Patent Description:
Large turbocharged two-stroke uniflow scavenged crosshead internal combustion engines are typically used as prime movers in large ocean-going ships, such as container ships or in power plants.

The cylinders of these engines are provided with a single exhaust valve centrally placed in the cylinder cover i.e. at the top of the cylinder and with a ring of piston controlled scavenge ports at the lower region of the cylinder liner. Accordingly, the direction of transport of gas through the cylinder is always from bottom to top, hence the designation uniflow scavenged. The scavenge ports are slanted to create a swirl in the gases in the combustion chamber.

Two or three fuel valves are disposed in the cylinder cover around the centrally placed exhaust valve, with their nozzles projecting into the combustion chamber. The fuel valves are peripherally disposed (i.e. not central) in the cylinder cover with the nozzle bores of the nozzles substantially directed with the swirl, away from the cylinder wall and into the combustion chamber.

Occasionally, a single nozzle hole of a nozzle is directed against the swirl in the combustion chamber.

A nozzle is attached to the forward or distal end of a fuel valve. The fuel valve comprises an elongated housing with the proximal or rear end protruding from the upper surface of the cylinder cover and with the elongated fuel valve housing extending through the cylinder cover and with the nozzle at the forward or distal end of the elongated fuel valve housing projecting into the combustion chamber.

Known nozzles for large two-stroke diesel engines of the crosshead type typically have an elongated nozzle body comprising a cylindrical section with a straight main bore leading from the base of the nozzle at a proximal end of the nozzle body to nozzle bores that are located near the tip or distal end of the nozzle body. The tip or distal end can be round or flat but is closed since the nozzle bores must not be directed downwardly towards the piston (when the piston is at top dead center, i.e. the moment of fuel injection for a compression igniting engine, the upper surface of the piston is very close to the tip of the nozzle). Thus, the nozzle bores are mainly laterally directed relative to the main axis of the nozzle/fuel valve and typically approximately at a right angle to the main axis of the engine cylinder. Typically, each nozzle is provided with three to seven nozzle bores that are all connected to the main bore.

Typically, the known fuel valves for injecting liquid fuel are provided with an axially displaceable valve needle that cooperates with a conical valve seat for controlling the flow of fuel to the nozzle. In addition, the forward section of the valve needle comprises a distal cylindrical that is tightly received in the main bore and acts as a slide valve for closing off the nozzle bores when the valve needle is in the closed position to thereby significantly reduce the so-called sac volume, i.e. the residual volume of fuel in the space formed by the main bore in the nozzle. Without such a slide valve arrangement, the volume of residual fuel in the main bore (and in the nozzle bores) would drip into the combustion chamber after a finished fuel injection event, which has detrimental effects on fuel consumption, reliability, and emissions. Document <CIT> discloses a fuel valve for a large two-stroke turbocharged self-igniting internal combustion engine.

Since the nozzle body projects into the combustion chamber it is exposed to the hot gases of the combustion chamber and parts of the nozzle body will therefore reach relatively high temperatures of up to approximately <NUM>. The incoming fuel for heavy fuel oil operated engines is approximately <NUM>. Thus, the incoming fuel in the main bore leaving the nozzle through the nozzle bores has a significantly lower temperature than the gas surrounding the outer surface of the nozzle body. Therefore, the material of the nozzle body is exposed to a substantial temperature gradient, causing stresses in the material of the nozzle.

Thus, the nozzles risk developing cracks in the area of the nozzle where the nozzle holes are located, in particular between the nozzle holes, due to thermal fatigue of the material when they are exposed to high operating temperature gas in the combustion chamber and the high cooling effect of the injected fuel.

This problem cannot be solved by simply increasing the distance between the nozzle holes so that there is more material between nozzle holes thereby reducing the temperature gradient since it is highly undesirable to increase the diameter of the nozzle since this would likely increase the amount of heat that is transferred from the combustion chamber to the nozzle and since it is not possible to simply increase the radial spacing between the nozzle holes, since the radial spread of the nozzle holes is limited to an approximately <NUM>° angle due to the two or three fuel valves in the cylinder cover being peripherally positioned. This is especially true when there is a slide valve in the nozzle, requiring that the main bore in the nozzle has a certain diameter and thus the limitation to the resulting wall thickness of the nozzle body. Further, in a fuel valve with a slider in the nozzle body, it is a requirement that the nozzle bores open at substantially the same axial distance from the base of the nozzle to the main bore if the nozzle bores are to inject fuel simultaneously.

