Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1999-12-23
2001-08-14
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S039170
Reexamination Certificate
active
06272864
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to gas turbines; and more particularly relates to a combustor for a gas turbine, in which combustor fuel is mixed with an air stream entering the combustor and is then burned, and the resulting combustion air stream is fed downstream from the combustor to a turbine.
BACKGROUND OF THE INTENTION
Today, gas turbines are often constructed so that the air stream guided through them is passed through two combustors and accordingly is guided twice through turbines. The drawn-in air is hereby passed first through a compressor group, and then into a primary combustor where supplied fuel/air mixture is ignited and burned. The hot combustion air then flows from the primary combustor through a first turbine, and is fed downstream from the first turbine into a secondary combustor where fuel and, if necessary, more auxiliary air, is mixed in and ignites the mixture. Since the gases flowing out of the first turbine are frequently very hot, i.e., are above the self-ignition temperature of the fuels, an active ignition in the secondary combustor is in most cases not necessary. Downstream from the secondary combustor is a second turbine, through which the hot combustion gases from the secondary combustor flow.
For space reasons and for technical simplification, the individual components in such gas turbines are provided mostly in series along a main axis of the gas turbine. Such a gas turbo group is known, for example, from U.S. Pat. No. 5,577,378. The individual channels for the air streams and combustors all are hereby designed in most cases essentially in the form of hollow cylinders extending around the axis of the gas turbine.
Secondary combustors for such gas turbines are, as a rule, designed in a relatively simple manner since they do not need burners, but the fuel can be simply injected into the air stream via nozzles following a suitable swirling of the hot air exiting the first turbine, and the mixture self-ignites after a characteristic time. A simple, hollow-cylindrically designed secondary combustor is known, for example, from U.S. Pat. No. 5,497,611.
Because of the high mach values in secondary combustors that are necessary, for example, among other things, because of the short self-ignition times especially of gaseous fuels, thermoacoustic oscillations with high amplitudes frequently occur in the secondary combustors. In addition, there is the problem of a quick and effective mixing of air and fuel in the combustion chamber while at the same time preventing a backflow. In most cases, specific swirl-generating elements are provided for this purpose. In addition, it must be ensured during the mixing and during the combustion control, especially in more recent times, that the emission values remain within the legally permissible limits.
SUMMARY OF THE INVENTION
It is therefore the objective of the invention to create a combustor for gas turbines that prevents the disadvantages of the known solutions and is characterized in particular by a good and efficient mixing of fuel and the added air.
In a combustor of the initially mentioned type, this objective is realized in that the combustor has an annular diffuser into which enters the air stream; that downstream from the diffuser, and communicating with it, at least one essentially annular, toroidal chamber is provided; that downstream from the annular, toroidal chamber and distributed over its periphery mixing pipes branch off, and that downstream from the mixing pipes an annular combustion chamber is provided into which merge the mixing pipes. The core of the invention is that the combination of diffuser, annular toroidal chamber and mixing pipes provide a premixing structure in which the air flowing through can be mixed optimally, i.e., quickly and efficiently, with fuel. Another advantage is that with the suggested configuration there is less of a tendency of thermoacoustic oscillations.
A first preferred embodiment of the combustor according to the invention is characterized in that the combustor is designed as a secondary combustor, and that the gas turbine has a primary combustor, a first turbine acting downstream from the primary combustor, a secondary combustor acting downstream from the first turbine, and a second turbine acting downstream from the secondary combustor. The use of the combustor as a secondary combustor is advantageous since especially this type of use at high mach values requires short mixing times. The quick and backflow-free mixing in the suggested arrangement is advantageous especially if the ignition, as described in another embodiment, takes place in the secondary combustor by self-ignition, and this makes it possible to ensure a controlled combustion in the area of the outlet of the mixing pipes into the combustor or inside the combustor.
Another preferred embodiment of the combustor according to the invention is characterized in that the diffuser is designed in such a way that the air stream flowing parallel to the gas turbine axis and entering the combustor is first deflected essentially in radial direction, and that the diffuser acts on the annular toroidal chamber tangentially so that the air stream entering the annular toroidal chamber coils in a torus and swirls around the annular secondary torus axis. If now, in addition, the mixing pipes are preferably provided on the side essentially opposing the diffuser in a manner essentially parallel to the axis of the gas turbine, two swirls with different rotating direction will then collide with each other before the mixing pipes and will then flow through the mixing pipes while mixing with each other and destroying the swirls. This makes it possible, as described in another embodiment, to provide means in or in front of the area of this mixing of the counter-rotating swirls which can be used to inject fuel into the air stream. This makes it possible to keep the mixing process short and adjust the ignition front to the desired location.
REFERENCES:
patent: 3877219 (1975-04-01), Hagen
patent: 4073137 (1978-02-01), Roberts
patent: 4081957 (1978-04-01), Cox, Jr.
patent: 4838029 (1989-06-01), Gleason et al.
patent: 5497611 (1996-03-01), Benz et al.
patent: 5575153 (1996-11-01), Ito et al.
patent: 5577378 (1996-11-01), Althaus et al.
patent: 6192669 (2001-02-01), Keller et al.
patent: 679 799 (1992-04-01), None
patent: 39 42 042 (1991-06-01), None
patent: 42 36 071 (1994-04-01), None
patent: 669 500 (1995-08-01), None
patent: 2 098 719 (1982-11-01), None
patent: 62-158927 (1987-07-01), None
Keller Jakob J.
Keller-Schärli Maria A.
ABB Alstom Power ( Schweiz) AG
Burns Doane Swecker & Mathis L.L.P.
Keller-Schärli Maria A.
Terrente David J.
Thorpe Timothy S.
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