Patent Description:
A hydrogen injector for a hydrogen engine is typically run at critical conditions at which the hydrogen flow becomes sonic or even locally supersonic. One problem with this type of flow is difficulties to maintain the initial direction of the jet out of the injector nozzle.

One commonly used hydrogen nozzle is a so called pintle-valve nozzle. An angle of the upper part of the pintle valve surface is a design-parameter which may determine the outgoing direction of the jet. In order to further control the outgoing direction of the jet, a pintle-valve can be combined with a nozzle cap. The cap comprises one or several holes and the configuration of the holes is often used to determine the direction of the outgoing jet. For example, <CIT> and <CIT> disclose hydrogen nozzles comprising nozzle caps.

A particular problem with a hydrogen nozzle is that the nozzle cap hole exit area needs to be larger than conventional engine nozzles. This means that a major part of the nozzle cap side and bottom sides are open holes. It is therefore difficult to design the holes to direct the jets in a wanted direction, especially at sonic or even locally supersonic hydrogen flow. Further, this may lead to disturbing vortices in the cap volume. Such disturbing vortices may re-direct part of the flow in an un-favourable direction. Furthermore, the cap-volume as such may contain residual hydrogen-containing gases that may auto-ignite at an un-favourable timing.

Accordingly, there is room for improvements with regards to hydrogen flow guidance in hydrogen nozzles.

An object of the invention is to provide a nozzle cap for fuel injection nozzle that at least partly alleviates the deficiencies with the prior art.

According to a first aspect of the invention, the object is achieved by a nozzle cap according to claim <NUM>.

According to the first aspect of the invention, there is provided a nozzle cap for a fuel injection nozzle operable in a hydrogen internal combustion engine. The nozzle cap comprising an inlet for receiving a flow of hydrogen controllable by an inlet valve arrangeable in the inlet. At least one outlet for providing an exit flow of hydrogen, and an internal bottom flow-guiding body arranged at a bottom side of the nozzle cap downstream of the inlet in a nozzle cap volume. The internal bottom flow-guiding body comprises a convex ridge protruding towards the inlet and comprises a flow-guiding surface for re-directing a flow of hydrogen from the inlet towards the outlet. The convex ridge is centralized in the bottom of the nozzle cap and is arranged to reach from side-to-side across the entire nozzle cap volume.

The present invention is based on the realization that to minimize circular flow in the nozzle cap the internal structures and surfaces of the nozzle cap can be modified to lead the flow of hydrogen towards the outlet of the nozzle cap with reduced vortices in the inner volume of the nozzle cap. One advantageous inner structure is the internal bottom flow-guiding body which defines a flow-guiding surface that is in contact with the stream of hydrogen gas. This internal bottom flow-guiding body advantageously leads the hydrogen gas towards the outlet while at the same time reducing the dead-volume in the cap which reduces the amount of residual hydrogen that can remain in the nozzle cap.

Thus, by the provision of the herein proposed nozzle cap the hydrogen stream is guided towards the outlet such that hydrogen injection for the hydrogen internal combustion engine can be efficiently performed.

The inlet valve arrangeable in the inlet of the nozzle cap may for example be a pintle valve that are per se known in the art, although other types or valves are conceivable.

The outlet of the nozzle cap directs the hydrogen stream into, or towards a combustion chamber of the hydrogen internal combustion engine.

In one embodiment, the outlet may comprise a first exit surface and a second exit surface forming the outlet, wherein the shape of the first exit surface substantially follows the shape of the second exit surface, such that the exit flow of hydrogen from the outlet at the first exit surface is in substantially the same direction as the exit flow of hydrogen at the second exit surface. Thus, the surfaces of the outlet are adapted to further improve the guidance of the hydrogen stream. The exits surfaces are in this way intentionally shaped to control the exit direction of the hydrogen flow. The first and second exit surfaces may be considered hole-edge surfaces of the outlet. That the exit flow is in substantially the same direction should be interpreted as that the main flow is in the same direction or near the same direction where a small deviation is allowed.

