Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – Fluid streams have angular junction
Reexamination Certificate
1998-12-08
2001-02-20
Koczo, Michael (Department: 3748)
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
Fluid streams have angular junction
C060S737000
Reexamination Certificate
active
06189814
ABSTRACT:
The present invention relates to a gas turbine engine combustion chamber.
BACKGROUND OF THE INVENTION
In order to meet the emission level requirements, for industrial low emission gas turbine engines, staged combustion is required in order to minimise the quantity of the oxides of nitrogen (NOx) produced. Currently the emission level requirement is for less than 25 volumetric parts per million of NOx for an industrial gas turbine exhaust. The fundamental way to reduce emissions of nitrogen oxides is to reduce the combustion reaction temperature and this requires premixing of the fuel and all the combustion air before combustion takes place. The oxides of nitrogen (NOx) are commonly reduced by a method which uses two stages of fuel injection. Our UK patent no 1489339 discloses two stages of fuel injection to reduce NOx. Our International patent application no WO92/07221 discloses two and three stages of fuel injection. In staged combustion, all the stages of combustion seek to provide lean combustion and hence the low combustion temperatures required to minimise NOx. The term lean combustion means combustion of fuel in air where the fuel to air ratio is low, ie less than the stoichiometric ratio.
The present invention is particularly concerned with gas turbine engines which have staged combustion, and more particularly concerned with the secondary fuel and air mixing duct and secondary fuel injection or tertiary fuel and air mixing duct and tertiary fuel injection.
In order to inject fuel into the secondary, or tertiary fuel and air mixing ducts, it is known to use cylindrical fuel injectors which extend across the inlet to the mixing duct as described in our copending UK patent application 9310690.4 filed May 24, 1993. This arrangement has suffered from preburning of fuel in the air in the mixing duct whereas the fuel should not burn until it is in the appropriate combustion zone. The fuel burns in the air in the mixing duct because of recirculation of the fuel and air in regions immediately downstream of the fuel injectors and due to hot gases in the combustion zone flowing upstream into the mixing duct.
SUMMARY OF THE INVENTION
The present invention seeks to provide a combustion chamber which reduces or overcomes these problems.
Accordingly the present invention provides a gas turbine combustion chamber comprising at least one combustion zone defined by at least one peripheral wall,
means to define at least one fuel and air mixing duct for conducting a mixture of fuel and air to the at least one combustion zone, each mixing duct having an upstream end for receiving air, an intermediate region for receiving fuel and a downstream end for delivering a fuel and air mixture into the at least one combustion zone, each mixing duct reducing in cross-sectional area from its upstream end to its downstream end to produce an accelerating flow therethrough,
at least one fuel injector for injecting fuel into the intermediate region of the at least one mixing duct, each fuel injector extending in a downstream direction along the at least one mixing duct to the intermediate region, each fuel injector being effective to subdivide the at least one mixing duct into a plurality of ducts over at least a part of the streamwise length of the at least one mixing duct, each fuel injector having a plurality of discharge apertures positioned to inject fuel into the intermediate region of the at least one mixing duct, said discharge apertures injecting fuel transversely of the streamwise direction.
The fuel injector may extend the full length of the at least one mixing duct, to subdivide the at least one mixing duct into a plurality of ducts over the full streamwise length of the at least one mixing duct.
At least one wall may extend in a downstream direction along the at least one mixing duct, each wall being effective to subdivide the at least one mixing duct into a plurality of ducts over at least a part of the streamwise length of the at least one mixing duct.
The at least one fuel injector may extend over an upstream portion of the mixing duct, the wall extends over a downstream portion of the mixing duct, the downstream end of the fuel injector being positioned substantially immediately upstream of the upstream end of the wall such that the fuel injector and the wall cooperate to subdivide the at least one mixing duct into a plurality of ducts over the full streamwise length of the at least one mixing duct.
The at least one fuel injector may extend over an upstream portion of the mixing duct, the fuel injector reducing in cross-sectional area from its upstream end to its downstream end.
The downstream end of the fuel injector preferably has a relatively sharp edge.
Preferably the portion of the fuel injector positioned within the mixing duct has a race track cross-section.
Preferably the fuel injector extends through the upstream end of the mixing duct, a portion of the fuel injector is positioned outside the mixing duct.
Preferably the portion of the fuel injector outside the mixing duct has an aerofoil cross-section.
Preferably the fuel injector extends in a first direction transversely relative to the streamwise direction across a major portion of the at least one mixing duct.
Preferably the fuel injector has at least a portion of substantially constant dimension in the first direction, the portion is arranged between the upstream end and the intermediate region of the mixing duct.
Preferably the portion of the fuel injector positioned outside the mixing duct reduces in cross-sectional area towards the portion of the fuel injector positioned within the mixing duct.
Preferably the fuel injector reduces in dimension in a second direction transversely relative to the streamwise direction, between the upstream end and the intermediate region of the mixing duct, the second direction is perpendicular to the first direction.
Preferably there is a uniform reduction in dimension in the second direction.
Preferably a plurality of fuel injectors are provided.
The combustion chamber may have a primary combustion zone and a secondary combustion zone downstream of the primary combustion zone, the at least one fuel and air mixing duct delivers the fuel and air mixture into the secondary combustion zone.
The peripheral wall may be annular, the at least one fuel and air mixing duct is arranged around the primary combustion zone.
The combustion chamber may have a primary combustion zone, a secondary combustion zone downstream of the primary combustion zone and a tertiary combustion zone downstream of the secondary combustion zone, the at least one fuel and air mixing duct delivers the fuel and air mixture into the tertiary combustion zone.
The peripheral wall may be annular, the at least one fuel and air mixing duct is arranged around the secondary combustion zone.
The at least one fuel and air mixing duct may be defined at its radially inner extremity and radially outer extremity by a pair of annular walls.
Preferably a plurality of equi-circumferentially spaced fuel injectors are provided.
Preferably the combustion chamber is surrounded by a combustion chamber casing, a fuel manifold to supply fuel to the at least one fuel injector.
The present invention also provides a gas turbine combustion chamber comprising at least one combustion zone defined by at least one peripheral wall,
mixing duct means for conducting a mixture of fuel and air to the at least one combustion zone, the mixing duct means having an upstream end for receiving air, an intermediate region for receiving fuel and a downstream end for delivering a fuel and air mixture into the at least one combustion zone, the mixing duct means reducing in cross-sectional area from its upstream end to its downstream end to produce an accelerating flow therethrough,
a plurality of fuel injectors for injecting fuel into the intermediate region of the mixing duct means, the fuel injectors extending in a downstream direction along the mixing duct means to the intermediate region, the fuel injectors being effective to subdivide the mixing duct means into a plura
Farkas & Manelli PLLC
Koczo Michael
Rolls-Royce plc
Taltavull W. Warren
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