Patent Application
20070102235
The invention relates in general to devices for suppressing acoustic energy and, more particularly, to the use of such devices in turbine engines.
The use of acoustic damping devices, such as Helmholtz resonators, in turbine engines is known. For instance, various examples of resonators are disclosed in U.S. Pat. No. 6,530,221 and U.S. Patent Application Publication No. 2005/0034918. Resonators can be used to dampen undesired frequencies of dynamics that may develop in the combustor section of the engine during operation. Sufficient damping of combustion dynamics is critical to ensure reliable engine operation. Accordingly, one or more resonators can be attached to a surface of a turbine engine component.
While such resonators have proven to be effective, increased operational demands of turbine engines have necessitated the use of resonator systems with greater damping effectiveness. Thus, there is a need for a system that can improve resonator performance.
Aspects of the invention are directed to a resonator system. The system includes a component, which can be a turbine engine component, such as a combustor liner or a transition duct. The component has an outer peripheral surface and an inner peripheral surface. The component has a first region transitioning into a second region. The first region can be formed in the side of the component including the outer peripheral surface. The first region can extend continuously about the outer peripheral surface of the component.
The first region has a first thickness, and the second region has a second thickness that is greater than the first thickness. A first plurality of passages extends through the first thickness of the component in the first region.
The system further includes a resonator with a resonator plate and at least one side wall extending from and about the resonator plate. The resonator plate has an outside face and an inside face. The at least one side wall connects to the outer peripheral surface of the component so as to enclose at least some of the first plurality of passages. The at least some of the first plurality of passages that are enclosed by the resonator can have a substantially uniform cross-section.
A cavity is defined between the outer peripheral surface and the resonator. The first plurality of passages is in fluid communication with the cavity. Alternatively or in addition, a second plurality of passages extends through the resonator plate from the inside face to the outside face so as to be in fluid communication with the cavity.
The first thickness is substantially uniform in at least a portion of the first region enclosed by the resonator. In one embodiment, the first thickness can be substantially uniform throughout the entire first region. The first thickness can be from at least about 0.75 to about 1.5 millimeters and, more particularly, from about 1.2 millimeters to about 1.5 millimeters. In one embodiment, the first thickness can be from about 30 percent to about 90 percent of the thickness of the second thickness. More specifically, the first thickness can be from about 50 percent to about 60 percent of the thickness of the second thickness. The average thickness of the first region can be less than the average thickness of the second region.
Embodiments of the invention are directed to a system for improving the acoustic performance of a resonator. Aspects of the invention will be explained in connection with one resonator system, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in
The resonator 18 can have any of a number of configurations. For instance, aspects of the invention can be used in combination with any of the resonators disclosed in U.S. Pat. No. 6,530,221 and U.S. Patent Application Publication No. 2005/0034918, which are incorporated herein by reference. To facilitate discussion, the following description will be directed to the resonator shown in
Referring to
The side wall 22 can be provided in any of a number of ways. In one embodiment, the resonator plate 20 and the side wall 22 can be formed as a unitary structure, such as by casting or stamping. Alternatively, the side wall 22 can be made of one or more separate pieces, which can be attached to the resonator plate 20. For example, when the resonator plate 20 is rectangular, there can be four side walls 22, where one side wall 22 extends from each side of the resonator plate 20. In such case, the side walls 22 can be attached to each other where two side walls 22 abut.
The side wall 22 can also be attached to the resonator plate 20 in various places. In one embodiment, the side wall 22 can be attached to the outer periphery of the resonator plate 20. Alternatively, the side wall 22 can be attached to the inside face 28 of the resonator plate 20. Such attachment can be achieved by, for example, welding, brazing or mechanical engagement. The side wall 22 can be substantially perpendicular to the resonator plate 20. Alternatively, the side wall 22 can be non-perpendicular to the resonator plate 20.
In one resonator configuration, sometimes referred to as a “flow-through” type resonator, a plurality of passages 32 can extend through the resonator plate 20 from the outside face 26 to the inside face 28. While particularly suited for flow-through type resonators, aspects of the invention can be used in combination with almost any type of resonator including, for example, “blind-cavity” resonators in which the resonator plate 20 does not include any passages extending therethrough.
For convenience, the following discussion will be directed to a flow-through type resonator; however, it will be understood that such discussion id not intended to limit the scope of the invention. As mentioned above, the resonator plate 20 can have a plurality of passages 32 extending therethrough from the outside face 26 to the inside face 28. The passages 32 are in fluid communication with the cavity 24. The passages 32 can have any cross-sectional shape and size. For instance, the passages 32 can be circular, oval, rectangular, triangular, or polygonal. Ideally, each of the passages 32 has a substantially constant cross-section. The passages 32 can be substantially identical to each other. The passages 32 can be arranged on the resonator plate 20 in various ways. For example, in one embodiment, the passages 32 can be arranged in rows and columns.
