EP1121561A1

EP1121561A1 - Fuel injection system for the radial or slinger combustion chamber in a small gas turbine

Info

Publication number: EP1121561A1
Application number: EP99946177A
Authority: EP
Inventors: Alexander Böck
Original assignee: Rolls Royce Deutschland Ltd and Co KG
Current assignee: Rolls Royce Deutschland Ltd and Co KG
Priority date: 1998-10-12
Filing date: 1999-09-15
Publication date: 2001-08-08
Anticipated expiration: 2019-09-15
Also published as: DE59907475D1; EP1121561B1; DE19846976A1; WO2000022350A1

Abstract

The invention relates to a fuel injection system for a radial or slinger combustion chamber in a small gas turbine, comprising a radial or diagonal compressor that is mounted upstream from a radial combustion chamber and part of a turbine that is connected to the compressor by a rotor shaft that extends in an axial direction. Fuel is fed into an intersecting segment of said rotor shaft located in an area close to the compressor of the combustion chamber by means of a feed pipe that is arranged in a wheel of the radial compressor and enters the combustion chamber via feed holes that extend in a substantially radial direction. The intersecting segment consists of ventilation holes that are arranged in an offset position with respect to the feed holes. Said ventilation holes enable the leaking air from the combustion chamber that enters the rear chamber of the compressor to enter the inner chamber of the at least partially hollow rotor shaft, whereby said air can be released into the surrounding atmosphere via a central outlet in the turbine disc. Said system also consists of an injection ring that fully surrounds the rotor shaft in the region of the intersecting segment and is arranged at least a short distance away from the rotor shaft, at least in the orifice region of the feed holes, and rotates with said shaft about the center axis of the small gas turbine.

Description

Fuel injection system for a radial or Slinger combustion chamber of a small gas turbine

The invention relates to a fuel injection system for a radial or Slinger combustion chamber of a small gas turbine with a radial compressor or diagonal compressor upstream of the radial or Slinger combustion chamber and a turbine part connected to the latter via a rotor shaft running in the axial direction, the fuel being supplied by a in the impeller of the radial compressor / Diagonal compressor provided delivery pipe comes into a crossing part of the rotor shaft located in the area of the combustion chamber near the compressor and is supplied to the combustion chamber via supply bores running essentially in the radial direction. With regard to the technical environment, reference is made, for example, to US Pat. No. 5,526,640.

In the case of a radial combustion chamber with the features mentioned above, which is usually also referred to as a Slinger combustion chamber, the fuel is drilled through a bore that runs concentrically to the axis of rotation of the radial compressor (this term also includes the so-called diagonal compressors) or the rotor shaft in the compressor impeller or through a delivery pipe provided to the combustion chamber. It flows due to the rotary movement of the rotor shaft or the compressor impeller as a result of the centrifugal forces that arise as a result, the fuel as a thin film along the wall of the bore or the delivery pipe as far as directly below the primary zone of the combustion chamber. There, in the known state of the art, it is sprayed into the primary zone of the combustion chamber through a suitable tear-off edge or through individual radially arranged nozzles.

The problem with all radial or Slinger combustion chambers is that the combustion chamber is sealed as well as possible to the rear space behind the compressor impeller, i.e. to the so-called compressor back space, since the combustion chamber is open to the rotor shaft because of the fuel injection just described. Because the pressure in the combustion chamber is always higher than in the back of the compressor due to the effect of the compressor stator, a small part of the combustion chamber air always flows as so-called combustion chamber leakage air in a region between the rotating and the non-rotating elements provided seal in the compressor rear space.

