EP2444161B1 - Atomizing nozzle for two substances - Google Patents

Description

The invention relates to a two-component atomizing nozzle for spraying a liquid with the aid of a compressed gas having a mixing chamber, a liquid inlet opening into the mixing chamber, a compressed gas inlet opening into the mixing chamber and an outlet opening downstream of the mixing chamber, wherein an annular gap surrounding the outlet opening is provided for the exit of compressed gas and wherein the outlet opening is formed by means of a circumferential wall, whose extreme end forms an outlet edge, and wherein the annular gap is arranged in the region of the outlet edge.

From the international patent publication WO 2004/096446 is a generic Zweistoffzerstäubungsdüse known. A convection gas jet emerges from a gap surrounding the outlet opening of the nozzle in order to prevent a gas-droplet jet issuing from the outlet opening of the nozzle from being decelerated. In the exit of the nozzle, the initial diameter of the gas-droplet jet and the diameter of the convection gas jet should differ greatly. The objective of the two-component atomizing nozzle described therein is to prevent a deceleration of the gas-droplet jet to a certain distance by means of the convection gas jet so as to increase the range of the gas-droplet jet.

From the German patent application DE 200 59 27 is a two-fluid nozzle is known in which first a tubular flow profile is to be formed within the nozzle, wherein in the interior of the tubular airfoil, the air is guided. The tubular flow profile is achieved by introducing a partial flow into the liquid passage of the nozzle, said partial flow of the air after generating the tubular flow profile is then guided into its interior. Compressed gas should escape from an annular space in the region of the outlet opening, which then breaks up the walls of the tube-like flow profile produced in drops. The two-fluid nozzle described thus represents a two-fluid nozzle with external mixing, since a decomposition of the drops takes place only outside the nozzle.

In the US patent US 1,451,063 an oil burner nozzle is described in which oil is to be atomized with the aid of compressed air. The described nozzle has a mixing zone, in whose wall numerous air outlet openings are provided. The air outlet openings in the inner wall surrounding the mixing zone prevent the formation of a liquid film on this inner wall.

In many process plants, liquids are distributed in a gas. It is often of crucial importance that the liquid is sprayed in fine drops as possible. The finer the drops, the larger the specific drop surface. This can result in considerable procedural advantages. For example, the size of a reaction vessel and its manufacturing costs are significantly dependent on the average droplet size. But in many cases it is by no means sufficient for the mean drop size to fall below a certain limit. Even a few much larger drops can lead to significant disruption. This is especially the case if the drops do not evaporate fast enough due to their size, so that even drops or even doughy particles in subsequent components, e.g. on fabric filter hoses or fan blades, and cause malfunction due to incrustation or corrosion.

To spray liquids finely, either high-pressure single-fluid nozzles or medium-pressure twin fluid nozzles are used. An advantage of two-fluid nozzles is that they have relatively large flow cross-sections have, so that even coarse particle-containing liquids can be sprayed.

The presentation of the Fig. 1 shows a dual-fluid nozzle with internal mixing according to the prior art. A fundamental problem with such nozzles results from the fact that the walls of the mixing chamber 7 are wetted with liquid. The liquid which wets the wall in the mixing chamber 7 is driven by the shear stress and pressure forces as liquid film 20 to the nozzle mouth. It is tempting to assume that the walls are blown dry towards the nozzle mouth due to high flow velocity of the gas phase and that only very fine droplets are formed from the liquid film. However, the theoretical and experimental work of one of the inventors, see the attached bibliography, has shown that liquid films on walls can still exist as stable films without dripping even when the gas flow which drives the liquid films to the nozzle orifice reaches supersonic speed. And this is also the reason why it is possible to use liquid film cooling in rocket thrusters.

The liquid films 20, which are driven by the gas flow to the nozzle orifice 8, can even move around a sharp edge on the nozzle orifice due to the adhesive forces. They form a water bead 12 on the outside of the nozzle orifice 8. From this water bead 12, edge drops 13 detach whose diameter is a multiple of the mean diameter of the drops in the jet core or core jet 21. And although these large edge drops contribute only a small mass fraction, they are ultimately determinative of the dimensions of a container in which, for example, the temperature of a gas to be lowered by evaporative cooling from 350 ° C to 120 ° C, without causing an entry of drops in a downstream fan or downstream fabric filter comes.

