DE102019209756A1 - Nozzle assembly for a fuel injector, fuel injector - Google Patents

Abstract

The invention relates to a nozzle assembly (1) for a fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber (2) of an internal combustion engine, comprising two coaxially arranged nozzle needles (3, 4) which are liftably received in a nozzle body (5) wherein first spray holes (6) arranged in a circle for forming gas jets (8) and circularly arranged second spray holes (7) for forming ignition jets (9) are formed in the nozzle body (5). According to the invention, the number of second spray holes (7) for forming the ignition jets (9) is smaller than the number of first spray holes (6) for forming the gas jets (8). The invention also relates to a fuel injector with such a nozzle assembly (1)

Description

The invention relates to a nozzle assembly for a fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber of an internal combustion engine. The invention also relates to a fuel injector with such a nozzle assembly.

The main gaseous fuel can in particular be natural gas (“natural gas” for short). The liquid ignition fuel can in particular be diesel fuel.

State of the art

In the so-called NGDI injection process ("Natural Gas Direct Injection"), natural gas is injected directly into a combustion chamber of an internal combustion engine, ignited by means of a previously set diesel pilot injection and then burned diffusively. Compared to conventional diesel combustion, the combustion of natural gas has the particular advantage that CO ₂ emissions can be reduced by up to 25%. Natural gas has diesel-like combustion and therefore torque characteristics, so that the degree of integration into existing diesel drive systems is high. This means that generally only minor changes to the internal combustion engine, cooling system and / or exhaust gas aftertreatment system are required. The NGDI injection process is used, for example, in commercial vehicles, especially heavy-duty commercial vehicles. Diesel fuel is usually used as the ignition fuel, the systems usually being designed in such a way that the internal combustion engine can also only be operated with diesel fuel when required (“diesel-only” operation).

So-called dual-fuel injectors are known for injecting different fuels into the combustion chamber of the internal combustion engine, which have two coaxially arranged nozzle needles which are guided into one another and which control different injection holes. The outer nozzle needle controls the first injection holes through which the main gaseous fuel can be injected. The inner nozzle needle controls second injection holes through which the liquid ignition fuel can be injected. A well-known dual fuel injector is exemplified in the DE 10 2014 225 167 A1 disclosed.

In an internal combustion engine that is operated with a gaseous main fuel and a liquid ignition fuel, the gas-energy ratio (GER, "Gas-Energy-Ratio") describes the ratio of the energy content of the gaseous main fuel to the total energy content of both fuels. The information is given in percent. In order to meet the legal requirements for a gas engine, the GER value must be over 90%.

The present invention is based on the object of optimizing the injection of a gaseous main fuel and a liquid ignition fuel in such a way that the legally required GER value is reliably maintained across all operating points of the internal combustion engine.

To achieve the object, the nozzle assembly with the features of claim 1 is proposed. Advantageous further developments of the invention can be found in the subclaims. Furthermore, a fuel injector with a nozzle assembly according to the invention is specified.

Disclosure of the invention

The proposal is for a nozzle assembly for a fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber of an internal combustion engine. The nozzle assembly comprises two coaxially arranged nozzle needles which are reciprocally received in a nozzle body. First spray holes arranged in a circle for forming gas jets and second spray holes arranged in a circle for forming ignition jets are formed in the nozzle body. According to the invention, the number of second spray holes for forming the ignition jets is smaller than the number of first spray holes for shaping the gas jets.

A pilot jet is usually assigned to each gas jet, so that the gas jet is reliably ignited and the gas is burned as completely as possible. This assumes that there are first and second injection holes in the same number. In the case of the nozzle assembly according to the invention, the number of second injection holes or injection holes for the liquid ignition fuel is less than the number of first injection holes through which the main gaseous fuel is introduced into the combustion chamber. As a result, less ignition fuel gets into the combustion chamber of the internal combustion engine, which leads to a favorable GER value. In particular, a GER value> 90% can be safely adhered to.

