EP0638769B1 - Fuel injector for liquid and/or gaseous fuels and method for its operation - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of Combustion technology. It concerns a fuel lance for liquid and / or gaseous fuels for use in a Combustion chamber, as used for example in gas turbines finds.

STATE OF THE ART

For the injection of liquid and / or gaseous fuels into the combustion chamber of a premix burner Fuel lances used that protrude into the combustion chamber and the fuel or fuels in the combustion air flowing past bring in a suitable distribution.

• Die an der Brennstofflanze vorbeiströmende Verbrennungsluft hat eine Temperatur, die weitgehend unabhängig ist von der Strömung des Brennstoffes in der Lanze. Es kann notwendig sein, die Lanze selbst und auch die in ihr geführten Brennstoffe vor einer zu hohen Temperatur der Verbrennungsluft zu schützen.
• Wenn die Brennkammer mit einem hohen Verhältnis der Brennstoffmengen zwischen Vollast und Teillast betrieben werden soll, muss dafür Sorge getragen werden, dass in jedem Betriebszustand der Brennstoff in geeigneter Verteilung vorliegt und auf dieselbe Weise in den Strom der Verbrennungsluft eingebracht und gemischt werden kann. Da die Aerodynamik des Brenners praktisch unabhängig vom Brennstoff ist, muss zur Erzielung einer optimalen Verbrennung sowohl der gasförmige als auch der flüssige Brennstoff in gleicher Weise in den Strom der Verbrennungsluft injiziert werden können.
• Damit der Wirkungsgrad des Brenners möglicht gross wird, sollte so wenig wie möglich Träger- bzw. Hilfsluft in der Lanze verwendet werden.
• Weiterhin ist darauf zu achten, dass sich im Bereich der Brennstofflanze möglichst keine Rezirkulationszonen oder Nachläufe bilden, die mit brennstoffhaltigen Gas gefüllt sind und zu Flammenrückschlägen oder thermoakustischen Schwingungen führen können.
• Bei der Injektion von Flüssigbrennstoff, d.h. insbesondere Oel, muss vermieden werden, das die fein verteilte Oel-Luft-Mischung frühzeitig zündet.
• Für die flüssigen Brennstoffe muss auch vermieden werden, dass sich im Inneren der Lanze aufgrund erhöhter Temperaturen und Verdampfen des Brennstoffes störende Ablagerungen bilden, da dies den Betrieb der Lanze auf lange Sicht beeinträchtigen oder ganz unmöglich machen könnte.

When designing such fuel lances, various requirements must be met, some of which result from the ambient conditions and some from the requirements:

• The combustion air flowing past the fuel lance has a temperature that is largely independent of the flow of fuel in the lance. It may be necessary to protect the lance itself and the fuels it contains from excessive combustion air temperature.
• If the combustion chamber is to be operated with a high ratio of the fuel quantities between full load and partial load, care must be taken to ensure that the fuel is available in a suitable distribution in every operating state and can be introduced and mixed in the same way into the combustion air stream. Since the aerodynamics of the burner are practically independent of the fuel, it must be possible to inject both the gaseous and the liquid fuel into the stream of combustion air in the same way in order to achieve optimal combustion.
• So that the efficiency of the burner is as high as possible, as little carrier or auxiliary air as possible should be used in the lance.
• It is also important to ensure that, as far as possible, no recirculation zones or wake-ups form in the area of the fuel lance that are filled with fuel-containing gas and can lead to flashbacks or thermoacoustic vibrations.
• When injecting liquid fuel, in particular oil, it must be avoided that the finely divided oil-air mixture ignites early.
• For the liquid fuels, it must also be avoided that interfering deposits form inside the lance due to increased temperatures and evaporation of the fuel, since this could impair the operation of the lance in the long term or make it completely impossible.

A fuel lance of the type mentioned is known from GB-A-2021 254. There is liquid and / or gaseous fuel and air by one Set of concentrically arranged nozzles with an increasing diameter injected into the combustion chamber at an angle of 45 ° to the lance axis. The air jet surrounds the fuel jets. While the fuel is through If separate pipe systems are inserted into the lance from the outside, the air Removed combustion chamber. As a result, there is no possibility of the lance outside as well as to cool the internal fuel channels and those from the nozzles protect escaping fuel from early ignition.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a fuel lance and a method to indicate their operation, which the above. Meet requirements and be safe Injection of gaseous and / or liquid fuel at the same time high Ensure efficiency and low pollutant emissions.

