EP1724527A1 - Combustion chamber and method of suppressing combustion vibrations - Google Patents

Abstract

The combustion chamber (12) has a resonator device for absorbing thermal acoustic oscillations inside the chamber. The resonator has a resonator volume (24) connecting through an opening (26) with the inside of the chamber. An oscillation activator (32) energizes an oscillation in the resonator volume. An independent claim is included for a method of suppressing combustion vibrations, and a gas turbine system.

Description

The present invention relates to a flame space and a method for suppressing combustion vibrations in a flame space.

Flame spaces are spaces in which a combustion process takes place. Examples of such flame chambers are combustion chambers, such as those used in gas turbine plants.

A gas turbine plant is a turbomachine that essentially comprises a compressor section, a turbine section and a burner section with one or more combustion chambers arranged between the turbine section and the compressor section.

During operation of such a gas turbine plant ambient air is sucked through the compressor and compressed to an elevated pressure. The compressed air is supplied to the burner section where it is mixed with a fuel, for example oil or gas, and burned in the combustion chamber (s). The combustion exhaust gas under high pressure due to the combustion is finally supplied as a working medium to the turbine section, where it relaxes and cools, thereby causing the turbine to rotate. In this way, the thermal energy of the combustion is converted into mechanical work, on the one hand for driving the compressor, which is coupled to the turbine via a common shaft, the so-called turbine rotor, as well as for driving a consumer, eg. A generator for generating Electricity, serves.

In the combustion chambers or the combustion chamber, it can lead to the formation of thermoacoustic vibrations in the combustion exhaust gases come. Increased pollutant emissions and vibrations as well as vibrations of the gas turbine plant, in particular the combustion chamber, can be the result.

The suppression of thermoacoustic oscillations can take place, for example, by means of Helmholtz resonators, which reduce the oscillations in their amplitudes or extinguish them completely. A Helmholtz resonator comprises as essential components a resonator volume and a resonator opening, via which the resonator volume communicates with the combustion chamber. As a rule, the opening first leads into a so-called resonator neck, which finally opens into the resonator volume. The air in the resonator neck and in the resonator volume forms a spring-mass system, in which the air in the resonator volume serves as a spring and the air in the resonator neck as a mass. This spring mass system has a resonance frequency which depends on the resonator volume as well as on the length and the area of the resonator neck.

In the ideal case, the resonator acts as a damper by shifting the thermoacoustic oscillation imposed on the resonator opening by the combustion exhaust gases to another frequency. In reality, however, influences such as fluid friction etc. change the effectiveness of the resonators, so that they do not act as sound absorbers, but only as the amplitude reducing absorber. Therefore, reduction is far from being so pronounced that the oscillation can be extinguished. In addition, the effect of Helmholtz resonators is reduced in vibrations that are not in the immediate vicinity of its resonance frequency.

It is therefore an object of the present invention to provide a flame chamber which enables a more effective suppression of thermoacoustic oscillations in the combustion exhaust gases.

Another object of the present invention is to provide an effective method for suppressing thermoacoustic vibrations in a flame room.

The first object is achieved by a flame chamber according to claim 1, the second object by a method for suppressing combustion oscillations in a flame chamber according to claim 7. The dependent claims contain advantageous developments of the invention.

A flame chamber according to the invention is equipped with a resonator device for damping thermoacoustic oscillations in the interior of the flame chamber. The resonator device comprises a resonator volume, a resonator opening connecting the resonator volume to the interior of the flame space, and a vibration exciter for exciting a vibration in the resonator volume. As vibration exciter can here, for example, come to be put in vibration metal plate for use. A resonator neck of the resonator device can be formed either alone by the material surrounding the resonator opening or by an example. Tubular connection between the resonator opening and the resonator volume.

By means of the excitation of a suitable counter-oscillation in resonator volume, the thermoacoustic oscillations in the flame chamber can be suppressed much more effectively than with conventional Helmholtz resonators.

