Damping resonator with impingement cooling

The invention relates to vibration damping acoustic resonators with impingement cooling, particularly for gas turbine components such as combustor liners and transition ducts.

The use of damping devices such as Helmholtz resonators in turbine engines is known to dampen undesired frequencies of dynamics that may develop in the engine during operation. Examples are disclosed in U.S. Pat. No. 6,530,221.

One or more resonators can be attached to a surface of a turbine engine component such as a combustor liner by welding. Some resonators include passages through which air can enter and purge the cavity enclosed by the resonator. One beneficial byproduct of such airflow is that the component to which the resonator is attached can be impingement-cooled. That is, cooling air can pass through the passages and directly impinge on the hot surface underlying the resonator housing. One such example is U.S. Pat. No. 7,089,741 which shows resonators having side walls with cooling holes and an outer wall with purge holes.

The operational demands of some engines have necessitated resonators with greater damping effectiveness, which can be achieved by increasing the size of the resonators. However, a tradeoff to larger resonators is that the cooling holes become less effective in cooling the surface below, especially when resonator height is increased. As the distance between the impingement cooling holes and the hot surface beneath increases, the cooling air can disperse within the cavity of the resonator without impinging on the hot surface. As a result, the cooling is less effective. Thus, there can be concerns of overheating of the component and/or the welds between the resonator and the component, which can reduce the life cycle of these components.

Increased cooling air may be directed through larger resonators to improve cooling, but this reduces the amount of air that becomes premixed with the fuel, thereby providing a richer fuel mixture which burns hotter and can adversely affect emissions. Furthermore, increasing the coolant flow through the resonator can detune the resonator so that it no longer damps in its target frequency range. Alternately, additional resonators can be provided on the component. However, adding resonators at sub-optimal locations can provide less damping effectiveness than a larger resonator at an optimal location. Further, other design constraints, including space limitations, may limit the ability to attach more resonators at other locations.

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a schematic view of a prior gas turbine combustor assembly.

FIG. 2 is a sectional view taken along line 2 - 2 of FIG. 1 .

FIG. 3 is a side sectional view of a prior resonator taken along line 3 - 3 of FIG. 1 .

FIG. 4 is a side sectional view of a resonator according to aspects of the invention.

FIG. 5 is a perspective view of a first embodiment of the invention.

FIG. 6 is a perspective view of a second embodiment of the invention.

FIG. 7 is a perspective view of a third embodiment of the invention.

FIG. 1 shows a prior art combustor assembly 20 , with a combustor liner 22 , a circular array of damping resonators 24 on the liner, and an air plenum 26 . An additional or alternate location for such resonators is on the transition duct 23 between the combustor assembly 20 and the turbine, or on other engine components enclosing a working gas flow path.

FIG. 2 is a sectional view of the combustor liner 22 of FIG. 1 taken on line 2 - 2 of FIG. 1 through the resonators 24 . The liner 22 surrounds a combustion chamber 28 , which may be generally cylindrical about an axis 30 or may have another shape. Each resonator 24 has an outer wall 32 with coolant inlet holes 34 , an inner wall 36 with acoustic holes 38 , and side walls 40 between the outer and inner walls 32 , 36 , forming a resonance chamber 42 . The inner wall 36 is formed by the combustor liner 22 or other component wall bounding the working gas flow 48 . The acoustic holes 38 may serve three functions: 1) to facilitate resonant vibrations as later described; 2) coolant exits; and 3) film cooling of the component wall 22 .

The air plenum 26 receives compressed air from the engine compressor as known in the art. Some of this air 44 enters the coolant inlet holes 34 in the outer wall 32 of each resonator to cool the inner wall 36 . It then escapes 46 into the combustion chamber 28 , providing film cooling of the inner surface of the liner 22 . The working gas 48 flows generally axially through the combustion chamber. It is shown in a circular swirl in this view for clarity.

FIG. 3 shows a side sectional view of a resonator 24 taken along line 3 - 3 of FIG. 1 . Acoustic vibrations occur in each chamber 42 when the working gas 48 flows past the acoustic holes 38 in the liner 22 . These vibrations are caused by fluid dynamic mechanisms such as Helmholtz resonance (as in pan flutes) and/or by a Karman Vortex (as in regular flutes), depending on the resonator and acoustic hole geometry. The resonator is tuned by its geometry and position such that it cancels unwanted frequencies in the combustor or other component to which it is attached. Methods and formulas for designing and tuning damping resonators are known, and are not detailed here.

