Combustion – Flame holder having protective flame enclosing or flame... – Including means feeding air axially spaced points of the flame
Reexamination Certificate
2000-05-25
2001-12-18
Lazarus, Ira S. (Department: 3743)
Combustion
Flame holder having protective flame enclosing or flame...
Including means feeding air axially spaced points of the flame
C431S154000, C431S190000, C431S010000, C060S759000, C060S039230
Reexamination Certificate
active
06331110
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and methods for adjusting the NO
x
level of emissions of heavy-duty gas turbines for emissions compliance without disassembly of the combustors and particularly relates to a mechanical arrangement enabling external access to the dilution air sleeves for the combustion chamber for adjusting the combustor dilution air flow hole areas and methods of adjustment.
Heavy-duty gas turbines employing dry low NO
x
combustion systems are typically installed with predetermined dilution flow hole areas for flowing compressor discharge air into the combustion liner to shape the gas temperature profile exiting the combustion system and provide reduced NO
x
emissions. Dilution air flow sleeves are typically provided and have a predetermined hole area for flowing compressor discharge air into the combustion liner. Not infrequently, however, and after installation of the turbine at the power generation site, the NO
x
emissions level is either too high or too low, with corresponding CO emissions level that is too high. This is a result of the normal variability of machine air flow fraction that is delivered to the combustor and the resulting variability of flame temperature in the NO
x
producing zones of the combustor.
Under those circumstances, the turbine is typically brought into NO
x
emissions compliance by removal of the combustion liners from the turbine and resizing the dilution holes to redistribute the combustor air flow. This procedure requires the physical removal of the combustion liner from the turbine with attendant removal of certain piping for fuel, as well as piping for oil and water systems and auxiliary air piping for atomization. It is also necessary to remove the heavy end cover of the combustor to gain access to the dilution holes. Further, there is the possibility of contaminating the fuel system in the process of removing and reassembling the various piping systems. Still further, this process can take between one to two weeks' time, during which there is a gas turbine outage, preventing the electricity provider from producing power during that period of time. Consequently, there is a need for a system which facilitates change of the combustor dilution hole areas without disassembly and subsequent reassembly of major portions of the combustor and in a reduced timeframe.
BRIEF SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, there is provided a mechanical arrangement enabling external access to the combustion chamber which facilitates changeover of combustor dilution hole areas to adjust the NO
x
levels without disassembly of the combustors. To accomplish this, the combustion liner and surrounding air flow sleeve have aligned radial openings at an axial location along the liner for admitting dilution air through dilution sleeves in the aligned radial openings into the combustion chamber. An outer casing surrounds the flow sleeve and defines with the flow sleeve an annular flow passage for flowing compressor discharge air through the dilution sleeves into the combustion chamber. The openings through the flow sleeve are provided with collars which form seats for receiving flanges of the dilution sleeves. The outer casing is also provided with a cylindrical boss or flange in line with the axes of the openings through the combustion liner and flow sleeve, affording access to the dilution sleeves externally of the combustor. A cover is releasably secured to the cylindrical flange, for example, by bolts, and a spring cooperates between the cover and the flange on each dilution sleeve to maintain the dilution sleeve in the aligned openings of the combustion liner and flow sleeve with the flange of the dilution sleeve seated on the collar.
Each dilution sleeve has a central opening of a predetermined area. In the event that the NO
x
emissions are out of compliance after initial installation of the gas turbine, the access covers to the installed dilution sleeves are removed and dilution sleeves having holes of different areas are inserted to provide more or less compressor discharge air flow through the sleeves into the combustion chamber. Particularly, after the NO
x
emissions of the newly installed turbine have been measured at the design operating conditions, the actual measured NO
x
emission level is compared with the required NO
x
emission level for compliance. If the measured NO
x
emissions deviate to the extent the turbine is out of compliance, an increase or decrease in the hole area of the installed dilution sleeves is calculated to arrive at a dilution hole area effective to provide a NO
x
emission level within the compliance range. Once the required dilution hole area is determined, the combustion covers are removed and a new set of dilution sleeves conforming to the new required hole area is provided. Alternatively, the initially installed set of dilution sleeves are machined to the required new dilution hole areas. In either case, the dilution sleeves with the required hole areas are inserted through the cylindrical bosses to seat on the collars about the openings in the flow sleeve and extend through the aligned openings through the flow sleeve and the combustion liner. The springs and covers are then reinstalled to secure the dilution sleeves in place with the properly sized dilution hole areas.
In a preferred embodiment according to the present invention, there is provided a combustor for a gas turbine comprising an outer casing, a flow sleeve within the outer casing defining an air flow passage with the outer casing, a combustion liner within the flow sleeve for flowing hot gases of combustion, at least one opening in each combustion liner and the flow sleeve, a dilution sleeve removably received within the openings of the combustion liner and the flow sleeve and an access port in the outer casing for access to the dilution sleeve, the dilution sleeve being sized for passage through the access port enabling insertion into or removal of the dilution sleeve from the openings.
In a further preferred embodiment according to the present invention, there is provided in a combustor for a gas turbine having a combustion liner defining a hot gas flow path, an outer casing, a flow sleeve between the outer casing and the liner defining a dilution air flow path therebetween, and openings through the flow sleeve and the liner for flowing dilution air in the dilution air flow path into the hot gas flow path, a method of adjusting the level of NO
x
emissions comprising the steps of (a) providing a dilution air flow sleeve in the openings having an air flow passage of a predetermined area, (b) measuring the NO
x
emissions from the gas turbine at design operating conditions, (c) determining a deviation of the measured NO
x
emissions from a predetermined desired level of NO
x
emissions, (d) ascertaining a predetermined area of a desired air flow passage through an air flow dilution sleeve based on the deviation and (e) installing an air flow dilution sleeve in the turbine having a flow area sized to provide at least approximately the desired level of NO
x
emissions.
REFERENCES:
patent: 3927520 (1975-12-01), Arvin et al.
patent: 3930368 (1976-01-01), Anderson et al.
patent: 4301657 (1981-11-01), Penny
patent: 4389848 (1983-06-01), Markowski et al.
patent: 5235805 (1993-08-01), Barbier et al.
patent: 5240404 (1993-08-01), Hemsath et al.
patent: 5454221 (1995-10-01), Loprinzo
patent: 5664412 (1997-09-01), Overton
patent: 985058 (1965-03-01), None
patent: 2 003 989-A (1979-03-01), None
McLeroy Jacob Tussey
Morton Harmon Lindsay
Steber Charles Evan
Cocks Josiah C.
General Electric Company
Lazarus Ira S.
Nixon & Vanderhye
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