DE102013012654B4 - Dual-fuel fuel injector - Google Patents

Abstract

A dual-fuel fuel injector (1) for a fuel injector, comprising a nozzle body (3), wherein: - a receptacle (5) for a nozzle needle (7) axially displaceable therein is formed in the nozzle body (3); - At one end portion (13) of the receiving (5) defining the nozzle body portion (15) is formed a first nozzle assembly (17) with at least one injection port (19) for the discharge of a first liquid fuel; - On the nozzle body (3) is formed a second nozzle arrangement (47) with at least one injection hole (49) for the discharge of a second, gaseous fuel; - On the nozzle body (3) the end portion (13) surrounding a nozzle cap (51) is arranged; - The second nozzle assembly (47) on the nozzle cap (51) is provided; - With the nozzle cap (51) a nozzle chamber (55) on the nozzle body (3) is defined, via which the at least one spray hole (49) of the second nozzle assembly (47) with the second fuel is flowed; characterized in that - a spray hole (49) or a plurality of spray holes (49) of the second nozzle assembly (47) is each formed in a male member (75) or are, which is received on the nozzle cap (51).

Description

The present invention relates to a dual-fuel fuel injector for a fuel injection device, in particular an internal combustion engine, according to the preamble of claim 1.

Gaseous fuels are becoming increasingly important in the large engine sector, especially in stationary engines for power generation. Due to its very good availability and its more favorable emission potential compared to diesel fuel, natural gas is excellently suited for economical and environmentally friendly engine operation. Most gas engines work after the Ottover procedure, d. H. with homogeneous combustion and spark ignition, wherein the ignition may be initiated by either a spark plug or a diesel jet injector. However, the Otto engine method has the disadvantage that during the charge change, caused by the external mixture formation, an undesirable methane slip. However, methane slip can only be prevented if a combustion process with internal mixture formation is used in the engine. For this purpose, a direct high-pressure injection is required.

In the previously implemented injectors with gas common rail technology, the potential of the gas injector is not fully utilized. A particular disadvantage is that for the introduction of the gas - due to production - simple injection holes are used similar to those of a diesel injector. These are fluidly unfavorable for gas, so that large cross sections for the required throughput are required. In a further disadvantageous manner, the gas pressure in the known nozzles is only partially converted into kinetic beam energy, the other part dissipates in the combustion chamber. A high speed, z. B. achievable with a Laval nozzle according to the document JP 2010-242 668 A However, the jet penetration depth would be useful and desirable to that extent.

Dual-fuel nozzles are also very expensive to manufacture, in particular if the gas valve and fuel needle are accommodated in the same nozzle body, see, for example, the document DE 203 09 001 U1 or the publication DE 10 2012 012 450 A1 , The needles are z. B. either concentrically nested in the nozzle body or housed separately in the nozzle body, z. B. is the fuel needle is centric and other gas needles are arranged eccentrically in the nozzle body to cover the full combustion chamber range of 360 °. Regardless of the particular variant, the space situation in the nozzle body is always extremely cramped and thus disadvantageous for a production of the nozzle in view of the effort to be operated for the production.

Proceeding from this, it is an object of the present invention to propose an improved dual-fuel fuel injector, which overcomes the above-mentioned disadvantages.

This object is solved by the features of claim 1. Advantageous developments and embodiments of the invention are specified in the further claims.

According to the invention, a dual-fuel fuel injector (dual-substance injector, in particular for a first, liquid and a second, gaseous fuel), in particular a diesel-gas injector, is proposed. The dual-fuel fuel injector is provided for a fuel injection device of an internal combustion engine, in particular z. B. for a gas common rail system. Generally, the fuel injector is preferably for use with an internal combustion engine in the form of a gas engine, in particular based on a gasoline or diesel engine (with internal mixture formation), further provided in particular with a large engine and further particularly for stationary applications, for example cogeneration or industrial applications. By means of the proposed dual-fuel fuel injector, both a pure liquid fuel operation and a combined liquid fuel / gas operation can be realized with any gas / liquid fuel fraction.

