EP0892212B1 - Pressure spray nozzle - Google Patents

Description

Technical field

The invention relates to the field of combustion technology. It affects a pressure atomizing nozzle, comprising a nozzle body with a mixing chamber, which is connected to an outside space via a nozzle bore. The nozzle body has a first feed channel for a liquid to be atomized through which said liquid is under pressure and swirl-free Chamber can be fed. At least one opens into the chamber of the nozzle body another supply channel for part of the liquid to be atomized or for one second liquid to be atomized, through which said part of the liquid or the second liquid can be supplied under pressure and with swirl. The feed hole of the first feed channel lies with the Nozzle outlet bore on one axis. Such Nozzle is known for example from GB 2 001 262.

State of the art

Atomizer burners are known in which the oil which is burned mechanically finely distributed. It is divided into fine droplets of approx. 10 to 400 µm Disassembled diameter (oil mist), which is mixed with the combustion air in evaporate and burn the flame. In pressure atomizers (see Lueger Lexicon der Technik, Deutsche Verlags-Anstalt Stuttgart, 1965, volume 7, p.600) the oil is supplied to an atomizing nozzle under high pressure by an oil pump. The oil passes into an essentially tangential slot Swirl chamber and leaves the nozzle via a nozzle bore. This ensures that the oil particles have two motion components, one axial and one radial, preserved. The one emerging from the nozzle bore as a rotating hollow cylinder Oil film expands to a hollow cone due to centrifugal force Edges vibrate unstably and tear into small oil droplets. The atomized oil forms a cone with a more or less large opening angle.

1. Die Tröpfchengrösse muss gering sein, damit die Öltröpfchen vor der Verbrennung vollständig verdampfen können.

2. Der Öffnungswinkel (Ausbreitungswinkel) des Ölnebels soll insbesondere bei der Verbrennung unter erhöhtem Druck klein sein.

3. Die Tropfen müssen eine hohe Geschwindigkeit und einen hohen Impuls haben, um weit genug in den verdichteten Verbrennungsluftmassenstrom eindringen zu können, damit sich der Brennstoffdampf vollständig mit der Verbrennungsluft vor Erreichen der Flammenfront vormischen kann.

In the low-pollutant combustion of mineral fuels in modern burners, for example in premix burners of the double-cone type, which are described in their basic structure in EP 0 321 809 B1, special requirements are placed on the atomization of the liquid fuel. The main ones are:

1. The droplet size must be small so that the oil droplets can evaporate completely before combustion.

2. The opening angle (angle of spread) of the oil mist should be small, especially when burning under increased pressure.

3. The drops must have a high speed and a high momentum in order to be able to penetrate far enough into the compressed combustion air mass flow so that the fuel vapor can completely premix with the combustion air before reaching the flame front.

Swirl nozzles (pressure atomizers) and air-assisted atomizers of the known types with a pressure up to approx. 100 bar are hardly suitable because they do not allow small spreading angle, the atomization quality is restricted and the impulse of the drop spray is low.

With swirl-stabilized burners (e.g. double-cone type burners), where the flame stabilization is achieved with the help of a swirl flow Area between the swirl generator and the recirculation area, which through The swirl flow bursts open for mixing and evaporation of liquid fuel. To achieve good pre-evaporation should the fuel is atomized into the flow, which is what easiest to do with a pressure atomizing nozzle. Become the fine However, droplets exposed to a swirl flow field can cause one The droplets are thrown out due to the centrifugal forces (cyclone effect). Wetting the swirl generator or the mixing tube walls would have Consequence that the mixture deteriorates and that there is a risk of flashback along the walls and the appearance of deposits due to Fuel decomposition occurs.

As a result of this insufficient evaporation and premixing of the fuel is therefore an addition of water to lower the flame temperature locally and therefore NOx formation is necessary. Because the supplied water often too Flame zones are disturbing, which produce little NOx per se, but for flame stability are very important, instabilities often occur, such as flame pulsation and / or poor burnout, which leads to an increase in CO emissions.

An improvement is with the high pressure atomizing nozzle known from EP 0 496 016 B1 to reach. This consists of a nozzle body in which a turbulence chamber is formed which has at least one nozzle bore communicates with an outside space, and which have at least one Has feed channel for the liquid to be atomized under pressure. It is characterized in that the cross-sectional area of the turbulence chamber opening feed channel is larger by a factor of 2 to 10 than that Cross-sectional area of the nozzle bore. With this arrangement it is possible in the Turbulence chamber to generate a high level of turbulence that is on the way up does not subside as it exits the nozzle. The liquid jet is through the front the turbulence generated in the outside of the nozzle, ie after leaving the Nozzle bore decayed rapidly, with low spreading angles of 20 ° and less. The droplet size is also very small.