The number of the first spray holes or the spray holes for the gaseous main fuel preferably corresponds to n times the number of the second spray holes or the spray holes for the liquid ignition fuel. This means that the number of the first spray holes is a multiple of the number of the second spray holes. In this way, the GER score can be further improved. In particular, a GER value> 90% can also be achieved when the internal combustion engine is operating at part load. The problem in partial load operation is that the Ignition quantity remains the same while the injection quantity of the main gaseous fuel decreases. This has a negative effect on the GER value, so that the legally required value may not be complied with. With the aid of the nozzle assembly according to the invention, the legally required GER value can also be achieved in partial load operation, where n is preferably a number between 2 and 9. This means that the number of the first spray holes is at least twice as high as the number of the second spray holes.

It is also proposed that the first spray holes and / or the second spray holes are each arranged at the same angular distance from one another. This means that the circularly arranged first spray holes and / or the circularly arranged second spray holes are evenly distributed over the circumference of the nozzle body. This arrangement of the spray holes leads to a uniform distribution of the gas jets and / or the ignition jets in the combustion chamber or to better utilization of the combustion chamber.

The second spray holes are advantageously arranged offset with respect to their angular position with respect to the first spray holes. In particular, a second spray hole can be arranged centrally between two first spray holes. The pilot jet formed with the aid of this spray hole can then be used to ignite the gas jets of the spray holes arranged on both sides. This means that a pilot jet can be assigned to two gas jets, so that reliable ignition and burning is guaranteed.

If the second spray holes are each arranged centrally between two first spray holes, it is not necessary for a second spray hole to be arranged between each two first spray holes. This means that the second spray holes can also be arranged at different angular distances from one another. Furthermore, the number of first spray holes does not necessarily have to be n times the number of second spray holes. In this way, the number of spray holes for the liquid ignition fuel can be further reduced.

In addition, more than two gas jets can be assigned to a pilot jet. For example, a pilot jet can be assigned a group of gas jets, at least one of which is ignited directly with the aid of the pilot jet and the others indirectly, specifically with the aid of the already ignited pilot jet. In this way, a cascaded ignition of the gas jets can be brought about, which enables a further reduction in the number of spray holes for the liquid ignition fuel. With cascaded ignition, the indirectly ignited gas jets ignite later than the directly ignited gas jets. This has the positive side effect that the gas burns through more slowly and is associated with less noise.

If a group of gas jets is assigned to a pilot jet, these can be generated by injection holes for the main gaseous fuel that belong to different injection hole circles. The gas jets of the spray hole circle, which is closer to the spray holes for the liquid ignition fuel, can then be ignited directly and the others indirectly. A cascaded ignition of the gas jets can also be effected in this way.

In a further development of the invention, it is therefore proposed that the first injection holes or the injection holes for the main gaseous fuel be arranged in a plurality of circles lying one above the other. In this way, the GER value can be significantly improved again.

The second spray holes or the spray holes for the liquid ignition fuel are preferably arranged in a circle which is spaced axially from the at least one circle of the first spray holes or the spray holes for the main gaseous fuel. The second spray holes are advantageously closer to a tip of the nozzle body in the axial direction than the first spray holes. The greater distance between the first spray holes and the tip of the nozzle body enables the number of first spray holes per spray hole circle to be maximized. Because with increasing distance from the tip, the diameter of the nozzle body also increases, so that more space is available for the formation of injection holes. This is also of advantage because usually and preferably also in the case of the nozzle assembly according to the invention, the first spray holes have a larger diameter than the second spray holes.

It is further proposed that the longitudinal axes A _{S1 of} the first spray holes and the longitudinal axis A _{D of} the nozzle body each enclose an angle α ₁ and the longitudinal axes A _{S2 of} the second spray holes and the longitudinal axis A _{D of} the nozzle body each enclose an angle α ₂ , preferably the Angle α _{2 is} equal to or greater than angle α ₁ . If the two angles α ₁ and α _{2 are} equal, the longitudinal axes A _S1 and A _S2 run parallel to one another at different heights. Since the gas jets and ignition jets usually form jet cones, they meet in the combustion chamber so that at least some of the gas jets can be ignited directly with the aid of the ignition jets. The ignition point is usually outside on the cone of a gas jet, on the side facing the pilot jet. If the angle α _{2 is selected to be} greater than the angle α ₁ , the ignition jet hits the gas jet earlier or the ignition location moves into Direction of the nozzle body. The lower penetration depth of the pilot jet leads to combustion of the main gaseous fuel close to the nozzle and thus slow and at the same time low-noise.

