Abstract:
A method and system for monitoring creep in a moving object are provided. The creep monitoring system includes a creep sensor assembly formed onto a surface of an object rotatable about an axis, the creep sensor assembly includes at least one of an image pattern and a radio frequency interrogatable circuit. The creep monitoring system also includes an online monitoring system communicatively coupled to the creep sensor assembly. The online monitoring system configured to collect information from the creep sensor assembly relative to an amount and a rate of creep of the object. The creep monitoring system also includes a processor programmed to receive the information, correct the information for movement of the creep sensor assembly during the collection, and determine a creep rate, a crack presence, and a temperature of the object simultaneously.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The field of the invention relates generally to rotating machinery, and more specifically, to a system and method for online monitoring of creep of rotating components. 
         [0002]    As rotatable machines operate, a condition of components of the machine may deteriorate over time. This degradation of condition typically affects performance and may be due to various factors. One such factor is the deformation of the material of the component when exposed to stresses less than its yield strength over time, or creep. Creep can degrade gaps between parts that move relative to each other and can create projectile hazards and debris if the creep is permitted to occur until failure of the component material. Some components, such as turbine blades, are difficult or costly to remove from service for periodic inspections, and scheduled shutdowns for plant maintenance and repair may occur infrequently enough that creep may cause damage before it can be detected and repaired. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    In one embodiment, a creep monitoring system includes a creep sensor assembly formed onto a surface of an object rotatable about an axis, the creep sensor assembly includes at least one of an image pattern and a radio frequency interrogatable circuit. The creep monitoring system also includes an online monitoring system communicatively coupled to the creep sensor assembly. The online monitoring system configured to collect information from the creep sensor assembly relative to an amount and a rate of creep of the object. The creep monitoring system also includes a processor programmed to receive the information, correct the information for movement of the creep sensor assembly during the collection, and determine a creep rate, a crack presence, and a temperature of the object simultaneously. 
         [0004]    In another embodiment, a method of monitoring creep in a moving object includes applying a creep sensor assembly to a moving object, receiving from the creep sensor assembly information relative to creep associated with the moving object, determining, using a processor, at least one of an amount of creep and a rate of creep of the moving object, and outputting the at least one of an amount of creep and a rate of creep of the moving object. 
         [0005]    In yet another embodiment, a creep sensor assembly includes at least one of an image pattern and a radio frequency interrogatable sensor direct deposited on a moving object. The creep sensor assembly is direct deposited using at least one of a direct write technique, a thermal spray technique and a screen printing technique. The image pattern includes at least one of a moiré pattern, film cooling holes and a surface feature of the object. The radio frequency interrogatable sensor includes an antenna portion and a capacitor portion electrically coupled to the antenna portion. A dimensional property of the image pattern changes with creep in the moving object and an electrical property of the radio frequency interrogatable sensor changes with creep in the moving object. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIGS. 1-12  show exemplary embodiments of the method and system described herein. 
           [0007]      FIG. 1  is a schematic block diagram of an online creep monitoring system in accordance with an exemplary embodiment of the present invention; 
           [0008]      FIG. 2  is a schematic block diagram of a breakdown of components that may be used with the online creep monitoring system shown in  FIG. 1 ; 
           [0009]      FIG. 3A  is a schematic block diagram illustrating a plurality of creep sensor assemblies that may be used with the online creep monitoring system shown in  FIG. 1 ; 
           [0010]      FIG. 3B  is a schematic diagram of imaging a moiré pattern on an object in accordance with an exemplary embodiment of the present invention. 