The task is for a fuel lance for liquid and / or gaseous Fuels for use in the combustion chamber of a premix burner characterizing features of claim 1 solved.

The essence of the invention is that for cooling the lance and for distributing the fuel through the air duct air with a temperature up to several 100 ° C, but preferably less than 600 ° C, to the air / fuel nozzle led and there as a sheath flow surrounding the fuel flow in the Combustion chamber is blown. This also ensures safe cooling of the lance at higher temperatures of the combustion air flowing past the lance or combustion gases reached.

A first preferred embodiment of the invention Fuel lance is characterized in that the least an air / fuel nozzle and the at least one gas nozzle circular and one behind the other common nozzle axis are arranged, and the diameter the gas nozzle is smaller than the diameter of the Air / fuel nozzle. The gas flow emerging from the gas nozzle will pass through the Air / fuel nozzle surrounded by a jacket-shaped air flow. This ensures on the one hand that for the gaseous fuel gives practically the same injection route as for the liquid fuel. On the other hand supports the air flow largely independent of the amount of gas the gas injection, so that even with small gas flows the aerodynamic conditions in the combustion chamber hardly change.

Particularly simple and uniform flow conditions within the lance and at the nozzles result for the different fuels if preferred according to a second Embodiment of the invention also the liquid fuel nozzle along with the other two nozzles on the common Nozzle axis is arranged, and the diameter of the Liquid fuel nozzle is smaller than the diameter of the Gas nozzle, and if the liquid fuel pipe and the gas pipe firmly connected to the lance jacket in the area of the nozzles are. The fixed connection between the inner tubes and the lance jacket ensures that the nozzles are in their position to each other practical even with thermal expansions cannot move.

A further preferred embodiment of the invention is thereby characterized that the gas pipe and the liquid fuel pipe in the flow direction before the at least one Air / fuel nozzle ends that the gas nozzle and liquid fuel nozzle arranged at the end of each tube and are oriented parallel to the lance axis, and that for each Air / fuel nozzle and the other nozzles a scoop-shaped Baffle is provided, which from the other Gas or liquid flows emerging through nozzles by approximately 90 ° deflects and introduces into the respective air / fuel nozzle. This will help distribute and mix the liquid fuel an air powered atomizer realized in Anglo-Saxon literature as a "prefilming atomizer" is known (see also A. H. Lefebvre, Airblast Atomization, Prog.Energy Combust. Sci., Vol. 6, pp. 233-261 (1980)).

In a further preferred embodiment of the inventive Fuel lance is the air duct around the downstream led around the end of the fuel lance, and in this end at least one, largely parallel to the lance axis oriented auxiliary nozzle provided through which air can flow out of the air duct into the combustion chamber. By the auxiliary nozzle will fuel-free air in the room behind the The tip of the lance was injected to the critical point Formation of fuel-containing after-runs and / or recirculation zones to prevent.

Further embodiments of the fuel lance according to the invention as well as embodiments of the operating method according to the invention result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

in der Seitenansicht eine in einer Brennkammer angeordnete Brennstofflanze nach der Erfindung;

Fig. 2

im Längsschnitt die Spitze eines ersten bevorzugten Ausführungsbeispiels einer erfindungsgemässen Brennstofflanze mit den durch Pfeilen angedeuteten Gas- und Flüssigkeitsströmungen, wobei in der oberen Hälfte der Betrieb mit gasförmigem Brennstoff, und in der unteren Hälfte der Betrieb mit flüssigem Brennstoff dargestellt ist;

Fig. 3

im Längsschnitt (Fig. 3A) und teilweisen Querschnitt (Fig. 3B) ein zu Fig. 2 analoges zweites bevorzugtes Ausführungsbeispiel in den zwei Betriebsarten;

Fig. 4

im Längsschnitt (Fig. 4A) und mit separater Darstellung der Leitbleche (Fig. 4B) ein zu Fig. 2 analoges drittes bevorzugtes Ausführungsbeispiel in den zwei Betriebsarten; und

Fig. 5

ein mit Fig. 2 vergleichbares Ausführungsbeispiel, bei welchem die Gasdüsen in Strömungsrichtung vor den anderen Düsen angeordnet sind.

