(19)
(11)EP 2 282 119 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
03.08.2016 Bulletin 2016/31

(21)Application number: 10183465.3

(22)Date of filing:  26.08.2004
(51)International Patent Classification (IPC): 
F23R 3/28(2006.01)
F23M 20/00(2014.01)
F23R 3/60(2006.01)

(54)

Combustion liner cap assembly for combustion dynamics reduction

Brennkammerkappe zur Verminderung der Verbrennungsdynamik

Calotte de chambre de combustion pour diminuer la dynamique de la combustion


(84)Designated Contracting States:
DE FR GB IT

(30)Priority: 28.08.2003 US 650194

(43)Date of publication of application:
09.02.2011 Bulletin 2011/06

(62)Application number of the earlier application in accordance with Art. 76 EPC:
04255145.7 / 1510760

(73)Proprietor: General Electric Company
Schenectady, NY 12345 (US)

(72)Inventors:
  • Crawley, Bradley Donald
    Simpsonville, SC 29681 (US)
  • Fossum, James
    Greer, SC 29651 (US)

(74)Representative: Bedford, Grant Richard 
GPO Europe GE International Inc. The Ark 201 Talgarth Road Hammersmith
London W6 8BJ
London W6 8BJ (GB)


(56)References cited: : 
US-A- 2 775 094
US-B2- 6 502 825
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The invention relates to gas and liquid fueled turbines and, more particularly, to combustors and a combustion liner cap assembly in industrial gas turbines used in power generation plants.

    [0002] A combustor typically includes a generally cylindrical casing having a longitudinal axis, the combustor casing having fore and aft sections secured to each other, and the combustion casing as a whole secured to the turbine casing. Each combustor also includes an internal flow sleeve and a combustion liner substantially concentrically arranged within the flow sleeve. Both the flow sleeve and combustion liner extend between a double walled transition duct at their forward or downstream ends with a sleeve cap assembly (located within a rearward or upstream portion of the combustor) at their rearward ends. The flow sleeve is attached directly to the combustor casing, while the liner receives the liner cap assembly which, in turn, is fixed to the combustor casing. The outer wall of the transition duct and at least a portion of the flow sleeve are provided with air supply holes over a substantial portion of their respective surfaces, thereby permitting compressor air to enter the radial space between the combustion liner and the flow sleeve, and to be reverse flowed to the rearward or upstream portion of the combustor where the air flow direction is again reversed to flow into the rearward portion of the combustor and towards the combustion zone.

    [0003] A plurality (e.g., five) of diffusion/premix fuel nozzles are arranged in a circular array about the longitudinal axis of the combustor casing. These nozzles are mounted in a combustor end cover assembly which closes off the rearward end of the combustor. Inside the combustor, the fuel nozzles extend into a combustion liner cap assembly and, specifically, into corresponding ones of the premix tubes. The forward or discharge end of each nozzle terminates within a corresponding premix tube, in relatively close proximity to the downstream end of the premix tube which opens to the burning zone in the combustion liner. An air swirler is located radially between each nozzle and its associated premix tube at the rearward or upstream end of the premix tube, to swirl the compressor air entering into the respective premix tube for mixing with premix fuel. Such a combustor is known for example, from US 6502825 B2.

    [0004] High combustion dynamics in a gas turbine combustor can cause disadvantages such as preventing operation of the combustion system at optimum (lowest) emissions levels. High dynamics can also damage hardware to a point that could result in a forced outage of the gas turbine. Hardware damage that does occur but does not cause a forced outage increases repair costs. Several corrective actions have been considered for reducing combustion dynamics in a gas turbine combustor. Tuning through fuel split changes, control changes and nozzle resizing have been tried with varying degrees of success. Often, a combination of these and other efforts is made to provide the best overall solution. Tuning and control setting changes are considered normal approaches to mitigating combustion dynamics as they are relatively simple changes to make when compared to other more costly and intrusive approaches such as changing hardware. Limitations do exist, however, as it is not only combustion dynamics that must be considered when tuning fuel splits or adjusting control settings. The effects on emissions (NOx, CO, and UHC), output, heat rate, exhaust temperature, fuel mode transfers, and turndown should all be considered when using these methods to mitigate dynamics and always involves a trade-off.

    [0005] Nozzle resize is also an option sometimes used to deal with high dynamics but is typically reserved for use when the fuel composition has changed significantly from the design point. Also costly and time-consuming, this option has the disadvantage of having only a certain range of application based on the design pressure ratio range of the nozzle. A further change in fuel composition could once again require a different nozzle if the dynamics could not be tuned.

