Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Reexamination Certificate
1999-08-30
2001-02-20
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
C060S737000, C060S743000, C060S746000
Reexamination Certificate
active
06189314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combustor for a gas turbine engine, utilizing a combination of a diffusion combustion system and a premixing/pre-evaporating combustion system, or a combustor for a gas turbine engine, including a premixing/pre-evaporating chamber.
2. Description of the Related Art
Combustors for a gas turbine engine are already known from U.S. Pat. No. 4,589,260 and Japanese Patent Application Laid-open No. 7-332671. A first fuel nozzle for diffusion combustion disposed on the axis of the gas turbine engine combustor of the latter publication, is designed to inject fuel under pressure directly into a combustion chamber. A second fuel nozzle for premixing/pre-evaporating combustion disposed to surround an outer periphery of the first fuel nozzle, includes a louver disposed within an annular premixing/pre-evaporating chamber in which a swirled air flow generated by a swirler flows; and is designed to atomize the fuel injected from a fuel injecting port into the premixing/pre-evaporating chamber by collision of the fuel against the louver.
The combustor for the gas turbine engine of the above-described Japanese publication suffers from a problem that it is difficult to sufficiently atomize fuel, resulting in a degraded emission characteristic, because the first fuel nozzle injects the fuel under pressure directly into the combustion chamber. The combustor also suffers from another problem that it is difficult to appropriately design the shape of the louver and the relative positional relationship between the louver and the fuel injection port, because the fuel injected from the fuel injection port by the second fuel nozzle must be atomized by collision against the louver, and also the number of parts is increased due to the provision of the louver.
The combustor for the gas turbine engine of the above-described Japanese publication includes an annular premixing/pre-evaporating chamber surrounding the axis, and a homogeneous combustion chamber connected to a downstream portion of the premixing/pre-evaporating chamber, so that the air and fuel fed to the premixing/pre-evaporating chamber are supplied to the homogeneous combustion chamber in a state in which the air and fuel are atomized by generating swirled flows thereof.
In the combustor for the gas turbine engine where the premixing/pre-evaporating chamber is at a location upstream of the homogeneous combustion chamber, the following problem is encountered: A fuel-air mixture in the premixing/pre-evaporating chamber may be self-ignited by a back fire from the homogeneous combustion chamber in some cases. Particularly, in the center portion of the premixing/pre-evaporating chamber, the swirled flows stagnate, resulting in a reduced flow speed and for this reason, the self-ignition phenomenon is liable to be produced.
SUMMARY OF THE INVENTION
Accordingly, it is a first object of the present invention to ensure that the atomization of the fuel is promoted to enhance the emission characteristic in the combustion for the gas turbine engine utilizing the combination of the diffusion combustion system and the premixing/pre-evaporating combustion system.
It is a second object of the present invention to ensure that the self-ignition phenomenon due to the stagnation of the swirled flows in the premixing/pre-evaporating chamber is prevented in the combustor for the gas turbine engine including the premixing/pre-evaporating chamber.
To achieve the above first object, according to a first aspect and feature of the present invention, there is provided a combustor for a gas turbine engine, comprising a single can type homogeneous combustion chamber disposed on an axis of an engine casing, a first fuel nozzle disposed on the axis for supplying a fuel-air mixture to an upstream end of the homogeneous combustion chamber, and a premixing/pre-evaporating chamber surrounding an outer periphery of the first fuel nozzle and connected to the upstream end of the homogeneous combustion chamber, and a second fuel nozzle surrounding the outer periphery of the first fuel nozzle for supplying the fuel-air mixture to the upstream end of the premixing/pre-evaporating chamber. The first fuel nozzle is an air blast nozzle which includes a first fuel liquid film forming passage disposed on the axis for supplying the fuel, and a first annular air passage surrounding an outer periphery of the first fuel liquid film forming passage for supplying air. The second fuel nozzle is an air blast nozzle which includes a second annular fuel liquid film forming passage surrounding the outer periphery of the axis for supplying the fuel, and a second annular air passage surrounding an outer periphery of the second fuel liquid film forming passage for supplying air.
With the above arrangement, the homogeneous combustion chamber, the premixing/pre-evaporating chamber, the first fuel nozzle and the second fuel nozzle are disposed axially symmetrically with respect to the axis of the engine casing. Therefore, the flow of the air, the fuel, the fuel-air mixture and a combustion gas are axially symmetrical and circumferentially uniform. Thus, the pressure loss can be decreased to provide an increase in power output and a reduction in fuel consumption. Also the fuel-air ratio of the fuel-air mixture supplied to the homogeneous combustion chamber is circumferentially uniform to enhance the emission characteristic and moreover, the profile of temperature in the combustor is axially symmetrical, whereby the thermal strain of various parts is suppressed to a minimum.
In addition, since the first fuel nozzle for diffusion combustion having excellent igniting performance and flame stabilizing performance and the second fuel nozzle for premixing/pre-evaporating combustion having an excellent emission characteristic, are used in combination, the igniting performance and flame stabilizing performance and the emission characteristic can all be reconciled.
Further, the first fuel nozzle for diffusion combustion for supplying the fuel-air mixture directly to the homogeneous combustion chamber comprises an air blast nozzle which includes a first fuel liquid film forming passage disposed on the axis for supplying the fuel, and a first annular air passage disposed to surround the outer periphery of the first fuel liquid film forming passage for supplying air. Therefore, the fuel can be atomized sufficiently by the first fuel nozzle to contribute to an enhancement in the emission characteristic. Additionally, the second fuel nozzle for premixing/pre-evaporating combustion for supplying the fuel-air mixture to the homogeneous combustion chamber through the premixing/pre-evaporating chamber comprises an air blast nozzle which includes a second annular fuel liquid film forming passage disposed to surround the outer periphery of the axis for supplying the fuel and a second annular air passage being disposed to surround the outer periphery of the second fuel liquid film forming passage for supplying air. Therefore, the cooperation of the atomization of the fuel by the first fuel nozzle and the premixing/pre-evaporating effect for the fuel-air mixture provided by the premixing/pre-evaporating chamber can contribute to a further enhancement of the emission characteristic.
To achieve the above first object, according to a second aspect and feature of the present invention, a ignition plug is disposed in the vicinity of the nozzle tip of the first fuel nozzle.
With the above arrangement, the ignition plug is disposed in the vicinity of the nozzle tip of the first fuel nozzle for supplying the fuel at the start of the gas turbine engine. Therefore, the fuel-air mixture supplied from the nozzle tip of the first fuel nozzle at the start can be ignited reliably by the ignition plug.
To achieve the first object, according to a third aspect and feature of the present invention, a swirling is provided to the air and the fuel supplied to the first fuel liquid film forming passage.
With the above arrangement, prior swirling is provided to the a
Kobayashi Nobuyuki
Nakata Hidehiko
Utsugi Eiichi
Yamamoto Yoshiharu
Arent Fox Kintner & Plotkin & Kahn, PLLC
Casaregola Louis J.
Honda Giken Kogyo Kabushiki Kaisha
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