EP1182399A2 - Process for reducing the thermoacoustic oscillations in a turbo-engine using a combustion system - Google Patents

Process for reducing the thermoacoustic oscillations in a turbo-engine using a combustion system Download PDF

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Publication number
EP1182399A2
EP1182399A2 EP01116012A EP01116012A EP1182399A2 EP 1182399 A2 EP1182399 A2 EP 1182399A2 EP 01116012 A EP01116012 A EP 01116012A EP 01116012 A EP01116012 A EP 01116012A EP 1182399 A2 EP1182399 A2 EP 1182399A2
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EP
European Patent Office
Prior art keywords
fuel
burner
pulsed
air mixture
frequency
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EP01116012A
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German (de)
French (fr)
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EP1182399A3 (en
Inventor
Ephraim Dr. Gutmark
Christian Oliver Dr. Paschereit
Wolfgang Weisenstein
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General Electric Technology GmbH
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Alstom Schweiz AG
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Publication of EP1182399A2 publication Critical patent/EP1182399A2/en
Publication of EP1182399A3 publication Critical patent/EP1182399A3/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C15/00—Apparatus in which combustion takes place in pulses influenced by acoustic resonance in a gas mass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C7/00—Combustion apparatus characterised by arrangements for air supply
    • F23C7/002—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
    • F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
    • F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
    • F23R3/286—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply having fuel-air premixing devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2205/00—Pulsating combustion
    • F23C2205/10—Pulsating combustion with pulsating fuel supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
    • F23C2900/07002—Premix burners with air inlet slots obtained between offset curved wall surfaces, e.g. double cone burners
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
    • F23R2900/00—Special features of, or arrangements for continuous combustion chambers; Combustion processes therefor
    • F23R2900/00013—Reducing thermo-acoustic vibrations by active means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
    • F23R2900/00—Special features of, or arrangements for continuous combustion chambers; Combustion processes therefor
    • F23R2900/00014—Reducing thermo-acoustic vibrations by passive means, e.g. by Helmholtz resonators

