KR102566767B1 - A fuel valve for a large turbocharged two-stroke uniflow crosshead internal combustion engine - Google Patents

Abstract

A fuel valve (1) for a large turbocharged two-stroke uniflow crosshead internal combustion engine is disclosed, comprising an elongate fuel valve housing (2) having a rear end (3) and a front end (4). and a nozzle (5) with at least one bore (7) opening into at least one nozzle hole (9) having a nozzle hole area, arranged at the front end (4) of the housing (2). 5), a fuel channel 11 extending from the rear end 3 towards the front end 4 and connected to a source of pressurized fuel, and an axially displaceable valve needle 12, the valve needle A closed position in which the axially displaceable valve needle 12 is placed on the valve seat 8 to prevent fuel from flowing into the nozzle 5 and the axially displaceable valve needle 12 is positioned on the valve seat 8 ( 8) to expose the valve needle flow area 13 between the valve needle 12 and the valve seat 8 and at least the fuel channel 11, the valve needle flow area 13 and the nozzle 5 It has an open position allowing fuel to flow through the fuel valve (1) to the nozzle hole (9) via a flow path defined by at least one bore (9) in the interior. The fuel valve 1 is unique in that it includes a flow restrictor 20 in the flow path of fuel.
Thus, by introducing the flow restrictor 20 into the flow path at a different location than the nozzle hole(s) 9 itself, the spray flow rate is determined by the effective open flow area of the flow restrictor 20 and the spray pressure, and accordingly to prevent high exit velocities from the nozzle hole(s) (9) into the cylinder. In this way, fuel can be injected into the combustion chamber 10 of the cylinder of the internal combustion engine at a lower injection speed, thus reducing the risk of extinction of the flame while still maintaining a high fuel supply pressure in the fuel injection system. Fuel, such as ammonia, can thus be injected into the cylinder in a well-controlled mass ratio, which eliminates or at least lowers the risk of extinction of the flame.

Description

Fuel valve for large turbocharged 2-stroke Uniflow crosshead internal combustion engine

The present invention relates to a fuel valve for a large turbocharged two-stroke uniflow crosshead internal combustion engine, the fuel valve comprising: an elongate fuel valve housing having a rear end and a front end, and at least one nozzle bore having a nozzle bore area. a nozzle with at least one bore opening to a nozzle arranged at a front end of the housing; a fuel channel extending from the rear end toward the front end and connected to a source of pressurized fuel; and an axially displaceable valve. a needle, wherein the valve needle is in a closed position where the axially displaceable valve needle is placed on the valve seat to prevent fuel from flowing into the nozzle and the axially displaceable valve needle is lifted from the valve seat to move the valve needle exposing a valve needle flow area between the valve seat and the valve seat and allowing fuel to flow through the fuel valve to the nozzle bore via a flow path defined by at least a fuel channel, a valve needle flow area and at least one bore in the nozzle. and an open position where the fuel valve includes a flow restriction in the flow path of fuel.

Large turbocharged two-stroke uniflow crosshead internal combustion engines are typically used as prime movers in power plants or on large marine vessels such as container ships. Very often, these engines run on heavy or fuel oil.

Recently, there has been a need for large two-stroke diesel engines capable of handling alternative types of fuels such as gaseous fuels such as methanol, LPG, LNG, ethane, ammonia and/or other similar fuels.

Such a fuel is a relatively clean fuel with significantly lower levels of sulfur components, NOx and CO2 in the exhaust gas when used as a fuel for large low speed uniflow turbocharged two stroke internal combustion engines compared to using heavy oil as fuel.

However, there are problems associated with using such fuels in large turbocharged two-stroke uniflow crosshead internal combustion engines. One of these issues is the nature and predictability of the fuel to self-ignite, both of which are essential to keeping such an engine under control. Therefore, existing large turbocharged two-stroke uniflow crosshead internal combustion engines typically utilize pilot injection of oil in conjunction with injection of gaseous fuel to ensure reliable and timely ignition of the gaseous fuel.

Also, these engines are typically provided with two or three fuel valves arranged on each cylinder cover. The fuel valve may have a spring-loaded, axially movable valve needle acting as a movable valve member. When the pressure of the fuel exceeds a preset pressure (typically about 350 Bar), the axially movable valve needle is lifted from the valve seat and fuel is allowed to flow through a nozzle in front of the fuel valve and into the combustion chamber. The fuel valve needle may be actuated and controlled by external hydraulic pressure or electric power.

