Granted Patent B2

US 10,317,276 · App. 14/514,117 · Granted Jun 11, 2019

Abstract

Claims (123)

1. A method for monitoring for a turbomachine for a surge condition, comprising:

detecting a surge condition through vibration signals measured at at least one location in a turbomachine, wherein detecting a surge condition includes:

determining a ratio-metric indicator, R BR , by comparing a blade frequency band, Ω B , to a reference frequency band, Ω R , wherein determining the ratio-metric indicator R BR includes:

determining a time window length for vibration data acquisition;

identifying the blade frequency band Ω B and the reference frequency band Ω R ;

collecting vibration data with a known sampling rate with at least one accelerometer operable to generate the vibration signals representative of blade vibration and other vibration sources;

segmenting the vibration data into slices based on a time window;

determining a power spectrum of a given slice of vibration data;

obtaining respective residual spectrums from the power spectrum for the blade frequency band Ω B and the reference frequency band Ω R ; and

calculating the ratio-metric indicator, R BR , for the given slice of vibration data by comparing the power spectrum of the blade frequency band Ω B and the reference frequency band Ω R with the following equation:

R

BR

=

∑

ω

⋐

Ω

B

⁢



S

⁡

(

ω

)



2

∑

ω

⋐

Ω

R

⁢



S

⁡

(

ω

)



2

wherein S(ω) is the Discrete Fourier Transform, DFT, for a frequency, ω, of the given slice of vibration data;

calculating a surge score, SS, with the following equation:

SS

=

R

BR

-

R

μ

R

σ

wherein R μ is a sample mean of a set of ratio-metric indicators and R σ is a sample standard deviation of a set of ratio-metric indicators;

determining whether a surge condition exists based on the surge score SS; and

altering operation of the turbomachine if a surge condition is determined.

2. A method as recited in claim 1 , wherein determining whether a surge condition exists includes statistically analyzing populations of surge scores accumulated in different durations to monitor long term changes and drift.

3. A method as recited in claim 1 , wherein determining if a surge condition exists includes determining that the surge condition does exist if the ratio-metric indicator, R BR , deviates from the sample ratio mean, R μ , more than three times the ratio sample ratio standard deviation, R σ .

4. A method as recited in claim 1 , wherein determining whether a surge condition exists includes estimating the sample ratio mean, R μ , and the sample ratio standard deviation, R σ , from vibration signals obtained in-service as an in-system calibration process.

5. A method as recited in claim 1 , wherein determining the sample ratio mean, R μ , and the sample ratio standard deviation, R σ , includes determining ratio-metric indicator data for different speeds within an operating range under known normal conditions, collecting the ratio-metric indicator data, and calculating the sample ratio mean, R μ , and the sample ratio standard deviation, R σ , based on the collected ratio-metric indicator data.

6. A method as recited in claim 1 , wherein determining the ratio-metric indicator includes determining a respective fan rotation speed from the power spectrum.

7. A method as recited in claim 6 , wherein the step of determining the fan rotation speed includes rejecting data from which the fan rotation speed is considered to be uncertain.

8. A method as recited in claim 6 , wherein obtaining respective residual spectrums from the power spectrum includes removing peaks associated with the respective fan rotation speed and its harmonics in the blade frequency band Ω B and the reference frequency band Ω R .

9. A method as recited in claim 8 , wherein a width of a frequency window for the peaks to be removed is tied to the type of time window being used.

10. A turbomachinery surge monitoring system, comprising:

at least one sensor coupled to a compressor system; and

a processing unit coupled to the at least one sensor including a plurality of program instructions comprising:

program instructions to detect a surge condition through vibration signals measured at at least one location in a turbomachine, wherein program instructions to detect a surge condition include:

program instructions to determine a ratio-metric indicator, R BR , by comparing a blade frequency band, Ω B , to a reference frequency band, Ω R , wherein determining the ratio-metric indicator R BR includes:

determining a time window length for vibration data acquisition;

identifying the blade frequency band Ω B and the reference frequency band Ω R ;

collecting vibration data with a known sampling rate with the at least one sensor operable to generate the vibration signals representative of blade vibration and other vibration sources;

segmenting the vibration data into slices based on a time window;

determining a power spectrum of a given slice of vibration data;

obtaining respective residual spectrums from the power spectrum for the blade frequency band Ω B , and the reference frequency band Ω R ; and

calculating the ratio-metric indicator, R BR , for the given slice of vibration data by comparing the power spectrum of the blade frequency band Ω B and the reference frequency band Ω R with the following equation:

R

BR

=

∑

ω

⋐

Ω

B

⁢



S

⁡

(

ω

)



2

∑

ω

⋐

Ω

R

⁢



S

⁡

(

ω

)



2

wherein S(ω) is the Discrete Fourier Transform, DFT, for a frequency, ω, of the given slice of vibration data;

program instructions to calculate a surge score, SS, with the following equation:

SS

=

R

BR

-

R

μ

R

σ

wherein R μ is a sample mean of a set of ratio-metric indicators and Rσ is a sample standard deviation of a set of ratio-metric indicators;

program instructions to determine whether a surge condition exists based on the surge scoreSS; and

program instructions to alter operation of the compressor if a surge condition is determined.

11. A system as recited in claim 10 , wherein program instructions to determine whether a surge condition exists include program instructions to statistically analyze populations of surge scores accumulated in different durations to monitor long term changes and drift.

12. A system as recited in claim 10 , wherein program instructions to determine whether a surge condition exists include program instructions to determine that the surge condition does exist if the ratio-metric indicator, R BR , deviates from the sample ratio mean, R μ , more than three times the ratio sample ratio standard deviation, R σ .

13. A system as recited in claim 10 , wherein program instructions to determine whether a surge condition exists include program instructions to estimate the sample ratio mean, R μ , and the sample ratio standard deviation, R σ , from vibration signals obtained in-service as an in-system calibration process.

Assignments (9)