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the figures. Show it

Fig. 1

in the side view a fuel lance according to the invention arranged in a combustion chamber;

Fig. 2

in longitudinal section the tip of a first preferred embodiment of a fuel lance according to the invention with the gas and liquid flows indicated by arrows, the operation with gaseous fuel being shown in the upper half and the operation with liquid fuel being shown in the lower half;

Fig. 3

in longitudinal section (FIG. 3A) and partial cross section (FIG. 3B) a second preferred exemplary embodiment analogous to FIG. 2 in the two operating modes;

Fig. 4

in longitudinal section (FIG. 4A) and with a separate illustration of the guide plates (FIG. 4B), a third preferred exemplary embodiment analogous to FIG. 2 in the two operating modes; and

Fig. 5

an embodiment comparable to FIG. 2, in which the gas nozzles are arranged in the flow direction in front of the other nozzles.

WAYS OF CARRYING OUT THE INVENTION

In Fig. 1 is a possible arrangement of a side view exemplary fuel lance according to the invention in one by a housing 3 limited combustion chamber 2 of a gas turbine or the like. (Only a partial section is shown the chamber). The fuel lance 1 is in this Example with their lance axis 5 in the central axis of the Combustion chamber 2 is arranged and (as by the three long Arrows is indicated in Fig. 1) of hot combustion air flows around. The fuel lance 1 is therefore the aerodynamic Conditions in the combustion chamber 2 adapted and streamlined designed. It is of an elongated lance coat 11 surrounded and on a laterally outgoing arm 4 on Housing 3 attached. The support arm 4 is also streamlined designed and can in the cross section shown Have wing-like support arm profile 14.

Run through the support arm 4 and the fuel lance 1 itself - As broken up by the part shown in FIG Lance becomes clear - several pipes through which gaseous or liquid fuel and cooling or atomizing air led downstream lance tip and there in a in a manner to be described in more detail later on by appropriate Air / fuel nozzles 12 and an auxiliary nozzle 13 into the combustion chamber 2 is injected. The tubes include one in the axial direction internal liquid fuel pipe 7 and a the liquid fuel tube 7 concentrically in one Distance surrounding gas pipe 9. The gas pipe 9 is in turn surrounded at a distance by the lance jacket 11. Due to the concentric and spaced arrangement of pipes and jacket three channels are formed, the inner liquid fuel channel 6, the gas duct 8 and the air duct 10. Die Channels take over depending on the operating mode of the fuel lance 1 different functions, based on three preferred exemplary embodiments illustrated in FIGS. 2 to 4 are to be explained in more detail.

Fig. 2 shows for the first embodiment in longitudinal section the lance tip used to explain various Operating cases along the lance axis 5 in two separate Halves has been divided. The top half refers with the drawn currents (marked by arrows) to the operating case with exclusively gaseous fuel, the lower half to the operating case with exclusively liquid fuel. A corresponding two-part Representation is the same for the other reasons Figures 3 and 4 have been chosen.

Coming from the left, the inner liquid fuel tube ends in the tip of the lance 7, the gas pipe 9 and the lance jacket 11. The gas pipe 9 ends up in a hemispherical pipe head 17 above, which closes the pipe. The Liquid fuel pipe 7 is blunt on the inner surface of the Pipe head 17 welded (or soldered) and in this way completed at the end. The lance jacket 11 encloses the pipe head 17 at a distance in the form of a hemispherical shell, so that the formed between lance jacket 11 and gas pipe 9 Air duct 10 extends into the immediate tip of the lance and encloses the pipe head 17 on the outside. Between the pipe head 17 and the front hemisphere shell of the lance shell 11 are welded a plurality of connecting webs 16 or - soldered. In this way, the two tubes 7 and 9 and the lance jacket 11 in the area of the lance tip has a stable, firmly connected unit which is due to thermal expansion prevents displacement of the pipes among themselves.

There are several (preferably 4) sets in the area of the pipe ends provided by nozzles, each along a perpendicular (or at an angle) to the lance axis 5 standing nozzle axis 24 are. The nozzle sets are along the perimeter of the Fuel lance 1 distributed according to number and angular distance, that they have a given secondary combustion chamber flow pattern optimal mixing while avoiding Ensure wakes. Each nozzle set includes one in Liquid fuel pipe 7 embedded liquid fuel nozzle 18, a gas nozzle 15 embedded in the gas pipe and one in the lance jacket 11 recessed air / fuel nozzle 12. Each of the Nozzles 12, 15 and 18 are preferably circular. Your diameter are graduated with the inner liquid fuel nozzle 18 the smallest and the outer air / fuel nozzle largest diameter. Number and diameter of the Liquid fuel nozzles 18 are based on that in the normal case flow rate of the liquid fuel occurring. It is make sure that the nozzle diameter is not too large the nozzles become small when solid deposits are formed do not clog. Otherwise, the number of jets of fuel injected into the combustion chamber through the nozzles not be too big, so that the aerodynamics are not around the fuel lance 1 is disturbed so far that increasingly form fuel-containing wakes behind the lance.