<CIT> discloses an injection rate shaping nozzle assembly for a fuel injector is provided which includes a closed nozzle valve element and a rate shaping control device including an injection spill circuit for spilling a portion of the fuel to be injected to produce a predetermined time varying change in the flow rate of fuel injected into a combustion chamber. The spill circuit includes a spill passage integrally formed in the nozzle valve element. The rate shaping control device may include a spill accelerating chamber formed in the nozzle valve element for creating a rapid increase in the spill flow rate. A spill circuit purge device is provided to remove fuel from the spill circuit and accelerating chamber between each of the injection events thereby ensuring an unimpeded, effective spill fuel flow during the next spill event. The purge device includes a purge passage formed of a predetermined size for restricting the flow of purge gas to ensure sufficient fuel removal from the injection spill circuit while avoiding excessive purge gas flow. The purge passage may include an annular clearance gap formed between the nozzle valve element and the nozzle housing wall, or alternatively, may include an orifice passage formed in the inner portion of the nozzle valve element.

In view of the above, it is an object of the present invention to provide a fuel valve for injecting liquid fuel into a large two-stroke uniflow scavenged internal combustion engine of the crosshead type that overcomes or at least reduces the problems mentioned above.

Further implementation forms are apparent from the dependent claims, the description, and the figures.

According to a first aspect, there is provided a fuel valve for injection of liquid fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads, the fuel valve comprising:.

By providing individual supply passages that are angled to the straight nozzle bores and to the main nozzle bore, more freedom is provided for choosing the angle of the straight nozzle bores to the main axis and their position in the nozzle body material, thereby allowing a choice of position and orientation of the nozzle bores that results in more nozzle body material between neighboring nozzle bores to thereby reduce the thermal coefficient and thermal stress related crack formation, without needing to increase the overall size of the nozzle, in particular the diameter of the cylindrical part of the nozzle.

According to a possible implementation form of the first aspect, the individual supply passages are, seen from the position where the individual supply passage concerned connects to the main bore directed away from the longitudinal axis at a first angle with the longitudinal axis, resulting in the "base" of the of the straight nozzle bore being placed more radially outward, thereby allowing for more distance between neighboring straight nozzle bores and thus more nozzle body material between neighboring nozzle bores. In this context, the "base" positions where a straight nozzle bore connects to the individual supply passage concerned.

According to a possible implementation form of the first aspect, the straight nozzle bore, seen from the position where the straight nozzle bore concerned connects to the individual supply passage, is directed away from the longitudinal axis at a second angle with the longitudinal axis, the second angle being greater than the first angle.

According to a possible implementation form of the first aspect, the individual supply passages are straight bores, preferably with a rounded, i.e. spherical extremity to reduce stress in the nozzle bore material.

According to a possible implementation of the first aspect, the cylindrical end section fluidically connects the individual supply passages to the main straight bore when the valve needle is in the open position.

According to a possible implementation of the first aspect, the cylindrical end section covers the opening of the individual supply passages towards the straight main bore when the valve needle is in the closed position.

According to a possible implementation of the first aspect, the cylindrical end section does not cover the opening of the individual supply passages towards the straight main bore when the valve needle is in the open position.

According to a possible implementation of the first aspect, the individual supply passages open to the main bore at a given axial distance from the inlet, and the cylindrical end section extends past the given axial distance in the closed position of the valve needle.

According to a possible implementation of the first aspect, an axially displaceable valve needle is slidably received in a longitudinal bore in the elongated valve housing, the valve needle resting on a valve seat in the closed position, the valve seat is preferably a conical valve seat, the valve needle has lift from the valve seat in the open position and the valve needle preferably being biased towards the closed position, and preferably, a fuel chamber is provided that surrounds the valve needle and opens to the valve seat.

According to a possible implementation of the first aspect, the fuel valve comprises a fuel inlet port in the elongated fuel valve housing for connection to a source of liquid fuel.

According to a possible implementation of the first aspect, all of the straight nozzle bores have a substantially equal cross-sectional area or diameter and preferably also a substantially equal length.

