Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1997-03-18
2001-04-03
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S747000, C060S760000, C060S756000, C060S748000
Reexamination Certificate
active
06209325
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a combustor for a gas- or liquid-fueled turbine.
A turbine engine typically includes an air compressor, at least one combustor and a turbine. The compressor supplies air under pressure to the combustor(s)—a proportion of the air is mixed with the fuel, while the remaining air supplied by the compressor is utilized to cool the hot surfaces of the combustor and/or the combustion gases, (i.e., the gases produced by the combustion process, and/or other components of the turbine plant).
With the aim of reducing the amount of pollutants produced by the combustion process (particularly No
x
), lean burn combustors have been proposed. Such combustors involve the premixing of air and fuel, with a relatively low proportion of fuel being utilized. Combustion then occurs at relatively low temperatures, which reduces the amount of pollutants produced. However, in their basic form such lean burn combustors have a narrow operating range, i.e. they cannot work satisfactorily with large variations in the quantity of fuel being supplied, and are susceptible to flame blow-out or flash-back.
One known solution aimed to overcome difficulties inherent in this type of combustor is to stage the air and/or fuel supply relative to engine load, for example, so that optimum flow and mixture rates are achieved over the whole operating range. Stage combustors have, in the past, taken various designs, from those of fixed geometry which may have a number of burners and to which fuel is selectively directed depending on engine requirements, to those of a more complicated nature which may have movable parts to control the flow of combustion air.
The present invention seeks to provide a three stage combustor of relatively simple construction but which is nonetheless effective in minimizing the production of pollutants resulting from the combustion process and, in addition, operates with good combustion stability and an excellent turndown ratio whilst at the same time giving flashback-free combustion.
SUMMARY OF THE INVENTION
According to the invention, there is provided a combustor for a gas- or liquid-fueled turbine comprising a main combustion chamber and a pre-chamber, a first injection means for supplying fuel or a fuel/air mixture to the pre-chamber, a second injection means for supplying air or a fuel/air mixture to the pre-chamber, a third injection means for supplying air or a fuel/air mixture to the main combustion chamber, the first, second and third injection means being operable progressively in sequence to provide fuel or a fuel/air mixture for combustion; and wherein the third injection means comprises at least one elongated passage means with an arrangement for introducing fuel into the passage means.
The combustion chamber and the pre-chamber are preferably defined by one or more cylindrical walls whereby the pre-chamber and the combustion chamber are each of cylindrical form, and with the cross-sectional area of the combustion chamber being greater than the cross-sectional area of the pre-chamber. Preferably, a transition region is defined between the pre-chamber and the combustion chamber.
The arrangement for introducing fuel into the passage means may comprise a spray bar.
Preferably at least part of the length of the passage means extends alongside the combustion chamber over at least part of the length of the combustion chamber. Further, at least part of the length of a passage for cooling air may extend alongside the combustion chamber over at least part of the length of the combustion chamber.
The elongated passage means may be of generally annular form having a radially inner wall and a radially outer wall, the radially inner wall being constituted at least partly by a wall defining the combustion chamber.
It is also envisaged that said elongated passage means and said passage for cooling air may both be of annular form with the passage for cooling air being situated radially outside the combustor chamber and the passage means being situated radially outside the passage for cooling air.
The axial direction of flow of fuel/air mixture in the elongated passage means may be counter to the axial direction of flow of cooling air in the passage therefor.
Alternatively the flow of fuel/air mixture in the elongated passage means may be in the same direction as the flow of cooling air in the passage therefor.
The passage means may include turbulence inducing means, which may comprise at least one tube extending between the walls defining the passage means. The or each tube may be open-ended and provide means for entry of cooling air from outside the combustor to the passage for cooling air.
The interior of the wall or walls defining the combustion chamber and the pre-chamber may have a thermal barrier coating applied thereto.
At least one of the walls defining the elongated passage means may be of corrugated section.
In a preferred arrangement the first injection means provides an air/fuel mixture with local fuel rich areas.
The second injection means may comprise a fuel spray bar, an air inlet means, and a chamber in which mixing of the fuel and air takes place.
When a passage for coolant air is provided it is envisaged that coolant air will pass from the passage into the interior of the combustor; at least a part of the coolant air may pass into the combustion chamber through at least one orifice adjacent the downstream region thereof, and/or at least a part of the coolant air may pass into the interior of the combustor through at least one orifice in a transition duct region.
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European Gas Turbines Limited
Kim Ted
Kirschstein et al.
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