Patent Description:
Internal combustion piston engine is widely utilized in providing mechanical power in land-based power plant and in marine vessel for producing electric power and/or propulsion power.

A dual-fuel engine uses a low-pressure gaseous fuel such as natural gas that is mixed at relatively low pressure with intake air admitted into the engine cylinders. The air/gaseous fuel mixture that is provided to the cylinder under certain operating conditions is compressed and then ignited using a spark ignition or using a compression ignition pilot fuel, such as light fuel oil, which is injected into the air/gaseous fuel mixture present in the cylinder.

A direct injection gas engine is also known as such, in which a gaseous fuel, such as liquefied natural gas (LNG), is injected into the cylinder at high-pressure while combustion in the cylinder from a diesel pilot is already underway. The direct injection gas engines operate on the gaseous fuel, and the diesel pilot provides ignition of the gaseous fuel.

<CIT> discloses a fuel supply system for supplying high-pressure gas to a large two-stroke compression-ignited internal combustion engine. The engine is provided with a fuel injection system for injecting the supplied high-pressure gas into the combustion chambers of the engine. The fuel supply system comprises a feed conduit connecting an outlet of a liquefied gas storage tank to the inlet of a high-pressure pump for transporting liquefied gas from the liquefied gas storage tank to the high-pressure pump, a transfer conduit connecting the outlet of the high-pressure pump to the inlet of a high-pressure vaporizer for transporting high-pressure liquefied gas from the high-pressure pump to the high-pressure vaporizer, a supply conduit connecting the outlet of the high-pressure vaporizer to an inlet of the fuel injection system of the engine for transporting high-pressure vaporized gas to the fuel injection system of the engine. The high-pressure pump comprises two or more pump units. Each pump unit comprises a pump piston slidably disposed in a pump cylinder and a hydraulically powered drive piston slidably disposed in a drive cylinder with the drive piston coupled to the pump piston for driving the pump piston.

<CIT> discloses an engine fuel system having liquid and gaseous fuel systems, each of which injects fuel directly into an engine cylinder. The gaseous fuel system is a direct injection gas system which comprises a liquefied gas storage, liquefied gas pump, liquefied gas evaporator and gaseous gas fuel rail connected to a fuel injector.

A gaseous fuel direct injection fuel supply system needs to be configured such that gas at substantially high-pressure is delivered to the gas injectors arranged to the cylinders of the engine.

Both of the above mentioned prior art documents suggest to control the operation of the gaseous fuel pump by control fluid which operates the high-pressure piston pump. Variable control of the high-pressure pump requires a variable high-pressure pump of the control fluid system. The prior art solutions have a general problem of complexity in structure of liquefied gas pump and its controllability.

Other systems are known for example from <CIT> and <CIT>.

An object of the invention is to provide an assembly for direct injection of gaseous fuel in a cylinder of a two-stroke internal combustion piston engine which is considerably improved compared to the prior art solutions.

An object of the invention is to provide two-stoke internal combustion piston engine having a direct injection gaseous fuel feeding system which is considerably improved compared to the prior art solutions for gas operated large two-stroke internal combustion piston engines.

Objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

The assembly is therefore configured to pump the liquefied gas in liquid phase, cryogenic conditions, and evaporate the pumped gas into gaseous form, which may be administered to the cylinder by the gaseous gas fuel injector. The fuel injection system utilizing liquefied gas is provided for a large two-stroke engine which can be easily modularized. Safety issues relating to gaseous fuel are taken care of by the enclosure which is common for the liquefied gas supply manifold and the liquefied gas return manifold, a liquefied gas high-pressure pump unit. The assembly can be readily installed to an existing large two-stroke engine, because it is configured to be assembled on top of the engine.

According to an embodiment of the invention the enclosure is provided with an air inlet and an outlet connectable to a blower arranged to the assembly. This makes it possible to connect the outlet to a blower for conveying possibly leaked fuel safely away from the engine.

According to an embodiment of the invention the liquefied gas supply manifold in the enclosure is a single wall manifold and the liquefied gas return manifold in the enclosure is a single wall manifold.

