JPH1082526A - Device to detect occurrence of flashback to premixture combustor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly detect the occurrence of flashaback in order to perform a stop before a combustor is damaged by sensing the occurrence of the flashback by using a plurality of optical fibers and photodetectors. SOLUTION: A combustor 1 contains a plurality of flame nozzles 12a-12e to generate flame. The flame nozzles 12a-12e are monitored by using fiber optical elements 24a-24e containing optical fibers through which a light signal is sent to photodetectors 14a-14e. The photodetectors 14a-14e feed an electric signal to a multiplexer 18 and the multiplexer 18 transmits data to a signal processor 20 before the multiplexer is operated by a gas turbine controller and monitor 22. When light is detected by the photodetector 14a-14e at a level to indicate the presence of flame in a test region where no flame is present, the information is transmitted to the controller and monitor 22 through the signal process 20 and this way turns OFF the combustor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Gas turbines generally include a compressor,
It includes one or more combustors, a fuel injection system, and a turbine. Typically, the compressor pressurizes the inlet air, which then flows in the opposite direction to the combustor and provides air for the combustion process in the combustor and is used to cool the combustor. Can be In a multi-combustor system, the combustors are positioned along the perimeter of the gas turbine and a transition duct is provided at the outlet end of each combustor to deliver hot combustion products to the turbine. Is connected to the entrance end.

[0002] Gas turbine combustors have been developed employing lean premixed combustion to reduce the emission of gases such as NOx (nitrogen oxide). One such combustor includes multiple burners mounted in a single combustion chamber. Each burner includes a flow tube having a centrally located fuel nozzle, the fuel nozzle including a central hub supporting a fuel injector (injector) and a swirl vane. In. In operation, fuel is injected through the fuel injector and mixed with swirling air in the fuel tube, producing a flame at the burner outlet. The combustion flame is stabilized by a combination of bluff body recirculation behind the central hub and vortex induced recirculation. With lean stoichiometry, lean premixed combustion achieves lower flame temperatures, thus causing lower NOx emissions.

[0003] These premix systems are susceptible to a predictable phenomenon commonly referred to as "flashback". Flashback can be caused by impurities in the fuel. Flashback can also be triggered during a mode switch when the flame is in a transition state. When a flashback occurs, the flame of the combustor travels rearward (upstream) and enters an area or cavity of the combustor chamber that is not designed to contain the flame.
The flame may also suddenly move into a combustor cavity used for an ignition mode other than the combustion mode that is operating when the flashback occurs. Any form of flashback that results in loss of combustion control and additional heating and melting of combustor parts, such as flame nozzles, that are not designed to withstand excessive heating. obtain. Operators generally have no way to recognize the occurrence of flashback until the combustor is damaged.

[0004]

SUMMARY OF THE INVENTION It is desirable to have a means for quickly detecting the occurrence of flashback so that the combustor can be shut down before it suffers damage. In the present invention, multiple optical fibers and at least one photodetector are used to sense flashback.

[0005] The features of the present invention which are believed to be novel include:
It is specifically described in the claims. However, the invention itself, structure and method of operation, together with further objects and advantages of the invention, will best be understood by referring to the following description taken in conjunction with the drawings, in which like reference numerals represent like components. Will be appreciated.

[0006]

FIG. 1 is a block diagram showing an embodiment of flashback protection according to the present invention, and FIG. 2 is a sectional view of a part of the embodiment of FIG. The combustor 1 has at least one flame nozzle (preferably a plurality of flame nozzles 12a, 12b, 12c, 12d and 1) capable of generating a flame 44.
2e). Each of the flame nozzles includes a fiber optic element 24a, 24b, 24c, 24 that includes at least one optical fiber that sends an optical signal to a respective photodetector 14a, 14b, 14c, 14d, or 14e.
It is monitored using d or 24e.

If desired, each fiber optic optical element 24a, 24b, 24c, 24d or 24e forms a bundle as shown in FIG. 2 by optical fibers 24a ', 24a "and 24a'". It may include several optical fibers. In one embodiment, each fiber optic element is at least one optically pressure sealed at one end 26 or both ends in a protective tube (indicated by tube 25a in FIG. 2) capable of withstanding the operating environment. Includes multimode fiber. In one embodiment, the optical fiber is comprised of quartz and the tube 25a is comprised of stainless steel. If desired, an optical microlens may be used to selectively collect light from the flame present during the flashback from a portion of the protective tube. The tube is located in the combustor casing 10 (air passage 46
Inner) hole and combustor liner 48. The tube is
It can be attached to the combustor casing using a compression fit connection (not shown).

[0008] At the other end of the tube is mounted a photodetector. In one embodiment, the photodetector includes a semiconductor photodiode made of a material such as silicon, gallium arsenide, silicon carbide, germanium, gallium nitride or gallium phosphide. The light detector may be located outside the partition 5 of the engine holding the combustor, and thus may be protected from harsh combustion environments. Each photodetector is capable of sending an electrical signal to a multiplexer 18 which signals data prior to being actuated by gas turbine controller / monitor 22 (shown in FIG. 1). It can be sent to the processor 20.

