DE102019125569B3 - Device and method for providing a water-fuel emulsion - Google Patents

Abstract

A device (10) for providing a water-fuel emulsion comprises a high pressure pump (12), a pressure chamber (26) and at least one ultrasonic unit (34) assigned to the pressure chamber (26), the pressure chamber (26) of the high pressure pump (12) is downstream. The pressure chamber (26) is in flow connection with the high pressure pump (12) in order to convey a water-fuel emulsion generated by the high-pressure pump (12) and / or a mixture of water and fuel to the pressure chamber (26). The pressure chamber (26) is larger in the longitudinal direction (L) than in a transverse direction (Q) perpendicular to the longitudinal direction (L). The at least one ultrasound unit (34) is attached to a side (36) of the pressure chamber (26) extending in the transverse direction (Q) and extends in the longitudinal direction (L) into the pressure chamber (26).
A method for providing a water-fuel emulsion is also specified.

Description

The invention relates to a device and a method for providing a water-fuel emulsion.

In the area of engine development, increasing the performance of the internal combustion engine and reducing exhaust gas are two of the most important target variables. One possibility for increasing performance and / or reducing exhaust gas is the use of water injection.

In the case of water injection, the engine is cooled, for example by injecting a water-fuel emulsion directly into the combustion chamber of an internal combustion engine.

By lowering the temperature, the areas of the engine characteristics map can be expanded in which a combustion air ratio λ of 1 is used, i.e. stoichiometric or complete combustion of the fuel takes place. This means that limit values for CO emissions can be adhered to under real vehicle conditions, i.e. outside the test cycles used in the approval process.

The combustion of a stoichiometric mixture of fuel and air generates higher temperatures than a rich mixture, i.e. a mixture that has a lack of air and thus a lack of oxygen. However, this higher temperature would cause excessively high NO _x emissions. The emission reduction would therefore have to take place in this case via a power reduction.

For this reason, the addition of water is necessary, which cools the mixture of fuel and air, whereby a sufficient reduction in exhaust gas can be achieved while maintaining the usual performance for the customer. This makes it possible to implement engines that have increased performance and / or lower emissions.

Accordingly, a water-fuel emulsion must be produced before the injection and injected into the internal combustion engine via injection nozzles. The water-fuel ratio of the emulsion obtained must always be adapted to the selected power window of the internal combustion engine. In addition, the quality, also known as the quality of the mixture or the quality of the emulsion, is crucial for optimizing the combustion process.

Since water and fuel do not combine to form a stable emulsion or mixture without further additives, delays between the production of the emulsion and the injection into the combustion chamber can result in partial or complete separation of the emulsion. This can cause problems when starting the engine, such as starting delays or water hammer.

The DE 10 2017 219 371 A1 discloses a device for feeding a liquid at risk of freezing into the combustion chambers of an internal combustion engine driving a motor vehicle, in particular, with a suction device which is designed to remove the liquid at risk of freezing from a wide area of a feed line through which the liquid passes from a storage container to a feed device for the internal combustion engine, suck off. In this case, a non-return valve, which opens in the direction of the conveying direction of the suction device and branches off from the feed line, is provided near the feed device, which, in the open state, connects the feed line with the environment. In the supply line, a pressure accumulator is provided for a certain amount of liquid under excess pressure, it being possible for the check valve to be provided on or in the pressure accumulator.

From the DE 10 2018 219 189 B3 a device and a method are known for operating an internal combustion engine that can be operated either with fuel or with a water-fuel emulsion, with a fuel tank for storing fuel, a water tank for storing water, a mixing device to which the fuel and water are supplied to form a water-fuel emulsion, a high-pressure fuel accumulator with a storage space for storing the fuel and the water-fuel emulsion, a high-pressure fuel pump that promotes the water-fuel emulsion to the high-pressure fuel accumulator when the internal combustion engine is equipped with a Water-fuel emulsion should be operated. According to the invention, the high-pressure fuel reservoir has a sound generating device which introduces sound waves into the storage space for the water-fuel emulsion of the high-pressure fuel reservoir.

