EP3267027A1 - Nozzle head for a fuel injection valve of a large diesel engine, and method for manufacturing same - Google Patents

Abstract

A nozzle head is proposed for a fuel injector of a large diesel engine, particularly a longitudinally-scavenged two-stroke large diesel engine, having a longitudinal passage (2) to which fuel can be supplied and extending in an axial direction (A) from an upper end (21) to a lower end (22) and with at least one nozzle channel (4) extending from the longitudinal channel (2) to a nozzle opening (3) through which the fuel is introduced into a combustion chamber of the large diesel engine, each nozzle channel ( 4) has a flow area smaller than the flow area of the longitudinal channel (2), and the lower end (22) of the longitudinal channel (2) being located above the axial direction (A) and above the normal use position above each nozzle opening (3) is. Furthermore, a method for producing such a nozzle head (1) is proposed.

Description

The invention relates to a nozzle head for a fuel injector of a large diesel engine, in particular a longitudinally-flushed two-stroke large diesel engine, and a method for producing such a nozzle head according to the preamble of the independent claim of the respective category.

Large diesel engines, such as longitudinally purged two-stroke large diesel engines, are often used as power units for ships or even in stationary operation, e.g. used to drive large generators for generating electrical energy. The engines usually run for long periods in continuous operation, which places high demands on the reliability and availability. Therefore, for the operator in particular long maintenance intervals, low wear and an economical handling of the operating materials are central criteria.

For some years, the quality of the exhaust gases, in particular the nitrogen oxide concentration in the exhaust gases, has become an increasingly important aspect with increasing importance. This has in particular in two-stroke large diesel engines with the result that the combustion of the classic, highly polluted with pollutants heavy fuel, but also the combustion of diesel oil or other fuels is problematic, because compliance with the exhaust emission limits increasingly difficult, technically complex and therefore more expensive or at the end of their compliance is no longer meaningful possible.

In practice, therefore, has long been the need for so-called "dual-fuel engines", ie engines that can be operated with two different fuels. In a gas mode, a gas, e.g. a natural gas such as LNG (liquefied natural gas), or a gas in the form of an autogas or other suitable for driving an internal combustion engine gas burned, while in a liquid mode, a suitable liquid fuel such as diesel or heavy oil can be burned in the same engine.

In the context of this application, the term "large diesel engine" also refers to those large engines which, except in diesel mode, which is characterized by the self-ignition of the fuel, also in an Otto mode, which is characterized by the spark ignition of the fuel, or in mixed forms of these two can be operated. In addition, the term "large diesel engine" also includes, in particular, the aforementioned dual-fuel engines and those large engines in which the self-ignition of the fuel is used for the spark ignition of another fuel.

In liquid mode, the fuel is usually introduced directly into the combustion chamber of the cylinder and burns there according to the principle of auto-ignition. In the gas mode, it is known to mix the gas in the gaseous state with the purging air according to the Otto principle, so as to produce an ignitable mixture in the combustion chamber of the cylinder. In this low or high pressure method, the ignition of the mixture in the cylinder is usually done by a small amount of liquid fuel is injected at the right moment in the combustion chamber of the cylinder or in an antechamber, which then leads to the ignition of the air-gas mixture. A dual-fuel engine can be switched from gas mode to liquid mode during operation, and vice versa.

If a large diesel engine is operated with liquid fuel, that is to say, for example, heavy oil or diesel oil, fuel injection nozzles are usually used for introducing the fuel into the combustion chamber of the cylinder, which have a nozzle body and a nozzle head. The nozzle head is also referred to as an atomizer. In the nozzle head a plurality of nozzle openings are usually provided, through which the fuel is injected into the combustion chamber. In order to start or end the injection process, a movable nozzle needle is provided in the fuel injector, which cooperates with a valve seat such that the passage to the nozzle openings is opened or closed.

Typically, the nozzle head is a wear part, which is subject to a high thermal, mechanical and chemical stress collective. Among other things, the mechanical loads are based on the high injection pressure, which can amount to more than a thousand bar. The thermal stresses are caused by the high temperatures in the combustion chamber and the enormous temperature changes between combustion temperature and temperature of the freshly supplied scavenging air, while the chemical stresses are mainly due to the high-temperature or hot corrosion.

