WO2006136152A1

WO2006136152A1 - Method and device for the direct injection of fuel into reciprocating internal combustion engines

Info

Publication number: WO2006136152A1
Application number: PCT/DE2006/001087
Authority: WO
Inventors: Uwe Lienig; Ernstwendelin Bach; Maurice Kettner; Amin Velji; Ulrich Spicher; Reinhard Latsch
Original assignee: Hochschule für Technik und Wirtschaft Dresden; Universität Karlsruhe
Priority date: 2005-06-21
Filing date: 2006-06-20
Publication date: 2006-12-28
Also published as: DE112006002024A5; EP1899598A1

Abstract

The invention relates to a method and a device for the direct injection of fuel into reciprocating internal combustion engines, the injected fuel being gasoline, diesel, or combustion gases (e.g. natural gas). The aim of the invention is to improve the combustion process in reciprocating internal combustion engines while reducing the emission or formation of harmful substances, especially nitrogen oxides, in the exhaust gas, fuel being fed to a variably swirling injection nozzle at an elevated pressure via at least one inlet (I, II), a swirl chamber (7) being embodied in the injection nozzle. A basic mixture is injected into the cylinder in a first phase in which the port of the injection nozzle is open while fuel simultaneously flows back from the injection nozzle via a recirculation pipe (10) or one of the inlets (I, II). An ignition mixture is then injected in a second phase in which the injection nozzle is open, the recirculation pipe (10) is closed, and fuel is prevented from flowing back from the injection nozzle.

Description

Method and device for direct injection of fuel in reciprocating engines

The invention relates to a method and a device for the direct injection of fuel in

Reciprocating engines, which may be an injection of gasoline, diesel or even fuel gases (for example natural gas).

In the gasoline direct injection further development depends on the characteristics of the injection system and in particular of the injection nozzle. In the case of the wall-guided methods, the combustion chamber surface generally increases, and at the same time the combustion chamber has unfavorable geometric surfaces, which result in an increase in the heat flow, in particular in the pistons.

The airborne processes can not exploit the potential of gasoline direct injection because of the generation of intense air movement in the cylinder must be bought with corresponding disadvantages in the filling. Again, the charge movement causes an intensification of the heat flow in the combustion chamber delimiting components and thus reduces the achievable efficiency gain.

In addition, in both air or wall guided procedures, their applicability is limited to certain areas of the engine load range. An expansion of the operating range are limited by the mutually adversely affecting properties of the respective methods.

One solution to these limitations is seen as transitioning to jet-guided processes. In the case of spray-guided processes, the generation of an ignitable mixture must be ensured by the fact that the beam geometry can always be adapted to the load-point-dependent requirements.

Thus, a swirl nozzle with a geometrically variable swirl chamber is described in DE 100 60 435 A1. Efforts to use nozzles with variable geometric dimensions in internal combustion engines, however, have so far been unsuccessful. In particular, the high thermal and mechanical stresses lead to considerable difficulties in the realization.

If one considers the motor injection as a sputtering process, one finds corresponding parallels to spraying processes in the process engineering. Sputtering systems with a swirl chamber allow a continuous change of the beam parameters. The swirl chamber has a peculiarity in relation to the tangentially incoming channels. The channels have a different cross section and, each considered individually, generate a different twist. For a given supply pressure, a smaller swirl is associated with a higher swirl velocity and a smaller swirl velocity with the larger cross-section. The fluid flow twisted in the chamber leaves the atomization system via a concentrically arranged outlet hole. By skillful choice of the channel parameters, a spin system can be built in which a certain base twist of the liquid in the chamber is predetermined via the small channels. The change in the atomization parameters can be achieved by connecting the liquid flow over the large channels. The design of the channels allows the atomization quality to remain almost unchanged even with increasing throughput.

These properties of such spin-variable injection nozzles can be the basis for further development. An injection nozzle from EP 1 029 175 Bl known. It can also be used in principle in connection with the invention. Reference should be made in full to their disclosure content.

