Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1999-03-17
2001-10-16
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S748000
Reexamination Certificate
active
06301899
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a combustor of a turbine engine and, more particularly, to a combustor premixer.
In a typical aero-derivative industrial gas turbine engine, fuel is burned in an annular combustor. The fuel is metered and injected into the combustor by multiple nozzles along with combustion air having a designated amount of swirl. Non-uniformity of the fuel/air mixture causes the flame to be locally hotter, leading to significantly enhanced production of NOx. As herein used, the term “fuel/air mixture” is defined as a mixture of air and fuel for combustion.
In the typical turbine engine, flame stability and engine operability dominate the combustor design requirements. These requirements have in general resulted in combustor designs with the combustion at the dome end of the combustor proceeding at the highest possible temperatures at stoichiometric conditions. Additionally, designs that optimize flame stability and engine operability typically do not minimize production of NOx.
To reduce the production of NOx, hollow vane mixers have been used for fuel injection. Such a mixer includes an outer annular swirler and an inner annular swirler. The outer annular swirler includes hollow vanes with internal cavities and gas fuel passages for injecting gas fuel into the air stream. Using such a mixer, the high pressure air and the fuel is uniformly mixed, resulting in reduced formation of pollutants when the fuel/air mixture is exhausted out the downstream end of the mixing duct into the combustor and ignited. Such hollow vanes are used in both single fuel and dual fuel mixers.
Although the above described mixer satisfies the technical requirements of very low emissions, the mixer is complex and costly to fabricate, particularly the hollow swirl vanes. The hollow vane fabrication process includes time-consuming, intricate machining processes which result in reduced manufacturing yield. Further, as compared to a solid vane swirler, the reliability of the hollow vane swirler is reduced due to the potential for cracking around the injection openings and in the vane walls.
It is desirable to reduce the cost and improve the reliability of mixers. Such a mixer, however, must maintain acceptable combustion performance and emission levels.
SUMMARY OF THE INVENTION
In accordance with the instant invention, a combustor comprises a hollow body defining a combustion chamber. The hollow body is typically annular in form and includes an outer liner, an inner liner, and an upstream dome plate. Mounted to the dome plate is a swirl cup with a mixer disposed therein to provide uniform mixing of fuel and air. The mixer comprises an inner swirler and an outer swirler that are mounted in the swirl cup. The outer swirler typically includes solid vanes. A shroud surrounds the mixer at the upstream end, which shroud includes an annular fuel chamber. The shroud further comprises a plurality of axial fuel injection openings that provide flow communication between the annular fuel chamber and the mixer and radially inject fuel within the mixer. The use of solid vanes within the combustor significantly reduces the fabrication time and costs associated with the mixer, and also significantly reduces the possibility for vane cracking, thereby improving the reliability of the mixer. In addition, by radially injecting fuel through axial fuel injection openings, the desired combustion performance and yield emissions of such a solid vane mixer are achieved.
REFERENCES:
patent: 4426841 (1984-01-01), Cornelius et al.
patent: 5351477 (1994-10-01), Joshi et al.
patent: 5435126 (1995-07-01), Beaudoin
patent: 5778676 (1998-07-01), Joshi et al.
patent: 6070410 (2000-06-01), Dean
Dean Anthony John
Goebel Steven George
Freay Charles G.
General Electric Company
Patnode Patrick K.
Stoner Douglas E.
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