For these reasons, and in particular due to the thermal load, the valve seat is usually arranged slightly away from the nozzle openings, so that an excessive exposure to heat of combustion is avoided. Downstream of the valve seat in the nozzle head designed as a blind hole longitudinal bore is provided, branch off from which holes that lead to the nozzle openings.

The spatial distance between valve seat and nozzle openings brings with it the following problem. Upon termination of the fuel injection, the nozzle needle is pressed into the valve seat, so that the fuel, which is located downstream of the valve seat - ie between the valve seat and nozzle holes - in the blind hole, is no longer supplied with the feed pressure. This part of the fuel can be undesirable Lead deposits in the nozzle head and after completion of the injection through the nozzle openings poorly atomized enter the combustion chamber, or drip into it, where it but little or no burn. This leads to an increased fuel consumption, to additional pollution of the exhaust gas, in particular with oxides of oxides NO _x , as well as to deposits of unburned fuel in all parts of the combustion chamber and the exhaust gas-carrying components.

To solve this problem, various proposals have already been made. For example, it is known to provide a shut-off element on the nozzle needle downstream of the valve seat, which prevents the flow of fuel through the nozzle openings as soon as the nozzle needle is pressed into the valve seat. Even if such refinements have proven to be useful, they are relatively complex in terms of apparatus and therefore cost-intensive.

Based on this prior art, it is therefore an object of the invention to provide a simple nozzle head for a fuel injector of a large diesel engine, which can be at least significantly reduce the problems mentioned, which are caused by the fuel, the downstream of the injection still downstream the valve seat is present. Furthermore, it is an object of the invention to propose a method for producing such a nozzle head.

The objects of the invention solving this object are characterized by the features of the independent claim of the respective category.

According to the invention, therefore, a nozzle head is proposed for a fuel injector of a large diesel engine, in particular a longitudinally flushed two-stroke large diesel engine, with a longitudinal channel to which a fuel can be supplied, and which extends in an axial direction from an upper end to a lower end, and at least a nozzle channel which extends from the longitudinal channel to a nozzle opening through which the fuel into a combustion chamber of the Large diesel engine can be introduced, wherein each nozzle channel has a flow cross-section which is smaller than the flow cross-section of the longitudinal channel, and wherein the lower end of the longitudinal channel with respect to the axial direction and with respect to the normal position of use is arranged above each nozzle opening.

This configuration of the nozzle head, in which the longitudinal channel does not extend over substantially the entire length of the nozzle head in the axial direction, but already ends above each nozzle opening, the volume between the valve seat and the nozzle openings can be drastically reduced compared to known nozzle heads. In conjunction with the smaller flow cross section of the at least one nozzle channel, thus resulting in a much smaller amount of fuel, which is located after completion of the injection process, so when the nozzle needle again sealingly cooperates with the valve seat, downstream of the valve seat in the nozzle head. Consequently, after completion of the injection process downstream of the valve seat only a considerably smaller amount of fuel in the nozzle head is present, so that the negative effects caused by this fuel - especially the harmful emissions, fuel consumption and harmful deposits, are significantly reduced. Since no equipment-consuming measures are necessary for this, such a nozzle head is also particularly simple in its design.

According to the invention, a method is also proposed for producing a nozzle head according to the invention, in which the nozzle head is produced by means of an additive machining method.

With an additive processing method or with an additive manufacturing, which is also referred to as generative manufacturing, thereby a processing method is meant in which material is applied or applied. Usually, in an additive processing method of an informal material, such as liquids or powders, or of a form-neutral material, such as ribbon or wire-shaped material, the desired structures are generated by chemical and / or physical processes, eg. B. by building on a body. Well-known additive manufacturing methods for metallic materials are, for example, deposition welding processes, especially inert gas processes such as tungsten inert gas welding (TIG) or laser deposition welding, or plasma processes or selective laser melting (SLM) or laser sintering.

