Combustion – Separately supplied or controlled – physically related flame... – Having common flame chamber or shield means
Reexamination Certificate
1999-01-22
2001-02-13
Lazarus, Ira S. (Department: 3743)
Combustion
Separately supplied or controlled, physically related flame...
Having common flame chamber or shield means
C431S284000, C431S009000, C431S258000, C431S263000
Reexamination Certificate
active
06186775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a burner for operating a heat generator.
2. Discussion of Background
EP-0 780 629 A2 has disclosed a burner which comprises a swirl generator on the incident-flow side, the flow formed herein being passed smoothly into a mixing section. This is done with the aid of a flow geometry, which is formed at the start of the mixing section for this purpose and consists of transition passages which cover sectors of the end face of the mixing section, in accordance with the number of acting sectional bodies of the swirl generator, and run helically in the direction of flow. On the outflow side of these transition passages, the mixing section has a number of prefilming bores, which ensure that the flow velocity along the tube wall is increased. This is then followed by a combustion chamber, the transition between the mixing section and the combustion chamber being formed by a jump in cross section, in the plane of which a backflow zone or backflow bubble forms.
The swirl intensity in the swirl generator is therefore selected in such a way that the breakdown of the vortex does not take place inside the mixing section but further downstream, as explained above, in the region of the jump in cross section. The length of the mixing section is dimensioned in such a way that an adequate mixture quality is ensured for all types of fuel.
Although this burner, compared with those from the prior art, guarantees a significant improvement with regard to intensification of the flame stability, lower pollutant emissions, lower pulsations, complete burn-out, large operating range, good cross-ignition between the various burners, compact type of construction, improved mixing, etc., it has been found that this burner has no autonomous measures in order to be able to reliably run the gas turbine in particular in its transient load ranges. For example, in the part-load range, the burner must be assisted with a back up flame. In this case, the integration of such measures in the burner must not lead to any additional pollutant emissions, which could jeopardize the operational and emissive advantages of the burner taken as a basis. There is also the fact that these burners, in gas turbines, are ignited in a conventional manner by means of a special igniter. These igniters usually operate at a high voltage, which delivers the ignition spark, which either serves directly as ignition source at high output or ignites an ignition torch. These igniters require a separate leadthrough and seal for the igniter and its conduits through the casing of the gas turbine right into the combustion chamber. However, the existing igniter systems have the following disadvantages:
a) costly separate leadthrough and seal for the igniter and its conduits through the casing of the gas turbine right into the combustion chamber;
b) cross-ignition inside the combustion chamber on account of the small number of igniters (usually only 1 igniter for reasons of cost);
c) thermal loading of the igniter due to the positioning in the combustion chamber, which, for example, requires cooling of the igniter, for which reason leakages occur due to seals which may be unsound;
d) highly susceptible to condensed water, in which case short circuits divert the ignition spark.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention, in a burner of the aforementioned type, is to propose novel measures which ensure intensification of the flame stability for a stable operation, in particular in the transient load ranges, always with the further proviso that the pollutant emissions remain low, and, at the same time, when these measures are taken, steps are to be taken which are able to remove the abovementioned disadvantages concerning ignition systems.
For this purpose, the burner is extended in such a way that an annular system which is intended for the provision of an air/fuel mixture and generally functions as a pilot stage is provided in the region of its transition to the combustion space arranged downstream. A number of outlet bores which are provided in the peripheral direction and lead into the combustion space create corresponding pilot burners, which for stability reasons are run by diffusion operation and act directly in the combustion space.
The essential advantages of the subject matter of the invention may be seen in the fact that these individual pilot burners are operated with a low proportion of gas, so that the gas introduced there mixes with a relatively small proportion of air and burns as premixed flame with minimized pollutant emissions.
This air quantity, with the aid of impingement cooling, first of all performs the task of cooling the side remote from the combustion chamber before it then mixes with the gas and subsequently, as premixed flame with minimized pollutant emissions, maintains the piloting of the combustion space.
Due to this impingement cooling, the surface of the pilot-gas ring is largely isolated from the hot gas and from the flame radiation from the combustion space, so that the thermal loading in this region is substantially reduced.
Even during 100% pilot operation, the individual pilot burners, for stability reasons, burn by diffusion operation, since here the proportion of cooling air compared with the gas is very small.
The subject matter of the invention also achieves the effect that the minimized cooling quantity can likewise be fed to the combustion process.
The directed introduction of said cooling air is at the same time used to provide an ignition device, integrated there, for the respective pilot burner, whereby this integrated ignition device for the pilot burner becomes a component part of the burner system, and this component part is interchangeably mounted in the gas turbine. Due to the integration of the ignition device in the burner, a plurality of pilot burners or all the pilot burners can be equipped with an igniter, as a result of which optimum cross-ignition properties are achieved. The pilot burner is preferably ignited by means of an incandescent ignition pin or by means of a spark plug.
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Jansohn Peter
Koster Dieter
Ruck Thomas
ABB Research Ltd.
Burns Doane Swecker & Mathis L.L.P.
Lazarus Ira S.
Lee David
LandOfFree
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