The dual-fuel fuel injector according to the invention has a nozzle body (nozzle element), wherein in the nozzle body, a receptacle (axial bore) is formed for a nozzle needle axially displaceable therein. In this case, a first nozzle arrangement with at least one injection hole for the discharge (injection) of a first, liquid fuel (preferably diesel fuel) is formed at one end portion of a nozzle body region defining the receptacle, d. H. at a nozzle-near end portion of the nozzle body. It is generally provided that the nozzle needle forms with the nozzle body a nozzle valve, via which a flow path for the first fuel to the first nozzle arrangement is selectively disclosed.

According to the invention, a second (gas) nozzle arrangement with at least one injection hole for the discharge (injection) of a second, gaseous fuel (for example natural gas, biogas, especially methane, etc.) is further formed on the nozzle body, on the nozzle body the end portion (of the Receiving nozzle area) surrounding a (separately formed or manufactured) (gas) nozzle cap arranged; the second nozzle arrangement is provided on the nozzle cap; and with the nozzle cap defines a nozzle chamber on the nozzle body, via which the at least one injection hole of the second Nozzle arrangement with the second fuel is flowed, in particular all the injection holes.

The thus equipped dual-fuel fuel injector advantageously allows a very inexpensive production, especially with regard to any rejects. As part of the production of the proposed dual-fuel fuel injector, the processing of the nozzle body can be carried out separately from the processing of the nozzle cap, whereby a possible rejects of the nozzle cap does not entail the reject of the entire nozzle body.

The dual-fuel fuel injector is characterized in that one or more spray holes of the second nozzle arrangement, preferably all - in particular each formed as a Laval nozzle - are each formed in a plug-in part or insert, which is accommodated on the nozzle cap, for example used in corresponding receptacles (holes) of the nozzle cap and subsequently welded (reib), for example. Such nozzle hole (insert) elements can be advantageously produced inexpensively, for example, as turned parts.

In the context of the present invention, the nozzle chamber preferably surrounds the end section as an annular space. In this way, in particular in connection with an embodiment of the fuel injector, the second (gas) nozzle arrangement or the nozzle cap has an injection-hole ring configuration surrounding the end section (whose injection openings are preferably distributed uniformly around the circumference of the end section). , Advantageously, a (homogeneous) 360 ° gas jet distribution in the combustion chamber can be achieved.

In the context of the present invention, it is also proposed in particular that one and / or several, preferably all, injection ports of the second (gas) nozzle arrangement are each formed as a Laval nozzle (or as a purely convergent nozzle). The design of a respective injection hole, in particular as a Laval nozzle, significantly improves the penetration of the gas jet. The gas entering the nozzle or injection hole is accelerated in the Laval nozzle and reaches the speed of sound in the narrowest Laval cross section. In the subsequent cross-sectional widening of the spray hole, the gas pressure is subsequently lowered, that is converted into kinetic energy. The high jet velocity achieved in this way is in the supersonic range and allows an intended advantageously high penetration depth in the combustion chamber.

The simple provision of a Laval nozzle that is complicated to manufacture in terms of its production is made possible, in particular, by the second nozzle arrangement being accommodated or provided on the nozzle cap. The nozzle cap is advantageous in the manufacture easy to handle, up to their connection in particular separated from the nozzle body, s. O.

On a cooling of the (gas) nozzle cap, for example, in pure liquid fuel operation, can be advantageously omitted in particular embodiments of the dual-fuel fuel injector, in which the nozzle cap is partially and / or entirely made of high-temperature steel. For this purpose, a precision casting and / or vacuum investment casting process is proposed for this purpose.

Alternatively or additionally, it may be provided for good cooling at the nozzle cap to form one or more cooling channels on the nozzle body, in particular its end section, which can be flowed through by a coolant (for example water, oil, liquid fuel). A cooling channel can, for example, in the nozzle body region defining the end section on the nozzle body, for. B. in the circumferential direction, be formed. Alternatively or additionally, it may be provided, for example, to form a large surface area for cooling in the nozzle space (gas-flowed area) provided in the nozzle cap, for example by ribbing or in general a suitable surface-enlarging structuring. In addition, by minimizing the contact surfaces between (gas) nozzle cap and the nozzle body, the heat flow into the nozzle body can be minimized.