An essential difference in comparison to process technology is that process technology often involves continuous processes. In contrast, fuel injection is characterized by repetitive single events. The adaptation of the swirl-variable nozzles known from process engineering therefore takes place by supplementing the nozzle with a nozzle needle. With the help of the nozzle needle, the centrally arranged nozzle outlet locked. In addition to the direct influencing of the jet parameters by the choice of the swirl level, the injector should also allow the setting of defined fluid dynamic parameters, even with the nozzle needle closed. Therefore, the

Injection nozzle supplemented by a return. The return leads from the swirl chamber an adjustable flow of fuel flow. As a result, the designed spin-variable injection nozzle can flow through even when the nozzle needle is closed and the operating state can be determined independently of the injection event. An overall view of the hydraulic circuit of the injection nozzle is given in FIG.

It is an object of the invention to improve the combustion process in reciprocating engines and to reduce pollutant emission or formation, in particular of nitrogen oxides in the exhaust gas.

According to the invention, this object is achieved by a method having the features of claim 1. It can be used in the method, a device according to claim. Advantageous embodiments and further developments can be achieved with features designated in subordinate claims.

The method according to the invention is carried out in such a way that fuel is supplied to a spin-variable injection nozzle in which a swirl chamber is formed. When injecting a basic mixture at least one inlet and the return is open. Subsequently, an ignition mixture is then injected with the return closed.

When injection of the basic mixture occurs clearly larger cone angle, so that a large area in the cylinder with fine droplets of fuel is applied and a very lean mixture is present. The injection of the basic mixture can already start in the intake stroke and be carried out until shortly before the start of ignition. (Eg start at minus 90 ° up to 270 ° before TDC)

Then ignition mixture is injected with a much smaller jet cone angle, so that in a small

Volume range is a fat ignitable mixture.

For piston engines, a piston with a recess formed in the piston head can preferably be used. The ignition mixture should then be injected as completely as possible into the trough and ignited in the trough. This can also be combined with the BPI method mentioned below.

In principle, the number in the cross section of different channels of an injection nozzle, which run tangentially into the swirl chamber, set only geometric limits. For fluid dynamic considerations, however, it makes sense that more than one tangential channel is always in operation. Investigations show that swirl chambers with only one tangentially incoming channel have a strongly asymmetrical spray pattern and are probably not suitable for use in a fuel injection nozzle. Because there are always several channels over the same. Cross-section, it makes sense to form channel groups.

Below, the invention will be explained in more detail by way of example. Showing:

Figure 1 is a hydraulic diagram for a device which can be used in the invention;

Figure 2 is an exploded view of an insertable in the invention injector;

FIG. 2 a parts of an injection nozzle with a swirl return;

FIG. 2 b shows an operating diagram for a possible implementation of the method according to the invention;

Figure 3 is a schematic representation of a fuel inlet via channel groups in a swirl chamber;

FIG. 4 indicates possible main dimensions of a swirl chamber in the case of a spin-variable injection nozzle;

Figure 5 is a graph of the influence of the amount of return of fuel on the mass of fuel injected;

FIG. 6 shows a measurement specification for determining the penetration depth and beam cone angle of injected fuel;

FIG. 7 shows a diagram illustrating the influence of the amount of return of fuel on the achievable jet depth;

FIG. 8 injection jet images with modified return flow at ambient pressure conditions;

FIG. 9 injection jet images with modified return running current at a back pressure of 10 bar;

FIG. 10 shows a diagram of the jet angle with a modified return flow rate and changed backpressure;

FIG. 11 injection jet images with modified return flow with a changed volume flow of fuel supplied via a channel group;

FIG. 12 shows a diagram of the influence of beam cone angle and changed fuel feed ratio;

Figure 13 shows a principal possibility of using the invention in a BPI concept;

Figure 14 shows a schematic representation of favorable geometric relationships at a nozzle exit hole and

Figure 15 test results when using the invention in the BPI method.

The hydraulic circuit of an inventive system, as shown in FIG. 1, illustrates that the injection nozzle has two inlets I and II. The inlet I to the channels with a small cross-section has no adjustment for the flow and thus determines the basic twist in the swirl chamber. The inlet II for the large channels and the return are provided with a flow adjustment. In addition to the inlets, the representation also includes the flow-controlled return from the swirl chamber 7.

