Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1998-11-20
2001-05-01
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S737000, C431S007000
Reexamination Certificate
active
06223537
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
This invention relates generally to combustors for use with gas turbines. More particularly, the invention provides a compact, low emission catalytic combustor for gas turbines operable in automotive and other environments.
Catalytic combustion makes possible extremely low emissions of pollutants from gas-powered turbine generators, particularly of oxides of nitrogen (NOx). A properly designed catalytic combustor can deliver both low NOx and low carbon monoxide (CO) emissions over the full engine operating range, in contrast to conventional combustors which may suffer from high NOx or high CO at different points in the duty cycle. In addition, stability and acoustic problems often associated with alternative low-NOx combustors are avoided with catalytic combustion, as are the complications of variable geometry.
Catalytic combustion is possible only when the combustor inlet temperature exceeds a minimum value that is a function of the catalyst formulation. This is typically about 700 F. Thus, a conventional diffusion-flame preheater is required for engine starting and for accelerating the engine to the speed necessary to obtain an adequate combustor inlet temperature. Once this condition has been reached, the preheater can be shut off. At this point a separate fuel delivery system is used to introduce fuel into the premix duct, where the fuel is evaporated (if liquid rather than gaseous fuel is used) and mixed with the incoming air. The resulting fuel-air mixture is then introduced into the catalyst bed. When liquid fuel is used, complete evaporation of the fuel as well as thorough mixing of air and the fuel must be achieved within the premix duct in order to obtain minimum combustor emissions and to avoid damage to the catalyst bed. Similarly, when gaseous fuel is used, thorough mixing of air and the fuel must be achieved within the premix duct.
Within the catalyst bed, combustion is initiated by catalytic action near the bed walls. Once initiated, combustion is continued by homogeneous combustion in the gas phase. Ignition by the catalyst makes possible complete combustion at very low flame temperatures, which results in extremely low NOx production. Support of the flame by the catalyst also results in high efficiency combustion, which leads to low CO emissions. Thus, both NOx and CO can be kept low over a wide range of engine speeds and loads.
While catalytic combustion is not a new technology, the present invention provides a relatively small-sized catalytic combustor compared to earlier examples of such combustors. For example, in previous catalytic combustor designs, the preheater has typically been designed to be remote from the premix duct. This is because the recirculating flows that are necessary to support diffusion-flame combustion within the preheater cannot be tolerated within the premix duct. At the relatively high combustor inlet temperatures necessary for catalytic operation, autoignition of the fuel within the premix duct is a distinct possibility. Excessively recirculating flows within the premix duct can lead to long residence times for the air-fuel mixtures in the duct and result in a high probability of autoignition. However, autoignition must be avoided in low emission combustion because autoignition can result in high flame temperatures and thus high NOx production. For this reason the preheater has in the past typically been physically separated from the premix duct.
The present invention, in addition to enabling the construction of a relatively small catalytic combustor, also addresses the problem of meeting or exceeding stringent emissions standards. For example, emissions standards for the Ultra-Low Emissions Vehicle (ULEV) specify stringent emission limits over a complete driving cycle from engine startup to shutdown. Thus, the present invention was designed to provide low emissions not only from the catalyst, but also from the preheater during its ignition through the engine spoolup and warmup phases to the transition to catalytic operation.
BRIEF SUMMARY OF THE INVENTION
The invention disclosed herein is a relatively compact catalytic combustor for gas turbines used in such applications as hybrid electric vehicles, compact on-site power generation devices, and other situations where small size is a plus. A design feature that helps make possible the uniquely small size of the present catalytic combustor is the integration of the combustor's preheater and the premix duct. The preheater is grafted onto the inlet of the premix duct, which significantly shortens the overall package and enables use of a low-emission catalytic combustor for applications that, prior to the invention, would have been extremely inconvenient or not possible due to size constraints. Structurally, the combustor has a combustor can, an upstream end, an inner liner, and a chamber. The combustor can surrounds the inner liner and the inner liner surrounds the chamber. The chamber has a preheater portion and a premix duct portion, surrounded by the inner liner. A catalyst bed is located sequentially downstream from the upstream end. The preheater is a type of diffusion-flame burner having at least one preheater fuel nozzle and the premix duct includes a plurality of premix fuel nozzles. The premix duct portion of the inner liner has a diameter that is larger upstream of the premix fuel nozzles than downstream of the premix fuel nozzles. The inner liner further includes a plurality of primary air orifices for introducing air into the preheater portion of the chamber and a plurality of secondary air orifices for introducing air into the chamber downstream of the primary air orifices.
A further aspect of the invention relates to the conflicting requirements of the preheater and premix duct. The preheater, unlike the premix duct, must support a stable flame during its operation. The configuration of the disclosed catalytic combustor satisfies these conflicting requirements of the preheater and premix duct.
REFERENCES:
patent: 3846979 (1974-11-01), Pfefferle et al.
patent: 3943705 (1976-03-01), DeCorso et al.
patent: 4019316 (1977-04-01), Pfefferle
patent: 4118171 (1978-10-01), Flanagan et al.
patent: 4285193 (1981-08-01), Shaw et al.
patent: 5000004 (1991-03-01), Yamanaka et al.
patent: 5003768 (1991-04-01), Kappler
patent: 5026273 (1991-06-01), Cornelison
patent: 5431017 (1995-07-01), Kobayashi et al.
patent: 5452574 (1995-09-01), Cowell et al.
patent: 5634784 (1997-06-01), Pfefferle et al.
patent: 5685156 (1997-11-01), Willis et al.
patent: 5826429 (1998-10-01), Beebe et al.
patent: 1070127 (1980-01-01), None
patent: 0103159 (1984-03-01), None
patent: 106659 (1984-04-01), None
patent: 0356092 A1 (1990-02-01), None
Article: Catalytic Combustion for Gas Turbine Applications; Krill et al.; ASME publication; Jan. 11, 1979; 7 pp.
Article: Performance and Emissions of a Catalytic Reactor with Propane, Diesel and Jet A Fuels, David N. Anderson; Sep. 1977; NASA—Lewis Research Ctr., No.: NASA TM-73786; 13 pp.
Article: Design of a Catalytic Combustor for Heavy-Duty Gas Turbines; Touchton et al.; Journal of Engineering for Power, vol. 105; Oct. 1983; pp. 797-805.
Article: Development and Test of a Catalytic Combustor for an Automotive Gas Turbine; John J. Lipinski et al. ; ASME #98-GT-390; 10 pp.
Brine Philip J.
Buch Rajesh D.
Lester George R.
Lipinski John J.
AlliedSignal Power Systems
Ephraim Starr
Fischer Felix L.
Kim Ted
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