The DE 10 2011 076 670 A1 discloses a device for providing a water-fuel emulsion comprising a high-pressure pump, a pressure chamber and at least one ultrasonic unit assigned to the pressure chamber, the pressure chamber being connected downstream of the high-pressure pump, the high-pressure pump comprising an outlet which is in flow communication with the pressure chamber to in the high pressure pump generated water-fuel emulsion and / or a mixture of water and fuel to the pressure chamber, wherein the pressure chamber is larger in the longitudinal direction than in a transverse direction perpendicular to the longitudinal direction, and wherein the at least one ultrasonic unit is attached to a transversely extending side of the pressure chamber.

The object of the invention is to create a possibility with which a water-fuel emulsion of sufficient quality can be provided reliably and in particular promptly.

The object is achieved by a device for providing a water-fuel emulsion, comprising a high-pressure pump, a pressure chamber and at least one ultrasonic unit assigned to the pressure chamber, the pressure chamber being connected downstream of the high-pressure pump. The high-pressure pump also includes a fuel inlet and a water inlet and an outlet that is in flow connection with the pressure chamber. The water-fuel emulsion generated in the high-pressure pump and / or a mixture of water and fuel can thus be passed into the pressure chamber. The pressure chamber is larger in a longitudinal direction than in a transverse direction perpendicular to the longitudinal direction and the at least one ultrasound unit is attached to a side of the pressure chamber extending in the transverse direction and extends in the longitudinal direction into the pressure chamber.

The ultrasound unit arranged inside the pressure chamber serves to maintain the emulsion quality of the water-fuel emulsion introduced into the pressure chamber, to produce a water-fuel emulsion from a mixture of water and fuel introduced into the pressure chamber and / or, in the case of longer idle times, the can lead to the separation of the phases of water and fuel.

Such ultrasonic units are also known by the term sonotrode and have at least one front surface that can be set into high-frequency mechanical vibrations. These vibrations can then be transmitted as sound waves into the medium surrounding the ultrasonic unit, in this case into the water-fuel emulsion and / or the mixture of water and fuel. The components of the medium are blended or mixed with one another by the sound waves, so that in the present case a water-fuel emulsion of sufficient emulsion quality results.

The ultrasonic unit thus serves to introduce energy into the water-fuel emulsion or into the mixture of water and fuel. For this purpose, such ultrasonic units only have a low energy consumption and at the same time are available in a compact design.

In other words, with the device according to the invention, it is possible to ensure adequate mixing of the two components even after the original mixing of water and fuel. In this way, a first thorough mixing by the high-pressure pump can take place without the risk of a partially or completely separated water-fuel emulsion in the event of time delays between production of the emulsion and injection into an internal combustion engine connected to the pressure chamber, in particular the combustion chamber of an engine is injected. In addition, the high pressure pump does not have to provide sufficient emulsion quality on its own, so that the design of the high pressure pump is simplified. This allows the costs to be reduced accordingly.

Delays can arise from the transport of the water-fuel emulsion between the high pressure pump and the pressure chamber as well as from the transport within the pressure chamber. A delay can also refer to the period between a stop and the restart of the internal combustion engine, for example in the case of an automatic start and stop.

Usual pressure chambers are elongated, i.e. the longitudinal direction of the pressure chamber is larger than a transverse direction perpendicular to the longitudinal direction. Attaching the ultrasound unit to a side of the pressure chamber that extends in the transverse direction, ie perpendicular to the longitudinal direction, results in a particularly simple possibility of attaching the ultrasound unit within the pressure chamber. In addition, a good transmission of the vibrations of the ultrasound unit into the medium within the pressure chamber is made possible.

Due to the elongated shape, in particular an elongated and cylindrical shape, of the pressure chambers, the sides of the pressure chamber extending in the transverse direction are particularly suitable for attaching the pressure sensor, for example by means of a screw connection. In this case, a pressure sensor can be attached to the side opposite the ultrasound unit, for example likewise via a screw connection. The pressure sensor is used to monitor the pressure inside the pressure chamber.

A fuel tank and a water tank, which provide the two components for producing the water-fuel emulsion by the high-pressure pump, can be connected to the high-pressure pump.

The fuel can also include ethanol.

The pressure chamber can have an inlet via which the pressure chamber receives the water-fuel emulsion and / or the mixture of water and fuel from a supply line of the high-pressure pump. A simple transfer of the water-fuel emulsion and / or mixture of water and fuel generated by the high-pressure pump into the pressure chamber is thus possible.