Definitions

  • the invention relates to a method for reducing thermoacoustic Vibrations in a fluid flow machine with a burner system that provides at least one burner into which at least one burner nozzle Fuel is introduced, the combustion air flowing into the burner is mixed into a fuel / air mixture, which in one, to the Burner system subsequent combustion chamber is brought to ignition.
  • thermoacoustic vibrations often occur in the combustion chambers, which arise on the burner as fluid-mechanical instability waves and lead to flow vortices that have a strong influence on the entire combustion process and lead to undesired periodic heat releases within the combustion chamber, which are associated with strong pressure fluctuations.
  • the high pressure fluctuations are associated with high vibration amplitudes, which can lead to undesirable effects, such as a high mechanical load on the combustion chamber housing, an increased NO x emission due to inhomogeneous combustion and even an extinguishing of the flame within the combustion chamber.
  • Thermoacoustic vibrations are based, at least in part, on flow instabilities the burner flow, which is expressed in coherent flow structures, and that affect the mixing processes between air and fuel.
  • cooling air is in the form of a cooling air film over the Headed combustion chamber walls.
  • the cooling air film also works sound absorbing and helps to reduce thermoacoustic vibrations at.
  • the Cooling air flow into the combustion chamber is significantly reduced and all of the air is through directed the burner.
  • the sound absorbing is also reduced Cooling air film, which reduces the sound-absorbing effect and with the problems associated with the undesirable vibrations are increasing again.
  • thermoacoustic vibration amplitudes is associated with the disadvantage that the injection of fuel at the head stage is accompanied by an increase in the emission of NO x .
  • thermoacoustic Vibrations Although the emission values deteriorate only marginally, however, this can be particularly useful in gas turbines due to instabilities which form high due to thermoacoustic vibrations Frequencies in the kHz range are insufficiently countered.
  • the invention is based on the object of a method for reducing thermoacoustic Vibrations in a fluid power machine with a burner system, which provides at least one burner, in the at least one burner nozzle Fuel is introduced with the flowing into the burner Combustion air is mixed into a fuel / air mixture that is in a combustion chamber connected to the burner system for ignition will be developed in such a way that high-frequency thermoacoustic vibrations effectively and without the need for costly and maintenance-intensive components can be suppressed.
  • the method according to the preamble of claim 1 provides the high-frequency, combustion-driven vibrations or thermoacoustic Vibrations as they are called by a low frequency Suppress excitation of the fuel mass flow.
  • the fuel pulsed through the burner nozzle into the burner with variable or fixed Frequencies between 0.1 Hz and 1000 Hz, preferably between 1 and 20 Hz, brought in.
  • thermoacoustic instabilities with a considerable high-frequency component due to low-frequency modulation of the fuel mass flow through pulsed fuel injection just the high-frequency Proportion of thermoacoustic vibrations can be effectively suppressed.
  • thermoacoustic instabilities are based on the one hand on coherent vortex detachments, which arise, for example, immediately after the burner outlet, and on the other hand on fluctuations in the mixture during the mixing of the fuel with the combustion air in the premixing stage. If one influences the phase position between the fuel injection and the periodic heat release due to one of the excitation mechanisms, the combustion instabilities can be controlled. In particular, it is important to disturb the phase position between the periodic heat release and the fuel injection in such a way that the so-called Rayleigh criterion is no longer met.
  • Spq represents the cross spectrum between pressure fluctuations p 'and fluctuations in the heat release q' and ⁇ pq the phase difference.
  • the Rayleigh index can be set to G (x) ⁇ 0, which dampens the system.
  • the suppression of combustion-driven vibrations is therefore based on that the phases of fuel injection and heat release are not in the Are kind of correlated that the Rayleigh criterion is met.
  • Liquid or gaseous fuel passes from a fuel reservoir 1 an injector 2 into the interior of a burner 3 in which the atomized fuel together with combustion air forms a fuel / air mixture that after complete mixing reaches the combustion chamber 4, in which it is ignited and is available for the operation of a gas turbine, for example.
  • the injection nozzle 2 can be controlled in such a way that its nozzle opening can be closed, so that depending on the control of the injector 2, a pulsed fuel input in the burner 3 is possible.
  • a Frequency generator 5 is provided, whose control signals from an amplification unit 6 amplified and fed to the injector 2.
  • Any predefinable frequency values can be set, the pulse frequency of the fuel input into the burner 3. As a rule, you can do this empirically determined frequencies at which effective suppression thermoacoustic instabilities can be observed.
  • FIG. 2 shows a diagram based on the effect of the invention Measure for the formation of thermoacoustic vibrations in the kHz range can be seen.
  • the diagram shows amplitude values of pressure vibrations along the abscissa and plotted a scale along the ordinate showing the strength of the formation of Reproduces pressure vibrations.
  • the entered line with the filled squares represents a major instability in the kHz range.
  • a low frequency excitation see the Line with the filled diamonds
  • the high-frequency instability could be suppressed by 39 dB. in this connection only the amplitude of the excitation signal is changed, its frequency remains constant in the case shown in FIG. 2.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

The method involves feeding fuel into the burner (3) via a burner nozzle (2) in a pulsed manner with a variable or fixed frequency between 1 Hz and 1000 Hz. The pulsed fuel delivery takes place so that the formation of the fuel/air mixture for the burner is also pulsed. Open loop fuel delivery can be employed that is independent of the thermoacoustic vibrations.

Description

Technisches GebietTechnical field

Die Erfindung bezieht sich auf ein Verfahren zur Reduzierung thermoakustischer Schwingungen in einer Strömungskraftmaschinen mit einem Brennersystem, das wenigstens einen Brenner vorsieht, in den über wenigstens eine Brennerdüse Brennstoff eingebracht wird, der mit in den Brenner einströmenden Verbrennungszuluft zu einem Brennstoff-/Luftgemisch vermischt wird, das in einer, sich an das Brennersystem anschließenden Brennkammer zur Zündung gebracht wird.The invention relates to a method for reducing thermoacoustic Vibrations in a fluid flow machine with a burner system that provides at least one burner into which at least one burner nozzle Fuel is introduced, the combustion air flowing into the burner is mixed into a fuel / air mixture, which in one, to the Burner system subsequent combustion chamber is brought to ignition.