In one embodiment, the nozzle cap may further comprise at least a first internal side flow-guiding body arranged at a side-wall surface of the nozzle cap and protruding inwards in a nozzle cap volume, for guiding the flow of hydrogen towards the at least one outlet. Hereby, guiding of the hydrogen flow is even further improved. The at least one internal side flow-guiding body provides at least one additional flow-guiding surface that contributes to reducing vortices in the nozzle cap volume by assisting in leading the hydrogen flow towards the outlet. The first internal side flow-guiding body cooperates with the internal bottom flow-guiding body to lead the hydrogen flow towards the outlet.

In one embodiment, the outlet may comprise a first exit surface and a second exit surface forming the outlet, wherein the shape of the at least one first internal side flow-guiding body substantially follows a shape of the flow-guiding surface of the internal bottom flow-guiding body, such that the exit flow of hydrogen from the outlet at the first exit surface is in substantially the same direction as the exit flow of hydrogen at the second exit surface. That the exit flow is in substantially the same direction should be interpreted as that the main flow is in the same direction or near the same direction where a small deviation is allowed. Hereby, the first internal side flow-guiding body and the internal flow-guiding body advantageously cooperates to better guide the hydrogen stream towards the outlet.

The shape of the outlet along the flow direction may be that the first and second exit surfaces are parallel. However, other outlet shapes or configurations are possible. For example, in one embodiment, the outlet comprises a first exit surface and a second exit surface forming the outlet, wherein the first exit surface and a second exit surface together form a conical outlet.

In one embodiment, the outlet may comprise a first exit surface and a second exit surface, wherein the flow-guiding surface of the internal bottom flow-guiding body is arranged next to the second exit surface, the flow-guiding surface and the second exit surface are configured to co-operatively direct the exit flow of hydrogen at the second exit surface in the same direction as the exit flow of hydrogen at the first exit surface. Hereby, the nozzle cap is further improved to guide the hydrogen flow towards the outlet. That the internal bottom flow-guiding body is arranged next to the second exit surface means that they are directly neighbouring, i.e. being adjacent to each other. The flow-guiding surface of the internal bottom flow-guiding body and the second exit surface may form a single seamless flow-guiding surface.

In one embodiment, the internal bottom flow-guiding body may be configured to redirect a flow of hydrogen towards to two opposite sides of the nozzle cap. The opposite sides may be on two sides of a centre axis of the nozzle cap. This is advantageous if, for example, the nozzle cap comprises outlets on the two opposite sides.

In one embodiment, the nozzle cap may comprise two outlets arranged on opposite sides of the internal bottom flow-guiding body, wherein the internal flow-guiding bodies are configured to redirect a flow of hydrogen from the inlet towards the two outlets.

In embodiments, the internal bottom flow-guiding body may be centralized in the bottom of the nozzle cap.

In other embodiments, the internal bottom flow-guiding body may be arranged off-set from a centre of the bottom of the nozzle cap.

Different offsets and locations of the internal bottom flow-guiding body are advantageous depending on specific implementations at hand. For example, an offset arrangement may be used in some implementations, e.g. with only one outlet to reduce flow to a side not having an outlet. A centralized location may be advantageous when it is desirable to direct equal amount so flow to the different sides of the nozzle cap.

In one embodiment, the internal bottom flow-guiding body may be shaped to substantially fill the side of the nozzle cap opposite the outlet. Hereby, the dead-volume in the nozzle cap is advantageously reduced which leads to reduced amount of residual hydrogen that can remain in the nozzle cap.

In one embodiment, the number of outlets is more than two, wherein the internal bottom flow-guiding body comprising a set of flow-guiding surfaces for re-directing a flow of hydrogen towards each of the outlets. Thus, the internal bottom flow-guiding body may advantageously be designed in correspondence with the number of outlets, still providing improved flow of hydrogen through the nozzle cap.

The nozzle cap may have different outer shapes depending on the implementations at hand.

For example, in one embodiment, the internal bottom flow-guiding body may have a convex outer shape.

