EP0794383B1 - Method of operating a pressurised atomising nozzle - Google Patents

Description

Technical field

The invention relates to the field of combustion technology. It affects on Method for operating a pressure atomizing nozzle in a Gas turbine combustion chamber according to the generic term of the Claim 1.

State of the art

Atomizer burners are known in which the for combustion oil is mechanically finely distributed. It will be fine Droplets of approx. 10 to 400 µm in diameter (oil mist) broken down, which are mixed with the combustion air in the Vaporize and burn the flame. In pressure atomizers (see Lueger - Lexicon of Technology, Deutsche Verlags-Anstalt Stuttgart, 1965, volume 7, p.600) is the oil under by an oil pump high pressure supplied to an atomizer nozzle. About essentially The oil gets into tangential slots a swirl chamber and leaves the nozzle through a nozzle bore. This ensures that the oil particles have two motion components, one axial and one radial. The emerging from the nozzle bore as a rotating hollow cylinder Oil film widens to a hollow cone due to the centrifugal force whose edges get into unstable vibrations and close tear small oil droplets. The atomized oil forms one Cone of 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, in particular 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 premix completely with the combustion air before reaching the flame front.

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

As a result of this insufficient evaporation and premixing of the Fuel is therefore an addition of water for local lowering the flame temperature and thus the formation of NOx. Since the water supplied often also flame zones disturbing, which generate little NOx per se, but for those Flame stability is very important, instabilities often occur, like flame pulsation and / or bad burnout, which leads to an increase in CO emissions.

An improvement is known from EP 0 496 016 B1 To reach high pressure atomizer nozzle. This consists of one Nozzle body, in which a turbulence chamber is formed, which has at least one nozzle bore with an outside space is connected, and which at least one feed channel for the liquid to be atomized under pressure having. It is characterized in that the cross-sectional area of the feed channel opening into the turbulence chamber is larger by a factor of 2 to 10 than the cross-sectional area the nozzle bore. This arrangement succeeds it to a high level of turbulence in the turbulence chamber generate that on the way to the exit from the nozzle not subsides. The liquid jet is through the front of the nozzle bore Turbulence generated in the outside space, i.e. after leaving the nozzle bore decayed rapidly, whereby there are low propagation angles of 20 ° and less. The droplet size is also very small.

When operating gas turbine burners with liquid fuel one strives, if possible, over the entire load range of the Gas turbine (approx. 10% to 120% fuel mass flow related on nominal load conditions) to generate a drop spray that entire pollutant-free and stable combustion in a given air flow field.

The use of a high pressure atomizer nozzle described above for atomizing liquid fuel in gas turbine burners performs at full load and overload (100-120%) as desired at a not too high pressure (100 bar) and a low one Droplet size, due to the narrow spray angle unwanted wall wetting and coking can be avoided.

At partial load, however, the fuel pre-pressure drops due to the falling total fuel mass flow. The atomizer required energy for pressure atomizers is over given the fuel admission pressure, so that in this load range the atomization quality deteriorates and the penetration depth of the fuel spray into the air flow through the low fuel pressure becomes lower.

From US 2,628,867 and DE 893 133 are fuel nozzles known with 2 pressure swirl stages, in which the second stage is only switched on at full load.

Presentation of the invention

The invention tries to avoid the disadvantages of the known prior art. It is based on the task of a method for operating a pressure atomizing nozzle with two To develop pressure swirl stages, with which a to the respective operating conditions angepasstet. Spray angle of the atomized Liquid is made possible. When using this pressure atomizing nozzle in a gas turbine burner is said to be even with small ones Fuel mass flows (approx. 25% based on nominal load conditions) a sufficiently large nozzle pressure is generated, while the nozzle with large fuel mass flows (approx. 100-120% based on nominal load conditions) not too high Nozzle form should need. With the drop spray created in this way should over the entire load range of the gas turbine a low-pollutant and stable combustion are made possible.

According to the invention, this is achieved in a method for operating a pressure atomizing nozzle in a gas turbine burner, wherein the pressure atomizing nozzle comprises a nozzle body in which one Swirl chamber is formed, which has a nozzle bore communicates with an outside space and at least a first feed channel for the liquid to be atomized through which said liquid is supplied with swirl under pressure will and in the chamber at least another feed channel for part of the atomized Liquid or for a second liquid to be atomized flows through which said part of the liquid, or the second liquid is supplied under pressure and with swirl by doing that the pressure atomizer nozzle at full and Overload operation of the gas turbine via a main pressure swirl stage with low Swirl is operated by the entire atomizer Liquid over the first The swirl chamber feed channel is swirled is generated, where there is a swirled flow which is then through the at least one nozzle bore got into the outside space and that the Pressure atomizer nozzle for partial and low-load operation of the gas turbine additionally over a further pressure swirl stage with a larger one Swirl is operated by part of the atomized Liquid or the second to be atomized Liquid via the at least one further feed channel more swirled fed to the chamber is generated and there a strong swirled flow which is then replaced by the at least a nozzle hole gets into the outside space, whereby the proportion of the supplied via the further swirl stage more twisted liquid with falling Total liquid mass flow is increased.

