Patent Application
20100028133
Exemplary embodiments of the present invention relate to the art of turbomachines and, more particularly, to a damping structure for a turbomachine component.
Turbomachines include a multitude of components, many of which rotate at high speed during operation. The operation of the turbomachine subjects many of the turbomachine components to stresses resulting from vibration. This includes compressor components, hot gas path (HGP) components, combustor sections and turbine components. Stresses resulting from vibration cause fatigue that shortens operational life of turbomachine components.
In accordance with an exemplary embodiment of the invention, a turbomachine component includes a main body having a surface, and a damping structure mounted to the surface of the main body. The damping structure is formed from a material having a temperature dependent damping characteristic.
In accordance with another exemplary embodiment of the invention, a method of damping vibration of a turbomachine component including mounting a damping structure to a surface of the turbomachine component. The damping structure is formed from a material having a temperature dependent damping characteristic.
Referring to
In accordance with the exemplary embodiment shown, turbine bucket 2 includes a damping structure 60 secured to pressure side surface 20 of airfoil section 16. As will become more fully evident below, damping structure 60 provides vibration damping characteristics when applied to airfoil section 16. In accordance with the exemplary embodiment, damping structure 60 is formed from a material having temperature dependent vibration damping characteristics. More specifically, damping structure 60 includes a first damping characteristic at a first temperature and a second damping characteristic at a second temperature. The first damping characteristic changes to the second damping characteristic at a damping transition temperature. In this manner, turbine bucket 2 is provided with a first level of damping during start up and, as operating temperatures and speeds increase, damping structure 60 passes through the transition temperature to provide an increased level of vibration damping.
In accordance with one aspect of the exemplary embodiment, damping structure 60 is formed from a stainless steel alloy having a damping transition temperature at about 900° F. (482.2° C.). Damping structure 60 is secured to a surface of, for example airfoil section 16. The amount of damping provided by damping structure 60 is dependent upon the temperature at which a vibratory response occurs. That said, below about 900° F. (482.2° C.) the damping is at a first level and above about 900° F. (482.2° C.), damping is at a second, higher level. The above described system provides a 2-14 times increase in damping to turbine bucket 2. Of course it should be realized that the above described range is but an exemplary embodiment of the invention. Other materials having similar or different damping characteristics could also be employed. The particular materials employed depend upon desired damping characteristics at particular operating parameters/temperatures of the turbomachine.
At this point it should be understood that while damping structure 60 is described as being formed from stainless steel, other alloys, including glass alloys, that have a damping transition temperature in a range of about 800° F.-1400° F. (426.6° C.-760° C.) can also be employed. It should also be understood that the particular mounting location of damping structure 60 can also vary. That is, instead of covering an entire airfoil section, damping structure 60 can be selectively applied in high strain areas for maximum stress reduction. In addition, a thermal barrier coating 70 can be applied over an interface between damping structure 60 and airfoil section 16 to provide protection from spallation and oxidation.
Damping structure 60 can be applied to the desired turbomachine component by a number of appropriate joining techniques depending on the materials to be joined. For example, damping structure 60 can be applied to airfoil section 16 using welding, brazing or plasma spray techniques. More over, damping structure 60 can be applied in a single layer, multiple layers or combined with a damping structure having damping properties tied to structural characteristics of the damping material such as taught by co-pending U.S. patent application Ser. No. 11/844,462, entitled “Structures for Damping of Turbine Components” filed on Aug. 24, 2007 incorporated herein by reference in the entirety.
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 present 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.