In order to enable the generation of a suitable counter-vibration, a vibration sensor is preferably arranged such that it detects an oscillation of the combustion exhaust gases which is applied to the resonator opening. In this case, it is particularly advantageous to arrange the vibration sensor in the immediate vicinity of the resonator opening.

The vibration sensor is connected via a feedback device with the vibration exciter. The feedback device comprises a delay element and is designed such that that it causes the vibration exciter to excite a vibration which has a time delay with respect to the vibration applied to the resonator opening, ie is phase-shifted. By means of a suitable phase shift, a complete extinction of the voltage applied to the resonator opening vibration can be achieved, provided that the phase shift is adjusted properly and the amplitudes of the two oscillations are the same. With a suitable choice of the phase shift, ie the time delay with which the excited oscillation follows the oscillation applied to the resonator opening, the resonator acts like an ideal resonator, ie complete extinction of the oscillation applied to the resonator opening is possible.

If the feedback device comprises a setting device for adjusting the phase shift, the effect of the resonator device in the flame space can be optimized. In particular, an "online optimization" is possible if the vibration pickup is configured to output a vibration signal representing the detected vibration, the adjusting device is configured to receive a setting signal representing the frequency and / or the amplitude of the vibration to be excited, and one with both the vibration sensor and the vibration sensor Receiving the vibration signal as well as with the setting device for outputting the setting signal connected control unit is present. The control unit is configured such that it determines and outputs a suitable adjustment signal on the basis of the received oscillation signal.

The flame chamber according to the invention is particularly suitable for use as a combustion chamber, for example for a gas turbine plant, and in particular as an annular combustion chamber for a gas turbine plant.

Overall, two properties of the flame chamber according to the invention lead to a suppression of the thermoacoustic oscillations, namely on the one hand the ability to sound amplitudes not only to reduce, but to extinguish and on the other hand, the possibility to regulate the phase shift of the excited vibration with respect to the vibration applied to the resonator opening.

In the method according to the invention for suppressing combustion oscillations in a flame chamber, which can be used in particular in a flame chamber according to the invention, the combustion oscillations are suppressed by exciting a phase-shifted counter-vibration.

The inventive method provides an effective way to reduce combustion oscillations in flame chambers.

FIG 1

zeigt eine Gasturbinenanlage in einer teilweise geschnittenen Seitenansicht.

FIG 2

zeigt einen Ausschnitt aus der Wand der in FIG 1 dargestellten Brennkammer mit einer daran angeordneten Resonatorvorrichtung.

FIG 3

zeigt eine Prinzipskizze für einen konventionellen Helmholtz-Resonator.

Further features, properties and advantages of the present invention will become apparent from the following description of an embodiment with reference to the accompanying figures.

FIG. 1

shows a gas turbine plant in a partially sectioned side view.

FIG. 2

shows a section of the wall of the combustion chamber shown in FIG 1 with a resonator arranged thereon.

FIG. 3

shows a schematic diagram for a conventional Helmholtz resonator.

The gas turbine plant 1 shown in a partially sectioned side view in FIG. 1 comprises a compressor section 3, a turbine section 5 and a combustion chamber section 7. Through the entire installation extends a shaft 8, the so-called turbine rotor, from which turbine blades extend in the radial direction on the one hand compacting blades 4 and on the other hand form turbine blades 6. The turbine rotor 8 is rotatably mounted about a central axis 9 of the gas turbine plant.

In the combustion chamber section 7 of the gas turbine plant, a so-called annular combustion chamber 12 is arranged, which surrounds the turbine rotor 8 in an annular manner. The combustion chamber is equipped with a number of burners 10 distributed along the ring, through which a fuel, for example, oil or natural gas can be supplied to the combustion chamber.

During operation of the gas turbine plant 1, ambient air U is sucked in via the compressor, compressed to a higher pressure, and the compressed air is passed on to the combustion chamber section 7 as so-called compressor air. In the combustor section 7, the compressed air enters the burners 10 and is mixed with the fuel. In the combustion chamber 12, the air-fuel mixture is burned, wherein the resulting combustion exhaust gases form a working fluid A for driving the turbine rotor 8 in the turbine section 5. The rotating turbine rotor then drives on the one hand the compressor in the compressor section 3 and on the other hand a generator, not shown, as a consumer.

