EP1605209B1 - Combustor with thermo-acoustic vibrations dampening device - Google Patents

Description

The present invention relates to a combustion chamber with a damping device for damping thermoacoustic oscillations, in particular for a gas turbine, and a gas turbine with such a combustion chamber.

A gas turbine plant comprises e.g. a compressor, a combustion chamber and a turbine. In the compressor there is a compression of sucked air, which is then admixed with a fuel. In the combustion chamber, the mixture is burned, the combustion exhaust gases are supplied to the turbine. From the turbine thermal energy is extracted from the combustion exhaust gases and converted into mechanical energy.

In order to permanently ensure the functional reliability of the combustion chamber at the high temperatures prevailing during the combustion process, a number of elements of the combustion chamber are cooled with a cooling mass flow of cooling air. The cooling air also serves to block openings, for example gaps between two adjoining heat shield elements of a combustion chamber, i. for preventing hot gas from the combustion chamber from entering the opening. As a result, the air supply to the burner is reduced and the emission of pollutants, such as nitrogen oxides, increases.

In order to reduce the pollutant emissions of gas turbines, the cooling mass flow is reduced in modern systems. This also reduces the acoustic damping, so that thermoacoustic vibrations can increase. This can lead to a swirling interaction between thermal and acoustic disturbances, which can cause high loads on the combustion chamber and, in turn, rising emissions.

In addition, fluctuations in fuel quality and other thermal or acoustic disturbances lead to fluctuations in the amount of heat released and thus the thermodynamic performance of the system. There is an interaction of acoustic and thermal disturbances, which can oscillate. Such thermoacoustic oscillations in the combustors of gas turbines - or turbomachines in general - present a problem in the design and operation of new combustors, combustor parts and burners for such gas turbines.

For reducing thermoacoustic vibrations, therefore, in the prior art e.g. Helmholtz resonators used to dampen the vibrations. A Helmholtz resonator typically includes a volume of air or other gas therein. The volume is followed by a tube, the so-called resonator tube, which also contains air or gas and which opens into the combustion chamber. The air or the gas in the volume and in the resonator tube form a spring-mass system, wherein the air or the gas in the volume of the spring and the air or the gas in the resonator tube forms the mass. When the spring-mass system oscillates at a resonant frequency determined by the volume, the cross-sectional area of the resonator tube and the length of the resonator tube, the Helmholtz resonator behaves like an infinite-length aperture which prevents a standing wave can form with the resonance frequency. The emergence of thermoacoustic oscillations, which are substantially standing waves, can thus be effectively suppressed for frequencies corresponding to or near the resonant frequency of the Helmholtz resonator.

The US 6,351,947 Bl shows a combustion chamber with such Helmholtz resonators.

However, the mouths open to the combustion chamber Helmholtz resonators require additional sealing air, whereby the combustion temperature is increased again. As a result of this Increases increase the proportion of nitrogen oxides in the combustion exhaust gases.

It is therefore the object of the present invention to provide an improved combustion chamber with a damping device, in particular for a gas turbine.

It is another object of the present invention to provide an improved gas turbine.

According to the first object is achieved by a combustion chamber according to claim 1, the second object by a gas turbine according to claim 11. The dependent claims contain advantageous developments of the invention.

A combustion chamber according to the invention comprises at least one combustion chamber element to be cooled and at least one damping device for damping thermoacoustic oscillations with an opening open towards the combustion chamber. It is characterized by the fact that the mouth is integrated into the combustion chamber element to be cooled.

Characterized in that the damping device is integrated in a combustion chamber element to be cooled, the amount of air entering the combustion chamber increases only slightly, if at all, due to the presence of the damping element. This results from the fact that for cooling the combustion chamber element alone anyway a cooling air flow is necessary, which now also serves to lock the mouth of the damping device at the same time. The combustion temperature - and thus the pollution of the combustion gases - is therefore not or only slightly increased.

For supplying the sealing air, the mouth in the combustion chamber according to the invention may be associated with a blocking air supply. This then serves as a cooling air supply for the cooling of the combustor element to be cooled. In a Advantageous development of the mouth can also be associated with a fuel supply such that the sealing air fuel is added. The addition of fuel to the sealing air leads to a reduction of the combustion temperature in the main burner and thus to a reduction of the pollutant content of the combustion gases.