Advantageous embodiments of the dual-fuel fuel injector further provide an embodiment such that in the nozzle body no control member for the gas valve is received. Instead, the control member is preferably received in the injector outside the nozzle body. In this embodiment, the nozzle space is preferably via at least one formed on the nozzle body (in particular passed through the nozzle body (from the nozzle to the nozzle near end)) flow path for second fuel flowed (for example, two or more flow paths); the respective flow path via a control member of the fuel injector selectively open controllable; and the respective control member is received outside the nozzle body in the injector. Such advantageous embodiments, in which the control member (gas valve needle) of the gas valve is received in the injector outside the nozzle body, allow a simpler design of the gas valve and also reduce its temperature load significantly (compared to a housing in the nozzle body).

The dual-fuel fuel injector according to the invention can furthermore advantageously be configured such that in the circumferential direction around the end section around a flow-guiding structure, in particular a puncture, is formed at the end portion, which (r) optimizes the flow of the second nozzle assembly via the nozzle space. The puncture may be, for example, a ring concavity (in the nozzle space around the end portion). In this case, the puncture can preferably be streamlined on the flow path for the second fuel.

Generally, it can be provided in the context of the present invention that the nozzle cap is fixed by threaded connection or a press fit or welding to the nozzle body. All of these methods enable a cost effective and inexpensive manufacture of the dual fuel fuel injector.

Also proposed is a fuel injection device (for an internal combustion engine), which is configured to be able to supply a first (liquid) and a second (gaseous) fuel to the dual-fuel fuel injector, wherein the fuel injection device at least one dual-fuel as described above Fuel Injector, in particular a plurality of dual-fuel fuel injectors.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 by way of example and schematically, in some cases greatly simplified, a fuel injector (not included in the invention) with a nozzle body shown cut and nozzle cap attached.

2 exemplary and schematically a nozzle body with nozzle cap for a fuel injector according to a possible embodiment of the invention.

3 exemplary and schematically a perspective view of the nozzle cap according to 2 ,

4 exemplary and schematically a sectional view of the nozzle cap according to 3 ,

In the following description and the drawings, the same reference numerals correspond to elements of the same or comparable function.

1 shows a - not included in the invention - dual-fuel fuel injector (two-fluid nozzle or dual-fluid injector) 1 with a nozzle body 3 (Nozzle member). The fuel injector 1 is intended for a fuel injection device of an internal combustion engine (internal combustion engine), preferably for a gas common rail system. The dual-fuel fuel injector 1 is provided for injection operation with a first liquid fuel (especially diesel fuel) and a second gaseous fuel (fuel gas).

In the nozzle body 3 is a receptacle (axial bore) 5 for a nozzle needle received therein in an axially displaceable manner 7 of the fuel injector 1 formed into which receptacle 5 High pressure fuel from a high pressure line (high pressure supply line) 9 of the injector internal fuel system, for example, from an upstream high pressure (HP) fuel inlet 11 of the fuel injector 1 (in communication with HD line 9 ). The fuel inlet 11 can z. B. via a single pressure accumulator (not shown) of the fuel injector 1 with the high pressure line 9 Alternatively, the direct connection of the fuel inlet can be connected 11 with the high pressure line 9 be provided, for. B. in embodiment without a single pressure accumulator.

At one end section 13 one the recording 5 defining nozzle body area 15 is a first nozzle arrangement 17 with at least one spray hole 19 formed for the discharge (injection) of the first liquid fuel.

The one in the recording 5 introduced high-pressurized first fuel can be a function of the (stroke) position of the nozzle needle 7 over the nozzle arrangement 17 of the dual-fuel fuel injector 1 be discharged when operating with a fuel injection device in particular injected into a combustion chamber of an internal combustion engine. The nozzle arrangement 17 (Spiracles 19 ) is preferred on a nozzle tip 21 of the nozzle body 3 provided.