Compared to subtractive processing or manufacturing processes, in which material is removed or removed from a workpiece or a blank, additive processing methods are subject to at least almost no geometric restrictions, so that arbitrarily structured bodies, in particular those with internal cavities, can be produced. By way of example, subtractive processes include all forms of machining production, which means, as is generally customary, a production in which excess material in the form of chips is separated from a blank or a workpiece in order to achieve a desired geometric shape. Machining operations include, for example, milling, turning, drilling, planing, filing, grinding, honing or lapping, to name but a few examples.

Since, according to the invention, the nozzle head is produced by means of an additive machining method, its concrete geometrical configuration is subject to virtually no limits.

According to one embodiment, the entire nozzle head is manufactured by the additive machining method, that is, the entire nozzle head is constructed generatively.

According to a preferred embodiment, the additive machining method produces an insert in which all the nozzle channels are arranged, and the insert is inserted into a longitudinal bore of the nozzle head, which extends in the axial direction, and which longitudinal bore comprises the longitudinal channel.

It is preferred that the insert is designed so that it with its entire outer boundary surface on the longitudinal bore abuts limiting wall, so the longitudinal bore with respect to the radial direction so completely fills. Preferably, the insert has a cylindrical shape, wherein its outer diameter substantially corresponds to the inner diameter of the longitudinal bore, so that the insert can be inserted into the longitudinal bore and rests with its outer boundary surface on the wall which limits the longitudinal bore with respect to the radial direction.

Each nozzle channel is designed as an inner channel, which is located completely inside the insert. This means that each nozzle channel is completely enclosed by the insert, so that only the insert itself limits each nozzle channel. In particular, this avoids that other components such as the wall, which limits the longitudinal bore, forms a boundary for the nozzle channel.

This embodiment has the advantage that not only the nozzle channels in virtually any geometry can be produced, but that the use of the nozzle channels in the longitudinal bore or in the blind hole of a known conventional nozzle head can be used to a novel nozzle head realize. This embodiment thus also makes it possible, in particular, to reshape an existing conventional nozzle head into an inventive device. For this purpose, it may be necessary to extend the longitudinal bore or the blind hole in the conventional nozzle head, so that the additively manufactured insert can be used with the nozzle channels in this longitudinal bore.

The insert is preferably made so that it rests over its entire circumference on the inner wall of the longitudinal bore, so that the fuel from the longitudinal channel can pass substantially only through the nozzle channel or the nozzle channels into the combustion chamber.

The additive machining method has, as already mentioned, in particular the advantage that the nozzle channel or the nozzle channels can be made with any geometry / can. Thus, it is possible to produce each nozzle channel in free, arbitrary form, and thus for the to optimize the respective application. As a result, cavitations can be at least reduced and a trouble-free, optimal flow pattern for the fuel can be realized. Even deposits in the nozzle head can be significantly reduced at least.

Another advantage of the embodiment with the insert is that it can be made of a different material than the rest of the nozzle head. Since the use is not exposed to the extremely challenging environmental conditions in the combustion chamber itself, a material can be selected for it, which is selected from aspects such as cost optimization and the best possible passage of the fuel, while selected for the rest of the nozzle head another proven material which is particularly advantageous in terms of the conditions in the combustion chamber.

With regard to the apparatus aspects, it is preferred if the nozzle head has a plurality of nozzle channels, each of which extends in each case from the longitudinal channel to a nozzle opening, through which the fuel can be introduced into the combustion chamber of the large diesel engine. By this measure, a particularly favorable distribution of the fuel in the combustion chamber of the cylinder can be ensured.

According to a preferred embodiment, the nozzle head has a longitudinal bore which extends in the axial direction, wherein the longitudinal bore comprises the longitudinal channel, and wherein in the longitudinal bore an insert is provided, in which all the nozzle channels are arranged. As already explained in connection with the method according to the invention, this embodiment has several advantages. The insert with the at least one nozzle channel is inserted into the longitudinal bore of the nozzle head, so that with respect to the normal position of use upper part of the longitudinal bore of the nozzle head forms the longitudinal channel, followed by the downstream of the insert with the at least one nozzle channel, through which the fuel from the Longitudinal channel can enter the combustion chamber.

It is preferred for the reasons already mentioned, if the insert is made of a material that is different from the material, from which is the rest of the nozzle head. In the wall of the nozzle head then one or more holes are provided which form the nozzle openings through which the fuel can pass from the respective nozzle channel into the combustion chamber.

