Power plants – Combustion products used as motive fluid – With variable oxidizer control
Reexamination Certificate
1999-02-16
2001-08-14
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
With variable oxidizer control
C060S725000, C060S737000
Reexamination Certificate
active
06272842
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to industrial turbine engines, and more specifically, to combustors therein.
Industrial power generation gas turbine engines include a compressor for compressing air that is mixed with fuel and ignited in a combustor for generating combustion gases. The combustion gases flow to a turbine that extracts energy for driving a shaft to power the compressor and produces output power for powering an electrical generator, for example. The turbine is typically operated for extended periods of time at a relatively high base load for powering the generator to produce electrical power to a utility grid, for example. Exhaust emissions from the combustion gases are therefore a concern and are subjected to mandated limits.
More specifically, industrial gas turbine engines typically include a combustor design for low exhaust emissions operation, and in particular for low NOx operation. Low NOx combustors are typically in the form of a plurality of burner cans circumferentially adjoining each other around the circumference of the engine, each burner can having a plurality of premixers joined to the upstream end. Additionally, the combustors may comprise an annular arrangement.
Lean-premixed low NOx combustors are more susceptible to combustion instabilities as represented by dynamic pressure oscillations in the combustion chamber. The pressure oscillations, if excited, can cause undesirably large acoustic noise and accelerated high cycle fatigue damage to the combustor. The pressure oscillations can occur at various fundamental or predominant resonant frequencies and other higher order harmonics.
Such combustion instabilities may be reduced by introducing asymmetry in the heat release or for example by axially distributing or spreading out the heat release. One current method commonly used to introduce asymmetry for reducing combustion oscillations is to bias fuel to one or more burners generating more local heat release. Although this fuel-biasing method has been shown to reduce combustion instabilities, NOx emissions are substantially increased by the higher temperatures generated. Distributing the flame axially has been accomplished by physically offsetting one or more fuel injectors within the combustion chamber. A drawback to this offset approach, however, is that the extended surface associated with the downstream injectors must be actively cooled to be protected from the upstream flame. This additional cooling air has a corresponding NOx emissions penalty for the system.
Therefore, it is apparent from the above that there is a need in the art for improvements in combustor dynamics.
SUMMARY OF THE INVENTION
A variable length pre-mixer assembly comprises an upstream end for receiving compressed air from a compressor and a downstream end disposed in flow communication with a combustor. Pre-mixer assembly comprises an upstream forward clamp, a swirler assembly having a plurality of circumferentially spaced apart vanes disposed adjacent the upstream end for swirling compressed air channeled therethrough. An elongate centerbody has a first end joined to and extending through the swirler and a second end disposed downstream therefrom. A downstream fuel nozzle shroud has an outlet in flow communication with the combustor. Additionally, at least one removably disposed fuel nozzle spacer is alternatively disposed between a first position between the upstream forward clamp and the swirler assembly and a second position between the swirler assembly and the downstream fuel nozzle so as to change the relative position of the swirler assembly and alter the pre-mixer assemblies acoustical resonance characteristics.
REFERENCES:
patent: 3905192 (1975-09-01), Pierce et al.
patent: 4532762 (1985-08-01), Mongia et al.
patent: 4967550 (1990-11-01), Acton et al.
patent: 5005353 (1991-04-01), Acton et al.
patent: 5082421 (1992-01-01), Acton et al.
patent: 5141391 (1992-08-01), Acton et al.
patent: 5211004 (1993-05-01), Black
patent: 5357743 (1994-10-01), Zarzalis et al.
patent: 5373693 (1994-12-01), Zarzalis et al.
patent: 5428951 (1995-07-01), Wilson et al.
patent: 5664412 (1997-09-01), Overton
patent: 5685157 (1997-11-01), Pandalai et al.
patent: 5809769 (1998-09-01), Richards et al.
patent: 5822992 (1998-10-01), Dean
patent: 5918459 (1999-07-01), Nakae
patent: 5943866 (1999-08-01), Lovett et al.
General Electric Company
Patnode Patrick K.
Stoner Douglas E.
Thorpe Timothy S.
Torrente David J.
LandOfFree
Combustor tuning does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Combustor tuning, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combustor tuning will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2495696