In the in Fig. 1 A nozzle according to the prior art, a liquid is introduced parallel to a central longitudinal axis 24 in the direction of arrow 1. The liquid is passed through a lance tube 2 extending concentrically to the central longitudinal axis 24 and enters a mixing chamber 7 at a liquid inlet 10. The lance tube 2 and the mixing chamber 7 are concentrically surrounded by an annular chamber 6, which is formed by means of a further lance tube 4 for the supply of the compressed gas to the two-fluid nozzle. In this annular chamber 6 compressed gas is introduced according to the arrow 15. A with respect to the central longitudinal axis 24 radial peripheral wall of the mixing chamber 7 has a plurality of compressed gas inlets 5, which are arranged radially to the central longitudinal axis 24. Through these compressed gas inlets 5, compressed gas can enter the mixing chamber 7 at right angles to the liquid jet entering through the liquid inlet 10, so that a liquid / air mixture is formed in the mixing chamber 7. Adjoining the mixing chamber 7 is a frusto-conical constriction 3, which forms a convergent outlet section, followed by a frustum-shaped extension 9 after a narrowest cross section 14, which forms a divergent outlet section. The frusto-conical enlargement 9 ends at the outlet opening or the nozzle mouth 8.

With the invention, a Zweistoffzerstäubungsdüse be provided, in which a uniformly fine droplet spectrum can be achieved both in the edge region and in the jet core.

According to the invention, a two-component atomizing nozzle is provided for spraying a liquid with the aid of a compressed gas with a mixing chamber, a liquid inlet opening into the mixing chamber, a pressurized gas inlet opening into the mixing chamber and an outlet opening downstream of the mixing chamber, an annular gap surrounding the outlet opening for exiting high-pressure compressed gas Speed is provided, with the outlet opening is formed by a circumferential wall, the extreme end of which forms an outlet edge and wherein the annular gap is arranged in the region of the outlet edge, wherein the mixing chamber, the liquid inlet and the compressed gas inlet are formed and arranged such that a liquid film on the wall of the nozzle mouth exists and the Annular gap and the trailing edge are formed so that the compressed gas exits directly in the region of the trailing edge at high speed from the annular gap and the liquid film at the trailing edge to a very thin liquid lamella and then breaks this up into fine droplets.

By providing the annular gap surrounding the outlet opening, which is acted upon by atomizing gas, for example air or steam, a liquid film on the wall of the nozzle mouth, in particular of the divergent outlet portion is pulled out to a very thin liquid lamella which disintegrates into small drops. In this way, the formation of large drops of wall liquid films in the nozzle exit region can be prevented or reduced to an acceptable level and at the same time the fine droplet spectrum in the jet core can be obtained without the need to increase the pressure gas consumption of the two-fluid nozzle or the associated own energy demand. Experimental investigations by the inventors have shown that by providing an annular gap, the maximum droplet size can be reduced to about one third with the same expenditure of energy. This may be considered a minor effect. It should be noted, however, that the volume of a drop having a diameter reduced by a factor of three is only one-seventeenth of a large drop. Without entering into the well-known relationships, it should be clear to the person skilled in the art that this results in considerable advantages in terms of the required construction volume of evaporative coolers or resulting from sorption eg for the flue gas cleaning. With the additional annular gap atomization, therefore, a much finer droplet spectrum can be generated with the same expenditure of energy. Advantageously the annular gap air quantity 10% to 40% of the total atomizing air quantity. In process engineering plants, in which is injected into containers or channels, which are approximately at the pressure of the environment (1bar), the total pressure of the air in the annular gap is advantageously 1.5 bar to 2.5 bar absolute. The total pressure of the air in the annular gap would advantageously have to be so high that, when expanding to the pressure level in the vessel, approximately sound velocity is achieved.