In the operating case shown in the upper half of FIG. 2 with pure gas injection, the inner liquid fuel channel 6 not used at all. The flammable Gas flows through the gas channel 8 and the gas nozzle 15 and forms there a radially outward gas jet, the enters the combustion chamber 2 through the air / fuel nozzle 12. At the same time through the air duct 10 cooling air with a Temperature up to several 100 ° C, but preferably less than 600 ° C, which is also sent out of the air / fuel nozzle radially emerges into the combustion chamber and the gas jet initially surrounds it as a jacket-shaped stream. The cooling air has several functions: First, it cools the lance jacket 11 and forms a thermal protective jacket for the fuel channels further inside. Secondly, generated they on the air / fuel nozzle 12 a stable, constant Air jet, no matter how much gas through the lance is fed so that even at low Flow rates of gaseous fuel configuration the injection jets remain largely unchanged. Finally, the coat allows and supports relatively cool air is necessary for efficient combustion, sufficiently long mixing of the gaseous fuel with the combustion air in the combustion chamber 2 because one early ignition of the mixture safely avoided becomes.

In the operating case shown in Fig. 2 in the lower half with pure liquid fuel injection is through the inner liquid fuel channel 6 is a liquid fuel, usually an oil-water emulsion, to the liquid fuel nozzle 18 out and there radially as a liquid jet ejected outside. Through the gas channel 8 in this case Introduced air that exits through the gas nozzle 15 and in Interaction with that also through the gas nozzle 15 penetrating liquid jet a fine atomization of the Liquid fuel in small droplets ("plain-jet airblast atomization"). The atomizing jet is then at the air / fuel nozzle 12 in the same way as described above, surrounded by a cooling air jacket (the also contributes to atomization) and finally into the combustion chamber 2 injected. In addition to cooling through the air duct 10 flowing air is through the auxiliary air in the gas duct 8 provided a further thermal shielding stage. This allows the liquid fuel in the liquid fuel channel 6 be kept at temperatures at which solid deposits be safely avoided.

As can be seen from the above explanations, the cooling or Auxiliary air in the lance according to the invention several at the same time Functions: (i) It cools the lance and protects the inside Fuel channels from too high temperatures. (ii) It cools the fuel jets during injection and delays them thus heating them up, so that before self-ignition a there is sufficient mixing with the combustion air can. (iii) As auxiliary air, it drives the necessary Atomization of a liquid fuel. (iv) supports you when exiting through the air / fuel nozzles 12 as a jacket stream the mixing of the fuel jet in the combustion chamber. (v) It gets that even with low fuel flows jet system emerging from the nozzle sets upright.

In all of these processes, the special arrangement of the nozzles 12, 15 and 18 achieves that, regardless of whether gaseous or liquid fuel is used, always gives the same aerodynamic configuration, i.e. that Fuel jets are injected into the combustion chamber 2 in the same way become. Because of the stable connection of the pipes 7, 9 with each other and with the lance jacket 11, the uniaxial remains Arrangement of the nozzle sets and thus the aerodynamic Receive configuration even if by different Temperature distributions thermal tensions in the lance available.

The air from the air duct 10 can advantageously still perform another function: in the flow direction behind The tip of the lance can change for fluidic reasons basically form fuel-containing wakes that too Flashbacks or thermoacoustic vibrations (Pulsations). Such phenomena are intolerable, because they put a strain on the combustion chamber and, above all, too lead to increased pollutant emissions. For their prevention is preferably a centrally in the Lance axis 5 arranged auxiliary nozzle 13 through which a fuel-free air flow from the air duct 10 in the part of the combustion chamber located behind the tip becomes. At the same time, this measure also ensures that the fuel lance 1 cooled to the foremost tip becomes.

