An operating turbine resonant blade monitor

Claim 1

An apparatus for detecting a vibrating blade of a rotating rotor in an operating turbine comprising: an acoustic sensor positioned on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide an acoustic signal from said received sound waves, said acoustic sensor positioned with respect to said rotor so that said blade approaches and departs from said acoustic sensor in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves, first means for obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, second means for sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a first and at a second angular velocity of said rotor, third means for averaging said samples obtained at respective rotor positions of said rotor revolving at said first angular velocity and revolving at said second angular velocity, fourth means for subtracting the averaged samples obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is removed, and fifth means for comparing the amplitude of said difference signal at respective rotor positions of said rotor with a threshold value whereby amplitudes above said threshold value are indicative of said vibrating blade.

Claim 3

A method for detecting a vibrating blade of a rotating rotor in an operating turbine having an acoustic sensor positioned on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide an acoustic signal from said received sound waves, said acoustic sensor positioned with respect to said rotor so that said blade approaches and departs from said acoustic sensor in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves comprising the steps of: obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a first and at a second angular velocity of said rotor, averaging said samples obtained at respective rotor positions of said rotor revolving at said first angular velocity and revolving at said second angular velocity, subtracting the averaged samples obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is removed, and comparing the amplitude of said difference signal at respective rotor positions of said rotor with a threshold value whereby amplitudes above said threshold value are indicative of said vibrating blade.

Claim 5

An apparatus for detecting a vibrating blade of a rotating rotor in an operating turbine comprising: first and second acoustic sensors positioned apart by a predetermined angle of rotation of said rotor on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide first and second acoustic signals from said received sound waves, said first and second acoustic sensors positioned with respect to said rotor so that said blade approaches and departs from said first and second acoustic sensors in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves, first means for obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, second means for sampling said first and second acoustic signals from said first and second acoustic sensors respectively to obtain samples as a function of respective rotor positions as said rotor completes a plurality of revolutions at a first and at a second angular velocity of said rotor, third means for averaging said samples of each of said first and second signals obtained at respective rotor positions of said rotor revolving at said first angular velocity and revolving at said second angular velocity, fourth means for subtracting the averaged samples of said first signal obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a first difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is removed, fifth means for subtracting the amplitudes of averaged samples of said second signal obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a second difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is reduced, sixth means for time shifting said first difference signal with respect to said second difference signal so that said first difference signal corresponds to the same respective position on the rotor as said second difference signal, seventh means for subtracting said first and second difference signals to provide a difference-difference signal whereby order-related background noise is further reduced, and eighth means for comparing the amplitude of said difference-difference signal at respective rotor positions of said rotor with a threshold value whereby amplitudes above said threshold value are indicative of said vibrating blades.

Claim 7

A method for detecting a vibrating blade of a rotating rotor in an operating turbine having: first and second acoustic sensors positioned apart by a predetermined angle of rotation of said rotor on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide first and second acoustic signals from said received sound waves, said first and second acoustic sensors positioned with respect to said rotor so that said blade approaches and departs from said first and second acoustic sensors in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves comprising the steps of: obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said first and second acoustic signals from said first and second acoustic sensors respectively to obtain samples as a function of respective rotor positions as said rotor completes a plurality of revolutions at a first and at a second angular velocity of said rotor, averaging said samples of each of said first and second signals obtained at respective rotor positions of said rotor revolving at said first angular velocity and revolving at said second angular velocity, subtracting the averaged samples of said first signal obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a first difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is removed, subtracting the amplitudes of averaged samples of said second signal obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a second difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is reduced, time shifting said first difference signal with respect to said second difference signal so that said first difference signal corresponds to the same respective position on the rotor as said second difference signal, subtracting said first and second difference signals to provide a difference-difference signal whereby order-related background noise is further reduced, and comparing the amplitude of said difference-difference signal at respective rotor positions of said rotor with a threshold value whereby amplitudes above said threshold value are indicative of said vibrating blades.