Due to the inflow of combustion chamber leakage air throttled by the said seal into the compressor rear space, there is an excess of air which must flow away. This can be done via a gap between the compressor impeller and the compressor guide ring, whereby, however, recirculation can take place via the compressor guide ring and the combustion chamber. It is obvious that this has negative effects on the compressor efficiency and on its surge limit. As a remedial measure for this, the compressor back space can be vented, ie the so-called combustion chamber leakage air is then blown off into the surroundings, for example via additional pipelines, which, however, represents an effort which should be avoided. Therefore, said ventilation can also take place to the rear, as it were, through the rotor shaft, which is hollow at least in sections, for example through a central outlet opening in the turbine disk on its rear side and from there into the thrust nozzle of the small gas turbine. In this case, this combustion chamber leakage air can advantageously be used as cooling air for the rear of the turbine disk and also generates thrust by admixing it with the exhaust gas jet from the Kieingas turbine.

A disadvantage of this solution, however, is that the combustion chamber leakage air has a so-called crossing point with the fuel injection system, which is also provided in the rotor shaft and has already been briefly described above, which is why in the known prior art for this fuel injection system, only a plurality of individual nozzles opening in the combustion chamber in the radial direction are provided. However, these are unsuitable for the controllability of the fuel mass flow and for the atomization of the same at low speeds of the small gas turbine. At high speeds, the combustion chamber is sealed against the central fuel hole by the radial fuel column that forms, i.e. There would be no special sealing measures to be provided due to the fuel column, however, a windmilling start, which is often desired in small gas turbines, can then hardly be realized, since at low speeds the centrifugal force occurring is not sufficient to introduce the required amount of fuel into the combustion chamber against the pressure prevailing there promote.

The object of the present invention is to provide a remedial measure for the problems described. The features specified in the first claim contribute in their entirety to solving this problem, advantageous training and further developments form the content of the dependent claims. The invention is explained in more detail with reference to three preferred exemplary embodiments shown in the attached figures, it being possible for all the features described in more detail to be essential to the invention. It shows

1 shows a longitudinal section through a small gas turbine according to the invention, in which, in addition to the combustion chamber and the fuel injection system, the radial compressor and the turbine part are also shown, FIG. 2 shows the fuel injection system from FIG. 1 in an enlarged view, FIG. 3 shows a fuel injection system modified compared to FIG and FIG. 4 a modification of the fuel injection system shown in FIG. 3.

Reference number 1 denotes a Slinger combustion chamber of a small gas turbine, which - as shown in particular in FIG. 1 - has a radial compressor 2 upstream. The so-called turbine part 5 of the small gas turbine or more precisely the turbine disk 5a of the turbine part 5 is connected to the compressor impeller 2a of this radial compressor 2 via a rotor shaft 4 running in the axial direction 3. The compressor impeller 2a, the rotor shaft 4 and the turbine disk 5a rotate about the so-called central axis 19 of the small gas turbine.

The radial compressor 2 conveys an air flow to be supplied to the combustion chamber 1 in the direction of the arrow 6, which is required within the latter for the combustion of the fuel further supplied to the combustion chamber 1. Part of this air flow, also designated with reference number 6 for the sake of simplicity, does not, however, enter the combustion chamber 1 due to the different pressure conditions present in the different zones of the small gas turbine, but rather not on the combustion chamber 1 or on its side facing the radial compressor 2 in FIG. 1 specified (however in FIG. 2 with the reference number 25) end wall on the outside over a gap sealed by means of a seal 7 embodied here as a labyrinth seal (designated in FIG. 2 with the reference number 27) between rotating and non-rotating parts of the small gas turbine in the introduction to the description Defined so-called compressor back space 8. This part of the air flow 6 entering the compressor back space 8 is referred to as combustion chamber leakage air 6a.

The compressor rear space 8 located on the back of the compressor impeller 2a must therefore be ventilated, i.e. the combustion chamber leak air 6a must also be removed from the compressor rear space 8. This takes place via the rotor shaft 4, which is at least partially, but completely hollow, or more precisely via its interior 4a. As can be seen, the front end of the rotor shaft 4 facing the compressor impeller 2a is flange-like and represents a so-called crossing part 4b. Through this flange-like crossing part 4b, several (here preferably three evenly distributed over the circumference of the crossing part 4b) vent holes 9 through, which thus establish a connection between the rotor shaft interior 4a and ultimately the compressor rear space 8. Otherwise, the rotor shaft 4 is connected to the compressor impeller 2a in a rotationally fixed manner via this flange-like crossing part 4b.