Stand der TechnikState of the art

Beim Betrieb von Strömungskraftmaschinen, wie beispielsweise Gasturbinenanlagen, treten in den Brennkammern häufig unerwünschte, so genannte thermoakustische Schwingungen auf, die am Brenner als strömungsmechanische Instabilitätswellen entstehen und zu Strömungswirbeln führen, die den gesamten Verbrennungsvorgang stark beeinflussen und zu unerwünschten periodischen Wärmefreisetzungen innerhalb der Brennkammer führen, die mit starken Druckschwankungen verbunden sind. Mit den hohen Druckschwankungen sind hohe Schwingungsamplituden verknüpft, die zu unerwünschten Effekten, wie etwa zu einer hohen mechanischen Belastung des Brennkammergehäuses, einer erhöhten NOx-Emission durch eine inhomogene Verbrennung und sogar zu einem Erlöschen der Flamme innerhalb der Brennkammer führen können.During the operation of turbo engines, such as gas turbine systems, undesirable, so-called thermoacoustic vibrations often occur in the combustion chambers, which arise on the burner as fluid-mechanical instability waves and lead to flow vortices that have a strong influence on the entire combustion process and lead to undesired periodic heat releases within the combustion chamber, which are associated with strong pressure fluctuations. The high pressure fluctuations are associated with high vibration amplitudes, which can lead to undesirable effects, such as a high mechanical load on the combustion chamber housing, an increased NO x emission due to inhomogeneous combustion and even an extinguishing of the flame within the combustion chamber.

Thermoakustische Schwingungen beruhen zumindest teilweise auf Strömungsinstabilitäten der Brennerströmung, die sich in kohärenten Strömungsstrukturen äußern, und die die Mischungsvorgänge zwischen Luft und Brennstoff beeinflussen. Thermoacoustic vibrations are based, at least in part, on flow instabilities the burner flow, which is expressed in coherent flow structures, and that affect the mixing processes between air and fuel.

Bei herkömmlichen Brennkammern wird Kühlluft in Art eines Kühlluftfilm über die Brennkammerwände geleitet. Neben dem Kühleffekt wirkt der Kühlluftfilm auch schalldämpfend und trägt zur Verminderung von thermoakustischen Schwingungen bei. In modernen Gasturbinenbrennkammern mit hohen Wirkungsgraden, niedrigen Emissionen und einer konstanten Temperaturverteilung am Turbineneintritt ist der Kühlluftstrom in die Brennkammer deutlich reduziert und die gesamte Luft wird durch den Brenner geleitet. Jedoch reduziert sich zugleich auch der schalldämpfende Kühlluftfilm, wodurch die schalldämpfende Wirkung herabgesetzt wird und die mit den unerwünschten Schwingungen verbundenen Probleme wieder verstärkt auftreten.In conventional combustion chambers, cooling air is in the form of a cooling air film over the Headed combustion chamber walls. In addition to the cooling effect, the cooling air film also works sound absorbing and helps to reduce thermoacoustic vibrations at. In modern gas turbine combustion chambers with high efficiencies, low ones Emissions and a constant temperature distribution at the turbine inlet is the Cooling air flow into the combustion chamber is significantly reduced and all of the air is through directed the burner. However, the sound absorbing is also reduced Cooling air film, which reduces the sound-absorbing effect and with the problems associated with the undesirable vibrations are increasing again.

Eine weitere Möglichkeit der Schalldämpfung besteht im Ankoppeln so genannter Helmholtz-Dämpfern im Bereich der Brennkammer oder der Kühlluftzufuhr. Jedoch ist bei modernen Brennkammerkonstruktionen das Vorsehen derartiger Helmholtz-Dämpfer auf Grund enger Platzverhältnisse mit großen Schwierigkeiten verbunden.Another possibility of sound absorption is to connect so-called Helmholtz dampers in the area of the combustion chamber or the cooling air supply. however is the provision of such Helmholtz dampers in modern combustion chamber designs associated with great difficulties due to the limited space.