3 is another preferred embodiment reproduced for a fuel lance according to the invention. 3A corresponds in its form of representation to FIG. 2; Figure 3B is a partial cross section through the lance along line A-A of Fig. 3A, the area with the Liquid fuel nozzles 18 in FIG. 3A about the lance axis 5 is shown rotated. The embodiment shown gives way of the Fig. 2 especially with regard to the arrangement of the Liquid fuel nozzles 18 from: The nozzles 18 are not here longer with the other nozzles 12 and 15 together on a common one Nozzle axis 24 arranged, but from the lance tip moved backwards and at the same time around the Lance axis 5 rotated (Fig. 3B), so that one emerging from you No longer shine directly through the two other nozzles 15, 12 to the outside. Because a rigid position of the liquid fuel nozzles 18 to the other air / fuel nozzles 12, 15 is no longer necessary in this case, it can Liquid fuel pipe 7 ends before the pipe head 17 and does not need to be attached to the pipe head 17.

Another deviation in relation to the example from FIG. 2 results from the fact that in each of the gas nozzles 15 Guide tube 19 is fitted, which from the gas nozzle 15 through the air duct 10 into the associated Air / fuel nozzle 12 extends into it. This will already Favored sheath current formation described above, so that a gas stream flowing through the guide tube 19 at the outlet from the air / fuel nozzle 12 relatively protected in the combustion chamber 2 arrives.

In the upper part of FIG. 3A, as in FIG. 2, is the operating case represented with gaseous fuel in which the Liquid fuel pipe 7 is empty and is not used. The The injection jet is formed here completely analogously to Fig. 2. In the lower part of the picture is the operating case with liquid fuel reproduced: the liquid fuel occurs as Jet from the liquid fuel nozzle 18 is by in Gas channel 8 led auxiliary air on the inner wall of the gas pipe 9 entrained along to the gas nozzle 15 and together there blown off with the auxiliary air through the guide tube 19, wherein atomization takes place simultaneously ("air assist atomizer"). Additional ring plates 20 on both sides of the liquid fuel nozzles 18 improve the flow conditions.

Another preferred embodiment of a fuel lance according to the invention is shown in Fig. 4. Fig. 4A again corresponds to FIG. 2 or FIG. 3A, while in FIG. 4B the special shape of the used baffles and their interaction with the nozzles will be shown. 4 are the Air / fuel nozzles 12 arranged in the same place as in the exemplary embodiments from FIGS. 2 and 3. Clearly the arrangement of the other nozzles is different: The Gas pipe 9 and the liquid fuel pipe 7 end in the direction of flow even before the air / fuel nozzles 12. Everyone Air / fuel nozzle 12 associated gas nozzle 15 and liquid fuel nozzle 18 are at the end of each tube (9 and 7) and are oriented parallel to the lance axis 5. For each air / fuel nozzle 12 and the associated nozzles 15, 18, a blade-shaped guide plate 22 is provided, which the gas exiting from the associated nozzles 15, 18 or liquid flows deflected by about 90 ° and into the respective Air / fuel nozzle 12 initiates. As seen from Fig. 4B recognizes, the baffles 22 are cloverleaf around the lance axis 5 arranged around.

Each baffle 22 preferably runs in the area of Air / fuel nozzle 12 in a closed sheet metal ring 23 whose diameter is smaller than the diameter of the Air / fuel nozzle 12. The redirected streams from the assigned Nozzles 15, 18 are so when leaving the Air / fuel nozzle 12, in turn, in the form of a jacket from an air stream surround. In each of the gas nozzles 15 an additional Guide tube 19 can be fitted to a safe deflection of the To ensure gas flows through the baffles 22. The Baffles 22 are in the area of the nozzles (12, 15, 18) with the Lance jacket 11 firmly connected so that they are relative to Air / fuel nozzle 12 can not move. The connection takes place via a tubular head 21 in the form of a hemispherical shell, the position of the pipe head 17 from FIG. 2 or FIG. 3 occupies and by means of the connecting webs already mentioned 16 is anchored to the lance jacket 11.

In the upper part of FIG. 4 is again pure gas operation shown, in which the liquid fuel tube 7 is not is used. The gas flow exits the gas channel 8 here through the guide tube 19, is deflected by the guide plate 22, bundled by the sheet metal ring 23 and by the Air / fuel nozzle 12 coated with an air stream in the Combustion chamber ejected. When operating liquid fuel in In this case, gas duct 8 is not used in the lower drawing: The one emerging from the liquid fuel nozzle 18 The jet is used as a liquid film on the inner wall without auxiliary air of the baffle 22 passed to the air / fuel nozzle 12 and there by tearing off the finest droplets on the outer edge of the sheet metal ring atomized ("prefilmer atomizer").