Although one fiber optic element and one photodetector are shown per flame nozzle, any number of configurations are possible. For example, as shown in FIG.
All fiber optics are arranged together in a bundle 54 and are arranged by one photodetector 56, or a single fiber (not shown)
While being optically coupled to one another and disposed by one photodetector,
a, 24b, 24c, 24d and 24e may be used for each nozzle. Whenever multiple photodetectors are used (multiplexer 18 in FIG. 1)
A simple scanning or multiplexing system (shown as) may be used as an interface between the multiple sensing system and the signal processor.

As shown in FIG. 2, in a preferred embodiment,
The fiber optic elements are indicated or pointed to in the area of the flame nozzle (hereinafter referred to as the test area) 13a and 13b, where the flame is not present under normal operating conditions. One such test zone is at the rear of the flame nozzle 12a or 12b, immediately forward (downstream) from the swirl vanes 52a or 52b and the fuel injector 50a or 50b. At this location, the flame nozzle is not hot enough to emit significant amounts of infrared radiation (IR), or otherwise a broad spectrum responsive semiconductor photodiode (eg, silicon, germanium or gallium arsenide) Will be saturated with a small bandgap. This simplifies the detection mechanism since no IR filter is required.

If desired, the tube 2 can be used for many purposes.
A plurality of fiber optic elements 24b 'and 24b "provided in 5b' and 25b", respectively, can be used to monitor flashback at the flame nozzle. FIG. 3 is a circuit diagram illustrating an exemplary flashback protection embodiment of the present invention. The fiber optic elements 24a, 24b and 24c transmit the detected arbitrary light to the respective photodetectors 1.
4a, 14b and 14c and the photodetectors 14a, 1
4b and 14c send any resulting electrical signals to multiplexer 18. Multiplexer 18
Are, for example, the field effect transistors 34a, 34b and 3
4c. A shift register 45 may control the timing of the switch operation, and a pair of amplifier 38 and resistor 40 may be used for signal amplification prior to signal transmission from the multiplexer to signal processor 20. The drawing in FIG. 3 is for illustration only. In other embodiments, for example, an analog to digital converter is used for switching, and then amplification occurs digitally.

When light is detected by the photodetector at a level indicating the presence of a flame in the test area where the flame must not be present, that information is passed through the signal processor 20 (shown in FIG. 1). Is transmitted to the controller / monitor 22 so that the combustor 1 can be turned off. While only certain preferred features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of flashback protection according to the present invention.

FIG. 2 is a partial cross-sectional view of the embodiment of FIG.

FIG. 3 is a circuit diagram showing an embodiment of flashback protection according to the present invention.

FIG. 4 is a partial block diagram showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Combustor 5 Partition 10 Combustor casing 12a, 12b, 12c, 12d, 12e Flame nozzle 13a, 13b Test area 14a, 14b, 14c, 14d, 14e, 56 Photodetector 18 Multiplexer 20 Signal processor 22 Gas turbine controller / Monitors 24a, 24b, 24c, 24d, 24e, 24b ',
24b "fiber optical element 24a ', 24a", 24a'"optical fiber 25a, 25b ', 25b" tube 26 one end 34a, 34b, 34c field effect transistor 38 amplifier 40 resistor 44 flame 45 shift register 46 air passage 48 combustor Liners 50a, 50b Fuel injectors 52a, 52b Swirl vane 54 Bundle

Continued on the front page (72) Inventor Jefferi Alan Robbett United States of America, New York, Scotia, Robinson Road, No. 3 (72) Inventor Emily Icy Shue United States of America, New York, Schenectady, Valencia Road , 1417

Claims (4)

[Claims] 1. An apparatus for detecting the occurrence of flashback in a premixed combustor system including at least one flame nozzle, comprising: at least one photodetector; said at least one photodetector and said combustion. At least one fiber optic element coupled to a test area of the instrument system, wherein the test area is free of a respective flame of the at least one flame nozzle under normal operating conditions; An apparatus for detecting the occurrence of flashback in a premixed combustor system comprising at least one fiber optic element and a signal processor for monitoring a signal of said at least one photodetector. 2. The apparatus of claim 1, wherein said at least one fiber optic includes at least one optical fiber disposed within a protective tube. 3. The at least one flame nozzle includes a plurality of flame nozzles, the at least one photodetector includes a plurality of photodetectors, and the at least one fiber optic element includes: A plurality of fiber optic elements, each fiber optic element having a respective one of the plurality of photodetectors and a respective one of the plurality of flame nozzles.
The apparatus of claim 1, wherein the apparatus is coupled between two respective test areas. 4. The at least one flame nozzle includes a plurality of flame nozzles, the at least one fiber optic element includes a plurality of fiber optic elements,
The apparatus of claim 1, wherein each fiber optic element is coupled between the at least one photodetector and a respective test area of a respective one of the plurality of flame nozzles.