JP7307293B1 - Large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine and method of operation thereof - Google Patents

Abstract

A large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one mode of operation operating with both ammonia and an ignition fluid such as fuel oil.
At least one cylinder having a cylinder liner, a reciprocating piston in the cylinder liner, and a cylinder cover covering the cylinder, a combustion chamber formed in the cylinder between the reciprocating piston and the cylinder cover; An ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed on a cylinder cover or cylinder liner, and at least one ignition fluid valve disposed on the cylinder cover or cylinder liner. and an ignition fluid system configured to supply pressurized ignition fluid, wherein the ignition fluid system burns the ignition fluid for an injection duration of at least 20% of the determined ammonia fuel combustion duration. Configured to supply indoors.
[Selection drawing] Fig. 3

Description

The present invention relates to a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one mode of operation operating with both ammonia and an ignition liquid (e.g. fuel oil) as the fuel to be combusted within the engine. . at least one cylinder having a cylinder liner and a reciprocating piston within said cylinder liner; a cylinder cover covering said cylinder; and a combustion formed within said cylinder between said reciprocating piston and said cylinder cover. an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in said cylinder cover or said cylinder liner; disposed in said cylinder cover or said cylinder liner; an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve in the .

Background of the Invention

Large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engines are typically used as prime movers for large ocean-going ships such as container ships and power plants. Engines of this type are very often run on heavy or fuel oil. Its size, weight and power set large two-stroke turbocharged compression ignition internal combustion engines far apart from other combustion engines and place this type of compression internal combustion engine in a unique class.

Internal combustion engines have traditionally been driven primarily by hydrocarbon fuels, such as fuel oil, such as diesel oil, or fuel gas, such as natural gas or petroleum gas. Combustion of hydrocarbon fuels is associated with the production of greenhouse gases such as carbon dioxide (CO2), which can contribute to air pollution and climate change. Unlike petroleum fuel impurities that produce by-product emissions, CO2 production is inevitable in hydrocarbon combustion. A fuel's energy density and CO2 footprint depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. As such, gaseous hydrocarbon fuels have lower CO2 emissions than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult to handle, store, and costly. Research into fuels other than hydrocarbons is underway to reduce CO2 emissions.

Ammonia is a product obtained from petroleum, biomass and renewable energy sources (wind, solar, hydro, geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when burned and emits no CO2, SOx, particulate matter or unburned hydrocarbons. Ammonia is currently of great interest as a fuel for internal combustion engines. This is primarily because it can be produced in a climate-friendly manner using electricity from renewable sources such as solar, wind and wave energy, and because the combustion of ammonia itself does not contain greenhouse gases such as carbon dioxide. is.

WO 2020/252518 A1 describes a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine of the type mentioned at the outset.

When using ammonia as fuel for an internal combustion engine, when operating on the Otto principle in which ammonia fuel is introduced at a relatively low pressure during the compression stroke of the piston, and when the piston approaches top dead center (TDC), ammonia fuel is introduced. It may operate on the diesel principle with injection into the combustion chamber at high pressure. During the ammonia fuel injection/combustion phase of the piston cycle, cylinder pressure changes dramatically due to combustion chamber compression/expansion and combustion.

Ammonia has been tested and used on a small scale in small spark ignited internal combustion engines. However, they have not yet been used on a large scale in compression ignition internal combustion engines.

There are some technical problems in using ammonia as a fuel. One challenge is the low power density compared to typical hydrocarbon fuels. This leads to a very large amount of fuel having to be injected and thus to a large flow rate. Such large flow rates can result in flame extinction. That is, even if ignition occurs very early in the injection event, the subsequent high flow rate and accompanying high velocity fuel jet will extinguish (blow out) the flame. Another problem is that ammonia is less ignitable (easier to burn) than liquid hydrocarbon fuels. A further problem is the large evaporative cooling of ammonia, which cools the fuel during injection. Therefore, a lot of ignition energy is required. Due to strong evaporative cooling, a high temperature in the fuel chamber is a prerequisite for stable combustion. These technical challenges have strongly hindered the use of ammonia as the main fuel in compression ignition engines.

