This application claims priority to EP Application No. 14194660.7 filed Dec. 1, 2014, the contents of which are hereby incorporated in its entirety.
The present invention relates to the field of combustion technology. It refers to a Helmholtz damper according to the preamble of claim 1.
It further refers to a gas turbine with such a Helmholtz damper.
with the speed of sound c, and the area AN and length LN of neck tube 22.
This means, that
When Helmholtz damper 20 is attached to the combustor 15 of gas turbine 10 of
Further, it is known that the frequency of the pulsations within the combustor depends on the operation mode of the gas turbine. Especially, there is a change in pulsation frequency fP, when the gas turbine changes from part load operation to base load operation, and vice versa. For a gas turbine of the type shown in
To maintain the maximum damping properties of Helmholtz dampers used with such gas turbine, the resonance frequency of the dampers should stay tuned to the pulsation frequency even if the load conditions of the gas turbine change. According to the formula given above, the damper volume V should be changed in accordance with a change in the load conditions.
In the prior art, there are solutions described on closed loop volume adjustments in Helmholtz dampers by moving pistons. This, however, is not a solution for an actual engine due to high costs of control device (loop), stepping motor, and manufacturing tolerance of piston.
Another existing solution is to simply place more dampers that are tuned to different frequencies.
Some of the known solutions are cited below:
Document EP 2 397 761 A1 discloses a Helmholtz damper and a method for regulating the resonance frequency of a Helmholtz damper. In particular, it refers to Helmholtz dampers to be connected to lean premixed, low emission combustion systems of gas turbines, whereby said Helmholtz damper comprises an enclosure from which a neck extends, and a pipe is inserted into and fits the neck. Especially, an actuator is connected to the pipe to adjust its portion inserted into the neck.
Document EP 2 397 760 A1 discloses a damper arrangement that has a first Helmholtz damper connected in series to a second Helmholtz damper. The resonance frequency of the first Helmholtz damper and the resonance frequency of the second Helmholtz damper are shifted from one another in an amount producing a synergic damping effect.
Document DE 100 26 121 A1 describes an apparatus for damping acoustic vibrations in a combustor as well as a corresponding combustor arrangement with the apparatus. The apparatus comprises a Helmholtz resonator that can be connected via a connecting channel with a combustor. The Helmholtz resonator contains a hollow body the volume of which can be changed by adding or draining a fluid via a supply line, or is located adjacent to such a hollow body in such a way that the resonance volume of the Helmholtz resonator is changed when the volume of the hollow body is changed. This apparatus makes it possible to adjust the resonance frequency of a Helmholtz resonator arranged inside a pressure container in accordance with the respective current operating point of the combustor to be damped, without having to pass movable components through the pressure container.
Document U.S. Pat. No. 8,661,822 B2 discloses a system with a turbine engine, comprising: a compressor; a turbine; a combustor disposed downstream from the compressor and upstream from the turbine; a fluid injection system configured to inject one or more fluids into the combustor; a variable geometry resonator coupled to the fluid injection system; and a controller configured to tune the variable geometry resonator in response to feedback.
However, the problem with all these solutions is that they increase costs on the one hand and often are not possible at all to apply due to limited space to put dampers inside an engine.
It is an object of the present invention to provide a Helmholtz damper, which is simple in construction, requires minimum space and has a self-adjusting capability.
It is another object of the invention to provide a Helmholtz damper with a design that allows an adjustment of the damper volume in a way that is applicable to the combustor environment inside an engine and fulfils requirements of robustness and costs.
It is a further object of the invention to provide a gas turbine with such a Helmholtz damper.
These and other objects are obtained by a Helmholtz damper according to Claim 1 and a gas turbine according to Claim 8.
The Helmholtz damper according to the invention, which is especially suitable for damping pulsations in a combustor of a gas turbine, comprises a damper volume, which can be connected to a damped space by means of a neck tube, and further comprises a piston, which is moveable within said damper volume and divides said damper volume into a variable first part on one side of said piston, which variable first part is connected to said neck tube, and a correspondingly variable second part on the other side of said piston. It is characterized in that said piston is driven by a pressure drop between said first and second part of said damper volume.
An embodiment of the Helmholtz damper according to the invention is characterized in that the piston is held in an idle position, where the first part of said damper volume is a maximum, by means of a spring, and that said pressure drop drives said piston against the force of said spring.
Specifically, said spring is arranged within said first part of said damper volume.
Alternatively, said spring may be arranged outside of said damper volume and acts on said piston via a piston rod, which extends from said piston to the outside of said damper volume.
Specifically, said spring is a helical spring.
Another embodiment of the Helmholtz damper according to the invention is characterized in that said second part of said damper volume is in fluidic connection with the outside of said damper volume.
Specifically, said damper volume is enclosed by a housing, and said fluidic connection is established by at least one opening in said housing.
The gas turbine according to the invention comprises a compressor, at least one combustor and a turbine, whereby said at least one combustor is enclosed by a combustor casing, the outside of which is exposed to the compressor outlet pressure of said compressor, whereby at least one Helmholtz damper is provided at and connected to one combustor in order to damp pulsations within said combustor. It is characterized in that said at least one Helmholtz damper is a Helmholtz damper according to the invention, and that a pressure drop between said compressor outlet pressure and the pressure within said combustor is used to drive said piston of said at least one Helmholtz damper.
An embodiment of the gas turbine according to the invention is characterized in that said at least one Helmholtz damper is attached to the combustor casing by adaptation means.
Specifically, said at least one Helmholtz damper is connected to said combustor through a hole in said combustor casing, and said adaptation means comprises an insert, which fits into said hole and receives a neck tube of said at least one Helmholtz damper such that said neck tube passes through said insert to open out into said combustor.
More specifically, a neck tube adapter is provided to seal said neck tube against said insert.
Especially, said neck tube is releasably connected to the damper volume of said at least one Helmholtz damper.
Another embodiment of the gas turbine according to the invention is characterized in that said combustor is of an annular configuration, and that a plurality of Helmholtz dampers are circumferentially arranged around said combustor.
The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.
As has been said before, the pulsation frequency in gas turbine combustors usually increases with relative load. A damper that is optimized for part load operation consequently does not exhibit its maximum damping performance at base load and vice versa.
The idea of this invention is to make use of the relative pressure drop Δp between compressor plenum and combustion chamber that also increases with relative load RLGT.
The invention seeks to explore this fact in such a way that the volume V of the damper is reduced so that its resonance frequency is continuously adjusted in order to provide highest damping at the required frequency. This is possible due to the fact that the outside of the damper volume is exposed the compressor outlet pressure pk2, whereas the pressure inside the damper is very close to that of the combustion chamber.
The Helmholtz damper 24 according to
When Helmholtz damper 24 is in its starting position (
A more compact design of a Helmholtz damper according to the invention, which is more suitable for being applied to a gas turbine combustor 33, is shown in
Helmholtz damper 38 of
Piston 44, which has an orifice 47 for cooling purposes, is designed as a free piston. A balancing helical spring 45 is arranged within the damper volume 40. This configuration with a free piston and an internal balancing spring is on one hand very compact, requiring only minimal space, and on the other hand is protected against impacts from outside.
The embodiment of
Number | Date | Country | Kind |
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14195660.7 | Dec 2014 | EP | regional |