EP1016830B1 - Gas turbine combustor - Google Patents

Description

TECHNICAL AREA

The present invention relates to the field of gas turbines. It affects a combustion chamber for a gas turbine, in which combustion chamber with fuel mixed with an air stream entering the combustion chamber and then is burned, and the resulting combustion air flow downstream of the combustion chamber is fed to a turbine. Such an arrangement is over the document US-A-3,877,219 known.

STATE OF THE ART

Today, gas turbines are often designed in such a way that the one passed through them Air flow through two combustion chambers and, accordingly, twice over turbines is directed. The air drawn in is initially passed through a compressor group led, and then passed into a primary combustion chamber, where supplied Fuel-air mixture is ignited and burned. From the primary combustion chamber the hot combustion air flows over a first turbine and becomes downstream fed to the first turbine of a secondary combustion chamber, where fuel and if necessary additional air is added and the mixture ignites. Since the from the gases escaping from the first turbine are often very hot, i.e. above the auto-ignition temperature of the fuels can be in the secondary combustion chamber mostly do without active ignition. Downstream of the secondary combustion chamber there is then a second turbine, over which the hot combustion gases flow out of the secondary combustion chamber.

For reasons of space and for technical simplification, such gas turbines the individual components usually in series along a major axis of the Gas turbine arranged. Such a gas turbine group is from, for example EP 0 620 362 A1 known. The individual channels for the air flows and the combustion chambers are mostly all in the form of hollow cylinders, which reach around the axis of the gas turbine.

Secondary combustion chambers for such gas turbines are generally proportionate simply designed because they do not need burners, but the fuel after a suitable swirling of the hot ones emerging from the first turbine Air can simply be injected into the air flow via nozzles, and itself the mixture ignites itself after a characteristic time. A simple, the hollow-cylindrical secondary combustion chamber is, for example, out known from EP 0 669 500 A1.

As a result of because of the short auto-ignition times, especially of gaseous ones Fuels necessarily have high Mach numbers in secondary combustion chambers Frequently thermoacoustic oscillations of large amplitude occur in these on. There is also the problem of fast and effective mixing of air and fuel in the combustion chamber while avoiding Flow reflux. Usually, specific vortex-generating elements are used intended. Furthermore, especially in the more recent times, it must be mixed and the combustion management that the emission values remain within the legal limits.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide a combustion chamber for gas turbines, which disadvantages of the known solutions are avoided and in particular characterized by good and efficient mixing of fuel and supplied air.

The task is thereby in a combustion chamber of the type mentioned solved that the combustion chamber has an annular diffuser, in which the air flow enters that downstream of and in connection with the diffuser standing at least one substantially annular toroidal chamber arranged is that downstream of the annular toroidal chamber and over its circumference distributed mixing tubes branch, and that downstream of the mixing tubes an annular Combustion chamber is arranged, in which the mixing tubes open. The core the invention consists in the combination of diffuser, toroidal ring Chamber and mixing tubes have a premixing structure available too place in which air flowing through in an optimal manner, i.e. fast and can be mixed efficiently with fuel. Another advantage comes from that the proposed configuration is reduced to thermoacoustic Oscillations tend.

A first preferred embodiment of the combustion chamber according to the invention is characterized in that the combustion chamber as a secondary combustion chamber is designed, and that the gas turbine has a primary combustion chamber, a downstream the primary combustion chamber acting first turbine, a downstream of the first turbine acting secondary combustion chamber, and one downstream of the secondary combustion chamber has acting second turbine. The use of the combustion chamber as a secondary combustion chamber is advantageous, especially with such use at high Mach numbers short mixing times are required. Especially when the ignition, as described in a further embodiment, in the secondary combustion chamber is done by self-ignition, the quick and backflow-free mixing is in the proposed arrangement advantageous, and so it can controlled combustion in the area of the outlet of the mixing tubes in the combustion chamber or in Combustion chamber can be guaranteed.