The combustion taking place in the combustion chamber 12 can lead to thermoacoustic oscillations, which can lead to damage to the combustion chamber or to increased pollutant content of the combustion exhaust gases if no countermeasures are taken.

In order to effectively suppress the vibrations, the combustion chamber 12 is equipped with a number of resonator devices 20, as shown by way of example in FIG. 2 in a sectional view. The resonator device 20 is arranged on the combustion chamber wall 14 and comprises a resonator chamber 22, which encloses a resonator volume 24, which serves as a resonance volume. The resonator volume 24 communicates with the interior 13 of the combustion chamber 12 via a resonator opening 26. Between the resonator opening 26 and the resonator volume 24 is a so-called resonator neck, which is designed essentially as a narrowed point of the resonator volume 24. In the present In the exemplary embodiment, the resonator neck 25 is formed by a tube 25 arranged between the combustion chamber wall 14 and the resonator chamber 22, the length of which defines the length of the resonator neck. However, the length of the resonator neck can also be given only by the material thickness of the combustion chamber wall 14. In this case, no tube 25 is needed.

The previously described parts of the resonator device 20 essentially correspond to a conventional Helmholtz resonator, which behaves like a spring-mass system. Such a spring-mass system is shown schematically in FIG. In this case, the mass 100 of the spring-mass system is formed by the air mass in the resonator neck 25 and the spring 102 of the spring-mass system by the air in the resonator volume 24. Fluid friction and possibly existing flow resistance form an attenuator 104, which dampens the vibration of the spring-mass system. To vibrate the spring-mass system is excited by a stimulating vibration system 106, which is the vibrating working fluid in the combustion chamber 12 in the present embodiment.

beschreiben, wobei c die Schallgeschwindigkeit, V das Resonatorvolumen 24 der Resonatorkammer 22, L die Länge des Resonatorhalses 25 und S die Querschnittsfläche des Resonatorhalses 25 beschreiben. Ein idealer Helmholtz-Resonator würde als Schwingungstilger fungieren, indem er die an der Resonatoröffnung 26 durch die Verbrennungsabgase aufgeprägte Druckschwingung zu einer anderen Frequenz als der Schwingungsfrequenz in der Brennkammer verschiebt. Aufgrund der Dämpfung 104 lässt sich in der Realität die Schalltilgung jedoch nicht realisieren. Der Helmholtz-Resonator arbeitet daher nicht als Schalltilger, sondern als Schallabsorber, welcher die Schallamplitude lediglich reduziert und bei Weitem nicht auslöscht.The resonant frequency ƒ of a Helmholtz resonator is given by the equation $$f=\frac{c}{2\pi }\sqrt{\frac{S}{LV}}$$

in which c describes the speed of sound, V the resonator volume 24 of the resonator chamber 22, L the length of the resonator neck 25 and S the cross-sectional area of the resonator neck 25. An ideal Helmholtz resonator would function as a vibration absorber by shifting the pressure vibration imposed on the resonator opening 26 by the combustion exhaust gases to a frequency other than the oscillation frequency in the combustion chamber. Due to the damping 104, however, in reality the sound eradication can not be achieved realize. The Helmholtz resonator therefore does not work as a sound absorber, but as a sound absorber, which only reduces the sound amplitude and does not extinguish it by far.

In order to restore the Schalltilgungsfähigkeit of the resonator, the resonator 20 includes a vibration sensor, which is formed in the present embodiment as a change pressure sensor 28. In addition, the wall 30 of the resonator chamber 22 opposite the resonator opening 26 is designed in the form of a metal sheet to be vibrated. The wall 30 can be vibrated by a piezoelectric vibration exciter 32. The vibration imparted to the wall 30 by the vibration exciter is transferred to the gas in the resonator volume 24 so that an oscillation in the resonator volume 24 is impressed on the vibration exciter 32 through the intermediary of the wall 30 leaves. If this impressed oscillation has a suitable frequency and a suitable amplitude, the pressure oscillation applied to the resonator opening 26 can be extinguished.