Claim 9

An apparatus for detecting a non order-related vibrating blade of a rotating rotor in an operating turbine comprising: an acoustic sensor positioned on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide an acoustic signal from said received sound waves, said acoustic sensor positioned with respect to said rotor so that said blade approaches and departs from said acoustic sensor in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves, first means for obtaining a reference signal indicative of rotor positions at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, second means for sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a plurality of angular velocities of said rotor, third means for averaging said samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities and for storing the averaged samples, fourth means for subtracting the averaged samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities from individual samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities to provide a difference signal sample at respective rotor positions of said rotor revolving at said plurality of angular velocities whereby non order-related background noise due to flow noise and non order-related vibrating blades is extracted, fifth means for determining the root mean square (RMS) of a plurality of difference signal samples at respective rotor positions of said rotor revolving at each angular velocity of laid plurality of angular velocities to form a root mean square difference sample at respective rotor positions of said rotor revolving at said plurality of angular velocities, sixth means for determining the root means square (RMS) of said root means square difference samples at respective rotor positions of said rotor revolving at each angular velocity of said plurality of velocities to form a root mean square running speed signal, seventh means for subtracting the amplitude of said root mean square running speed signal at each respective angular velocity from the amplitude of said root mean square difference samples at the same corresponding angular velocity to form reduced root mean square difference samples at respective rotor positions and angular velocities, eighth means for averaging over several revolutions said reduced root mean square difference samples at respective rotor positions of said rotor revolving at respective angular velocities, and ninth means for comparing said averaged and reduced root mean square difference samples at respective rotor positions of said rotor revolving at respective angular velocities with a threshold value whereby amplitudes above said threshold value are indicative of said non order-related vibrating blade.

Claim 10

A method for detecting a non order-related vibrating blade of a rotating rotor in an operating turbine having: an acoustic sensor positioned on a stationary member with respect to said rotor to receive sound waves emanating from said vibrating blade of said rotor as said blade rotates about said rotor axis and to provide an acoustic signal from said received sound waves, said acoustic sensor positioned with respect to said rotor so that said blade approaches and departs from said acoustic sensor in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves comprising the steps of: obtaining a reference signal indicative of rotor positions at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a plurality of angular velocities of said rotor, averaging said samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities and for storing the averaged samples, subtracting the averaged samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities from individual samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities to provide a difference signal sample at respective rotor positions of said rotor revolving at said plurality of angular velocities whereby non order-related background noise due to flow noise and non order-related vibrating blades is extracted, determining the root mean square (RMS) of a plurality of difference signal samples at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities to form a root mean square difference sample at respective rotor positions of said rotor revolving at said plurality of angular velocities, determining the root mean square (RMS) of said root mean square difference samples at respective rotor positions of said rotor revolving at each angular velocity of said plurality of velocities to form a root mean square running speed signal, subtracting the amplitude of said root mean square running speed signal at each respective angular velocity from the amplitude of said root mean square difference samples at the same corresponding angular velocity to form reduced root mean square difference samples at respective rotor positions and angular velocities, averaging over several revolutions said reduced root mean square difference samples at respective rotor positions of said rotor revolving at respective angular velocities, and comparing said averaged and reduced root mean square difference samples at respective rotor positions of said rotor revolving at respective angular velocities with a threshold value whereby amplitudes above said threshold value are indicative of said non order-related vibrating blade.

Claim 11

An apparatus for detecting an aerodynamic event in a operating turbine comprising: an acoustic sensor positioned on a stationary member with respect to said rotor of said turbine to receive sound waves emanating from and near the blades of a blade row of said rotor as said rotor rotates about said rotor axis to provide an acoustic signal from said received sound waves, first means for obtaining a reference signal indicative of rotor positions at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, second means for sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a plurality of angular velocities of said rotor, third means for averaging said samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities and for storing the averaged samples, fourth means for subtracting the amplitudes of averaged samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities from individual samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities to provide a difference signal sample at respective rotor positions of said rotor revolving at said plurality of angular velocities whereby non order-related aerodynamic events and background noise due to flow noise and blade vibration is extracted, and to provide an output signal at times said difference signal sample exceeds said predetermined value indicative of an aerodynamic event.