Another preferred embodiment of the combustion chamber according to the invention is characterized in that the diffuser is designed such that the parallel air flow flowing to the gas turbine axis and entering the combustion chamber is initially deflected in a substantially radial direction, and that the Diffuser acts in a tangential manner on the toroidal chamber, so that the air flow entering the toroidal chamber curls up in the torus and swirls around the toroidal minor axis of the torus. Are now still preferred the mixing tubes on the one essentially opposite the diffuser Side attached in a manner essentially parallel to the axis of the gas turbine, In this way, two swirls of different screw rotation meet in front of the mixing tubes on top of each other, and then flow with mutual mixing and Annihilation of the vertebrae through the mixing tubes. This gives the possibility, as in another embodiment described in or in front of the area Mixing the opposite vortex means to provide with which fuel can be injected into the air flow. So the mixing process can be kept short and the ignition front can be set to the desired location.

Further preferred embodiments of the combustion chamber result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

einen axialen Längsschnitt durch einen Teil einer Gasturbine mit Sekundärbrennkammer;

Fig. 2

eine Teilansicht eines Schnittes entlang der Konusebene X-X aus Figur 1 in einer Ansicht von aussen nach innen; und

Fig. 3

die Wirbelzahl (swirl number) als Funktion des kleinen Torusradius (small radius of torus) in Metern.

The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawings. Show it

Fig. 1

an axial longitudinal section through part of a gas turbine with a secondary combustion chamber;

Fig. 2

a partial view of a section along the cone plane XX of Figure 1 in a view from the outside inwards; and

Fig. 3

the swirl number as a function of the small radius of torus in meters.

WAYS OF CARRYING OUT THE INVENTION

The proposed design of the combustion chamber is based, among other things, on the spectacular merging and mixing behavior of colliding, with opposing Rotating, rotating, subcritical vortices. This phenomenon occurred on Flow behavior in front of and in radial outlet pipes of steam turbines discovered. It is shown there that only when radial outlet pipes are attached the loss of free flow of the rotating air is possible, while losses occur due to swirling in simple openings. A detailed look at the behavior of the air flow before and in one Such a radial outlet tube shows that two in front of the tubes with opposite directions Rotating, rotating subcritical vortices collide, and the rotation of the two vertebrae within a distance of less than one Completely cancel each other out.

While normally in combustion chambers and especially in secondary combustion chambers according to the prior art vortex generating elements such as Swirl plates or fault air inlets must be provided to to ensure a quick and effective mixing of air and fuel, the mixing in the proposed combustion chamber is based on a structuring and guiding the flow channels, which a controlled vortex formation and inherent mixing of the air flowing therethrough.

The new concept is shown schematically in FIG. 1 using a secondary combustion chamber shown. Figure 1 shows a longitudinal section along the axis 21 of a gas turbine. The entire three-dimensional combustion chamber structure is essentially obtained by rotating the section about axis 21, i.e. it deals the channeling components with the exception of the mixing tubes 22 Axially symmetrical parts about the axis 21 of the gas turbine. The hot one from the first Combustion chamber, the primary combustion chamber, escaping airflow flows at the shown gas turbine first via a first turbine 11, which in one Bearing 31 is stored. There is a short one downstream of the first turbine 11 hollow cylindrical discharge line 12 through which the air flow from the first Turbine 10 flows parallel to the axis 21 of the gas turbine. The outflow pipe 12 is preferably just long enough that the axial hollow cylindrical Flow profile in the airflow 10 can recover. Downstream of the discharge line 12 is a diffuser 13 in which the air flow is controlled by the axial direction is deflected. The deflection occurs after in Figure 1 outside in an almost radial direction, but it is also conceivable in principle that Distraction inside. The curvature of the diffuser 13 can with the help of the inverse Euler equations can be optimized. It is essentially in the diffuser 13 therefore, the average flow velocity of the air flow approximately cut in half.