In another embodiment, the internal bottom flow-guiding body may have a concave outer shape.

In one embodiment, the internal bottom flow-guiding body comprises flow-guiding elements protruding from the upper ridge of the internal bottom flow-guiding body for further providing further adjustments of the hydrogen-flow in the nozzle cap. Hereby, the nozzle cap is further improved to guide the hydrogen flow towards the outlet.

According to a second aspect of the invention, there is provided a fuel injection nozzle comprising an inlet valve and a nozzle cap according to any one of the herein disclosed embodiments.

Effects and features of the second aspect of the invention are largely analogous to those described above in connection with the first aspect.

According to a third aspect of the invention, there is provided a hydrogen internal combustion engine comprising a fuel injection nozzle according to the second aspect.

According to a fourth aspect of the invention, there is provided a vehicle comprising a fuel injection nozzle according to the second aspect or a hydrogen internal combustion engine according to the third aspect.

Effects and features of the third and fourth, aspects are largely analogous to those described above in relation to the first aspect and the second aspect.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

<FIG> illustrates a vehicle in the form of a truck <NUM> comprising an engine <NUM> such as for example an internal combustion engine. The internal combustion engine is a hydrogen engine. The truck <NUM> may be a hybrid electric vehicle. The hydrogen internal combustion engine <NUM> of truck <NUM> further comprises a fuel injection nozzle with a nozzle cap as disclosed herein.

<FIG> is a perspective cross-sectional view of a nozzle cap <NUM> for a fuel injection nozzle <NUM> that, when in use, is operable in a hydrogen internal combustion engine <NUM>. <FIG> is a cross-section of the nozzle cap <NUM> and valve shown in <FIG>. The nozzle cap <NUM> comprises an inlet <NUM> for receiving a flow of hydrogen. The flow of hydrogen is provided from storage of hydrogen that is typically pressurised. The flow of hydrogen through the inlet <NUM> is controllable by an inlet valve <NUM> arrangeable in the inlet <NUM>. When the pintle <NUM> of the valve <NUM> is in an upper position, the inlet <NUM> is closed and hydrogen is not allowed to enter the nozzle cap volume <NUM>. In the lower position shown in <FIG>, the inlet <NUM> is open and hydrogen is allowed to enter the nozzle cap volume <NUM>.

The nozzle cap <NUM> further comprises at least one outlet <NUM> for providing an exit flow of hydrogen. An internal bottom flow-guiding body <NUM> is arranged at a bottom side <NUM> of the nozzle cap <NUM> downstream of the inlet <NUM> in the nozzle cap volume <NUM>, e.g. opposite the inlet <NUM>. The internal bottom flow-guiding body <NUM> is shaped to protrude towards the inlet <NUM> and comprises a flow-guiding surface <NUM> for re-directing a flow of hydrogen received from the inlet <NUM> towards the outlet <NUM>.

The hydrogen flow enters through the inlet <NUM> and is initially guided by the flow-guiding surface <NUM> of the valve <NUM> and the valve seat <NUM> before it enters the nozzle cap volume <NUM>. If the internal bottom flow-guiding body <NUM> was not present, vortices are created inside the cap and suboptimal flow of hydrogen towards the outlet <NUM> is obtained. However, as provided by embodiments herein, the internal bottom flow-guiding body <NUM> provides improved hydrogen flow guidance towards the outlet <NUM>.

The internal bottom flow-guiding body <NUM> extends along an axis <NUM> from the bottom side <NUM> towards the side of the inlet <NUM>. The flow-guiding surface <NUM> of the internal bottom flow-guiding body <NUM> ensures that the flow of hydrogen follows its shape and is guided towards the outlet <NUM>.

The internal bottom flow-guiding body <NUM> extends relatively close to the valve <NUM> which advantageously reduces cross-flow of hydrogen across the centre <NUM> of the internal bottom flow-guiding body <NUM> and here also the nozzle cap <NUM> which further improves the guidance of the hydrogen flow. Further, the size of the internal bottom flow-guiding body <NUM> is relatively large so that to fill-up a large portion of the nozzle cap volume <NUM>. This reduces the risk for residual hydrogen to remain in the nozzle cap volume <NUM>. Generally, the larger the size the better, however the size should not compromise the ability for the internal bottom flow-guiding body <NUM> to guide the hydrogen flow towards the outlet <NUM>. In <FIG>, the internal bottom flow-guiding body is centralized in the nozzle cap <NUM>.