Preferably, the resonator device is provided with an adjuster 34 for adjusting a phase relationship between the impressed vibration and the applied vibration. The adjuster 34 is connected to the piezoelectric vibrator 32 for outputting a phase signal representing the phase of the vibration to be impressed, and acts as a delay element, causing a time delay between the vibration applied to the resonator opening 26 and the excited vibration. By setting a suitable phase for the oscillation to be excited, the resonator device can in principle be adapted to the oscillation present at the resonator opening 26 in such a way that a complete eradication of the adjacent oscillation becomes possible. The detection of the voltage applied to the resonator opening 26 pressure oscillation takes place by means of the alternating pressure sensor 28, the one the amplitude and the frequency outputs the signal representative of the applied pressure oscillation.

In the present exemplary embodiment, the signal output by the alternating pressure sensor 28 is output to a control unit 36 which, based on a control law, determines a setting signal which it outputs to the setting device 34 and which represents the phase to be set, the frequency to be set and the amplitude of the oscillation to be set , The corresponding phase, amplitude and frequency is finally transmitted by the adjusting device 34 to the piezoelectric vibration exciter 32, so that it stimulates the wall 30 to a corresponding vibration.

The feedback loop described makes it possible to react online to changes in the pressure oscillation inside the combustion chamber 12, so that at any time a suitable phase-shifted counter-oscillation can be generated by means of the piezoelectric vibration exciter 32 so that the pressure oscillation is largely eradicated. Due to the possibility of regulating the phase shift between the recorded oscillation and the oscillation to be excited, the resonator device according to the invention can be adjusted over wide ranges.

Claims (9)

A flame chamber (12) having a resonator device for damping thermoacoustic oscillations inside the flame chamber (12), in which the resonator device comprises: a resonator volume (24), - A Resonatoröffnung (26) connecting the resonator volume (24) with the interior of the flame chamber (12) and - A vibration exciter (32) for exciting a vibration in the resonator (24). Flame space (12) according to claim 1,
marked by - A vibration sensor (28) which is arranged such that it detects a voltage applied to the resonator opening (26) vibration, and - a feedback device (34, 36) connecting the vibration sensor (28) to the vibration exciter (32) and comprising a delay element (34) configured to apply the vibration exciter (32) for exciting a vibration in the resonator volume (24). which is phase-shifted with respect to the vibration applied to the resonator opening (26). Flame space (12) according to claim 2,
characterized in that the delay element comprises an adjusting device (34) for adjusting the phase shift of the excited oscillation with respect to the vibration applied to the resonator opening. Flame space (12) according to claim 3,
characterized in that - The vibration sensor (28) is configured to output a vibration signal representing the detected vibration, - The setting means (34) for receiving a phase of the oscillation to be excited setting signal is configured and there is provided a control unit (36) connected to the vibration pickup (28) for receiving the vibration signal and to the adjusting means (34) for outputting the adjustment signal, which is arranged to determine and output a tuning signal based on the vibration signal represents a phase to be set by the adjusting device (34) with respect to the detected oscillation and / or an amplitude to be set and / or a frequency of the oscillation to be set. Flame chamber (12) according to any one of the preceding claims, characterized in that as a vibration exciter to be set in vibration metal plate is used. Flame chamber (12) according to one of the preceding claims, characterized by its design as a combustion chamber. Flame space (12) according to claim 5,
characterized by its design as an annular combustion chamber. Gas turbine plant with a flame chamber (12) according to one of the preceding claims. Method for suppressing combustion oscillations in a combustion chamber (12), in particular in a combustion chamber according to one of the preceding claims, in which combustion vibrations are suppressed by exciting a phase-shifted counter-vibration.

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