Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
2002-07-15
2004-04-20
Yu, Justine R. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S735000, C060S740000
Reexamination Certificate
active
06722132
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a fuel and air injection apparatus and method of operation for use in a gas turbine combustor for power generation and more specifically to a device that reduces the emissions of nitrogen oxide (NOx) and other pollutants by injecting gaseous fuel into a combustor in a premix condition while including liquid fuel capability.
2. Description of Related Art
In an effort to reduce the amount of pollution emissions from gas-powered turbines, governmental agencies have enacted numerous regulations requiring reductions in the amount of emissions, especially nitrogen oxide (NOx) and carbon monoxide (CO). Lower combustion emissions can be attributed to a more efficient combustion process, with specific regard to fuel injectors and nozzles. Early combustion systems utilized diffusion type nozzles that produce a diffusion flame, which is a nozzle that injects fuel and air separately and mixing occurs by diffusion in the flame zone. Diffusion type nozzles produce high emissions due to the fact that the fuel and air burn stoichiometrically at high temperature. An improvement over diffusion nozzles is the utilization of some form of premixing such that the fuel and air mix prior to combustion to form a homogeneous mixture that bums at a lower temperature than a diffusion type flame and produces lower NOx emissions. Premixing can occur either internal to the fuel nozzle or external thereto, as long as it is upstream of the combustion zone. Some examples of prior art found in combustion systems that utilize some form of premixing are shown in
FIGS. 1 and 2
.
Referring to
FIG. 1
, a fuel nozzle
10
of the prior art for injecting fuel and air is shown. This fuel nozzle includes a diffusion pilot tube
11
and a plurality of discrete pegs
12
, which are fed fuel from conduit
13
. Diffusion pilot tube
11
injects fuel at the nozzle tip directly into the combustion chamber through swirler
14
to form a stable pilot flame. Though this pilot flame is stable, it is extremely fuel rich and upon combustion with compressed air, this pilot flame is high in nitrogen oxide (NOx) emissions.
Another example of prior art fuel nozzle technology is the fuel nozzle
20
shown in
FIG. 2
, which includes a separate, annular manifold ring
21
and a diffusion pilot tube
22
. Fuel flows to the annular manifold ring
21
and diffusion pilot tube
22
from conduit
23
. Diffusion pilot tube
22
injects fuel at the nozzle tip directly into the combustion chamber through swirler
24
. Annular manifold ring
21
provides an improvement over the fuel nozzle of
FIG. 1
by providing an improved fuel injection pattern and mixing via the annular manifold instead of through radial pegs. The fuel nozzle shown in
FIG. 2
is described further in U.S. Pat. No. 6,282,904, assigned to the same assignee as the present invention. Though this fuel nozzle attempts to reduce pollutant emissions over the prior art, by providing an annular manifold to improve fuel and air mixing, further improvements are necessary regarding a significant source of emissions, the diffusion pilot tube
22
. The present invention seeks to overcome the shortfalls of the fuel nozzles described above by providing a fuel nozzle that is completely premixed in the gas circuit, thus eliminating all sources of high NOx emissions, while providing the option for dual fuel operation through the addition of liquid fuel and water passages.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to provide a fuel nozzle for a gas turbine engine that reduces NOx and other air pollutants during gas operation.
It is another object of the present invention to provide a premixed fuel nozzle with an injector assembly comprising a plurality of radially extending fins to inject fuel and air into the combustor such that the fuel and air premixes, resulting in a more uniform injection profile for improved combustor performance.
It is yet another object of the present invention to provide, through fuel hole placement, an enriched fuel air shear layer to enhance combustor lean blowout margin in the downstream flame zone.
It is yet another object of the present invention to provide a fuel nozzle for a gas turbine engine that is premixed when operating on gaseous fuel and has the additional capability of operating on liquid fuel.
It is yet another object of the present invention to provide a premixed fuel nozzle with improved combustion stability through the use of a plurality of fuel injection orifices located along a conical surface of the premixed fuel nozzle.
In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.
REFERENCES:
patent: 4850194 (1989-07-01), Fuglistaller et al.
patent: 4982570 (1991-01-01), Waslo et al.
patent: 5199265 (1993-04-01), Borkowicz
patent: 6070411 (2000-06-01), Iwai et al.
patent: 6282904 (2001-09-01), Kraft et al.
patent: 6357237 (2002-03-01), Candy et al.
patent: 2002/0092302 (2002-07-01), Johnson et al.
U.S. patent application Ser. No. 09/706,425, Kraft et al.
Jennings Stephen T.
Mack Brian R.
McMahon Ryan
Stuttaford Peter
Mack Brian R.
Power Systems MFG, LLC
Rodriguez William H.
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