Further, a flow-guiding surface <NUM> adjacent to the valve seat <NUM> is shaped to guide flow towards the outlet <NUM>. The flow-guiding surface <NUM> is adjacent to the valve seat <NUM> so that a continuous flow-guiding surface is formed from the flow-guiding surface <NUM> and the valve seat <NUM>.

The surfaces <NUM> and <NUM> cooperate to aerodynamically guide the flow towards the outlet <NUM>. For example, the outlet <NUM> comprises a first exit surface <NUM> and a second exit surface <NUM> forming the outlet <NUM>. These surfaces <NUM> and <NUM> are the hole edges of the outlet <NUM>. In order to provide an efficient flow through the outlet <NUM>, the shape of the first, upper exit surface <NUM>, substantially follows the shape of the second, lower exit surface <NUM>. In this way, the exit flow of hydrogen from the outlet <NUM> at the first exit surface <NUM> is in substantially the same direction as the exit flow of hydrogen at the second exit surface <NUM>. Thus, the shape of the flow-guiding surface <NUM> and the exit surfaces <NUM> and <NUM> may be different depending on the relative locations of the outlet <NUM> and the inlet <NUM> but are adapted to guide the hydrogen flow towards the outlet <NUM>. In <FIG>, the internal bottom flow-guiding body <NUM> has a convex outer shape, thus forming a convex ridge in the nozzle cap. The cross-sectional shape of the flow-guiding surface <NUM> of the internal bottom flow-guiding body <NUM> and the second exit surface <NUM> may be curved in two directions resembling an S-shape.

The valve seat <NUM>, the flow-guiding surface <NUM>, and the first exit surface <NUM> preferably form a continuous, smooth, flow-guiding surface. Similarly, the flow-guiding surface <NUM> and the second exit surface <NUM> preferably form a continuous, smooth, flow-guiding surface. The flow-guiding surface <NUM> of the cap wall <NUM> and the flow-guiding surface <NUM> of the bottom flow-guiding body are smoothly connected through the hole edge surfaces <NUM> and <NUM>.

It is also conceivable that the first exit surface and a second exit surface forming the outlet together form a conical outlet.

The flow-guiding surface <NUM> of the internal bottom flow-guiding body <NUM> is arranged next to the second exit surface <NUM>. Preferably, the flow-guiding surface <NUM> and the second exit surface form a seamless flow-guiding surface extending along the internal bottom flow-guiding body <NUM> all the way to the outlet <NUM>. The flow-guiding surface <NUM> and the second exit surface <NUM> are configured to co-operatively direct the exit flow of hydrogen at the second exit surface in the same direction as the exit flow of hydrogen at the first exit surface <NUM>.

<FIG> conceptually illustrates a comparative example not covered by the claims. This embodiment may be primarily intended for a single-hole cap with a main hole-direction presenting a certain angle related to the injector centre axis direction. The nozzle cap <NUM> illustrated in <FIG> differs from that shown in <FIG> in that the internal bottom flow-guiding body <NUM> is shaped to substantially fill the side <NUM> of the nozzle cap opposite the outlet <NUM>. In other words, instead of leaving an open volume on the side of the internal bottom flow-guiding body <NUM> where there is no outlet, the internal bottom flow-guiding body <NUM> fills up that volume. This significantly reduces the amount of residual hydrogen that can remain in the nozzle cap <NUM>.