           [0011]      FIG. 4  is a schematic block diagram illustrating a plurality of manufacturing techniques used to form creep sensor assemblies shown in  FIG. 3B  on a surface of the object; 
           [0012]      FIG. 5A  is a cross sectional view of the creep sensor assembly shown in  FIG. 1  that may be used with non-TBC objects in accordance with an exemplary embodiment of the present invention; 
           [0013]      FIG. 5B  is a cross sectional view of the creep sensor assembly shown in  FIG. 1  that may be used with TBC objects in accordance with another exemplary embodiment of the present invention; 
           [0014]      FIG. 6  is a schematic block diagram illustrating a plurality of materials that may be used to form the creep sensor assemblies shown in  FIG. 1  on a surface of the object; 
           [0015]      FIG. 7  is a schematic block diagram illustrating the online imaging system using at least one of a passive imaging mode and an active imaging mode; 
           [0016]      FIG. 8  is a flowchart of an image processing method for calculating a creep rate of object in real-time using the collected images of creep sensor assemblies in accordance with an exemplary embodiment of the present invention; 
           [0017]      FIG. 9  is a schematic block diagram of the remote interrogation system shown in  FIG. 1  in accordance with an exemplary embodiment of the present invention; 
           [0018]      FIG. 10  is a plan view of the creep sensor assembly associated with the remote interrogation system in accordance with an exemplary embodiment of the present invention; 
           [0019]      FIG. 11  is a schematic diagram of the remote interrogation system shown in  FIG. 1  in accordance with an exemplary embodiment of the present invention; 
           [0020]      FIG. 12  is a flow chart of a method of remotely interrogating RF creep sensor assemblies formed on, for example, high-speed rotating objects such as turbine blades. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The following detailed description illustrates embodiments of the invention by way of example and not by way of limitation. It is contemplated that the invention has general application to analytical and methodical embodiments of monitoring creep in moving objects in industrial, commercial, and residential applications. 
         [0022]    As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0023]    Embodiments of the present invention provide an online creep monitoring system for high speed rotating devices, such as, but not limited to, a gas turbine blade. In various embodiments, a creep rate, a crack presence and size, a temperature, and a coating spallation for high speed rotating devices are monitored simultaneously. The online creep monitoring system can be a part of an online prognosis and health monitoring (PHM) system. 
         [0024]      FIG. 1  is a schematic block diagram of an online creep monitoring system  100  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, online creep monitoring system  100  includes at least one of an online imaging system  102  and a remote interrogation system  104 , such as, but not limited to, a radio frequency (RF) remote interrogation system. Online imaging system  102  includes a processor  106  configured to execute an image processing program  108  that directs online imaging system  102  to acquire images and/or image patterns from an imaging sensor  109  and analyze the images and/or image patterns for creep related calculations. The image pattern can be a moiré pattern, film cooling holes or other image patterns with fine features for creep rate calculation. Remote interrogation system  104  also includes a processor  110  configured to execute a signal processing program  112  that directs remote interrogation system  104  to acquire RF signals from an RF sensor  113  and to calculate a creep rate in real-time using the collected RF signals. Online imaging system  102  and remote interrogation system  104  are configured to monitor a relatively high-speed rotating object  114 , such as, but not limited to, a turbine blade, a fan or compressor blade, or other airfoil having a creep sensor assembly  116  formed thereon. In various embodiments, creep sensor assembly  116  includes imaging sensor  109  for use with online imaging system  102  or RF sensor  113  for use with remote interrogation system  104 . Imaging sensor  109  and RF sensor  113  may be enclosed in respective housings,  115  and  117  that may be positioned within a casing (not shown) surrounding object  114  or may be positioned outside of the casing but, still in communication with a respective one of creep sensor assembly  116  for example, through a viewport of a wave-guide. When positioned within the casing, housings  115  and  117  may be cooled or otherwise environmentally supported for operation within the casing over relatively long periods of time. For temperature measurement, creep sensor assembly  116  is illuminated with a light source  126 . Creep sensor assembly  116  is formed of a doped material that generates a phosphorescence signal at different wavelength bands from light source  126  such that its intensity ratio or lifetime can be used to detect a temperature of object  114 . Online imaging system  102  and remote interrogation system  104  is configured to measure a temperature  118 , a creep rate  120 , a crack  122  and an amount of creep  124  simultaneously. Multiple creep sensor assemblies  116  may be deposited on the object surface at multiple locations for local creep detection, and they can be either isolated or connected to form a network. Creep sensor assemblies  116  may be formed of different materials to be visible with different detectors if under a TBC or not. 
         [0025]      FIG. 2  is a schematic block diagram of a breakdown of components that may be used with online creep monitoring system  100  (shown in  FIG. 1 ). In the exemplary embodiment, relatively high-speed rotating object  114  may include but is not limited to, a turbine blade  200 , a bladeless disk  202 , such as a Tesla turbine rotor, a disk  204 , a bucket  206 , a fan or compressor blade  208 , or other airfoil  210 . Object  114  may include components used in gas turbine engines and steam turbines, coated  214  with a thermal barrier coating (TBC) and uncoated. 