The compressed gas emerging from the annular gap at high speed can escape directly in the region of the outlet edge and thereby reliably ensure that a liquid film is drawn out at the nozzle mouth to form a very thin liquid lamella, which is then divided into fine droplets.

In a development of the invention, the annular gap is formed between the outlet edge and an outer annular gap wall.

In this way, the trailing edge itself can be used to form the annular gap. This simplifies the structure of the two-component atomizing nozzle according to the invention.

In a further development of the invention, an outer end of the annular gap wall is formed by an annular gap wall edge and the annular gap wall edge is arranged in the outflow direction after the trailing edge. Advantageously, the annular gap wall edge is arranged between 5% and 20% of the diameter of the outlet opening to the outlet edge.

In this way, the formation of coarse drops of liquid at the boundary of the outlet opening can be prevented particularly reliably.

In a further development of the invention, control means and / or at least two compressed gas sources are provided, so that a pressure of the compressed gas supplied to the annular gap and a pressure of the compressed gas opening into the mixing chamber through the compressed gas inlet can be set independently of one another.

Separate pipes for pressurizing the mixing chamber and for pressurizing the annular gap with compressed gas offer advantages in that the pressure in a gap air chamber upstream of the annular gap is then independent of the pressure of the atomizing gas, which is supplied to the mixing chamber, can be specified. This is then in view of the own energy requirement of importance when compressors with different back pressure or steam networks with matching different pressures in a system are available. In general, however, only a compressed gas network with a single pressure will be available. In this case, for example, pressure reducers can be used. When supplying the annular gap via a separate line with compressed gas, the annular gap air volume is adjusted via separate valves, regardless of the core jet air quantity, which is introduced into the mixing chamber.

In a further development of the invention, the mixing chamber is at least partially surrounded by an annular chamber for supplying the compressed gas, and a gap air chamber connected upstream of the annular gap is in flow communication with the annular chamber.

If only a single pressure gas network is available, it is necessary to remove the atomizing gas supplied to the same gap in the annular gap. The configuration of the two-component atomizing nozzle can then be simplified by removing the atomizing gas supplied to the annular gap from the annular space from which the mixing chamber is supplied with atomizing gas. By suitable dimensioning of the flow connection between the annular chamber and the gap air chamber, the energy requirement of the nozzle according to the invention can be minimized. The flow connection is formed, for example, by means of bores in a partition wall between annular chamber and gap air chamber, which are suitable to be dimensioned in cross-section, also in relation to the bores forming a compressed gas inlet into the mixing chamber.

In a further development of the invention, an outlet opening and the annular gap at least partially surrounding Schleierluftdüse is provided.

The provision of a Schleierluftdüse leads to a further improvement of the spray pattern of the Zweistoffzerstäubungsdüse according to the invention, in particular backflow vortex can be avoided by which drops and dust-containing gas are mixed together and lead to disturbing deposits on the nozzle mouth.

In a development of the invention, the veiling air nozzle has a void air ring gap surrounding the outlet opening and the annular gap, whose outlet area is much larger than an exit area of the annular gap. Advantageously, the Schleierluftdüse is fed with compressed gas, the pressure of which is substantially lower than a pressure of the annular gap supplied compressed gas.

In this way, the Schleierluftdüse, which surrounds the nozzle mouth annular, energy-saving be subjected to low pressure air. This is very important because the Schleierluftringspalt the Schleierluftdüse to avoid a backflow vortex must be sized much larger than the annular gap for liquid film atomization.

In a development of the invention, means are provided for imparting a twist about a central longitudinal axis of the nozzle to a mixture of compressed gas and liquid in the mixing chamber.