With regard to the best possible distribution of the fuel in the combustion chamber, it is preferred if each nozzle channel is designed so that the fuel at an injection angle inclined to the axial direction can escape from the respective nozzle opening, each injection angle less than 90 ° and preferably less than 80 ° is. With the injection angle is meant the smaller of the two angles, which includes the surface normal of the nozzle opening with the axial direction.

In order to ensure the best possible fuel injection, it is preferred if at least two nozzle channels are provided which have different injection angles.

Another preferred measure is when each nozzle channel is designed so that it opens in the axial direction in the longitudinal channel. By this measure, the flow resistance for the fuel at the transition from the longitudinal channel can be minimized in each nozzle channel, because each nozzle channel in the vicinity of the longitudinal channel extends in the same direction as the longitudinal channel, so that the fuel is not deflected in the transition from the longitudinal channel in the nozzle channel must become. As a result, in particular erosion-related degradation effects can be avoided.

Depending on the application, it may also be advantageous if at least one nozzle channel is widening or tapering in a region adjoining the nozzle opening. As a result, the flow behavior of the fuel can be optimized.

In particular, it is advantageous if each nozzle channel is designed free of edges and corners, because this can at least significantly reduce deposits, erosion phenomena and cavitations, the Usually increased on sharp edges or corners can occur and lead to increased wear.

A further preferred embodiment is that the at least one nozzle channel is designed arcuate or curved. Due to the arcuate or curved configuration, the flow of the fuel can be transferred particularly lossless and advantageous from the axial direction in the desired injection direction.

It is also advantageous if at least two nozzle channels are provided, which have a curved region, wherein the curvatures of the two nozzle channels are different in the curved region. This configuration makes it possible to realize particularly different injection angles for the fuel, with cavitations and erosion-related wear phenomena being at least significantly reduced.

The invention further proposes a large diesel engine, in particular a longitudinally purged two-stroke large diesel engine, with a fuel injection nozzle which comprises a nozzle head which is designed according to the invention or produced according to a method according to the invention.

Further advantageous measures and embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

einen Längsschnitt durch eine Brennstoffeinspritzdüse eines Grossdieselmotors gemäss Stand der Technik,

Fig. 2:

eine schematische Längsschnittdarstellung des Düsenkopfs der Brennstoffeinspritzdüse aus Fig. 1, und

Fig. 3:

einen schematische Längsschnittdarstellung eines Ausführungsbeispiels eines erfindungsgemässen Düsenkopfs.

In the following the invention will be explained in more detail by means of embodiments and with reference to the drawing. In the drawing show:

Fig. 1:

a longitudinal section through a fuel injector of a large diesel engine according to the prior art,

Fig. 2:

a schematic longitudinal sectional view of the nozzle head of the fuel injector Fig. 1 , and

3:

a schematic longitudinal sectional view of an embodiment of an inventive nozzle head.

In the context of the present application, relative position designations, such as "below", "above", "below", "above", etc., are to be understood as referring in each case to the normal position of use.

For a better understanding of the invention is first based on the Fig. 1 the structure of a fuel injector of a large diesel engine explained, as it is known in the prior art. For better distinction of the prior art of the present invention are used for the device known from the prior art reference numerals, which are provided with an apostrophe.

Fig. 1 shows a longitudinal section through a known from the prior art fuel injector of a large diesel engine, which is generally designated by the reference numeral 10 '. In particular, it is the fuel injector 10 'of a longitudinally purged two-stroke large diesel engine, with which a liquid fuel, in particular heavy oil or diesel oil, can be introduced into a combustion chamber 20' of a cylinder of the large diesel engine.

The known fuel injection nozzle 10 'comprises a nozzle body 11' with a nozzle head 1 ', which is connected to the nozzle body 11'. The connection takes place here by means of a holding sleeve 12 ', which tapers at its lower end according to the illustration to the longitudinal axis of the fuel injector 10' out. Through the longitudinal axis of the fuel injector 10 ', which is also the longitudinal axis of the nozzle head 1' at the same time, an axial direction A 'is set. The retaining sleeve 12 'is by means of a union nut 13' and an elastic member 14 ', for example a snap ring, attached to the nozzle body 11'. The nozzle head 1 'is supported in the tapered part of the retaining sleeve 12'.