Internal combustion engines that can operate on two fuels are commonly referred to as dual fuel engines. The two different fuels in a dual fuel engine usually consist of a compression ignitable fuel oil, such as heavy oil or diesel, and a gaseous fuel, such as ammonia, methanol, LPG, LNG, ethane, all of which, for example, pilot It is necessary to add ignition fluid in the form of fuel oil. Therefore, the concept of existing technical solutions for dual-fuel engines operating on ammonia and fuel oil is based on the idea that the engine either operates on fuel oil alone at its maximum rating or uses a minimum of pilot fuel oil for ignition of the ammonia fuel. , but operated at maximum rating on ammonia fuel only. Existing concepts include a fuel oil injection system optimized for full-rate delivery of fuel oil, an ammonia fuel system optimized for full-rate operation with ammonia, and a pilot fuel oil injection into the vestibule (e.g. A pilot fuel oil system suitable for ammonia ignition with a minimum of pilot fuel oil is needed. Also, some known dual fuel engines use a full rate fuel injection system for pilot fuel injection as well. Here, the amount of pilot fuel oil is in the range of 1.5-5% of the full rate amount when operating on gas fuel.

However, existing ammonia and fuel oil dual fuel engines suffer from the complexity of having a fuel oil pilot injection system. Also, the dual fuel concept does not operate the fuel oil injection system at full rate during ammonia fuel operation. For this reason, deposits may form in the nozzle holes of the injection valves of the full-rate fuel oil injection system when the vehicle is running on ammonia fuel, and the full-rate fuel oil injection system may not operate normally when the ammonia operation is switched to the fuel oil operation. Furthermore, since the laminar flame speed of ammonia is approximately one-tenth that of many hydrocarbons, flame extinguishing/extinguishing can occur even at low turbulence levels. For this reason, it is difficult to sustain ammonia combustion using the full-rate fuel oil injection systems utilized in known heavy oil/gas dual fuel engines, and it is difficult to ensure that all of the ammonia fuel introduced into the combustion chamber. It is difficult to ignite and burn. The injection time of the fuel oil in the pilot fuel oil injection system is typically about 1 degree crank angle, which only ensures ignition of the ammonia, but cannot guarantee complete combustion of all the ammonia fuel. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine of the initially mentioned type, in which the above problems are at least greatly reduced.

The above-mentioned and other problems are solved by the features of the independent claims. More specific implementations will become apparent from the dependent claims, the description and the drawings.

According to the first conception, a large turbocharged two-stroke uniflow crosshead that has at least one operating mode that operates using both ammonia and an ignition liquid such as fuel oil as fuels to be burned in the engine. A compression ignition internal combustion engine is provided. This institution
- at least one cylinder having a cylinder liner and a reciprocating piston within said cylinder liner; and a cylinder cover covering said cylinder;
a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
wherein the ignition fluid system is configured to deliver ignition fluid into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration.

The combustion time of the ammonia fuel is determined by the engine control system according to the actual rpm of the engine.

A more complete combustion of the ammonia is achieved by injecting the ignition liquid into the combustion chamber of the cylinder of the internal combustion engine for a longer period of time than in known practice. In addition, because a full rate fuel injector can be used, a pilot fuel injection system can be omitted, thus providing significant cost savings and better space to install fuel injectors in the cylinder cover. be done. In addition, since the fuel oil injection device is kept in operation even during the dual fuel operation of ammonia and ignition liquid (fuel oil, etc.), the fuel oil injection device can be maintained in a clean state, and the ammonia dual fuel operation is possible. Provision can be made for switching from to fuel oil operation.

In order to obtain a higher combustion rate of ammonia, preferably a complete combustion rate, said igniter fluid system controls at least 50%, preferably at least 80%, most preferably at least 95% of said determined ammonia fuel combustion duration. may be configured to supply ignition liquid into the combustion chamber for an injection duration of .

The ignition fluid system may be configured to deliver ignition fluid into the combustion chamber at injection durations that increase from 2 crank angle degrees at low engine speed to 20 crank angle degrees at full engine speed. Low engine speed is defined herein as the lowest possible engine speed.

In some embodiments, the ignition fluid system may be configured to continuously supply ignition fluid into the combustion chamber during the injection duration, or to intermittently supply ignition fluid into the combustion chamber. may be configured. If the ignition fluid system is configured to inject intermittently, the number of injections may be pre-determined between 2 and 10, preferably 5; may be variably determined by a control system that monitors a number of different engine operating parameters, such as cylinder pressure, which is indicative of .

The ignition fluid system ignites with an amount in the range of 5-50%, preferably 15-40%, most preferably 25-35% of the amount required for full speed operation when operating solely on ignition fluid such as fuel oil. It may be configured to supply liquid into the combustion chamber.