The fact that it is possible with the Zweistoffzäubäubdüse invention by the additional annular gap atomization, the liquid film that exists in the nozzle exit part on the inner wall to spray on the nozzle mouth to small drops, there are more interesting starting points for the nozzle design. In particular, it is hereby permissible to impart a twist to the two-phase flow in the mixing chamber and thus also in the outlet part of the nozzle. As a result, a few more drops are thrown onto the inner wall of the outlet part. But this is not harmful because of the very efficient annular gap atomization. An advantage of the twisting is that a twisted flow in the mixing chamber and in the outlet part tends to be centrically symmetrical. This can hardly be achieved with conventional two-substance nozzles with internal mixing and has hitherto led to the fact that in particular at the nozzle mouth, in particular, many large drops have been formed. As a result, the mean droplet size can be significantly reduced by twisting the core beam.

In a further development of the invention, the compressed gas inlet has at least one first inlet bore opening into the mixing chamber, which is oriented tangentially to a circle about a central longitudinal axis of the nozzle in order to generate a twist in a first direction.

By providing tangential inlet bores, a swirl can be generated in the mixing chamber in a simple and less clog-sensitive manner.

In a further development of the invention, a plurality of, in particular four, first inlet bores are provided in a first plane perpendicular to the central longitudinal axis and spaced apart in the circumferential direction.

By uniformly spaced arrangement of such tangential inlet bores, a significant twist in the mixing chamber can be achieved.

In a further development of the invention, at least one second inlet bore, which is aligned tangentially to a circle about the central longitudinal axis of the nozzle to generate a twist in a second direction, is provided parallel to the central longitudinal axis of the first inlet bore.

In this way, opposing swirl directions can be impressed in the mixing chamber in the different levels of the inlet or Zuluftbohrung. By opposite directions of twisting strongly pronounced shear layers are generated in the mixing chamber, which contribute to the formation of very fine drops.

In a further development of the invention, a plurality of, in particular four, second inlet bores are provided in a second plane perpendicular to the central longitudinal axis and spaced apart in the circumferential direction.

In a development of the invention, at least three planes spaced apart parallel to the central longitudinal axis are provided with inlet bores, the inlet bores of successive planes generating an oppositely directed twist.

For example, a counted from the liquid inlet forth first level left-hand inlet holes, the second level right-handed inlet holes and the third level again left-handed inlet holes. Due to the opposite directions of twist, pronounced shear layers are produced in the mixing chamber, which contribute to the formation of particularly fine drops.

Fig. 1

eine Zweistoffzerstäubungsdüse gemäß dem Stand der Technik,

Fig. 2

eine Zweistoffzerstäubungsdüse gemäß einer ersten Ausführungsform der Erfindung,

Fig. 2a

eine vergrößerte Einzelheit der Fig. 2,

Fig. 3

eine Schnittansicht einer Zweistoffzerstäubungsdüse gemäß einer zweiten bevorzugten Ausführungsform der Erfindung,

Fig. 4

eine abschnittsweise Schnittansicht der Düse der Fig. 2, in der unterschiedliche Schnittebenen markiert sind,

Fig. 5

eine Schnittansicht auf die Ebene I der Fig. 4,

Fig. 6

eine Schnittansicht auf die Ebene II der Fig. 4 und

Fig. 7

eine Schnittansicht auf die Ebene III der Fig. 4.

Further features and advantages of the invention will become apparent from the claims and the following description of preferred embodiments in conjunction with the drawings. In this case, individual features of the individual embodiments illustrated can be combined with one another in any desired manner, without exceeding the scope of the invention. In the drawings show:

Fig. 1

a two-part atomizing nozzle according to the prior art,

Fig. 2

a two-part atomizing nozzle according to a first embodiment of the invention,

Fig. 2a

an enlarged detail of Fig. 2 .

Fig. 3

a sectional view of a two-atomizing nozzle according to a second preferred embodiment of the invention,

Fig. 4

a sectional sectional view of the nozzle of Fig. 2 in which different cutting planes are marked,

Fig. 5

a sectional view on the level I of Fig. 4 .

