Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-04-15
2001-06-26
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039094, C060S039530, C060S039580, C060S039590, C060S039181
Reexamination Certificate
active
06250065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a gas turbine combustion system and a combustor ignition method therefor and more specifically to a gas turbine combustion system including a liquid fuel purge device and an ignition plug unit, a combustion ignition method therefor and a diffusion combustion type gas turbine combustion system.
2. Description of the Prior Art
As a prior art, there is used a combustor made such that a pilot nozzle is provided in a central portion of an inner cylinder of which end portion is open toward a gas turbine combustion chamber, a plurality of main nozzles are provided along a circumference surrounding the pilot nozzle and fuel supply rate to the plurality of main nozzles is regulated corresponding to change in the load of gas turbine so that the combustor is operated corresponding to size of load. It is to be noted that the term “fuel nozzle” as used herein is defined to include the main nozzles and the pilot nozzle.
For example, in the combustor of gas turbine used for power generation, fuel supply rate to the main nozzles is reduced or all the fuel nozzles including the pilot nozzle are extinguished to be stopped in the night time or the like time when the power demand is small. Also, in the day time or the like time when the power demand is large, diffusion flames are first generated by the pilot nozzle and then the main nozzles which had been extinguished and stopped are restarted to form active premixed flames. For this purpose, the main nozzles are regulated of the fuel supply rate so as to correspond to the size of load and are ignited for operation by the diffusion flames held in a flame holding cone provided in front of the pilot nozzle, so that the combustor is operated corresponding to the load.
Further, there is also used such one of the mentioned combustor as having same one fuel supply system constructed such that a liquid fuel and a gas fuel, both being usable therein, are supplied into the fuel nozzles according to the time by changing over the fuel, for example, from liquid fuel to gas fuel, during the operation.
FIG. 5
is a schematic view showing a combustor and a fuel system therefor in the prior art used for operation of a gas turbine. In this figure, a combustor
01
comprises; an inner cylinder
02
provided to a side wall of a combustion chamber
013
and having its front portion opening toward the combustion chamber
013
; a fuel nozzle
05
consisting of a pilot nozzle
04
provided in a central portion within the inner cylinder
02
and a plurality of main nozzles
03
provided on a coaxial circumference surrounding the pilot nozzle
04
; and a flame holding cone
012
provided in front of the pilot nozzle
04
for holding combustion of diffusion flames generated by the pilot nozzle
04
.
Also, a liquid fuel system
08
comprises a main liquid fuel system
07
for supplying liquid fuel to the plurality of main nozzles
03
and a pilot liquid fuel system
06
for supplying the liquid fuel to the pilot nozzle
04
.
Further, if the combustor
01
is made in a dual fuel type, that is, if the fuel nozzle
05
is so made that either liquid fuel or gas fuel is usable, the liquid fuel system
08
comprising the pilot liquid fuel system
06
and the main liquid fuel system
07
can supply not only the liquid fuel but also the gas fuel to the fuel nozzle
05
when the gas fuel is to be burned by the fuel nozzle
05
. Also, in each of the liquid fuel system
08
, that is, in each of the pilot liquid fuel system
06
and the main liquid fuel system
07
, there is interposed a stop valve
09
for intercepting fuel supply to the fuel nozzle
05
. It is to be noted that the term “fuel system” as used herein is defined to include the liquid fuel system and the fuel nozzle.
To each of the liquid fuel system
08
between the stop valve
09
and the fuel nozzle
05
, there is connected an air purge system
010
having a stop valve
011
interposed therein, so that a fuel purge device is constituted thereby.
In this fuel purge device comprising the air purge system
010
and the stop valve
011
, in case the combustor
01
is a dual fuel type combustor
01
for example, when gas turbine is to be stopped after liquid fuel has been used therefor, or when liquid fuel is to be changed to gas fuel while operation is being done using the liquid fuel, the stop valve
011
is opened and compressed air is thereupon supplied from the air purge system
010
into each of the liquid fuel system
08
between the stop valve
09
and the fuel nozzle
05
so that the liquid fuel remaining in said portion of the liquid fuel system
08
and in the fuel nozzle
05
is air-purged and is discharged into the combustion chamber
013
.
However, in the prior art fuel purge device so supplying the compressed air to effect the air purge of the fuel remaining in the fuel system including the liquid fuel system
08
and the fuel nozzle
05
, when the compressed air is injected into the fuel system, the liquid fuel remaining therein is discharged from the fuel nozzle
05
into the combustion chamber
013
suddenly by the effect of the compressed air so that there is a possibility of causing a sudden change of load.
Also, because of the purging using air which is lighter than the liquid fuel, there may be such a case where the remaining liquid fuel is not completely discharged but remains in the fuel system so that coking of the liquid fuel occurs due to high temperature of the surrounding area, which results in a problem of high possibility of causing a blockage of fuel passages in the fuel system including the liquid fuel system
08
and the fuel nozzle
05
.
In
FIG. 6
, there is provided an ignition plug unit in the downstream area of said fuel nozzle
05
. In this figure, an ignition plug
6
has a piston
8
provided to its back side portion and is constructed to be protrusile and retractile into and from within a combustor wall
1
by effect of air pressure acting on the piston
8
and elastic force of an elastic spring
7
resisting thereagainst so that it is protruded into within the combustor wall
1
only when the ignition is to be done, as shown by position B in FIG.
6
.
On the other hand, a combustor in the upstream area of the position B within the combustor wall
1
is constructed such that fuel is supplied thereinto from a pilot nozzle
4
provided on a central axis of the combustor and from main nozzles
2
provided around the pilot nozzle
4
and air as combustion supporting gas is supplied through a pilot swirler
5
and main swirlers
3
provided around said respective nozzles so that the fuel and the air may be mixed and atomized.
In the combustor and the ignition plug unit so constructed, pressurized air from an air source
10
passes through a three way valve
9
and pushes the piston
8
provided to the back side of the ignition plug
6
against the elastic spring
7
, thereby the ignition plug
6
is protruded through the combustor wall
1
to the position B from position A. On the other hand, the fuel and the air from the pilot nozzle
4
and the pilot swirler
5
, respectively, are pilot-atomized and ignited by ignition spark from tip end of the ignition plug
6
. Upon the ignition being so done, the air which had been supplied to the piston
8
via the three way valve
9
is drawn by the three way valve
9
being changed over and the ignition plug
6
is retracted quickly to the original position A from within the combustor wall
1
by the elastic force of the spring
7
. Such protrusion and retraction of the ignition plug
6
are done instantaneously and the ignition spark is given only when the ignition plug
6
is in the position B.
If the combustor is of a dual fuel type in which both of gas and oil fuels are usable, there is a case where the position of the ignition plug tip which is optimal for the ignition is different between the gas fuel and the oil fuel. In this case, if the prior art ignition plug shown in
FIG. 6
is used, there arises a problem where either one of these fuel
Akamatsu Shinji
Fukue Ichiro
Gora Tetsuo
Haruta Hideki
Mandai Shigemi
Hayes Ed
Mitsubishi Heavy Industries Ltd.
Thorpe Timothy S.
Wenderoth , Lind & Ponack, L.L.P.
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