Currently, ammonia can be produced mainly in an environmentally friendly way using electricity from renewable energy sources such as solar, wind and wave energy, and because the combustion of ammonia itself does not result in the formation of carbon-containing greenhouse gases such as carbon dioxide. Because of this, it enjoys very high interest as a fuel for internal combustion engines.

When ammonia is used as fuel in an internal combustion engine, the engine can operate according to the Otto principle in which the ammonia fuel is introduced at a relatively low pressure during the compression stroke of the piston, or the engine can operate when the piston is close to top dead center (TDC). It can operate via the diesel principle, in which ammonia fuel is injected under high pressure into the combustion chamber when it burns. During the ammonia fuel injection and combustion phases of the piston cycle, cylinder pressure undergoes rapid level changes due to both compression/expansion of the chamber and combustion occurring.

Currently, all fuel injection systems for internal combustion engines operating on the diesel principle inject fuel at significantly higher than the maximum pressure inside the cylinder combustion chamber, in order to ensure a stable and well-controlled mass rate of fuel into the cylinder during injection. ask for pressure The main pressure drop is always at the nozzle orifice where the fuel is injected at high speed into the combustion chamber. Thus, the injection pressure level together with the effective nozzle area defines the fuel injection mass ratio.

This is desirable for most fuels, but when ammonia is injected into the combustion chamber of a cylinder of an internal combustion engine, the injection pressure and speed must be much lower in order to allow stabilization of the flame close to the fuel valve or injector without interfering with combustion. there may be a need Ammonia has a laminar flame velocity nearly ten times lower than most hydrocarbons, so flame extinguishing/extinguishing can occur even at low turbulence levels. Also, if the velocity of the fuel jet is too high, it may sweep/divert the flame downstream without a chance to stabilize itself in the limited lift-off length from the nozzle hole exit. This can be seen as like blowing out a candle.

Existing fuel injection systems cannot inject fuel at a constant injection rate at low pressures because the downstream pressure changes rapidly during the injection period. Temporary control of the injection pressure (for example by controlling the hydraulic drive pressure of the booster or the fuel pressure of the common rail system within milliseconds) is not possible.

Fuel valves of the kind mentioned in the introduction are known from patent documents WO 2015/091180 A1 (corresponding to JP 2017/507269) and US 2009/0032622. In these known fuel valves the flow restrictor is arranged in the flow path upstream of the valve seat. Thus, in these known fuel valves, the force from the fuel medium acting on the valve needle, which needs to be counteracted by a spring, an actuator (electrical, hydraulic, etc.) will be affected by the flow restrictor or a change in the flow restrictor. . Therefore, the demand for actuation force and control of the actuation of the valve needle depends on the flow restrictor. Also, opening of the valve needle in these prior art fuel valves will immediately cause a rapid decrease in the pressure acting on the needle, which in turn will require a very large actuation force to keep the needle open.

The present invention also relates to a large turbocharged two-stroke uniflow crosshead internal combustion engine comprising a fuel valve as described above and as claimed in the appended claims.

It is an object of the present invention to provide a fuel valve of the kind mentioned at the outset, in which the above-mentioned problems related to the dissipation of sparks and forces from the fuel medium acting on the valve needle are at least significantly reduced.

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

According to a first aspect, there is provided a fuel valve for a large turbocharged two-stroke uniflow crosshead internal combustion engine, the fuel valve having an enlongated fuel valve housing having a rear end and a front end, and a nozzle hole area ( a nozzle having at least one bore opening into at least one nozzle hole having an area, the nozzle being arranged at the front end of the housing and a fuel extending from the rear end toward the front end and being connected to a source of pressurized fuel. a channel; and an axially displaceable valve needle, wherein the axially displaceable valve needle is positioned on a valve seat to prevent fuel from flowing into the nozzle and to a closed position; It is lifted from the valve seat to expose the valve needle flow area between the valve needle and the valve seat and fuel to the nozzle hole via a flow path defined by at least a fuel channel, a valve needle flow area and at least one bore in the nozzle. having an open position allowing fuel to flow through the valve, the fuel valve including a flow restriction in the flow path of the fuel, the flow restriction being provided in the flow path between the valve seat and the nozzle hole(s). characterized by

Thus, by introducing a flow restrictor into the flow path between the valve seat and the nozzle orifice(s), the spray flow rate at a location different from the nozzle orifice itself (or nozzle orifices itself) is determined by the spray pressure and the effective open flow area of the flow restriction. This prevents high exit velocities from the nozzle hole(s) into the cylinder. In this way, fuel can be injected into the combustion chamber of the cylinder of the internal combustion engine at a lower injection speed and thus lower the risk of extinction of the flame while still maintaining a high fuel supply pressure in the fuel injection system. Thus, fuel such as ammonia can be injected into the cylinder in a well controlled mass ratio which eliminates or at least lowers the risk of flame extinction. Also, the force from the fuel medium acting on the valve needle is not affected by the flow restriction.