For a better understanding shows Fig. 2 still a schematic longitudinal sectional view of the nozzle head 1 'of the fuel injector 10' from Fig. 1 .

The nozzle head 1 'has a longitudinal bore 5' and in the region of its lower end at least one nozzle opening 3 ', typically several z. B. five nozzle openings 3 ', which are connected to the longitudinal bore 5', so that the fuel through the nozzle openings 3 'in the combustion chamber 20' can escape.

In the interior of the nozzle body 11 'is a pressure chamber 14' is provided, in which a feed line 15 'opens for the fuel. Through the supply line 15 ', the high-pressure fuel from a reservoir, usually an accumulator of a common rail system, the fuel injector 10' are supplied. The pressure chamber 14 'is bounded in the axial direction A' by a valve seat 16 '. Further, in the interior of the nozzle body 11 ', a nozzle needle 17' is arranged, which extends substantially in the axial direction A ', and which cooperates with the valve seat 16'. In the in Fig. 1 shown closed position, the lower tip of the nozzle needle 17 'is pressed into the valve seat 16', so that the passage from the pressure chamber 14 'in the downstream adjoining longitudinal bore 5' is closed. The nozzle needle 17 'is spring-loaded by means of a compression spring, not shown, and biased against the valve seat 16'. In the open position of the nozzle needle 17 'is this darstellungsgemäss up from the valve seat 16' lifted so that between the lower end of the nozzle needle 17 'and the valve seat 16', a passage is open, through which the fuel from the pressure chamber 14 'in the longitudinal bore 5 'can get.

The volume of the longitudinal bore 5 'downstream of the valve seat 16' is commonly referred to as a blind hole or blind hole volume.

The longitudinal bore 5 'is configured in the example described here as a substantially cylindrical bore which extends in the axial direction A' and has a length L '(see Fig. 2 ). The diameter D 'of the longitudinal bore 5' defines a flow cross section, which means the available for the flow of the fuel cross-sectional area in the longitudinal bore 5 'is meant.

The nozzle needle 17 'is arranged in a bore 18' of the nozzle body 11 'extending in the axial direction A', which in FIG Fig. 1 for reasons of space only partially shown. The bore 18 'has an inner diameter B', which is slightly larger than an outer diameter of the nozzle needle 17 ', so that the nozzle needle 17' safely and precisely in the bore 18 'is guided.

As in particular the schematic representation in Fig. 2 shows, each nozzle opening 3 'via a nozzle channel 53' with the longitudinal bore 5 'of the nozzle head 1' is connected, so that the pressurized fuel from the longitudinal bore 5 'through the nozzle channels 53' and the nozzle openings 3 'injected into the combustion chamber 20' becomes. The flow cross section of each nozzle channel 53 'is significantly smaller, in particular at least five times smaller than the flow cross section of the longitudinal bore 5', which is defined by the diameter D 'of the longitudinal bore. Usually, the nozzle channels 53 'each extend inclined or oblique to the axial direction A', so that the fuel at an injection angle α 'inclined to the axial direction A' from the respective nozzle opening 3 'can escape. With the injection angle α 'is meant the smaller of the two angles, which includes the surface normal of the nozzle opening 3' with the axial direction. Of course, the respective injection angles α 'may be different for different nozzle openings 3'.

Fig. 3 shows a schematic longitudinal sectional view of an embodiment of an inventive nozzle head, which is generally designated by the reference numeral 1. The nozzle head 1 is in an analogous manner as that of Fig. 1 has been described for a fuel injector of a large diesel engine, in particular a longitudinally purged two-stroke large diesel engine, determined and acts in an analogous manner as described above with a nozzle body of the fuel injector together.

The nozzle head 1 has a longitudinal channel 2 which extends in an axial direction A from an upper end 21 to a lower end 22 and has the length L1. The longitudinal channel 2 is preferably cylindrical in shape and has a diameter D. In an analogous manner, as with reference to Fig. 1 has been explained, the axial direction A through the Longitudinal axis of the nozzle head 1 is fixed, which is identical to the longitudinal axis of the fuel injector when the nozzle head 1 is mounted in the fuel injector. In a similar manner as in the prior art, the longitudinal channel 2, a fuel can be supplied, which is to be introduced into a combustion chamber of a cylinder of the large diesel engine.