Fig. 6

a sectional view on the level II of Fig. 4 and

Fig. 7

a sectional view of the level III of Fig. 4 ,

The sectional view of Fig. 2 shows a Zweowoffzerstäubungsdüse 30 according to the invention according to a first preferred embodiment. The Zweistoffzäubäubdüse 30 according to the invention, at least as regards the introduction of the liquid and the compressed gas into the mixing chamber and the shape of the nozzle subsequent to the mixing chamber, similar to the known nozzle according to Fig. 1 built up. A liquid to be atomized is fed in the direction of an arrow 32 via an inner lance tube 34 running parallel to a central longitudinal axis 36 of the nozzle 30 and reaches a liquid inlet 38, which has a reduced cross-section with respect to the tube 34. After passing through the liquid inlet 38, the liquid then passes in the form of a concentric to the central longitudinal axis 36 extending liquid jet in the cylindrical and concentric with the central longitudinal axis 36 arranged mixing chamber 40. The tube 34 and the mixing chamber 40 are surrounded by an annular chamber 42, which through the gap between a outer lance tube 43 and the inner lance tube 34 is formed and in the direction of an arrow 44 pressurized gas, such as compressed air, is introduced. A concentric with the central longitudinal axis 36 extending peripheral wall of the mixing chamber 40 has a plurality of inlet openings 46a, 46b, 46c, all together form a compressed gas inlet into the mixing chamber 40, so for supplying the so-called core air. The compressed gas inlet openings 46 are arranged offset in the direction of the central longitudinal axis 36 as well as in the circumferential direction. As a result, compressed gas is introduced into the mixing chamber 40 in different layers. The exact arrangement of the compressed gas inlet openings 46 will be described below with reference to the Fig. 4 to 7 explained.

Subsequent to the mixing chamber 40, a frusto-conical constriction 48 is provided, which forms a convergent outlet part and which, after passing through a narrowest cross-section, again merges into a frusto-conical enlargement with a smaller opening angle, which forms a divergent outlet part. The divergent exit part terminates at an exit opening 52 or a nozzle mouth. The outlet opening 52 is formed by a peripheral outlet edge 54, which forms the downstream end of the outlet part.

The frustoconical constriction 48 and the frusto-conical extension 50 are surrounded by a funnel-like component 56, so that an annular gap air chamber 58 is formed between the funnel-like component 56 and an outer wall of the outlet part. This annular gap air chamber 58 is supplied by means of a plurality of inlet bores 60 from the annular chamber 42 with compressed gas. One in the presentation of the Fig. 2 The lower end of the funnel-shaped component 56 is formed by an annular gap wall edge 62, which runs around the outlet opening 52. Between the annular gap wall edge 62 and the outlet edge 54, an annular gap 64 surrounding the outlet opening 52 is formed, which thus annularly surrounds the outlet opening 52.

Through this annular gap 64, in the representation of the Fig. 2a shown enlarged again, compressed gas exits at high speed. In this way, a liquid film 66, which forms on an inner wall of the conical enlargement 50, is drawn out at the exit opening 52 of this divergent nozzle exit part into a very thin liquid lamella 68, which disintegrates into small drops. Experimental investigations by the inventors have shown that in this way the maximum droplet size of the two-component atomizing nozzle 30 in relation to the nozzle according to the prior art Fig. 1 same energy consumption can be reduced to about one third. The annular gap air quantity is between 10% and 40% of the total atomizing air quantity.

As the representations of Fig. 2 and 2a can be seen, the annular gap outlet edge 62 protrudes slightly in the flow direction with respect to the outlet edge 54. Thus, by letting the outer annular gap nozzle protrude slightly beyond the nozzle mouth of the central nozzle, a further improvement of the atomization and protection of the sharp exit edge 54 is achieved. Advantageously, the annular gap outlet edge 62 protrudes beyond the outlet edge 54 by 5% to 20% of the diameter of the outlet opening 52.

Notwithstanding the embodiment of the atomizing nozzle 30, the annular gap air chamber 58 can be supplied with compressed gas from a separate line. For this purpose, for example, the holes 60 are closed and compressed gas is introduced from a separate line directly into the annular gap air chamber 58.