The dual-fuel fuel injector 1 may be preferred for injecting the first fuel as an indirectly actuated injector 1 be formed, in particular with a pilot valve 23 , which is dominated by an actuator (not shown), preferably a Magnetaktuatorik. The pilot valve 23 and / or the actuator system can be arranged in at least one valve housing (housing element) 25 of the injector housing 27 , in particular adjacent to the nozzle remote End of the nozzle body 3 of the injector 1 be provided, for example, in a valve body 25 ,

Alternatively it can be provided, the injector 1 for injecting the first fuel as a directly operated injector 1 to design, the actuator in particular directly to the nozzle needle 7 can work.

About the pilot valve 23 can be a tax room 29 of the fuel injector 1 relieved valve position dependent, for example via a leakage flow path 31 the injector internal fuel system, which starting from the control room 29 to a low pressure side (ND) leakage outlet 33 of the injector 1 via the pilot valve 23 (under throttling 35 ), z. B. to a Leckagesammelbehältnis (tank) of a fuel injection system.

In the control room 29 continues to lead z. B. another high pressure path 37 of the injector internal fuel system (with throttling 39 ) over which the control room 29 via high-pressure-loaded first fuel from the high-pressure line (high-pressure passage) 9 is resilient. The control room 29 can by means of a needle guide sleeve 41 be formed, which at the nozzle distal end of the axial bore 5 is included in the same, wherein in the axial bore 5 still a closing spring 43 can be arranged, which the nozzle needle 7 in the closed position urges, ie against a valve seat or nozzle needle seat 45 ,

To fuel for an injection operation via the nozzle assembly 19 to be able to deploy, ie on the part of the axial bore 5 , the (closing) force equilibrium at the nozzle needle 7 by relieving the control room 29 via the pilot valve 23 be dissolved (leakage flow path 31 opened), leaving the nozzle needle 7 from the nozzle needle seat 45 lift off and the flow path to the nozzle assembly 17 can release. For closing the nozzle valve is the pilot valve 23 switched to locked position (in 1 open position is shown), whereupon the pressure in the control room 29 over the high pressure path 9 . 37 builds up again and the nozzle needle 7 closing spring assisted in the nozzle needle seat 45 returns.

As in 1 illustrated is on the nozzle body 3 a second nozzle arrangement 47 with at least one spray hole 49 formed for the discharge (injection) of the second gaseous fuel. The second nozzle arrangement 47 is on one (separate from the nozzle body 3 formed or manufactured) (gas) nozzle cap 51 provided or formed, which nozzle cap 51 the end section 13 surrounding the nozzle body 3 is arranged. For this purpose, the nozzle cap 51 preferably shell or cup shape, ie with a bottom opening or through hole 53 in / through which the end section 13 can dip or dive.

As 1 is further illustrated in or with the nozzle cap 51 a nozzle space 55 on the nozzle body 3 defined (around the end section 13 around), over which the at least one spray hole 49 the second nozzle arrangement 47 , in particular all spray holes 49 , with the second fuel is flowed.

To the flow of the nozzle chamber 55 with gaseous, second fuel, the nozzle body in the present case has a first 57 and a second 59 Flow path (gas channel) on, alternatively z. B. a single channel, which from the side of a gas inlet 61 of the dual-fuel fuel injector 1 and one - through the injector housing 27 guided, in the first 57 and the second flow path 59 Restrictive - flow path (gas channel) 63 can be acted upon with the second fuel. The flow paths (flow channels) 57 . 59 extend as drilling channels from the nozzle distal end of the nozzle body 3 to the nozzle room 55 (in 1 are still welded plugs 65 can be seen which after manufacturing the flow paths 57 . 59 close a respective inlet opening for a drilling tool). In an injection mode, a respective flow path (gas channel) 57 . 59 For example, with a gas pressure of about 350 bar applied.

Preferably located in the injector housing 27 - outside the nozzle body 3 recorded - continue to be a valve or gas valve 67 with a likewise in the injector housing 27 recorded control member in the form of a (gas) valve needle (not shown). About the gas valve 67 can the flow path 63 are selectively interrupted, thus the gas supply to the nozzle chamber 55 via flow paths 57 . 59 , Thus, the dual-fuel fuel injector allows 1 advantageous both a combined injection operation with first and second fuel and the application of only the first or only the second fuel. It should be noted that, as mentioned above, by the arrangement of the control member in the injector 27 an advantageous thermal relief of the same or of the gas valve 67 can be achieved. Alternatively, of course, embodiments are conceivable that do not provide such a solution.