         [0026]      FIG. 3A  is a schematic block diagram illustrating a plurality of creep sensor assemblies  116  that may be used with online creep monitoring system  100  (shown in  FIG. 1 ).  FIG. 3B  is a schematic diagram of imaging a moiré pattern on an object  114 . In the exemplary embodiment, image patterns  300  can include a moiré pattern  302 , film cooling holes  304 , or other image patterns  306  having fine features for creep rate calculation. In the exemplary embodiment, a moiré pattern  308  is positioned on object  114 . Moiré pattern  308  is viewed through a lens  310  and if object  114  has stretched, for example, due to creep a moiré beat pattern  312  is observed and the amount of creep is determined from varying characteristics of moiré beat pattern  312 . 
         [0027]      FIG. 4  is a schematic block diagram illustrating a plurality of manufacturing techniques used to form creep sensor assemblies  116  (shown in  FIG. 3A ) on a surface of object  114 . In the exemplary embodiment, manufacturing techniques for directly deposited creep sensor assemblies  116  include, for example, but not limited to, a direct write technique  400 , a screen printing technique  402 , a thermal spray technique  404 , and a water jet technique  406 . In addition to directly deposited techniques other printing and forming techniques  408  are contemplated. 
         [0028]      FIG. 5A  is a cross sectional view of creep sensor assembly  116  (shown in  FIG. 1 ) that may be used with non-TBC objects  114  in accordance with an exemplary embodiment of the present invention.  FIG. 5B  is a cross sectional view of creep sensor assembly  116  (shown in  FIG. 1 ) that may be used with TBC objects  114  in accordance with another exemplary embodiment of the present invention. In the exemplary embodiments, creep sensor assemblies  116  are embodied in a multi-layered structure. Each of the different layers of creep sensor assemblies  116  permit a thermal expansion of creep sensor assemblies  116  to substantially match a thermal expansion of object  114 , to protect and increase a life of creep sensor assemblies  116  under harsh environments, and to serve as insulation, and abrasion or moisture protection. 
         [0029]    In the exemplary embodiment, each of creep sensor assemblies  116  used with non-TBC objects  114  and with TBC objects  114  include three basic configurations. A first configuration  500  associated with a non-TBC object  114  includes a substrate  502 , for example, a blade or bucket with a protective environmental coating  504  and a sensor  506  deposited on top. 
         [0030]    A second configuration  508  associated with a non-TBC object  114  includes substrate  502 , a protective environmental coating  504 , a dielectric layer  510 , and sensor  506 . The addition of dielectric layer  510  permits forming an RF sensor, which includes a resonance circuit containing a capacitor, of which a first portion is formed on one side of dielectric layer  510  and a second portion is formed on a second side of dielectric layer  510 . 
         [0031]    A third configuration  512  associated with a non-TBC object  114  includes substrate  502 , an adhesion promoter layer  514 , a dielectric layer  510 , and sensor  506 . Adhesion promoter layer  514  also acts as protective environmental coating for substrate  502 . Adhesion promoter layer  514  used in third configuration  512  facilitates improving an attachment of dielectric layer  510 , and sensor  506  to substrate  502 . 
         [0032]    A first configuration  516  associated with a TBC object  114  includes a substrate  502 , for example, a blade or bucket with a TBC layer  518 , sensor  506 , and a protective overcoat layer  520 . 
         [0033]    A second configuration  522  associated with a TBC object  114  includes substrate  502 , TBC layer  518 , dielectric layer  510 , sensor  506 , and protective overcoat layer  520 . The addition of dielectric layer  510  permits forming an RF sensor, which includes a resonance circuit containing a capacitor, of which a first portion is formed on one side of dielectric layer  510  and a second portion is formed on a second side of dielectric layer  510 . 
         [0034]    A third configuration  524  associated with a TBC object  114  includes substrate  502 , adhesion promoter layer  514 , a dielectric layer  510 , sensor  506 , and protective overcoat layer  520 . The addition of dielectric layer  510  permits forming an RF sensor, which includes a resonance circuit containing a capacitor, of which a first portion is formed on one side of dielectric layer  510  and a second portion is formed on a second side of dielectric layer  510 . 
