EP1141628B1 - Burner for heat generator - Google Patents

Abstract

The invention relates to a burner for operating a heat generator. Said burner consists essentially of a swirl generator (100) for a combustion air flow (115) and means for injecting at least one fuel into the combustion air flow (115). Downstream of the swirl generator (100) a mixing section (20) is positioned which in a first part, in the direction of flow, presents a number of channels which are embodied in a transition piece (200) and serve to transfer a flow produced in the swirl generator (100) into a mixing tube (20) positioned downstream of the transition piece (200). A combustion chamber (30) is situated downstream of the mixing tube (20). The swirl generator (100) is integrated into a self-contained inflow cross-section (10) which is subjected to the combustion air flow (115).

Description

Technical area

The present invention relates to a burner for operating a heat generator according to the preamble of the independent claim. Such a burner is from EP 0 797 051 A2.

State of the art

To achieve high efficiencies and high power densities, is for modern gas turbines used the principle of staged combustion. there is in a first high pressure combustor, preferably with premix burners (see EP-0 321 809 B1) equipped, produces a hot gas, which after a partial relaxation in a first high-pressure turbine in a second Brennkammer (reheat combustion chamber) flows, in which the partially relaxed Hot gas is reheated to the maximum turbine inlet temperature, with which such a gas turbine based on a sequential combustion. A such gas turbine is from US-5,454,220, US-5,577,378 and EP-0 620 362 A1 forth.

The so-called reheat combustion chamber has a configuration which in the publications EP-0 745 809 A1 and EP-0 835 996 A1 shown in more detail and is described.

a) Es wird ein erheblicher rückgekühlter Luftmassenstrom zur Kühlung der Mischstrecke und der Längswirbelerzeuger benötigt.

b) Die erzeugten Längswirbel können den Strömungsquerschnitt, insbesondere in den Ecken des Rechtecks, nicht vollständig erfassen.

c) Bei der Erzeugung der Längswirbel wird in den Ablösegebieten der Längswirbelerzeuger kinetische Energie in Turbulenz dissipiert und nur ein Teil der kinetischen Energie in die Längswirbelbewegung umgesetzt.

d) Nach der stufenförmigen Erweiterung in die Brennkammer legt die Strömung sich erst nach einer erheblichen Laufstrecke an die Brennkammerwand an, das heisst, es entstehen unerwünschte Totwasser- und Rückströmgebiete nach dem Stufensprung.

This combustion chamber is of annular design, and it has essentially a series of individual juxtaposed transitional channels which form the individual burners of this combustion chamber. These individual burners have a nearly rectangular cross-section, in which case the mixture of the fuel with the oxygen-containing partially expanded hot gas, hereinafter called combustion air, from the first turbine, via a plurality of longitudinal vortex generators, also called vortex generators happens, which are attached to the cooled walls of the mixing section and to be self-cooled. These longitudinal vortex generators (cf EP-0 745 809 A1) produce on their surface a flow separation and deflection, which finally leads to the formation of longitudinal vortices. The rectangular mixing channel is almost filled by several of these longitudinal vortices. It has been shown that such a configuration can lead to imperfections in very specific operating modes and operating parameters:

a) A considerable recooled air mass flow is needed to cool the mixing section and the longitudinal vortex generators.

b) The generated longitudinal vortices can not completely capture the flow cross-section, in particular in the corners of the rectangle.

c) In the generation of the longitudinal vortices kinetic energy is dissipated into turbulence in the separation areas of the longitudinal vortex generator and only a part of the kinetic energy is converted into the longitudinal vortex movement.

d) After the step-like expansion into the combustion chamber, the flow is only after a considerable distance to the combustion chamber wall, that is, there are undesirable Totwasser- and Rückströmgebiete after the increment.

Presentation of the invention

The invention aims to remedy this situation. The invention as claimed in claim 1 is characterized, is the object of a Premix burner of the type mentioned above listed above Fix imperfections.

The mixture of combustion air, i. the partially relaxed Hot gases and fuel, is accomplished in a round mixing section, which mixing section is filled by a single swirl flow. For swirl generation are in the still rectangular held inlet cross-section a conical consisting of several partial bodies swirl generator or swirl generator blades installed, which a twisting of the combustion air form. The formed by the swirler blades or between The individual sub-bodies of the swirl generator existing entry slots are preferably of constant slot width, but they can be along their barrel length have a variable slot width. Preferably, there are four inlet slots provided, but also versions with a different number of slots possible are. Such swirl generation largely corresponds to one those according to DE 44 35 266 A1. A difference to this swirl generation is that the inventive swirl generator in a first rectangular inflow channel is integrated, this over the run length of the swirl generator in a channel with approximately square or round Cross-section is transferred, with a clean flow to the swirler inlet slots is respected, this at best flow separation too avoid.