In this case, for the regulation of the inflow of fuel from a tank 12 at a feed II, a control Valve 14 available. Furthermore, between tank 12 and inlet II, a further inlet I is connected there. Fuel can be fed to the injection nozzle via inlets I and II. In addition, a return 10 is present, via the fuel in the

Tank 12 can be returned, if this is desired in one or possibly several phases of a fuel injection operation. To regulate the return flow via the return line 10, a control valve 13 is present there.

The amount of fuel returned to the tank via the return 10 may be regulated during the first phase. As a result, the beam cone angle can also be influenced and adaptation to the respective combustion chamber shape or formation of a piston with or without a trough can be carried out.

The resulting from the hydraulic circuit settings set at the same time the conceivable modes. Table 1 summarizes and explains the operating modes. In this case, a further operating mode is added, resulting from the adjustment of the fuel supply, which was constructed to investigate a spin-variable nozzle.

It may also be possible, if this is due to the operation of the reciprocating engine during the second phase, so when injecting ignition mixture to allow a small reflux of fuel. In this case, the amount of fuel injected thereby can be slightly reduced.

But there is also the possibility only one Feed I or II use, so that the fuel supply is then realized via a single inlet I or II.

Another alternative is a waiver of the return. Then one of the feeds I or II temporarily forms the return, wherein in the corresponding inlet I or II then a bypass line to the tank and a valve which can shut off this inlet should be present.

The exploded view of Figure 2 illustrates a possible construction of a usable in the invention injector. It is a nozzle needle 1 passed through the injection nozzle, which can close or open the nozzle exit hole 11. For the supply of fuel several channels 2 and 3 in channel groups I and II are present, which are guided by an upper fuel guide 4 and a Kraftstoffzwischen- guide 5 with a centrally arranged return channel through the upper swirl chamber cover 6 with a swirl return chamber 9 to the swirl chamber 7. Below the swirl chamber 7, the lower swirl chamber cover 8 is arranged with a nozzle outlet hole.

The channels 2 and .3 of the channel groups I and II are pressure-tight separated from each other to the swirl chamber 7. During operation, the supply of fuel through the channel group I is constantly. By additionally supplying fuel via the channel group II, only the respective amount of fuel is increased. However, this also exerts an influence on the course of injection (course of the injection quantity over the injection time).

When injecting the basic mixture, the backbone should run 10 are opened before the opening of the nozzle needle 1. The return 10 should, however, be closed later for the injection of the ignition mixture when the injection nozzle is open, that is to say the free nozzle needle 1.

FIG. 2 a is intended to illustrate an additionally present swirl return chamber 9, which is designed here as an annular gap arranged around the nozzle needle 1. During the return flow of fuel from the swirl chamber 7 in the direction of the tank 12, a flow provided with a swirl can be maintained there, which can have an advantageous effect. In an unillustrated form, there may be additional swirl elements, for example helical guides or depressions, for supporting swirl maintenance in this area. The height of the swirl return chamber 9 should be greater than the height of the swirl chamber 7. The height of the swirl chamber 9 should preferably be significantly greater and have a multiple of the height of the swirl chamber 7. In this case, the height means the extent parallel to the nozzle needle 1.

By maintaining a swirl by means of

Swirl return chamber 9, the cone angle of an injection jet can be further increased and the combustion can be positively influenced, in particular for a reduction of pollutant emissions.

A swirl chamber 7 can be formed with one or more swirl disks.

FIG. 2 a also shows relative cross-sectional ratios of channels 2 and 3 of the channel groups I and II. FIG. 2 b shows two phases of an injection according to the invention with an injection of a basic mixture with the return open and subsequently in a second phase of an ignition mixture with a closed return with the corresponding jet cone geometry.

The design of a spin-variable nozzle and the associated definition of the dimensions of the swirl chamber, the nozzle hole and the tangential channels is based on the fluid dynamic relationships. Due to the currently extensive efforts in the field of gasoline direct injection, typical injection parameters from this area served as a starting point for the design. The data used are listed in Table 2.

With the help of this information, the determination of dimensions for a swirl chamber, the Tangentialkanä- Ie and the nozzle exit hole. The characteristic dimensions are compiled in FIG.

