Power plants – Combustion products used as motive fluid – Combustion products generator
Patent
1995-05-09
1997-04-01
Casaregola, Louis J.
Power plants
Combustion products used as motive fluid
Combustion products generator
60737, 60748, F02C 100
Patent
active
056155557
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This application is a 371 of PCT/GB94/02219 filed Oct. 12, 1994.
This invention relates to gas turbine engines which operate on gas and at least one alternative fuel. A typical application is to a dual fuel gas turbine operating on gas as the primary or main fuel and liquid as the secondary or stand-by fuel.
During the operation of a dual fuel gas turbine on the stand-by fuel, liquid for example, the gas fuel injector passages are open to the hot combustion products of the primary zone. Hence re-circulation of the hot gases within the gas injector passages is inevitable. This problem is exaggerated if the gas passages in question are designed for low calorific value (LBTU) gas fuel and are therefore larger than those designed for natural gas operation.
The ingestion of combustion products may cause damage or blockage of the gas passages. Previous work addressed this problem by purging the gas passages when operating on the stand-by fuel by the use of external pressurised steam or other gases. This method although effective, necessitates the addition of expensive equipment to generate and or supply the purge medium therefore increasing both capital and operating costs.
While the use of compressor air for this purging process has been proposed previously, difficulties involving fuel spilling back (i.e. upstream of the injector nozzle) and flashback have not previously been overcome.
SUMMARY OF THE INVENTION
An object of the present invention is to alleviate the above difficulties while benefitting the control of smoke emissions.
According to the present invention, a fuel injector for a combustor of a turbine engine operable on either or both of primary and secondary fluid fuels, in which primary fuel orifices are exposed to combustion products during operation on the secondary fuel, comprises secondary fuel orifices connected to a secondary fuel supply passage, a ring of primary fuel orifices connected to an annular primary fuel manifold, and an annular air passage providing combustion air for fuel injected by the primary and secondary fuel orifices, the air passage being formed between a wall of the manifold and a shroud member and having an inlet for combustion air between an inlet end of the shroud member and the wall of the manifold, the injector further comprising a multiplicity of holes in the manifold wall between the air passage and the manifold, the holes and the air passage dimensions being such that the primary orifices are purged by the emission of air during operation on secondary fuel and, during operation on primary fuel, at low fuel pressure air bleeds through the holes and at high fuel pressure primary fuel bleeds through the holes to provide in both cases a pre-mix of primary fuel and air.
The primary fuel manifold may comprise an intermediate wall dividing the downstream end of the manifold into concentric annular regions, the primary fuel orifices opening into the inner one of these regions and the outer one of these regions comprising turbulence inducing means.
The air passage may be open to a combustion region downstream of the injector by way of turbulence inducing means.
The fuel injector may comprise a cylindrical fuel orifice head with a planar downstream face having an array of secondary fuel orifices surrounded by a ring of primary fuel orifices the secondary fuel orifices having access to an axial secondary fuel duct and the primary fuel orifices having access to an annular primary fuel passage, the shroud member comprising a substantially cylindrical portion and an annular portion having an aperture providing access to a combustion region downstream of the injector, the annular portion being spaced from the downstream face to provide a path for purging air in operation on secondary fuel and for pre-mix combustion air in operation on primary fuel .
BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of fuel injector in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which:
FIG.
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Casaregola Louis J.
European Gas Turbines Limited
Kim Ted
LandOfFree
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