In one embodiment, the pressure chamber is assigned at least one injection nozzle which is set up to remove the water-fuel emulsion from the pressure chamber. In particular, the injection nozzle is connected to a combustion chamber of an internal combustion engine. This enables the water-fuel emulsion produced with the desired emulsion quality to be injected into the internal combustion engine via the injection nozzle. The water-fuel emulsion is accordingly removed from the pressure chamber in that the water-fuel emulsion is injected into the internal combustion engine.

By generating the uniform water-fuel emulsion, optimal operation and clean combustion within the internal combustion engine can be ensured.

The at least one injection nozzle can be assigned to a side of the pressure chamber extending in the longitudinal direction. Accordingly, the at least one injection nozzle has an orientation which is perpendicular to the orientation of the ultrasound unit. In this way, the attachment of the ultrasound unit does not limit the areas of the pressure chamber available for attachment of injection nozzles.

In addition, a plurality of injection nozzles can be provided along the side of the pressure chamber extending in the longitudinal direction. In this case, the pressure chamber is a so-called common rail.

In such a configuration, the device according to the invention enables a uniform emulsion quality to be achieved over the entire length of the pressure chamber. In this case, the operation of the ultrasonic unit can be regulated in such a way that differences in the quality of the emulsion due to different periods of time between mixing in the high-pressure pump and injection through a specific injection nozzle are compensated for. The device according to the invention thus also serves to synchronize the injection and to operate the common rail evenly.

The at least one ultrasound unit can taper from the side of the pressure chamber to a front surface pointing into the interior of the pressure chamber. In this way, a particularly simple assembly of the ultrasonic unit within the pressure chamber is possible with little space requirement. In addition, such ultrasonic units are available inexpensively.

In order to further increase the intermixing perpendicular to the direction of extent of the at least one ultrasonic unit, a thickening can be formed on the front surface of the at least one ultrasonic unit.

In a further embodiment, the device comprises two ultrasonic units, with a second ultrasonic unit being attached to a side of the pressure chamber opposite to the first ultrasonic unit. The water-fuel emulsion and / or mixture of water and fuel present within the pressure chamber is thus mixed evenly from both sides. An even more uniform water-fuel emulsion can be obtained in this way. Furthermore, the device is designed redundantly so that a uniform water-fuel emulsion can continue to be generated even if an ultrasonic unit should fail. In such an embodiment, a possibly required pressure sensor is attached in particular at a position outside the sides of the pressure chamber.

Starting from the side of the pressure chamber assigned to it, the second ultrasound unit can also taper towards the first ultrasound unit, that is to say likewise along the side of the pressure chamber that extends in the longitudinal direction. This means that only a small amount of installation space is required within the pressure chamber for the second ultrasonic unit.

1. a) Bereitstellen einer Vorrichtung der zuvor beschriebenen Art;
2. b) Einspeisen der Wasser-Kraftstoff-Emulsion und/oder des Gemischs aus Wasser und Kraftstoff in die Druckkammer über die Hochdruckpumpe; und
3. c) Herstellen der gleichmäßigen Wasser-Kraftstoff-Emulsion durch Erzeugen von Schallwellen innerhalb der Druckkammer mittels der zumindest einen Ultraschalleinheit.

The object is also achieved by a method for providing a water-fuel emulsion, comprising the following steps:

1. a) providing a device of the type described above;
2. b) feeding the water-fuel emulsion and / or the mixture of water and fuel into the pressure chamber via the high-pressure pump; and
3. c) Producing the uniform water-fuel emulsion by generating sound waves within the pressure chamber by means of the at least one ultrasonic unit.

By means of the at least one ultrasonic unit, the quality of the emulsion can be increased accordingly or an emulsion can be generated at all. At the same time, the emulsion is also distributed within the pressure chamber by the generated sound waves.

The sound waves are generated in particular with a frequency in the range from 10 to 20 kHz. Such frequencies ensure thorough mixing and can be reliably generated with inexpensive ultrasonic units. The frequency range used in each case can be adapted depending on the ultrasonic unit used and the water-fuel emulsion used or the mixture of fuel and water used.

The amplitude of the generated sound waves can be adapted to the density and / or the temperature of the water-fuel emulsion or the mixture of fuel and water used. This enables particularly efficient operation of the at least one ultrasonic unit.

Between the above-mentioned steps b) and c), i.e. between feeding in an emulsion or a mixture and producing the uniform emulsion, and / or between step c), i.e. producing the emulsion, and injecting the water-fuel Emulsion can be a period of more than 30 seconds, in particular more than 5 minutes.