The advantages of the invention include that thereby an adjustment of the pot spray (atomization quality, drop size, spray angle) to the respective load conditions is made possible.

A smooth switchover between the two is advantageous Stages, and depending on the load conditions, the operation of the nozzle with only one of the two stages.

Finally, the nozzle and the method for operating the nozzle are advantageously used in a premix burner of the double-cone design or a four-slot burner used, with a part in the vicinity of the nozzle the combustion air (approx. 3 to 7%) in the jacket flow around the nozzle to be led. This makes local detachment and recirculation areas avoided. It prevents the recirculation zone is moved inside the burner.

Brief description of the drawing

In the drawing are several embodiments of the invention shown.

Fig. 1

einen Teillängsschnitt einer Druckzerstäuberdüse mit zwei Drallstufen;

Fig. 2

einen Querschnitt der Druckzerstäuberdüse nach Fig. 1 im Bereich der Drallhauptstufe entlang der Linie V-V;

Fig. 3

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

Fig. 4

eine schematische Darstellung des Flüssigkeitszufuhrsystems zur zweistufigen Druckzerstäuberdüse, wobei in beiden Stufen Öl zerstäubt wird;

Fig. 5

eine schematische Darstellung des Flüssigkeitszufuhrsystems zur zweistufigen Druckzerstäuberdüse, wobei in beiden Stufen jeweils unterschiedliche Flüssigkeiten(Öl, Wasser) zerstäubt werden;

Fig. 6

eine schematische Darstellung der Massenstromverteilung für eine Düse gemäss Fig. 1;

Fig. 7

einen Vormischbrenner der Doppelkegelbauart in perspektivischer Darstellung

Fig. 8

einen vereinfacht dargestellten Schnitt in der Ebene XIII-XIII gemäss Fig. 7;

Fig. 9

einen vereinfacht dargestellten Schnitt in der Ebene XIV-XIV gemäss Fig. 7;

Fig. 10

einen vereinfacht dargestellten Schnitt in der Ebene XV-XV gemäss Fig. 7;

Fig. 11

eine-schematische Ansicht eines Doppelkegelbrenners mit Mantelluftstromführung im Düsennahbereich;

Fig. 12

eine schematische Ansicht eines Vierschlitzbrenners mit Mantelluftstromführung im Düsennahbereich.

Show it:

Fig. 1

a partial longitudinal section of a pressure atomizing nozzle with two swirl stages;

Fig. 2

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

Fig. 3

a cross section of the pressure atomizing nozzle of Figure 1 in the area of the further swirl stage along the line VI-VI.

Fig. 4

a schematic representation of the liquid supply system to the two-stage pressure atomizing nozzle, with oil being atomized in both stages;

Fig. 5

a schematic representation of the liquid supply system for the two-stage pressure atomizing nozzle, different liquids (oil, water) being atomized in each of the two stages;

Fig. 6

a schematic representation of the mass flow distribution for a nozzle according to FIG. 1;

Fig. 7

a premix burner of the double cone type in perspective

Fig. 8

a simplified section in the plane XIII-XIII of FIG. 7;

Fig. 9

a simplified section in the plane XIV-XIV of FIG. 7;

Fig. 10

a simplified section in the plane XV-XV of FIG. 7;

Fig. 11

a schematic view of a double-cone burner with jacket air flow in the vicinity of the nozzle;

Fig. 12

is a schematic view of a four-slot burner with jacket air flow in the vicinity of the nozzle.

It is only essential for understanding the invention Elements shown. The same elements are in the different Figures with the same reference numerals. The Flow direction of the media is indicated by arrows.

Way of carrying out the invention

The invention is described below using several exemplary embodiments and Figures 1 to 12 explained in more detail.

1 to 3 show a first embodiment of the invention, 1 shows the pressure atomizing nozzle in a partial longitudinal section represents and FIGS. 2 and 3 two cross sections show in different levels.

