Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1997-12-31
2001-06-05
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S748000, C060S752000, C239S400000
Reexamination Certificate
active
06240731
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to gas turbine engine combustors and more particularly to a low Nox combustor and method of operation.
BACKGROUND OF THE INVENTION
Gas turbine engines emit various pollutants including oxides of nitrogen (“NOx”). NOx is primarily formed through the thermal fixation of nitrogen and results from the high temperature combustion of fuel and air in the gas turbine engine. Environmental concerns and more stringent governmental regulation of NOx emissions have prompted designers to investigate various methods for reducing the generation of NOx by gas turbine engines. Examples of devices for reducing or controlling NOx are disclosed in the following commonly assigned patents: (1) Snyder et al., U.S. Pat. No. 5,256,352 issued Oct. 26, 1993 entitled Air-Liquid Mixer; (2) McVey et al., U.S. Pat. No. 5,263,325 issued Nov. 23, 1993 entitled Low Nox Combustion; and (3) Marshall, U.S. Pat. No. 5,406,799 issued Apr. 18, 1995 entitled Combustion Chamber.
Two basic approaches for a low NOx fuel injection system are (1) a locally lean stoichiometry system and (2) a locally rich stoichiometry system. It is desirable in a fuel rich approach to operate in the fuel spray equivalence ratio above 1.6 prior to rapidly quenching down to appropriate lean burning levels. The rich based system also requires a rapid mixing process controlled at some distance downstream of the fuel injection apparatus so that excessive Nox is not produced during the quenching process. However, the rich approach is susceptible to a potential increase in smoke. It is therefor desirable to provide a fuel-rich combustor system and method of operation which reduces Nox without a detrimental increase in smoke.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and improved combustor and method of operation which reduces NOx emission in a gas turbine engine.
Another object of the invention is to provide such a combustor which affords a rapid mixing process controlled at some distance downstream of the fuel injection mechanism.
Another object of the invention is to provide such a combustor which minimizes residence time at high temperature.
A still further object of the invention is to provide such a combustor which can achieve a coherent central flow structure downstream from the nozzle.
A still further object of the invention is to provide such a combustor which affords enhanced mixing so as to eliminate or substantially reduce fuel-rich regions to thereby control smoke.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
Accordingly, it has been found that the foregoing and related objects are attained and the disadvantages of the prior art are overcome in a combustor having first and second sidewalls connected to a dome to form an elongated combustion chamber with an upstream end and a downstream end. The dome wall is disposed at the upstream end of the chamber and has a predetermined dome height. A fuel injector/swirler apparatus is mounted in the dome and is configured to produce a fuel-rich, highly mixed fuel-air spray pattern with uniform distribution. The sidewalls contain an array of air inlets configured for introducing airflow into the combustion chamber sufficient to cause rapid mixing and quenching of the rich fuel-air mixture to a lean fuel-air mixture. The inlets are disposed to direct air into the fuel-air spray pattern and the inlets nearest the dome are positioned a first predetermined distance downstream from the dome. The predetermined distance is greater than 0.75 times the dome height.
In the method of the present invention for combusting fuel in the combustor of a gas turbine engine of the type having a combustor dome of predetermined height, a fuel injector/air swirler apparatus mounted in the dome and combustor side walls forming a combustion chamber, the method includes the steps of injecting fuel and a first predetermined amount of airflow into the combustion chamber to form a fuel-rich, highly-mixed, uniform distribution fuel-air spray pattern flowing downstream in the combustion chamber. A second predetermined amount of airflow is introduced into the fuel-air spray pattern from combustor air inlets positioned at a first predetermined distance downstream from frome the dome. The first predetermined distance is greater than 0.75 times the dome height and the second predetermined amount of airflow is that amount of dilution air sufficient to cause rapid mixing and quenching of the fuel-air mixture to a lean fuel-air mixture. In one embodiment of the invention, the fuel-air spray pattern is maintained for the first predetermined distance without the introduction into the fuel-spray pattern of additional airflow for mixing, conditioning or combustion.
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Hoke James B.
Segalman Irving
Siskind Kenneth S.
Smith Reid D. C.
Cummings Ronald G.
Kim Ted
United Technologies Corporation
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