Lobe lance for a gas turbine combustor

Abstract

A lobe lance is disclosed for a gas turbine combustor which includes a plurality of N (N4) lobe fingers, each configured as a streamlined body with two lateral surfaces. A plurality of nozzles for injecting a gaseous and/or liquid fuel mixed with air are provided whereby lobes running between the nozzles are provided for improving the mixing quality and reducing pressure loss in said combustor. The lobes of each lobe finger have one of two opposite orientations with respect to said flow direction, and the lobes of all lobe fingers follow a predetermined pattern of orientation across the lobe fingers at least one pair of neighboring lobe fingers has the same lobe orientation resulting in a grouped lobe arrangement ( . . . LL . . . or . . . RR . . . ) such that at least two of the vortices generated by the lobe shape downstream of the lobe fingers combine.

Claims

1. A lobe lance for a gas turbine combustor, comprising: a plurality of N lobe fingers wherein N4, each of said lobe fingers is configured as a streamlined body which has a streamlined cross-sectional profile, said streamlined body has two surfaces parallel to a direction of hot gas flow, said surfaces being joined at respective upstream sides by a leading edge and being joined at respective downstream sides forming a trailing edge, each lobe finger including a plurality of nozzles for injecting a gaseous and/or liquid fuel mixed with air distributed along said trailing edge, and lobes running between said nozzles provided at said trailing edge for impacting the mixing quality and reducing pressure loss in said combustor, wherein the lobes of each lobe finger has one of two opposite orientations (R, L) with respect to the direction of hot gas flow, and the lobes of all lobe fingers follow a predetermined pattern of orientation across the lobe fingers, and at least two pairs of adjacent lobe fingers of the plurality of lobe fingers has the same lobe orientation resulting in a grouped lobe arrangement ( . . . LL . . . and . . . RR . . . ) such that at least two vortices generated downstream of said lobe fingers combine, wherein each lobe finger of the plurality of lobe fingers having a lobe orientation (R) has trailing edge lobes with an apex pointing in a right direction when looking downstream and each lobe finger of the plurality of lobe fingers with a lobe orientation (L) has trailing edge lobes with an apex pointing in a left direction when looking downstream, wherein N=NR+NL with NR being a number of lobe fingers of the plurality of lobe fingers having a first lobe orientation (R), and NL being the number of lobe fingers of the plurality of lobe fingers having a second lobe orientation (L) opposite to said first lobe orientation, and wherein NR and NL are both at least 2.

2. The lobe lance as claimed in claim 1, wherein N.sub.R and N.sub.L are within 1.

3. The lobe lance as claimed in claim 1, wherein said predetermined pattern of orientation is one of the following patterns: RR . . . RRLL . . . LL, LL . . . LLRR . . . RR, RR . . . RRLL . . . LLRR RR . . . RRLL . . . LLRR . . . RRLL . . . LL, LL . . . LLRR . . . RR LL . . . LLRR . . . RRLL . . . LLRR . . . RR, RRLL . . . LLRR RRLL . . . LLRR . . . RRLL, LLRR . . . RRLL LLRR . . . RRLL . . . RRLL, with N/2=N.sub.R=N.sub.L for N being an even number, or with N/2=N.sub.R+1=N.sub.L1 or N/2=N.sub.R1=N.sub.L+1 for N being an odd number.

4. The lobe lance as claimed in claim 3, wherein N=8, and that said predetermined pattern of orientation is one of the following patterns: RRRRLLLL, LLLLRRRR, RRLLRRLL, LLRRLLRR, RRLLLLRR, LLRRRRLL.

5. The lobe lance as claimed in claim 1, wherein N=4.

6. The lobe lance as claimed in claim 5, wherein said predetermined pattern of orientation is either RRLL or LLRR.

7. The lobe lance as claimed in claim 5, wherein said predetermined pattern of orientation is either RLLR or LRRL.

8. The lobe lance as claimed in claim 5, wherein said predetermined pattern of orientation is one of the following patterns: RRRL, RLLL, LLLR, LRRR, RRRR, LLLL.

9. The lobe lance as claimed in claim 1, wherein said plurality of lobe fingers are arranged between left and right side walls, and lobe fingers adjacent to said side walls have a predetermined lobe orientation according to one of the following schemes: (left wall) R . . . L (right wall), (left wall) L . . . R (right wall).

10. The lobe lance as claimed in claim 1, wherein each of said plurality of lobe fingers has an even number of nozzles, and lobe fingers have a predetermined lobe orientation according to the scheme (left wall) R . . . L (right wall).