After the combustion chamber leakage air 6a has now reached the interior 4a of the rotor shaft 4 from the compressor rear space 8 via the ventilation bores 9 in the intersection part 4b, it is discharged from the latter via an exhaust pipe 4c provided in the end region of the rotor shaft 4 facing the turbine part 5, which penetrates the turbine disk 5a in a central outlet opening 10, ultimately discharged into the environment, more precisely via the thrust nozzle of the small gas turbine, not shown here. Via the crossing point 4b of the rotor shaft 4, however, not only the combustion chamber leakage air 6a is discharged from the compressor back space 8, but also the fuel to be burned in the combustion chamber 1

5 Combustion chamber 1 supplied As is customary in small gas turbines with a singer combustion chamber, the fuel is ultimately directed to the combustion chamber 1 through a bore 11 in the compressor impeller 2a, which runs concentrically to the axis of rotation of the radial compressor 2 or the rotor shaft 4, or more precisely through a delivery pipe 12 then provided To this end mouths

I O in the starting area of the delivery pipe 12 on the left-hand side here is a fuel injection pipe 13 connected to a fuel pump (not shown) which, from a storage container (also not shown), requires the fuel for the operation of the small gas turbine

1 The fuel introduced in this way thus passes through the delivery pipe 12 (and in the exemplary embodiment according to FIGS. 1, 2 via a centrifugal siphon 14, which will be explained in more detail later) into a preferably central location in the intersection 4b of the rotor shaft 4, but away from the ventilation bores 9 provided distribution chamber 15, from which a plurality of supply bores 17 branching in 0 radial direction 16 branch off. These supply bores 17, which are also provided in the intersection 4b and are arranged offset to the ventilation bores 9, so that the supply bores 17 and the ventilation bores 9 do not intersect the fuel ultimately gets into the combustion chamber 1

25 three such supply bores 17 are provided evenly distributed over the circumference of the intersection part 4b

If the supply bores 17 were now mouthed directly in the combustion chamber 1, this would result in an especially at low speeds of the Kieingasurbine

30 insufficient atomization of the fuel. Therefore, the rotor shaft 4 in the area of the intersection part 4b completely surrounded by a so-called splash ring 18, which is at least slightly spaced from the rotor shaft 4 at least in the mouth area of the supply bores 17 and which rotates together with the rotor shaft 4 about the central axis 19 of the small gas turbine. The fuel emerging from the 5 supply bores 17 can thus be distributed within the spray ring 18 over its entire circumference (and thus also over the circumference of the rotor shaft 4) before it is then better distributed and thus atomized into the actual combustion chamber 1 or into the primary zone the same arrives.

I O

As can be seen from FIG. 2, the spray ring 18 is essentially trough-shaped on its side facing the supply bores 17, i.e. it forms a rotor shaft 4 with its upper side, delimited by its collar 18a, which is on the right here and is exposed to the combustion chamber 1

15 facing and rotating with respect to the rotor shaft 4 so-called splash ring pan 18b, within which the fuel emerging from the supply bores 17 can initially be distributed evenly over the inner circumference of the spray ring 18 due to centrifugal force before it actually reaches the primary zone of the combustion chamber 1. The latter takes place after the so-called. 0 splash ring trough 18b is completely filled with fuel, so that the fuel initially exits the spray ring trough 18b via the collar 18a in the opposite direction to the centrifugal force and then again under the influence of centrifugal force along the end face of the collar 18a to the outermost corner region of the spray ring 18 trained tear edge 18c, from which the

25 fuel then sprayed into the combustion chamber 1 atomized.

