Patent Application
20160376917
Aspects of the present invention relate to a method and an apparatus for measuring a deflection of a rotor of a turbomachine.
A turbomachine, such as a turbine or a compressor, includes rotating components mounted on a rotor shaft. For example, in a gas turbine, the rotating components include one or more rotor disks each carrying a row of rotating blades. The weight of the rotor shaft, along with that of the other rotating components, such as the rotor disks, may cause the rotor shaft to bend or sag or deflect in any other manner from its axis of rotation. For normal functioning of the turbomachine to be maintained, it is desirable to measure and rectify any deflection of the rotor shaft.
Current techniques for measuring a deflection of a rotor may include, for example using tip clearance probes. Such an approach may only allow deflection measurements of the rotor to be taken in certain locations. Furthermore, this approach may only allow deflection measurements when the turbomachine is offline. Currently, the issue is addressed by reducing the rotor deflection measurements only to outage where such measurements can be executed.
Briefly described, aspects of the present invention relate to a method and an apparatus for measuring a deflection of a rotor of a turbomachine engine.
According to an aspect, a method for measuring a deflection of a rotor of a turbomachine engine comprises inserting an optical fiber through a central bore of the rotor such that the optical fiber extends lengthwise through the bore along an axial direction of the rotor. The optical fiber is made up of a plurality of fiber optic strain sensors along the length of the optical fiber. Strain information of the optical fiber is measured from the plurality of the fiber optic strain sensors. A shape of the optical fiber is reconstructed based on the measured strain information. A rotor deflection parameter is determined from the reconstructed shape of the optical fiber.
According to another aspect, an apparatus for measuring a deflection of a rotor of a turbomachine engine comprises an optical fiber. The optical fiber is inserted through a central bore of the rotor such that the optical fiber extends lengthwise through the bore along an axial direction of the rotor. The optical fiber is made up of a plurality of fiber optic strain sensors along the length of the optical fiber. Strain information of the optical fiber is measured from the plurality of the fiber optic strain sensors. A shape of the optical fiber is reconstructed based on the measured strain information. A rotor deflection parameter is determined from the reconstructed shape of the optical fiber.
Various aspects and embodiments of the application as described above and hereinafter may not only be used in the combinations explicitly described, but also in other combinations. Modifications will occur to the skilled person upon reading and understanding of the description.
Exemplary embodiments of the application are explained in further detail with respect to the accompanying drawings. In the drawings:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
A detailed description related to aspects of the present invention is described hereafter with respect to the accompanying figures.
As illustrated in
Fiber optic strain sensors 340 are well established for applications in smart structures. Advantages of fiber optic strain sensors 340 may include their small size, low cost, multiplexing capabilities, and capability to be embedded into structures.
As shown in
According to an embodiment, the shape of the optical fiber 320 may be represented by the various discrete points along the length of the optic fiber 320 to which fit a polynomial trend line. A deflection parameter of a rotor 200 may comprise a linearity of a rotor 200, a concavity of a rotor 200, a maximum deflection of a rotor 200 from a rotation axis 240, or any combinations thereof. A linearity of a rotor 200 may refer to how well the measured discrete strain information fits this polynomial trend line. A concavity of a rotor 200 may refer to whether the polynomial trend line is deflected up or down along the rotation axis 240, along with inflection points if the concavity changes along the rotation axis 240. A maximum deflection of a rotor 200 from a rotation axis 240 may refer to a maximum distance from the rotation axis 240 to a furthest point measured radially from the rotation axis 240.
When a deflection measurement is intended, for example, during an outage or engine standstill, the optical fiber 320 may be coupled to the data acquisition device 400 for data collection. At other times, for example, during engine operation, the optical fiber 320 may remain decoupled from the data acquisition device 400 while still being inserted in the rotor 200.
According an alternate embodiment, the optical fiber 320 may be coupled to the data acquisition device 400 via a fastener 360 with a free rotating joint, which allows rotation of the optical fiber 320 while still maintaining electrical contact with the data acquisition device 400 .This enables real-time monitoring of the shape of the rotor 200 during engine operation, by allowing the data acquisition device 400 to capture a time series of strain information from the array of strain sensors 340 and to use the time series to dynamically reconstruct the shape of the optical fiber 320, to obtain a shape of the rotor 200.
According to an embodiment, the size (i.e., a diameter) of the central bore 220 through the rotor 200 may be configured to provide a sufficiently tight tolerance with the optical fiber 320, to prevent or minimize any relative change in position of the optical fiber 320 with respect to the rotor 200, such as a twisting of the optical fiber 320 within the bore 220. This would ensure that the shape of the optical fiber 320 conforms at all times to the shape of the rotor 200 with a desired degree of accuracy.
According to an embodiment, a three dimensional shape of a rotor 200 may be determined from stain information of an optical fiber 320. According to an embodiment, a deflation of a rotor 200 may be determined from the three dimensional shape of the rotor 200.
According to an aspect, the illustrated embodiments may significantly reduce a time for determining a rotor deflection parameter of a rotor 200 in real time during an operation of the rotor 200.
The illustrated embodiments may provide high resolution measurements of a rotor deflection parameter of a rotor 200 during an operation of the rotor 200 based on strain information of an optical fiber 320 obtained from fiber optical strain sensors 340 along a length of the optical fiber 320. A typical but non-limiting exemplary resolution of a fiber optical strain sensing system is about 0.0005″. The illustrated embodiments may provide more than 1000 measurements in a half inch interval.
The illustrated embodiments may simplify a data collection with regards to a rotor 200 of an engine 100 in real time during an operation of the rotor 200.
The disclosed method and the apparatus may be implemented to a plurality of different types of rotating machines, for example, turbomachine including gas turbines, steam turbines, etc.
Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