    [0006] The design space is typically a last resort in dynamics mitigation at this stage due to the high cost normally associated with the development of a new piece of hardware. The goal is to lower dynamics without impacting the emissions, output, heat rate, exhaust temperature, mode transfer capability, and turndown that are often affected by the normal dynamics mitigation methods. For the most part, a more design oriented approach using small changes such as the cap modification decouples those parameters from the objective of reducing dynamics.

    [0007] According to the invention, a method of decreasing combustion dynamics in a gas turbine is provided, the gas turbine including a combustion liner cap assembly including a cylindrical outer sleeve supporting internal structure therein, and a plurality of fuel nozzle openings formed through the internal structure, wherein a first set of circumferentially spaced cooling holes is formed through the cylindrical outer sleeve; the method comprising increasing airflow through the combustion liner cap assembly to stabilize the combustion flame by forming a second set of circumferentially spaced cooling holes through the cylindrical outer sleeve, wherein the second set of cooling holes is axially spaced from the first set of cooling holes, so as to reduce one of the characteristic combustion dynamic frequencies of the gas turbine.

    [0008] Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

    FIGURE 1 is a partial cross-section of a gas turbine combustor;

    FIGURE 2 is a perspective view of a combustion liner cap assembly; and

    FIGURE 3 is a close-up view showing the additional cooling holes in the liner cap outer body sleeve.



    [0009] With reference to FIG. 1, the gas turbine 10 includes a compressor 12 (partially shown), a plurality of combustors 14 (one shown), and a turbine represented here by a single blade 16. Although not specifically shown, the turbine is drivingly connected to the compressor 12 along a common axis. The compressor 12 pressurizes inlet air which is then reverse flowed to the combustor 14 where it is used to cool the combustor and to provide air to the combustion process.

    [0010] As noted above, the gas turbine includes a plurality of combustors 14 located about the periphery of the gas turbine. A double-walled transition duct 18 connects the outlet end of each combustor with the inlet end of the turbine to deliver the hot products of combustion to the turbine.

    [0011] Ignition is achieved in the various combustors 14 by means of spark plug 20 in conjunction with cross fire tubes 22 (one shown) in the usual manner.

    [0012] Each combustor 14 includes a substantially cylindrical combustion casing 24 which is secured at an open forward end to the turbine casing 26 by means of bolts 28. The rearward end of the combustion casing is closed by an end cover assembly 30 which may include conventional supply tubes, manifolds and associated valves, etc. for feeding gas, liquid fuel and air (and water if desired) to the combustor. The end cover assembly 30 receives a plurality (for example, five) fuel nozzle assemblies 32 (only one shown with associated swirler 33 for purposes of convenience and clarity) arranged in a circular array about a longitudinal axis of the combustor.

    [0013] Within the combustor casing 24, there is mounted, in substantially concentric relation thereto, a substantially cylindrical flow sleeve 34 which connects at its forward end to the outer wall 36 of the double walled transition duct 18. The flow sleeve 34 is connected at its rearward end by means of a radial flange 35 to the combustor casing 24 at a butt joint 37 where fore and aft sections of the combustor casing 24 are joined.

    [0014] Within the flow sleeve 34, there is a concentrically arranged combustion liner 38 which is connected at its forward end with the inner wall 40 of the transition duct 18. The rearward end of the combustion liner is supported by a combustion liner cap assembly 42 as described further below, and which, in turn, is secured to the combustor casing at the same butt joint 37. It will be appreciated that the outer wall 36 of the transition duct 18, as well as that portion of flow sleeve 34 extending forward of the location where the combustion casing 24 is bolted to the turbine casing (by bolts 28) are formed with an array of apertures 44 over their respective peripheral surfaces to permit air to reverse flow from the compressor 12 through the apertures 44 into the annular (radial) space between the flow sleeve 34 and the liner 36 toward the upstream or rearward end of the combustor (as indicated by the flow arrows shown in FIG. 1).

    [0015] FIG. 2 is a perspective view of the combustion liner cap assembly 42. The details of the assembly 42 are generally known and do not specifically form part of the present invention. As shown, the combustion liner cap assembly 42 includes a generally cylindrical outer sleeve 50 supporting known internal structure 52 therein. A plurality of fuel nozzle openings 54 are formed through the internal structure as is conventional.