In the dual-fuel fuel injector 1 surrounds the nozzle chamber 55 the end section 13 on the one hand preferably as an annular space, see for example 1 , and to the second, the second nozzle arrangement 47 one prefers the end section 13 surrounding injection hole ring configuration at the nozzle cap (gas injection nozzle cap) 51 on (in Communication with the nozzle chamber 55 ). Such an extremely simple flow of the nozzle holes is realized with the advantage of 360 ° gas distribution in an injection.

In the embodiment of the dual-fuel fuel injector 1 to 1 has the nozzle cap 51 a relatively high (cup-shaped) design, which is particularly well suited to the nozzle body 3 screwed, reference numerals 69 to be pressed and / or laser welded (at a pressure can already be achieved an advantageous good sealing effect). For easy production of the spray holes 49 , which in the context of the present invention are preferably each formed as Laval nozzles, the nozzle cap 51 to 1 preferably manufactured by investment casting (with cast holes 49 ), further preferably made of high temperature steel. For the production of the injection holes 49 may alternatively be provided, for example, the spray holes 49 with a (hook-shaped) electrode to erode.

1 also shows one in the end section 13 recorded cooling channel 71 which may optionally be provided. The cooling channel 71 can be traversed by a coolant via a flow and a return (not shown).

2 shows a nozzle body 3 with mounted nozzle cap 51 a dual-fuel fuel injector 1 according to a preferred embodiment of a dual-fuel fuel injector according to the invention 1 (In this embodiment, in addition to the illustrated nozzle cap 51 high design alternatively be provided a flat design).

At the nozzle cap 51 are the spray holes 49 , again each in the form of a Laval nozzle, each in a plug-in part 75 formed, which at the nozzle cap 51 is included (in a corresponding version). The insertion parts are preferred 75 - In particular advantageously produced inexpensively as turned parts - with the nozzle cap 51 friction welded. The manufacture of the fuel injector 1 is flexible and with little waste.

Further advantageous and optional combined with other embodiments of the fuel injector shows 2 a flow guiding structure 77 at the end section 13 , The flow guiding structure 77 , which as an annular recess or concavity around the end portion 13 is guided (in the nozzle chamber 55 ), causes a favorable flow guidance or an optimized flow inlet of the part of the flow paths 57 . 59 in the nozzle chamber 55 introduced second fuel toward or into the injection holes 49 ,

3 and 4 show more views of the nozzle cap 51 according to 2 , Can be seen on the nozzle cap 51 drilling 79 be provided, for example, for attaching a hook wrench for a screw connection with the nozzle body 3 ,

It should be noted in conclusion that the pressure load on the nozzle cap 51 compared to the diesel injector is relatively low. The combustion pressure of approx. 200 bar largely compensates for the gas pressure load when viewed from the outside. The working pressure differences are in the order of 150 bar.

The cooling of the dual-fuel fuel injector 1 at the nozzle can be done in the gas mode via the gas itself. The expansion capability of the gas has a positive effect, since the gas cools down due to the pressure drop downstream and in particular due to the pressure reduction in the Laval nozzle. The aim can be a large-scale design of the nozzle cap 51 in the gas-flowed nozzle chamber 55 for a good cooling effect (eg by ribbing).

The cooling in pure liquid fuel operation, however, is a bit more problematic, as far as the nozzle cap 51 is not cooled without a gas stream, but is additionally claimed by the pressurized during the combustion process penetrating hot gas from the inside, as well as the shaft of the nozzle body 3 , As the dual-fuel fuel injector 1 or nozzle body 3 in this case, however, flows through a high fuel flow rate, a sufficient cooling as conventional fuel nozzles is secured.