The first spray holes and / or the second spray holes preferably have an inlet fillet. The inlet rounding of the first spray holes promotes an accumulation of the gas jets so that there is no undesired break. The gas jets are therefore more stable. The radius of the rounding of an inlet rounding of the first and / or second spray holes is preferably smaller than the respective spray hole diameter.

In addition, a fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber of an internal combustion engine is proposed which comprises a nozzle assembly according to the invention. The same advantages described above in connection with the nozzle assembly can be achieved with the aid of the fuel injector. In particular, the fuel injector makes it easier to comply with the legally required GER value when burning the main gaseous fuel.

In order to inject a gaseous main fuel and a liquid ignition fuel into a combustion chamber of an internal combustion engine, the fuel injector is preferably designed as a dual fuel injector, furthermore preferably as an NGDI injector.

• 1 einen schematischen Längsschnitt durch eine erfindungsgemäße Düsenbaugruppe gemäß einer ersten bevorzugten Ausführungsform der Erfindung im Bereich der Spritzlöcher,
• 2 eine schematische Darstellung des Spritzbilds der Düsenbaugruppe der 1,
• 3 einen schematischen Längsschnitt durch eine erfindungsgemäße Düsenbaugruppe gemäß einer zweiten bevorzugten Ausführungsform der Erfindung im Bereich der Spritzlöcher,
• 4 eine schematische Darstellung des Spritzbilds der Düsenbaugruppe der 3,
• 5 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer dritten bevorzugten Ausführungsform der Erfindung,
• 6 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer vierten bevorzugten Ausführungsform der Erfindung,
• 7 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer fünften bevorzugten Ausführungsform der Erfindung,
• 8 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer sechsten bevorzugten Ausführungsform der Erfindung,
• 9 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer siebten bevorzugten Ausführungsform der Erfindung, und
• 10 eine schematische Darstellung eines Spritzbilds einer erfindungsgemäßen Düsenbaugruppe gemäß einer achten bevorzugten Ausführungsform der Erfindung.

Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:

• 1 a schematic longitudinal section through a nozzle assembly according to the invention according to a first preferred embodiment of the invention in the area of the spray holes,
• 2 a schematic representation of the spray pattern of the nozzle assembly of FIG 1 ,
• 3 a schematic longitudinal section through a nozzle assembly according to the invention according to a second preferred embodiment of the invention in the area of the spray holes,
• 4th a schematic representation of the spray pattern of the nozzle assembly of FIG 3 ,
• 5 a schematic representation of a spray pattern of a nozzle assembly according to the invention according to a third preferred embodiment of the invention,
• 6th a schematic representation of a spray pattern of a nozzle assembly according to the invention according to a fourth preferred embodiment of the invention,
• 7th a schematic representation of a spray pattern of a nozzle assembly according to the invention according to a fifth preferred embodiment of the invention,
• 8th a schematic representation of a spray pattern of a nozzle assembly according to the invention according to a sixth preferred embodiment of the invention,
• 9 a schematic representation of a spray pattern of a nozzle assembly according to the invention according to a seventh preferred embodiment of the invention, and
• 10 a schematic representation of a spray pattern of a nozzle assembly according to the invention according to an eighth preferred embodiment of the invention.

Detailed description of the drawings

The ones in the 1 nozzle assembly shown 1 belongs to a fuel injector, with the help of which a gaseous main fuel and a liquid ignition fuel are fed into a combustion chamber 2 an internal combustion engine can be injected. For this purpose, it comprises two coaxially arranged nozzle needles 3 , 4th that are in a nozzle body 5 are lifted. The nozzle body 5 forms the first spray holes 6th for the main gaseous fuel and second spray holes 7th for the liquid ignition fuel, the first and second injection holes 6th , 7th - At an axial distance from one another - are each arranged in a circle. The first spray holes 6th are further away from a point in the axial direction 11 of the nozzle body 5 arranged and with the help of the lifting outer nozzle needle 3 controllable. The second spray holes 7th are via the inner nozzle needle 4th controlled. With the help of the first spray holes 6th are conical gas jets 8th malleable. With the help of the second spray holes 7th are conical ignition beams 9 malleable.