The pressure atomizing nozzle comprises a nozzle body 30, consisting of from a first tube 31, which at its in the flow direction seen end closed by a conical cover 32 is. In the middle of the cover 32 is a nozzle bore 33 arranged, the longitudinal axis of which is designated 34. In the tube 31 is a second, a smaller outside diameter as the inside diameter of the first pipe 31 Tube 35 used, which extends up to the cover 32 and rests on it. The annular space 36 between the both tubes 31 and 35 are used to supply the or a part the liquid to be atomized 37 '. That on the lid 32 resting end of the tube 35 is made tangentially with four Slots 38 provided which connect the Create annular space 36 with a chamber 39, which as Swirl chamber for the inflowing through the slots 38 to atomizing liquid 37 'is used. Chamber 39 is confined through the inner walls of the lid 32 and the second Tube 35, and by a filler 40, which inside of the second tube 35 is inserted and fastened therein. This filler 40 is spaced from the top edge of the slots 38, but it can be in a different embodiment are also at the same level. In the filler 40 are four feed channels 41a for the liquid 37 to be atomized arranged.

Deviating from the illustrated embodiment, the Pressure atomizer nozzle also with more or fewer slots 38 or feed channels 41a. Another is the same Distribution of the channels over the circumference possible.

The feed channels 41a are in the filler 40 made tangential, see above that the liquid to be atomized 37 both through the channels 38 and also swirls into the chamber 39 via the channels 41a arrives. It is important that the liquid to be atomized 37 only a slight twist that leads to a narrow spray cone angle  leads, receives when it flows through the channels 41a has, while the swirl of the liquid 37 after flowing through the channels 38 is larger and thus a larger one Spray cone angle  can be reached. In the embodiment according to Fig. 1 is shown that the nozzle of two to be atomized Liquids 37 and 37 'is applied. Both Liquids 37, 37 'are the chamber 39 in this Case is a pure swirl chamber, swirl fed, where the liquid 37 is less swirled than the liquid 37 '. Due to the different twist, the spray cone angle  and thus the distribution of the liquid mass flow after the nozzle. Of course you can Issue of two liquids 37, 37 'also only one to be atomized Liquid 37 can be used for both twist stiffeners.

Fig. 4 shows a possible representation in a schematic representation Liquid supply system to the pressure atomizer nozzle. Over a Pump 42 becomes the liquid to be atomized, in this case liquid fuel (oil) 12, in a pressure vessel 43 pumped. A return valve 49 is used to set the pump admission pressure. Between the pump 42 and the pressure vessel 43 a shut-off valve 50 is arranged in the fuel line. Two lines 44, 45 extend from the pressure vessel 43, whereby the line 44 the annular space 36 (and thus the swirl atomizer stage) feeds and line 45 with the supply channels 41a (swirl atomizer stage) communicates. In lines 44 and 45, respectively a control valve 46 and 47 arranged which a regulation allow the amount of liquid supplied. Depending on requirements, one of the two valves can also be used 46, 47 must be completely closed, so that in this case only one of the two atomizing stages of the nozzle is in operation. Smooth switching is possible between the two stages. As indicated in Fig. 4, this fuel supply system should several burners, for example a gas turbine combustion chamber be supplied with fuel. The one shown Circuit has the advantage of regulating the two atomizer stages only the two valves 46, 47, i.e. just one Control valve per stage are necessary.

5 shows another embodiment variant analogous to FIG. 4. In this case, the pressure atomizing nozzle is fed with water 51 via a feed line 44 and with oil 12 via a feed line 45. A pump 42 is arranged in each of the lines 44 and 45 and a shut-off valve 50 is arranged downstream, with which the lines 44 and 45 can optionally be closed. The amount of the liquids 12, 51 to be atomized is regulated by means of the control valves 46, 47. If, as indicated in FIG. 5, several burners, for example a gas turbine combustion chamber, are supplied with liquid fuel 12 or water 51 via this liquid supply system, the nozzle can be operated at the start or at partial load by only atomizing oil 12 finely via the main swirl stage , The swirl stage can be designed for maximum pressure at maximum fuel mass flow m ˙ _Bs . At higher loads or full loads, water 51 is then supplied via line 44. Water 51 and oil 12 mix in chamber 39 and form an emulsion which is atomized when it emerges from the nozzle. This leads to a reduction in NOx emissions. Here, too, there is an advantage that only one control valve is required per atomizer stage, that only one oil line is required for gas turbine operation, and that the swirl stage can be designed for pure oil operation, since the supply of water 51 through line 44 increases the Total mass flow at the same pressure leads.