         [0035]    In various embodiments, protective overcoat layer  520  may also be applied to non-TBC objects  114 . Additionally, some embodiments of the above described configurations may use adhesion promoter layer  514  between additional layers when necessary, for example, between protective environmental coating  504  and sensor  506  in configuration  500  and between substrate  502 , and dielectric layer  510  shown in configuration  508 . 
         [0036]      FIG. 6  is a schematic block diagram illustrating a plurality of materials that may be used to form creep sensor assemblies  116  (shown in  FIG. 1 ) on a surface of object  114 . In the exemplary embodiment, a material used to form creep sensor assemblies  116  has at least one of the following characteristics: a different emissivity than the substrate material  600 , is conductive  602 , is doped  604  with other materials for better image contrast or to form a temperature sensor, and is functional  606  under a harsh environment proximate object  114 . In one embodiment, online imaging system  102  and remote interrogation system  104  includes imaging sensor  109  or RF sensor  113  respectively that are enclosed in housing  115  and  117 , respectively that are configured to withstand the harsh environment inside the casing of, for example, a turbine engine component. 
         [0037]      FIG. 7  is a schematic block diagram illustrating online imaging system  102  using at least one of a passive imaging mode  700  and an active imaging mode  702 . Passive imaging mode  700 , in one embodiment, incorporates a short integration time image sensor  704  to “freeze” the high-speed rotating objects  114  so that only one object  114  may be analyzed at a time. Active imaging mode  702  may use, for example, light source  126  generating short light pulses to “freeze” high-speed rotating objects  114  for collection of images. Light source  126  may include for example, but not limited to an LED source  706 , a laser source  708 , a strobe  710 , and an arc lamp  712 . 
         [0038]      FIG. 8  is a flowchart of an image processing method  800  for calculating a creep rate of object  114  in real-time using the collected images of creep sensor assemblies  116  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, method  800  includes receiving raw image data  802 , performing  804  a dark subtraction process on the received image data, and correcting  806  a geometry associated with the image data. Method  800  also includes intensity correcting  808  the image data, registering  810  the image, and calculating  812  creep related parameters, such as, but not limited to, a creep rate  814 , a crack size  816 , for example, a crack width, and a temperature  818  of object  114 . 
         [0039]      FIG. 9  is a schematic block diagram of remote interrogation system  104  (shown in  FIG. 1 ) in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, remote interrogation system  104  includes a signal processing program  902  configured to calculate the creep rate in real-time using collected RF signals. An RF signal generated in for example, RF sensor  113  is transmitted to conductive creep sensor assembly  116  such that a connectivity of creep sensor assembly  116  can be detected. Creep sensor assembly  116  distorts or traces break connection when a local or a global creep rate  904  exceeds a pre-determined limit. Such distortion or breakage provides a digital device to detect “crept”  906  or “non-crept” blades. In various embodiments, remote interrogation system  104  is configured to perform as an analog device to measure creep rate  904 . Remote interrogation system  104  is configured to measure creep and an amount  908  of object cracking simultaneously. 
         [0040]      FIG. 10  is a plan view of creep sensor assembly  116  associated with remote interrogation system  104  in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, creep sensor assembly  116  is associated with an RF remote interrogation system and includes an antenna portion  1002  and a capacitor portion  1004 . Antenna portion  1002  and capacitor portion  1004  are formed on a surface of object  114  as described above. Each of antenna portion  1002  and capacitor portion  1004  adhere to and move with the surface of object  114  that they are adhered to. As such, if a portion of the surface of object  114  stretches due to creep, one or both of antenna portion  1002  and capacitor portion  1004  will also stretch with the surface. Charging the dimensions of antenna portion  1002  and/or capacitor portion  1004  causes their electric properties to change correspondingly. The changes in the electrical properties are determined when creep sensor assembly  116  is interrogated by remote interrogation system  104 . Remote interrogation system  104  is then able to determine an amount of creep, a rate of creep, a presence of cracking in the surface, and other related properties of object  114  during operation and in real-time. 
