Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-08-19
2001-06-26
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039281
Reexamination Certificate
active
06250063
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and methods for staging the flow of fuel to the nozzles of a gas turbine combustor.
BRIEF SUMMARY OF THE INVENTION
Gas turbines generally have a plurality of combustors arranged in an annular array about the axis of the turbine for generating hot gases of combustion for flow through the turbine. Each combustor typically has a plurality of nozzles, for example, five or six nozzles, for flowing the gaseous fuel into the combustor. As well known, the combustors of a gas turbine must operate over a wide range of fuel/air ratios. The fuel/air ratio, for example, is low during turbine start-up and low-load operation and is high during high-load operation. Low fuel/air ratios, however, affect combustor flame stability. One approach to enhancing flame stability is to bias the fuel flow to some of the fuel nozzles in a combustor and cut off fuel flow entirely to one or more of the other nozzles. The combustion flame near the nozzles with increased fuel flow are thus at higher fuel/air ratios and, consequently, more stable.
The individual nozzles of each combustor are typically connected to a common fuel supply manifold. The main fuel control valve for the turbine regulates the flow of fuel to the manifold. Staging fuel to different groups of nozzles traditionally requires separate fuel supply manifolds and control valves for each group. While these have afforded flexibility in fueling each nozzle group, they have disadvantages. First, it adds significant cost and complexity to the turbine. Secondly, the response time to fill a large empty manifold hampers smooth turbine operation. Thirdly, purging fuel from previously fueled manifolds requires additional valves and piping. Finally, continuous purging of the unfueled manifolds may require an additional system to prevent condensation buildup.
In certain cases, on/off fuel control to some of the nozzles in each combustor is adequate to extend combustor operating capability. For example, passive pressure actuated valves located on or near the combustor may be opened or closed when a certain fuel pressure is reached. Passive valving, however, does not provide sufficient flexibility throughout the range of combustor operation and does not afford valve actuation with sufficient precision. That is, passive valving permits non-uniform movement of valve members, i.e., poppet valves, and permits varying fuel pressure from one nozzle to the next. Additionally, the passive valve springs are different and have non-uniform spring forces. For these and other reasons, spring actuated passive valves do not actuate simultaneously nor do such valves permit valve operation at more than one machine operation condition. By requiring the passive valves to actuate at a certain machine condition, the valves do not have the ability to operate at other machine conditions. Consequently, there is a need for a fuel control system for actively and selectively supplying fuel to one or more nozzles in each combustor and cutting off fuel supplied to one or more other nozzles of the same combustor and to do so at selected operating parameters.
In a preferred embodiment according to the present invention, there is provided a method of operating a fuel system for the nozzles of a gas turbine combustor, comprising the steps of (a) providing fuel under pressure for distribution to a plurality of fuel nozzles of the combustor and (b) positively and remotely controlling the distribution of the fuel to selectively supply fuel to a first group of one or more nozzles of the combustor and cutting off fuel flow to a second group of one or more nozzles of the combustor not including nozzles of the first group.
In a further preferred embodiment according to the present invention, there is provided a fuel system for a gas turbine, comprising a plurality of combustors each having a plurality of fuel nozzles, a fuel supply conduit for the nozzles of at least one of the combustors, a fuel distribution valve in the supply conduit and having a plurality of outlet ports for communicating fuel from the valve to the nozzles of the one combustor, the valve including a valve member movable between a first position for supplying fuel to the plurality of nozzles of the one combustor and a second position for supplying fuel to a first group of one or more nozzles of the plurality thereof, and cutting off fuel to a second group of one or more nozzles of the plurality thereof and a remote control for moving the valve member between the open and closed positions.
REFERENCES:
patent: 4027474 (1977-06-01), Demase
patent: 4337616 (1982-07-01), Downing
Balevic David Justin
Beaudoin Ronald Joseph
Davis, Jr. Lewis Berkley
Mick Warren James
Gartenberg Ehud
General Electric Co.
Nixon & Vanderhye
Thorpe Timothy S.
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