Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1999-02-04
2001-04-03
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
Reexamination Certificate
active
06209326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas turbine combustor.
2. Related Art
Gas turbine combustors of the prior art will be described with reference to
FIGS. 5 and 6
.
In a gas turbine combustor of the prior art, as shown in
FIGS. 5 and 6
, there is arranged at the center of the section of the combustor a pilot fuel nozzle
104
for producing a flame portion. Around this pilot fuel nozzle
104
, there is a cylindrical outer cylinder
106
, on which there are arranged a plurality of main fuel nozzles
102
for producing a premixed gas of a fuel and air.
The pilot fuel nozzle
104
is provided with a pilot swirler
103
. Each of the main fuel nozzles
102
is provided with main swirlers
101
which are arranged around the main fuel nozzle
102
and extend to the outer cylinder
106
. A plurality of nozzle ports
105
are opened in the nozzle body wall face of the main fuel nozzle
102
downstream of the main swirlers
101
.
In the construction described above, the air and the fuel flow in the directions, as indicated by arrows in
FIGS. 5 and 6
, so that the air and the fuel are fed from a plurality of main swirlers
101
and one pilot swirler
103
, and from a plurality of main fuel nozzles
102
and one pilot fuel nozzle
104
, respectively, to the combustion zone.
The fuel thus fed from the main fuel nozzle
102
is injected from the nozzle ports
105
in the nozzle body wall face so that it is mixed with the air flowing through the main swirlers
101
around the nozzle outer circumference to prepare a premixed gas.
In the combustor of the prior art, the main fuel nozzle
102
, the main swirlers
101
and the outer cylinder
106
construct a main fuel nozzle device.
The main fuel nozzle device of the gas turbine combustor of the prior is of the type in which the fuel is injected from the nozzle ports formed in the wall face of the nozzle body, as described hereinbefore.
This system has a problem in that the premixture to be prepared in the vicinity of the exits of the main swirlers has a tendency to become a gas having a higher fuel concentration at its center portion. Another problem is that the pressure for feeding the fuel has to be set at a high level for establishing a fuel penetration necessary for mixing the fuel, injected from the main fuel nozzles, efficiently with the air flow.
Another example of the gas turbine combustor of the prior art is shown in FIG.
7
.
In a gas turbine combustor
201
of the prior art, as shown in
FIG. 7
, there is formed a combustion chamber
212
which is enclosed and defined by both an axially symmetrical cylindrical upstream inner cylinder
206
and a downstream inner cylinder
207
connected at its leading end portion to the rear end portion of the upstream inner cylinder
206
.
The downstream inner cylinder
207
forming the combustion chamber
212
together with the upstream inner cylinder
206
is composed of a plurality of cylinders, with these cylinders increasing in diameters from the inner cylinder
206
to a downstream-most cylinder. A clearance is formed at the joint between adjacent inner cylinders
207
so that compressed air flowing outside of the upstream inner cylinder
206
and the downstream inner cylinder
207
may flow as cooling air
217
through this clearance into the downstream inner cylinder
207
, and then may flow further along the inner circumference of the downstream inner cylinder
207
to cool the downstream inner cylinder
207
from its inside to then protect it from the combustion gas which is at a high temperature and under a high pressure. Air as indicated by arrows
204
and
210
flows respectively through swirlers
203
and
209
.
In the gas turbine combustor
201
of the prior art, as has been described hereinbefore, a pilot nozzle
202
and a main nozzle
208
are arranged in the upstream inner cylinder
206
on the upstream side of the combustion chamber
212
. A pilot fuel
213
and a main fuel
215
, i.e. the fuels necessary for the operation of the gas turbine, are fed to the upstream side of the combustion chamber
212
. As a result, the ratio of the unburned fuel to the fed fuel has a high value on the upstream side but gradually lowers toward the downstream side, as plotted in the distribution of the unburned fuel in the axial direction of the combustor in FIG.
8
.
Specifically, the ratio of the fuel being burned in a section in the combustion chamber
212
, i.e., the so-called “sectional load factor” is high on the upstream side, but a certain unburned fuel ratio is maintained even within a range on the downstream side so that the sectional load factor is shared. As a result, the combustion in the combustion chamber
212
can maintain a stable combustion and a low NOx emission.
Gas turbines have been demanded in recent years to have a high temperature and a high pressure of the combustion gas for a larger size and a higher efficiency. However, the reaction rate of the fuel, as fed to the combustion chamber
212
, is increased by the high temperature and pressure of the combustion gas. If 100% of the fuels
213
and
215
required for running the gas turbine are fed on the upstream side, therefore, they are instantly burned on the upstream side, and the unburned gas has a small distribution on the downstream side. As a result, the sectional load factor rises on the upstream side and causes problems of an unstable combustion state and an increase in the NOx emission.
SUMMARY OF THE INVENTION
An object of the invention is to provide a gas turbine combustor which is enabled to prepare a homogeneous premixture, to thereby suppress an NOx emission by mixing a main fuel and air homogeneously without requiring a high fuel feeding pressure.
Another object of the invention is to provide a gas turbine combustor which can eliminate the disadvantage of the instability in the combustion state or the increase in the NOx emission caused when 100% of fuel is fed to the upstream side of the combustion chamber, as in the gas turbine of the prior art. When this gas turbine is demanded to have high temperature and pressure of the combustion gas for a large size and a high efficiency.
In order to solve the above-specified problems, according to the invention, there is provided a gas turbine combustor comprising: a cylindrical outer cylinder into which air is fed; main swirlers disposed in the outer cylinder; and an annular fuel feed manifold disposed on the outer circumference of the outer cylinder on the upstream or downstream side of the main swirlers, and having a plurality of nozzle ports communicating with the inside of the outer cylinder.
In the invention, the fuel is injected from the outer circumference to the center of the air flowing in the outer cylinder so that a more homogeneous premixture than that of the device of the prior art can be prepared to suppress the NOx emission.
On the other hand, it is possible to lower the high fuel feed pressure which has been demanded in the device of the prior art for the fuel to reach the outer circumference of the air flow.
In order to solve the aforementioned problem in the gas turbine combustor having the combustion chamber formed by the upstream inner cylinder and the downstream inner cylinder, according to the invention, the main fuel is divided to be fed in the direction of the flow of the burning air in the combustion chamber which is formed by the upstream inner cylinder and the downstream inner cylinder.
As a result, even in the gas turbine in which the high temperature and pressure of the combustion gas are demanded for the larger size and the higher efficiency so that the reaction rate of the fuel fed to the inside of the combustion chamber is raised by the high temperature and pressure of the combustion gas, the unburned fuel ratio of the fuel fed to the inside of the combustion chamber can obtain a distribution in which the ratio gently fluctuates in the flow direction of the burning air flowing in the combustion chamber.
That is to say, the sectional load factor can be prevented from locally risi
Haruta Hideki
Inada Mitsuru
Ishiguro Tatsuo
Mandai Shigemi
Nishida Koichi
Freay Charles G.
Gartenberg Ehud
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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