Daneben ist bekannt, dass den im Brenner auftretenden strömungsmechanischen Instabilitäten und den damit verbundenen Druckschwankungen dadurch entgegengetreten werden kann, indem die Brennstoffflamme durch zusätzliche Eindüsung von Brennstoff stabilisiert werden kann. Eine derartige Eindüsung von zusätzlichem Brennstoff erfolgt über die Kopfstufe des Brenners, in der eine auf der Brennerachse liegende Düse für die Pilot-Brennstoffgaszuführung vorgesehen ist, was jedoch zu einer Anfettung der zentralen Flammstabilisierungszone führt. Diese Methode der Verminderung von thermoakustischen Schwingungsamplituden ist jedoch mit dem Nachteil verbunden, dass die Eindüsung von Brennstoff an der Kopfstufe mit einer Erhöhung der Emission von NOx einhergeht.In addition, it is known that the fluid mechanical instabilities occurring in the burner and the pressure fluctuations associated therewith can be counteracted by stabilizing the fuel flame by additional injection of fuel. Such injection of additional fuel takes place via the head stage of the burner, in which a nozzle is provided on the burner axis for the pilot fuel gas supply, but this leads to an enrichment of the central flame stabilization zone. However, this method of reducing thermoacoustic vibration amplitudes is associated with the disadvantage that the injection of fuel at the head stage is accompanied by an increase in the emission of NO x .

Zwar ist erkannt worden, dass eine gepulste Zugabe von zusätzlichem Brennstoff über die Kopfstufe in den Brenner zu einer leichten Reduzierung von thermoakustischen Schwingungen führt, obwohl sich die Emissionswerte nur unwesentlich verschlechtern, doch können auf diese Weise insbesondere den sich in Gasturbinen aufgrund thermoakustischer Schwingungen ausbildenden Instabilitäten mit hohen Frequenzen im kHz-Bereich nur ungenügend entgegengetreten werden.It has been recognized that a pulsed addition of additional fuel via the head stage into the burner for a slight reduction in thermoacoustic Vibrations, although the emission values deteriorate only marginally, however, this can be particularly useful in gas turbines due to instabilities which form high due to thermoacoustic vibrations Frequencies in the kHz range are insufficiently countered.

Gerade Instabilitäten im Strömungsfluß innerhalb des Brennersystems mit hohen Frequenzen sind mit den bisher bekannten technischen Mitteln schwierig zu kontrollieren. Versuche durch aktive Einflußnahme, bspw. durch gezieltes Einkoppeln von Antischallfeldern in das Brennersystem zur Unterdrückung der hochfrequenten Druckschwankungen schlugen mangels geeigneter Aktoren fehl, die gezielt Druckschwingungen mit hoher Amplitude zu erzeugen in der Lage sein sollten. Zudem müßten derartige Aktoren schnell ansprechbar sein und die Eigenschaft besitzen Anwortsignale auf entsprechend gewonnene Instabilitätssignale in geeigneter Leistung zu generieren. Derartige Aktoren sind jedoch weder mit den gewünschten Eigenschaften verfügbar noch finanziell und in Bezug auf ihre Anfälligkeit im operativen Gebrauch tragbar.Especially instabilities in the flow flow within the burner system with high Frequencies are difficult to control with the technical means known to date. Experiments through active influence, for example through targeted coupling of Anti-noise fields in the burner system to suppress the high frequency Pressure fluctuations failed due to the lack of suitable actuators, the targeted pressure fluctuations should be able to produce with high amplitude. moreover such actuators should be responsive and have the property Response signals to correspondingly obtained instability signals with suitable power to generate. However, such actuators have neither the desired properties still available financially and in terms of its vulnerability in operations Use portable.

Darstellung der ErfindungPresentation of the invention

Der Erfindung liegt die Aufgabe zu Grunde ein Verfahren zur Reduzierung thermoakustischer Schwingungen in einer Strömungskraftmaschinen mit einem Brennersystem, das wenigstens einen Brenner vorsieht, in den über wenigstens eine Brennerdüse Brennstoff eingebracht wird, der mit in den Brenner einströmenden Verbrennungszuluft zu einem Brennstoff-/Luftgemisch vermischt wird, das in einer, sich an das Brennersystem anschließenden Brennkammer zur Zündung gebracht wird, derart weiterzubilden, dass hochfrequente thermoakustische Schwingungen effektiv und ohne die Notwendigkeit kosten- und wartungsintensiver Komponenten unterdrückt werden können.The invention is based on the object of a method for reducing thermoacoustic Vibrations in a fluid power machine with a burner system, which provides at least one burner, in the at least one burner nozzle Fuel is introduced with the flowing into the burner Combustion air is mixed into a fuel / air mixture that is in a combustion chamber connected to the burner system for ignition will be developed in such a way that high-frequency thermoacoustic vibrations effectively and without the need for costly and maintenance-intensive components can be suppressed.