According to the invention the fuel feed line outside the enclosure is provided with a separate double wall which forms an intermediate space inside the double wall and that the enclosure is provided with a lead-through block via which the fuel feed line is led from the enclosure to the heat exchanger unit, which lead-through block separates the intermediate space of the fuel feed line from the space of the enclosure.

According to an embodiment of the invention the assembly comprises a gaseous gas accumulator connected to the gaseous gas outlet of the heat exchanger unit by means of the fuel feed line.

According to the invention the assembly comprises an enclosure and the assembly is configured for a multi-cylinder two-stroke internal combustion piston engine comprising a several cylinders arranged in a line of cylinders, wherein.

According to an embodiment of the invention the assembly is configured for a multi-cylinder two-stroke internal combustion piston engine comprising a several cylinders arranged in a line of cylinders, and.

According to an embodiment of the invention the liquefied gas supply manifold is an assembly of multiple gas supply manifold sections, comprising one supply manifold section for each cylinder of the engine.

According to an embodiment of the invention the liquefied gas return manifold is an assembly of multiple gas return manifold sections, comprising one return manifold section for each cylinder of the engine.

According to an embodiment of the invention the assembly comprises several fuel delivery lines for the cylinders of the engine, each fuel delivery line comprising.

A two-stroke internal combustion piston engine according to the invention comprises more than one cylinders in which each cylinder is provided with an assembly according to anyone of the claims <NUM> and <NUM>.

According to an embodiment of the invention the enclosure has a length extending from a first cylinder in the line of cylinders to the last cylinder in the line of cylinders of the engine.

According to an embodiment of the invention the enclosure, the liquefied gas supply manifold, the liquefied gas return manifold and the liquefied high-pressure pump units are arranged on and attached to the top of engine.

According to an embodiment of the invention that the engine comprises one fuel delivery line for each cylinders (<NUM>) of the engine.

The assembly according to the invention and its various embodiments are applicable for use liquefied combustible gas for direct injection of gaseous fuel into a cylinder of an internal combustion piston engine, and combustion therein. For example, liquefied ammonia, liquefied natural gas or liquefied petroleum gas as suitable fuel materials.

The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

<FIG> depicts schematically a simplified assembly <NUM> for direct injection of gaseous fuel into a cylinder <NUM> of a two-stroke internal combustion piston engine <NUM>. The assembly is configured to attend to injecting gaseous fuel directly to one combustion chamber of the engine, while the fuel is pressurized to injection pressure in liquid phase. The assembly <NUM> comprises a liquefied gas supply manifold section <NUM> and a liquefied gas return manifold section <NUM> which are arranged parallel with each other. In practise the manifold sections are formed using advantageously pipes and flanges. In this case the word section refers to the fact that the assembly in the <FIG> is for one cylinder and usually the engine has more than one cylinders. In that case the manifold is formed of respective number of manifold sections coupled with each other by means of the flanges. The assembly in the <FIG> depicts the minimum components of a fuel delivery line for one cylinder of the engine. And, when the engine comprises several cylinders in a line, arranged one after the other, the engine is provided with corresponding number of assemblies <NUM>, connected to each other such that the liquefied gas supply manifold <NUM>' and a liquefied gas return manifold <NUM>' extend from the first cylinder in the line of cylinders to the last cylinder in the line of cylinders (see the <FIG>). The liquefied gas supply manifold <NUM>' is connected to a liquefied gas supply pipe <NUM> and the liquefied gas return manifold <NUM>' is connected to a liquefied gas return pipe <NUM>.