Integrated into the swirl generator is a fuel distribution system for gaseous and / or liquid fuels, the fuel distribution thereby along the Entry slots, as is apparent from the latter document, or through the trailing edges of the swirl blades or through axial injection the fuel from the blade surface out, here it primarily for the injection of a low or medium calorific fuel (LBTU, MBTU) goes. If necessary, the fuel from a cold Carrier air stream or inert gas stream are enveloped to prevent premature ignition to avoid fuel. Liquid fuels are beneficial at injected upstream of the swirl generator by a plurality of individual jets, where it has been shown that it is extremely advantageous if the Number of individual beams with the number of inlet slots in the swirl generator or the number of Dralierzeugerschaufeln matches.

On the axis of the swirl generator is a free flow channel, the Prevents a backflow zone on the axis in the mixing tube. The supply of liquid fuel must therefore preferably outside the axis done by the above-mentioned multiple nozzle system.

To the swirler blades against oxidation attacks due to the hot To protect entry temperatures, these can be made of either a ceramic one Material produced and / or provided with an internal air cooling become. The design and manufacture of the air-cooled swirl generator blades follows the rules known from the cooled turbine blades, the heat transfer rates are however due to the lower flow rates compared to runners or vanes in the turbine much lower.

After the swirl generator, the flow is in a cylindrical mixing tube guided. The transition from the swirl generator to the mixing tube is to be designed in such a way that that the flow cross-sectional area is almost constant and no separations occur. This can be done either by a specially shaped transition piece or by immersing the swirler blades in the cylindrical Channel happen. Another possibility is the swirler blades with a cutaway trailing edge in the axial direction too Mistake. The length of the mixing tube is chosen so that of the Fuel injection until the end of the mixing tube, the autoignition of the selected fuels is not exceeded. Depending on the size of the Burner and depending on the selected burner pressure loss, the Length of the mixing section between zero and two burner diameters vary.

In order to reignite the flame in the building up boundary layers of the Transition piece and the mixing tube to avoid, can be suitable Place Flammenrückzündsperrfilme be introduced.

At the downstream end of the mixing tube, a differently shaped Demolition edge can be attached, which is due to the Coanda effect a convexly curved end portion stabilizes the boundary layer and the entire Flow deflects outwards. This will on the one hand achieved that the Flow in the combustion chamber moves faster to the wall and faster is delayed, so that can set a turbulent flame front. On the other hand, the delay at the end of the mixing tube part of the recovered dynamic pressure in the sense of a diffuser effect.

The swirl intensity can be adjusted so much that downstream of the mixing section a Rückströmgebiet arises on the axis, preferably the swirl strength but be so great that the flow downstream of the mixing tube within a Mixing tube diameter on the axis only at speeds smaller the cross-sectional average combustion chamber velocity is delayed. The turbulent ones generated at this lossy delay Velocity fluctuations are used for flame stabilization.

The fuel supply to the swirl generator is done by one to the burner axis radially extending fuel and cooling air supply. The swirl generators can be attached to the fuel supply and with this radially from the gas turbine be removable without the housing must be lifted.

a) dass durch die Ausführung der Mischstrecke als zylindrisches Rohr die für den Flammenrückschlag empfindliche Oberfläche minimiert wird; dadurch wird die zur Rückschlagsperre und zur Kühlung der Wand benötigte Kühl- und Filmluft reduziert und somit der Gesamtprozess optimiert;

b) dass es durch die Ausführung der Mischstrecke als zylindrisches Rohr möglich ist, mit einem einzigen Längswirbel die gesamte Mischstrecke optimal auszufüllen;

c) dass die Eindüsung des Brennstoffes entlang der Eintrittsschlitze eine gute Feinverteilung ermöglicht, dadurch wird die erforderliche Mischstrecke nach dem Drallerzeuger minimiert;

d) dass die Drallerzeugung verlustarm erfolgt, das heisst, es werden bei einer erfindungsgemässen Auslegung keine Ablösegebiete und Totaldruckverlustzonen generiert. Dies hat zur Folge, dass der Druckverlustbeiwert des Brenners bezogen auf den effektiven Strömungsquerschnitt klein wird, und in der Mischstrecke nur wenig flammenstabilisierende Turbulenz vorhanden ist; damit wird ein Flammenrückschlag schon bei geringeren Strömungsgeschwindigkeiten vermieden,