The combustion chamber has a combustion chamber wall which comprises a combustion chamber shell and a combustion chamber lining fastened to the combustion chamber shell by means of fastening elements to be cooled. The combustion chamber lining may, for example, be a heat shield, in particular a ceramic or metallic heat shield. The mouth of the at least one damping device is integrated in a fastening element for fastening the combustion chamber lining to the combustion chamber shell. In other words, in the invention, the combustor element to be cooled is formed as a fastener for fixing the combustor liner. Since the fasteners are present anyway and require cooling, integrating the mouth in a fastener requires only a redesign of the fastener, for example. By fastening screws are provided with an axial bore or other axial passage opening so that they can serve as the mouth of the damping element , Further conversions of the interior of the combustion chamber are not necessary in this embodiment. Except as a fastening screw, the fastening element can also be configured as a fastening element, which comprises at least one sliding seat device. A sliding seat device is often located, for example, at the transition from the so-called "basket" to the so-called "transition piece" in a silo burning chamber. Except at the transition from the "Basket" to the "Transitionpiece" the damping device can also be arranged at the transition from the combustion chamber to the first row Leitschauffelreihe. As a rule, quite high blocking air flows are needed there. This applies to ring combustion chambers and also for silo separation chambers.

In the combustion chamber according to the invention, the damping element may in particular be designed such that the combustion chamber element to be cooled forms part of the damping device. For example. For example, a fixing screw with an axial through-bore can form the resonator tube of a Helmholtz resonator.

In one embodiment of the invention, the damping device is designed as a Helmholtz resonator, in particular as a Helmholtz resonator with variable resonance frequency. For example, the variability of the resonant frequency can be achieved by making the volume of the Helmholtz resonator changeable. A volume change may e.g. can be achieved via an adjustable rear wall of the resonator.

The Helmholtz resonator may also include a plurality of orifices, each of which is integrated into a combustion chamber element to be cooled. For example. For example, a plurality of resonator tubes of the same Helmholtz resonator can be integrated into different fastening screws.

In an alternative embodiment of the invention, the damping device is designed as a λ / 4 tube, ie as a tube with a quarter of the wavelength of the vibration to be damped.

A gas turbine according to the invention comprises at least one combustion chamber according to the invention.

Although the invention is described herein in its entirety with respect to combustion chambers of gas turbines, the use is not limited to gas turbines. It is also possible to use the invention in other turbines and turbomachines or in combustion chambers in general.

Further features, characteristics and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings.

Fig. 1 shows as a first embodiment, a section of the combustion chamber wall of a combustion chamber according to the invention in a highly schematic representation.

Fig. 2 shows a view of the combustion chamber wall of a second embodiment of the invention seen from the combustion chamber inside.

Fig. 3 shows a side view of in Fig. 2 shown Brennkammerwandung.

In FIG. 1 is shown as a first embodiment of the invention, a combustion chamber of a gas turbine according to the invention. The figure shows a section of the combustion chamber wall 1, which comprises a combustion chamber shell 3 and a metallic heat shield 4. The metallic heat shield 4 is constructed from a number of heat shield elements 2, which are each fixed by means of a screw 7 as a fastening element at a connection point 5 on the combustion chamber shell 3. The screws 7 are like the heat shield elements 2 by means of cooling air to be cooled combustion chamber elements.

For damping of acoustic oscillations in the combustion chamber, this is equipped with at least one damping device, which is formed in the present embodiment as opening into the combustion chamber Helmholtz resonator 6. The Helmholtz resonator 6 is attached to the combustion chamber wall 1 in the region of a connection point 5. It is held by means of a fastening element or a plurality of fastening elements (not shown) on the combustion chamber wall 1. In an alternative embodiment, it is also possible to mount the Helmholtz resonator 6 by means of the screw 7 the combustion chamber wall 1 to keep. In this case, the screw 7 then serves both for holding the heat shield element 2 and for holding the Helmholtz resonator 6, so that an additional fastening element for holding the Helmholtz resonator 6 is not necessary.

In the present embodiment, further attached to joints 5 damping devices may be present.

The Helmholtz resonator 6 comprises a resonator chamber 15 and a resonator tube, also called resonator neck. The resonator tube is formed in the present embodiment of the screw 7, which has a through hole 8 for this purpose. One end 9 of the through hole 8 opens into the resonator 15. The other end 10 of the through hole 8 opens into the combustion chamber and represents the mouth of the Helmholtz resonator 6 in the combustion chamber. The damping effect of the Helmholtz resonator 6 is based on that the behaves in the resonator 15 and the resonator tube 8 located air as a spring-mass system. In this case, the air in the resonator chamber 15, the spring and the air in the resonator tube 8 is the mass of this system. When this spring-mass system oscillates at a resonant frequency, by the volume V of the resonator 15, the cross-sectional area F of the through hole. 8 , And by the length L of the through hole 8 (ie, the screw 7) is determined, the Helmholtz resonator 6 behaves like an opening of infinite length, so that no standing wave can form with the resonance frequency. The generation of thermoacoustic oscillations, which are substantially standing waves, can thus be effectively suppressed for frequencies corresponding to or near the resonant frequency of the Helmholtz resonator.

