HELMHOLTZ DAMPER FOR A GAS TURBINE AND GAS TURBINE WITH SUCH HELMHOLTZ DAMPER

Abstract

A Helmholtz damper for a gas turbine is disclosed which includes a static resonator volume, which can be connected via a neck to an inner space of the gas turbine to damp pressure pulsations developing in the inner space. The static resonator volume can be changed in order to match resonances of the Helmholtz damper with the pressure pulsations. A simple and effective self-adjustment can be achieved via volume changing by at least one first element, which is exposed to a varying temperature within the gas turbine and undergoes a deformation, which depends on the varying temperature.

Claims

1. Helmholtz damper (HD3-HD5) for a gas turbine (GT1-GT3), comprising: a static resonator volume, configured to be connected via a neck to an inner space of said a gas turbine (GT1-GT3) to damp pressure pulsations developing in said inner space, and means for changing said static resonator volume in order to match resonances of said Helmholtz damper (HD3-HD5) with said pressure pulsations, wherein a volume changing means includes at least one first element configured for exposure to a varying temperature (T.sub.p) within the gas turbine (GT1-GT3) and for undergoing a deformation, which depends on said varying temperature (T.sub.p).

2. Helmholtz damper as claimed in claim 1, wherein said at least one first element is made of a bi-metal and/or shape memory alloy (SMA).

3. Helmholtz damper as claimed in claim 2, wherein said at least one first element is a wall that confines said static resonator volume, such that said static resonator volume will change when said at least one first element undergoes a deformation.

4. Helmholtz damper as claimed in claim 2, wherein said at least one first element acts on a movable second element that confines said static resonator volume, such that said static resonator volume will change when said at least one first element undergoes a deformation.

5. Helmholtz damper as claimed in claim 4, wherein said movable second element is a piston, and said at least one first element is a spring arranged for acting on said piston.

6. A gas turbine (GT1-GT3) comprising: a compressor; a combustor; and a turbine, wherein at least one Helmholtz damper (HD3-HD5) according to claim 1 is provided in said gas turbine (GT1-GT3).

7. Gas turbine as claimed in claim 6, wherein said at least one Helmholtz damper is configured to be exposed to a varying temperature (T.sub.p) of compressed air coming from said compressor.

8. Gas turbine as claimed in claim 6, wherein said combustor has a combustor cavity, and said at least one Helmholtz damper is connected with its neck to said combustor cavity.

9. Gas turbine as claimed in claim 6, wherein said gas turbine comprises: an exhaust duct for exhaust gas leaving said turbine, and said at least one Helmholtz damper is connected with its neck to said exhaust duct.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.

[0041] FIG. 1 shows a perspective view of an industrial GT engine equipped with a combustor of the silo type;

[0042] FIG. 2 shows experimental acoustic pulsation spectrums at two measuring points close to the burner (curve a) and close to the combustor exit (curve b);

[0043] FIG. 3 shows a schematic diagram of a Helmholtz resonator with a piston system for adjusting the eigenfrequency f.sub.H by axial displacement L.sub.H with respect to variable combustor resonance frequency f.sub.c;

[0044] FIG. 4 shows the acoustic resonance (peak) in the frequency dependence of the pressure amplitudes without (curve c) and with (curve d) Helmholtz resonator;

[0045] FIG. 5 shows the frequency sensitivity of the acoustic resonances in terms of temperature T in a cylindrical cavity

[0046] FIG. 6 shows a sketch of an arrangement of a Helmholtz damper in a combustor of a gas turbine, where T.sub.P and T.sub.f denote the plenum and flame temperature, respectively;

[0047] FIG. 7 shows a sketch of a Helmholtz damper with its characteristic temperatures T.sub.P (T.sub.compressed air) and T.sub.hot gas, of the compressed air and hot gases in the combustor;

[0048] FIG. 8 shows the temperature characteristic of the compressed air T.sub.P and hot-gas T.sub.hot gas in the combustor with respect to engine loading in a gas turbine (GT);

[0049] FIG. 9 shows deformations of the systems made of the bi-metallic (dashed curve f) and shape memory alloy (curves e) with respect to temperature T, where T.sub.R denotes the reference compressed air temperature at part load, T.sub.b is the compressed air temperature at the base-load of a GT engine, and PLO denotes

[0050] FIG. 10 shows an example of the application of a bi-metallic element as a wall for adjusting Helmholtz volume V.sub.0 in terms of temperature T varying between part load T.sub.part and base load T.sub.b, where PLO denotes the temperature range of part load operation;

[0051] FIG. 11 shows a Helmholtz damper according to an embodiment of the invention with a helical spring made of a shape memory alloy;

[0052] FIG. 12 shows a Helmholtz damper according to another embodiment of the invention, whereby a side wall of the Helmholtz damper is made of a bi-metallic, in the non-deformed state (a) and in the deformed state (b); and

[0053] FIG. 13 shows a GT exhaust system with a Helmholtz resonator according to the invention made of a bi-metallic or/and shape memory alloy with self-adjusting damping characteristics in terms of the exhaust gas temperature T.sub.after turbine.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS OF THE INVENTION

[0054] According to the present invention a Helmholtz resonator or Helmholtz damper comprises sub-parts that are made of bi-metallic and/or shape memory alloys. Dependent on the temperatures of compressed air T.sub.p in part load or base load, these materials change their deformations due to thermal expansions. Their behaviours are shown in FIG. 9. Deformations of the bi-metallic system are a linear function in terms of temperature T (dashed curve f). The shape memory alloy demonstrates binary or kind of switching behaviour of the deformation with the typical pseudo elastic-plastic hysteresis, as illustrated with solid curves e in FIG. 9.