Another preferred embodiment of a fuel lance according to the invention is shown in FIG. 5. In this example, only the liquid fuel nozzles 18 and the corresponding air / fuel nozzles 12 in a nozzle axis 24 arranged. The gas nozzles 15 are independently in Flow direction placed in front of the other nozzles 12, 18. in the Case of gas operation (upper half of the figure) mixes the gas in front of the air / fuel nozzle 12 in the air duct 10 intensive with the cooling air. The gas-air mixture occurs then through the air / fuel nozzle 12 into the combustion chamber out. A beginning in front of the gas nozzle 15 and at the gas nozzle passing air pipe 20 leads fuel-free Cooling air in the head area of the lance, where it is used to prevent of after-running through the auxiliary nozzle 13 into the combustion chamber is injected. In the case of liquid fuel operation (lower part of Fig. 5) the liquid fuel flows from the liquid fuel nozzle accommodated in the tube head 17 18 past the air tube 20 directly into the air / fuel nozzle 12, where it is in the manner already described with the cooling air cooperates from the air duct 10.

Overall, the invention results in a fuel lance, which in the same aerodynamic configuration are gaseous and can inject liquid fuels, even at high combustion gas temperatures works safely, optimal atomization of liquid fuels allowed and by an extended Mixing process enables very low pollutant emissions.

LIST OF DESIGNATIONS

1

Fuel lance

2nd

Combustion chamber

3rd

casing

4th

Beam

5

Lance axis

6

Liquid fuel channel

7

Liquid fuel pipe

8th

Gas channel

9

Gas pipe

10th

Air duct

11

Lance coat

12th

Air / fuel nozzle

13

Auxiliary nozzle

14

Support arm profile

15

Gas nozzle

16

Connecting bridge

17.21

Pipe head

18th

Liquid fuel nozzle

19th

Guide tube

20th

Air tube

22

Baffle

23

Sheet metal ring

24th

Nozzle axis

Claims (17)

1. Fuel lance for liquid and/or gaseous fuels for use in a combustion chamber (2), which fuel lance comprises

   (a) a liquid fuel pipe (7) extending along a lance center line (5) and surrounding a liquid fuel passage (6) for carrying a liquid fuel;

   (b) a gas pipe (9) surrounding the liquid fuel pipe (7) and forming a gas passage between itself and the liquid fuel pipe (7) for carrying a gaseous fuel;

   (c) a lance outer shell (11) surrounding the gas pipe (9) and forming an air passage (10) between itself and the gas pipe (9) for carrying cooling air and atomizer air;

   (d) at least one air/fuel nozzle (12) which is provided in the side of the lance outer shell (11) at the downstream end of the fuel lance (1) and through which air can flow out of the air passage (10) into the combustion chamber (2) surrounding the fuel lance (1); whereby

   (e) arranged in the gas pipe (9), there is at least one gas nozzle (15) through which gas can flow out of the gas passage (8) through the air passage (10) and, with the air, through the at least one air/fuel nozzle (12) into the combustion chamber (2); and whereby

   (f) arranged in the liquid fuel pipe (7), there is at least one liquid fuel nozzle (18) through which liquid fuel can flow out of the liquid fuel passage (6) through the air passage (10) and, with the air, through the at least one air/fuel nozzle (12) into the combustion chamber (2).

