Patent Application
20130189097
The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a turbomachine including a blade tuning system.
Many turbomachines include a compressor portion linked to a turbine portion through a common compressor/turbine shaft or rotor and a combustor assembly. The compressor portion guides a compressed air flow through a number of sequential stages toward the combustor assembly. In the combustor assembly, the compressed air flow mixes with a fuel to form a combustible mixture. The combustible mixture is combusted in the combustor assembly to form hot gases. The hot gases are guided to the turbine portion through a transition piece. The hot gases expand through the turbine portion along a hot gas path and impart a force to a series of buckets or blades mounted to rotors that, in turn, are coupled to a shaft.
The force causes the blade to rotate creating work that is output through the shaft to, for example, power a generator, a pump, or to provide power to a vehicle. In addition to providing compressed air for combustion, a portion of the compressed airflow is passed through the turbine portion for cooling purposes. The hot gases flowing over the blades create a sound footprint. That is, the blades possess a natural frequency property that is triggered by the hot gas flow. Occasionally, the natural frequency of the blades may match combustor frequency tone ranges. In such cases, the turbomachine may vibrate excessively.
According to one aspect of the exemplary embodiment, a turbomachine includes a compressor portion, a turbine portion operatively connected to the compressor portion, a combustor assembly fluidly connected to each of the compressor portion and the turbine portion, a blade element including a base portion, an airfoil portion, and a natural frequency generated during rotation of the blade element. The blade element is rotatably mounted within one of the compressor portion and the turbine portion, and a blade tuning member rotatably mounted in the one of the compressor portion and the turbine portion. The blade tuning member is configured for engagement with the blade element to alter the natural frequency.
According to another aspect of the exemplary embodiment, a method for adjusting a natural frequency of a blade element in a turbomachine during operation includes rotating a blade element within the turbomachine, positioning a blade tuning member having a predetermined stiffness to contact the blade element, and adjusting a natural frequency of the blade element through contact between the blade element and the blade tuning member.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
With reference to
In the exemplary embodiment shown, turbine portion 6 includes first and second stages 20 and 21 that define gas path 18. Of course it should be understood that the number of stages in turbine portion 6 could vary. First stage 20 includes a plurality of first stage stators or nozzles, one of which is indicated at 30, and a plurality of first stage buckets or blade elements, one of which is indicated at 32, mounted to a first stage rotor wheel 34. Second stage 21 includes a plurality of second stage stators or nozzles, one of which is indicated at 37, and a plurality of second stage buckets or blade elements, one of which is indicated at 39, mounted to a second stage rotor wheel 41. Blade elements 32 include a base portion 60 and an airfoil portion 61. Likewise, blade elements 39 include a base portion 63 and an airfoil portion 64. Blade elements 32 and 39 also include a natural frequency property that is associated with blade element geometry and blade element material.
In accordance with an exemplary embodiment, turbomachine 2 includes a blade tuning member 70 arranged between first and second turbine stages 20 and 21. As will become more fully evident below, blade tuning member 70 is configured to adjust the natural frequency of blade elements 32 and 39. In the exemplary embodiment shown, blade tuning member 70 takes the form of near flow path seal 78. However, it should be understood that blade tuning member 70 may be a separate structure provided in turbine portion 6. In the exemplary embodiment shown, blade tuning member 70 includes a first blade tuning element 86 and a second blade tuning element 87. First blade tuning element 86 is cantilevered from blade tuning member 70 and extends toward base portion 60 of blade elements 32. Second blade tuning element 87 is cantilevered from blade tuning member 70 and that extends toward base portion 63 of blade elements 39. At this point it should be understood that blade tuning member 72 and 74 include generally similar structure.
As best shown in
At this point it should be understood that the exemplary embodiments describe a system for adjusting a natural frequency property of rotating turbomachine blade elements. Blade tuning members act upon base portions of the rotating blade element to alter blade element stiffness. In this manner, blade element stifthess can be adjusted to tune the natural frequency property of each blade element to a desired value. Stiffness can be adjusted by adding elements to the base portion of the buckets, increasing or decreasing a length of the blade tuning elements, altering a thickness of the blade tuning elements, adjusting a height of the crown elements, or altering a volume of the blade tuning elements, e.g., forming hollow regions in the blade tuning element. Selectively altering or tuning the natural frequency property of each blade element row will separate natural frequency property of one stage from a natural frequency of another stage to improve frequency margin requirements.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