FIG. 4 indicates possible main dimensions of a swirl chamber 7 in the case of a swirl-variable nozzle.

The injection nozzle consists of a swirl chamber 7 with a constant diameter and basically has 2 channel groups each having four channels with the same cross-section. However, the absolute dimensions have little significance in terms of the behavior of the swirl variable nozzle. Therefore, the marking of the swirl variable nozzle is carried out by means of ratio ratios. Table 3 summarizes the key figures that are given for the injector investigated here. With regard to the flow through the swirl chamber 7, the area ratios were determined so that, on the one hand, the minimum and maximum inflow area over the channel groups is substantially larger than the nozzle hole circle area ( ^KJ and ^KJI ) and, on the other hand, the

Area of the return approximately the same size [Y ^RJ and Y ^R ' ⁿ ) has, as the inlet through the channels. This ensures that much more fuel can always flow into the swirl chamber 7 than can flow out via the nozzle hole. At the same time it is possible to derive almost all of the incoming fuel through the feedback without pressure difference.

With regard to the expected beam cone angle, it can be deduced from the large relative hole length of the nozzle exit hole { ^L ) 11 that the smallest beam cone angle due to a lack of twist must be very small. When operating the injector without return is associated with a pronounced Vorstrahl. What behavior the injector with variable return or with variable inflow ratio on the channel groups shows will be explained below.

In the invention, the simplest possible embodiment for injectors used therein, which can be produced with relatively simple production technologies, with relatively free choice of the dimensions of the function-determining components (swirl chamber and nozzle hole plate) are used.

This approach resulted in a constructive solution that can be completely dismantled non-destructively. Figure 3 gives an overall view of the CAD construction shown structurally realized leadership of the fuel and illustrates the operating principle of the swirl variable nozzle.

After production, an injection system was available that could be subjected to various tests in the pressure chamber. The test results are the subject of the following sections. The investigations on the behavior of the nozzle took place on a pressure chamber test stand. Ambient pressure and backpressure of 10 bar were applied during the tests. The fuel supply was provided by a common rail system. Since the investigations initially focus on the potential for influencing the beam geometry, commercial petrol was used as the fuel.

For the identification of the operating state, however, it is not sufficient for the swirl variable nozzle, only the

Supply pressure to specify. As can be seen from the different operating modes (Table 1), the current return flow and the partial flow through the controlled channel group II must also be specified. For a complete description of the

Operating parameters are therefore introduced characteristic values according to Table 4.

Regardless of the operating condition, the supply pressure ^Sys remained constant in all experiments and was 75 bar. To mark the operating state of the injector in the individual experiments, the remaining parameters are given.

As can be seen from the compilation of geometrical relationships in Table 3, the back- 10, the possibility, even with the nozzle needle 1 closed, of dissipating the fuel stream supplied via a channel group under a given pressure completely via the return line 10, since the area ratios ^{R> 1} and ^R ' ⁿ cause practically no throttling. However, the conditions change when the nozzle needle 1 releases the nozzle exit hole 11. The additionally released outflow cross-section causes now the pressure conditions in the swirl chamber 7 by the ratio of Gesamtzuströmquerschnittes (sum of the operating channel groups) and the effective cross-section of the return 10 (depending on the set in the operating point throttling in the feedback according to Be operating mode overview in Table 1) are determined. Due to the open nozzle needle 1, therefore, the pressure in the swirl chamber 7 will decrease. It can be assumed that the greater the return flow, the greater the pressure reduction in the swirl chamber 7. Therefore, it is expected that the injection quantity decreases with increasing return flow. In addition, however, the injection quantity is also influenced by the increasing swirl with increasing return flow.

The dependency of the injection quantity on the return flow is represented by an operating point with a variable return flow ^ - ^ between 0 and 1 l / min, a constant φπ of 0.1 and a variable injection time in FIG. In addition to the results of the swirl operation of the injector, the measured values are also included when operating via the return line.

