Patent Application
20130330187
The subject matter disclosed herein relates to an apparatus and method for mitigating out-of-roundness effects at an inner turbine shell of a gas turbine. Several turbine section designs include an inner turbine shell that provides a flow path for a working gas through the turbine and an outer turbine shell that surrounds the inner turbine shell. Generally, a rotor having a plurality of blades is disposed within the inner turbine shell and rotates as a result of the working gas passing through the turbine. The clearance between the inner turbine shell and the plurality of turbine blades determines turbine efficiency and power production and can be affected by a deviation of the inner turbine shell from a circular cross-section, also known as out-of-roundness. Due to connections between inner turbine shell and outer turbine shell, loads due to various operational stresses are often transferred from the outer turbine shell to the inner turbine shell and cause the inner turbine shell to distort, a condition known as out-of-roundness. There is therefore a desire to design turbine shells that mitigate out-of-roundness effects. The present disclosure provides a method and apparatus that reduces load transfer between outer turbine shell and inner turbine shell to reduce out-of-roundness effects.
According to one aspect, the present disclosure provides a method of mitigating out-of-roundness effects at a turbine, the method including: providing an inner turbine shell of the turbine within an outer turbine shell of the turbine; and coupling the inner turbine shell to the outer turbine shell using a ring insert that is segmented into a plurality of ring insert segments that reduce a transfer of load from the outer turbine shell to the inner turbine shell to mitigate out-of-roundness of the inner turbine shell.
According to another aspect, the present disclosure provides a turbine including an outer turbine shell; an inner turbine shell; and a ring insert configured to couple the inner turbine shell to the outer turbine shell and segmented into a plurality of ring insert segments to reduce a load transfer from the outer turbine shell to the inner turbine shell.
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.
In one aspect, the length of the ring insert segment can be determined using a processor. The exemplary processor can run a simulation to determine the length of the ring insert segment at which an out-of-roundness of the inner turbine shell meets a selected criterion. The processor can simulate various operating cycles of the turbine and determine out-of-roundness of the inner turbine shell at various times during the cycle.
Alternately, a turbine having the exemplary ring insert segments can be constructed and operated. Sensors can be disposed at various locations of the inner turbine shell and the out-of-roundness of the inner turbine shell can be observed as the turbine is run through various operational cycles. A ring insert segment length and spacing can thereby be determined by observing an effectiveness of the various ring insert segment lengths with respect to mitigating out-of-roundness effects.
In one aspect, the length of the ring segment is selected at which the out-of roundness meets a selected criterion. In various embodiments, the right segment is selected when a length of the ring segment keeps the out-of-roundness of the inner turbine shell within an acceptable tolerance level. In another embodiment, the selected criterion can be an out-of-roundness tolerance over a selected time frame.
Therefore, in one aspect, the present disclosure provides a method of mitigating out-of-roundness effects at a turbine, the method including: providing an inner turbine shell of the turbine within an outer turbine shell of the turbine; and coupling the inner turbine shell to the outer turbine shell using a ring insert that is segmented into a plurality of ring insert segments that reduce a transfer of load from the outer turbine shell to the inner turbine shell to mitigate out-of-roundness of the inner turbine shell. In one embodiment, the plurality of ring insert segments includes four ring insert segments. At least one of the ring insert segments subtends an angle measured from a longitudinal axis of the inner turbine shell selected from the group consisting of: (i) less than 90 degrees; (ii) between about 15 degrees and about 85 degrees; and (iii) between about 30 degrees and about 70 degrees. A processor can be used to determine a length and position of the ring insert segments at which an out-of-roundness of the inner turbine shell meets a selected criterion. The length of a ring insert segment is selected to reduce a load path between the outer turbine shell and the inner turbine shell. In various embodiments, the load is a result of a thermal stress at the outer turbine shell. The ring insert segments are disposed at a thrust collar of the inner turbine shell at equidistant locations around a circumference of the inner turbine shell. In various embodiments, the inner turbine shell is formed of at least two azimuthal shell sectors.
A turbine including an outer turbine shell; an inner turbine shell; and a ring insert configured to couple the inner turbine shell to the outer turbine shell and segmented into a plurality of ring insert segments to reduce a load transfer from the outer turbine shell to the inner turbine shell. In an exemplary embodiment, the ring insert is segmented into four ring insert segments. An angle subtended by at least one of the ring insert segments is selected from the group consisting of: (i) less than 90 degrees; (ii) between about 15 degrees and 85 degrees; and (iii) between about 30 degrees and about 70 degrees. A processor running a program of a model of the turbine can be used to determine a length of the ring insert. The length of the ring insert segments is generally selected to reduce a load path between the outer turbine shell and the inner turbine shell. The load is generally related to thermal stress at the outer turbine shell. In an exemplary embodiment, the ring insert segments are evenly spaced around a circumference of the inner turbine shell. In various embodiments, the inner turbine shell is formed of at least two shell sectors extending over a selected azimuthal angle.
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.