The nozzle head 1 further has at least one nozzle channel 4, which extends from the longitudinal channel 2 to a nozzle opening 3, through which the fuel is introduced into the combustion chamber of the cylinder. Usually, the nozzle head 1 comprises a plurality of separate nozzle openings 3, each of which is then connected in each case by a nozzle channel 4 with the longitudinal channel 2. In the schematic representation in Fig. 3 two nozzle openings 3 are shown, which are in each case flow-connected via a nozzle channel 4 with the longitudinal channel 2.

Each nozzle channel 4 in this case has a flow cross section which is significantly smaller, for example at least five times smaller than the flow cross section of the longitudinal channel 2. The flow cross section in this case means in each case the surface which is perpendicular to the main flow direction of the fuel.

According to the invention, the lower end 22 of the longitudinal channel 2 with respect to the axial direction and with respect to in Fig. 3 shown normal use position above each nozzle opening 3 arranged. As a result of this measure, the volume which is available to the fuel in the nozzle head can be drastically reduced, so that only a significantly smaller amount of fuel is present in the nozzle head 1 after the end of the injection.

The nozzle head 1 is manufactured by means of an additive machining method. These processing or manufacturing processes are also referred to as generative processes or as additive manufacturing. By an additive processing method or with an additive manufacturing, a method is meant in which material is applied or applied in order to build up the corresponding body. Usually, in an additive machining process, from an informal material, For example, liquids or powders, or from a shape-neutral material, such as ribbon or wire-shaped material, generated by chemical and / or physical processes, the desired structures, eg. B. by building on a body. Well-known additive manufacturing methods for metallic materials are, for example, deposition welding processes, especially inert gas processes such as tungsten inert gas welding (TIG) or laser deposition welding, or plasma processes or selective laser melting (SLM) or laser sintering.

The additive or generative production has the particular advantage that they are subject to virtually no geometric restrictions, so that in particular bodies with arbitrarily shaped inner cavities can be produced. With regard to the nozzle channel 4 or the nozzle channels 4, this has the considerable advantage that each nozzle channel 4 can be produced with virtually any desired geometry. Thus, the respective geometry of the nozzle channel 4 can be optimized under various aspects, for example, under the aspects cavitations at least significantly reduce erosion degradation as far as possible to avoid deposits in the nozzle channel 4, to optimize the flow behavior of the fuel, or to realize an optimal atomization or distribution of the fuel in the combustion chamber.

At the in Fig. 3 illustrated, preferred embodiment, an insert 6 is provided, which is arranged in a longitudinal bore 5 of the nozzle head 1, which extends in the axial direction A over a length L which is greater than the length L1 of the longitudinal channel 2 in the axial direction A. This insert 6 contains all nozzle channels 4 and fills the representation according to the lower end of the longitudinal bore 5 over a length L2 completely. This means, in particular, that the insert 6 fully rests against the inner wall of the longitudinal bore 5.

Each nozzle channel 4 is designed as an inner channel, which is located completely inside the insert 6. Each nozzle channel 4 is thus laterally bounded in full by the insert 6. This is to be understood in particular as meaning that the nozzle channel 4 or the nozzle channels 4 are not in the Surface of the insert 6 is arranged, which limits the insert 6 in the radial direction, but just inside the insert 6. Only the mouths of the nozzle channels 4 on the one hand in the nozzle openings 3 and on the other hand in the longitudinal channel 2 are in the surface of the insert 6th

The insert 6 with the nozzle channels 4 is manufactured with an additive processing method.