FIG. 5 illustrates the influence of the return quantity on the injection mass. First, it can be seen that the injection mass increases linearly with the injection time in the swirl variable nozzle. It shows the same behavior as normal injectors. In contrast to normal injection nozzles, however, the injection quantity can be influenced not only by the supply pressure and the injection time, but also by the return quantity. In the present injection nozzle, the spread of the injection quantity is almost 400%, ie at the same pressure, the injection mass of a selected

Design point can be increased to 4 times the amount. This makes it possible to adjust the injection rate significantly further to the requirements of a given combustion process. Finally, this behavior can also be used to improve the suitability for the smallest quantity injection.

As already explained, the return flow greatly influences the pressure conditions in the swirl chamber 7. The reduction of the injection rate proves that the effective pressure difference for the fuel injection decreases. This is accompanied by a reduction in the exit velocity. It is to be expected that this will result in a reduction in the penetration depth of the injection jet.

In order to determine the influence, radiation-optical investigations were carried out. With the aid of a triggered CCD camera, images of the injection beam were produced in the transmitted light process, showing the injection jet in silhouette. For the evaluation of the shadow images was a measurement specification, as shown in Figure 6.

The measurement specification is not only used to determine the penetration depth S _Edt and therefore also contains the information for determining the cone angle αKgl. Due to the observation field of the camera, the beam could only be measured up to a maximum distance of 35 mm. The results obtained from the strahlopti investigations are shown in FIG.

FIG. 7 shows the influence of the amount of return on the jet penetration depth.

The measurements confirm that the penetration depth decreases with increasing return flow. It should be noted that the behavior of the injection nozzle during operation via the return line 10 (Table 1, line 4) and with closed return 10 (Table 1, line 1 or 2) is virtually identical. The associated beam images, which are shown below, show the cause of this behavior. In both operating modes, no significant difference can be seen in the spray pattern. Therefore, it can be considered that the conditions at the nozzle hole end are not different.

The other operating modes show that not only is there a decrease in the penetration depth. With increasing injection duration, the penetration depth no longer increases. Especially in the case of a large amount of return, the curve changes into an almost horizontal part.

With increasing return flow and due to the relationships between the inflow and outflow cross sections, a stronger swirl in the swirl chamber 7 occurs. Since the swirl is already present at the beginning of the injection and is retained during the entire injection period, the associated Improved nebulization of smaller drops. This relationship means that at a certain distance from the nozzle hole, the drops are very small due to the beam interaction and no visible beam boundary is more recognizable.

The measurement of the jet penetration depth had shown that the amount of return has a strong influence on the jet properties. The other important geomet- ric size of the injection jet is the beam cone angle. Together with the penetration depth, it is possible to derive a suitability for a specific mixture formation process or to design a process from this information.

While the penetration depth depends substantially on the initial impulse of the fuel drop, the ratio of radial and axial velocity at the outlet hole determines the jet cone angle in the swirl nozzle. The radial velocity at the exit hole is essentially determined by the swirl in the swirl chamber 7. The axial velocity results from the pressure difference across the nozzle exit hole 11. Due to friction effects, the two components decrease over the length of the nozzle exit hole 11.

As a measure of the expected friction losses, the ratio ^L can be used. For the present nozzle, this ratio is relatively high at 2.3. Therefore, only a relatively small beam cone angle would be expected.

However, the swirl prevailing in the swirl chamber 7 is not determined solely by the outflow velocity from the nozzle outlet hole 11. Conditional on the selectable return quantity can be generated a much higher swirl in the swirl chamber 7, as he would result from the outflow conditions (pressure difference across the nozzle outlet hole) of a simple swirl chamber 7. Thus, the return amount becomes the determining factor for the peripheral speed at the nozzle exit hole end.

The jet images resulting from the variation of the return quantity are compiled in FIG. In a horizontal arrangement extends the time course of the injection images, while the return amount increases downward. The pressure in the pressure chamber in these experiments was at the level of the environment.

FIG. 9 shows injection jet images with variable return flow and 10 bar chamber pressure.

The increase in the chamber pressure leads, as already indicated, to a reduction in the penetration depth.

At the same time, however, it also shows that the cone angle of the untwisted jet increases slightly and corresponds to the behavior of normal hole nozzles. Due to the increasing return flow, the nozzle increasingly behaves like a swirl nozzle. At the same time, the jet cone angle decreases with increasing backpressure. Furthermore, the typical for swirl nozzles beam shape is to be seen at the top, which is caused by the emerging at the beam edge air currents.