FIG. 6 shows the distribution of the fuel mass flow m in _BS as a function of the radius R of the spray in a pressure atomizing nozzle according to the embodiment variant shown in FIG. 1 at a certain distance from the nozzle. When operating the two swirl stages operating with different spray cone angles , the mass flow distribution between the two stages can be varied.

The pressure atomizing nozzle according to the invention can, for example installed in a gas turbine burner and operated as follows become:

If a pressure atomizing nozzle according to FIG. 1 is used, then with full and overload operation of the gas turbine, the entire Fuel to be atomized via at least one first feed channel 41a (four feed channels 41a according to FIG. 1) of the swirl chamber 39 fed with little twist, where there is a twisted Flow is generated, which then through the Nozzle bore 33 reaches the outside. Due to the low Twist, a narrow spray cone angle  is realized, which at high pressures for a fine atomization of the fuel leads. In the case of partial and low-load operation, an is also added Part of the fuel to be atomized over the minimum a further feed channel 38 (four feed channels according to FIG. 1) 38) is more swirled in the chamber 39. In the chamber 39 this creates a more swirled flow, which then through the nozzle bore 33 into the outside space arrives, the share of the over the swirl stage supplied more swirled fuel mass flow is increased with falling total fuel mass flow. The strong swirl leads to a larger one Spray cone angle , which in turn is the lower penetration depth of the fuel spray in the air flow is compensated. Due to the variable design of the spray cone angle  an optimal adaptation of the atomization of the fuel the respective operating conditions of the gas turbine take place. In contrast to the usual two-stage swirl nozzles the inventive design, both stages in a common Swirl chamber merged. It is also possible different liquids depending on the load range, e.g. oil 12 and water 51 to atomize in the two stages.

The pressure atomizing nozzle according to the invention can, for example in a premix burner of the double-cone type, the principal of which Structure is described in EP 0 321 809 B1 become.

Fig. 7 shows a perspective view of the double-cone burner with integrated premixing zone. The two partial cone bodies 1, 2 are with respect to their longitudinal symmetry axes 1b, 2b arranged radially offset from one another. This creates on both sides of the partial cone body 1, 2 in opposite Inflow arrangement each tangential air inlet slots 19, 20, through which the combustion air 15 in the Interior 14 of the burner, i.e. in that of the two partial cone bodies 1, 2 formed cone cavity flows. The partial cone bodies 1, 2 expand in a straight line in the direction of flow, i.e. they have a constant angle α with the burner axis 5 on. The two partial cone bodies 1, 2 each have one cylindrical initial part 1a, 2a, which is also offset run. In this cylindrical starting part 1a, 2a there is the pressure atomizing nozzle 3 according to the invention, which is roughly in the narrowest cross section of the conical interior 14 of the burner is arranged. Of course you can the burner also without a cylindrical initial part, i.e. pure be conical. The liquid fuel 12 is by means of atomized the nozzle 3 in the manner described above. Depending on the respective operating conditions there are different spray cone angles . The Fuel spray 4 is in the interior 14 of the burner from the through the air inlet slots 19, 20 tangentially into the Combustion air flow 15 flowing into the burner, the mixture is ignited only at the burner outlet, the flame passing through in the area of the burner mouth a backflow zone 6 is stabilized.

The two partial cone bodies 1, 2 have along the air inlet slots 19, 20 each have a fuel feed line 8, 9, which are provided on the long side with openings 17 through which another fuel 13 (gaseous or liquid) flow can. This fuel 13 is the tangential Air inlet slots 19, 20 in the interior of the burner flowing combustion air 15 admixed, which by the Arrows 16 is shown. A mixed operation of the burner Via the nozzle 3 and the fuel feeds 8, 9 is possible.

A front plate 10 with openings is arranged on the combustion chamber side 11, through which, if necessary, dilution air or cooling air are fed to the combustion chamber 22. It also ensures this air supply ensures that flame stabilization on Output of the burner takes place. There is a stable one Flame front 7 with a backflow zone 6.

8 to 10 the arrangement of baffles 21a, 21b. These can be around a pivot point, for example 23 can be opened or closed, so that the original gap size of the tangential air inlet slots 19, 20 is changed. Of course, the Burners can also be operated without these baffles 21a, 21b.

Since there is a risk with these burners that there is in the vicinity of the nozzle Form separation and recirculation areas This is prevented according to FIG. 11 by a channel around the nozzle 3 24 is arranged through which a jacket air flow 15a as Purge air flows. The jacket air flow 15a is about 3 to 7% of the combustion air flow 15.