The injection system can maintain high feed pressure either by controlling the pressure in the common-rail system or by maintaining a constant high pressure hydraulic pressure driving the booster valve.

The flow restriction must provide a flow area that ensures the correct fuel flow rate at the selected pressure level. Therefore, it is preferred that the flow area of the flow restrictor be significantly smaller than the nozzle orifice area. In a preferred embodiment of the present invention the flow area of the flow restrictor is less than 3/4, preferably less than 1/2, most preferably less than 1/3 the nozzle orifice area. Thus, in this way fuel can be injected through the nozzle orifice at a constant mass ratio and velocity independent of cylinder pressure.

The nozzle may include one or more bores that open into at least one nozzle orifice. The nozzle holes in such an embodiment preferably have the same nozzle hole area. However, nozzles with more nozzle orifices of different areas are conceivable. In another embodiment, the nozzle may include one bore through which all nozzle orifices are energized. In embodiments with nozzles having more nozzle orifices, it is the total nozzle orifice area of all nozzle orifices, which must be compared and sized to the flow area of the flow restrictor.

In one embodiment of the present invention, when the flow restrictor is provided in the flow path between the valve seat and the nozzle hole, a cross-sectional area reduction of at least a portion of the bore may be provided. In practice such a restriction may be provided by introducing a flow restricting insert into a bore extending from the valve seat to the nozzle bore. Where fuel is delivered to each nozzle hole through a separate bore for each nozzle hole, flow restricting inserts must be provided in all bores, the flow restricting area of the inserts being the nozzle hole of each individual nozzle hole from which fuel is supplied. smaller than the area

In another embodiment of the present invention, where a flow restrictor is also provided in the flow path between the valve seat and the nozzle hole(s), the nozzle of the fuel valve comprises only one bore, where one bore comprises multiple nozzles. Only one flow restricting insert will be needed to fuel the orifices and have a flow restricting area less than the sum of all nozzle orifice flow areas.

In another embodiment of the present invention, the fuel valve may be a type of slide valve, wherein the nozzle includes only one bore that delivers fuel to a plurality of nozzle holes and the valve needle acts as a cut-off shaft. formed, which extends into the bore and blocks the nozzle orifices when the valve needle is in the closed position. In a valve of that kind, the flow restriction in such a valve may be provided in said at least one orifice, since the fuel passes through the shut-off shaft via the at least one orifice when the valve needle is in the open position.

The nozzle holes in the nozzle may be distributed radially and preferably axially over the nozzle. The nozzle apertures may be located axially near the tip of the nozzle, which tip is preferably closed. The nozzle apertures may preferably be positioned over a relatively narrow nozzle circumference, such as between approximately 50° and 120°. The radial orientation of the nozzle orifices may be further directed away from the wall of the combustion chamber defined by the cylinder liner. Also, the nozzle holes can be oriented so that they are generally in the same direction as the direction of the scavenging vortex in the combustion chamber caused by the configuration of the scavenging port.

The invention will be explained in more detail with reference to exemplary embodiments shown in the following figures:
1 shows an embodiment of a fuel valve according to the invention, wherein a flow restrictor is provided in a bore of a nozzle such that the flow area of at least a part of the bore is smaller than the nozzle hole area.
Figure 2 shows an embodiment of a fuel valve according to the invention, wherein the nozzle comprises only one bore and a flow restrictor is provided in said bore such that the flow area of at least part of the bore is smaller than the nozzle hole area.
3 shows an embodiment of a fuel valve according to the invention, wherein the fuel valve is a slide valve, the nozzle has only one bore and the valve needle is formed as a shut-off shaft, and the flow restrictor is formed in an orifice of said shut-off shaft. Provided.

In the detailed description that follows, a fuel valve according to the present invention will be described for use in a large two-stroke uniflow scavenged internal combustion engine with a crosshead, although it should be understood that internal combustion engines may be of other types.