Cooling air 44 travels a distance D 1 from the outer wall 32 to the inner wall 36 . This distance is dictated by the volume needed in the resonance chamber 42 to produce a given resonance within a given chamber perimeter. Distance D 1 may be greater than is optimum for impingement cooling of the inner wall 36 . The coolant 44 swirls and disperses 47 in the resonance chamber 42 , thus impinging on the inner wall 36 indirectly. Some of the coolant does not impinge, as shown by flow arrows 45 .

U.S. Pat. No. 7,413,053 improves this situation with tubes in the resonance chamber that carry the coolant from the outer wall to desired impingement locations on the inner wall. However, such tubes require a multi-part assembly of each resonator, thus adding complexity and expense. Furthermore, the coolant gains heat as it travels the length of each tube. The present invention eliminates these disadvantages.

FIG. 4 is a sectional view of a resonator 24 A according to aspects of the invention. The outer wall 32 A has one or more depressions 33 A, each having a bottom portion 50 that is closer to the inner wall 36 than is a peak portion 37 A of the outer wall. For example, distance D 3 may be less than 60% of distance D 2 , or especially less than 40% of distance D 2 . The depression 33 A may be generally bowl-shaped, trough-shaped, or other shapes. Coolant inlet holes 34 A, 35 A are located in the depression 33 A and in the side walls 40 A close to the inner wall 36 . These holes are positioned to direct coolant flows 44 against the inner wall 36 at locations 43 on the inner wall apart from the acoustic holes 38 , thus increasing cooling efficiency.

Some of the coolant inlet holes 49 may be located centrally in the bottom portion 50 of the depression 33 A. Others of the coolant inlet holes 34 A may be located in fillet areas of the bottom portion 50 of the depression 33 A to direct some of the coolant 44 away from a central flow line 51 toward other locations 43 on the inner wall 36 . Yet others of the coolant inlet holes 35 A may be located in a bottom portion of the side walls 40 A, and may be located adjacent to or within a fillet area 41 of the side walls 40 A to direct coolant flows 44 close to the walls 40 A. Thus, the coolant inlet holes 34 A, 35 A, 49 may be positioned to direct the coolant flows 44 , 51 to impinge on the inner wall 36 out of alignment with the acoustic holes 38 .

Peak portions 37 A of the outer wall 32 A may be more distant D 2 from the inner wall than the distance D 1 of a prior resonator with the same perimeter and resonance target, in order to provide sufficient volume in the chamber 42 A for a desired resonance. The resonators 24 A may be formed individually or in groups, for example by molding or sheet-metal stamping. The side walls, the outer wall, the depression, and the coolant inlet holes may be formed as a single sheet-metal part without a multi-part assembly. The side walls 40 A may be bonded to the combustor liner 22 by welding or other means. The side walls 40 A may be taller than a prior art resonator with the same perimeter to provide a volume in the resonance chamber 42 A for a target resonance.

FIG. 5 is a perspective view of an embodiment 24 A of the invention having a sectional view as in FIG. 4 when sectioned on line 4 - 4 . The depression 33 A is in the form of a trough. FIG. 6 shows an embodiment 24 B with a cross-shaped depression 33 B formed by two crossing trough-shaped depressions. It has side walls 40 B, coolant inlet holes 34 B, 35 B, and four peaks 37 B of the outer wall 32 B. It may have a sectional view as in FIG. 4 in one or more directions sectioned on a line 4 - 4 between peaks 37 B. Such a cross-shaped depression 33 B can provide more coverage of coolant inlet holes 34 B near the inner wall 36 when compared to the single trough of FIG. 5 . This embodiment 24 B may have additional peaks 37 B—for example 6 or more—providing additional tuning options and component coverage options.

The embodiments of FIGS. 5 and 6 may have chambers with different volumes. For example in FIG. 5 , the peaks 37 A may have different heights. In FIG. 6 , the peaks 37 B may have one or more different heights. This provides further tuning options, such as tuning at more than one frequency, thus damping more than one frequency.

FIG. 7 shows an embodiment 24 C with a bowl-shaped depression 33 C. The depression 33 C may be rectangular as shown or other bowl shapes, such as circular or oval. It has side walls 40 C, coolant inlet holes 35 C, and a peak 37 C of the outer wall 32 C. This embodiment may have a sectional view as in FIG. 4 in one or more directions as shown by two section lines 4 - 4 .

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.