Preferably, a per se known nozzle head can be used for the production of the nozzle head 1, as he, for example, in Fig. 2 is shown. In the wall 7 of the nozzle head 1, which limits the longitudinal bore 5, at least one bore is provided which forms the nozzle opening 3. In Fig. 3 two such nozzle openings 3 are shown. These nozzle openings 3 are preferably identical to the nozzle openings of the known nozzle head 1 'in FIG Fig. 2 is shown. The insert 6 is then introduced into the longitudinal bore 5 or into the longitudinal bore 5 'of the known nozzle head 1' until it rests against the lower end of the longitudinal bore 5 or 5 '. Thus, the lower region of the longitudinal bore 5 or 5 'is preferably completely filled with the insert 6 over the length L2, and the upper region of the longitudinal bore 5 or 5' forms the longitudinal channel 2, which has the length L1. L1 and L2 complement each other to the length L of the longitudinal bore. 5

If a nozzle head 1 'known per se is used for the production of the nozzle head 1, it may be advantageous, depending on the application, to change the original diameter D' (FIG. Fig. 2 ) of the longitudinal bore 5 'by drilling or any other suitable machining process to increase, so as to produce the longitudinal bore 5 with the diameter D, in which then the insert 6 is used.

It is understood that in the production of the insert 6, the outlet openings of all nozzle channels 4 are arranged so that they are aligned after placing the insert 6 in the longitudinal bore 5 each with one of the nozzle openings 3 in the wall 7 of the nozzle head 1.

The measure of producing the nozzle head 1 on the basis of a nozzle head 1 'which is known per se has several advantages. Thus, the outer design of the nozzle head 1, which in particular the arrangement and the design of the nozzle openings 3 is meant to be taken over by a known nozzle head. Furthermore, the nozzle head 1 can be easily inserted into an existing fuel nozzle without the need for structural changes or adjustments. It is also possible to convert or retrofit an already existing nozzle head into a nozzle head 1 according to the invention by inserting into the longitudinal bore 5 'of the existing nozzle head 1', possibly after an enlargement of the diameter D 'of the original longitudinal bore 5'.

Another advantage of the embodiment with the insert 6 is that it can be made of a different material than the rest of the nozzle head 1, so for example its wall 7. This makes it possible for the production of the nozzle head 1 - with the exception of the insert 6 - to use a proven material that is particularly suitable in view of the extremely demanding conditions in the combustion chamber, for example, the enormous thermal loads. Such materials known per se for the production of a nozzle head 1 of a large diesel engine are, for example, steels or alloys based on nickel or cobalt, for example stellite 6. These materials are particularly suitable with regard to erosion, abrasion and cavitation especially in the nozzle openings 3.

For the production of the insert 6 then another material, preferably a metallic material can be chosen because the insert 6 is not exposed even to the extreme conditions in the combustion chamber, but is protected by the wall 7 of the nozzle head 1. So you have now a much higher flexibility in the selection of a suitable material with which the insert 6 of the nozzle head 1 is built in additive manufacturing. The material for the insert 6 can be selected, for example, in terms of cost or optimum management of the fuel.

A particular advantage of the inventive design of the nozzle head 1 is that the respective flow connection between the longitudinal channel 2 and the nozzle opening 3, so the respective nozzle channel 4, can be designed freeform, that is in particular subjected to practically no geometric constraints. Thus, each nozzle channel 4 can be designed with regard to an optimal flow behavior of the fuel or with regard to an optimal guidance of the fuel. Thus, each nozzle channel 4 can be optimized in particular also with regard to cavitations, erosion, abrasion and the most efficient possible introduction of the fuel into the combustion chamber.

In the following, some preferred measures and variants for the design of the respective nozzle channel 4 are explained in a non-exhaustive list.

Preferably, each nozzle channel 4 is designed such that the fuel is inclined at an injection angle α Fig. 3 to the axial direction A can escape from the respective nozzle opening 3. By the injection angle α is meant the smaller of the two angles, which encloses the surface normal of the nozzle opening 3 with the axial direction. Of course, the respective injection angles α may be different from each other for different nozzle openings 3. Each injection angle α is preferably less than 90 ° and preferably less than 80 °. A particularly preferred value range is 70 ° to 75 °.

Also, it is advantageous, though not mandatory, that, as in Fig. 3 represented, each nozzle channel 4 is designed so that it opens in the axial direction A in the longitudinal channel 2. This makes it possible to realize a particularly good transition of the fuel from the longitudinal channel 2 into the respective nozzle channel 4.

It may also be advantageous that the nozzle channel 4 is widening or tapering in particular in a region adjacent to the nozzle opening 3. By this measure, the atomization of the fuel in the combustion chamber can be improved.

