JP2024006957A - Large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large turbocharged two-stroke single-flow crosshead dual-fuel internal combustion engine in which a space required for fuel injection valves and cost are substantially reduced.

SOLUTION: The engine has an Otto cycle mode in which the engine is operated by first fuel such as ammonia or methane, and a fuel oil for igniting the first fuel, and a diesel cycle mode in which the engine is operated only by the fuel oil. The engine includes a fuel introduction valve (50) introducing the first fuel during an upstroke of a piston, a fuel injection valve (52) injecting the fuel oil near TDC, and a pilot ignition sub-chamber. The mixture of the first fuel and a scavenging gas in the combustion chamber is ignited by the fuel oil introduced into the sub-chamber. A fuel injector is also configured to introduce fuel oil into the pilot ignition sub-chamber during Otto cycle mode operation of the engine and to inject fuel oil into the combustion chamber during Diesel cycle mode operation of the engine.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention operates in an Otto cycle mode in which the engine is operated with a first fuel such as ammonia, methane, methanol, ethane, LPG, or DME, and fuel oil for igniting the first fuel; and in which the engine is operated in only fuel oil. The present invention relates to a large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine having a diesel cycle mode; The engine includes at least one cylinder having a cylinder liner; a piston reciprocating between bottom dead center (BDC) and top dead center (TDC); a cylinder cover defining a combustion chamber; and a cylinder cover disposed at the bottom of the cylinder. a scavenging gas inlet for introducing oxygen-containing scavenging gas into the combustion chamber at least when the piston is at bottom dead center; at least one fuel inlet valve disposed between the scavenging gas inlet and the cylinder cover or within the cylinder cover; 1 a fuel inlet valve for introducing fuel; at least one fuel injection valve disposed within the cylinder cover or within the cylinder liner; a fuel injection valve for injecting fuel; at least one pilot ignition subchamber disposed on the cylinder cover or the cylinder liner and having at least one subchamber port opening into the combustion chamber; a pilot ignition subchamber for igniting the mixture of the first fuel and the scavenging gas in the combustion chamber with the introduced fuel oil; The fuel oil is configured to be introduced into the pilot ignition subchamber during Otto cycle mode operation.

Background of the invention

An example of such a large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine is known from Japanese Patent Laid-Open No. 20037923. In this prior art document, separate fuel injectors are used to inject fuel oil in each of the Otto cycle mode and the diesel cycle mode.

Large turbocharged two-stroke uniflow crosshead internal combustion engines are used, for example, in propulsion systems for large ships and as primary prime movers in power plants. The size of this two-stroke diesel engine is huge. Not only because of its large size, but the two-stroke diesel engine also has a different structure than other internal combustion engines. For example, the weight of an exhaust valve can reach 400 kg and the diameter of the piston can reach 100 cm. The maximum pressure in the combustion chamber during operation is typically up to several hundred bar. The forces generated from such high pressure levels and piston size are enormous.

In recent years, there has been a demand for large two-stroke diesel engines to be able to handle other types of fuel, such as ammonia, ethane, LPG, and DME. Engines that can operate in both a fuel oil mode, operating on fuel oil only, and an alternative fuel mode, operating on alternative fuel and pilot fuel oil, are often referred to as dual fuel engines.

Dual fuel engines for these alternative fuels have dedicated fuel systems for these highly volatile fuels. In either case, equipment is required to completely drain the fuel from the fuel system, such as fuel piping, valves, and pumps for engine shutdown, fuel conversion to fuel oil, and maintenance.

A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine is operated in Otto cycle mode on gaseous fuel introduced through a fuel valve. The fuel valve is typically located near the longitudinal center of the cylinder liner or on the cylinder cover. The engine introduces gaseous fuel during the upward stroke of the piston from BDC to TDC, and compresses a mixture of the gaseous fuel and scavenging gas containing oxygen in the combustion chamber. It therefore operates according to a premixing process. The compressed air-fuel mixture is then ignited at or near top dead center (TDC) by ignition means (for example, injection of pilot fuel oil or pilot gas) that operates at a predetermined timing.