The ammonia fuel system may be arranged to supply ammonia to the combustion chamber in an amount of at least 60%, preferably at least 70%, most preferably at least 95% of the amount of fuel required for full speed operation of the engine. Costs are reduced as the size of the ammonia fuel system is reduced.

In some embodiments, the ammonia fuel valve may be connected to a pre-chamber that is connected to the combustion chamber by an opening. Injecting ammonia fuel into the combustion chamber through such a prechamber causes a significant deceleration of the fuel before it enters the combustion chamber through the opening, and the prechamber can also serve as a preheating chamber. . As a result, the fuel velocity decreases as it enters the combustion chamber through the opening, and the fuel temperature increases as it enters the combustion chamber. Thereby, the above-mentioned problems associated with using ammonia as a fuel in compression ignition internal combustion engines are at least partially resolved.

In such an embodiment of the invention, the engine has an ignition fluid valve associated with the prechamber, said ignition fluid valve having an ignition fluid nozzle having a nozzle hole, said ignition fluid valve being pressurized. may be combined with a source of ignition fluid. As a result, the ignition fluid is mixed with the ammonia in the prechamber, improving the reliability of ignition of the ammonia. Injecting the ignition fluid at high pressure into the pre-chamber ensures that the ignition fluid is well dispersed in the ammonia and that the mixture of ignition fluid and ammonia is already well mixed when it enters the combustion chamber. be done.

The prechamber may have the form of an insert in the cylinder cover. Therefore, if damage occurs to the pre-chamber or the opening between the pre-chamber and the combustion chamber, the pre-chamber can be easily replaced by simply replacing the insert, which allows the entire cylinder cover to be repaired and machined. no need to do

The prechamber may also form a single unit with the ammonia fuel valve. This single unit is an insert placed in the cylinder cover. Thus, the prechamber and ammonia fuel valve can be attached to the cylinder cover in a single operation.

According to the second conception, a large turbocharged two-stroke uniflow crosshead that has at least one operating mode that operates using both ammonia and an ignition liquid such as fuel oil as the fuel to be burned in the engine. A method of operating a compression ignition internal combustion engine is provided. wherein said agency:
- at least one cylinder having a cylinder liner and a reciprocating piston in said cylinder liner; and a cylinder covering said cylinder;
a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
and the method is characterized in that the ignition fluid is supplied into the combustion chamber for an injection duration of at least 20% of the determined ammonia-fueled combustion duration.

The invention will be explained in more detail below with reference to exemplary embodiments shown in the drawings.
1 shows a frontal view of a large two-stroke diesel engine in accordance with certain exemplary embodiments; 2 shows an overview of the large two-stroke engine of FIG. 1 viewed from the rear. 2 shows a schematic representation of the large two-stroke engine of FIG. 1;

Detailed explanation

In the following detailed description, the compression ignition internal combustion engine according to the invention will be described with reference to a large two-stroke crosshead uniflow scavenging internal combustion engine. However, it should be understood that the internal combustion engine may be of other types.

1-3 depict a turbocharged large low speed two-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9 . FIG. 3 is a schematic representation of a turbocharged large low-speed two-stroke diesel engine with its intake and exhaust systems. In this embodiment the engine has six cylinders 1 in series. Turbocharged large low speed two-stroke diesel engines typically have from 4 to 14 cylinders arranged in series. These cylinders are carried on 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 on ships or as a stationary engine for powering generators in power plants. The total engine power can be, for example, from 1000 kW to 110000 kW.

The engine in this embodiment is a two stroke uniflow compression ignition binary engine. Each cylinder liner 1 is provided with a scavenging port 18 in its lower region and an exhaust valve arranged centrally on its top. The engine has at least one mode of operation operating both on ammonia or ammonia-based fuels and on ignition liquids such as fuel oil. The engine may also have at least one conventional fuel mode operating on conventional fuels, such as fuel oil marine diesel) or heavy oil.

During operation of the engine, scavenging air is directed through the scavenging receiver 2 to the scavenging ports 18 of each cylinder 1 . Piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in cylinder liner 1 to compress scavenging air. Fuel is injected into the combustion chamber inside the cylinder liner 1 through a fuel valve 50 arranged on the cylinder cover 22 . The injected fuel contains ammonia and ignition fluid. Ammonia is supplied from the ammonia fuel supply device 30, and ignition liquid is supplied from the ignition fuel supply device 40, respectively. The injection of ammonia may occur at relatively low pressure during the stroke of piston 10 toward TDC, or at high pressure at or near TDC. The ignition fluid injection is always at or near TDC and at high pressure. Following the injection of fuel, combustion occurs and exhaust is produced.