e) dass durch die starke Strömungsverzögerung stromab des Mischrohres es möglich ist, das Öffnungsverhältnis, nämlich Mischrohrquerschnitt zu anteiligem Brennkammerquerschnitt, auf Werte > 4 bis mindestens 10 zu erhöhen. Dadurch lässt sich bei gleichbleibender Verweilzeit und damit weiterhin gutem Ausbrand eine wesentliche kürzere Brennkammer bauen,

f) dass der Drallerzeuger und die Brennstoffeindüsung konstruktiv so ausgestaltet werden können, dass sie ohne Abheben des Gehäuses der Gasturbine radial nach aussen ausgebaut werden können. Damit lassen sich auszutauschende Drallerzeuger leicht ersetzen und ein Wechsel auf andere Brennstoffe oder Brennstoffeindüsungssysteme leichter bewerkstelligen.

In the invention, further advantages can be achieved thereby,

a) that the execution of the mixing section as a cylindrical tube, the surface sensitive to the flashback is minimized; this reduces the cooling and film air required for the non-return valve and the cooling of the wall and thus optimizes the overall process;

b) that it is possible by the execution of the mixing section as a cylindrical tube to optimally fill the entire mixing section with a single longitudinal vortex;

c) that the injection of the fuel along the entry slots allows a good fine distribution, thereby minimizing the required mixing distance after the swirl generator;

d) that the swirl generation takes place with low loss, that is, in a design according to the invention, no detachment regions and total pressure loss zones are generated. This has the consequence that the pressure loss coefficient of the burner with respect to the effective flow cross-section is small, and in the mixing section little flame-stabilizing turbulence is present; thus a flashback is avoided even at lower flow rates,

e) that due to the strong flow delay downstream of the mixing tube, it is possible to increase the opening ratio, namely mixing tube cross section to proportionate combustion chamber cross section, to values> 4 to at least 10. As a result, it is possible to build a considerably shorter combustion chamber while retaining the residence time and thus ensuring good burnout,

f) that the swirl generator and the fuel injection can be structurally designed so that they can be removed without lifting the housing of the gas turbine radially outward. This makes it easy to replace exchanged swirl generators and make it easier to change to other fuels or fuel injection systems.

Advantageous and expedient developments of the invention are characterized in the further claims.

Brief description of the drawings

In the following, with reference to the drawings, embodiments of Invention explained in more detail. All for the immediate understanding of the invention insignificant features have been omitted. Same elements are in provide the different figures with the same reference numerals. The flow direction the media is indicated by arrows.

Fig. 1

einen schematischen Schnitt durch einen Brenner,

Fig. 2

eine Konfiguration des eingebauten Drallerzeugers in perspektivischer Sicht und

Fig. 3

eine weitere Ausführung eines Drallerzeugers.

Show it:

Fig. 1

a schematic section through a burner,

Fig. 2

a configuration of the built-in swirl generator in a perspective view and

Fig. 3

another embodiment of a swirl generator.