The diffuser 13 abuts a toroidal ring in a tangential manner downstream Chamber 14 to. The torus 14 is arranged perpendicular to the axis 21 of the generator, with a large torus radius 29 around axis 21, i.e. the major toric axis 27 and the axis 21 of the generator coincide. The circular line of the large torus radius 29 forms the annular torus minor axis 26, and the Torus outer wall 30 is formed by a small torus radius 28 around the ring Secondary torus axis 26 formed. As a result of the tangential inflow of the air flow the air flow becomes from the diffuser 13 into the toroidal chamber 14 deflected in a controlled manner around the annular torus minor axis 26 and curls up in the shape of a torus, like that from the first section the trajectory 15 of the vortex center can be seen in FIG. 1.

A plurality are located downstream of the toroidal annular chamber 14 of mixing tubes 22 which are perpendicular to the toroidal secondary axis 26 of branch off the chamber 14 and are distributed over the circumference of the chamber 14. Through these mixing tubes 22, the air flow rolled up in the torus 14 flows out of the annular toroidal chamber 14 from. The mixing tubes 22 are cylindrical or at least partially conical and preferably have a radius in the area of the small torus radius 28. Located downstream of the mixing tubes 22 the actual combustion chamber 18, which again essentially as a hollow cylinder is formed around the axis 21, and downstream of this combustion chamber 18 is a second turbine arranged.

Figure 2 shows part of a conical section through the chamber 14 and Mixing tubes 22 along the plane X-X in Figure 1 in view from the outside in. The behavior of the air flow in the chamber can be determined on the basis of this section 14 and the mixing tubes 22 illustrate. For simplicity's sake, consider that Air flow, which is tangent to the center between two mixing tubes 22 Diffuser 13 enters the chamber 14, this separates into two to the left and vertebrae 24 and 25 evading to the right, which are different Screw direction, 24 corresponds to a left-handed screw, 25 a clockwise. Each of the partial vertebrae 24 and 25 now "screws" in Direction of the nearest mixing tube 22 to flow out of the chamber 14 there to be able to. If the geometric dimensions are chosen correctly, finds flow reversal, if any, only in the upstream of the Mixing tubes 22 lie areas of the annular toroidal chamber 14. Immediately from the mixing tubes 22, two meet with different ones Vertebrae affecting each other in the direction of screw rotation. Once the two vortex centers entering the mixing tubes 22 stops any flow reversal and it jet-like vortex centers form. At a certain point in the area of At the entrance to the mixing tubes, the opposite vortices approach each other to the maximum it is precisely in this area that the violent process of unification of the two sets in Whirl in, whirling out completely. This complete Cancellation typically occurs within a distance of less than one Diameter of the mixing tubes 22, and it brings the complete mixing of the both air flows with it.

Especially in the area where the two vertebrae approach each other to a maximum, should advantageously Nozzles 32 are arranged with which liquid or gaseous Fuel can be injected. In this way, an optimal Mixing of fuel and air achieved under safe conditions. liquid Fuel can also be supplied through nozzles 20, which are located opposite the mixing tubes 22 Wall sides of the toroidal chamber 14 attached are injected into the air flow: Depending on the location of the injection, according to Auto-ignition characteristic of the injected fuel, according to the temperature of the Airflow and flow velocity are formed by auto-ignition of the mixture due to the high air temperature a flame front, which either at the area of the outlet of the mixing tubes 22 or behind it in the combustion chamber 18 can come to rest.

In order to be able to optimize the dimensioning of the individual components in a targeted manner, it is advantageous to compare the eddy number changes of the present concept with those of those types for which experimental data are available. The number of vertebrae relevant for the collision of subcritical vertebrae can be found as follows. Maintaining the volume flow requires that A I u I = A e u e . where A _I and A _{E are} the cross-sectional areas of the tangential entry of the diffuser 13 into the annular toroidal chamber 14 and the cross-sectional area 23 of the mixing tubes 22, and u _I and u _{E are} the corresponding flow velocities. With the help of the eccentricity radius ' r _{I of} the tangential input and the effective velocity component w _{E of} the vortex at the output, the condition for conservation of angular momentum can be expressed as follows: r I u I = A e π w e ,