Correspondingly, the method according to the invention ensures that the water-fuel emulsion injected into the internal combustion engine has a sufficient emulsion quality even when delays occur. In particular, the water-fuel emulsion is also produced immediately after the internal combustion engine has been started, so that partial or complete separation of the components of the water-fuel emulsion can be remedied immediately.

At the same time, the emulsion quality of the water-fuel emulsion produced under step c) can be so high that sufficient emulsion quality is guaranteed even with slight delays between the production and the injection of the water-fuel emulsion.

In principle, if necessary, step c) can also be repeated (several times) if the delays up to the injection of the water-fuel emulsion become too long.

• - 1 eine schematische Darstellung einer erfindungsgemäßen Vorrichtung zum Bereitstellen einer Wasser-Kraftstoff-Emulsion,
• - 2 eine Seitenansicht einer Druckkammer der Vorrichtung aus 1,
• - 3 eine Draufsicht auf die Druckkammer aus 2,
• - 4 eine Schnittansicht der Druckkammer aus 2,
• - 5 die Schnittansicht der Druckkammer aus 4 während des Betriebs einer Ultraschalleinheit,
• - 6 eine alternative Ausführungsform der Ultraschalleinheit aus 5,
• - 7 eine schematische Darstellung des erfindungsgemäßen Verfahrens,
• - 8 eine Seitenansicht einer zweiten Ausführungsform der Druckkammer aus 1,
• - 9 eine Draufsicht auf die Druckkammer aus 8,
• - 10 eine Schnittansicht der Druckkammer aus 8, und
• - 11 die Schnittansicht der Druckkammer aus 10 während des Betriebs der Ultraschalleinheiten.

Further features and advantages of the invention emerge from the following description and from the accompanying drawings, to which reference is made. In these show:

• - 1 a schematic representation of a device according to the invention for providing a water-fuel emulsion,
• - 2 a side view of a pressure chamber of the device 1 ,
• - 3 a top view of the pressure chamber 2 ,
• - 4th a sectional view of the pressure chamber 2 ,
• - 5 the sectional view of the pressure chamber 4th during operation of an ultrasound unit,
• - 6th an alternative embodiment of the ultrasound unit 5 ,
• - 7th a schematic representation of the method according to the invention,
• - 8th a side view of a second embodiment of the pressure chamber 1 ,
• - 9 a top view of the pressure chamber 8th ,
• - 10 a sectional view of the pressure chamber 8th , and
• - 11 the sectional view of the pressure chamber 10 during operation of the ultrasonic units.

In 1 is a device according to the invention 10 for providing a water-fuel emulsion shown.

The device 10 includes a high pressure pump 12 . To a fuel inlet 14th the high pressure pump 12 is a fuel tank 16 and to a water inlet 18th the high pressure pump 12 a water tank 20th connected.

The high pressure pump 12 stands over an exit 22nd by means of a supply line 24 with a pressure chamber 26th in flow connection, the supply line 24 to an inlet 28 the pressure chamber 26th connected.

The pressure chamber 26th is also connected to several injection nozzles 30th connected to an internal combustion engine 32 are in flow connection. At the pressure chamber 26th it is accordingly a so-called common rail.

The internal combustion engine 32 is in particular an engine of a motor vehicle.

Inside the pressure chamber 26th is an ultrasound unit 34 arranged the sound waves in one inside the pressure chamber 26th present medium can generate.

The pressure chamber 26th has an elongated shape. Accordingly, the pressure chamber 26th a longitudinal direction L which is greater than a transverse direction Q perpendicular to the longitudinal direction L.

The ultrasound unit 34 is a side extending in the transverse direction Q. 36 the pressure chamber 26th arranged and protrudes into the interior of the pressure chamber 26th in, as out 1 already becomes clear.

In 2 Figure 13 is a side view and in 3 Figure 3 is a top plan view of a first embodiment of the pressure chamber 26th shown.

The pressure chamber 26th points next to the inlet 28 several connecting pieces 40 on. The connecting pieces 40 are used, for example, to connect pressure sensors via which the in the pressure chamber 26th existing pressure can be transmitted to a (not shown) control and / or regulating unit.

In the embodiment shown, there are a total of four outlet nozzles 42 provided, each with one of the injection nozzles 30th ( 1 ) are connected. In principle, however, fewer or more outlet nozzles can also be used 42 and injection nozzles 30th be provided.

