Power plants – Combustion products used as motive fluid
Reexamination Certificate
2000-05-19
2001-12-25
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039230, C060S737000, C060S746000
Reexamination Certificate
active
06332313
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a combustion chamber assembly, particularly a combustion chamber assembly for a non-aero gas turbine engine.
BACKGROUND OF THE INVENTION
A small gas turbine engine is described in UK patent application no. 9800782.6 filed Jan. 15, 1998 and in a corresponding International patent application no. PCT/GB99/00074 filed Jan. 8, 1999, now abandoned. This gas turbine engine comprises a centrifugal compressor, a diffuser, a heat exchanger, combustion apparatus, and at least one turbine. The compressor has variable inlet guide vanes, the diffuser has variable outlet guide vanes and the at least one turbine has variable inlet guide vanes so that the flow capacity of each component is independently variable while maintaining the temperature, pressure ratio and speed of rotation of the gas turbine engine substantially constant.
A combustion chamber is required for this gas turbine engine which produces low emissions of the oxides of nitrogen (NOx), carbon monoxide (CO) and unburned hydrocarbons (UHC) throughout the entire power range of the gas turbine engine, but especially at low powers.
The fundamental way to reduce the emissions of nitrogen oxides (NOx) is to reduce the combustion reaction temperature, and this requires premixing of the fuel and most of the combustion air before combustion occurs. The oxides of nitrogen (NOx) are commonly reduced by a method which uses two stages of fuel injection. Our UK patent no GB1489339 discloses two stages of fuel injection. 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, i.e. less than the stoichiometric ratio. In order to achieve the required low emissions of NOx and CO it is essential to mix the fuel and air uniformly.
The industrial gas turbine engine disclosed in our International patent application no. WO92/07221 uses a plurality of tubular combustion chambers, whose axes are arranged in generally radial directions. The inlets of the tubular combustion chambers are at their radially outer ends, and transition ducts connect the outlets of the tubular combustion chambers with a row of nozzle guide vanes to discharge the hot gases axially into the turbine sections of the gas turbine engine. Each of the tubular combustion chambers has two coaxial radial flow swirlers which supply a mixture of fuel and air into a primary combustion zone. An annular secondary fuel and air mixing duct surrounds the primary combustion zone and supplies a mixture of fuel and air into a secondary combustion zone. An annular tertiary fuel and air mixing duct surrounds the secondary combustion zone and supplies a mixture of fuel and air into a tertiary combustion zone.
SUMMARY OF THE INVENTION
Accordingly the present invention seeks to provide a novel combustion chamber assembly for a gas turbine engine which comprises variable inlet guide vanes for the compressor, variable guide vanes for the diffuser, variable inlet guide vanes on the turbine, and in which the combustion chamber assembly produces low emissions at low power levels of the gas turbine engine.
Accordingly the present invention provides a combustion chamber assembly comprising at least one combustion chamber having a primary combustion zone, a secondary combustion zone, at least one primary fuel and air mixing duct, primary fuel injector means to supply fuel to the primary fuel and air mixing duct, first valve means to control the supply of air to the at least one primary fuel and air mixing duct, the primary fuel and air mixing duct being arranged to supply fuel and air into the primary combustion zone, at least one secondary fuel and air mixing duct, secondary fuel injector means to supply fuel to the secondary fuel and air mixing duct, second valve means to control the supply of air to the secondary fuel and air mixing duct, the secondary fuel and air mixing duct being arranged to supply fuel and air into the secondary combustion zone, and means to supply cooling air and dilution air to the combustion chamber.
Preferably the primary fuel and air mixing duct is arranged to supply the fuel and air into the primary combustion zone with a downstream flow component.
Preferably the secondary fuel and air mixing duct is arranged to supply the fuel and air into the primary combustion zone with a tangential and a downstream flow component.
Preferably each primary fuel and air mixing duct comprises a pair of axial flow swirlers arranged coaxially to swirl the air in opposite directions, the primary fuel injector means being arranged to supply fuel coaxially of the axial flow swirlers in the primary fuel and air mixing duct.
Preferably each secondary fuel and air mixing duct comprises a pair of axial flow swirlers arranged coaxially to swirl the air in opposite directions, the secondary fuel injector means being arranged to supply fuel coaxially of the axial flow swirlers in the secondary fuel and air mixing duct.
Preferably the combustion chamber has a tertiary combustion zone, at least one tertiary fuel and air mixing duct, tertiary fuel injector means to supply fuel to the tertiary fuel and air mixing duct, means to supply air to the tertiary fuel and air mixing duct, the tertiary fuel and air mixing duct being arranged to supply fuel and air into the tertiary combustion zone.
Preferably the tertiary fuel and air mixing duct is arranged to supply fuel and air into the tertiary combustion zone with a tangential component opposite to the secondary fuel and air mixing duct and a downstream flow component.
Preferably each tertiary fuel and air mixing duct comprises a pair of axial flow swirlers arranged coaxially to swirl the air in opposite directions, the tertiary fuel injector means being arranged to supply fuel coaxially of the axial flow swirlers in the tertiary fuel and air mixing duct.
Preferably there a plurality of primary fuel and air mixing ducts and a plurality of secondary fuel and air mixing ducts.
Preferably there a plurality of primary fuel and air mixing ducts, a plurality of secondary fuel and air mixing ducts and a plurality of tertiary fuel and air mixing ducts.
Preferably the primary fuel and air mixing duct is arranged to inject fuel and air into the combustion chamber with a tangential and a downstream flow component.
The first and second valve means may be two position valves, alternatively the first and second valve means may be multi-position valves.
Preferably one of the axial flow swirlers in the primary fuel and air mixing duct provides more swirl than the other axial flow swirler such that there is a residual swirl provided by the pair of axial flow swirlers.
Preferably the axial flow swirlers in the secondary fuel and air mixing duct provide substantially equal and opposite swirl such that there is no residual swirl provided by the pair of axial flow swirlers.
Preferably the axial flow swirlers in the tertiary fuel and air mixing duct provide substantially equal and opposite swirl such that there is no residual swirl provided by the pair of axial flow swirlers.
Preferably there are means to measure the flow of air to the primary and secondary fuel and air mixing ducts, and means to control the supply of fuel to the primary and secondary fuel injector means in response to the measured flows of air to the primary and secondary fuel and air mixing ducts to minimise emissions from the combustion chamber.
Preferably there are means to measure the flow of air to the primary, secondary and tertiary fuel and air mixing ducts, and means to control the supply of fuel to the primary, secondary and tertiary fuel injector means in response to the measured flows of air to the primary, secondary and tertiary fuel and air mixing ducts to minimise emissions from the combustion chamber.
Preferably the means to measure the air flow to the primary, secon
Melville James
Willis Jeffrey D.
Kim Ted
Manelli Denison & Selter PLLC
Rolls-Royce plc
Taltavull W. Warren
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