In a large two-stroke turbocharged internal combustion engine, when the piston injects gaseous fuel at or near top dead center (TDC), the compression pressure within the combustion chamber is approximately at its maximum. In comparison, the above type of gas introduction using a fuel valve (gas inlet valve) placed in the cylinder liner or cylinder cover injects gaseous fuel when the pressure in the combustion chamber is relatively low, resulting in a much lower fuel injection rate. It has the advantage that pressure (typically 5 to 25 bar) can be used. Types of engines that inject gaseous fuel at or near TDC require fuel injection pressures that are significantly higher (typically 300 bar or more) than the combustion chamber pressure, which is already at approximately maximum compression pressure. Due to the volatility of gaseous fuels and their behavior at high pressures, fuel systems capable of handling gaseous fuels at such extremely high pressures are expensive and complex.

Therefore, fuel supply systems for engines that inject gaseous fuel during the compression stroke are significantly less expensive than those for engines that inject gaseous fuel under high pressure when the piston is near TDC.

However, the fuel injectors for large two-stroke diesel engines are very large, and there is enough space on the engine cover to mount two to three main diesel fuel injectors and one to two subchambers, each containing a pilot fuel injector. is difficult to find. Further, fuel injection valves are expensive, and having a separate diesel fuel injection valve with a fuel supply system to the pre-chamber significantly increases costs (increases CAPEX).

It is an object of the present invention to provide a large turbocharged two-stroke uniflow crosshead dual-fuel internal combustion engine of the type mentioned at the outset, in which the above-mentioned problems regarding the space requirements and costs of the fuel injection valves are at least significantly reduced. That's true.

The above-mentioned and other objects are solved by the features of the independent claims. More specific implementation forms will become apparent from the dependent claims, the specification, and the drawings.

According to the first way of thinking, an Otto cycle mode in which the engine is operated with a first fuel such as ammonia, methane, methanol, ethane, LPG, DME, etc. and fuel oil for igniting the first fuel; A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine is provided that has a diesel cycle mode in which the engine is operated exclusively. The engine includes at least one cylinder having a cylinder liner; a piston reciprocating between bottom dead center (BDC) and top dead center (TDC); a cylinder cover defining a combustion chamber; and a cylinder cover disposed at the bottom of the cylinder. a scavenging gas inlet for introducing oxygen-containing scavenging gas into the combustion chamber at least when the piston is at bottom dead center; at least one fuel inlet valve disposed between the scavenging gas inlet and the cylinder cover or within the cylinder cover; 1 a fuel inlet valve for introducing fuel; at least one fuel injection valve disposed within the cylinder cover or within the cylinder liner; a fuel injection valve for injecting fuel; at least one pilot ignition subchamber disposed on the cylinder cover or the cylinder liner and having at least one subchamber port opening into the combustion chamber; a pilot ignition subchamber for igniting the mixture of the first fuel and the scavenging gas in the combustion chamber with the introduced fuel oil; The fuel oil is configured to introduce the fuel oil into the pilot ignition subchamber during Otto cycle mode operation, and is configured to inject the fuel oil into at least the combustion chamber during diesel cycle mode operation of the engine. It is characterized by

In a dual-fuel engine according to the invention (in which a pilot ignition subchamber is used for ignition of the fuel during Otto cycle mode operation), one and the same fuel injector is used in both operating modes of the dual-fuel engine. As a result, overall costs for the institution may be reduced. In this way, a separate pilot fuel oil injection valve and supply system can be avoided while continuing to provide good performance for engines with prechambers. Further, the cylinder cover can secure a significantly larger space for attaching other equipment such as a fuel injection valve and a monitoring device.