When operating gas turbine burners with liquid fuel, the aim is to if possible over the entire load range of the gas turbine (approx. 10% to 120% Mass flow based on nominal load conditions) a drop spray generate a stable, low-emission combustion throughout the area in a given air flow field.

The use of a high pressure atomizing nozzle described above for atomizing of liquid fuel in gas turbine burners leads to full load and overload (100-120%) as desired to a not too high pressure (100 bar) and a small droplet size, but undesirable due to the narrow spray angle Wall wetting and coking can be avoided.

At partial load, however, the fuel admission pressure drops due to the falling total fuel mass flow from. The energy required for atomization for Pressure atomizer is given via the fuel pressure, so that in this load range deteriorates the atomization quality and the penetration depth of the Fuel sprays in the air flow are lower due to the low fuel pressure becomes.

This disadvantage is with the two-stage pressure atomizer nozzle already mentioned eliminated according to DE 196 08 349.4. This becomes over during full and overload operation a swirl-free turbulence generator main stage and for partial and low-load operation additionally or operated alone via a pressure swirl stage. Has this solution but the disadvantage that due to the high turbulence in the jet of the main turbulence stage no very narrow spray angles (<15 °) are possible. For certain However, there are applications in which the burner air is strongly swirled very narrow fuel jet angles required to avoid wall application. In principle, jet nozzles, so-called plain jets, are suitable for this. This but produce atomization that is poorly suited to igniting the burner.

Presentation of the invention

The invention tries to avoid all of these disadvantages. You have the task based on a pressure atomizing nozzle of the above Kind of develop a simple Has construction and a precisely adapted to the respective operating conditions Spray angle or degree of atomization of the liquid to be atomized or liquids. Above all, extremely small spray angles should also be used can be realized, whereby the atomization is suppressed and it only goes there is a delayed dissolution of the liquid flow. In addition, a Methods for effective operation of this pressure atomizing nozzle are proposed become.

According to the invention, this is the case with a pressure atomizing nozzle, comprising a Nozzle body, in which a mixing chamber is formed, which has a Nozzle outlet bore communicates with an outside space and a first one Feed channel with a feed hole for a liquid to be atomized through which said liquid can be supplied without swirl and under pressure, wherein at least one additional supply channel for part of the to the chamber atomizing liquid or for a second liquid to be atomized, through which said part of the liquid or the second liquid under Pressure and swirl can be fed, the feed bore of the first feed channel lies on one axis with the nozzle outlet bore, thereby achieved that the outlet-side diameter of the nozzle outlet bore is at most so is as large as the diameter of the feed bore and the length of the nozzle outlet bore at least 2 to a maximum of 10 times the outlet side Diameter of the nozzle outlet bore.

The advantages of the invention include that it enables the possibility is given, the spray angle of the nozzle to an extremely small angle, i.e. up to a full jet without reducing disturbing turbulence. So that will the peculiarities of the swirl flow field of a swirl-stabilized burner Taken into account. On the other hand, the operation of a conventional one atomizing pressure atomizer nozzle can be maintained. Between these Extreme is a sliding control, the setting of all operating conditions, i.e. Spray angles and degrees of atomization possible. By observing the above The ratio of length to diameter of the nozzle outlet bore is achieved, that on the one hand the swirl from the swirl stage is not reduced too much and thus the atomization in the pressure atomizer operation is sufficient and on the other hand the divergence of the full beam is small enough that it does not become one unwanted ejection of drops can occur.

It is particularly expedient if the pressure atomizer nozzle has an outlet side Has diameter of the nozzle outlet bore, which is smaller than that Diameter of the feed hole, in particular it should be approximately 0.7 times the Diameter of the feed hole. This will make a bigger part of the total pressure drop across the outlet opening, resulting in a high Stability of the full jet leads.

Furthermore, an embodiment variant is advantageous in which the nozzle outlet bore is arranged in the cover of a first tube, in which a second tube smaller outer diameter is used, up to the said lid is sufficient, and at least one slot in the cover-side end of the second tube is provided, which is made tangential and forms a swirl channel and which is the annulus between the first and second tubes with the chamber connects from which the nozzle outlet bore leads into the outside space, the chamber being essentially through the lid, the inner walls of the second Pipe and a filler in the second pipe is limited, and the feed hole arranged in the filler on the same axis as the nozzle outlet bore is. This nozzle is characterized by a simple design.

