Methods and systems to monitor health of rotor blades

Abstract

A system for monitoring health of a rotor is presented. The system includes a processing subsystem that generates a plurality of frequency peak values corresponding to two or more respective windows of signals by iteratively shifting the two or more respective windows of signals along delta times of arrival signals corresponding to a blade in the rotor, determines one or more resonant-frequency rotor speeds ranges of the blade by identifying rotor speeds corresponding to a subset of the plurality of frequency peak values, and monitors the blade to determine a presence of one or more defects in the blade during the resonant-frequency rotor speeds regions.

1 . A system for monitoring health of a rotor, comprising a processing subsystem, memory, and communications section that:
 generates a plurality of frequency peak values corresponding to two or more respective windows of signals by iteratively shifting the two or more respective windows of signals along delta times of arrival signals corresponding to a blade in the rotor;   determines one or more resonant-frequency rotor speeds regions of the blade by identifying rotor speeds corresponding to a subset of the plurality of frequency peak values; and   monitors the blade to determine a presence of one or more defects in the blade during the resonant-frequency rotor speeds regions.   
     
     
         2 . The system of  claim 1 , wherein the one or more resonant-frequency rotor speeds regions are a local maxima of the rotor speeds corresponding to the subset of the plurality of frequency peak values. 
     
     
         3 . The system of  claim 1 , wherein the processing subsystem further monitors the health of the blade during the resonant-frequency rotor speeds range of the blade. 
     
     
         4 . The system of  claim 1 , wherein the processing subsystem further determines the delta times of arrival signals based upon times of arrival generated during a start-up state of the rotor, a transient state of the rotor, a steady state of the rotor, over-speed state of the rotor, or combinations thereof. 
     
     
         5 . The system of  claim 1 , wherein a width of a first window of signals in the two more windows of signals is greater than a width of a second window of signals in the two or more window of signals. 
     
     
         6 . The system of  claim 1 , wherein the processing subsystem generates a plurality of first frequency peak values corresponding to a first window of signals in the two or more respective window of signals by:
 selecting a first subset of the delta times of arrival signals contained in the window of signals;   generating a first frequency peak value in the plurality of first frequency peak values based upon the first subset of the delta times of arrival signals;   shifting the first window of signals along the delta times of arrival signals to determine a shifted first window of signals;   selecting a second subset of the delta times of arrival signals contained in the shifted first window of signals;   generating a subsequent first frequency peak value in the plurality of first frequency peak values based upon the second subset of the delta times of arrival signals; and   determining the plurality of first frequency peak values by iteratively shifting the first window of signals along the delta times of arrival signals and selecting a respective subset of the delta times of arrival,   wherein the plurality of first frequency peak values is a subset of the plurality of frequency peak values.   
     
     
         7 . The system of  claim 6 , wherein the shifted first window of signals does not completely overlap the first window of signals. 
     
     
         8 . The system of  claim 6 , wherein the processing subsystem generates the first frequency peak value in the plurality of first frequency peak values based upon the first subset of the delta times of arrival signals by:
 determining a frequency signal corresponding to the first subset of the delta times of arrival signals by determining a Fourier transform of the first subset of the delta times of arrival signals;   selecting synchronous frequencies from the frequency signal; and   selecting a frequency having a highest amplitude in the synchronous frequencies; and   determining the first frequency peak value equal to the highest amplitude in the synchronous frequencies.   
     
     
         9 . A method for monitoring health of a rotor, comprising:
 generating a plurality of first frequency peak values by iteratively shifting a first window of signals along delta times of arrival signals corresponding to a blade in the rotor;   generating a plurality of second frequency peak values by iteratively shifting a second window of signals along the delta times of arrival signals corresponding to a blade;   processing a plurality of initial resultant values based upon the plurality of first frequency peak values and the plurality of second peak values;   determining whether one or more of the plurality of initial resultant values are less than a determined value; and   processing one or more resonant-frequency rotor speeds regions of the rotor by identifying rotor speeds corresponding to the plurality of second frequency peak values when the one or more of the plurality of resultant values are less than the determined value.   
     
     
         10 . The method of  claim 9 , wherein the one or more resonant-frequency rotor speeds regions are a local maxima of the rotor speeds corresponding to the subset of the plurality of second frequency peak values. 
     
     
         11 . The method of  claim 9 , wherein further comprising:
 generating a plurality of subsequent frequency peak values by iteratively shifting a subsequent window of signals along the delta times of arrival signals when the one or more of the plurality of resultant values are greater than the determined value;   generating a plurality of subsequent resultant values based upon the plurality of subsequent frequency peak values and a plurality of previous frequency peak values determined using a previous window of signals;   determining whether one or more of the plurality of subsequent resultant values are less than the determined value; and   processing the resonant-frequency rotor speeds of the rotor by identifying rotor speeds corresponding to the plurality of subsequent peak values when one or more of the plurality of subsequent resultant values are less than the determined value.   
     
     
         12 . The method of  claim 11 , wherein the previous window comprises the second window, and the plurality of previous peak values comprises the plurality of second peak values. 
     
     
         13 . The method of  claim 9 , further comprising determining the delta times of arrival signals based upon times of arrival generated during multiple rotor speeds of the rotor. 
     
     
         14 . The method of  claim 9 , wherein the delta times of arrival signals comprise delta times of arrival vectors comprising delta times of arrival mapped to respective rotor speeds of the rotor. 
     
     
         15 . The method of  claim 11 , wherein a width of the second window is greater than a width of the first window, and a width of the subsequent window is greater than the previous window. 
     
     
         16 . The method of  claim 15 , wherein the width of the first window, the width of the second window, the width of the previous window, and the width of the subsequent window comprises a rotor speed band. 
     
     
         17 . The method of  claim 9 , further comprising determining a plurality of resultant values based upon the plurality of first frequency peak values and the plurality of second frequency peak values by subtracting the plurality of second frequency peak values from the plurality of first peak values. 
     
     
         18 . The method of  claim 9 , wherein the one or more resonant frequency rotor speeds ranges comprise a subset of rotor speeds of the rotor that activate at least one resonant frequency of the blade. 
     
     
         19 . The method of  claim 9 , further comprising:
 generating resonant-frequency delta times of arrival by extracting a subset of the delta times of arrival determined based upon times of arrival generated during the resonant-frequency rotor speeds range of the rotor; and   determining one or more defects in the blade based upon the resonant-frequency delta times of arrival.   
     
     
         20 . The method of  claim 9 , further comprising:
 receiving times of arrival corresponding to the blade;   generating preprocessed times of arrival signals by applying at least one of a smoothening filtering technique and a median filtering technique to remove asynchronous signals from the times of arrival signals; and   determining the delta times of arrival signals based upon the preprocessed times of arrival signals and an expected time of arrival.