      characterized in that

   (g) air with a temperature of up to several hundred degrees centigrade, but preferably less than 600°C, is carried through the air passage (10) to the air/fuel nozzle (12) in order to cool the lance and distribute the fuel and is there blown into the combustion chamber (2) as a flow jacketing the fuel flow.
2. Fuel lance according to Claim 1, characterized in that the at least one air/fuel nozzle (12) and the at least one gas nozzle (15) are of circular configuration and are arranged one behind the other on a common nozzle center line (24), and the diameter of the gas nozzle (15) is smaller than the diameter of the air/fuel nozzle (12).
3. Fuel lance according to Claim 2, characterized in that, fitted into the gas nozzle (15), there is a guide pipe (19) which extends from the gas nozzle (15) through the air passage (10) into the air/fuel nozzle (12) in such a way that a flow of gas through the guide pipe (19) is jacketed by an airflow on emergence from the air/fuel nozzle (12).
4. Fuel lance according to either of Claims 2 and 3, characterized in that the liquid fuel nozzle (18), together with the two other nozzles (12, 15), is also arranged on the common nozzle center line (24), and the diameter of the liquid fuel nozzle (18) is smaller than the diameter of the gas nozzle (15).
5. Fuel lance according to Claim 4, characterized in that the liquid fuel pipe (7) and the gas pipe (9) are firmly connected to the lance outer shell (11) in the region of the nozzles (12,15,18).
6. Fuel lance according to either of Claims 2 and 3, characterized in that the liquid fuel nozzle (18) is displaced to the side relative to the gas nozzle (15) out of the nozzle center line (24), and the gas pipe (9) is firmly connected to the lance outer shell (11) in the region of the nozzles (12,15,18).
7. Fuel lance according to either of Claims 5 and 6, characterized in that, at the downstream end of the fuel lance (1), the gas pipe (9) merges into a rounded, closed pipe end (17) which is surrounded by the air passage (10) and the lance outer shell (11) and is fastened on the lance outer shell (11) by means of a plurality of connecting webs (16) which cross the air passage (10).
8. Fuel lance according to Claim 1, characterized in that the gas pipe (9) and the liquid fuel pipe (7) end, in the flow direction, before the at least one air/fuel nozzle (12), in that the gas nozzle (15) and the liquid fuel nozzle (18) are arranged at the end of the respective pipe (9 or 7) and are directed parallel to the lance center line (5) and in that a vane-shaped guide plate (22) is provided for each air/fuel nozzle (12) and the further nozzles (15,18), which guide plate deflects the gas and liquid flows emerging from the further nozzles (15,18) by approximately 90° and guides them into the respective air/fuel nozzle (12).
9. Fuel lance according to Claim 8, characterized in that, in the region of the air/fuel nozzle (12), the guide plate ends in a closed sheet-metal ring (23) whose diameter is smaller than the diameter of the air/fuel nozzle (12) in such a way that the deflected flows from the further nozzles (15,18) are jacketed by an airflow on emergence from the air/fuel nozzle (12).
10. Fuel lance according to either of Claims 8 and 9, characterized in that a guide pipe (19) is additionally fitted into the gas nozzle (15) and in that the guide plate (22) is firmly connected to the lance outer shell (11) in the region of the nozzles (12,15,18).
11. Fuel lance according to one of Claims 1 to 10, characterized in that a plurality of nozzles, preferably four, as determined by the flow surrounding the fuel lance (1), is distributed over the periphery of the fuel lance (1).
12. Fuel lance according to one of Claims 1 to 11, characterized in that the air passage (10) is led around the downstream end of the fuel lance (1), and at least one auxiliary nozzle (13) directed substantially parallel to the lance center line (5) is provided in this end, and air can flow out of the air passage (10) through this auxiliary nozzle (13) into the combustion chamber (2).
13. Fuel lance according to one of Claims 1 to 12, characterized in that the fuel lance (1) is fastened on a casing (3) surrounding the combustion chamber (2) by means of a side support arm (4) with a streamlined support arm profile (14) and in that the pipes (7,9) are led out of the combustion chamber (2) within the support arm (4).
14. Fuel lance according to Claim 1, characterized in that, in the flow direction, the at least one gas nozzle (15) is arranged before the other nozzles (12,18).
15. Fuel lance according to Claim 14, characterized in that at least one auxiliary nozzle (13) which is directed substantially parallel to the lance center line (5) is provided at the downstream end of the fuel lance (1) and air can flow out of the air passage (10) through this auxiliary nozzle (13) into the combustion chamber (2) and in that air pipes (20) are provided by means of which fuel-free cooling air can be guided past the gas nozzle (15) to the auxiliary nozzle (13).
16. Method of operating a fuel lance according to one of Claims 1 to 13, characterized in that the gas is carried through the gas passage (8) and the gas nozzle (15) to the air/fuel nozzle (12) and is there mixed with the airflow while the liquid fuel passage (6) remains unused.
17. Method of operating a fuel lance according to Claim 1, characterized in that liquid fuel in the form of an emulsion is carried through the liquid fuel passage (6) and the liquid fuel nozzle (18) to the air/fuel nozzle (12) and is there mixed with the airflow and in that air is additionally carried through the gas passage (8) to the air/fuel nozzle (12) in order to provide better distribution and additional cooling of the liquid fuel.

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