[0055] In case of the continuous adjustment of the Helmholtz parameters, the bi-metallic system is applied to the resonator (linear curve f). For variable ambient conditions, e.g. between night and day, the Helmholtz resonator adjusts itself following the surrounding temperature T.sub.p which varies in accordance with T.sub.part and T.sub.b as illustrated in FIG. 10.

[0056] Different designs made of the bi-metallic systems and/or shape memory alloys in combination with ordinary metals may be used within the scope of the present invention. Moreover, all known or new developed bi-metallic or/and shape memory alloys of various shapes and fixations may be used. The proposed bi-metallic systems are made of arbitrary metals that are available on market or can be developed in accordance with particular design reasons. Possible applications of the shape memory alloy or/and bimetallic in the Helmholtz damper design are demonstrated in FIG. 11 and FIG. 12.

[0057] In FIG. 11 the Helmholtz damper HD3 comprises a static resonator volume 17, which is connected to a combustor cavity 15 of the gas turbine by neck 16 of fixed length L.sub.0 and fixed diameter. Static resonator volume 17 is confined by a piston-cylinder arrangement with a piston 18 being movable in axial direction. With piston 18 being moved the axial length L.sub.H of the static resonator volume 17 may be changed by a value L.sub.H. Piston 18 is coupled with a spring or springs 25 made of a shape memory alloy (SMA). Spring 25 is exposed to the temperature of the compressed air in the plenum surrounding Helmholtz damper HD2. When this temperature changes, spring 25 changes its length thereby changing the static resonant volume 17.

[0058] Another embodiment of the invention using a bi-metal element is shown in FIG. 12. A bimetallic wall 27 is fixed at its edges by means of a mechanical fixation 26 to ordinary metal 28. In FIG. 12(a) bi-metallic wall 27 is not deformed as the surrounding temperature is the compressed air temperature at part-load, T.sub.part. In FIG. 12(b) wall 27 is at compressed air temperature at base-load, T.sub.b, which leads to a substantial (concave) deformation reducing the static resonator volume 17.

[0059] The described phenomena could be applied to various Helmholtz resonators applied to other engines in that the noise or/and acoustic pulsation need to be suppressed.

[0060] The range of temperature can be then determined in terms of the design point of the engine of interest and the self-adjusting Helmholtz resonator operates within the defined off-design points.

[0061] Another application of this invention could be that the Helmholtz damper (HD5 in FIG. 13) is placed in the exhaust duct 29 of the gas turbine GT3 in order to damp pulsation in the exhaust gas of the gas turbine (FIG. 13). With a changing exhaust gas temperature between the part- and base-load Helmholtz resonator HD5 adapts itself to different frequencies.

[0062] The present invention replaces entirely the manual adjusting of the system with a passive self-adjusting mechanism depending on the temperatures in the plenum and combustor.

[0063] The innovation can be extended onto other sub-systems of a GTCC, like an exhaust system.

LIST OF REFERENCE NUMERALS

[0064] 10 casing [0065] 11 rotor [0066] 12 compressor [0067] 13 turbine [0068] 14 combustor (silo) [0069] 15 combustor cavity [0070] 16 neck [0071] 17 static resonator volume [0072] 18 piston [0073] 19 air flow [0074] 20 compressor [0075] 21 burner [0076] 22 combustor [0077] 23 turbine [0078] 24 exhaust gas [0079] 25 spring [0080] 26 fixation (mechanical) [0081] 27 bi-metallic wall [0082] 28 ordinary metal [0083] 29 exhaust duct [0084] A cross-sectional area (neck) [0085] a-g curve [0086] GT1-GT3 gas turbine [0087] HD1-HD4 Helmholtz damper (resonator) [0088] L.sub.0 length (neck) [0089] L.sub.H length (Helmholtz cavity) [0090] L.sub.H axial displacement (piston) [0091] T.sub.p temperature of compressed air [0092] T.sub.R ambient air temperature [0093] T.sub.b compressed air temperature at base-load [0094] T.sub.hot gas temperature of hot gas in combustor [0095] T.sub.compressed air temperature of compressed air [0096] T.sub.f flame temperature [0097] T.sub.after turbine temperature of exhaust gas [0098] T.sub.part compressed air temperature at part-load