11. The lobe lance as claimed in claim 1, wherein each lobe finger of the plurality of lobe fingers has a lobe finger chord bisecting the lobe finger from the leading edge to the trailing edge and the lobe finger chords of two of said lobe fingers are closer to each other at the trailing edge than at the leading edge.

12. A gas turbine comprising: the lobe lance of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.

(2) FIG. 1 is a perspective view of an exemplary gas turbine with sequential combustion of the type GT26;

(3) FIG. 2 shows a lobe lance for a secondary combustor of rectangular design according to an embodiment of the invention; and

(4) FIG. 3 shows in a view against hot gas flow direction four different possibilities of the lobe orientation of a lobe lance according to FIG. 2.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS OF THE INVENTION

(5) According to the invention grouped or alternating neighboring lobe fingers are the cause to have local combined vortices (grouped) or not (alternating); thus it defines the level of large scale mixing of fuel, cooling air and hot gas. The arrangement is defined based on the burner size and possible numbers of lobe fingers. With current rectangular sequential burner, a four finger arrangement is proper. However, the arrangements will not be limited to four finger arrangements.

(6) Within a reheat burner an arrangement of three lobe fingers behaves differently than an arrangement with four fingers or more. For such an arrangement grouped lobes allow the vortices to combine with each other (two or more vortices can combine into a single vortex) and thereby create large scale structures, which enhance mixing and are thus beneficial for NOx, CO and overall temperature distribution factor (OTDF).

(7) A lobe lance according to an example of the invention is shown in FIG. 2. Lobe lance 21 of FIG. 2, which is preferably to be used with a rectangular burner, comprises four separate fingers 22a-d extending in parallel between an upper plate 25 and a lower plate 26. Each finger 22 is configured as a streamlined body which has a streamlined cross-sectional profile (like an airfoil). The body has two lateral surfaces essentially parallel to an axial hot gas flow with flow direction 32, which passes through the lance between upper and lower plates 25, 26. The lateral surfaces are joined at their upstream side by a leading edge 23 and joined at their downstream side forming a trailing edge 24.

(8) A plurality of nozzles 27 for injecting a gaseous and/or liquid fuel mixed with air is distributed along the trailing edge 24. Each of said fingers 22 has an air plenum 30 for air supply, a gas plenum 31 for gaseous fuel supply, and a liquid fuel supply 29. Means for improving the mixing quality and reducing pressure loss in said secondary combustor are provided in the trailing edge region of said body in form of lobes 28 running between the nozzles 27 at the trailing edge 24.

(9) Lobes 28 of the various fingers 22 generate vortices in the downstream flow of the fuel/air mixture, whereby the vortex flow of the different fingers 22 interact with each other. This interaction, which is able to enhance the mixing effect, depends on the orientation of lobes 28 in each finger.

(10) As can be seen at the lobe lance 21 shown in FIG. 2, the lobes 28 of the different fingers 22a-d can have two different orientations. In this case, the lobes 28 of the left two fingers 22a and 22b have the same orientation, which is opposite to the orientation of the lobes 28 of the right two fingers 22c and 22d. The lobe orientation of fingers 22a and 22b is said to be R (for right), while the lobe orientation of fingers 22c and 22d is said to be L (for left).

(11) Suppose there are a number of N4 lobe fingers (N=4 in the case shown in FIG. 2). N.sub.R is the number of lobe fingers with lobe orientation R (N.sub.R<N), i.e. fingers having the trailing edge lobe pointing in right direction when looking in downstream direction. N.sub.L is the number of lobe fingers with lobe orientation L (N.sub.L=NN.sub.R), i.e. fingers having the trailing edge lobe pointing in left direction when looking in downstream direction.

(12) Thus, there are two opposite types of directions or orientations (R and L). The case where the lobes of two neighboring fingers have the same trailing edge direction or orientation is referred to as a grouped lobe arrangement ( . . . LL . . . or . . . RR . . .), while the cases where the lobes of two neighboring fingers have the opposite trailing edge direction or orientation is referred to as an alternating lobe arrangement ( . . . LR . . . or . . . RL . . . )

(13) These grouped and alternating lobes arrangements, where neighboring lobes shall have the same resp. opposite direction are object of the present invention.

(14) This includes that either all lobes have the same kind of orientation (N.sub.L=N or N.sub.R=N) or that there is an arbitrary mix of them (N.sub.L+N.sub.R=N with N.sub.L>0 and N.sub.R>0).

(15) For a Lobe Lance with N4 Lobe Fingers 22 the Situation is as Follows:

(16) With grouped lobe arrangement, the streamwise vortices generated by the lobe shape are in the same direction, which are observed to combine to bigger vortices, in case the shape of lobe and the distance between two lobe fingers is properly designed or adjusted.