The outlet ports 42 are distributed along the longitudinal direction L of the pressure chamber 26th appropriate.

The pressure chamber 26th also indicates at the in 2 page shown on the left 36 a broadening 44 on that to accommodate the ultrasound unit 34 serves.

This is done in 4th illustrates, which is a sectional view along a plane of the in 3 indicated line AA shows.

The ultrasound unit 34 fills that by widening 44 created receiving space (substantially) completely and extends along the longitudinal direction L into the interior of the pressure chamber 26th inside. The ultrasound unit tapers in the process 34 towards a front surface 46 . The front surface 46 is on the front of the ultrasound unit 34 provided to the interior of the pressure chamber 26th is facing.

In the embodiment shown, the ultrasound unit 34 furthermore a cylindrical cross section, in particular a cylindrical cross section stepped over its longitudinal extension. In other words, the ultrasound unit is tapered 34 to the front surface 46 not continuously, but also at least partially in steps, as is clear from the figures.

Starting from the front surface 46 can the ultrasound unit 34 Sound waves 48 inside the pressure chamber 26th generate, as in 5 clarified.

In 6th is an alternative embodiment of the ultrasound unit 34 shown in which the front surface 46 a thickening 49 having. By the thickening 49 the cross-section of the ultrasound unit widens 34 . In other words, it is the face of the ultrasound unit 34 widened. This enables even better mixing within the pressure chamber 26th be achieved.

The method according to the invention for providing a water-fuel emulsion is explained below.

First the device 10 provided, for example, in the 1 to 5 is shown (step S1 in 7th ), the ultrasound unit 34 as in 6th may be formed shown.

To operate the device 10 is via the high pressure pump 12 a water-fuel emulsion by mixing fuel from the fuel tank 16 and water from the water tank 20th generated.

This is done by the high pressure pump 12 via the supply line 24 into the pressure chamber 26th fed in (step S2 in 7th ).

If the water-fuel emulsion is not fed in directly via one of the injection nozzles 30th in the internal combustion engine 32 injected, partial or complete separation of the water-fuel emulsion can occur, for example after a period of more than 30 seconds, in particular after a period of more than 5 minutes.

One such case is in 4th shown in the inside of the pressure chamber 26th a mixture 50 consists of water and fuel.

In the example shown, the water forms larger, circular spheres that are distributed within the fuel or within the remaining water-fuel emulsion. This behavior is also known as flocculation.

Depending on the extent of the original mixing of the water-fuel emulsion, the service life and temperatures, the two components fuel and water can also completely separate. In this case, due to its higher density than fuel, the water collects at the bottom and the fuel at the top, so that a horizontal interface is formed. This process is also known as “breaking” the emulsion.

Complete segregation is particularly important in the case of long delays between feeding in and removing the water-fuel emulsion from the pressure chamber 26th expected. Such a case can occur when the internal combustion engine 32 is restarted after a longer standstill or already with an automatic start and stop and a correspondingly long standstill phase, for example in a traffic jam or at a long red phase of a traffic light system.

If the water-fuel emulsion also has ethanol, it can happen that the water-fuel emulsion does not separate completely even after a long period of time. Nonetheless, uneven distributions can occur within this water-fuel emulsion, for example due to differences in density of the components of the water-fuel emulsion. In this case, it is desirable to mix the water-fuel emulsion again in order to ensure a sufficient quality of the emulsion.

By generating sound waves 48 by means of the ultrasound unit 34 it is possible from the mixture 50 or from a water-fuel emulsion of poor emulsion quality a uniform water-fuel emulsion 52 with high emulsion quality. This is in 5 shown as an example.

In particular, there are sound waves 48 used in a frequency range of 10 to 20 kHz, the exact frequency band and the amplitude of the sound waves 48 depending on the composition, the density and / or the temperature of the mixture 50 or the water-fuel emulsion of low emulsion quality is selected.

The emulsion quality of the water-fuel emulsion 52 can be so high that regardless of which outlet port 42 the water-fuel emulsion 52 from the pressure chamber 26th is removed, the emulsion quality is the same. In this respect, there is a uniform emulsion quality over the entire pressure chamber 26th in front.

The ultrasound unit 34 can also be used to pass through the inlet 28 water-fuel emulsion fed into the pressure chamber 26th to distribute evenly.