The number of outlets of the nozzle cap may be more than one. Turning to <FIG>, there is shown a nozzle cap <NUM> having two outlets 108a-b. <FIG> is a perspective cross-sectional view of the nozzle cap <NUM> and <FIG> is a cross-section of the nozzle cap <NUM>. The internal bottom flow-guiding body <NUM> is configured to redirect a flow of hydrogen towards to two opposite sides of the nozzle cap <NUM>, where the two outlets are located. Thus, the internal bottom flow-guiding body <NUM> comprises two opposite flow-guiding surfaces 112a-b. A first flow-guiding surface 112a is configured to guide hydrogen flow towards a first outlet 108a and second flow-guiding surface 112b is configured to guide hydrogen flow towards a second outlet 108b.

<FIG> conceptually illustrates a further embodiment of a nozzle cap. Here, the nozzle cap <NUM> comprises an internal bottom flow-guiding body <NUM> as discussed above with reference to preceding drawings, and two outlets 508a-b. Further, the nozzle cap <NUM> comprises at least a first internal side flow-guiding body <NUM> arranged at a side-wall <NUM> of the nozzle cap <NUM> and protruding inwards in a nozzle cap volume <NUM>, for guiding the flow of hydrogen towards the outlets 508a-b. Thus, the internal bodies <NUM> and <NUM> defines outer surfaces 510a-b, and 521a-b that are in contact with the hydrogen flow and that are cooperatively configured to lead the flow of hydrogen towards the outlets to reduce vortices in the cap volume <NUM>.

The first internal side flow-guiding body <NUM> is shaped with a convex outer surface to allow for receiving the flow form the inlet and guide the flow over surface of the guiding the flow along the internal flow-guiding body <NUM>, with assistance from the oppositely arranged internal bottom flow-guiding body <NUM> with respect to the outlets 508a-b.

Preferably, a shape of a surface portion <NUM> of the at least one first internal side flow-guiding body 521a-b substantially follows a shape of the flow-guiding surface 510a-b of the internal bottom flow-guiding body, such that the exit flow of hydrogen from the outlet at a first exit surface 512a and 512b is in substantially the same direction as the exit flow of hydrogen at a second exit surface 514a and 514b, respectively. Preferably, the shape of the surface portion 525b of the internal side flow-guiding body 521b adjacent to the second exit surface 514b is substantially similar to the shape of the internal bottom flow-guiding body <NUM> in surface portions opposite the surface portion 525b. Similarly, at the other outlet 108a, the shape of the surface portion 525a of the internal side flow-guiding body 521a adjacent to the second exit surface 514a is substantially similar to the shape of the internal bottom flow-guiding body <NUM> in surface portions opposite the surface portion 525a.

Generally, the internal flow-guiding bodies <NUM>, 521a-b are configured to redirect a flow of hydrogen from the inlet towards the two outlets 508a-b.

In case the number of outlets is more than two, the internal bottom flow-guiding body comprising a set of flow-guiding surfaces for re-directing a flow of hydrogen towards each of the outlets.

For each of the embodiments discussed with respect to <FIG>, and <FIG>, is advantageous to have the internal bottom flow-guiding body to be shaped to fill-out the volume between two outlets in the nozzle cap volume. Thus, the internal bottom flow-guiding body reaches across the entire inner volume of the nozzle cap, from side-to-side, but leaves the openings open. Further, the internal bottom flow-guiding body <NUM>, <NUM> is centralized in the bottom of the nozzle cap.

<FIG> conceptually illustrates different configurations for internal bottom flow-guiding bodies. In <FIG>example height curves and shapes of the internal bottom flow-guiding bodies are illustrated. However, these are only examples, and variations are possible and within the scope of the present invention. The shape of the internal bottom flow-guiding bodies is generally configured to assist the flow of hydrogen to efficiently reach the outlet of the nozzle cap in a preferred direction.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> according to the claims and having a convex outer shape. Thus, the flow-guiding surfaces <NUM> have a convex shape and are configured to direct flow of hydrogen from the inlet to the outlet as described herein.

