Apparatus to estimate the root means square value or the amplitude of limit cycle oscillations in systems that encounter oscillatory instabilities and methods thereof

Patent metadata

Field	Value
Publication number	US-11650552-B2
Application number	US-201816605054-A
Country	US
Kind code	B2
Filing date	Apr 19, 2018
Priority date	Apr 27, 2017
Publication date	May 16, 2023
Grant date	May 16, 2023

Abstract

Oscillatory instabilities are ubiquitous of systems, and these usually arise out of low amplitude aperiodic oscillations. These oscillatory instabilities generally affect the performance and the lifespan of systems in an adverse manner. An apparatus and a method are disclosed here to estimate the rms value or the amplitude of limit cycle oscillations for control of the oscillatory instability.

First claim

What is claimed is:

1. A system to determine impending oscillatory instabilities in a device, the system comprising:
a sensor to detect an oscillatory variable;
a signal conditioner connected to the sensor to condition and filter electrical signals from the sensor;
an analog to digital convertor to convert electrical signals received from the signal conditioner;
an amplitude estimator that estimates a root means square (rms) value or amplitude of limit cycle oscillations;
a processing unit connected to the amplitude estimator compares a predicted oscillation amplitude or rms value with a threshold value or to compare a measured signal obtained from the said analog to digital converter with the predicted oscillation amplitude or rms value,
characterized in that:
the amplitude estimator continuously obtains segments of data associated with one or more parameters measured from the device in real time, wherein each of the segments of data comprises single input time series data with fixed length such that the segments collectively comprise multiple contiguously labelled time series of data, wherein each segment of data is acquired by varying control parameters of the device over time during a stable operation;
the amplitude estimator estimates amplitude or rms value of the impending limit cycle oscillations in real time by modelling the device exhibiting oscillatory instability as a kicked oscillator based on the continuously obtained segments of data from the device during the stable operation; and
the processing unit generates times the kicked oscillator is kicked using the parameters measured from the device and obtains the strength of kicking by determining a mean of all the obtained estimates of amplitude or rms value of the limit cycle oscillations; and

a controller that controls the oscillatory variable to alter one or more operating inputs to restore stable operation of the system based on estimated amplitude.

2. The system as claimed in claim 1 wherein the parameters include but not limited to aperiodic probability, dominant time-period, the RMS value or amplitude of the limit cycle oscillations, and kicking times and kicking strength measured from the system.

3. The system as claimed in claim 1 , wherein the device is a system with turbulent flow exhibiting oscillatory instabilities.

4. The system as claimed in claim 1 , wherein the operating inputs altered to restore stable operation include one of air or fuel flow rate, degree of premixing or preheat temperature of air or fuel, length of the flame, fuel splitting, distribution of fuel or fuel injection or flame length or their combinations.

5. A method of estimating root means square (rms) or amplitude of limit cycle oscillations for systems susceptible to oscillatory instabilities comprising the steps of:
a. detecting an oscillatory variable causing the limit cycle oscillations using a sensor mounted on the system;
b. converting a signal detected as part of said detecting an oscillatory variable into digital signals in an analog-digital convertor;
c. continuously obtaining segments of data associated with one or more parameters measured from the device in real time by an amplitude estimator, wherein each of the segments of data comprises single input time series data with fixed length such that the segments collectively comprise multiple contiguously labelled time series of data, wherein each segment of data is acquired by varying control parameters of the device over time during a stable operation;
d. estimating the rms value or the amplitude of the impending limit cycle oscillations in real time by modelling the device exhibiting oscillatory instability as a kicked oscillator based on the continuously obtained segments of data from the device during the stable operation by an amplitude estimator;
e. comparing the estimated value of the rms or the amplitude of limit cycle oscillations with a threshold value for the system, or comparing the measured signal obtained from the said analog to digital converter with the estimated amplitude or rms value;
f. obtaining the strength of kicking by determining the mean of all the obtained estimates of amplitude or rms value of the limit cycle oscillations;
g. creating appropriate instructions for controlling the system parameters of one or more of the systems susceptible to oscillatory instabilities to restore stable operation; and
h. restoring the stability of one more of the systems susceptible to oscillatory instabilities by suitably adjusting the system parameters.

6. The method as claimed in claim 5 , wherein the rms value or the amplitude of the limit cycle oscillations is estimated by modelling one or more of the systems exhibiting oscillatory instabilities as a kicked oscillator, generating the times at which the oscillator is kicked using one or more parameters measured from the system, and obtaining the strength of kicking.

7. The method as claimed in claim 5 , wherein the parameters measured or estimated from one or more of the systems exhibiting oscillatory instabilities comprises aperiodic probability, dominant time-period, the RMS value or amplitude of the limit cycle oscillations, and kicking times and kicking strength.

8. The method as claimed in claim 5 , wherein the controller is configured to alter one or more operating inputs to restore stable operation of one or more of the systems exhibiting oscillatory instabilities.

9. The method as claimed in claim 5 , wherein the one or more of the systems exhibiting oscillatory instabilities is a system with turbulent flow exhibiting oscillatory instabilities such as combustion system, aero-elastic system or aero-acoustic system.

10. The method as claimed in claim 5 , wherein the operating inputs altered to restore stable operation include but not limited to any of air or fuel flow rate, degree of premixing or preheat temperature of air or fuel, length of the flame, fuel splitting, distribution of fuel or fuel injection or flame length or their combinations.

Assignees

• Indian Inst Tech Madras
• Indian Institute Of Tech

Inventors

• Nair Sujith Raman Pillai Indusekharan
• Seshadri Akshay
• Pavithran Induja

Classifications

• G01H1/08 Primary

  Amplitude · CPC title

• G01H1/00

  Measuring {characteristics of} vibrations in solids by using direct conduction to the detector (G01H9/00, G01H11/00 take precedence) · CPC title

• G05B13/048 Primary

  using a predictor · CPC title

• G01M15/14

  Testing gas-turbine engines or jet-propulsion engines · CPC title