Accordingly, the vortex number ξ of the colliding vertebrae can be expressed as ξ = w e u e = r I A e π A I , Size unit value mass flow kg / s 450.4 density kg / m ^∧ 3 3.81 Number of mixing tubes 12 exit speed m / s 140 Large radius of the torus m 1.4 Small radius of the torus m 00:15 Width of the entry slot m 00:12 volume flow m ^ 3 / s 118215 Diameter of the mixing tubes at the exit m 0.2993 Entire exit area m ^ 2 0.8444 Radius of the tangential input m 1.25 Total area of the entrance slot m ^ 2 0.9425 Flow velocity at the exit slot m / s 125.43 Area of the entrance slot per swirl arm, A _I m ^ 2 0.03927 Eccentricity radius , r _I m 00:09 Cross-sectional area of the vertebrae, A _E m ^ 2 0.07069 vertebrae 1:08

Table 1 gives the values for a secondary combustion chamber with 12 mixing tubes 22, each with an output radius of 300 mm. The large radius of the outputs of the mixing tubes 22, which are distributed circularly about the axis 21 via the chamber 14, is 1161 mm, which results in a circumferential spacing of the mixing tubes of slightly more than twice a mixing tube diameter. Size unit Value 1 Value 2 Large radius of the torus m 0.0675 0.0675 Small radius of the torus m 0.0275 0.0275 Width of the entry slot m 0.0085 0.0135 Radius of the tangential input m 0.04425 0.04675 Area of the entrance slot per swirl arm, A _I m ^ 2 0.01182 0.001983 Eccentricity radius , r _I m 0.02325 0.02075 Cross-sectional area of the vertebral arm, A _E m ^ 2 0.002376 0.002376 vertebrae 1.70 0.90

If you compare the value given in Table 1 for the vortex number of 1.08 with the experimental values given in Table 2 for steam turbine outputs, you can see that vortex numbers from 0.9 to 1.7 occur there. In the case of a "twin combustor" of the applicant, with an area of the entry slot per vertebral arm, A _I , of 0.010278m ² , an eccentricity radius , r _I , of 0.04375m and a cross-sectional area of the vertebral arm, A _E , of 0.047144m ² occurs a high vortex number of ξ = 1.64.

An optimal compromise between fast mixing and relatively unimportant Domains of flow reversal upstream of the vortex center the vertebra number ξ should be in the range of 1. Probably the best strategy this is the variation of the small torus radius 28 upstream of the mixing tubes 22, where you can start with a starting value of 150mm. Figure 3 shows the Swirl number as a function of the small torus radius' 28 (small radius of torus) in meters, whereby all other values are kept the same as in the table 1 given. You can see that the vortex number can be changed significantly by using the small torus radius 28 varies, experience has shown that optimally the small torus radius 28 does not deviate significantly from the typical mixing tube radius should.

LIST OF REFERENCE NUMBERS

10

Airflow from the first turbine

11

first turbine

12

Blow-out line of the first turbine

13

diffuser

14

toroidal chamber

15

Trajectory of the vertebral center

16

Wall of the mixing tube

17

Output of the mixing tube

18

combustion chamber

19

Exit from 18 to the second turbine

20

Liquid fuel injector

21

Axis of the gas turbine

22

mixing tube

23

Cross-sectional area of the mixing tube

24.25

counter-rotating partial flows of the air flow

26

Torusnebenachse

27

Torushauptachse

28

small torus radius

29

large torus radius

30

Torusaussenwand

31

Bearings of the first turbine

32

Injectors for fuel

33

Combustion air flow

Claims (12)