The sectional view of Fig. 3 shows another binary atomizing nozzle 70 according to a second preferred embodiment of the invention. The two-component atomizing nozzle 70, with the exception of an additional Schleierluftdüse 72 is equal to the Zweistoffzäubungsdüse 30 of Fig. 2 so that on an in depth explanation of the basic operation is omitted and the same components are provided with the same reference numerals.

The funnel-shaped component 56 is surrounded in the two-component atomizing nozzle 70 by a further component 74, which is constructed in principle tubular, forms a further lance tube and narrows in the direction of the outlet opening 52 to a funnel-like. In this way, a Schleierluftringspalt 76 is formed between the component 74 and the component 56. The Schleierluftspalt 76 ends approximately at the height of the outlet opening 52 and a lower, circumferential edge of the component 74 is disposed at the same height as the annular gap wall edge 62. A cross-sectional area of the Schleufluftspalts formed thereby is significantly larger than the annular gap 64, so that in the Schleierlufteinleitung Rückstromwirbel avoided can be. The nozzle nozzle or the outlet opening 52 annularly enclosing Schleierluftdüse 72 can be energetically charged with low pressure air, which is supplied according to an arrow 78.

The two-component atomizing nozzle 30 and the two-component atomizing nozzle 70 of the Fig. 2 or 3 can be arranged at the lower end of a so-called sputtering lance, which projects into a process space.

The presentation of the Fig. 4 shows a sectional sectional view of the two-component atomizing nozzle 30 of Fig. 2 , Through the various levels with compressed gas inlet openings 46a, 46b, 46c are placed sectional planes, which are designated I, II and III.

Because it is possible with the Zweistoffzerstäubungsdüse 30, 70 according to the invention with additional annular gap atomization, the liquid film 66, which exists in the divergent nozzle outlet part 50 on the inner wall to spray on the nozzle mouth to small drops, there are further interesting starting points for the nozzle design. In particular, it is permissible for the two-phase flow in the mixing chamber 40 and thus also in the outlet part 48, 50 of the nozzle 30, 70 impart a twist. As a result, a few more drops are thrown onto the inner wall of the outlet part. But this is not harmful because of the very efficient additional annular gap atomization. An advantage of the twisting is that a twisted flow in the mixing chamber 40 and in the outlet part 48, 50 sets rather centrally symmetrical. This can hardly be achieved with conventional two-fluid nozzles and has hitherto led to such nozzles being prone to "spitting", in that particularly large drops have been formed in regions at the nozzle mouth. So far, the centerlines of the Zuluftbohrungen 5 were the conventional nozzle according to Fig. 1 directed to the central longitudinal axis 24 of the two-fluid nozzle. One is inclined to assume that this would result in a centrically symmetrical flow configuration. This is not the case; Rather, even the smallest disturbances in the liquid or air supply to the mixing chamber suffice to allow the jet to escape laterally.

In contrast, according to the invention, the bores for forming the compressed gas inlet openings 46a, 46b, 46c are each aligned tangentially to a circle around the central longitudinal axis 36 of the nozzle. The thus twisted beam is centered thereby in the mixing chamber 40 and in the convergent outlet part and in the divergent outlet part of the nozzle 30, 70 automatically.

The tangential orientation of the compressed gas inlet openings 46a is based on the sectional view of Fig. 5 to recognize more precisely. Overall, four holes in the plane I are uniformly spaced from each other in the circumferential direction, which form a flow connection of the annular chamber 42 in the mixing chamber 40. All of these bores are arranged tangentially to an imaginary circle 80 about the central longitudinal axis 36 of the nozzle. As a result, in the plane I forms a twist, which by means of a circular arrow in the counterclockwise direction in the representation of Fig. 5 is indicated.

The presentation of the Fig. 6 shows the arrangement of four holes to form the Druckgaseinlassöffnungen 46 b in the plane II. The Druckgaseinlaßöffnungen 46 b are also arranged tangentially to a circle about the central longitudinal axis 36 of the nozzle, but such that in the plane II, a flow about the central longitudinal axis 36 in the clockwise direction results.