The assembly comprises further a liquefied gas high-pressure pump unit <NUM>, which is connected to the liquefied gas supply manifold section <NUM> and to the liquefied gas return manifold section <NUM>. The liquefied gas tends to heat in the pump due to the pumping and heat transfer from the surroundings. The pump is provided with heat insulation to minimize undesired warming of the liquefied gas in the pump at the pumping stage. The pump is provided, in addition to the connection to the liquefied gas supply manifold section <NUM>, a connection to the liquefied gas return manifold section <NUM>. That is because in order to prevent - or at least minimize - even partial phase change of the liquefied gas in to gaseous form in the pump, it is advantageous to maintain low temperature of liquefied gas in the pump and therefore a portion of the liquefied gas is led through the pump and returned to the liquefied gas return manifold for cooling the pump unit <NUM>. The liquefied gas at cryogenic conditions is partly circulated through the liquefied gas high-pressure pump unit <NUM> such that part of the liquefied gas which flows from the liquefied gas supply manifold <NUM> to the liquefied gas high-pressure pump unit <NUM> is guided to the liquefied gas return manifold <NUM> to be returned to a source of liquefied gas. A major part of the liquefied gas, which flows from the liquefied gas supply manifold <NUM> to the liquefied gas high-pressure pump unit <NUM>, is guided at an elevated pressure, which results in desired fuel injection pressure, to a high-pressure liquefied gas outlet <NUM> in the liquefied gas high-pressure pump unit <NUM>. The liquefied gas high-pressure pump unit <NUM> comprises preferably a hydraulically operated piston pump. The pump is driven by high pressure hydraulic fluid such that is comprises a drive part to which the hydraulic fluid is guided to reciprocate the drive part and the piston of the pump.

The liquefied gas at elevated pressure is guided via the high-pressure liquefied gas outlet <NUM> to a heat exchanger unit <NUM> which is configured to evaporate the liquefied gas into gaseous form and to heat the gaseous gas to suitable level for injection into the engine. For that purpose, the heat exchanger unit <NUM> is in flow connection with the high-pressure liquefied gas outlet <NUM> and at least one gaseous gas fuel injector <NUM>. The heat exchanger unit <NUM> is provided with a liquefied gas inlet <NUM> and a gaseous gas outlet <NUM>, the liquefied gas inlet being connected to the high-pressure outlet of the liquefied gas high-pressure pump unit <NUM> by means of a fuel feed line <NUM>, more particularly the second fuel feed line <NUM> outside the enclosure <NUM>.

The assembly comprises an enclosure <NUM>, which encloses the liquefied gas supply manifold section <NUM>, the liquefied gas return manifold section <NUM> and the liquefied gas high-pressure pump unit <NUM>. The components containing liquefied or gaseous gas outside the enclosure <NUM> are provided with a separate double wall <NUM> which forms an intermediate space inside the double wall <NUM> bordering the inner space containing gas. For example, pipes are provided with another pipe outside the inner pipe leaving an intermediate space therebetween. A portion of the fuel feed line <NUM> is inside the enclosure, which may be called as the first fuel feed line <NUM>. A portion of the fuel feed line <NUM> is outside the enclosure <NUM>, which may be called as the second fuel feed line <NUM>. The first fuel feed line <NUM> is made of single wall pipe while the second fuel feed line <NUM> is made of double wall pipe. The assembly comprises a lead-through block <NUM> in a wall of the enclosure. The lead-through block <NUM> is provided with conduit <NUM>' to which the first fuel feed line <NUM> inside the enclosure <NUM>, and the second fuel feed line <NUM> outside the enclosure <NUM> are connected with each other. The lead-through block <NUM> separates the intermediate space of the fuel feed line <NUM> from the space of the enclosure <NUM>. The lead-through block <NUM> also seals the connection of the internal space of the enclosure from the surroundings. A leak from a high-pressure line <NUM> between the pump and the injector <NUM> is the most likely point for the leakage because the pressure is considerably high, for example <NUM> MPa, at that portion of the fuel feed line. In case of a failure of the first fuel feed line <NUM> the leak flows into the enclosure <NUM>. Outside the enclosure, in case of a failure of the second fuel feed line <NUM>, the leak flows into an intermediate space of the line, which is separated by the lead-through block <NUM> from the inner space of the enclosure <NUM>. The volume of the portion of the first fuel feed line <NUM> inside the enclosure is so small, that the large volume of the enclosure <NUM>, together with the ventilation of it will take care of the leak easily. When a leak is observed, then the corresponding pump can be immediately shut down, and the leaked amount will remain relatively small compared with the ventilated volume of the enclosure <NUM>.

The components containing liquefied gas within the enclosure are provided with a single wall bordering the inner space containing liquefied gas. Possible leak of gas of the components containing liquefied or gaseous gas outside the enclosure <NUM> is detected and handled suitably. Any gas leaked from the second fuel feed line <NUM> to the intermediate space between inner and outer pipes maybe led by separate piping (not shown) to further processing. Thus, the liquefied gas supply manifold section <NUM> is a single wall manifold and respectively the liquefied gas return manifold section <NUM> is a single wall manifold. It should be noted that the fuel gas is in liquid phase until it is evaporated in the heat exchanger unit <NUM>.