Finally, a pressure atomizing nozzle according to the invention is advantageously used, whose nozzle outlet bore is constant over its entire length Has cross-sectional area. This is very easy to manufacture.

If, on the other hand, a two-stage pressure atomizing nozzle according to the invention is used, the nozzle outlet bore over their entire length in the direction of flow has a continuously decreasing cross-sectional area, so as a result of the converging Partly advantageous in the swirl stage, a uniform acceleration of the liquid to be atomized. The friction losses are less than in a variant in which a nozzle with a constant cross section of the Nozzle outlet bore is provided. With this geometry, when operating in the full jet stage suppresses atomization and there is a delay Dissolution of the liquid flow.

It is also advantageous if the pressure atomizing nozzle according to the invention has a Nozzle outlet bore, which has an inlet radius at its inlet end has at least as large as the radius of the mixing chamber. This prevents the flow from detaching at the inlet into the outlet bore and thereby loss of flow or at high speeds possible cavitation prevented.

Brief description of the drawing

In the drawing, three embodiments of the invention are shown.

Fig. 1

einen Teillängsschnitt einer erfindungsgemässen Druckzerstäuberdüse mit Vollstrahlstufe und Drallstufe in einer ersten Ausführungsvariante;

Fig. 2

einen Querschnitt der Druckzerstäuberdüse nach Fig. 1 im Bereich der Vollstrahlstufe entlang der Linie II-II;

Fig. 3

einen Querschnitt der Druckzerstäuberdüse nach Fig. 1 im Bereich der Drallstufe entlang der Linie III-III;

Fig. 4

einen Teillängsschnitt einer erfindungsgemässen Druckzerstäuberdüse mit Vollstrahlstufe und Drallstufe in einer zweiten Ausführungsvariante;

Fig. 5

einen Teillängsschnitt einer erfindungsgemässen Druckzerstäuberdüse mit Vollstrahlstufe und Drallstufe in einer dritten Ausführungsvariante.

Show it:

Fig. 1

a partial longitudinal section of a pressure atomizing nozzle according to the invention with full jet stage and swirl stage in a first embodiment;

Fig. 2

a cross section of the pressure atomizing nozzle of Figure 1 in the area of the full jet stage along the line II-II.

Fig. 3

a cross section of the pressure atomizing nozzle of Figure 1 in the region of the swirl stage along the line III-III.

Fig. 4

a partial longitudinal section of a pressure atomizing nozzle according to the invention with full jet stage and swirl stage in a second embodiment;

Fig. 5

a partial longitudinal section of a pressure atomizer nozzle according to the invention with full jet stage and swirl stage in a third embodiment.

Only the elements essential for understanding the invention are shown. Not shown, for example, regulating organs with which the size of the influenced by the individual stages of the nozzle flowing liquid flow can be. The direction of flow of the media is indicated by arrows.

Way of carrying out the invention

In the following, the invention will be described in terms of exemplary embodiments and FIG. 1 to 5 explained in more detail.

1 to 3 show a first embodiment of the invention, with Fig. 1 the Pressure atomizer nozzle in a partial longitudinal section and FIGS. 2 and 3 two Show cross sections in different planes.