The pressurized gas inlet ports 46c in the plane III are as Fig. 7 can be seen, again arranged equal to the compressed gas inlet openings 46a in the plane I, so that in the plane III again a flow around the central longitudinal axis 36 results in the counterclockwise direction.

According to the invention, it is therefore intended to impose counter-rotating swirl directions in the different planes I, II, III of the supply air bores. Thus, the first inlet air bore plane I counted from the liquid inlet is left-handed, the second bore plane II is right-handed, and the third bore plane is again left-handed. Due to the opposite directions of twist in the different planes I, II, III, strongly pronounced shear layers are produced in the mixing chamber 40, which contribute to the formation of particularly fine drops.

Furthermore, the two-component atomizing nozzles 30, 70 can be optimized in that the massive liquid jet entering the mixing chamber is split even before the interaction with the atomizing air. This can be done in a different, conventional manner, for example by providing impact plates, swirl inserts and the like.

bibliography

1

Wurz, DE Flow behavior of thin water films under the effect of a co-current air flow of moderate to high subsonic velocities; Effects of the Film on the Airflow Proceedings of the Third International Conference on Rain Erosion and Associated Phenomena, England, Elvetham Hall, Vol. 2, pp. 727-750, 11-13 August (1970) Published by AA Fyall and RB King , Royal Aircraft Establishment, Engl and

2

Wurz, DE Experimental investigation of the flow behavior of thin water films and their reaction to a rectified air flow of moderate to high subsonic velocity Dissertation, Karlsruhe (1971 )

3

Wurz, DE Flow behavior of thin water films under the effect of a co-current air flow of moderate supersonic velocities Proceedings of the Fourth International Conference on Rain Erosion and Associated Phenomena, Germany, Meersburg, Vol. 1, pp. 295-318, 08-10 May (1974) Edited by AA Fyall and RB King, Royal Aircraft Establishment, Engl and

4

Wurz, DE Experimental investigation into the flow of thin water films; Effect on a co-current air flow of moderate to high supersonic velocities. Pressure distribution at the surface of a rigid wavy reference structure. XII Biennial Fluid Dynamics Symposium "Advanced Problems and Methods in Fluid Dynamics", Bialowieza, Poland, 1975 Archives of Mechanics, 28, 5-6, pp. 969-987, Warsaw (1976 )

5

Wurz, DE Liquid Film Flow Under the Effect of a Supersonic Air Flow Habilitationsschrift, Karlsruhe (1977 )

6

Wurz, DE Subsonic and supersonic gas liquid film flow paper no. 78-1130, AIAA-11-th Fluid and Plasma Dynamics Conference, Seattle, Washington (USA), 10-12 July (1978 )

7

Reske, R., DE Root Droplet impingement on walls and wavy water films Colloquium EUROMECH 162; Stability and Evaporation of Thin Liquid Films in Two-Phase Flow; Palace of Jablonna, Poland, 20-23 Sept. (1982 )

8th

Sill, KH, DE Wurz Colloquium EUROMECH 162; Stability and Evaporation of Thin Liquid Films in Two-Phase Flow; Palace of Jablonna, Poland, 20-23 Sept. (1982 )

9

Wurz, DE The subsonic-supersonic controversy of the shear-driven liquid film flow Colloquium EUROMECH 162; Stability and Evaporation of Thin Liquid Films in Two-Phase Flow; Palace of Jablonna, Poland, 20-23 Sept. (1982 )

Claims (15)