In contrast to the swirl nozzles without return, however, it can also be seen here that the swirl generated by the return in the swirl chamber 7 leads to the fact that no pre-jet can be seen. As already observed in the tests without back pressure, the injection jet from the nozzle outlet hole 11 occurs with the for the set operating parameters typical cone angle.

The determination of the cone angle confirms the visual impression. FIG. 10 compares the profiles of the jet cone angle determined for the two chamber pressures as a function of the return flow.

FIG. 10: Beam cone angle with variation of return quantity and chamber pressure

The beam cone angle when operating on the return line 10 is only slightly below that which occurs during operation with closed return 10. The small difference supports the assumption that the swirl built up in the swirl chamber 7 collapses again in the long nozzle exit hole 11. The increase in the chamber pressure leads to an increase in the beam cone angle at these two operating points.

As the return flow increases and the basic spin increases, the increase in chamber pressure causes a decreasing cone angle. Thus, while in the absence of a basic spin the cone angle increases with increasing chamber pressure, this leads to a decrease in the cone angle as the base twist increases.

This behavior can be used for a given geometric arrangement of injector and spark plug to correct the beam geometry depending on the current load point and / or injection timing.

As already explained at the beginning, consists in the It is also possible to influence the swirl by changing the inflow ratio ^ ¹¹ . The flow velocity in the channels of the second channel group is indeed much lower due to the cross-sectional ratios compared to the channel group I.

To determine the influence, the ratio ^ ^{11 is} changed for a selected return flow. Thus, by increasing the flow through channel group II (^ becomes larger), the cone angle can be reduced. The basic behavior of the nozzle that the injection jet exits without Vorstrahl, but still maintained.

The dependence of the beam cone angle on the volume flow ratio is plotted in FIG. The determination of the beam cone angle is based on the measurement specification in FIG. 5.

FIG. 12 illustrates the beam cone angle with a variable feed ratio Φn.

From FIG. 11, a relatively good linear dependence of the cone angle of the cone can be deduced from the feed ratio. Since an increase in the flow through the channel group II is to be compared with an increase in the effective cross section, this results in a reduction of the inflow velocity in the swirl chamber. This is also a reduction of the radial velocity at the nozzle hole end connected, which leads to the reduction of the beam cone angle.

Figure 13 shows a schematic diagram of the combustion process according to the BPI concept (Bowl Prechamber Ignition). Due to the great demands of the BPI process, the spin variable nozzle is very well suited for the direct injection of fuel. By deliberately changing the operating status of the spiral-variable nozzle, the spray pattern can be precisely adapted to the requirements. In the formation of the basic mixture, a large cone angle is required in order to achieve the best possible homogenization of the lean base mixture. The generation of the enriched ignition mixture, which is conveyed into the ignition chamber, takes place with a very small cone angle. Considering the above explanations and referring to the modes in Table 1, it is necessary to switch from the basic mixture mode 3 to the 1 or 2 mode for the accumulation amount within one cycle.

For switching between the operating modes, an operating concept was realized in which the return flow 10 is opened during the basic mixture formation and sets a fixed return flow rate and the associated cone angle. In the formation of the enrichment amount, the return 10 is closed, the cone angle thereby collapses and the enrichment amount can be accurately placed.

Overall, the injector completed about 24 hours of operation very successfully, the nozzle even after that worked perfectly. A result of the experiments, which is intended to show the potential of the method, is contained in FIG.

For comparison, in FIG. 15 the operation with conventional nozzles is compared with the operation with a spin-variable nozzle. The significant reduction in NOx emissions through internal mixture formation only leads to a small increase in HC emissions. At the same time, the test results could be achieved with a lower fuel pressure, which may be considered as an indication of the good atomization properties of the injection nozzle in the formation of the homogeneous, lean base mixture.

The spin variable nozzle with return has proven to be a very flexible concept for actively influencing the

Beam parameters of a fuel injector proved. Not only is the adaptation of the injection parameters possible with existing methods. The design of new concepts consistently matched to the characteristics of the spin-variable injector may allow further improvement of the operating strategies of today's internal combustion engines by e.g. In gasoline engines with direct injection, the energy-efficient operating range with stratified charge is expanded.