The at least one fuel injector may be configured to introduce fuel oil into both the pilot ignition subchamber and the combustion chamber during diesel cycle mode operation of the engine. Such an embodiment can simplify the fuel injection valve, reduce cost, and also keep the fuel oil path to the pre-chamber clean during diesel cycle mode operation of the engine.

The at least one fuel injector can in principle be designed in any suitable way, but includes at least one first nozzle hole that opens into the subchamber (e.g. through a flow path) and into the combustion chamber. Preferably, the at least one second nozzle hole is open and means for opening and closing access to the at least one first nozzle hole and the at least one second nozzle hole, respectively.

The at least one fuel injector may be of the following type. That is, a fuel valve housing having a longitudinal direction and a transverse direction and having a rear end and a front end; a nozzle having at least one bore opening into the first and second nozzle holes; a nozzle disposed at the front end of the fuel valve housing; a fuel flow path running from the rear end to the front end and connected to a source of pressurized fuel; an axially displaceable valve; a needle; a closed position in which the valve needle seats on the valve seat to prevent fuel from flowing into the nozzle; and a closed position in which the valve needle seats on the valve seat to prevent fuel from flowing into the nozzle. first and second open positions permitting flow through the at least one bore in a direction toward the first and second nozzle holes, access to the first nozzle hole; The fuel injector may be of the type that is open in said first open position and wherein access to at least said second nozzle hole is opened in said second open position.

In an embodiment of the invention, access to the first nozzle hole is also open in the second open position, allowing fuel to enter both the subchamber and the combustion chamber. I can do it.

Advantageously, said at least one fuel injection valve is a slide valve. If the at least one fuel injection valve is a slide valve, the valve needle is an elongate member projecting into a single bore of the nozzle, comprising a solid first portion and a hollow portion furthest from the valve seat. an elongated member having a second portion, the second portion having at least one orifice allowing fuel to enter the second portion, the second portion being open at a free end thereof; and

When the valve needle lifts into a first open position away from the valve seat, the free end of the elongate member lifts free to open access to the first nozzle orifice or holes. ,

When the valve needle is lifted to a second open position away from the valve seat, the free end of the elongated member is free to lift to open access to the one or more second nozzle holes. .

The elongated member of the slide valve has an element that closes access to the one or more first nozzle holes when the valve needle is lifted to the second open position away from the valve seat. You may.

The at least one pilot ignition sub-chamber disposed on the cylinder cover may have one or more sub-chamber ports, preferably two or three, that open into the combustion chamber.

The invention will now be explained in more detail with reference to exemplary embodiments shown in the drawings.
1 illustrates a frontal view of a large two-stroke dual fuel engine according to an exemplary embodiment; FIG. This figure shows an overview of the large two-stroke engine in Figure 1 as seen from the rear. 2 is a schematic representation of the large two-stroke engine of FIG. 1; 1 shows an example of a fuel injection valve that can be used in a large two-stroke dual fuel engine according to the present invention. 1 shows an insert that can be used in a large two-stroke dual-fuel engine according to the invention and includes a fuel injection valve and a prechamber; FIG.

Detailed explanation

In the detailed description that follows, the invention is described with respect to a large turbocharged two-stroke crosshead dual fuel internal combustion engine. Note, however, that in some embodiments, the internal combustion engine may be another type of engine. A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine has both an Otto cycle mode and a diesel cycle mode. In the Otto cycle mode, the engine operates on a first fuel such as ammonia, methane, methanol, ethane, LPG, DME, and fuel oil for igniting the first fuel. In a diesel cycle mode engine, the engine operates only on fuel oil.

1-3 illustrate a large, turbocharged, low speed, two-stroke dual fuel engine. This engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a large, turbocharged, low-speed, two-stroke dual-fuel engine with its intake and exhaust systems. In this example, the engine has six cylinders in series. Large, low-speed, two-stroke, turbocharged dual-fuel engines typically have four to fourteen cylinders arranged in series. These cylinders are carried by a cylinder frame 23. The cylinder frame 23 is carried by the engine frame 11. Such an engine can also be used, for example, as a main engine of a ship or as a stationary engine for operating a generator in a power plant. The total power of the engine can be, for example, from 1000 kW to 110 000 kW.