Like the spray pattern of the 2 can be seen, forms the nozzle assembly 1 the 1 eight gas jets 8th and four pilot jets 9 which are each arranged at the same angular distance from one another. Under every second gas jet 8th there is a pilot jet 9 . That means that the pilot jet 9 the overlying gas jet 8th ignites and this then the two adjacent gas jets 8th (see arrows). The gas jet ignited first 8th is therefore from below (see 1 ) ignited. The two adjacent gas jets 8th are ignited from the side (see 2 ).

The 3 is a nozzle assembly 1 according to a second preferred embodiment of the invention. In contrast to the nozzle assembly 1 the 1 assign the second Injection holes 7th a different position and orientation in relation to the first injection holes 6th on.

Like the spray pattern of the 4th it can be seen that there are eight gas jets 8th with the help of four pilot jets 9 ignited. The second spray holes 7th for shaping the pilot beams 9 However, their angular position is offset from the first injection holes 6th arranged so that the second spray holes 7th each between two first injection holes 6th come to rest. The second spray holes 7th also have longitudinal axes A _S2 , which are common to a longitudinal axis A _{D of} the nozzle body 5 enclose an angle α ₂ which is greater than an angle α ₁ between the longitudinal axis A _D and a longitudinal axis A _{S1 of} the first injection holes 6th is. In the embodiment of 1 and 2 the two angles α ₁ and α _{2 were} equal. The changed alignment of the pilot beams 9 has the consequence that this the gas jets 8th earlier, that is, closer to the nozzle body 5 cross. Would the detonators 9 right under the gas jets 8th the gas jets would lie 8th in an ignition location 13th ignited, the closer to the nozzle body 5 lies. In the embodiment of 3 and 4th the ignition does not take place from below, but from the side, so that the ignition location 13th essentially changed its altitude. That is, the pilot beams 9 and the gas jets 8th burn at about the same height.

The following figures are further preferred embodiments of a nozzle assembly according to the invention 1 which are described using their respective spray patterns.

The spray pattern of the 5 belongs to a nozzle assembly 1 with seven first injection holes 6th or fuel holes 6th for the main gaseous fuel and three second injection holes 7th or injection holes 7th for the liquid ignition fuel. The three second injection holes 7th are each exactly below a first spray hole 6th arranged so that thereover formed gas jets 8th with the help of the ignition beams below 9 can be ignited directly. The inflamed gas jets 8th then ignite the neighboring gas jets 8th (see arrows). The indirect ignition of the gas jets 8th via already inflamed gas jets 8th enables a further reduction in the number of second spray holes 7th . There are not exactly half as many second injection holes 7th like the first spray holes 6th provided, but also one less.

The spray pattern of the 6th belongs to a nozzle assembly 1 with seven first injection holes 6th and four second injection holes 7th . The number of second spray holes 7th is therefore half the number of the first injection holes 6th an additional spray hole 7th .

The embodiments with the spray patterns of 5 and 6th have in common that the second spray holes 7th are not arranged at the same angular distance from one another. The number of the first spray holes 6th also does not correspond to n times the number of second injection holes 7th , as is the case with the embodiments of 1 and 2 as well as 3 and 4 was the case.

The same principle is also applied to a nozzle assembly 1 applicable, their second injection holes 7th offset in their angular position to the first injection holes 6th are arranged. This embodiment is exemplified in FIG 7th shown. On seven gas jets 8th there are also four pilot jets 9 , with the gas jets 8th - due to the offset angular position of the spray holes - not ignited from below, but from the side.