The pressure atomizing nozzle comprises a nozzle body 30, consisting of a first tube 31, which is closed at its end seen in the direction of flow by a conical cover 32. In the middle of the cover 32 there is a nozzle bore 33, the longitudinal axis of which is designated 34. According to the invention, the length of the nozzle outlet bore is at least 2 to a maximum of 10 times the outlet-side diameter of the nozzle outlet bore. A second tube 35, which has a smaller outside diameter than the inside diameter of the first tube 31, is inserted into the tube 31 and extends as far as the cover 32 and rests thereon. The annular space 36 between the two tubes 31 and 35 serves to supply the or a part of the liquid 37 to be atomized. The end of the tube 35 resting on the cover 32 is provided with four tangentially arranged slots 38 which connect the annular space 36 to produce a chamber 39 which serves as a swirl chamber for the liquid 37 to be atomized flowing through the slots 38. The chamber 39 is delimited by the inner walls of the cover 32 and the second tube 35, and by a filler 40 which is inserted in the interior of the second tube 35 and fastened therein. This filler 40 is located at the same height as the upper edge of the slots 38, but it can also be spaced from the upper edge of the slots 38 in another embodiment variant, not shown. In the filler 40 there is a feed bore 41 for the liquid 37 to be atomized or for a second liquid to be atomized, which enable a swirl-free inflow of the liquid from the feed channel 42 into the chamber 39. The feed bore 41 lies on the same axis 34 with the nozzle outlet bore 33. In this first exemplary embodiment, the feed bore 41 has a constant diameter d _z over its entire length L. This diameter d _z is dimensioned somewhat larger than the diameter d _{a of} the nozzle outlet bore 33. The ratio of d _a to d _z should preferably be about 0.7. Then a good stability of the full jet is achieved when the nozzle is operated in the full jet stage, because a larger part of the total pressure drop occurs via the nozzle outlet bore. The ratio of length L to the outlet-side diameter d _{a of} the nozzle outlet bore 33 is also of particular importance for the function of the nozzle. According to the invention, it is in a range from 2 to 10. If the length-to-diameter ratio is too high, the twist becomes degraded too much from the swirl stage and the atomization in the pressure atomizer operation is insufficient. If the ratio of the length to the diameter of the nozzle outlet bore 33 is too small, on the other hand, the full jet has too great a divergence, which can lead to undesired discharge of drops.

The pressure atomizing nozzle according to the invention thus has two stages - one Full jet stage (see Fig. 2) and a pressure swirl stage (see Fig. 3), depending on the requirements can be operated either together or individually.

Deviating from the illustrated embodiment, the pressure atomizing nozzle also be provided with more or fewer slots 3 &. There is also one other distribution of the channels over the circumference possible. Instead of slots 38 Other swirl generators, for example blades, can also be arranged in the channel 36 be that ensure that the liquid to be atomized comes out of the channel 36 swirls into the chamber 39 enters.

Fig. 4 shows a partial longitudinal section of a second embodiment of an inventive two-stage pressure atomizer nozzle with full jet stage and swirl stage. The structure of the nozzle differs from the embodiment described above only in that the nozzle outlet bore 33 does not have a constant Has diameter, but that the diameter seen in the direction of flow over the entire length L of the nozzle outlet bore to the actual one Exit steadily decreases. This has compared to the first embodiment the additional advantages that a smooth acceleration of the liquid flow takes place in the nozzle that the friction losses in the swirl stage be reduced so that no turbulence occurs in the full jet stage or possibly existing ones are broken down and that the atomization of the liquid is suppressed becomes.

5 shows in a partial longitudinal section a third exemplary embodiment of a two-stage pressure atomizer nozzle according to the invention with a full jet stage and a swirl stage. The structure of the nozzle differs from the first exemplary embodiment described above only in that here too the nozzle outlet bore 33 does not have a constant diameter. In this third exemplary embodiment, the nozzle outlet bore has an inlet radius R _e which should be approximately as large as the radius R _{k of} the chamber 39. Here, too, there are fewer friction losses.

The nozzle according to the invention can, for example, be swirl-stabilized Gas turbine or boiler burners, e.g. a burner of the double cone type, installed and to the requirements of the respective burner flow field or Operating conditions of the gas turbine combustion chamber or the boiler adapted if necessary, also during operation. When igniting and in Partial load operation, for example, the nozzle is operated via the pressure swirl stage, by the liquid 37, in this case fuel, via the feed channel 36 and the swirl channel 38 (or via a swirl generator arranged in the channel 36) below high pressure and swirl enters the chamber 39 and through the nozzle outlet bore 33 is injected into the combustion chamber as a finely atomized drop. The rotating movement causes a hollow cone flow at the nozzle bore 33 generated. With increasing total fuel quantity and therefore with increasing The danger of dropping droplets is then on the full jet nozzle passed over by the fuel through the channel 42 and the supply bore 41, which lies on an axis with the nozzle outlet bore 33, is not swirled is introduced into the chamber 39, from where the fuel then the nozzle outlet bore 33 enters the combustion chamber as a full jet. The spray angle the full jet nozzle is extremely low, it is <5 °.

Both stages can be operated simultaneously, then takes place in the chamber 39 a mixture of the two fuel flows instead.