1 shows an exemplary embodiment of a fuel valve 1 according to the invention. This exemplary embodiment and the embodiment shown in FIGS. 2 and 3 are shown in different cross-sections, and therefore are identical structural elements not shown in all figures, but identical reference numerals for corresponding elements in all three figures. used

The fuel valve 1 shown in FIG. 1 comprises an elongated fuel valve housing 2 having a rear end 3 and a front end 4 . At the front end of the housing 2 there is a nozzle 5 mounted by a retaining element 6 . The nozzle 5 comprises five bores 7 extending from the valve seat 8 and opening into nozzle holes 9 for injecting fuel into the combustion chamber 10 , as shown in FIG. 1 . The bore 7 has a diameter X defining its flow area and the nozzle hole area is defined by the diameter Y of the nozzle hole 9 . The fuel valve 1 further comprises a fuel channel not shown in FIG. 1 , which extends from the rear end 3 toward the front end 4 of the fuel valve 1 . The fuel channel is connected to a source of pressurized fuel, not shown. The fuel valve also includes a fuel return channel, not shown. To control the flow of fuel through the fuel valve (1), it comprises an axially displaceable valve needle (12), which is mounted on the valve seat (8). The closed position and axially displaceable valve needle 12, which is placed in the valve seat 8 and prevents fuel from flowing into the nozzle 5, is lifted from the valve seat 8 to open the valve needle flow area 13. It has an open position which exposes and allows fuel to flow through the fuel valve (1) into the nozzle holes (9). Thus, the fuel valve 1 has a flow path defined by the fuel channel, the valve needle flow area 13 and the bore 7 of the nozzle 5 .

An axially displaceable valve needle 12 is slidably received with a narrow gap in a longitudinal bore 14 of the elongated valve housing 2 . The valve needle 12 shown has a conical section formed to mate with the valve seat 8 . In the closed position the conical section of the valve needle 12 rests on the valve seat 8 . The conical section is lifted from the valve seat 8 in the open position and the valve needle 12 is resiliently urged towards the closed position by means of a pre-tensioned helical spring. The pre-tension helical spring 15 acts on the valve needle 12 and urges the valve needle 12 towards the closed position where the conical section rests against the valve seat 8 . The helical spring 15 is a helical wire spring accommodated in the spring chamber 16 of the elongate fuel valve housing 2 .

The fuel valve 1 shown in FIGS. 2 and 3 basically includes the same elements as the fuel valve shown in FIG. 1 , but with some differences as will be explained below. The nozzle 5 of the fuel valve in FIGS. 2 and 3 comprises only one single hole 7 supplying fuel to all the nozzle holes 9 . The nozzle 5 is also shown being positioned relative to the housing 2 by means of a locating pin 22, which also applies to the valve in FIG. Also in these fuel valves, the nozzle 5 is mounted on the housing 2 by means of a retaining element 6 shown only in FIG. 1 .

The fuel valve shown in FIG. 3 is a slide valve featuring a special design of the valve needle 12 . The valve needle (12) of the slide valve comprises an elongated member, which protrudes into one single bore (7) and is hollow furthest from the solid first part (23) and the valve seat (8). a second part (24) of which hollow part contains at least one orifice (26) and is open at its free end (25). In operation, when the valve needle is lifted to the open position away from the valve seat (8), the free end (25) of the elongate member is also lifted freely from the nozzle hole (9) and the elongate member and the bore (7) are lifted freely. allows fuel to flow within the bore 7 between the walls of the orifice(s) 26 and into the hollow portion 24, from which fuel flows out of the open free end 25 and into the nozzle hole ( 9) continues to flow into

The elongated valve housing 2 and other components of the fuel valve 1, as well as the nozzle 5, are in a preferred embodiment made of steel, for example tool steel and stainless steel.

As mentioned, the nozzle 5 has nozzle holes 9 distributed radially and preferably axially above the nozzle 5 . The nozzle holes 9 are located axially near the tip 17 of the nozzle 5, the tip 17 being closed in the illustrated embodiments. The nozzle apertures 9 are distributed over a relatively narrow range around the nozzle 5 , such as between approximately 50° and 120° in the presented embodiments. The radial orientation of the nozzle hole 9 may in such an embodiment be directed away from the wall of the combustion chamber defined by the cylinder liner. Also, the nozzle hole 9 can be oriented in approximately the same direction as the direction of the scavenging swirl in the combustion chamber caused by the configuration of the scavenging port (this swirl is a well-known feature of large two-stroke turbocharged internal combustion engines of the Uniflow type). lim).