Claim 12

A method for detecting an aerodynamic event in an operating turbine having an acoustic sensor positioned on a stationary member with respect to said rotor of said turbine to receive sound waves emanating from and near the blades of a blade row of said rotor as said rotor rotates about said rotor axis to provide an acoustic signal from said received sound waves comprising the steps of: obtaining a reference signal indicative of rotor positions at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a plurality of angular velocities of said rotor, averaging said samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities and for storing the averaged samples, subtracting the amplitudes of averaged samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities from individual samples obtained at respective rotor positions of said rotor revolving at each angular velocity of said plurality of angular velocities to provide a difference signal sample at respective rotor positions of said rotor revolving at said plurality of angular velocities whereby non order-related aerodynamic events and background noise due to flow noise and blade vibration is extracted, and to provide an output signal at times said difference signal sample exceeds said predetermined value indicative of an aerodynamic event.

Claim 13

An apparatus for detecting differential nozzle wear between two or more nozzle sections in a high pressure turbine comprising: a first and second acoustic sensor positioned downstream of a rotating blade row and downstream of respective first and second nozzle sections of a turbine to receive sound waves emanating from said blade row and individual vibrating blades of said blade row rotating as part of a rotor about a rotor axis to provide an acoustic signal from said received sound waves, first means for obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, second means for sampling said first and second acoustic signals to obtain first and second samples as a function of rotor position as said rotor completes a plurality of revolutions at one of a plurality of angular velocities of said rotor, third means for averaging said first and second samples of said first and second acoustic signals obtained at respective rotor positions of said rotor revolving at said angular velocity, fourth means for phase shifting said second samples of said second acoustic signal whereby said first samples of said first acoustic signal and said second samples of said second acoustic signal correspond to the same place on the rotor, and fifth means for subtracting said first samples of said first acoustic signal from said second samples of said second acoustic signal to provide a difference signal indicative of nozzle wear between said first and second nozzles.

Claim 14

A method for detecting differential nozzle wear between two or more nozzle sections in a high pressure turbine having: a first and second acoustic sensor positioned downstream of a rotating blade row and downstream of respective first and second nozzle sections of a turbine to receive sound waves emanating from said blade row and individual vibrating blades of said blade row rotating as part of a rotor about a rotor axis to provide an acoustic signal from said received sound waves comprising the steps of obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said first and second acoustic signals to obtain first and second samples as a function of rotor position as said rotor completes a plurality of revolutions at one of a plurality of angular velocities of said rotor, averaging said first and second samples of said first and second acoustic signals obtained at respective rotor positions of said rotor revolving at said angular velocity, phase shifting said second samples of said second acoustic signal whereby said first samples of said first acoustic signal and said second samples of said second acoustic signal correspond to the same place on the rotor, and subtracting said first samples of said first acoustic signal from said second samples of said second acoustic signal to provide a difference signal indicative of nozzle wear between said first and second nozzles.

Claim 16

A method for measuring the order-related torsional resonant shaft vibration of a rotor shaft in an operating turbine having an acoustic sensor positioned on a stationary member with respect to said rotor to receive sound waves emanating from vibrating blades of said rotor as said blades rotate about said rotor axis and to provide an acoustic signal from said received sound waves, said acoustic sensor positioned with respect to said rotor so that said blades approach and depart from said acoustic sensor in the course of one rotation of said rotor about said rotor axis thereby imparting a Doppler effect to said received sound waves comprising the steps of: obtaining a reference signal indicative of rotor position at least once each time said rotor completes a revolution about said rotor axis and for determining the angular velocity of said rotor, sampling said acoustic signal to obtain samples as a function of rotor position as said rotor completes a plurality of revolutions at a first and at a second angular velocities of said rotor,    averaging said samples obtained at respective rotor positions of said rotor revolving at said first angular velocity and revolving at said second angular velocity, subtracting said averaged samples obtained at respective rotor positions of said rotor revolving at said first and at said second angular velocity to provide a difference signal at respective rotor positions of said rotor whereby order-related background noise due to other blades having nonuniformity in angular position on the rotor is removed, and detecting a sine wave modulation in the amplitude of said difference signal as a function of one revolution of said rotor shaft and for providing a signal indicative of torsional resonant shaft vibration of said rotor shaft at times said sine wave modulation is detected.