Depending on the operating conditions of the gas turbine, the nozzle can also be in only one Stage operated. As extremely small as possible at full load and overload Spray angle should be set, for example, only the full jet level used, and the fuel mass flow flowing through the swirl channels 38 is completely switched off It is also possible, depending on the load range different liquids, e.g. Water and oil, through channels 36, 38 and 42, 41 to feed the chamber 39 and atomize after their mixing.

LIST OF REFERENCE NUMBERS

30

nozzle body

31

first pipe

32

Cover of item 31

33

Nozzle outlet bore

34

Longitudinal axis of the nozzle

35

second pipe

36

Annulus between items 31 and 35

37

liquid to be atomized

37 '

second liquid to be atomized

38

tangential slit

39

swirl chamber

40

filling

41

feed bore

42

supply channel

L

Length of item 33

d _a

Diameter from item 33

d _z

Diameter from item 41

R _e

Inlet radius from item 33

R _k

Radius of pos. 39

Claims (10)

1. Pressure atomizer nozzle, comprising a nozzle body (30), in which a mixing chamber (39) is designed, the said mixing chamber being connected to an outside space via a nozzle outlet bore (33) and having a first feed duct (42) with a feed bore (41) for a liquid (37) to be atomized, through which feed bore the said liquid (37) can be supplied, free of swirling and under pressure, at least one further feed duct (36) for a portion of the liquid (37) to be atomized or for a second liquid (37') to be atomized opening into the chamber (39), through which feed duct the said portion of liquid (37) or the second liquid (37') can be fed under pressure, and with swirling, the feed bore (41) of the first feed duct (42) lying on one axis (34) with the nozzle outlet bore (33), characterized in that

   a) the outlet-side diameter (d_a) of the nozzle outlet bore (33) is at most as large as the diameter (d_z) of the feed bore (41), and

   b) the length (L) of the nozzle outlet bore (33) is at least twice to at most ten times the outlet-side diameter (d_a) of the nozzle outlet bore (33).
2. Pressure atomizer nozzle according to Claim 1, characterized in that the outlet-side diameter (d_a) of the nozzle outlet bore (33) is approximately 0.7 times the diameter (d_z) of the feed bore (41).
3. Pressure atomizer nozzle according to Claim 1 or 2, characterized in that the nozzle outlet bore (33) is arranged in the cover (32) of a first tube (31), in which is inserted a second tube (35) of smaller outside diameter, which reaches as far as the said cover (32), and in the cover-side end of the second tube (35) at least one slit (38) is provided, which is set tangentially and forms a swirl duct and which connects the annular space (36) between the first (31) and the second (35) tube to the chamber (39), from which the nozzle outlet bore (33) leads into the outside space, the chamber (39) being delimited essentially by the cover (32), the inner walls of the second tube (35) and a filling piece (40) in the second tube (35), and the feed bore (41) in the filling piece (40) being arranged on the same axis (34) as the nozzle outlet bore (33).
4. Pressure atomizer nozzle according to one of Claims 1 to 3, characterized in that the nozzle outlet bore (33) has a constant cross-sectional area over its entire length (L).
5. Pressure atomizer nozzle according to one of Claims 1 to 3, characterized in that the nozzle outlet bore (33) has, over its entire length (L), a cross-sectional area decreasing continuously in the direction of flow.
6. Pressure atomizer nozzle according to one of Claims 1 to 3, characterized in that the nozzle outlet bore (33) has, at its inflow-side end, an inflow radius (R_a) which is at least as large as the radius (R_k) of the chamber (39).
7. Method for operating a pressure atomizer nozzle according to one of Claims 1 to 6 in a swirl-stabilized burner, during ignition and in the part load mode the nozzle being operated via a pressure swirl stage, in that a portion of the liquid (37) to be atomized or a portion of the liquid (37') to be atomized is fed, swirled, via the feed duct (38) to the chamber (39), and a sharply swirled flow is generated there, which subsequently passes through the nozzle outlet bore (33) into the outside space, the proportion of liquid (37, 37'), fed via the swirl stage, being reduced with an increasing overall liquid mass flow, characterized in that, in the full load and overload mode, the nozzle is operated via a full jet stage, in that the liquid (37) is fed via the feed bore (41) to the chamber (39) and passes from there through the nozzle outlet bore (33) into the outside space as a full jet.
8. Method according to Claim 7, characterized in that a sliding changeover is made between the two stages.
9. Method according to Claim 7, characterized in that both stages are operated simultaneously and with a variable throughput.
10. Method according to Claim 7, characterized in that only one of the two stages is operated.

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