(17) With alternating lobe arrangement, the streamwise vortices at the trailing edge are in different directions; therefore they do not combine.

(18) Thus, combined streamwise vortices make it possible to have large scale mixing in transverse direction, while the uncombined vortices in an alternating arrangement will only make small scale mixing.

(19) Furthermore, in order to avoid the flow getting asymmetric, it is preferred to have N.sub.RN.sub.L (preferably N.sub.R=N.sub.L).

(20) In general, the preferred combinations look like this: 1. RR . . . RRLL . . . LL, 2. LL . . . LLRR . . . RR, 3. RR . . . RRLL . . . LLRR( . . . RRLL . . . LL) 4. LL . . . LLRR . . . RR(LL . . . LLRR . . . RR) 5. RRLL . . . LLRR( . . . RRLL) 6. LLRR . . . RRLL( . . . RRLL)
with N/2=N.sub.R=N.sub.L for N being an even number, or with N/2=N.sub.R+0.5=N.sub.L0.5 or N/2=N.sub.R0.5=N.sub.L+0.5 for N being an odd number.

(21) As illustrations for the above described arrangements for N=8 the following arrangements might be used: 1. RRRRLLLL 2. LLLLRRRR 3. RRLLRRLL 4. LLRRLLRR 5. RRLLLLRR 6. LLRRRRLL

(22) Less preferable, particularly in burners with sidewalls, are arrangements with all lobes of the same type or arrangements which are completely asymmetric: RR . . . RR, (All of the same type) LL . . . LL, (All of the same type) RLRRLLLRL (example for an asymmetric case)

(23) For the Special Case of a Lobe Lance with N=4 Lobe Fingers 22 the Situation is as Follows:

(24) For the N=4 case the preferred variants of lobe orientation are: RRLL (see FIG. 2 and FIG. 3(a)), LLRR (see FIG. 3(b))

(25) These variants ensure that vortices combine to large structures, and symmetry of the flow is given. Given this, the RRLL variant currently is preferred for the implementation in a gas turbine.

(26) A limited but nevertheless useful combination of the vortices is given for the following versions, while flow symmetry is still kept valid. Such combinations are: RLLR, LRRL.

(27) Less preferable are variants where three lobe fingers (or four fingers) of the same type are side by side, with one (or no) alternating lobe finger: RRRL, RLLL, LLLR, LRRR, RRRR, LLLL.

(28) These variants introduce asymmetry into the flow and are therefore less preferable.

(29) The following give the mixing zone without vortex combination: RLRL (see FIG. 3(d)), LRLR (see FIG. 3(c)).

(30) Even less preferable are variants wherein only one out of the two middle lobe fingers is different to the other three fingers, since no symmetry is given and vortices cannot combine properly for half of the flow: RRLR, RLRR, LLRL, LRLL.

(31) When the lobe fingers 22a-d are arranged between side walls, there are two types of side finger orientations, using the first row of lobe trailing edge facing the left and right side wall as an example: (left wall) R . . . L (right wall) (left wall) L . . . R (right wall)

(32) For an even number of injector nozzles per lobe finger in terms of the mixing performance the first version R . . . L is preferred.

(33) Preferably, two or more of the lobe fingers are arranged such that their trailing edges are closer together than their leading edges (e.g. in FIG. 2). Preferably, two or more lobe fingers with the same orientation (LL, RR) are arranged such that their trailing edges are closer together than their leading edges. Each lobe finger has a chord stretching from its leading edge to its trailing edge. This chord would normally be substantially parallel to the hot gas flow, and would normally bisect a cross-section of the lobe finger. The lobe lance could have all the lobe fingers in this configuration, particularly when four lobe fingers are provided. When the trailing edges are closer together than the leading edges, the vortices are already moving towards one another at the lobe finger trailing edge, meaning that it is easier for the vortices to combine.

(34) The example shown in FIG. 2 is in a secondary combustor in a sequential combustion turbine. In some cases, such as single combustor turbines, this invention could be incorporated in a first stage combustor. In cases where three or more combustors are provided, the invention could be incorporated in the third or later stage.

LIST OF REFERENCE NUMERALS

(35) 10 gas turbine (GT, e.g. GT26) 11 rotor 12 casing 13 air inlet 14 compressor 15 combustor (annular, e.g. EV) 16 high pressure (HT) turbine 17 combustor (annular, e.g. secondary, e.g. SEV) 18 low pressure (LP) turbine 19 exhaust gas outlet 20 machine axis 21 lobe lance 22 finger 22a-d finger 23 leading edge 24 trailing edge 25 upper plate 26 lower plate 27 nozzle 28 lobe 29 liquid fuel supply 30 air plenum 31 gas plenum 32 direction (of hot gas flow)