Here, the flow-guiding surfaces <NUM> have a relatively shallow slope. Further, at side portions <NUM> a passage is formed between the internal bottom flow-guiding body <NUM> and the inlet valve pintle (not shown in <FIG>). The axis <NUM> indicates the centre of the nozzle cap, thus, the internal bottom flow-guiding body <NUM> is here indicated as centralized in the nozzle cap.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> according to the claims and having a convex outer shape but with a narrower side-ways extension compare to the internal bottom flow-guiding body <NUM> shown in <FIG>. The internal bottom flow-guiding body <NUM> is configured as barrier type structures that allows minimal cross-flow between the sides of the internal bottom flow-guiding body <NUM>.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> not covered by the claims, having a convex outer shape similar to the internal bottom flow-guiding body <NUM> shown in <FIG>. However, the convex ridge of the internal bottom flow-guiding body <NUM> is arranged off-set from a centre <NUM> of the bottom of the nozzle cap. Thus, the internal bottom flow-guiding body <NUM> is located such that more of the hydrogen stream is directed towards a first side <NUM> of the internal bottom flow-guiding body <NUM> than towards a second side <NUM>. In other words, the off-centre location of the internal bottom flow-guiding body <NUM> favours direction the hydrogen flow towards the first side <NUM>.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> according to the claims and having a convex outer shape. A difference between the internal bottom flow-guiding body <NUM> and the internal bottom flow-guiding body <NUM> is that the slopes of the flow-guiding surfaces <NUM> are steeper than the flow-guiding surfaces <NUM> of the internal bottom flow-guiding body <NUM>. The steeper slope leads to a smaller passage <NUM> which advantageously reduces the cross-flow at across the centre <NUM> of the nozzle cap.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> not covered by the claims, adapted to fill out one side of the nozzle cap opposite the outlet. Thus, on one side of the internal bottom flow-guiding body <NUM> there is a flow-guiding surface <NUM> adapted to guide a flow of hydrogen towards an outlet. The other side of the internal bottom flow-guiding body <NUM> fills out the volume of the nozzle cap on that side. Thus, very little flow is directed towards the fill out side of the nozzle cap.

<FIG> is a top view <NUM> and a side view <NUM> of an internal bottom flow-guiding body <NUM> not covered by the claims, having a concave outer shape. The flow-guiding surfaces <NUM> having a concave shape are advantageous for directing the flow of hydrogen towards the centre of the outlets <NUM>, in other words, the concave shape of the flow-guiding surfaces <NUM> provides for converging the flow towards the centre of the outlets <NUM>.

<FIG> conceptually illustrates a perspective cross-section of a nozzle cap <NUM> according to embodiments of the invention. Here, the internal bottom flow-guiding body <NUM> comprises a flow-guiding element <NUM> protruding from the upper ridge <NUM> of the internal bottom flow-guiding body <NUM>. This provides for adjusting of the hydrogen-flow in the nozzle cap towards preferred directions. The flow-guiding element <NUM> is specifically adapted to guide the minor flow going from the valve-seat in the region between the nozzle cap outlets 108a,b such that the flow in this location between the outlets is better directed towards the outlets 108a,b. The flow-guiding element <NUM> is thus designed to redirect downwards going flow reaching the bottom flow-guiding body <NUM> at locations between the outlets 108a, 108b.

Although other possibilities are conceivable, the nozzle caps are preferably made of steel.

Claim 1:
A nozzle cap (<NUM>) for a fuel injection nozzle operable in a hydrogen internal combustion engine (<NUM>), the nozzle cap comprising:
an inlet (<NUM>) for receiving a flow of hydrogen controllable by an inlet valve (<NUM>) arrangeable in the inlet,
at least one outlet (<NUM>) for providing an exit flow of hydrogen, and
an internal bottom flow-guiding body (<NUM>) arranged at a bottom side (<NUM>) of the nozzle cap downstream of the inlet in a nozzle cap volume (<NUM>), the internal bottom flow-guiding body comprising a convex ridge protruding towards the inlet and comprises a flow-guiding surface (<NUM>) for re-directing a flow of hydrogen from the inlet towards the outlet,
characterized in that
the convex ridge is centralized in the bottom of the nozzle cap and is arranged to reach from side-to-side across the entire nozzle cap volume (<NUM>).