Patent Application
20100050640
The subject matter disclosed herein relates to gas turbines and, more particularly, to combustion cap assemblies used in gas turbines.
Combustion cap assemblies are utilized in gas turbines to deliver fuel and air from fuel nozzles to a combustion chamber in the turbines. Combustion cap assemblies typically include a cap plate through which fuel nozzles deliver fuel and air.
Current cap plates have low cycle and high cycle life limitations. The life limitations are in the form of cracks in the cap plate. Some of the cracking experienced is initiated from low cycle fatigue due to severe thermal gradients caused by proximity to flames in the combustion chamber. Some of the cracking is also due to high cycle fatigue because the relatively low stiffness of the cap plate allows it to be deflected by combustion pressure pulsations.
Some designs attempting to extend the life limitations include thickening the plate to make it have higher life and greater stiffness. This increased thickness makes it harder to manufacture and increases cost. The increased thickness may also lead to a discontinuity where a thicker plate is attached to a thinner plate. Other designs use a covering plate or a shield that is attached to the cap. In these designs, the hotter shield can grow independent of the colder cap structure. Devices including such shields require more parts, complexity and cost than systems with a single cap plate. Accordingly, there is a need for cap assemblies that have improved durability and lifetimes without significant additional cost or complexity.
A combustion cap plate constructed in accordance with exemplary embodiments of the invention includes: a plate having a planar surface and configured to be affixed to an assembly connected to a turbine combustion chamber, the plate defining a central axis perpendicular to the planar surface; a plurality of openings through the plate; and a plurality of raised portions formed by the plate, the raised portions each extending away from the planar surface in a direction of the central axis and having a shape conforming to a thermal gradient incident on the plate during a combustion process.
Other exemplary embodiments of the invention include a system for supplying combustible material to a gas turbine. The system includes: an outer sleeve connectable to a combustion chamber in the gas turbine; a plate having a planar surface and defining a central axis perpendicular to the planar surface, the plate including a plurality of fuel nozzle openings through the plate; and a plurality of fuel nozzle cups affixed in alignment with the plurality of openings. The plate has a plurality of raised portions, the raised portions each extending away from the planar surface in a direction of the central axis and having a shape conforming to a thermal gradient incident on the plate during a combustion process.
Additional features and advantages are realized through the techniques of exemplary embodiments of the invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features thereof, refer to the description and to the drawings.
With reference to
Referring to
A transition portion 30, also referred to as a transition piece 30, is coupled to the combustor casing 24 and facilitates channeling combustion gases generated in the chamber 28 to a turbine nozzle 32. Fuel and air are mixed and ignited within the combustion chamber 28. The resultant combustion gases 34 are channeled from the chamber 28 toward and through a combustion gas stream guide cavity 36 that channels the combustion gas stream towards the turbine nozzle 32.
The cap assembly 20 includes a combustion cap plate 40, which includes a plurality of openings for accommodating the fuel nozzles 22. The cap plate 40 includes a plurality of fuel nozzle openings 42, 44. A plurality of fuel nozzle cups or tubes are affixed in alignment with the fuel nozzle openings 42, 44.
Referring to
Referring to
The planar surface 46 defines a plane that is perpendicular to a central axis 48. In one embodiment, the central opening 42 is symmetrical about the central axis 48. In one embodiment, the peripheral openings 44 are circumferentially positioned on the surface 46, that is, the center of each peripheral opening is located on a circumference formed symmetrically around the central axis 48.
In one embodiment, the surface 46 includes a plurality of raised portions 50 extending away from the surface 46 in a direction offset from a radial line eminating from the central axis 48. In one embodiment, the raised portions 50 maintain substantially the same thickness as the thickness of at least the flat portion of the plate 40.
The raised portions 50 decrease stresses from thermal conditions introduced by combustion processes, by changing the shape of the cap plate 40 into a shape that is more compliant to the directions of thermal deflections caused by the combustion process. This design also causes the plate 40 to stiffen to make it less sensitive to resonances from driving forces caused by the combustion. The shapes of the raised portions 50 are configured to absorb the thermal loads by allowing for out-of-plane thermal growth, i.e., growth away from the planar surface 46. The shapes are constructed based on the thermal loading patterns that exist, however they can be adapted to suit other thermal patterns. In one example, the shapes of the raised portions 50 conform to the thermal deflections.
The cap plate 40 is exposed to severe thermal gradients due to its proximity to flame in the turbine combustion chamber, as well as to cyclic thermal loading from turning the flame on and off. Thermally hot regions of the metallic plate 40 form adjacent to thermally cold regions. In prior plates, the thermally hot regions strain against the thermally cold regions, referred to as “thermal fight”. The cap plates 40 including the raised portions 50 reduce or eliminate thermal flight.
For example, during combustion, the plate 40 develops “hot” portions and “cool” portions. Hot portions are any area of the surface 46 having a significantly higher temperature than other portions, i.e., cool portions, of the surface 46. The hot portions are subject to a higher thermal load than the cool portions. The raised portions 50 are shaped to at least partially conform to the shape of a corresponding hot portion, which allows the material in the hot portion to expand away from the surface 46 and prevent thermal fight between hot and cold portions. By preventing thermal fight, the risk and incidence of cracks is significantly reduced or eliminated.
In one exemplary embodiment, the plurality of raised portions 50 form a plurality of elongated protrusions 50, such as the elongated troughs shown in
In one exemplary embodiment, the elongated protrusions 50 are raised inwardly, i.e., in a direction toward the combustion chamber 28 and toward the rear of the plate 40 when the plate 40 is assembled on the turbine 10. This is shown in the front view of
Referring to
In one embodiment, the pyramidal protrusions 50 are raised inwardly, i.e., in a direction toward the combustion chamber 28 and toward the rear of the plate 40 when the plate 40 is assembled on the turbine 10. This is shown in the front view of
Although the exemplary embodiments herein describe elongated shapes and pyramidal shapes, the shape of the raised portions 50 are not limited to these embodiments. The raised portions may take any desired shape that encompasses all or part of a hot portion of the surface 46.
The devices and systems described herein provide numerous advantages over prior art systems. For example, the devices and systems provide the technical effect of improving the robustness and durability, and correspondingly the lifetime, of a cap assembly plate without requiring changes in thickness or additional components. The devices and systems reduce stress on the cap plate due to thermal fight between portions subject to different loads. Furthermore, the increased stiffness of the plate cap provides for increased resistance to pressure fluctuations produced during the combustion process. Accordingly, the devices and systems described herein provide for increased lifetimes without the introduction of significant complexity or cost.
The capabilities of the embodiments disclosed herein can be implemented in software, firmware, hardware or some combination thereof. As one example, one or more aspects of the embodiments disclosed can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately. Additionally, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform the capabilities of the disclosed embodiments can be provided.
In general, this written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of exemplary embodiments of the invention if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