According to a possible implementation of the first aspect, all of the straight nozzle bores have an equal diameter, and preferably, the individual supply passages have a diameter greater than that of the straight nozzle bores.

According to a possible implementation of the first aspect, the straight main bore is formed in a bushing that is solidly received in a bore in the nozzle body.

According to a possible implementation of the first aspect, the cylindrical end section is hollow to form a fluid passage, the fluid passage preferably opening proximally to the exterior of the shank and the fluid passage preferably opening distally in an axial direction.

According to a possible implementation of the first aspect, wherein the straight nozzle bores open to the cylindrical surface.

According to a possible implementation of the first aspect, a preferably rounded transition surface is arranged between the substantially cylindrical surface and a flat distal end surface of the nozzle body.

According to a possible implementation of the first aspect, the straight nozzle bores open to the cylindrical surface and/or to the transition surface.

According to a possible implementation of the first aspect, the straight nozzle bores each have a nozzle axis I,II,III,IV,V, and wherein the nozzle axis I,II,III,IV,V of each of the nozzle bores is arranged at an obtuse angle α with the main direction X.

According to a possible implementation of the first aspect, the radial components of each of the nozzle axes I,II,III,IV,V relative to the main axis X are distributed, preferably substantially equally distributed, over a circular sector with an arc less than <NUM> deg. , preferably less than <NUM> deg. and even more preferably less than <NUM> deg.

According to a possible implementation of the first aspect, at least three of the straight nozzle bores are connected to the straight main bore by an individual supply passage that is arranged at an angle to the straight main bore and to the straight nozzle bore concerned.

According to a second aspect, there is provided a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads comprising a fuel valve according to the first aspect or any one implementation thereof.

These and other aspects of the invention will be apparent from the embodiments described below.

In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the example embodiments shown in the drawings, in which:.

In the following detailed description, a fuel valve, and a large two-stroke engine in which the fuel valve is used will be described by the example embodiments. <FIG> show a large low speed turbocharged two-stroke internal combustion engine with a crankshaft <NUM> and crossheads <NUM>. <FIG> shows a diagrammatic representation of a large low speed turbocharged two-stroke internal combustion engine with its intake and exhaust systems. In this example embodiment, the engine has six cylinders (that are formed by cylinder liners <NUM>) in line. Large turbocharged two-stroke internal combustion engines have typically between five and sixteen cylinders in line, carried by an engine frame <NUM>. The engine may e.g. be used as the main engine in an ocean-going vessel or as a stationary engine for operating a generator in a power station. The total output of the engine may, for example, range from <NUM>,<NUM> to <NUM>,<NUM> kW.

The engine can be a diesel (compression-igniting) engine of the two-stroke uniflow type with scavenge ports <NUM> in the form of a ring of piston-controlled ports at the lower region of the cylinder liners <NUM> and an exhaust valve <NUM> at the top of the cylinder liners <NUM>. Thus, the flow in the combustion chamber is always from the bottom to the top and thus the engine is of the so-called uniflow type. The scavenging air is passed from the scavenging air receiver <NUM> to the scavenging air ports <NUM> of the individual cylinders that are formed by the cylinder liners <NUM>. A reciprocating piston <NUM> in the cylinder liner <NUM> compresses the scavenging air, fuel is injected via the nozzles of two or three fuel valves <NUM> that are arranged in the cylinder cover <NUM>. Combustion follows and exhaust gas is generated. When an exhaust valve <NUM> is opened, the exhaust gas flows through an exhaust duct <NUM> associated with the cylinder <NUM> concerned into an exhaust gas receiver <NUM> and onwards through a first exhaust conduit <NUM> to a turbine <NUM> of the turbocharger <NUM>, from which the exhaust gas flows away through a second exhaust conduit <NUM>. Through a shaft <NUM>, the turbine <NUM> drives a compressor <NUM> supplied via an air inlet <NUM>.

The compressor <NUM> delivers pressurized charging air to a charging air conduit <NUM> leading to the charging air receiver <NUM>. The scavenging air in the conduit <NUM> passes through an intercooler <NUM> for cooling the charging air. The cooled charging air passes via an auxiliary blower <NUM> driven by an electric motor <NUM> that pressurizes the charging air flow in low or partial load conditions to the charging air receiver <NUM>. At higher loads the turbocharger compressor <NUM> delivers sufficient compressed scavenging air and then the auxiliary blower <NUM> is bypassed via a non-return valve <NUM>.

