Power plants – Combustion products used as motive fluid – Combustion products generator
Patent
1997-03-13
1998-10-06
Thorpe, Timothy
Power plants
Combustion products used as motive fluid
Combustion products generator
60737, 60732, 60733, F02C 300, F23R 314, F23R 334
Patent
active
058160507
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a low-emission combustion chamber for gas turbine engines comprising an outer casing with a closing upstream end wall in which is mounted a pilot fuel injector. Spaced coaxially around the mouth of the injector is mounted a first radial flow swirler adopted to bring air radially entering therethrough to rotate around the longitudinal axis of the combustion chamber and to be mixed with injected pilot fuel and the mixture to be ignited by an igniting means to initiate a stable diffusion flame in a pilot zone. At least one second coaxial swirler is being arranged radially outwardly of the zone for bringing primary air radially entering through the second swirler and intended for the main combustion, to rotate around the longitudinal axis and to be mixed with fuel from main fuel injectors circumferentially spaced around the second swirler. To this fuel-air-mixture second air is then added for finishing the combustion in a subsequent main combustion zone.
BACKGROUND OF THE INVENTION
Gas turbine engine combustion chambers are previously known from e.g. WO 92/07221 and U.S. Pat. No. 4,069,029. Recently it has become still more important not only to reduce the emissions of carbon monoxide and unburnt hydrocarbon from combustion engines but also the emissions of nitrogen oxide. Particularly for reducing the last-mentioned a very exact and sensitive control of the entire combustion process in the combustion chamber is required. A large amount of various measures and design improvements have been suggested which imply considerable reductions of the harmful emissions of the engines but in the near future the limit values for the emissions will be further lowered stepwise and therefore still more refined control measures for the combustion process are now required. The techniques known up to now do not provide for this and therefore further improvements are necessary.
SUMMARY OF THE INVENTION
The object of the present invention therefore is to suggest a low-emission gas turbine combustion chamber of the kind referred to, in which a still further improved combustion process can be obtained thereby provide for still more reduced emissions, particularly of undesirable nitrogen oxides. According to the invention this is now made possible by the fact that the pilot zone is confined radially outwardly by a surrounding wall which at the same time constitutes the radially inner confinement of an axial outlet portion of a radial vaporization channel located inwardly of the second swirler and adapted to provide the vaporization of the injected main fuel, and because a third radial flow swirler is located axially approximately at the level of the downstream edge of the pilot zone wall and adapted to supply in a mixing zone the secondary air in a rotary motion opposite to that of the main flow of the fuel and air around the longitudinal axis.
In the two above-mentioned patent specifications, as a basic measure in order to reduce particularly the emissions of NO.sub.X, the step has been taken to divide the combustion process into several stages axially following after each other. By a detailed control of each single step it has been considered that the combustion could be better controlled and as the result the emission of harmful components reduced. By supplying the air required for the combustion in several steps the combustion temperature can be kept relatively low which is a basic prerequisite for low emissions of nitrogen oxide.
The present invention, however, is based on the concept that as far upstream as possible in the combustion chamber there is to provide such a complete and homogenous mixture of fuel and air ignited by an exactly controlled combustion process in a pilot zone, that the combustion is compiled at still at a relatively low combustion temperature within the main combustion zone without division into several axially separated stages.
BRIEF DESCRIPTION OF THE DRAWINGS
By way of example, the invention will be further described below with referenc
REFERENCES:
patent: 4069029 (1978-01-01), Hudson
patent: 4260367 (1981-04-01), Markowski et al.
patent: 4301657 (1981-11-01), Penny
patent: 5069029 (1991-12-01), Kuroda et al.
patent: 5319935 (1994-06-01), Toon et al.
patent: 5490380 (1996-02-01), Marshall
Andersson Alf
Gabrielsson Rolf
Johansson Patrik
Lundgren Sonny
Sjunnesson Anders
Kim Ted
Thorpe Timothy
Volvo Aero Corporation
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