The assembly can be utilized as a gaseous fuel injection module for one cylinder of the engine and when applied to a multi-cylinder engine, the engine is provided with the assembly for each one of its cylinder, wherein the liquefied gas supply manifold sections <NUM> of the assembly are connected with each other and the liquefied gas return manifold sections <NUM> of the assembly are, respectively, connected with each other to form manifolds extending parallel to each other from a first cylinder to a last cylinder in a line of cylinders in the engine.

In order to facilitate ventilation and removal of possibly leaked gaseous fuel away from the enclosure <NUM> of the assembly <NUM>, it is provided an air inlet <NUM> and an air outlet <NUM> connected to a blower <NUM> arranged in connection with the assembly <NUM>. The blower <NUM> may be comprised of one or several blowers connected suitably to obtained desired flow rate and under-pre sure in the enclosure <NUM>. It should be noted that only one air outlet is needed even if several assemblies are provided for serving fuel injection to several cylinders of an engine.

<FIG> discloses schematically an assembly <NUM> for direct injection of gaseous fuel into a cylinder <NUM> of a two-stroke internal combustion piston engine which has been further developed from the assembly shown in the <FIG>. In the <FIG> the gas feed line <NUM>, particularly the part of the second feed line <NUM> containing gaseous fuel, has adequate volume to act as a fuel accumulator. Even if not shown here the exchanger unit <NUM> is also in connection with a suitable heat source. The assembly is configured to pressurize and evaporate liquefied gas fuel and attend to injecting gaseous fuel directly to one combustion chamber. The assembly <NUM> shown in the <FIG> is otherwise similar to that shown in the <FIG> but here the assembly comprises a separate gaseous gas accumulator <NUM> connected to the gaseous gas outlet of the heat exchanger unit by means of the fuel feed line <NUM>.

<FIG> describes the assembly for direct injection of gaseous fuel in a cylinder of a two-stroke, multi-cylinder internal combustion piston engine <NUM>. The large two-stroke crosshead engine, which is depicted in the <FIG>, comprises more than one, usually more than six cylinders <NUM> in a line. The large <NUM>-stroke engine, to which the gaseous fuel feeding system according to the invention is specifically intended, is a low speed, crosshead engine, having a cylinder bore diameter from about <NUM> up to <NUM> and stroke length of about <NUM>,<NUM> to <NUM>,<NUM> meters.

Each one of the cylinders <NUM> is provided with the assembly according to <FIG>. In the embodiment of the <FIG> the assembly comprises for each cylinder at least two fuel injectors <NUM>, which both are connected to a shared, or a common accumulator <NUM>. Depending on e.g. power and the bore diameter of the engine it may be more advantageous to provide each cylinder with three injectors connected to the common accumulator <NUM>. When applied to a multi-cylinder two-stroke engine the enclosure <NUM> has a length L which substantially corresponds to the length of a line of the cylinders <NUM> of the engine. In other words, the enclosure extends from a first cylinder in the line of cylinders to the last cylinder in the line of cylinders of the engine <NUM>.

The enclosure <NUM> is provided with an air inlet <NUM> and an outlet <NUM> at opposite ends of the enclosure <NUM>. The enclosure can be formed of several distinct section connected to one another. The air outlet <NUM> is connected to a blower <NUM>. It should be noted that only one air outlet is needed but instead of one air outlet the enclosure may be provided with two, or even more outlets, even if several assemblies according to <FIG> are provided for serving fuel injection to several cylinders of an engine.

The enclosure <NUM> encloses the liquefied gas supply manifold <NUM>' and the liquefied gas return manifold <NUM>' totally and the liquefied gas high-pressure pump units <NUM>, as well. This way the components containing liquefied gas within the enclosure are provided with a single wall bordering the inner space containing liquefied gas and the common enclosure. Thus, the liquefied gas supply manifold <NUM>' and respectively the liquefied gas return manifold <NUM>' can be called as single wall manifolds. The components containing liquefied or gaseous gas outside the enclosure <NUM> in turn, are provided with a double wall bordering the gaseous fuel feed line <NUM> which contains and delivers gas to the injectors <NUM>.