Of course, with the method just described also a burner (see FIG. 12) can be operated, essentially consisting of a swirl generator 100 for a combustion air flow 15 and from means for injecting a fuel, a mixing section at the downstream of the swirl generator 100 220 is arranged and this within a first Section part 200 in the flow direction transition channels 201 for transferring one in the swirl generator 100 formed flow in the downstream of the transition channels 201 downstream flow cross section 18 of the mixing section 220, wherein the means for injecting the fuel is a pressure atomizing nozzle according to the invention, which according to one of the methods described above is operated. The Swirl generator 100 is preferably a conical structure, the tangential multiple (e.g. over four slots) from the tangential inflowing combustion air flow 15 is applied becomes. This combustion air flow 15 wraps around the fuel drop spray 4, previously by atomizing the liquid Fuel 12 in the two-stage pressure atomizer nozzle 3 was formed. The flow that is formed is based on a Transition geometry provided downstream of the swirl generator 100 (Transition channels 201) seamlessly into a transition piece 200 transferred, which is extended by a tube 18. Both Parts form the mixing section 220 to which the downstream side is located connects the actual combustion chamber, not shown here. The mixing section allows very good premixing of the fuel with the combustion air low-loss flow and prevented by a A maximum of axial speed on the axis a flashback the flame from the combustion chamber. Because the axial speed drops towards the wall, are in the wall of the tube 18th Bores 48 provided through which combustion air 15 flows in, which increases speed along the wall causes. Only after the mixing tube 220 does one form central backflow zone 6, which has the properties of a Has flame holder. It is also advantageous here if 3 up to 7% of the combustion air flow 15 as jacket air flow 15a around the pressure atomizer nozzle. In this way in turn become detachment and recirculation areas in the vicinity of the nozzle prevented.

LIST OF REFERENCE NUMBERS

1, 2

Partial conical bodies

1a, 2a

cylindrical initial part

1b, 2b

Central axis of the partial cone body

3

atomizer

4

Fuel droplet spray

5

Brenner

6

Backflow zone (vortex breakdown)

7

flame front

8, 9

fuel supply line

10

front panel

11

Openings in the front panel

12

liquid fuel

13

additional fuel (liquid or gaseous)

14

Interior of the burner

15

Combustion air flow

15a

Jacket air flow (part of item 15)

16

Injection fuel

17

openings

18

pipe

19, 20

tangential air inlet slot

21a, 21b

baffle

22

Combustion chamber downstream of the burner

23

pivot point

30

nozzle body

31

first tube

32

Cover of item 31

33

nozzle 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

Turbulence and / or swirl chamber

40

filling

41a

Feed channel (set tangentially)

42

pump

43

pressure vessel

44

management

45

management

46

Valve in pos. 44

47

Valve in pos. 45

48

Bores in pos. 18

49

Return valve

50

shut-off valve

51

water

100

swirl generator

200

Transition piece

201

Transition duct

220

mixing tube

α

Cone half angle



Spray cone angle

R

Radius of the spray

m ˙ _BS

Fuel mass flow

Claims (4)

1. Method for operating a pressure atomizer nozzle in a gas turbine burner comprising a nozzle body (30) in which there is formed a swirl chamber (39) which is connected via a nozzle bore (33) to an outer space and has at least one first feed channel (41a) for the liquid (37) to be atomized, through which said liquid (37) is fed in with a swirl under pressure, and at least one further feed channel (38) for part of the liquid (37) to be atomized or for a second liquid (37') to be atomized opens into the chamber (39) and through this feed channel the said part of the liquid (37) or the second liquid (37') is fed in under pressure and with a swirl, characterized in that, in full-load and overload operation of the gas turbine, the pressure atomizer nozzle is operated by way of a main pressure swirl stage with little swirl by feeding all the liquid (37) to be atomized to the swirl chamber (39) with a swirl via the first feed channel (41a), a swirling flow being produced there which then passes into the outer space through the nozzle bore or bores (33), and in that, in part-load and low-load operation of the gas turbine, the pressure atomizer nozzle is additionally operated by way of a further pressure swirl stage with a greater swirl by feeding part of the liquid (37) to be atomized or the second liquid (37') to be atomized to the chamber (39) with a greater swirl via the further feed channel or channels (38) and producing there a flow with a high degree of swirl which then passes into the outer space through the nozzle bore or bores (33), the proportion of the liquid (37, 37') with a greater swirl fed in by the further swirl stage being increased as the total mass flow of liquid falls.
2. Method according to Claim 1, characterized in that a smooth switchover is effected between the two stages.
3. Method according to Claim 1, characterized in that both stages are operated simultaneously and with a variable throughput.
4. Method according to Claim 1, characterized in that only one of the two stages is operated.

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