In the 8th to 11 is a second embodiment of the pressure chamber 26th shown. The second embodiment of the pressure chamber 26th corresponds essentially to the first embodiment, so that only the differences will be discussed below. Identical and functionally identical parts are provided with the same reference symbols.

In the second embodiment, the pressure chamber 26th at both ends, ie both on the side 36 as well as on the opposite side 43 each one widening 44 on. This is done on both sides 36 , 43 one ultrasonic unit each 34 , 54 inside the pressure chamber 26th to attach, the second ultrasound unit 54 on the one to the first ultrasound unit 34 opposite side of the pressure chamber 26th is appropriate. The front sides or front surfaces 46 of the two ultrasound units 34 , 54 are facing each other or are facing each other.

The second ultrasound unit 54 tapers to the first ultrasound unit 34 down.

The two ultrasound units 34 , 54 are constructed identically in the embodiment shown. Of course, the two ultrasound units could 54 however also differ from each other.

The use of two ultrasound units 34 ensures a further increase in the emulsion quality within the pressure chamber 26th by means of sound waves 48 produced water-fuel emulsion 52 .

In addition, a system redundancy is created, whereby the device 10 is more fail-safe overall.

Claims (12)

Device for providing a water-fuel emulsion (52), comprising a high-pressure pump (12), a pressure chamber (26) and at least one ultrasonic unit (34) assigned to the pressure chamber (26), the pressure chamber (26) of the high-pressure pump (12) is connected downstream, wherein the high pressure pump (12) comprises a fuel inlet (14) and a water inlet (18) and an outlet (22) which is in flow connection with the pressure chamber (26) in order to generate the water generated in the high pressure pump (12) To conduct fuel emulsion (52) and / or a mixture (50) of water and fuel to the pressure chamber (26), the pressure chamber (26) being larger in a longitudinal direction (L) than in a direction perpendicular to the longitudinal direction (L) Transverse direction (Q), and wherein the at least one ultrasound unit (34) is attached to a side (36) of the pressure chamber (26) extending in the transverse direction (Q) and extends in the longitudinal direction (L) into the pressure chamber (26) extends. Device according to Claim 1 , characterized in that the pressure chamber (26) has an inlet (28) through which the pressure chamber (26) the water-fuel emulsion (52) and / or the mixture (50) of water and fuel from a supply line (24) of the high pressure pump (12). Device according to Claim 1 or 2 , characterized in that the pressure chamber (26) is assigned at least one injection nozzle (30) which is set up to remove the water-fuel emulsion (52) from the pressure chamber (26). Device according to Claim 3 , characterized in that the at least one injection nozzle (30) is assigned to a side of the pressure chamber (26) extending in the longitudinal direction (L). Device according to one of the preceding claims, characterized in that the at least one ultrasonic unit (34) tapers starting from the side (36) of the pressure chamber (26) to a front surface (46) pointing into the interior of the pressure chamber (26). Device according to Claim 5 , characterized in that a thickening (49) is formed on the front surface (46) of the at least one ultrasonic unit (34). Device according to one of the preceding claims, characterized in that the device (10) comprises two ultrasonic units (34, 54), a second ultrasonic unit (54) on a side (43) of the pressure chamber (26) opposite to the first ultrasonic unit (34). is appropriate. Device according to Claim 7 , characterized in that the second ultrasonic unit (54) tapers starting from the side (43) of the pressure chamber (26) assigned to the second ultrasonic unit (54) towards the first ultrasonic unit (34). A method for providing a water-fuel emulsion (52) comprising the following steps: a) providing a device (10) according to one of the preceding claims; b) feeding the water-fuel emulsion (52) and / or the mixture (50) of water and fuel into the pressure chamber (26) via the high-pressure pump (12); and c) producing the uniform water-fuel emulsion (52) by generating sound waves (48) within the pressure chamber (26) by means of the at least one ultrasonic unit (34). Procedure according to Claim 9 , characterized in that the sound waves (48) are generated with a frequency in the range of 10 to 20 kHz. Procedure according to Claim 9 or 10 , characterized in that the amplitude of the generated sound waves (48) is adapted to the density and / or the temperature of the water-fuel emulsion (52) and / or the mixture (50) of water and fuel. Method according to one of the Claims 9 to 11 , characterized in that between steps b) and c) and / or between step c) and an injection of the water-fuel emulsion (52) there is a period of more than 30 seconds.

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