    [0016] With reference to FIG. 3, a first set of circumferentially spaced cooling holes 56 is formed through the cylindrical outer sleeve 50. These conventional holes permit compressor air to flow into the liner cap assembly. In order to increase air flow through the cap effusion plate, a second set of circumferentially spaced cooling holes 58 is formed through the cylindrical outer sleeve 50, where the cooling holes are preferably axially spaced from the first set of cooling holes 56. Preferably, eight cooling holes 58 are included in the second set and have a diameter of about 0.01905m (0.75 inches). The second set of cooling holes 58 enables increased air flow for better stabilizing the combustion flame. In an exemplary application, the modification reduces one of the three characteristic tones of the DLN2+ combustion system which allows easier optimization of the remaining two tones during the integrated tuning process. That is, the DLN2+ combustion system has three characteristic combustion dynamics frequencies. This modification reduces one of those tones. Normal tuning methods of fuel split and purge adjustments can then be used to reduce the remaining two tones. The reduction in combustion dynamics improves or allows for easier tuning of the units and leads to reduced repair and replacement costs since elevated dynamics levels can decrease hardware life and possibly lead to hardware failure. The construction results in a simplified resolution to problems of existing configurations and is retrofittable to current designs.

    [0017] The construction can also be returned to the original configuration by covering the second set of cooling holes 58 if deemed necessary without affecting the air flow to the original holes 56. That is, the holes added by this design improvement could be repaired by welding a metal disc or the like over the hole to block the airflow into the hole. The configuration and functionality of the part is then returned to the original design configuration.


    Claims

    1. A method of decreasing combustion dynamics in a gas turbine, the gas turbine including a combustion liner cap assembly (42) including a cylindrical outer sleeve (50) supporting internal structure (52) therein, and a plurality of fuel nozzle openings (54) formed through the internal structure, wherein a first set of circumferentially spaced cooling holes (56) is formed through the cylindrical outer sleeve; and the method comprising
    increasing airflow through the combustion liner cap assembly to stabilize the combustion flame by forming a second set of circumferentially spaced cooling holes (58) through the cylindrical outer sleeve, wherein the second set of cooling holes is axially spaced from the first set of cooling holes, so as to reduce one of the characteristic combustion dynamic frequencies of the gas turbine.
     
    2. A method according to claim 1, wherein the forming step is practiced such that the second set of cooling holes (58) may be rendered ineffective.
     


    Ansprüche

    1. Verfahren zum Verringern der Verbrennungsdynamik in einer Gasturbine, wobei die Gasturbine eine Flammrohrkappenbaugruppe (42) enthält, die eine zylindrische äußere Hülse (50), in der eine innere Struktur (52) gestützt wird; und mehrere Brennstoffdüsenöffnungen (54), die durch die innere Struktur hindurch ausgebildet sind, wobei eine erster Satz entlang des Umfangs beabstandeter Kühllöcher (56) durch die zylindrische äußere Hülse hindurch ausgebildet sind, und das Verfahren Folgendes umfasst:

    Erhöhen des Luftstromes durch die Flammrohrkappenbaugruppe zum Stabilisieren der Verbrennungsflamme durch Ausbilden eines zweiten Satzes entlang des Umfangs beabstandeter Kühllöcher (58) durch die zylindrische äußere Hülse hindurch, wobei der zweite Satz Kühllöcher axial von dem ersten Satz Kühllöcher beabstandet ist, um eine der kennzeichnenden verbrennungsdynamischen Frequenzen der Gasturbine zu verringern.


     
    2. Verfahren nach Anspruch 1, wobei der Schritt des Ausbildens dergestalt ausgeführt wird, dass der zweite Satz Kühllöcher (58) wirkungslos bleiben kann.
     


    Revendications

    1. Procédé de réduction de la dynamique de combustion dans une turbine à gaz, la turbine à gaz comprenant un ensemble de calotte de chemisage de chambre de combustion (42) comprenant une gaine cylindrique externe (50) qui y supporte la structure interne (52) et une pluralité d'ouvertures de buse à carburant (54) formées à travers la structure interne, dans lequel un premier ensemble de trous de refroidissement (56) espacés sur la circonférence est formé à travers la gaine cylindrique externe ; le procédé comprenant :

    l'augmentation de l'écoulement d'air à travers l'ensemble de calotte de chemisage de chambre de combustion pour stabiliser la flamme de combustion en formant un second ensemble de trous de refroidissement (58) espacés sur la circonférence à travers la gaine cylindrique externe, dans lequel le second ensemble de trous de refroidissement est espacé axialement du premier ensemble de trous de refroidissement de manière à réduire l'une des fréquences de combustion dynamiques caractéristiques de la turbine à gaz.


     
    2. Procédé selon la revendication 1, dans lequel l'étape de formation est mise en oeuvre de sorte que le second ensemble de trous de refroidissement (58) puisse être rendu inopérant.
     




    Drawing











    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description