In particular, it is preferred as well as in Fig. 3 is shown, when each nozzle channel 4 is designed free of edges and corners. Since edges and corners in the flow are particularly high risk of unwanted cavitation and erosion, such edges and corners are preferably avoided. Therefore, it is advantageous if the nozzle channel 4 as in Fig. 3 is designed arcuate or curved, so that the fuel can be as optimally deflected from the axial direction A in the desired direction of injection.

It is also particularly advantageous if at least two nozzle channels 4 are provided, which have a curved portion, wherein the curvatures of the two nozzle channels 4 are different in the curved region. This is in Fig. 3 indicated by the two arrows with the reference numerals r ₁ and r ₂ .

According to another embodiment of the invention, the entire nozzle head is manufactured by means of an additive machining process. In this embodiment, therefore, no insert 6 is provided, but the nozzle head 1 is constructed overall in additive or additive manufacturing. Otherwise, the preceding explanations apply analogously to the same manner for the embodiment without insert 6.

Claims (15)

Nozzle head for a fuel injection nozzle of a large diesel engine, in particular a longitudinally flushed two-stroke large diesel engine, having a longitudinal channel (2) to which a fuel can be fed and which extends in an axial direction (A) from an upper end (21) to a lower end (A). 22), and with at least one nozzle channel (4) which extends from the longitudinal channel (2) to a nozzle opening (3) through which the fuel is introduced into a combustion chamber of the large diesel engine, each nozzle channel (4) has a flow cross-section which is smaller than the flow cross-section of the longitudinal channel (2), characterized in that the lower end (22) of the longitudinal channel (2) with respect to the axial direction (A) and with respect to the normal position of use above each nozzle opening (3) is arranged. Nozzle head according to claim 1, having a plurality of nozzle channels (4), each of which extends from the longitudinal channel (2) to a nozzle opening (3) through which the fuel can be introduced into the combustion chamber of the large diesel engine. Nozzle head according to one of the preceding claims, having a longitudinal bore (5) which extends in the axial direction, the longitudinal bore (5) comprising the longitudinal channel (2), and wherein an insert (6) is provided in the longitudinal bore (5), in which all the nozzle channels (4) are arranged. Nozzle head according to claim 3, wherein the insert (6) is made of a material which is different from the material of which the remainder of the nozzle head (1) consists. Nozzle head according to one of the preceding claims, in which each nozzle channel (4) is designed such that the fuel can emerge from the respective nozzle opening (3) at an injection angle (α) inclined to the axial direction (A), each injection angle (α) is less than 90 ° and preferably less than 80 °. Nozzle head according to claim 5, wherein at least two nozzle channels (4) are provided which have different injection angles (α). Nozzle head according to one of the preceding claims, wherein each nozzle channel (4) is designed such that it opens in the axial direction (A) in the longitudinal channel (2). Nozzle head according to one of the preceding claims, wherein at least one nozzle channel (4) is widening or tapering in a region adjoining the nozzle opening (3). Nozzle head according to one of the preceding claims, wherein each nozzle channel (4) is designed free of edges and corners. Nozzle head according to one of the preceding claims, wherein the at least one nozzle channel (4) is designed arcuate or curved. Nozzle head according to one of the preceding claims, wherein at least two nozzle channels (4) are provided which have a curved region, wherein the curvatures (r ₁ , r ₂ ) of the two nozzle channels (4) are different in the curved region. Method for producing a nozzle head according to one of the preceding claims, characterized in that the nozzle head (1) is produced by means of an additive machining method. A method according to claim 12, wherein the entire nozzle head (1) is manufactured by the additive machining method. The method of claim 12, wherein the additive machining process, an insert (6) is prepared in which all the nozzle channels (4) are arranged, and wherein the insert (6) in a Longitudinal bore (5) of the nozzle head (1) is inserted, which extends in the axial direction (A), and which longitudinal bore (5) comprises the longitudinal channel (2). Large diesel engine, in particular longitudinally purged two-stroke large diesel engine, with a fuel injection nozzle, which comprises a nozzle head (1), which is designed according to one of claims 1-11, or which is produced according to one of claims 12-14.

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