Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Patent
1993-05-26
1994-12-06
Thorpe, Timothy S.
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
60 3955, F02C 900
Patent
active
053699513
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 continuation of PCT/GB91/02100, filed Nov. 27, 1991.
FIELD OF THE INVENTION
This invention relates to gas generators, e.g., industrial gas turbine engines for producing electrical or mechanical power. These may be used as part of a combined cycle power plant, or for providing power for process plants.
The invention is particularly relevant to gas generators which can operate on both liquid and gaseous fuels and which are provided with steam injection, primarily to reduce emissions of nitrous oxides (NOx) in their exhausts.
BACKGROUND OF THE INVENTION
It is well known to use steam injection to reduce NOx emissions from gas turbine engines and/or to boost their powers. United Kingdom patent application no. 2219070 discloses a dual fuel injector provided with a steam injector to inject steam into a gas turbine combustor when the engine is operating on liquid fuel. It should be noted that steam can also be injected when the engine is operating on gas fuel only. When the engine is operating on liquid fuel a proportion of delivery air from the compressor of the engine is allowed to flow through purge holes in the fuel injector to provide a positive flow of air through the gas nozzles in order to prevent these nozzles becoming partially or wholly blocked by carbon deposits which can accumulate when operating on liquid fuel only.
However, the steam is injected into the compressor delivery flow upstream of the fuel injector and thus it is possible for a mixture of steam and air to enter the gas fuel passages. These passages comprise a small gas fuel manifold within the fuel injector, a large outer gas fuel manifold around the engine, supply ducts from the outer gas manifold to the fuel injectors, and a gas fuel supply pipe to the outer manifold. When the engine operates on gas fuel, the fuel pressure is higher than that of the compressor delivery air and therefore obviates any air flow into the gas passages, but when operating on liquid fuel, the steam will be at higher pressure than the gas passages and will therefore enter them. On contacting the relatively cold air in the gas fuel supply system, the steam will condense and the condensate will collect in the gas fuel passages. If an attempt is made to initiate a fuel transfer to gas fuel, or the engine is shut down and restarted on gas fuel, condensate which may have collected in the gas fuel supply passages may be injected into the engine through the gas fuel nozzles in the fuel injector when the gas fuel supply valve is opened. This may have an undesirable effect on the combustion process.
BRIEF STATEMENTS OF INVENTION
The present invention seeks, among other things, to provide a convenient means of draining condensate which has collected in the gas fuel supply passages.
Accordingly, the present invention provides a gas generator having a compressor, a combustor, combined gas and liquid fuel injector means for the combustor, steam injector means located upstream of the fuel injector means and downstream of the compressor, gas fuel supply means connected to the fuel injector means, purge valve means connected to the gas fuel supply line for venting the gas fuel supply means externally of the gas generator, and control means for scheduling the purge valve means to open whenever the gas generator is operating on liquid fuel with steam injection, whereby high pressure air and steam exits from the fuel injector means through the gas fuel supply means and is vented through the purge valve means.
The gas fuel supply means preferably comprises gas manifold means connected to the fuel injector means, and a gas fuel supply line connected to the gas manifold, the purge valve means being connected to the gas fuel supply line for venting the high pressure air and steam therefrom.
The purge valve means can comprise an upstream manual shut-off valve in addition to a purge valve scheduled by the control means, and a restriction can be provided downstream of the purge valve for restricting the volume of the purge flow so that gas generator per
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Corbett Nicholas C.
Lines Norman
Steward Lynn I. T.
Rolls-Royce plc
Thorpe Timothy S.
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