The engine of this embodiment is a two-stroke uniflow compression ignition dual fuel engine. Each cylinder liner 1 is provided with a scavenging port 18 in its lower region, and an exhaust valve is arranged in its upper center. In this illustrative example, the engine has at least one operating mode operating with a first fuel such as ammonia, methane, methanol, ethane, LPG or DME, and fuel oil for ignition of the first fuel; It has a second diesel cycle mode in which it operates only with fuel, such as fuel oil (marine diesel oil) or heavy oil.

Scavenging air is guided through the scavenging air receiver 2 to the scavenging air port 18 of each cylinder 1. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1 and compresses scavenging air. In the illustrated embodiment, in the Otto cycle mode, fuel, for example in the form of ammonia, is injected into the combustion chamber 53 in the cylinder liner 1 through a low-pressure fuel valve 50 arranged in the cylinder cover 22 . In an alternative embodiment, fuel for the Otto cycle mode may be introduced through a low pressure fuel valve 50' located in the cylinder liner 1 somewhere intermediate between the scavenge port 18 and the cylinder cover 22. In the dual fuel engine according to the present invention, ignition at a predetermined timing at or near TDC is caused by injection of ignition fluid into the auxiliary chamber 51 disposed in the cylinder cover 22. This auxiliary chamber 51 opens into a combustion chamber 53, as will be explained in more detail later. Combustion occurs and exhaust gas is produced. In the illustrated embodiment, each cylinder cover 22 includes only one fuel valve 50, but may include two or more fuel valves 50. In the illustrated embodiment, fuel valve 50 may be configured to inject only one particular type of fuel (eg, ammonia). In that case, one or more fuel valves 52 would also be provided for injecting conventional fuel into the combustion chamber 53. Therefore, an engine may have two or more fuel valves. In the illustrated embodiment, the fuel valves 50 and 52 are both arranged in the cylinder cover 22 and are arranged around the exhaust valve 4, which is arranged in the center of the cylinder cover 22. In the engine according to the present invention, ignition fuel is injected into the auxiliary chamber 51 by the fuel injection valve 52 .

When the exhaust valve 4 opens, the exhaust gas flows through the exhaust duct provided in the cylinder 1 to the exhaust receiver 3, passes through the selective catalytic reduction reactor (SCR reactor) 28, and then passes through the first exhaust pipe 19 to the turbo. Proceed to the turbine 6 of the supercharger 5. From there, the exhaust flows through the second exhaust pipe 25 to the economizer 20 and is further discharged to the atmosphere through the outlet 21. SCR reactors reduce NOx emissions. In some embodiments, not shown, the engine may not have an SCR reactor 28. The engine may be equipped with an exhaust gas recirculation (EGR) system that recirculates a portion of the exhaust gas from the exhaust pipe 19 to the scavenge pipe 13.

Turbine 6 drives compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12 . The compressor 7 sends compressed scavenging air to the scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air from the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging air flow if the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging air receiver 2, ie when the engine is at low or part load. When the engine load is high, the turbocharger compressor 7 can supply sufficiently compressed scavenging air, so that the auxiliary blower 16 is bypassed by the check valve 15 and the electric motor 17 is stopped. .

The engine operates in the Otto cycle mode using the alternative fuel (first fuel) as the main fuel. This alternative first fuel is, for example, ammonia, methane, methanol, ethane, LPG or DME. The alternative first fuel is supplied to the first fuel valve 50 at a substantially constant pressure and temperature.

Since conventional fuel systems are well known, they are not shown or described in detail. First fuel system 30 supplies a first fuel to fuel valve 50 .