Each cylinder cover 22 is provided with two or more fuel valves 50 . The fuel valves 50 may each be configured to inject only one particular type of fuel, ammonia and in this case ignition liquid. In such a case, two or more fuel valves 50 are provided for injecting ammonia into the combustion chamber and two or more fuel valves 50 for injecting ignition liquid, for example in the form of conventional fuel, into the combustion chamber. become. Accordingly, in such a case, the engine would have four or more fuel valves 50. FIG. When the fuel valve 50 is configured to simultaneously inject both ammonia and conventional fuel (for example, ammonia and conventional fuel are premixed and injected, or ammonia and conventional fuel are separately injected). nozzle holes), the number of fuel valves 50 provided in each cylinder may be two or more. The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4 arranged in the central portion of the cylinder cover 22 .

The ignition liquid may be, for example, dimethyl ether (DME) or fuel oil. However, other forms of ignition accelerator, such as hydrogen, are also possible. Since the engine is a dual fuel engine, it can also be operated in a conventional fuel mode where it is operated solely on conventional fuels such as ignition liquid, e.g. fuel oil (marine diesel), or heavy oil.

In some embodiments, an ammonia fuel inlet valve is positioned along the cylinder liner. The ammonia fuel inlet valve introduces ammonia fuel into the cylinder liner at relatively low pressure before the piston 10 passes through the ammonia fuel inlet valve on its way from BDC to TDC. The piston 10 then compresses the mixture of scavenging air and fuel. Ignition is performed at a predetermined timing at or near TDC. This ignition is performed by injection of ignition fluid or the like. In the embodiment with the ammonia fuel inlet valve, the pressure at which the ammonia fuel is introduced is significantly lower than the pressure at which the fuel is injected in the embodiment with the fuel valve 50 in the cylinder cover 22 . As such, the pressure required for the fuel delivery system 30 to deliver the ammonia fuel may be significantly lower and/or the pressure booster often used in the fuel valve 50 located in the cylinder cover 22 may not be required.

When the exhaust valve 4 opens, the exhaust flows through an exhaust duct provided in the cylinder 1 to the exhaust receiver 3, further through a selective catalytic reduction reactor (SCR reactor) 38, through a first exhaust pipe 19, and into the turbo. Proceed to turbine 6 of supercharger 5 . From there, the exhaust flows through a second exhaust pipe 25 to the economizer 20 and out the outlet 21 to the atmosphere. SCR reactors reduce emissions in the exhaust, especially NOx emissions.

Turbine 6 drives compressor 7 via a shaft. Outside air is supplied to the compressor 9 through an air intake 12 . The compressor 7 sends the compressed scavenging air to the scavenging pipe 13 connected to the scavenging receiver 2 . The scavenging air in 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 when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging receiver 2, ie when the engine is under 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 non-return valve 15 and the electric motor 17 is stopped. .

Ammonia is supplied to ammonia valve 50 at a substantially stable pressure and temperature. It may be supplied to the ammonia valve 50 in a liquid phase, or may be supplied to the ammonia valve 50 in a gas phase. The liquid phase ammonia may be aqueous ammonia, ie an aqueous solution of ammonia.

According to the invention, the ignition fluid is injected into the combustion chamber of the cylinder of the internal combustion engine for a longer period of time than in known practice, thereby achieving a more complete combustion of the ammonia. According to known practice, the ignition fluid is injected over a crank angle of approximately 1 degree. This corresponds to 5-10% of the combustion duration of ammonia fuel. In contrast, in accordance with the present invention, the ignition fluid system 40 is configured to deliver ignition fluid into the combustion chamber for an injection duration of at least 20% of the determined ammonia fuel combustion duration.

In addition to burning the ammonia more completely, an additional advantage of the present invention is that a full rate fuel oil injection system can be used to inject the ignition fluid. This is because of the required amount of ignition fluid to be used. This means that the pilot fuel oil injection system can be omitted, thus providing significant cost savings and better space for installing the fuel injectors in the cylinder cover. Also, in all operating modes of the engine, the fuel oil injection device continues to operate, so a clean state can be maintained.