1. Combustion chamber (13, 14, 18, 22) for a gas turbine, in which combustion chamber (13, 14, 18, 22) fuel is mixed with an air flow (10) entering the combustion chamber (13, 14, 18, 22) and is subsequently burned, and the combustion-air flow (33) produced is fed to a turbine downstream of the combustion chamber (13, 14, 18, 22), characterized in that the combustion chamber (13, 14, 18, 22) has an annular diffuser (13), which the air flow (10) enters, in that at least one essentially annular toroidal chamber (14) is arranged downstream of the diffuser (13) and in such a way as to be connected to the latter, in that mixing tubes (22) branch off downstream of the annular toroidal chamber (14) and in such a way as to be distributed over the periphery of the latter, and in that an annular combustion space (18) into which the mixing tubes (22) open is arranged downstream of the mixing tubes (22).
2. Combustion chamber (13, 14, 18, 22) according to Claim 1, characterized in that the combustion chamber is designed as a secondary combustion chamber (13, 14, 18, 22), and in that the gas turbine has a primary combustion chamber, a first turbine (11) acting downstream of the primary combustion chamber, a secondary combustion chamber (13, 14, 18, 22) acting downstream of the first turbine (11), and a second turbine acting downstream of the secondary combustion chamber (13, 14, 18, 22).
3. Combustion chamber (13, 14, 18, 22) according to Claim 2, characterized in that the annular toroidal chamber (14) has an annular torus minor axis (26) which runs with a large radius (29) of torus about a torus major axis (27), and in which annular toroidal chamber (14) a torus outer wall (30) with a small radius (28) of torus is formed about the torus minor axis (26), and in that the torus major axis (27) is oriented essentially parallel to the axis (21) of the gas turbine.
4. Combustion chamber (13, 14, 18, 22) according to Claim 3, characterized in that the mixing tubes (22) are designed to be essentially conical or cylindrical, and in that the axes of the mixing tubes (22) are arranged outside the plane of the annular toroidal chamber (14) and essentially perpendicularly to the annular torus minor axis (26).
5. Combustion chamber (13, 14, 18, 22) according to Claim 3, characterized in that the radius of the mixing tubes (22) is formed in the region of the small radius (28) of torus or is preferably formed to be the same as the small radius (28) of torus.
6. Combustion chamber (13, 14, 18, 22) according to either of Claims 4 or 5, characterized in that the primary combustion chamber is an annular combustion chamber, in that an outflow line (12) designed as a hollow cylinder is arranged between the first turbine (11) and the diffuser (13), and in that the axis of the outflow line (12) runs parallel to the axis (21) of the gas turbine.
7. Combustion chamber (13, 14, 18, 22) according to Claim 6, characterized in that the annular diffuser (13) is designed in such a way that the air flow (10) flowing through the outflow line (12) parallel to the axis (21) of the gas turbine is deflected by the diffuser (13), and in that in particular this deflection is preferably effected in a direction running essentially radially to the axis (21) of the gas turbine.
8. Combustion chamber (13, 14, 18, 22) according to either of Claims 6 or 7, characterized in that the diffuser (13) acts tangentially on the annular toroidal chamber (14).
9. Combustion chamber (13, 14, 18, 22) according to Claim 8, characterized in that the diffuser (13) is designed in such a way that the air flow (10) is diverted by the diffuser (13) essentially radially outwards, and in that the diffuser (13) acts tangentially from inside on the annular toroidal chamber (14).
10. Combustion chamber (13, 14, 18, 22) according to either of Claims 8 or 9, characterized in that the mixing tubes (16) are arranged essentially opposite the inlet opening of the diffuser (13) into the annular toroidal chamber (14), and in that they are oriented essentially parallel to the axis (21) of the gas turbine.
11. Combustion chamber (13, 14, 18, 22) according to Claim 10, characterized in that means (20, 32) with which liquid fuel can be injected are arranged either on the rear side, remote from the mixing tubes (16), of the annular toroidal chamber (14) or in the central region of the mixing tubes (16) downstream of the annular toroidal chamber (14).
12. Combustion chamber (13, 14, 18, 22) according to either of Claims 10 or 11, characterized in that means (32) via which gaseous fuel can be injected are arranged in the central region of the mixing tubes (16) downstream of the annular toroidal chamber (14).

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