The invention can be illustrated by such that the engine comprises one fuel delivery line for each one of the cylinders <NUM> of the engine. Thus the assembly comprises several fuel delivery lines for the cylinders of the engine, each fuel delivery line comprising one liquefied gas high-pressure pump unit <NUM> connected to the liquefied gas supply manifold <NUM>' and to the liquefied gas return manifold <NUM>', one heat exchanger unit <NUM> configured to evaporate the liquefied gas and heating the gaseous gas, and one gaseous gas accumulator <NUM> to which the number of fuel injectors <NUM> are connected for receiving gaseous fuel.

The liquefied gas supply manifold <NUM>' is an assembly of multiple gas supply manifold sections <NUM>, comprising one supply manifold section for each cylinder <NUM> of the engine, as is depicted in the <FIG>. Respectively, the liquefied gas return manifold <NUM>' is an assembly of multiple gas return manifold sections <NUM>, comprising one return manifold section for each cylinder of the engine. There is the liquefied gas supply pipe <NUM> and the liquefied gas return pipe <NUM> serving for all of the cylinders of the engine.

The liquefied gas supply manifold <NUM>' and the liquefied gas return manifold <NUM>', as well as each one of the liquefied gas high-pressure pumps <NUM> units are arranged within the common enclosure <NUM> and the heat exchanger units <NUM>, and the gaseous gas accumulators <NUM> are arranged outside the enclosure <NUM>. The accumulator for each cylinder can be installed near the injectors, on top of the respective cylinder head. The enclosure <NUM> is provided for safety reasons. Should there be a leak in the fuel system within the enclosure, the leaked gas can be led away for further processing by means of the blower <NUM>. A leak from a high-pressure line between the pump and the injector <NUM> is the most likely point for the leakage. The volume in one single-wall high-pressure line is so small, that the large volume of the enclosure <NUM> and ventilation of it will take care of the leak easily. When a leak is observed, corresponding pump can be immediately shut down quickly, and the leaked amount of gas will remain relatively small compared to the ventilated volume of the enclosure <NUM>.

Claim 1:
A fuel injection module (<NUM>) for direct injection of gaseous fuel for one cylinder (<NUM>) of a multi-cylinder two-stroke internal combustion piston engine (<NUM>), the module (<NUM>) comprising:
an enclosure (<NUM>), enclosing within the enclosure (<NUM>)
- a liquefied gas supply manifold section (<NUM>,<NUM>'),
- a liquefied gas return manifold section (<NUM>,<NUM>'), arranged parallel with each other within the enclosure (<NUM>), and
- a liquefied gas high-pressure pump unit (<NUM>) connected to the liquefied gas supply manifold (<NUM>, <NUM>') and to the liquefied gas return manifold (<NUM>, <NUM>'), and a high-pressure liquefied gas outlet (<NUM>) in the liquefied gas high-pressure pump unit (<NUM>), and
the module (<NUM>) further comprising outside the enclosure:
- a heat exchanger unit (<NUM>) configured to evaporate the liquefied gas and heating the gaseous gas and being provided with a liquefied gas inlet (<NUM>) and a gaseous gas outlet (<NUM>), the liquefied gas inlet (<NUM>) being connected to the high-pressure outlet (<NUM>) of the liquefied gas high-pressure pump unit (<NUM>) by means of a fuel feed line (<NUM>), and
- at least one gaseous gas fuel injector (<NUM>) connected to the heat exchanger unit,
wherein the fuel feed line (<NUM>) outside the enclosure (<NUM>) is provided with a separate double wall (<NUM>) which forms an intermediate space inside the double wall (<NUM>) and the enclosure (<NUM>) is provided with a lead-through block (<NUM>) via which lead-through block (<NUM>) a portion of the fuel feed line (<NUM>) outside the enclosure (<NUM>) and a portion of the fuel feed line (<NUM>) is inside the enclosure are connected with each other, and which lead-through block (<NUM>) separates the intermediate space of the fuel feed line (<NUM>) from the space of the enclosure (<NUM>).