         [0041]      FIG. 11  is a schematic diagram of remote interrogation system  104  (shown in  FIG. 1 ) in accordance with an exemplary embodiment of the present invention. In the exemplary embodiment, a turbine rotor  1102  is rotatably supported within a turbine casing  1104 . Turbine rotor  1102  includes a plurality of objects  114  (shown in  FIG. 1 ) spaced circumferentially thereon. One or more interrogators  1106 , which may be embodied in an RF transceiver, are spaced circumferentially about turbine rotor  1102 . Interrogators  1106  are communicatively coupled to remote interrogation system  104  through hard wire conduits  1108  or wirelessly. One or more objects  114  includes a creep sensor assembly  116  formed thereon or coupled thereto as described above. In another embodiment, one or more imaging sensors  109  are spaced circumferentially about turbine casing  1104  and are communicatively coupled to online imaging system  102 . In one embodiment, imaging sensor  109  is positioned outside of turbine casing  1104  and uses a viewport extending through turbine casing  1104  to permit a direct line of sight between imaging sensor  109  and creep sensor assembly  116 . In another embodiment, imaging sensor  109  uses a fiber  1110  to permit a view of creep sensor assembly  116  for image acquisition. In yet another embodiment, imaging sensor  109  is positioned within turbine casing  1104  and hardened to withstand the environment within turbine casing  1104 . Such hardening may include cooling  1112  via a closed loop cooling system or may include an open loop cooling system, such as, but not limited to, a bleed air system. 
         [0042]      FIG. 12  is a flow chart of a method  1200  of remotely interrogating RF creep sensor assemblies  116  formed on, for example, high-speed rotating objects  114  such as turbine blades. The patterns of creep sensor assemblies  116  are for example, directly deposited on the blade surface by direct write, thermal spray or screen printing techniques. The patterns are formed of a multi-layered structure to match the thermal expansion of the blade, to increase the longevity under harsh environments, and to serve as insulation. In the exemplary embodiment, method  1200  includes acquiring  1202  a raw RF signal that represents a condition of at least one of creep sensor assemblies  116 . Corrections  1204  to the raw signal are applied and the corrected signals are transmitted to an RF processor  1206  for signal processing. The signals are processed to generate output signals representative of a creep  1208  of objects  114  using creep sensor assemblies  116 . Additionally, creep rate  1210 , an amount object  114  has crept  1212 , and a presence of a crack  1214  in object  114  are determined simultaneously. 
         [0043]    As used herein, real-time refers to outcomes occurring at a substantially short period after a change in the inputs affecting the outcome, for example, computational calculations. The period may be an amount of time between each iteration of a regularly repeated task. Such repeated tasks are called periodic tasks. The time period is a design parameter of the real-time system that may be selected based on the importance of the outcome and/or the capability of the system implementing processing of the inputs to generate the outcome. Additionally, events occurring in real-time occur without substantial intentional delay. In contrast, as used herein, near real-time refers to outcomes occurring with some delay after a change in the inputs affecting the outcome. The delay may be intentional, such as due to a timer, or may be unintentional, such as due to latency within a network. 
         [0044]    The term processor, as used herein, refers to central processing units, microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASIC), logic circuits, and any other circuit or processor capable of executing the functions described herein. 
         [0045]    As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by processors  106  and  110 , including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program. 
         [0046]    As will be appreciated based on the foregoing specification, the above-described embodiments of the disclosure may be implemented using computer programming or engineering techniques including computer software, firmware, hardware or any combination or subset thereof, wherein the technical effect is real-time detection and monitoring of creep in moving objects. Any such resulting program, having computer-readable code means, may be embodied or provided within one or more computer-readable media, thereby making a computer program product, i.e., an article of manufacture, according to the discussed embodiments of the disclosure. The computer readable media may be, for example, but is not limited to, a fixed (hard) drive, diskette, optical disk, magnetic tape, semiconductor memory such as read-only memory (ROM), and/or any transmitting/receiving medium such as the Internet or other communication network or link. The article of manufacture containing the computer code may be made and/or used by executing the code directly from one medium, by copying the code from one medium to another medium, or by transmitting the code over a network. 
         [0047]    The above-described embodiments of a method and system of simultaneously measuring creep rate, crack, temperature and coating spallation in a real-time online prognostics and health monitoring (PHM) system provides a cost-effective and reliable means for providing a model based lifing prediction for moving objects while in service. As a result, the method and system described herein facilitate managing machinery assets in a cost-effective and reliable manner. 
         [0048]    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 the claims 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 languages of the claims.