According to the invention, the fuel valve includes a flow restrictor 20 provided in the flow path between the valve seat 8 and the nozzle hole 9 . Thereby, fuel can be injected into the combustion chamber of the cylinder of the internal combustion engine at a low injection speed while still maintaining a high fuel supply pressure in the fuel injection system, thereby reducing the fear of extinction of the flame. Fuel, such as ammonia, can thus be injected into the cylinder in a well-controlled mass ratio that eliminates or at least reduces the risk of flame extinction.

In the embodiment shown in FIG. 1 a flow restrictor 20 is provided in the flow path between the valve seat 8 and the nozzle hole 9 . In practice, a reduction in the cross-sectional area of at least part of the bore 7 is provided, but in order to facilitate the manufacture of the nozzle 5, as shown, the bore 7 has the same diameter over its entire length and is in the form of an insert. Preferably, a flow restrictor 20 is mounted in each bore 7, wherein the flow restrictor 20 has a flow area smaller than the nozzle hole area.

In the embodiment shown in FIG. 2 a flow restrictor 20 is also provided in the flow path between the valve seat 8 and the nozzle hole 9 . In practice, a reduction in the cross-sectional area of a portion of the bore 7 is provided by mounting an insert in the bore 7, wherein the flow restrictor 20 in the form of an insert has a flow area smaller than the total area of the nozzle hole 9. .

In the embodiment shown in FIG. 3 a flow restrictor 20 is also provided in the flow path between the valve seat 8 and the nozzle hole 9 . In this embodiment, the flow restrictor 20 is provided by mounting an insert in the orifice(s) 26 or by ensuring that the total flow area of the orifice(s) 26 is smaller than the total area of the nozzle holes 9. provided in the orifice(s) 26 by making the orifice(s) 26 of a smaller diameter to ensure

Claims (10)

As a fuel valve (1) for a large turbocharged two-stroke uniflow crosshead internal combustion engine,
The fuel valve (1) has an elongate fuel valve housing (2) with a rear end (3) and a front end (4) and at least one bore opening into at least one nozzle hole (9) having a nozzle hole area. A nozzle (5) with (7), the nozzle (5) arranged at the front end (4) of the housing (2) and extending from the rear end (3) towards the front end (4), and providing a flow of pressurized fuel. a fuel channel 11 connected to a supply source and an axially displaceable valve needle 12;
The valve needle is in a closed position in which the axially displaceable valve needle 12 is placed on the valve seat 8 to prevent fuel from flowing into the nozzle 5 and the axially displaceable valve needle 12 is positioned on the valve seat 8 to prevent the fuel from flowing into the nozzle 5. It is lifted from the valve seat 8 to expose the valve needle flow area 13 between the valve needle 12 and the valve seat 8 and at least the fuel channel 11, the valve needle flow area 13 and the nozzle has an open position allowing fuel to flow through the fuel valve (1) to the nozzle hole (9) via a flow path defined by at least one bore (7) in (5);
The fuel valve 1 includes a flow restrictor 20 in the flow path of fuel,
The flow restrictor (20) is provided in the flow path between the valve seat (8) and the nozzle hole (s) (9),
The fuel valve (1), characterized in that the flow area of the flow restrictor (20) is smaller than the nozzle hole area. delete The method of claim 1,
The fuel valve (1), characterized in that the flow area of the flow restrictor (20) is less than 3/4 of the nozzle hole area. The method of claim 1,
The fuel valve (1), characterized in that the nozzle (5) comprises at least one bore (7) opening into at least one nozzle hole (9). The method of claim 1,
The fuel valve (1), characterized in that the nozzle (5) comprises only one bore (7) opening into at least one nozzle hole (9). The method of claim 5,
A fuel valve (1), characterized in that it is a slide valve comprising a valve needle (12) with an elongate member protruding into one single bore (7). The method of claim 6,
The elongate member comprises a solid first part (23) and a hollow second part (24) furthest from the valve seat (8), the hollow part comprising at least one orifice (26) and having a free end ( Fuel valve (1), characterized in that it opens at 25). The method of claim 1,
The flow restrictor 20 is an insert mounted in at least one bore 7 or in at least one orifice 26 of the hollow second part 24 of the valve needle 12 with an elongated member, said valve Fuel valve (1), characterized in that it is provided in the flow path between the seat (8) and the nozzle hole (s) (9). According to any one of claims 4 to 8,
The nozzle holes 9 of the nozzle 5 are distributed radially and axially above the nozzle 5, and the nozzle holes 9 are axially located near the tip 17 of the nozzle 5. And, the fuel valve (1), characterized in that the front end (17) is closed. A large turbocharged two-stroke uniflow crosshead internal combustion engine comprising a fuel valve (1) as defined in claim 1.

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