From the viewpoint of generating as little CO2 as possible even when the engine is operated to simultaneously burn ammonia and ignition liquid, the amount of ignition liquid must be as small as possible within a range that does not impair the combustion of ammonia. However, in some situations, the ignition liquid must be injected into the combustion chamber for at least 50%, alternatively at least 80%, alternatively at least 95% of the combustion time of the ammonia fuel in order to completely combust the ammonia. It is also possible for the ignition fluid to be injected into the combustion chamber for an injection time that is 100% of the ammonia fuel combustion time.

The injection duration during which the ignition fluid system 40 delivers the ignition fluid into the combustion chamber may be increased from about 2 crank angle degrees at low engine speed to about 20 crank angle degrees at full engine speed.

Depending on the embodiment, the ignition fluid system may be configured to continuously supply ignition fluid into the combustion chamber for the injection duration, or may be configured to intermittently supply ignition fluid into the combustion chamber. may If the ignition fluid system is configured to inject intermittently, the number of injections may be pre-determined from 2 to 10, preferably 5, or otherwise improve the combustion performance and thus the combustion of ammonia. It may be variably determined by a control system that monitors a number of different engine operating parameters, such as indicated cylinder pressure.

The ignition fluid system should be in the range of 5-50%, preferably 15-40%, most preferably 25-35% of the amount required for maximum rpm (maximum speed) when operating solely on ignition fluid such as fuel oil. may be configured to supply the ignition liquid into the combustion chamber in an amount of

The ammonia fuel system may be configured to supply ammonia to the combustion chamber in an amount of at least 60%, preferably at least 70%, and most preferably at least 95%. Reducing the size of the ammonia fuel system reduces costs accordingly.

Claims (10)

A large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one mode of operation operating with both ammonia and an ignition fluid such as fuel oil as fuel to be combusted in the engine, said institutions are
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
with
An engine, wherein the ignition fluid system is configured to supply ignition fluid into the combustion chamber for an injection duration of at least 20% of an ammonia fuel combustion duration determined as a function of engine speed . The ignition fluid system is configured to supply ignition fluid into the combustion chamber for an injection duration of at least 50%, preferably at least 80%, most preferably at least 95% of the determined ammonia fuel combustion duration. 2. An engine according to claim 1, characterized in that: 2. The igniter fluid system of claim 1, wherein the igniter fluid system is configured to deliver igniter fluid into the combustion chamber with an injection duration corresponding to anywhere from 2 degrees to 20 degrees of crank angle. institutions. 4. An engine as claimed in any preceding claim, wherein the ignition fluid system is configured to continuously supply ignition fluid into the combustion chamber for the duration of injection. 4. An engine as claimed in any preceding claim, wherein the ignition fluid system is configured to intermittently supply ignition fluid into the combustion chamber during the injection duration. If the igniter system is configured to inject intermittently, the number of injections is pre-determined between 2 and 10, preferably 5, or indicates combustion performance and thus combustion of ammonia. 6. An engine as claimed in claim 5, variably determined by a control system which monitors a plurality of different engine operating parameters such as cylinder pressure. Said igniter fluid system has an amount in the range of 5 to 50%, preferably 15 to 40%, most preferably 25 to 35% of the amount required for maximum rpm when operating only on igniter fluid such as fuel oil. 4. An engine as claimed in any preceding claim, arranged to supply ignition liquid into the combustion chamber. said ammonia fuel system is arranged to supply ammonia to said combustion chamber in an amount of at least 60%, preferably at least 70%, most preferably at least 95% of the amount of fuel required for full speed operation of the engine; An engine according to any one of claims 1 to 3, characterized in that A method of operating a large turbocharged two-stroke uniflow crosshead compression ignition internal combustion engine having at least one mode of operation operating with both ammonia and an ignition liquid such as fuel oil as the fuel to be combusted in the engine. and said agency:
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to at least one ammonia fuel valve disposed in the cylinder cover or the cylinder liner;
an ignition fluid system configured to supply pressurized ignition fluid to at least one ignition fluid valve disposed in the cylinder cover or the cylinder liner;
wherein said ignition liquid is supplied into said combustion chamber for an injection duration of at least 20% of an ammonia fuel combustion duration determined as a function of engine speed . Claim characterized in that said ignition liquid is supplied into said combustion chamber for an injection duration of at least 50%, preferably at least 80%, most preferably at least 95% of said determined ammonia fuel combustion duration. Item 9. The method of Item 9.

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