Ways to carry out the invention, industrial usability

Fig. 1 shows the overall structure of a burner system for operating a combustion chamber. The burner system basically consists of four operating stages, which each fulfill a certain function and among themselves in an interdependent Process flow. The first section consists of one hand an inflow passage 10 for a combustion air flow, in which inflow passage 10 a swirl generator 100 is arranged. The in this swirl generator 100 swirl flow formed is arranged on the basis of a downstream Transition geometry 200 transferred without separation into a mixing tube 20. A such transition geometry 200 is in the document DE 44 35 266 A1 under Fig. 6 is shown and described. Abströmungsseitig of the mixing tube 20 is located the actual combustion chamber 30, which here only by the flame tube is a picture-picture light. The mixing tube 20 satisfies the condition that downstream of Swirl generators 100 a defined mixing distance is provided, in which a perfect premix of fuels of various types is achieved. This mixing section, so the mixing tube 20, further allows a lossless flow guidance, so that also in operative connection with the Transition geometry 200 initially can not form a backflow zone, which along the length of the mixing tube 20 on the quality of mixing for all types of fuel Influence can be exercised. This mixing tube 20 has one more another characteristic being that in the mixing tube itself the axial velocity profile has a pronounced maximum on the axis, so that a flashback of the flame from the combustion chamber 30 is not possible. However, it is true that with such a configuration, this axial velocity falls off towards the wall. To re-ignite in this area too Stop, the mixing tube 20 in the flow and circumferential direction with a number of regularly or irregularly distributed holes 21 most different Cross sections and directions provided by which a Air quantity flows into the interior of the mixing tube 20, and along the wall in the Meaning of a filming an increase in prevailing speed induced. Another way to achieve the same effect is that the flow cross-section of the mixing tube 20 downstream the transition geometry 200 undergoes a constriction, whereby the entire speed level within the mixing tube 20 is raised becomes. In the figure, these holes 21 extend at an acute angle opposite the burner axis 60. Furthermore, the outlet corresponds to the Transition geometry the narrowest flow cross-section of the mixing tube 20th The said transition geometry 200 thus bridges the respective one Cross-sectional difference, without negatively affecting the flow formed influence. If the chosen precaution in guiding the pipe flow 40 along the mixing tube 20 an intolerable pressure drop can be remedied by this at the end of the Mixing tube 20 a in the figure not shown in detail diffuser is provided. At the end of the mixing tube 20 then closes the already mentioned Combustion chamber 30, wherein between the two flow cross-sections a Cross-section jump is present. Only here does a central backflow zone form 50, which has the characteristics of a bodiless flame holder having. Forms within this cross-sectional jump during the Operation a flowable edge zone, in which by the there prevailing negative pressure vortex shedding arise, this leads to a reinforced ring stabilization of the return flow zone 50. Front side, the Combustion chamber 30 a number of openings 31, through which an amount of air flows directly into the cross-sectional jump, and there lower lower contributes to that the ring stabilization of the Rückströmzone 50 is strengthened. Danebst may not to mention that the generation of a stable return flow 50 also requires a sufficiently high swirl number in a tube. Is one Initially undesirable, so can stable Rückström zones by the supply small strongly twisted air flows at the pipe end, for example by tangential openings are generated. It is assumed here that the amount of air required for this purpose in about 5-20% of the total to operate the Combustion chamber used amount of air is. What the nürere refinement the edge at the end of the mixing tube 20 to strengthen the Rück-strömzone 50th relates to the publications DE 195 47 913 A1, Fig. 7, and DE 196 39 301 A1, Fig. 8-11, referenced.

Fig. 2 shows the head stage of the burner. The quadrangular inflow channel 10 as well as the swirl generator 100 integrated therein are shown here. This inflow channel 10 forms an autonomous burner unit and in conjunction with a number of further juxtaposed inflow channels an annular Combustion chamber, preferably for the operation of gas turbines, in particular one Nachbrennkammer, as is apparent from EP 0 620 362 A1, Figure Pos. The inflow passage 10 is on the head side of rectangular shape, over the run length of the swirl generator 100 it goes over in a square cross-section.

The mode of operation of the swirl generator 100 shown here can be deduced from Description of the publications DE 44 35 266 A1, Fig. 2-5; DE 195 47 913 A1, Fig. 2-5; DE 196 39 301, Fig. 2-5, remove.

In short, here the swirl generator (100) consists of at least two hollow, conical, nested in the flow direction partial bodies 101, whose respective longitudinal axis of symmetry offset each other so run that the adjacent walls of the body part 101 in the Longitudinal tangential channels 102 for the inflow of combustion air 115 in an inner space 103 formed by the partial bodies 101 exhibit. With effect on this interior is at least one fuel nozzle intended.

Fig. 3 shows another embodiment of a swirl generator, which without can be further integrated into the inflow duct according to FIG. This Swirl generator 150 consists of a central body 151, which has a radial or quasi-radial conduit 152 for the supply of fuels 153, 154 having. On this central body 151 are individual swirl vanes 156 anchored, which extend in the axial direction. Covered in a jacket these swirl vanes are separated by a tube 155 which is open at each end, on the one hand on the head side for the inflow of the combustion air 115 (see FIG. and on the other drain side for the further flow of the twisted combustion air (see Fig. 1), whereby it is opposite to the swirl generator according to Fig. 2, which relates to the inflow of the combustion air, differs. Interdependent for the twisting of the combustion air 115 becomes fuel added, which here analogous to the swirl generator according to FIG. 2, also a first premix is formed; the final premix will then take place downstream, on the one hand along the transition geometry (see Fig. 1, item 200) and then inside the mixing tube (see Fig. 1, Pos. 20). liquid Fuels 154 are head side and central respectively. injected in a quasi-central way 154a; gaseous fuels 153, however, over a number of in the swirl vanes 156 integrated openings 153a. The number and degree of twist of the Swirl vanes 156 will vary depending on the particular requirements of the premix process.