Die Lösung der der Erfindung zu Grunde liegenden Aufgabe ist im Anspruch 1 angegeben. Den Erfindungsgedanken vorteilhaft weiterbildende Merkmale sind Gegenstand der Unteransprüche sowie der Beschreibung zu entnehmen. The solution to the problem on which the invention is based is specified in claim 1. Features that advantageously further develop the inventive concept are the subject matter the subclaims and the description.

Erfindungsgemäß sieht das Verfahren gemäß dem Oberbegriff des Anspruchs 1 vor, die hochfrequenten, verbrennungsgetriebenen Schwingungen oder auch thermoakustischen Schwingungen, wie sie bezeichnet werden, durch eine niederfrequente Anregung des Brennstoffmassenstromes zu unterdrücken. So wird erfindungsgemäß der Brennstoff durch die Brennerdüse in den Brenner gepulst mit variablen oder festen Frequenzen zwischen 0.1 Hz und 1000 Hz, vorzugsweise zwischen 1 und 20 Hz, eingebracht.According to the invention, the method according to the preamble of claim 1 provides the high-frequency, combustion-driven vibrations or thermoacoustic Vibrations as they are called by a low frequency Suppress excitation of the fuel mass flow. So according to the invention the fuel pulsed through the burner nozzle into the burner with variable or fixed Frequencies between 0.1 Hz and 1000 Hz, preferably between 1 and 20 Hz, brought in.

Durch eine derart mit niedrigen Frequenzen durchgeführte gepulste Einspeisung des Hauptbrennstoffes in den Brenner zur weiteren Vermischung zu einem Brennstoff/Luftgemisches ist es möglich, kommerziell erhältliche und zuverlässig arbeitende Aktoren für die Brennstoffanregung bzw. Brennstoffeinspeisung einzusetzen.By means of a pulsed feed-in to the Main fuel in the burner for further mixing into a fuel / air mixture it is possible to have commercially available and reliable working Use actuators for fuel excitation or fuel feed.

Die der Erfindung in unerwarteter Weise zugrundeliegende Erkenntnis ist die Tatsache, dass unabhängig von der Ausbildung thermoakustischer Instabilitäten mit einem beträchtlichen hochfrequenten Anteil durch niederfrequente Modulation des Brennstoffmassenstromes durch gepulste Brennstoffeindüsung eben der hochfrequente Anteil der thermoakustischen Schwingungen wirkungsvoll unterdrückt werden kann.The finding on which the invention is based unexpectedly is the fact that regardless of the formation of thermoacoustic instabilities with a considerable high-frequency component due to low-frequency modulation of the fuel mass flow through pulsed fuel injection just the high-frequency Proportion of thermoacoustic vibrations can be effectively suppressed.

Bislang herrschte die weitverbreitete Auffassung, dass es lediglich durch Einspeisung hochfrequenter Gegenschwingungen möglich sei den hochfrequenten Instabilitäten zu begegnen. Hält man sich jedoch den treibenden Mechanismus für die Ausbildung thermoakustischer Instabilitäten vor Augen, so basieren diese zum einen auf kohärente Wirbelablösungen, die bspw. unmittelbar nach dem Brenneraustritt entstehen, und zum anderen auf Mischungsbruchschwankungen während der Durchmischung des Brennstoffes mit der Verbrennungszuluft in der Vormischstufe. Beeinflußt man nun die Phasenlage zwischen der Brennstoffeindüsung und der periodischen Wärmefreisetzung aufgrund eines der Anregungsmechanismen, kann man die Verbrennungsinstabilitäten kontrollieren. Insbesondere gilt es die Phasenlage zwischen der periodischen Wärmefreisetzung und der Brennstoffeindüsung derart zu stören, so dass das sogenannte Rayleigh-Kriterium nicht mehr erfüllt ist. Auf diese Weise kann der treibende Mechanismus für das Auftreten von thermoakustischen Schwingungen unterbunden werden.
Zur Unterdrückung der verbrennungsgetriebenen Schwingungen gilt es insbesondere, die Phasen der Brennstoffeindüsung und der Wärmefreisetzung derart zu korrelieren, daß das Rayleigh-Kriterium nicht erfüllt ist. Es gilt: G(x) = 2∫|Spq (x,f)|cos(Φpq )df So far, there has been a widespread view that it is only possible to counter the high-frequency instabilities by feeding in high-frequency countervibrations. However, if you keep in mind the driving mechanism for the formation of thermoacoustic instabilities, they are based on the one hand on coherent vortex detachments, which arise, for example, immediately after the burner outlet, and on the other hand on fluctuations in the mixture during the mixing of the fuel with the combustion air in the premixing stage. If one influences the phase position between the fuel injection and the periodic heat release due to one of the excitation mechanisms, the combustion instabilities can be controlled. In particular, it is important to disturb the phase position between the periodic heat release and the fuel injection in such a way that the so-called Rayleigh criterion is no longer met. In this way, the driving mechanism for the occurrence of thermoacoustic vibrations can be prevented.
To suppress the combustion-driven vibrations, it is particularly important to correlate the phases of fuel injection and heat release in such a way that the Rayleigh criterion is not met. The following applies: G ( x ) = 2∫ | S pq ( x . f ) | Cos ( Φ pq ) df