LIST OF REFERENCE NUMBERS

1

Dual-fuel fuel injector

3

nozzle body

5

axial bore

7

nozzle needle

9

High-pressure line

11

High pressure inlet

13

end

15

Nozzle body area

17

Nozzle arrangement (first fuel)

19

Spray hole (first fuel)

21

injector cap

23

(Pilot) valve

25

valve housing

27

injector

29

control room

31

Leckageströmungsweg

33

leakage outlet

35

throttling device

37

High-pressure fluid path

39

throttling device

41

Needle guide sleeve

43

nozzle spring

45

Nozzle needle seat

47

Nozzle arrangement (second fuel)

49

Spray hole (second fuel)

51

(Gas) nozzle cap

53

passage

55

nozzle chamber

57, 59

Flow path (second fuel)

61

Inlet (second fuel)

63

Flow path (second fuel)

65

Plug

67

(Gas) valve

69

screw

71

cooling channel

75

male

77

flow-conducting structure

79

drilling

Claims (9)

Dual-fuel fuel injector ( 1 ) for a fuel injection device, comprising a nozzle body ( 3 ), wherein: - in the nozzle body ( 3 ) a recording ( 5 ) for an axially displaceable nozzle needle ( 7 ) is formed; At an end portion ( 13 ) one of the recording ( 5 ) defining nozzle body region ( 15 ) a first nozzle arrangement ( 17 ) with at least one injection hole ( 19 ) is formed for the application of a first, liquid fuel; - on the nozzle body ( 3 ) a second nozzle arrangement ( 47 ) with at least one injection hole ( 49 ) is formed for the discharge of a second, gaseous fuel; - on the nozzle body ( 3 ) the end section ( 13 ) surrounding a nozzle cap ( 51 ) is arranged; The second nozzle arrangement ( 47 ) on the nozzle cap ( 51 ) is provided; - with the nozzle cap ( 51 ) a nozzle space ( 55 ) on the nozzle body ( 3 ) is defined, over which the at least one injection hole ( 49 ) of the second nozzle arrangement ( 47 ) is flowed to the second fuel; characterized in that - a spray hole ( 49 ) or several spray holes ( 49 ) of the second nozzle arrangement ( 47 ) each in a plug-in part ( 75 ) is formed on the nozzle cap ( 51 ) is recorded. Dual-fuel fuel injector ( 1 ) according to claim 1, characterized in that - the nozzle space ( 55 ) the end section ( 13 ) surrounds as annulus and / or the second nozzle arrangement ( 47 ) one the end portion ( 13 ) surrounding injection hole ( 49 ) Ring configuration on the nozzle cap ( 51 ) having. Dual-fuel fuel injector ( 1 ) according to one of the preceding claims, characterized in that - the nozzle space ( 55 ) via at least one of the nozzle body ( 3 ) formed flow path ( 57 . 59 ) is flowed to the second fuel; The respective flow path ( 57 . 59 ) via a control element of the fuel injector ( 1 ) is selectively openly controllable; - The respective control member outside the nozzle body ( 3 ) in the injector ( 1 ) is recorded. Dual-fuel fuel injector ( 1 ) according to one of the preceding claims, characterized in that - one or more or all spray holes ( 49 ) of the second nozzle arrangement ( 47 ) are each formed as a Laval nozzle or as a convergent nozzle. Dual-fuel fuel injector ( 1 ) according to one of the preceding claims, characterized in that - the nozzle cap ( 51 ) is made partly or wholly of high-temperature steel and / or by means of precision casting and / or by means of vacuum investment casting. Dual-fuel fuel injector ( 1 ) according to one of the preceding claims, characterized in that - in the circumferential direction around the end portion ( 13 ) a flow-conducting structure ( 77 ) at the end portion ( 13 ) is formed, which the flow of the second nozzle assembly ( 47 ) over the nozzle space ( 55 ) optimized. Dual-fuel fuel injector ( 1 ) according to one of the preceding claims, characterized in that - the nozzle cap ( 51 ) by threaded connection ( 69 ) or a press fit and / or welding to the nozzle body ( 3 ). Fuel injection device, characterized in that - the fuel injection device at least one dual-fuel fuel injector ( 1 ) according to one of the preceding claims. Fuel injection device according to claim 8, characterized in that the fuel injection device is arranged, a first, liquid and a second, gaseous fuel to the dual-fuel fuel injector ( 1 ).

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