In a decentralized fuel injection 154a of the liquid fuel 154 becomes the injection angle of the fuel jet associated with the fuel nozzle 154a relative to the axis, preferably approximately the angle of attack of Swirl vanes 156 equated. With this provision will be a perfect Premixing of the fuel used ensures, while maintaining a reliable and optimal flame positioning, i. an enrichment the central zone is thus sustainably prevented, and the fuel drops are stronger with increasing radius within the premix exposed to radial acceleration, such that they are in there Incoming combustion air can mix well.

In a multi-shell swirl generator of a burner, as for example from EP 0 321 809 B1 or from the swirl generators 1 (see the references cited therein), are suitable Good as injection position of the fuel, the trailing zones along the Lee side of the corresponding shell, or the guide vanes or the Swirl vanes of a suitably designed swirl generator. There it is Drop spray exposed to lower aerodynamic forces, and he will accordingly blended better radially into the combustion air.

The number of injection points is adapted to the burner design, wherein At least one injection per shell or blade is provided.

LIST OF REFERENCE NUMBERS

10

inflow passage

20

mixing tube

21

drilling

30

Combustion chamber, combustion chamber

31

openings

40

pipe flow

50

Backflow zone, backflow bubble

60

Brenner

100

swirl generator

101

partial body

102

Tangential channels

103

inner space

115

Combustion air, combustion air flow

150

swirl generator

151

Central body

152

fuel line

153

Fuel, gaseous fuel

153a

Fuel injection, fuel nozzle

154

Fuel, liquid fuel

154a

Fuel injection, fuel nozzle

155

pipe

156

swirl blade

200

Transition piece, transition channels, transition geometry

Claims (10)

1. Burner for operating a heat generator, the burner consisting essentially of a swirl generator (100, 150) for a combustion air flow (115) and of means for injecting at least one fuel into the combustion air flow (115), a mixing section being arranged downstream of the swirl generator (100, 150), which mixing section has, in a first section part in the flow direction, a number of ducts in a transition piece (200) for the transfer of a flow formed in the swirl generator (100, 150) into a mixing tube (20) connected downstream of this transition piece (200), a combustion space (30) formed by a cross-sectional expansion being arranged downstream of this mixing tube (20), characterized in that the swirl generator (100, 150) is integrated into an inlet flow duct (10) into which the combustion air flow (115) flows, the flow cross section of the inlet flow duct (10) merging from a rectangular cross-sectional shape at the head end into an approximately square or round cross-sectional shape over the length of the swirl generator (100, 150).
2. Burner according to Claim 1, characterized in that the swirl generator (100, 150) consists of at least two hollow, conical partial bodies (101), which are interlaced with one another in the flow direction, in that the respective longitudinal axes of symmetry of these partial bodies 101 extend offset to one another in such a way that the adjacent walls of the partial bodies (101) expose, in their longitudinal extent, tangential ducts (102) for the inlet flow of the combustion air flow (115) into an internal space (103) formed by the partial bodies (101).
3. Burner according to Claim 2, characterized in that at least one fuel nozzle is present which acts on the internal space (103).
4. Burner according to Claim 3, characterized in that the partial bodies (101) have a vane-shaped profile in cross section.
5. Burner according to Claim 1, characterized in that the swirl generator (100, 150) consists of a number of swirl vanes (156) which are integrated into a closed envelope.
6. Burner according to Claim 5, characterized in that the swirl generator (100, 150) has means for the injection (153a, 154a) of at least one fuel (153, 154).
7. Burner according to Claim 5 or 6, characterized in that the swirl generator (100, 150) has at least one head-side fuel nozzle (154a), and in that the fuel nozzle (154a) is directed relative to the burner axis (60) approximately in accordance with the setting angle of the swirl vanes (156).
8. Burner according to Claim 3 or 7, characterized in that the number of fuel nozzles (154a) at least corresponds to the number of the swirl-forming elements (101, 156) of the swirl generator (100, 150).
9. Burner according to Claim 2 or 5, characterized in that the number of ducts in the transition piece (200) corresponds to the number of the swirled partial flows formed by the swirl generator (100, 150).
10. Burner according to Claim 1, characterized in that the inlet flow duct (10) is a constituent part of an annular combustion chamber (30).

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