According to the present invention, the fuel injector 52 is configured to introduce fuel oil into the pilot ignition subchamber 51 during Otto cycle mode operation of the engine, and at least into the combustion chamber 51 during engine diesel cycle mode operation. 53 is configured to inject fuel oil.

An example of a fuel injection valve is depicted in FIG. The fuel injection valve 52 is configured to introduce fuel oil into the pilot ignition subchamber 51 during the Otto cycle mode operation of the engine, and is configured to inject fuel oil into at least the combustion chamber 53 during the engine diesel cycle mode operation. is configured to do so. The fuel injection valve includes a first nozzle hole 31 (see FIG. 5) that opens into the auxiliary chamber 51 (through the flow path 56, for example), a second nozzle hole 33 that opens into the combustion chamber 53, and a first nozzle hole. 31 and means for opening and closing access to the second nozzle hole 33, respectively. This opening and closing means is in the form of an elongated member 34.

The fuel injection valve 52 includes a fuel valve housing 35 having a rear end 36 and a front end 37 having longitudinal and lateral directions, and a nozzle having one bore 39 that opens into the first nozzle hole 31 and the second nozzle hole 33. 38. A nozzle 38 is located at the front end 37 of the housing 35. Fuel flow path 40 extends from rear end 36 toward front end 37 and is connected to a source of pressurized fuel. The fuel injection valve 52 includes a valve needle 41 that is axially displaceable. The valve needle 41 is positioned in a closed position, seated on the valve seat 42 to prevent fuel from flowing into the nozzle 38, and in a closed position, in which the valve needle 41 is seated off the valve seat 42, allowing fuel to pass through the bore 39 of the nozzle 38. It has at least a first open position and a second open position that allow flow in a direction toward the first nozzle hole 31 and the second nozzle hole 33. In said first open position access to the first nozzle hole 31 is opened. In said second open position, access to both the first nozzle hole 31 and the second nozzle hole 33 is opened.

The fuel injection valve 52 shown in FIG. 4 is a slide valve, the feature of which is that the valve needle 41 has a special design. The valve needle 41 of the slide valve has an elongated member 34 projecting into a single bore 39 . This member has a solid first part 43 and a hollow second part 44 which is the part furthest from the valve seat 42. This hollow part has at least one orifice 45 and is open at its free end 46. In operation, when the valve needle 41 is disposed away from the valve seat 42 to its open position, the free end 46 of the elongated member 34 is also lifted free from the nozzle bore 41 and the fuel flows between the elongated member 34 and the wall of the bore 39. The fluid flows between the bore 39 to one or more orifices 45 and then into the hollow portion 44 . From there, the fuel flows out to the open free end 46 and flows into the first nozzle hole 31 in the first open position of the valve needle 41 and between the first nozzle hole 31 and the second nozzle hole in the second open position. It flows into both the nozzle hole 33 and the nozzle hole 33. An axially displaceable valve needle 41 is slidably received within a longitudinal bore 47 in the valve housing 35 with tight clearance. The nozzle holes 31 and 33 are arranged near the tip 48 of the nozzle 38 in the axial direction. In the illustrated embodiment, this tip 48 is closed. Nozzle 38 is shown positioned relative to housing 35 by locating pin 49 .

FIG. 5 shows an insert 55 including a fuel injection valve 52 and an auxiliary chamber 51 as shown in FIG. This insert can be used in the large two-stroke dual-fuel engine according to the present invention by being installed at the time of new construction or by being retrofitted. Insert 55 is attached to cylinder cover 22. The insert 55 also includes a first flow path 56 that connects the first nozzle hole 31 of the fuel injection valve 52 and the auxiliary chamber 51, and a second flow path 57 that connects the second nozzle hole 33 and the combustion chamber 53. have In FIG. 5, the valve needle 41, and thus the elongate member 34, is in its closed position, preventing fuel from flowing into either nozzle hole. When the valve needle 41 is lifted to the first open position, fuel is allowed to enter the subchamber 51 through the first flow path 56, and when the valve needle 41 is further lifted to the second open position, the fuel is allowed to enter the secondary chamber 51 through the first flow path 56. It is also possible to enter the combustion chamber through the flow path 57.