In the illustrated embodiment, the resonator 6 is designed substantially cylindrically symmetrical to the screw 7.

However, embodiments are also possible which have no symmetry.

By adjusting the length L of the screw 7 and the height H, with which the screw 7 projects into the resonator 15, and / or the cross-sectional area F of the through hole 8 and / or the volume V of the resonator 15, the resonance frequency of the Helmholtz resonator 6 are set. For example, Increasing the volume V of the resonator chamber 15 or the length L of the screw 7 leads to a reduced resonance frequency. Increasing the cross-sectional area F of the through-hole 8, on the other hand, leads to an increased resonance frequency.

To adjust the resonant frequency of the Helmholtz resonator, various approaches are possible.

To change the volume V of the resonator chamber 15, for example, the rear wall 17 of the Helmholtz resonator 6 can be designed to be adjustable. On the cylindrical side wall 12 of the Helmholtz resonator 6 then, for example, a thread 16 is present, in which a matching mating thread of the rear wall 17 engages. By turning the rear wall 17, which can also be done automatically via an electric motor, not shown, the volume V of the resonator 15 and thus the resonator frequency can be changed in the desired manner. However, it is also possible to change the volume by exchanging the resonator chamber 15 with a resonator chamber 15 having a different volume.

In addition, by changing the screw 7, the length L of the screw and / or the cross-sectional area F of the through-hole 8 can be changed. For example, in order to increase the resonance frequency, a screw 7 can be used whose bore 8 has a larger cross-sectional area F than the previously used screw 7. It can be used for the same purpose but also a screw 7 with a shorter length L. become. Also, by adjusting the height H, with which the screw 7 projects into the resonator 15, by means of the choice of a suitable screw 7, the resonance frequency of the Helmholtz resonator 6 can be influenced.

In the present embodiment, the resonator space 15 is at the cold side, i. attached to the combustion chamber facing away from the outside of the combustion chamber shell 3 and projects into the Kompressplplenum 20 inside. In order to enable an air supply for an impingement cooling of the heat shield elements 2, spacers 19 are provided between the resonator chamber 15 and the outside of the combustion chamber shell 3, which ensure a distance between the combustion chamber shell 3 and the resonator chamber 15 and thus a flow of pressurized cooling air between allow the combustion chamber shell 3 and the resonator 15. Cooling air can then be conducted from the compressor plenum 20 along the flow paths 13 to the side facing away from the combustion chamber interior, the so-called cold side of the heat shield elements 2, where it provides for an impingement air cooling of the heat shield elements 2. The impingement air flows into the combustion chamber after hitting the cold sides along the flow paths 23 through gaps between adjacent heat shield elements 2, blocking the gaps against hot gas penetration of the combustion chamber.

The cooling of the screw 7 takes place together with the locking of the mouth 10 of the Helmholtz resonator 6 against ingress of hot gas. The air first flows from the compressor plenum 20 through the openings 18 (forming the blocking air supply) in the rear wall 17 of the resonator chamber 15 into the resonator chamber 15 and then through the through-hole 8 of the screw 7 into the combustion chamber (flow path 11). Characterized that the cooling of Helmholtz resonator 6 and screw 7 is carried out with the same cooling air, the proportion of cooling air, which is guided past the burner, compared to a separate cooling of Helmholtz resonator 6 and screw 7, as necessary would be if the screw 7 was not used at the same time as Resonatorrohr be reduced.

In FIGS. 2 and 3 a second embodiment is shown very schematically. The same or similar components are provided with the same reference numerals as in the first embodiment for simplicity and for better comparability.

In Fig. 2 shows, seen from the combustion chamber inside, a section of a combustion chamber 1, which is lined with metallic heat shield plates 21, 22 as heat shield elements. Fig. 3 shows a section through the combustion chamber wall 1 along the line A - A.