1. Two-substance atomizing nozzle for spraying a liquid with the aid of a compressed gas, comprising a mixing chamber (40), a liquid inlet (38) opening out into the mixing chamber (40), a compressed gas inlet (46a, 46b, 46c) opening out into the mixing chamber (40) and an outlet opening (52) downstream of the mixing chamber (40), characterized in that the mixing chamber (40), the liquid inlet (38) and the compressed gas inlet (46a, 46b, 46c) are configured and arranged such that a liquid film is present on the wall of the nozzle mouth, wherein an annular gap (64) surrounding the outlet opening (52) is provided for discharging of compressed gas, wherein the outlet opening (52) is formed by means of a peripheral wall, the outermost end of which forms an outlet edge (54), wherein the annular gap (64) is arranged in the region of the outlet edge (54), and wherein the annular gap (64) and the outlet edge (54) are configured and arranged such that compressed gas is discharged at high speed from the annular gap (64) directly in the region of the outlet edge (54) and distends the liquid film on the outlet edge (54) to a very thin liquid lamella and then atomizes said lamella to fine droplets.
2. Two-substance atomizing nozzle according to Claim 1, characterized in that the annular gap (64) is formed between the outlet edge (54) and an outer annular gap wall.
3. Two-substance atomizing nozzle according to Claim 2, characterized in that an outer end of the annular gap wall is formed by an annular gap wall edge (62) and in that the annular gap wall edge (62) is arranged after the outlet edge (54), as seen in the outflow direction.
4. Two-substance atomizing nozzle according to Claim 3, characterized in that the annular gap wall edge (62) is arranged downstream of the outlet edge (54) by between 5 % and 20 % of the diameter of the outlet opening (52).
5. Two-substance atomizing nozzle according to at least one of the preceding claims, characterized in that control means and/or at least two compressed gas sources are provided, so that a pressure of the compressed gas supplied to the annular gap and a pressure of the compressed gas entering the mixing chamber through the compressed gas inlet can be set independently of each other.
6. Two-substance atomizing nozzle according to at least one of the preceding claims, characterized in that the mixing chamber (40) is surrounded at least in certain portions by an annular chamber (42) for supplying the compressed gas and in that a gap air chamber (58) arranged upstream of the annular gap (64) is connected in terms of flow to the annular chamber (42).
7. Two-substance atomizing nozzle according to at least one of the preceding claims, characterized in that a veil-of-air nozzle (72) which surrounds the outlet opening (52) and the annular gap (64) at least in certain portions is provided.
8. Two-substance atomizing nozzle according to Claim 7, characterized in that the veil-of-air nozzle (72) has a veil-of-air annular gap which surrounds the outlet opening (52) and the annular gap (64) and the outlet area of which is larger than an outlet area of the annular gap.
9. Two-substance atomizing nozzle according to Claim 7 or 8, characterized in that control means and/or at least two compressed gas sources are provided, so that a pressure of the compressed gas supplied to the veil-of-air nozzle (72) is essentially lower than a pressure of the compressed gas supplied to the annular gap (64).
10. Two-substance atomizing nozzle according to at least one of the preceding claims, characterized in that means (46a, 46b, 46c) are provided to impart a swirl about a center longitudinal axis (36) of the nozzle (30; 70) to a mixture of compressed gas and liquid in the mixing chamber (40).
11. Two-substance atomizing nozzle according to Claim 10, characterized in that the compressed gas inlet (46a, 46b, 46c) has at least a first inlet bore, which opens into the mixing chamber (40) and is aligned tangentially in relation to a circle (80) around a center longitudinal axis (36) of the nozzle (30; 70), to produce a swirl in a first direction.
12. Two-substance atomizing nozzle according to Claim 11, characterized in that a number of first inlet bores, in particular four, are provided in a first plane (I) perpendicularly in relation to the center longitudinal axis (36) and spaced apart in the circumferential direction.
13. Two-substance atomizing nozzle according to Claim 11 or 12, characterized in that at least a second inlet bore, which is aligned tangentially in relation to a circle around the center longitudinal axis (36) of the nozzle (30; 70), is provided parallel to the center longitudinal axis (36) and at a distance from the first inlet bore, to produce a swirl in a second direction.
14. Two-substance atomizing nozzle according to Claim 13, characterized in that a number of second inlet bores, in particular four, are provided in a second plane (II) perpendicularly in relation to the center longitudinal axis (36) and spaced apart in the circumferential direction.
15. Two-substance atomizing nozzle according to at least one of Claims 11 to 14, characterized in that at least three planes (I, II, III) with inlet bores are provided, spaced apart and parallel to the center longitudinal axis, the inlet bores of successive planes (I, II, III) producing an oppositely directed swirl.

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