In the following we will now describe the centrifugal siphon 14 provided between the delivery pipe 12 and the distribution chamber 15 in the first exemplary embodiment according to FIG. 1, for the sake of clarity in particular reference is made to the enlarged illustration according to FIG. 2. The meaning of this F ekkraftiphons 14 is to seal the initial area of the fuel injection system, namely the fuel injection pipe 13 and the delivery pipe 12 with respect to the combustion chamber 1, in particular to ensure excellent controllability of the entire fuel injection system of the Kieingas turbine even at low speeds thereof and in addition to ensure the best possible possibility of a windmill start often sought for small gas turbines

As shown in FIG. 2, the fuel brought in through the injection pipe 13 exits the delivery pipe 12 again under the influence of centrifugal force onto the inner surface of a so-called distributor cone 20 and over it due to a baffle plate 21 provided in the intersection part 4b along the one between the free one End of the distributor cone 20 as well as the baffle plate 21, not specified in more detail, in the radial direction 16 outwards into an annular gap 22 surrounding the baffle plate 21 on the outside. From there, the fuel then moves inward along the side of the baffle plate 21 facing away from the distributor cone 20 in radial direction 16 , ie in the direction of the central axis 19 into the distribution chamber 15 already described

Furthermore, one can see in FIG. 2 more precisely a screw connection designated by reference numeral 23, via which the compressor impeller 2a is flanged to the rotor shaft 4 or to the intersection point 4b thereof. Furthermore, the flow path of the entry is already detailed in this FIG The combustion chamber leakage air 6a explained in more detail than shown in FIG. 1 As shown and as already mentioned, this combustion chamber leakage air 6a comes from the annulus designated by the reference number 24, that of the combustion chamber end wall 25, from a partition wall designated by the reference number 26 ( this is the non-rotating part of the Kieingas turbine already mentioned several times) and the flange-like crossing point 4b of the rotor shaft 4 is limited, via the gap 27 between the partition wall 26 and the crossing part 4b, which is sealed by the seal 7 provided there as a labyrinth seal, but which does not allow complete sealing, into the compressor rear space 8.

In this compressor rear chamber 8, the combustion chamber leakage air 6a mixes with a further air flow that comes in due to the different pressure conditions and can thereafter be provided through transition bores 29 in provided in the flange-like section 28 of the compressor impeller 2a that cooperates with the flange-like crossing part 4b the ventilation bores 9 already explained arrive, which in turn (in the exemplary embodiment according to FIGS. 1, 2, inclined with respect to the axial direction 3) open into the rotor inner space 4a.

In the embodiment according to FIG. 3, no centrifugal siphon described in connection with FIG. 2 is provided, so that the delivery pipe 12, which is preferably soldered into a suitable receptacle in the crossing part 4b, opens directly into the distribution chamber 15. Here too, the compressor impeller 2a is designed slightly differently, so that the ventilation bores 9, which branch off here from a chamber designated by the reference number 30, through which the delivery pipe 12 passes, run at least essentially in the axial direction 3. The combustion chamber leakage air 6a which is to be discharged from the compressor rear space 8 and possibly mixed with a further air flow also enters this chamber 30 via a transition bore again identified by the reference number 29. Also seen in FIG. 3 is a compression spring-loaded mechanical seal 31 provided at the upstream end of the delivery pipe 12 and surrounding the fuel injection pipe 13, by means of which the interior of the delivery pipe 12 is sealed from the surroundings. In the exemplary embodiment according to FIG. 4, a throttle point 32 is used in the supply bore (s) 17 for the fuel which is led through the supply bore 17 in the radial direction 16, here in the form of a suitably designed screwed-in throttle element. In this throttle point 32, a pressure gradient builds up under the influence of centrifugal force in the fuel injection system in the direction of the combustion chamber 1, which prevents combustion chamber air from pressing back into the delivery pipe 12. The mechanical seal 31 shown in FIG. 3 is therefore not necessary here.