The cylinders are formed in a cylinder liner <NUM>. The cylinder liners <NUM> are carried by a cylinder frame <NUM> that is supported by the engine frame <NUM>.

<FIG> illustrates an embodiment of one of the two or three fuel valves <NUM> that are mounted in a through-going bore in the cylinder cover <NUM> of each cylinder with the rear end <NUM> of the fuel valve <NUM> protruding from the upper side of the cylinder cover <NUM> and with the distal end (tip) of the nozzle <NUM> marginally protruding into the combustion chamber. The fuel valve <NUM> comprises an elongated fuel valve body <NUM> with a nozzle holder at its distal (forward) end <NUM>. The nozzle holder connects the nozzle <NUM> to the elongated fuel valve body <NUM>. Liquid fuel (e.g. ethanol, methanol, diesel, heavy fuel oil) is delivered in a controlled and timed manner by the fuel valve <NUM> to the combustion chamber <NUM> via the nozzle <NUM>. The fuel valve <NUM> illustrated in <FIG> has an elongated external housing <NUM> which at its proximal end <NUM> has a head by which the fuel valve <NUM> in a known manner may be mounted in the cylinder cover <NUM> and be connected with a fuel pump (not shown) of the internal combustion engine.

The head at the proximal end <NUM> includes a fuel inlet <NUM> which is in flow connection with a duct extending through the valve body <NUM>. An axially displaceable valve needle <NUM> is journaled in the valve housing <NUM> and has an open position in which the valve needle <NUM> has lift from a preferably conical valve seat <NUM> and a closed position in which a matching section of the valve needle <NUM> rests in a sealing fashion on the valve seat <NUM>. The valve needle is resiliently biased towards the closed position by resilient means, in the present embodiment formed by a helical spring <NUM>. Lift of the valve needle <NUM> against the bias of the helical spring <NUM> is caused by the pressure of the fuel supplied to the fuel valve <NUM> acting on a surface of the valve needle <NUM> or of a piston or plunger operably connected to the valve needle <NUM>. A fuel chamber <NUM> surrounds the valve needle <NUM> and opens to the valve seat <NUM>.

The fuel valve <NUM> carries at its distal end <NUM> a nozzle <NUM>. The nozzle <NUM> is configured to project into the combustion chamber <NUM> of the engine cylinder liner <NUM> when the fuel valve <NUM> is mounted on the cylinder cover <NUM>.

In the present embodiment, the fuel valve comprises an axially movable valve needle <NUM> that comprises a conical section that cooperates with a conical seat <NUM> in the longitudinal housing <NUM> of the fuel valve <NUM>.

<FIG> illustrates how the nozzles <NUM> are peripherally positioned in the cylinder cover <NUM> and illustrates the direction of the fuel jets (which corresponds to the direction of the axes I,II,III,IV, and V of straight nozzle bores <NUM> in the nozzles <NUM>. The direction of the swirl of the gases in the combustion chamber is illustrated by the curved interrupted arrow <NUM>.

<FIG> illustrates a fuel valve <NUM> according to another embodiment, that is similar to the embodiment of <FIG>, except for comprising a booster pump to amplify the pressure of the fuel that is supplied to the fuel valve <NUM>. The main component of the booster pump is a booster plunger <NUM>. The other components of the fuel valve <NUM> according to this embodiment and the nozzle <NUM> are in concept identical to the fuel valve of <FIG>.

<FIG> illustrate the nozzle <NUM> and the distal section of the valve needle <NUM> in greater detail.

The nozzle <NUM> has a nozzle body that extends from a base <NUM> at a proximal end to a closed distal end <NUM> that forms the tip of the nozzle <NUM>. A cylindrical portion <NUM> of the nozzle body extends from the base to the distal end <NUM>. The nozzle body is made from a suitable material, e.g. a suitable alloy as is well-known in the art.