The heat shield plates 21, 22 are screwed to connecting points 5 by means of screws 7 with the combustion chamber shell 3. At the connection points 5 Helmholtz resonators 6 are arranged, which are fixed by means of screws 7 on the combustion chamber 1. A passage opening or through-bore 8 in the screws 7 serves, as in the first exemplary embodiment, as a resonator tube of the respective Helmholtz resonator 6. For the sake of simplicity, FIG FIG. 3 only one of the Helmholtz resonators 6 shown.

In a modification of the second embodiment, it is also possible for a resonator chamber 15 to expand over a plurality of screws 7. In this case, all screws 7, over which the resonator chamber 15 extends, can be provided with through-holes and thus form resonator tubes. Alternatively, it is also possible to provide only a few or even only one of the screws 7, over which the resonator chamber 15 extends, with a through-hole 8. The remaining screws 7 then serve only as fastening screws for the heat shield plates or for the heat shield plates 21, 22 and the Helmholtz resonator.

In the described embodiments, the adjustment of the resonator volume can be done within operating pauses by means of a suitable tool by hand or during operation. In an advantageous embodiment, a controller (not shown) is provided, by means of which the adjustment of the resonator volume can be controlled. An automatic adjustment or regulation is possible. For example, an electric motor, a hydraulic adjusting device or a pneumatic adjusting device can be used. By a controlled automatic adjustment of the effort for subsequent adjustment of the resonator frequency is kept particularly low. The regulation can be done online during operation. With a fully automatic control can take place a continuous or at intervals, adjustment to the strongest vibration frequency. By appropriate adaptation of the resonator 6, it is possible to adapt to changed conditions, e.g. an altered fuel composition, reacts and an adjustment of the resonant frequency are performed. The simple adjustability is particularly advantageous in the prototype testing and also during the commissioning of a gas turbine. A significant advantage of the ease of adjustability results not only from the operation with different fuels, but also under widely varying operating conditions, e.g. due to significant changes in the ambient temperature.

In the described embodiments, a Helmholtz resonator 6 can be switched off by replacing the screw with through hole against a screw without through hole. Alternatively, the resonator 6 can also be completely removed.

Instead of the described Helmholtz resonators, other damping devices, for example. Λ / 4 tubes can be used.

The invention is particularly suitable for use in annular combustion chambers with metallic heat shields or in the so-called inlet shells of the combustion chambers with ceramic heat shields ("stones").

Claims (11)

1. Combustion chamber, in particular for a gas turbine, with at least one fastening element (7) to be cooled and with at least one damping device (6) for the damping of thermoacoustic vibrations, having a mouth (10) open towards the combustion chamber, the mouth (10) being integrated into the fastening element (7) to be cooled, so that, in order to cool the fastening element, all that is necessary is only a cooling-air stream which serves at the same time also for shutting off the mouth of the damping device, characterized in that the combustion chamber comprises a combustion-chamber wall (1) which comprises a combustion-chamber shell (3) and a combustion-chamber lining (4) fastened to the combustion-chamber shell (3) by means of fastening elements (7) to be cooled, so that the mouth (10) of the at least one damping device (6) is integrated into a fastening element (7) for fastening the combustion-chamber lining (4) to the combustion-chamber shell (3).
2. Combustion chamber according to Claim 1, characterized in that the mouth (10) is assigned a shut-off air supply (18) for the supply of shut-off air shutting off the mouth (10) against the ingress of hot gas from the combustion chamber.
3. Combustion chamber according to Claim 2, characterized in that, moreover, the mouth (10) is assigned a fuel supply in such a way that fuel is admixed to the shut-off air.
4. Combustion chamber according to one of the preceding claims, characterized in that the fastening element is a fastening screw (7).
5. Combustion chamber according to one of the preceding claims, characterized in that the fastening element comprises at least one sliding-seat device.
6. Combustion chamber according to one of the preceding claims, characterized in that the combustion-chamber lining is a heat shield (4).
7. Combustion chamber according to one of the preceding claims, characterized in that the damping device is designed as a Helmholtz resonator (6).
8. Combustion chamber according to Claim 7, characterized in that the Helmholtz resonator (6) is configured as a Helmholtz resonator with a variable resonant frequency.
9. Combustion chamber according to Claim 7 or Claim 8, characterized in that the Helmholtz resonator (6) comprises a plurality of mouths (10) towards the combustion chamber, which are integrated in each case into a fastening element (7) to be cooled.
10. Combustion chamber according to one of Claims 1 to 6, characterized in that at least one damping device is designed as a quarter-wave tube.
11. Gas turbine having at least one combustion chamber according to one of the preceding claims.

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