The ignition quantity can be further reduced if each pilot jet 9 more than two gas jets 8th be assigned. Corresponding embodiments are the 8th to 10 refer to. Here is every pilot 9 a group 12th of gas jets 8th assigned, which can be arranged next to and / or one above the other. At least one gas jet 8th a group 12th is directly via the pilot jet 9 ignited. The at least one inflamed gas jet 8th then ignites the neighboring gas jets 8th on and so on. In this way the gas jets 8th cascaded ignited.

The spray pattern of the 8th shows a division of the gas jets 8th in groups 12th of three gas jets each 8th . As can be seen in the small picture above, there are three first injection holes for this 6th arranged above and next to each other. The pilot jet below 9 ignites the first gas jet 8th and this the two overlying gas jets 8th .

The spray pattern of the 9 also shows a division of the gas jets 8th in groups 12th of three gas jets each 8th . As can be seen in the small picture above, here are the first three injection holes 6th arranged exclusively next to each other. The pilot jet located in the middle 9 ignites the middle gas jet 8th and this the two adjacent gas jets 8th .

The spray pattern of the 10 shows a division of the gas jets 8th in groups 12th of nine gas jets each 8th . As can be seen in the small picture above, there are two rows of first injection holes 6th arranged one above the other, one row four and the other row five first injection holes 6th includes. The pilot jet below 9 ignites the gas jet closest to it 8th or the gas jets closest to it 8th , this one or these the respectively adjacent gas jets 8th next to and above.

Indirect ignition via already ignited gas jets 8th has the advantage that the ignition quantity can be significantly reduced, which has a positive effect on the GER value. In addition, a time delay is created that contributes to slow, low-noise combustion. The first and / or the second injection holes can or can provide support 6th , 7th an inlet fillet 10 have, as for example in the 1 and 3 shown. The inlet fillet 10 acts to tear off the gas jet 8th or the pilot jet 9 opposite.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102014225167 A1 [0004]

Claims (10)

Nozzle assembly (1) for a fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber (2) of an internal combustion engine, comprising two coaxially arranged nozzle needles (3, 4) which are reciprocally accommodated in a nozzle body (5), the nozzle body (5) first spray holes (6) arranged in a circle for forming gas jets (8) and second spray holes (7) arranged in a circle for forming ignition jets (9) are formed, characterized in that the number of second spray holes (7) for forming the Ignition jets (9) is smaller than the number of first spray holes (6) for forming the gas jets (8). Nozzle assembly (1) Claim 1 , characterized in that the number of first spray holes (6) corresponds to n times the number of second spray holes (7), where n is an integer between 2 and 9. Nozzle assembly (1) Claim 1 or 2 , characterized in that the first spray holes (6) and / or the second spray holes (7) are each arranged at the same angular distance from one another. Nozzle assembly (1) according to one of the preceding claims, characterized in that the second spray holes (7) are arranged offset with respect to their angular position with respect to the first spray holes (6). Nozzle assembly (1) according to one of the preceding claims, characterized in that the second spray holes (7) are arranged at different angular distances from one another. Nozzle assembly (1) according to one of the preceding claims, characterized in that the first spray holes (6) are arranged in several superposed circles. Nozzle assembly (1) according to one of the preceding claims, characterized in that the second spray holes (7) are closer to a tip (11) of the nozzle body (5) in the axial direction than the first spray holes (6). Nozzle assembly (1) according to one of the preceding claims, characterized in that the longitudinal axes (A _S1 ) of the first spray holes (6) and the longitudinal axis (A _D ) of the nozzle body (5) each form an angle (α ₁ ) and the longitudinal axes (A _S2 ) of the second spray holes (7) and the longitudinal axis (A _D ) of the nozzle body (5) each enclose an angle (α ₂ ), the angle (α ₂ ) preferably being equal to or greater than the angle (α ₁ ). Nozzle assembly (1) according to one of the preceding claims, characterized in that the first injection holes (6) and / or the second injection holes (7) have an inlet fillet (10), the fillet radius (R) preferably being smaller than the respective injection hole diameter (D ) is. A fuel injector for injecting a gaseous main fuel and a liquid ignition fuel into a combustion chamber (2) of an internal combustion engine, comprising a nozzle assembly (1) according to one of the preceding claims.

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