Claims (8)

an Otto cycle mode in which the engine is operated using a first fuel such as ammonia, methane, methanol, ethane, LPG, or DME, and fuel oil for igniting the first fuel;
Diesel cycle mode that operates the engine only with fuel oil;
A large turbocharged two-stroke uniflow crosshead dual fuel internal combustion engine having:
at least one cylinder having a cylinder liner;
a piston that reciprocates between bottom dead center (BDC) and top dead center (TDC); a cylinder cover that defines a combustion chamber;
a scavenging gas inlet located at the bottom of the cylinder for introducing scavenging gas containing oxygen into the combustion chamber at least when the piston is at bottom dead center;
at least one fuel inlet valve associated with the cylinder and located within the cylinder liner between the scavenging gas inlet and the cylinder cover, the valve comprising: a fuel introduction valve for introducing the first fuel during a BDC to TDC stroke;
at least one fuel injection valve disposed within the cylinder cover or within the cylinder liner for injecting the fuel oil when the piston is at or near TDC;
at least one pilot ignition subchamber disposed on the cylinder cover or the cylinder liner and having at least one subchamber port opening into the combustion chamber, the fuel oil introduced into the subchamber; a pilot ignition subchamber for igniting the mixture of the first fuel and the scavenging gas in the combustion chamber;
wherein the at least one fuel injector is configured to introduce the fuel oil into the pilot ignition subchamber during Otto cycle mode operation of the engine, and during diesel cycle mode operation of the engine; An engine configured to inject the fuel oil into at least the combustion chamber. The engine of claim 1, wherein the at least one fuel injector is configured to introduce fuel oil into both the pilot ignition subchamber and the combustion chamber during diesel cycle mode operation of the engine. . The at least one fuel injection valve includes, for example, at least one first nozzle hole that opens into the subchamber through a flow path, at least one second nozzle hole that opens into the combustion chamber, and the at least one first nozzle hole that opens into the combustion chamber. 2. An engine according to claim 1, comprising means for respectively opening and closing access to the nozzle hole and the at least one second nozzle hole. The at least one fuel injector comprises:
a fuel valve housing having a longitudinal direction and a transverse direction, and having a rear end and a front end;
a nozzle having at least one bore opening into the first nozzle hole and the second nozzle hole, the nozzle being disposed at the front end of the fuel valve housing;
a fuel flow path running from the rear end to the front end and connected to a source of pressurized fuel;
an axially displaceable valve needle;
Equipped with
The valve needle is
a closed position sitting on the valve seat to prevent fuel from flowing to the nozzle;
a first open position, unseated from the valve seat, allowing fuel to flow through the at least one bore of the nozzle in a direction toward the first and second nozzle holes; and a second open position.
access to the first nozzle hole is opened in the first open position, and access to at least the second nozzle hole is opened in the second open position;
The institution according to claim 3. 5. The engine of claim 4, wherein access to the first nozzle hole is also open in the second open position, allowing fuel to enter both the subchamber and the combustion chamber. . 6. An engine according to claim 4 or 5, wherein the at least one fuel injection valve is a slide valve and the valve needle has an elongated member projecting into a single bore of the nozzle. The elongate member has a solid first portion and a hollow second portion furthest from the valve seat, the second portion having at least one inlet for allowing fuel to enter the second portion. an orifice, the second portion being open at its free end;
when the valve needle lifts to a first open position away from the valve seat, the free end of the elongate member lifts free to open access to the one or more first nozzle holes;
when the valve needle lifts to a second open position away from the valve seat, the free end of the elongated member is free to lift to open access to the one or more second nozzle holes;
The institution according to claim 6. the elongated member of the slide valve has an element that closes access to the one or more first nozzle holes when the valve needle is lifted to the second open position away from the valve seat; The institution according to claim 6.