Patent Application
20150192019
The subject matter disclosed herein relates to a rotor train torsional mode frequency apparatus and, more particularly, to a rotor train torsional mode frequency apparatus in which a rotor train frequency is adjustable by a change in inertia and/or torsional stiffness somewhere in the train.
Rotating bodies, such as rotors, are used in many different types of mechanical and electrical elements, including generators, motors and other similar devices. These rotating bodies have multiple torsional natural frequency modes and for a variety of reasons, including stress, fatigue, performance, etc., it is desirable to keep these frequency modes outside certain operating ranges. For example, generators, or other mechanical elements including a rotating body, typically have at least one torsional natural frequency mode close to twice a line frequency. If this frequency mode becomes too close to twice a line frequency and becomes excited, it can cause failure of elements in a coupled body, such as the last stage buckets in a coupled turbine.
A frequency of a rotor torsional mode can be shifted by changes in either inertia or torsional stiffness that directly impact the frequency of the rotating body mode of interest (i.e., by adding or removing large shrunk-on rings). However, making such changes requires a process of decoupling of the rotor from other rotor sections in the train and exposing the rotor to allow the installation/removal of the rings. The rings are often large, high strength and expensive and, if the process is unsuccessful, components may need to be machined to remove stiffness or inertia depending on the scenario. Each of these steps can be expensive and time consuming.
The processes described above for tuning the frequency of a rotor torsional mode also tend not to target just the torsional frequency or vibration of the rotor modes. Rather, the current processes of mass addition can affect the stresses in the rotor or lead to unwanted lateral frequency changes.
According to one aspect of the invention, a rotor train torsional mode frequency tuning apparatus is provided and includes a rotor train and a coupling element. The rotor train includes first and second shafts and a coupling operably disposed between the first and second shafts and has a torsional mode frequency. The coupling element is disposed at the coupling and is configured to adjust the torsional mode frequency of the rotor train by a change in at least one of inertia and/or torsional stiffness in the rotor train.
According to another aspect of the invention, a rotor train torsional mode frequency tuning apparatus is provided and includes a coupling element fixedly disposed on a coupling operably disposed between first and second shafts and a portable mass supportively disposable on the coupling element. The portable mass is movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of one of the shafts such that a frequency of a torsional mode of the one of the shafts is substantially identical to a natural frequency of the torsional mode of the other one of the shafts.
According to yet another aspect of the invention, an apparatus for rotor train torsional mode frequency tuning is provided. The rotor train includes a coupling by which respective ends of shafts are connectable with each other. The apparatus includes a coupling element fixedly disposed on the coupling and a portable mass supportively disposable on the coupling element. The portable mass is movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of one of the shafts such that a frequency of a torsional mode of the one of the shafts is substantially identical to a natural frequency of the torsional mode of the other one of the shafts.
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.
The description provided below relates to tuning of torsional natural frequencies in, for example, turbine-generator power trains. The disclosure of such tuning is similar to disclosures in U.S. Pat. No. 8,013,481, the contents of which are incorporated herein by reference. The tuning can be applied at a coupling of two shafts or rotors and is provided by a torsional vibration absorber that serves to adjust a rotor train frequency by a change in inertia and/or torsional stiffness somewhere in the train.
With reference to
The coupling 109 may include a first coupling part 1091, which is associated with the end of the first shaft 105, and a second coupling part 1092, which is associated with the end of the second shaft 108. The first shaft 105, the second shaft 108 and the first and second coupling parts 1091 and 1092 of the coupling 109 of
As will be described is more detail below, the portable mass 4 is re-positionable or movable from one of the stationary element 3 and the coupling element 2 to the other one of the stationary element 3 and the coupling element 2 in order to adjust at least one of a torsional stiffness and a rotational inertia of one of the first shaft 105 and the second shaft 108. More particularly, the portable mass 4 may be moved from the stationary element 3 to the coupling element 2 or from the coupling element 2 to the stationary element 3 in order to adjust at least one of a torsional stiffness and a rotational inertia of the second shaft 108. In so doing, a frequency of a torsional mode of the second shaft 108 can be made substantially identical to a natural frequency of the torsional mode of the first shaft 105.
With particular reference to
With the above-described arrangement, the stationary element 3 includes a flange 16 and hook elements 17. The flange 16 is disposed proximate to the coupling element 2 and the hook elements 17 are arrayed on the flange 16 to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 18 or ring, the portable mass 4 can be lifted off of the hook elements 17 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit inside the annulus 15.
The loading may involve transporting the portable mass 4 from the flange 16 and the hook elements 17 to the coupling element 2 and then sliding the portable mass 4 into the annulus 15. Such loading can be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.
In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 into the annulus 15.
During an operation of the rotor train 110 of
With particular reference to
With the above-described arrangement, the stationary element 3 includes an end face 27, which is disposed proximate to the coupling element 2 and configured to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 28 or ring, the portable mass 4 can be lifted off of the end face 27 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit in the pocket 26.
The loading may involve transporting the portable mass 4 from the end face 27 to the coupling element 2 and then sliding the portable mass 4 in the pocket 26. Such loading may be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.
In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 in the pocket 26.
During an operation of the rotor train 110 of
With particular reference to
With the above-described arrangement, the stationary element 3 includes a flange 34 and hook elements 35. The flange 34 is disposed proximate to the coupling element 2 and the hook elements 35 are arrayed on the flange 34 to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 36 or ring, the portable mass 4 can be lifted off of the hook elements 35 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit inside the recess 33.
The loading may involve transporting the portable mass 4 from the flange 34 and the hook elements 35 to the coupling element 2 and then sliding the portable mass 4 into the recess 33. Such loading can be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.
In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 into the annulus 15.
During an operation of the rotor train 110 of
In accordance with further embodiments and, with reference to
With reference to
The embodiments described above add torsional inertia over or between the coupling 109 in the rotor train 110. This change in inertia yields a torsional natural frequency of oscillation in the second shaft 108 that is substantially identical to the torsional frequency of interest in the first shaft 105 and is obtained using modifications of a fully assembled unit. In addition, since the modifications are being done to a fully assembled unit, the modifications allow for result verification and further modifications, if necessary.
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.