In the two exemplary embodiments according to FIGS. 3, 4, the splash ring 18 is shaped somewhat differently than in the exemplary embodiment according to FIGS. 1, 2. This different shape also depends on the different design of the compressor impeller 2a or the flange-like section 28 the same together, as can be seen in the exemplary embodiments according to FIGS. 3, 4, the screw connection designated by the reference number 23 in FIG. 2 has been replaced by a welded connection, however this and a large number of further details, in particular of a constructive nature, can be designed quite differently from the exemplary embodiments shown be without leaving the content of the claims. With the measures described, both uniform fuel injection into the combustion chamber 1 and optimal ventilation of the compressor rear space 8 are always obtained. These advantages are particularly evident when the rotational speeds of the rotor shaft 4 are low and, at the same time, relatively large amounts of fuel are to be supplied to the combustion chamber 1 . Reference symbol list:

1 radial or Slinger combustion chamber, also called the combustion chamber

2 radial compressors 2a compressor impeller

3 axial direction

4 rotor shaft

4a interior of 4

4b (flange-like) crossing part of 4 4c discharge pipe

5 turbine part

5a turbine disc

6 Air flow supplied to the combustion chamber, promoted by 2 6a Combustion chamber leakage air 7 Seal in the gap between rotating and non-rotating parts

8 compressor back space

9 vent hole (in 4b)

10 (central) outlet opening (in FIG. 5a)

11 (central) bore in 2a, which receives 12 12 delivery pipe (for fuel, trending in 2a)

13 fuel injection tubes

14 centrifugal siphon

15 distribution chamber (for fuel, in 4b)

16 radial direction 17 supply bore (for fuel, in 4b)

18 thrower

18a bunch of 18

18b splash ring pan

18c tear-off edge 19 central axis (of the small gas turbine)

20 distributor cone

21 baffle plate

22 Annular gap

23 screw connection 24 annulus

25 combustion chamber end wall

26 partition

27 gap

28 section of 1 a 29 crossover hole

30 chamber

31 Mechanical seal

32 throttling point

Claims

claims

1 . Fuel injection system for a radial or Slinger combustion chamber of a small gas turbine with a radial compressor (2) or diagonal compressor upstream of the radial or Slinger combustion chamber (1) and a turbine part connected to the latter via a rotor shaft (4) running in the axial direction (3) (5), the fuel passing through a delivery pipe (12) provided in the impeller (2a) of the radial compressor / diagonal compressor into a crossing part (4b) of the rotor shaft (4) located in the region of the combustion chamber (1) near the compressor and essentially passing through it Supply bores (17) which run in the radial direction (16) are fed to the combustion chamber (1), and in the intersection part (4b) offset ventilation bores (9) are provided in the intersection part (4b) via which the bores into the compressor rear space (8) Combustion chamber leakage air (6a) enters the interior (4a) of the rotor shaft (4), which is hollow at least in sections, in order to pass through the se to be discharged into the environment through a particularly central outlet opening (10) in the turbine disc (5a), with a spray ring (18) completely surrounding the rotor shaft (4) in the area of the crossing part (4b), which is at least in the mouth area of the supply bores ( 17) is slightly spaced from the rotor shaft (4) and rotates together with it about the central axis (19) of the small gas turbine. The fuel injection system according to claim 1, wherein the spray ring (18) is trough-shaped on the side facing the supply bores (17) and is provided with a tear-off edge (18c) towards the combustion chamber (1).

Fuel injection system according to Claim 1 or 2, wherein a centrifugal siphon (14) upstream of the supply bores (17) is provided in or upstream of the crossing part (es) (4b).

Fuel injection system according to one of the preceding claims, wherein the in particular three supply bores (17), which are uniformly distributed over the circumference of the crossing part (4b), are each provided with a throttle point (32).