The resonator 18 can be attached to the outer peripheral surface 12 of the combustor component in various ways, such as by welds 30 or by brazing. The outer peripheral surface 12 can be substantially flat, or it can be curved or otherwise non-flat. The combustor component can also have an inner peripheral surface 13. A plurality of passages 34 can extend through the combustor component from the inner peripheral surface 13 to the outer peripheral surface 12. The passages 34 are in fluid communication with the cavity 24.
There can be any quantity of passages 34 in the combustor component, and the passages 34 can be arranged in various ways. In one embodiment, the passages 32 in the resonator plate 20 can be arranged in X rows and Y columns, and the passages 34 in the combustor component can be arranged in X-1 rows and Y-1 columns. In this arrangement or in other arrangements, the passages 32 in the resonator plate 20 can be staggered or otherwise offset from the passages 34 in the combustor component. However, aspects of the invention are not limited to any particular arrangement. In a flow-through type resonator, the passages 32 in the resonator plate 20 can be referred to as the upstream passages, and the passages 34 in the combustor component can be referred to as the downstream passages, based on the flow path in the combustor section 10.
One or more resonators 18 can be attached to the outer peripheral surface 12 of the combustor component so as to enclose at least some of the passages 34 in the combustor component. The resonators 18 are particularly effective when disposed at or near the locations within the flow path of the combustor section that has the greatest acoustical pressure amplitudes and locations that are in fluid communication with the combustion zone. The locations having the greatest acoustical pressure amplitude can be established experimentally or analytically. In cases where a plurality of resonators 18 are attached to the combustor component, the resonators 18 can be arranged on and about the outer peripheral surface 12 of the combustor component in numerous ways, and aspects of the invention are not limited to any particular arrangement.
The acoustic damping performance of a resonator is a function of the length of the passages 34 in the combustor component, among other things. More specifically, the acoustic damping performance of a resonator is inversely related to the length of the downstream passages 34. Thus, the shorter the length of the downstream passages 34, the greater the damping performance of the resonator. According to aspects of the invention, the length of the downstream passages 34 can be decreased by reducing the thickness of the combustor component in a region containing the passages 34.
For instance, as shown in
Preferably, all of the downstream passages 34 are provided in the first region R1. In one embodiment, the region R1 can extend continuously about the entire periphery of the combustor component. Alternatively, the region R1 can comprise a plurality of regions of reduced thickness collectively extending at intervals about the periphery of the combustor component. In such case, each individual region of reduced thickness can include a plurality of the downstream passages 34. Preferably, the downstream passages 34 have a substantially uniform cross-section through thickness T1 of the first region.
In one embodiment, the thickness T1 can be substantially uniform at least in an area between any neighboring pair of the downstream passages 34. In another embodiment, the thickness T1 can be substantially uniform throughout an area of the first region R1 that is enclosed by one of the resonators 18. In still another embodiment, the thickness T1 can be substantially uniform throughout the first region R1. The term substantially uniform includes perfectly uniform as well as slight variations thereof. For instance, the first region R1 can include a slight taper.
The thickness T1 of the region R1 is preferably as small as possible so long as the component can withstand, structurally and otherwise, the operational environment of the combustor section without degradation in strength. In one embodiment, the minimum thickness of the first region R1 can be from about 0.75 to about 1.5 millimeters thick. In another embodiment, the thickness T1 of the first region R1 can be from about 1.2 millimeters to about 1.5 millimeters thick.
As noted above, the thickness T1 of first region R1 may not be substantially constant. Likewise, the thicknesses T2, T3 of the neighboring regions R2, R3 may not be substantially constant. However, the average thickness of the first region R1 can be less than the average thickness associated with each of the neighboring regions R2, R3. In one embodiment, the thickness T1 at any point within the first region R1 can be less than the thickness T2 at any point in the neighboring region R2 and/or the thickness T3 at any point in the neighboring region R3. In one embodiment, the thicknesses T2, T3 of the neighboring regions R2, R3 can be about 2.5 millimeters, whereas the thickness T1 of the first region R1 can be as small as 1.3 millimeters. There can be almost any relative thickness between the thickness T1 of the first region R1 and the thicknesses T2 and T3 associated with neighboring regions R2 and R3, respectively. For example, the thickness T1 of the first region R1 can be from 30% to 90% of the thickness T2, T3 of at least one of the neighboring regions R2, R3. In one embodiment, the thickness T1 of the first region R1 can be about 50-60% of the thickness of at least one of the neighboring regions R2, R3.
The first region R1 can be formed in the combustor component in various ways. For instance, the first region R1 can be formed by machining, rolling and/or other processes that can locally reduce the thickness of the combustor component in the region R1. Alternatively, the first region R1 can be formed by welding a first component segment defining region R1 to second and third component segments that define the neighboring regions R2 and R3.