An inlet <NUM> opens to the base <NUM> for receiving liquid fuel from the fuel valve <NUM> when the valve needle <NUM> is in the open position. A single straight main bore <NUM> extends longitudinally from the inlet <NUM> into said nozzle body. In the present embodiment, the straight main bore <NUM> is formed in a bushing <NUM> that is solidly received in a bore <NUM> in the valve body, e.g. by a shrink fit, but it is understood that the nozzle can be constructed without the bushing <NUM> so that the nozzle body is made from one single piece of material.

The closed distal end (tip) <NUM> comprises a substantially planar end surface <NUM> with a circular or elliptical outline. The end surface <NUM> connects to the cylindrical portion via a curved or rounded transition surface <NUM>.

The nozzle <NUM> is provided with a plurality of straight nozzle bores <NUM>. The nozzle <NUM> is provided with any desirable number of nozzle bores <NUM>, preferably between three and seven nozzle bores <NUM> even more preferably between three and six nozzle bores <NUM>, and most preferably five or six nozzle bores <NUM>. The nozzle <NUM> according to the present embodiment is provided with five nozzle bores <NUM>.

Each straight nozzle bore <NUM> opens to the outer surface of the nozzle body <NUM> at a different radial angle to cause a fan of fuel rays (as shown in <FIG>) to be injected into the combustion chamber when the fuel valve <NUM> opens. Each straight nozzle bore <NUM> opens to the outer surface of the nozzle body at a different radial angle. Preferably, the nozzle bores <NUM> opens to the cylindrical surface <NUM> and/or) and/or to the transition surface <NUM>.

The nozzle holes <NUM> each have a nozzle axis I,II,III,IV, and V (<FIG>). The nozzle axis I,II,III,IV, and V of each of the holes <NUM> is arranged at an obtuse angle α with the main axis X. The obtuse angle α can be different for each of the nozzle holes <NUM>. The radial components of each of the nozzle axes I,II,III,IV, and V relative to the main axis X are distributed over a circular sector with an arc of less than <NUM> deg. preferably less than <NUM> deg. and even more preferably less than <NUM> deg. The radial components of each of the nozzle axes (I,II,III,IV, and V) relative to the main axis X are substantially evenly distributed over the circular section, to maximize the amount of nozzle body material between the individual nozzle holes <NUM>.

The base <NUM> is provided with an inlet port <NUM> for receiving fuel from said fuel valve <NUM>. A main bore <NUM> extends from said inlet port <NUM> into the nozzle body and into the cylindrical portion <NUM> in a direction along a main axis X to a position close to the distal end <NUM> of the nozzle body. The main bore <NUM> connects to a plurality of individual supply passages <NUM> that are each connected to a nozzle bore <NUM>. The individual supply passages <NUM> are arranged at an angle to the axis of the straight main bore <NUM> and to the axis of the straight nozzle bore <NUM> to which the individual supply passage <NUM> concerned connects.

The cross-sectional area of the main bore <NUM> is substantially larger than the total cross-sectional area of the supply passages <NUM>. The total cross-sectional area of the supply passages <NUM> is substantially equal to the total cross-sectional area of the nozzle bores <NUM>.

The use of individual supply passages <NUM> to connect the nozzle bores <NUM> to the main bore <NUM> allows for the nozzle bores <NUM> to be placed anointed in such a way that maximizes the amount of nozzle body material between them, whilst still having the axis I,II,III,IV, and V of the nozzle bores <NUM> to cover the desired circle sector with the fuel jets.

The inlet port <NUM> is in an embodiment formed by a bore with a diameter that is larger than the diameter of the main bore <NUM>. Alternatively, the inlet port <NUM> can have the same diameter as the main bore.

The nozzle <NUM> provides a wide spread of nozzle bores <NUM>, and thus more nozzle material between the nozzle bores <NUM> and thus better resistance against crack formation. Further, the nozzle <NUM> provides uniform inlet conditions to each of the nozzle bores <NUM>, for creating substantially uniform fuel jets.

The valve needle <NUM> comprises a distal section that comprises a cylindrical end section <NUM> carried by a shank <NUM>. The cylindrical end section <NUM> is journaled with a tight fit in the straight main bore <NUM> to fluidically disconnect the individual supply passages <NUM> from the main straight bore (<NUM>) when the valve needle <NUM> is in the closed position as shown in <FIG>,<FIG> and <FIG>, since the cylindrical end section <NUM> covers the opening of the individual supply passages <NUM> towards said straight main bore <NUM> when the valve needle <NUM> is in the closed position. Thus, any fuel in the space between the valve seat <NUM> and the distal end of the main bore <NUM> is prevented from leaking into the combustion chamber <NUM> when the valve needle <NUM> is in the closed position.

