of boil-off gas to the compressor unit (48);
a first heat exchanger 43;
a second supply conduit (41) connected to an outlet of said compressor unit (48) for conveying a first portion of said pressurized gaseous fuel stream to said one or more pressurized gaseous fuel consumers;
the compressor unit (48) for passing a second portion of the pressurized gaseous fuel stream through the first heat exchanger (43) exchanging heat with the boil-off gas flowing through the first heat exchanger (43) a reliquefaction conduit connected to the outlet of 46);
connected to the reliquefaction conduit 46 downstream of the high pressure carburetor 38 to collect the liquefied gaseous fuel produced by the cooling effect of the high pressure carburetor 38 and separate excess gaseous fuel from the reliquefied gaseous fuel separation vessel (32);
The compressor unit (48) is a multi-stage compressor unit, comprising a cooler (45) after each stage,
The first supply conduit 36 extends from the outlet of the high pressure cryogenic pump unit 37 and passes through the high pressure vaporizer 38 to convey a stream of high pressure liquefied gaseous fuel through the high pressure vaporizer 38 . directing a stream of high pressure liquefied gaseous fuel into a high pressure gaseous fuel stream for said main engine;
the boil-off gas conduit (42) passes through the first heat exchanger (43) for exchanging the stream of boil-off gas in the first heat exchanger (43); and
The compressor unit 48 consumes pressurized gaseous fuel to the main engine of the marine vessel and the gaseous fuel of the marine vessel, characterized in that it increases the pressure of the stream of boil-off gas to produce a stream of pressurized gaseous fuel. system that supplies to other consumers. According to claim 1,
a throttling device (29) in the reliquefaction conduit (46) downstream of the high pressure carburetor (38) for submitting the stream of pressurized gaseous fuel to a throttling process. A system for supplying engines and other consumers consuming gaseous fuel of the marine vessel. 3. The method of claim 2,
The throttling device or downstream of the high pressure carburetor 38 or the high pressure carburetor 38 for collecting the liquefied gaseous fuel produced by the cooling effect of the throttling process and separating the excess gaseous fuel from the reliquefied gaseous fuel A system for supplying pressurized gaseous fuel to the main engine of a marine vessel and other consumers consuming the gaseous fuel of the marine vessel, comprising a separation vessel (32) connected to the reliquefaction conduit (46) downstream of (29) . 4. The method of claim 3,
the separation vessel (32) for carrying reliquefied gaseous fuel to the storage tank (26) and including a gas recirculation conduit (34) connecting the gas outlet of the separation vessel (32) to the boil-off gas conduit (42) supplying pressurized gaseous fuel to the main engine of the marine vessel and other consumers consuming the gaseous fuel of the marine vessel, comprising a reliquefaction gas conduit (33) connecting the liquid outlet of the storage tank (26) to the inlet of the storage tank (26). system that does. According to claim 1,
a heater (39) in the first supply conduit (36) downstream of the high pressure carburetor (38) for heating the stream of high pressure gaseous fuel prior to supplying the stream of high pressure gaseous fuel to the main engine. A system for supplying gaseous fuel to the main engine of a marine vessel and other consumers that consume the gaseous fuel of the marine vessel. A method of supplying a high pressure gaseous fuel to a main engine of a marine vessel and supplying a stream of a pressurized gaseous fuel consumer that consumes the pressurized gaseous fuel of the marine vessel, the method comprising:
storing the liquefied gaseous fuel in cryogenic conditions;
pumping the stream of liquefied gaseous fuel obtained from the stored liquefied gaseous fuel to a high pressure cryogenic pump unit (37) to produce a stream of high pressure liquefied gaseous fuel;
vaporizing the stream of high pressure liquefied gaseous fuel in a high pressure vaporizer (38) into a stream of gaseous fuel;
supplying the stream of high pressure gaseous fuel to the main engine;
A stream of boil-off gas from the stored liquefied gaseous fuel is passed through a first heat exchanger 43 to a compressor 48 which is a multi-stage compressor unit and includes a cooler 45 after each stage to produce a stream of pressurized gaseous fuel. guiding;
feeding a first portion of the pressurized gaseous fuel stream from the compressor (48) to a consumer of the pressurized gaseous fuel;
directing a second portion of the pressurized gaseous fuel stream from the compressor (48) to a reliquefaction conduit (46);
exchanging the second portion with the stream of boil-off gas in the first heat exchanger (43);
exchanging the second portion with the stream of high pressure liquefied gaseous fuel in the high pressure vaporizer (38);
Connected to the reliquefaction conduit 46 downstream of the high pressure carburetor 38 to collect the liquefied gaseous fuel produced by the cooling effect of the high pressure carburetor 38 and separate excess gaseous fuel from the reliquefied gaseous fuel directing the second portion having the stream of boil-off gas to a separation vessel (32) to be used; and
adding the separated excess gaseous fuel to the boil-off gas stream of the stored liquefied gaseous fuel; A method of supplying a stream of a gaseous fueled consumer. 7. The method of claim 6,
reliquefying at least a third portion of the second portion and adding the third portion to the stored liquefied gaseous fuel. A method of supplying a stream of pressurized gaseous fuel consumer that consumes gaseous fuel. 8. The method of claim 7,
and adding a residual gaseous portion of the second portion to the stream of boiloff gas; How to feed a stream of. 9. The method according to any one of claims 6 to 8,
a stream of pressurized gaseous fuel consumers supplying the main engine of the marine vessel with high pressure gaseous fuel and consuming the pressurized gaseous fuel of the marine vessel, comprising passing the second portion through a throttling device (29). How to supply.

Images