Power plants – Combustion products used as motive fluid – With addition of steam and/or water
Reexamination Certificate
1999-05-21
2001-09-18
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
With addition of steam and/or water
Reexamination Certificate
active
06289668
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of combustion technology, and more particularly to an arrangement for the selective introduction of fuel and/or water into a combustion chamber.
BACKGROUND OF THE INVENTION
In gas turbines as used for the generation of electrical energy in combined-cycle power stations or the like, in order to achieve favorable exhaust-gas values (“low NOx”), the procedure of spraying water into the associated combustion chamber together with the fuel (e.g. naphtha) is being increasingly adopted in order to reduce the temperature in the combustion chamber and thus prevent or make more difficult the formation of the undesirable nitrogen oxides. In large gas turbines, as manufactured, for example, by the applicant (e.g. of the type GT 13E2), a large, annular combustion chamber, in which a multiplicity of burners which can be activated individually are arranged (in an annular manner), is usually used for the combustion. Provided in this case for supplying the burners with the fuel and the water are burner lances which are each interchangeable and in whose interior space fuel and water and, if need be, also a pilot gas are fed in from outside to the burners. Here, fuel and water may be carried in separate lines and sprayed in separately, or may already be mixed at the entry to the lance to form an emulsion, which is then transmitted in a common line (in this respect see DE-A1-44 01 097 of the applicant).
In all cases, the burner lances are connected in each case at the entry side via separate feed-line valves to a fuel feed line and a water feed line, which are directed past the lance entries (lance heads) in an annular manner in order to supply all the lances. The feed-line valves permit the starting and shutdown of individual burners and at the same time control the mixture ratio of fuel to water. A further valve which connects the two feed lines to one another permits flushing of the fuel feed line by means of water from the water feed line. In addition, a venting valve is provided on the fuel ring main, and air (or water) located in the system can escape through this venting valve when the ring main is being filled with fuel.
Such a fuel distribution system accordingly has a number of valves which amount to a multiple of the number of burners or lances. Since each of these valves contains movable parts, in particular the susceptibility to faults and the maintenance costs, in addition to the plant costs, increase with the number of valves. In addition, individual activation of the valves requires complicated wiring and control logic.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to develop an improved arrangement of the type mentioned above in such a way that the disadvantages of the previous arrangement are avoided and in particular increased reliability and simplified control are obtained.
The object is achieved by an arrangement of the type mentioned above in that the valve means comprise a combination valve, which can be shifted into at least five different valve positions, in which case only the fuel feed line is connected to the combustion-chamber feed line in the first valve position, only the water feed line is connected to the combustion-chamber feed line in the second valve position, the fuel feed line and the water feed line are connected simultaneously to the combustion-chamber feed line in the third valve position, the fuel feed line and the water feed line are connected to one another and are separated from the combustion-chamber feed line in the fourth valve position, and the fuel feed line and the water feed line are shut off individually in the fifth valve position. The essence of the invention consists in performing all the necessary valve functions with a single combination valve which can be shifted into different valve positions. Such a combination valve can be realized with only one movable part, so that a greatly reduced number of movable parts and thus considerably reduced susceptibility to faults results where there is a multiplicity of burners or burner lances.
In the arrangement according to the invention, the fuel feed line and the water feed line are connected simultaneously to the combustion-chamber feed line in the third valve position, so that fuel and water are directed to the combustion chamber. If the third valve position is fixed, a mixture ratio of fuel to water appears and this mixture ratio can be varied by a further valve being fitted into at least one of the feed lines. In a first preferred embodiment of the invention, in order to avoid the use of a further valve and to fully maintain the advantages achievable with the invention, the mixture ratio between water and fuel can be set within the third valve position by varying the valve position. The mixture ratio of fuel and water can thus also be set with the same combination valve.
A second preferred embodiment of the arrangement according to the invention is distinguished by the fact that a sixth valve position, in which the water feed line is shut off and the fuel feed line is simultaneously connected to a vent outlet, is provided. In this way, it is possible, without additional movable parts or valves, to vent the fuel feed line and fill it with fuel before the actual start of operation.
A further preferred embodiment of the invention is distinguished by the fact that the combination valve is designed as a rotary valve, and each of the valve positions corresponds to a predetermined rotary angle of the rotary valve, that the combination valve comprises a valve piston arranged so as to rotate about the longitudinal axis in a valve bore, that recesses or milled-out portions, which each form a valve chamber rotatable about the axis of rotation, are arranged one behind the other in the valve piston in the axis of rotation, and that the combustion-chamber feed line, the fuel feed line and the water feed line are connected to the valve bore in each case at the level of one of the valve chambers. The only movable part of the rotary valve is the rotary piston. The specific configuration of the rotary piston results in a very simple construction of the valve and high functional reliability.
It is especially favorable if, in a preferred development of this embodiment, the valve piston has two recesses or milled-out portions, which each form a valve chamber having a semicircular cross section, if the two valve chambers are arranged rotated through 180° relative to the axis of rotation, if the fuel feed line and the water feed line lead parallel to one another and one behind the other in the direction of the axis of rotation into the valve bore, the fuel feed line leading into the first valve chamber at a suitable rotary position of the valve piston, and the water feed line leading into the second valve chamber at a suitable rotary position of the valve piston, if a first combustion-chamber outlet branches off from the valve bore transversely to the fuel feed line in the region of the first valve chamber, if a second combustion-chamber outlet branches off from the valve bore in the opposite direction to the first combustion-chamber outlet in the region of the second valve chamber, if the two combustion-chamber outlets are connected to the combustion-chamber feed line, and if a further outlet branches off from the valve bore in the opposite direction to the second combustion-chamber outlet in the region of the second combustion chamber and is connected to a branch of the fuel feed line via a connecting line.
In principle, different drives may be used for the actuation of the rotary valve; the individual rotary positions or valve positions may then be defined by appropriate catch mechanisms. However, it is especially simple and advantageous if, in another preferred embodiment, a stepping motor is provided in order to actuate the combination valve or rotary valve, by means of which stepping motor the valve can be rotated and certain predetermined rotary positions can be reliably activated at the same time.
It is especially space-
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Rodriguez William H
Thorpe Timothy S.
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