Spq stellt hierbei das Kreuzspektrum zwischen Druckfluktuationen p' und Fluktuationen der Wärmefreisetzung q' dar und pq die Phasendifferenz. Durch Wahl der korrekten Phasendifferenz zwischen der Wärmefreisetzung, die durch die modulierte Brennstoffeindüsung beeinflußbar ist, und dem Drucksignal kann der Rayleigh-Index auf G(x) < 0 eingestellt werden, wodurch das System gedämpft ist.Spq represents the cross spectrum between pressure fluctuations p 'and fluctuations in the heat release q' and  pq the phase difference. By choosing the correct phase difference between the heat release that can be influenced by the modulated fuel injection and the pressure signal, the Rayleigh index can be set to G (x) <0, which dampens the system.

Die Unterdrückung der verbrennungsgetriebenen Schwingungen beruht daher darauf, daß die Phasen der Brennstoffeindüsung und der Wärmefreisetzung nicht in der Art korreliert sind, daß das Rayleigh-Kriterium erfüllt ist.The suppression of combustion-driven vibrations is therefore based on that the phases of fuel injection and heat release are not in the Are kind of correlated that the Rayleigh criterion is met.

Kurze Beschreibung der ErfindungBrief description of the invention

Die Erfindung wird nachstehend ohne Beschränkung des allgemeinen Erfindungsgedankens anhand von Ausführungsbeispielen unter Bezugnahme auf die Zeichnung exemplarisch. Es zeigen:

Fig. 1
Blockdiagramm zur Darstellung einer verwendeten Steuerkette zur Unterdrückung thermoakustischer Schwingungen innerhalb eines Brennersystems und
Fig. 2
Diagramm zur Darstellung der Effizienz des erfindungsgemäßen Verfahrens.
The invention is exemplified below without restricting the general inventive concept on the basis of exemplary embodiments with reference to the drawing. Show it:
Fig. 1
Block diagram to illustrate a control chain used to suppress thermoacoustic vibrations within a burner system and
Fig. 2
Diagram showing the efficiency of the method according to the invention.

Wege zur Ausführung der Erfindung, gewerbliche VerwendbarkeitWAYS OF CARRYING OUT THE INVENTION, INDUSTRIAL APPLICABILITY

Aus einem Brennstoffreservoir 1 gelangt flüssiger oder gasförmiger Brennstoff über eine Einspritzdüse 2 in das Innere eines Brenners 3, in dem der zerstäubte Brennstoff zusammen mit Verbrennungsluft ein Brennstoff-/Luftgemisch bildet, das nach vollständiger Durchmischung in die Brennkammer 4 gelangt, in der es gezündet wird und für den Betrieb bspw. einer Gasturbine zur weiteren Verfügung steht.Liquid or gaseous fuel passes from a fuel reservoir 1 an injector 2 into the interior of a burner 3 in which the atomized fuel together with combustion air forms a fuel / air mixture that after complete mixing reaches the combustion chamber 4, in which it is ignited and is available for the operation of a gas turbine, for example.