When used in the BPI process, the spin-variable nozzle with return has already been able to show that this concept enables a new combustion process with a considerable potential for extending lean operation to a larger map range.

FIG. 14 shows geometric relationships of a preferred nozzle exit hole 11. In this case, the length I _{DL should be} at least twice as large as the diameter d _{DL of} the nozzle exit hole 11. Table 1: Possible operating modes of the spin-variable nozzle

Table 2: Parameters for the design of the swirl variable nozzle

Table 3: Characteristic ratios of the examined injector

Table 4: Operating parameters of the spin-variable nozzle

Claims

claims

1. A method for direct injection of fuel in reciprocating engines, wherein the fuel under increased pressure via at least one inlet (I,

II) is supplied to a spin-variable injection nozzle, in which a swirl chamber (7) is formed,

In a first phase, a basic mixture is injected into the cylinder, with the nozzle of the injection nozzle being opened and, at the same time, fuel being returned from the injection nozzle via a return line (10) or one of the inlets (I, II),

Subsequently, in a second phase, an ignition mixture is injected with the injection nozzle open and the return flow closed (10) and avoiding the backflow of fuel from the injection nozzle.

2. The method according to claim 1, characterized in that the base mixture is injected with a larger jet cone angle than the jet cone angle for ignition mixture.

3. The method according to claim 1 or 2, characterized in that the base mixture in the crank angle range minus 90 ° to 270 ° is injected.

4. Method according to one of the preceding claims, characterized in that a lambda value greater than 1 is maintained when the basic mixture is injected.

5. The method according to any one of the preceding claims, characterized in that ignition mixture is injected into a recess formed on the piston.

6. The method according to any one of the preceding claims, characterized in that ignition mixture is injected into the sphere of influence of an ignition device and / or a spark plug.

7. The method according to any one of the preceding claims, characterized in that the over

Inlets (I, II) supplied fuel mass is regulated.

8. The method according to any one of the preceding claims, characterized in that the base mixture and ignition mixture are injected within a working cycle.

9. The method according to any one of the preceding claims, characterized in that fuel from the inlets (I, II) in each case via at least two channels of the swirl chamber (7) of the injection nozzle is supplied.

10. The method according to any one of the preceding claims, characterized in that directly from the swirl chamber (7) back flowing fuel in the injection nozzle with a swirl provided the return line (10) is supplied.

11. The method according to claim 10, marked thereby, that with the from the swirl chamber (7) back flowing fuel a swirl column in a swirl return chamber (9) is formed.

12. The method according to any one of the preceding claims, characterized in that the return (10) is opened prior to the initiation of the first phase for injection of the basic mixture.

13. The method according to any one of the preceding claims, characterized in that the return (10) is closed before the initiation of the second phase for injection of the ignition mixture.

14. A device for carrying out the method according to one of claims 1 to 13, characterized in that an injection nozzle via at least one inlet (I, II) fuel in a

Swirl chamber (7) can be fed and the swirl chamber (7) with a nozzle outlet hole (11), which is temporarily closed with a nozzle needle (1) is connected; It can flow back into a tank (12) via at least one return channel fuel via a connected to the injection nozzle return (10) or one of the inlets (I, II) and at the return (10) or an inlet (I, II) a back flowing Fuel influencing

Control valve (12, 13) is present.

15. The apparatus according to claim 12, characterized in that the length of the nozzle outlet hole (11) is at least twice greater than the diameter of the nozzle outlet hole (11).

16. The apparatus of claim 12 or 13, characterized in that adjoins the swirl chamber (7) a swirl return chamber (9).

17. The apparatus according to claim 14, characterized in that the swirl return kairaner (9) is designed as an annular chamber around the nozzle needle (1).

18. Device according to claim 14 or 15, characterized in that swirl elements are formed on the swirl return chamber (9).

19. Device according to one of claims 14 to 16, characterized in that the height of the swirl return chamber (9) is greater than the height of a swirl chamber (7).

20. Device according to one of claims 12 to 17, characterized in that channels (2) and (3) are summarized in each case to channel groups (I) and (II).