Power plants – Combustion products used as motive fluid
Reexamination Certificate
2000-12-06
2001-08-28
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039190, C060S039463
Reexamination Certificate
active
06279310
ABSTRACT:
BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention concerns a method for starting a burner device for a gas turbine, wherein the burner device comprises at least one burner member, arranged to be supplied with a liquid fuel, and an ignition member, which is activated for igniting a fuel which is supplied to the burner member.
Such starting methods are already well known. In the prior technology, the ignition member, which preferably is formed by a separate ignition burner, is often activated by means of an ignition plug or the like, such that an ignition flame is obtained. The ignition burner uses for example liquefied petroleum gas or natural gas as fuel.
Since the invention is particularly suitable in connection with burner devices which use a liquid fuel, preferably an oil, it will below in an exemplifying but not limiting purpose be described with reference to such a burner device.
In a burner device of this kind, the main portion of the air which is supplied to a combustion chamber connected to the burner device is supplied via the flame zone which is defined by the burner member or members included in the burner device.
During the start of the burner device it is important that the concentration of fuel in an ignition zone of the burner member is such that the activation of the ignition member immediately results in a corresponding ignition of the fuel and in the generation of a burner member flame. If the fuel concentration is such that no immediate ignition and generation of a burner member flame is obtained, the mixture of fuel and incoming air will flow through the combustion chamber and into a subsequent turbine. If the ignition of the fuel takes place at such a late stage, the generated flame will extend all the way through the combustion chamber and into the turbine as far as the mixture of fuel and air which may be ignited extends. Said mixture may extend all the way to and into an exhaust channel connected to the turbine. When the exhaust channel in this manner is filled with an explosive mixture which may ignited, this may lead to the fact that an explosion takes place in the exhaust channel. Such an explosion may have devastating consequences and should therefore be avoided as far as possible.
Starting methods according to prior technology are thus very sensitive and require a very precise control of the fuel concentration in the ignition zone of the burner member or members at the moment when the fuel is supplied to said zone and the ignition of the same shall be carried out for generating a burner member flame.
SUMMARY OF THE INVENTION
A purpose with the present invention is to achieve a method by means of which the above mentioned disadvantages of the prior art are avoided. The method should guarantee that no explosive mixture of fuel and air extends through the combustion chamber, the turbine and an exhaust channel of the gas turbine connected to the turbine at the starting moment when ignition of the fuel takes place by activating the ignition member.
This purpose is achieved by means of the initially defined method, which is characterized in that the fuel which is initially supplied to the burner member and which is ignited by means of the ignition member and generates a burner member flame mainly comprises an ignition gas.
Unlike prior technology, the invention thus suggests that an ignition gas, such as for example a liquefied petroleum gas, at the starting moment is conveyed into the ignition zone via the burner member instead of a liquid fuel mixed with air. The ignition gas has the advantage of being very easily ignitable, which results in that it is ignited by the ignition member and generates a burner member flame immediately. The risk is minimal that the ignition of the gas will fail and that the gas will flow all the way to the turbine and to the exhaust channel before the ignition of the gas takes place.
According to a preferred implementation of the method, a liquid fuel is supplied to the burner member after that a burner member flame generated by said ignition gas has been obtained, in order to contribute to the generation of the burner member flame. Since a stable burner member flame already exists when the liquid fuel, preferably an oil or an oil mixture, is conveyed into the flame zone, this liquid fuel will immediately be ignited and contribute to the stability of the already generated burner member flame. The concentration of liquid fuel in the ignition zone or the flame zone is thus not as critical as in the prior technology.
According to a further preferred implementation of the method, the activation of the burner member comprises ignition of a separate ignition flame intended to ignite said ignition gas for generating the burner member flame. Such a separate ignition flame may easily obtain a considerable stability. The stability ensures in its turn a reliable ignition of the ignition gas as soon as it reaches the area in which the ignition flame exists.
According to a further preferred implementation, the burner device comprises a plurality of burner members, each of which is supplied with an ignition gas which is ignited and which generates a burner member flame at least with indirect support of said activation of the ignition member. The indirect support is a consequence of the fact that the activation of the ignition member initiates the ignition of the ignition gas at a first burner member and the generation of a burner member flame. This burner member flame is in its turn stable and strong enough to ignite the gas which is supplied to the ignition zone of a neighboring burner member and to thereby generate a burner member flame at this burner member. In such a manner a successive, almost immediate ignition of a plurality of burner members arranged in parallel and next to each other is obtained.
According to a further implementation, the burner member flame generated by said ignition gas is extinguished at at least one of said plurality of burner members when all burner members have obtained a burner member flame generated by said ignition gas. In a subsequent step, when the other burner members are supplied with a liquid fuel, no liquid fuel is supplied to the burner member or members of which the burner member flame was extinguished during the previous step. A subsequent acceleration of the gas turbine thus takes place while using only some of the burner members of the burner member device, which burner members then have burner member flames which mainly are generated by means of a liquid fuel. This use of only some of the burner members during the initial acceleration phase of the gas turbine is advantageous from the point of view of emissions and results in an improved use of the energy of the fuel which is used.
According to a further preferred implementation, the burner member or members of which the burner member flame was extinguished when all of said plurality of burner members has obtained such burner member flames, are kept extinguished during a subsequent acceleration of the gas turbine and thereafter are supplied with liquid fuel at previously defined operating conditions of the gas turbine. In such a manner the number of active burner members increases as the gas turbine approaches a suitable operational speed. During normal, continuous operation preferably all burner members are active such that they are supplied with the liquid fuel for generating burner member flames. By the step by step increase of the number of active burner members during the acceleration phase optimal combustion condition of the ignited burner members may be achieved at the same time as the amount of emissions, primarily of NO
x
, is minimised.
According to further preferred implementation, the burner device comprises a plurality of burner members arranged in a ring and directed towards a combustion chamber common for these burner members, wherein at least two ignition members are activated at burner members separated by one or more further burner members. In case contrary to expectation the activation of one ignition member w
Andersson Leif G.
Strand Torsten
ABB AB
Burns Doane Swecker & Mathis L.L.P.
Casaregola Louis J.
LandOfFree
Gas turbine starting method using gas and liquid fuels does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas turbine starting method using gas and liquid fuels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas turbine starting method using gas and liquid fuels will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2539792