Die Einspritzdüse 2 ist derart ansteuerbar, dass ihre Düsenöffnung schließbar ist, sodass in Abhängigkeit der Ansteuerung der Einspritzdüse 2 ein gepulster Brennstoffeintrag in den Brenner 3 möglich ist. Zur Ansteuerung der Einspritzdüse 2 ist ein Frequenzgenerator 5 vorgesehen, dessen Steuersignale von einer Verstärkungseinheit 6 verstärkt und der Einspritzdüse 2 zugeleitet werden. Am Frequenzgenerator 5 können beliebig vorgebbare Frequenzwerte eingestellt werden, die die Pulsfrequenz des Brennstoffeintrages in den Brenner 3 vorgeben. In aller Regel bieten sich hierfür empirisch ermittelte Frequenzen an, bei denen eine wirkungsvolle Unterdrückung thermoakustischer Instabilitäten zu beobachten sind.The injection nozzle 2 can be controlled in such a way that its nozzle opening can be closed, so that depending on the control of the injector 2, a pulsed fuel input in the burner 3 is possible. To control the injector 2 is a Frequency generator 5 is provided, whose control signals from an amplification unit 6 amplified and fed to the injector 2. On the frequency generator 5 Any predefinable frequency values can be set, the pulse frequency of the fuel input into the burner 3. As a rule, you can do this empirically determined frequencies at which effective suppression thermoacoustic instabilities can be observed.

In Figur 2 ist ein Diagramm dargestellt, anhand dem die Wirkung der erfindungsgemäßen Massnahme für die Ausbildung von thermoakustischen Schwingungen im kHz-Bereich zu entnehmen ist.FIG. 2 shows a diagram based on the effect of the invention Measure for the formation of thermoacoustic vibrations in the kHz range can be seen.

Im Diagramm sind entlang der Abszisse Amplitudenwerte von Druckschwingungen und entlang der Ordinate eine Skala aufgetragen, die die Stärke der Ausbildung von Druckschwingungen wiedergibt.The diagram shows amplitude values of pressure vibrations along the abscissa and plotted a scale along the ordinate showing the strength of the formation of Reproduces pressure vibrations.

Die eingetragene Linie mit den ausgefüllten Quadraten stellt eine Hauptinstabilität im kHz Bereich dar. Durch die Einprägung einer niederfrequenten Anregung (siehe die Linie mit den ausgefüllten Rauten), deren Frequenz bei 1.5% der Instabilitätsfrequenz lag, konnte die hochfrequente Instabilität um 39 dB unterdrückt werden. Hierbei wird lediglich die Amplitude des Anregungssignal verändert, seine Frequenz bleibt im gezeigten Fall der Figur 2 konstant. The entered line with the filled squares represents a major instability in the kHz range. By impressing a low frequency excitation (see the Line with the filled diamonds), whose frequency at 1.5% of the instability frequency , the high-frequency instability could be suppressed by 39 dB. in this connection only the amplitude of the excitation signal is changed, its frequency remains constant in the case shown in FIG. 2.

Eine zweite Instabilität mit einer etwas kleineren Amplitude im 100 Hz Bereich, siehe die Linie mit den ausgefüllten Kreisen, konnte ebenfalls um etwa 2 dB weiter unterdrückt werden.A second instability with a slightly smaller amplitude in the 100 Hz range, see the line with the filled circles could also be suppressed by about 2 dB become.

Ferner kann beobachtet werden, daß auch die Amplitude der Anregung nur gering ansteigt und noch 5 dB unter dem Pegel der niederfrequenten Instabilität ohne Kontrolle lag und 14 dB unter dem Pegel der hochfrequenten Schwingung. It can also be observed that the amplitude of the excitation is only small increases and still 5 dB below the level of low-frequency instability without control was and 14 dB below the level of the high-frequency vibration.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

11
Brennstoffreservoirfuel reservoir
22
Einspritzdüseinjection
33
Brennerburner
44
Brennkammercombustion chamber
55
Frequenzgeneratorfrequency generator
66
Verstärkereinheitamplifier unit

Claims (7)