In one embodiment, the region R1 of reduced thickness can be formed in the side of the combustor component including the outer peripheral surface 12, as shown in
While the length of the downstream passages 34 can be reduced by counter-boring each individual passage 34, such a construction is not desirable because the process of counter-boring each of the downstream passages 34 can be time consuming and labor intensive. Aspects of the invention recognize that manufacturing efficiencies can be gained by providing the downstream passages 34 in a relatively larger area of the combustor component with a reduced thickness T1.
Having described a resonator system according to aspects of the invention, one manner in which such a system can be used will now be described. For purposes of this example, it will be assumed that the resonators 18 are attached to the outer peripheral surface 12 of the combustor liner 14. During engine operation, the combustor section receives compressed air 36 from the compressor section (not shown) of the engine. The air 36 passes over the outer peripheral surface 12 of the liner 14.
The compressed air 36 can be mixed with fuel (not shown) at various points in its path through the combustor section, and the air-fuel mixture can be ignited to form the combustion gases 38. The gases 38 can be routed from the combustor section to the turbine section through the liner 14 and the transition duct 16. Acoustic pressure waves in the gas path 38 can arrive at the downstream passages 34 and can be substantially dampened at the resonator 18. The operation of a resonator is well known and is described in more detail in U.S. Pat. No. 6,530,221 and U.S. Patent Application Publication No. 2005/0034918, which are incorporated by reference. Because the length of the downstream passages 34 have been shortened in accordance with aspects of the invention, a greater acoustic response can be achieved to thereby enhance the damping capability of the resonator 18.
A portion 36a of the compressed air 36 can enter the resonator 18 through the upstream passages 32 in the resonator plate 20. Thus, there can be a steady purging or scavenging flow of air through the resonator 18. Such airflow through the resonator 18 can allow for a broader frequency response bandwidth so that the accuracy and repeatability of frequency tuning are rendered much less critical than in a “blind-cavity” resonator. Further, the airflow can be used to cool the portion of the liner 14 enclosed by the resonator 18. Lastly, the air 36a can exit the resonator 18 through the passages 34 in the liner 14, and join the combustion gases 38 flowing through the liner 14.
The acoustic damping performance of a resonator 18 may be expressed in terms of acoustic conductance, which can be defined as the in-phase component of volume-velocity through the downstream passages 34, divided by the amplitude of the pressure oscillation at the downstream passages 34 on the inner peripheral surface 13 side of the combustor component. A higher value of acoustic conductance indicates better damping performance. As the conductance of the resonators increases, the quantity of resonators required to provide adequate damping is reduced. Fewer resonators can result in cost savings and less cooling air consumption. Alternatively, the quantity of resonators can remain unchanged, but overall increase in resonator performance can provide greater margins against the occurrence of combustion dynamics. Preferably, the resonator system according to aspects of the invention is adapted to minimize the impact on other engine operating parameters including, for example, emissions, pressure drop, and liner temperature.
The natural frequency and the conductance of a through-flow resonator are governed by the geometries of the upstream and downstream passages 32, 34, the volume of the cavity 24, and the steady pressure differentials across each of the upstream and downstream passages 32, 34. The dynamic response of a through-flow resonator can be analytically modeled as shown in
To optimize resonator performance in accordance with aspects of the invention, the acoustic inertance Md of the downstream passages 34 can be made as small as possible within the design and performance limits of the system. Minimizing the acoustic inertance Md of the downstream passages 34 can have the effect of maximizing the conductance of the resonator 18 because a comparatively larger volume of the cavity 24 (corresponding to a large compliance, C) will result from frequency tuning when the inertance Md of the downstream passages 34 is small. A large compliance, in turn, can isolate the flow oscillations from the high-resistant upstream flow path, making the conductance large.
As discussed above, the acoustic conductance of a resonator 18 can vary as a function of the local thickness of the component to which the resonator is attached. Generally, reductions in the thickness are can result in improved resonator performance. According to one analytical model, a 50 percent reduction in the length of the passages 34 in the combustor component can result in about a 50 percent increase in the normalized conductance of the resonators 18.
In addition to those systems described herein, it will be appreciated that the system according aspects of the invention can be used in connection with a variety of resonator designs including, for example, those disclosed in U.S. Pat. No. 6,530,221 and U.S. Patent Application Publication No. 2005/0034918, which are incorporated by reference. It should be noted that resonators according to aspects of the invention have been described herein in connection with the combustor section of a turbine engine, but it will be understood that the resonators can be used in any section of the engine that may be subjected to undesired acoustic energy. The resonator system according to aspects of the invention can have application beyond the context of turbine engines to improve the acoustic damping performance of any resonator. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.