The cylindrical end section <NUM> is hollow to form a fluid passage <NUM> for the fuel from the proximal side of the cylindrical end section <NUM> to the distal side of the cylindrical end section <NUM>. The fluid passage <NUM> opens proximally to the exterior of the shank <NUM> and the fluid passage <NUM> opens distally in an axial direction.

The cylindrical end section <NUM> fluidically connects the individual supply passages <NUM> to the main straight bore <NUM> when the valve needle <NUM> is in the open position, as shown in <FIG>, by the cylindrical end section <NUM> not covering the opening of the individual supply passages <NUM> towards said straight main bore <NUM>.

The individual supply passages <NUM> open to said main bore at a given axial distance from said inlet <NUM>, and the cylindrical end section <NUM> extends past the given axial distance in the closed position of the valve needle <NUM> to obstruct the flow of fuel to the individual supply passages <NUM>.

In an embodiment, the individual supply passage <NUM> are, seen from the position where the individual supply passage <NUM> concerned connects to the main bore <NUM>, directed away from the longitudinal axis X at a first angle with the longitudinal axis X, resulting in the "base" of the of the straight nozzle <NUM> bores being placed more radially outward, thereby allowing for more distance between neighboring straight nozzle bores <NUM> and thus more nozzle body material between neighboring straight nozzle bores <NUM>. In this context, the "base" position is where a straight nozzle bore <NUM> connects to an individual supply passage <NUM>.

In an embodiment, the straight nozzle bore <NUM>, seen from the position where the nozzle bore <NUM> concerned connects to the individual supply passage <NUM>, is directed away from the longitudinal axis X at a second angle with the longitudinal axis X, the second angle being greater than the first angle.

According to a possible implementation form of the first aspect, the individual supply passages <NUM> are straight bores, preferably with a rounded, i.e. spherical extremity (a or near the "base") to reduce stress in the nozzle bore material.

Claim 1:
A fuel valve (<NUM>) for injection of liquid fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads, said fuel valve (<NUM>) comprising:
an elongated fuel valve housing (<NUM>) with a longitudinal axis (X), a proximal end (<NUM>), and a distal end (<NUM>),
an axially displaceable valve needle (<NUM>), said valve needle (<NUM>) having a closed position resting on a valve seat (<NUM>) and an open position where the valve needle (<NUM>) has lift from the valve seat (<NUM>), and
a nozzle (<NUM>) disposed at the distal end (<NUM>) of said elongated fuel valve housing (<NUM>),
said nozzle (<NUM>) having a nozzle body extending along said longitudinal axis (X) from a base (<NUM>) at a proximal end (<NUM>) of said nozzle body to a closed distal end (<NUM>) of said nozzle body, said base (<NUM>) being attached to said fuel valve housing (<NUM>),
said nozzle body comprising:
an elongated portion, preferably a cylindrical portion, extending between said base (<NUM>) and said closed distal end (<NUM>),
an inlet (<NUM>) opening to said base (<NUM>) for receiving liquid fuel from said fuel housing valve (<NUM>),
a plurality of straight nozzle bores (<NUM>), each straight nozzle bore (<NUM>) opening to the outer surface of the nozzle body at a different radial angle,
a single straight main bore (<NUM>) extending longitudinally from said inlet (<NUM>) into said nozzle body,
characterized in that
at least three of said straight nozzle bores (<NUM>) being connected to said straight main bore (<NUM>) by an individual supply passage (<NUM>) that is arranged at an angle to said straight main bore (<NUM>) and to the straight nozzle bore (<NUM>) concerned,
the valve needle (<NUM>) comprising a distal section with a cylindrical end section (<NUM>) carried by a shank (<NUM>) and which is journaled with a tight fit in the straight main bore (<NUM>) in order to fluidically disconnect the individual supply passages (<NUM>) from the main straight bore (<NUM>) when the valve needle (<NUM>) is in the closed position.