Verfahren zur Reduzierung thermoakustischer Schwingungen in einer Strömungskraftmaschinen mit einem Brennersystem, das wenigstens einen Brenner (3) vorsieht, in den über wenigstens eine Brennerdüse (2) Brennstoff eingebracht wird, der mit in den Brenner (3) einströmenden Verbrennungszuluft zu einem Brennstoff/Luftgemisch vermischt wird, das in einer, sich an das Brennersystem anschließenden Brennkammer (4) zur Zündung gebracht wird,
dadurch gekennzeichnet, dass der Brennstoff durch die Brennerdüse (2) in den Brenner (3) gepulst mit variablen oder festen Frequenzen zwischen 1 Hz und 1000 Hz eingebracht wird.Method for reducing thermoacoustic vibrations in a fluid-flow engine with a burner system which provides at least one burner (3) into which fuel is introduced via at least one burner nozzle (2) and which mixes with combustion air flowing into the burner (3) to form a fuel / air mixture which is brought to ignition in a combustion chamber (4) connected to the burner system,
characterized in that the fuel is introduced through the burner nozzle (2) into the burner (3) pulsed at variable or fixed frequencies between 1 Hz and 1000 Hz. Verfahren nach Anspruch 1,
dadurch gekennzeichnet, dass die gepulste Brennstoffzugabe durch die Brennerdüse (2) derart erfolgt, dass sich die Ausbildung des Brennstoff-/Luftgemisch ebenso gepulst erfolgt.Method according to claim 1,
characterized in that the pulsed fuel is added through the burner nozzle (2) such that the fuel / air mixture is also pulsed. Verfahren nach Anspruch 1 oder 2,
dadurch gekennzeichnet, dass die gepulste Brennstoffzugabe unabhängig von sich im Brennersystem ausbildenden thermoakustischen Schwingungen, d.h. in einem "open loop", erfolgt.The method of claim 1 or 2,
characterized in that the pulsed addition of fuel takes place independently of thermoacoustic vibrations which form in the burner system, ie in an "open loop". Verfahren nach Anspruch 1 oder 2,
dadurch gekennzeichnet, dass die gepulste Brennstoffzugabe mit einer Frequenz erfolgt, die etwa bei 1,5 % der Frequenz liegt, mit der sich die thermoakustischen Schwingungen ausbilden. The method of claim 1 or 2,
characterized in that the pulsed fuel is added at a frequency which is approximately 1.5% of the frequency at which the thermoacoustic vibrations form. Verfahren nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet, dass das unmittelbar aus dem Brenner (3) ausströmende Brennstoff-/Luftgemisch im Rahmen einer Vormischstufe möglichst vollständig durchmischt wird, bevor das Gemisch in der Brennkammer (4) gezündet wird.Method according to one of claims 1 to 4,
characterized in that the fuel / air mixture flowing directly out of the burner (3) is mixed as completely as possible in the course of a premixing stage before the mixture is ignited in the combustion chamber (4). Verfahren nach einem der Ansprüche 1 bis 5,
dadurch gekennzeichnet, dass zur Erzeugung des Brennstoff-/Luftgemisches ein Brenner verwendet wird, der aus mindestens zwei hohlen, in Strömungsrichtung des Brennstoff-/Luftgemisches ineinandergeschachtelten Teilkörpern besteht, deren Mittelachsen zueinander versetzt laufen, dergestalt, dass benachbarte Wandungen der Teilkörper tangentiale Lufteintrittskanäle für die Einströmung von Verbrennungsluft in einen von den Teilkörpem vorgegebenen Innenraum bilden, und wobei der Brenner zumindest eine axial angeordnete Brennstoffdüse, durch die der Brennstoff gepulst eingedüst wird, aufweist.Method according to one of claims 1 to 5,
characterized in that a burner is used to generate the fuel / air mixture, which consists of at least two hollow part bodies nested in the flow direction of the fuel / air mixture, the center axes of which are offset from one another, in such a way that adjacent walls of the part body tangential air inlet channels for the Form the inflow of combustion air into an interior space specified by the partial bodies, and wherein the burner has at least one axially arranged fuel nozzle through which the fuel is injected in a pulsed manner. Verfahren nach einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet, dass als Strömungskraftmaschinen Gasturbinenanlagen verwendet werden.Method according to one of claims 1 to 6,
characterized in that gas turbine systems are used as flow engines.
EP01116012A 2000-08-21 2001-07-02 Process for reducing the thermoacoustic oscillations in a turbo-engine using a combustion system Withdrawn EP1182399A3 (en)

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DE10040868A DE10040868A1 (en) 2000-08-21 2000-08-21 Process for reducing thermoacoustic vibrations in fluid-flow machines with a burner system
DE10040868 2000-08-21

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DE10257704A1 (en) * 2002-12-11 2004-07-15 Alstom Technology Ltd Method of burning a fuel
AT504523B1 (en) * 2007-01-04 2008-06-15 Glueck Christoph Ing PROCESS FOR FIRING LIQUID FUELS
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