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-2021132555-A1
Application number	US-201816605054-A
Country	US
Kind code	A1
Filing date	Apr 19, 2018
Priority date	Apr 27, 2017
Publication date	May 6, 2021
Grant date	—

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 predicts the rms value or amplitude of the limit cycle oscillations; a processing unit connected to the amplitude estimator to compare the predicted oscillation amplitude or rms value with a threshold value, and/or to compare the measured signal obtained from the said analog to digital converter with the predicted amplitude or rms value, characterized in that the amplitude or rms value of the limit cycle oscillations is estimated by modelling the system exhibiting oscillatory instability as a kicked oscillator, generating the times at which oscillator is kicked using one or more parameters measured from the system, and obtaining the strength of kicking; and a controller to control the oscillatory variable based on the instructions received from the processing unit through the control device connected to the system. 25

2 . The system as claimed in claim 1 wherein the parameters measured or estimated from the system include aperiodic probability, dominant time-period, the RMS value or amplitude of the oscillation, kicking times and kicking strength.

3 . The system as claimed in claims 1 wherein the controller is configured to alter one or more operating inputs to restore stable operation of the system.

4 . The system as claimed in claim 1 , wherein the system is a system with turbulent flow exhibiting oscillatory instabilities such as combustion system, aero-elastic system or aero-acoustic system.

5 . The system as claimed in claims 3 , wherein the operating inputs are altered to restore stable operation include but not limited to 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 and the like or their combinations.

6 . A method of estimating rms or amplitude of limit cycle oscillations for systems susceptible to oscillatory instabilities comprising the steps of:
a. detecting an oscillatory variable causing the oscillations using a sensor mounted on the system; b. converting the signal into digital signals in an analog-digital convertor; c. estimating the rms value or the amplitude of the limit cycle oscillations using an amplitude estimator from data obtained from the said analog-digital convertor d. comparing the estimated value of the rms or the amplitude of limit cycle oscillations with a threshold value for the system, and/or to compare the measured signal obtained from the said analog to digital converter with the predicted amplitude or rms value; e. and create appropriate instructions for controlling the system parameters to restore stable operation; and f. restoring the stability of the system by suitably adjusting the system parameters.

7 . A method as claimed in claim 6 wherein the rms value or the amplitude of the limit cycle oscillations is estimated by modelling the system exhibiting oscillatory instability 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.

8 . A method as claimed in claims 6 wherein the parameters measured or estimated from the system include aperiodic probability, dominant time-period, the RMS value or amplitude of the oscillation, kicking times and kicking strength.

9 . A method as claimed in claims 6 , wherein the controller is configured to alter one or more operating inputs to restore stable operation of the system.

10 . A method as claimed in claims 6 , wherein the system is a system with turbulent flow exhibiting oscillatory instabilities such as combustion system, aero-elastic system or aero-acoustic system.

11 . A method as claimed in claims 6 , wherein the operating inputs altered to restore stable operation include but not limited to 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 and the like or their combinations.

Assignees

• Indian Inst Tech Madras

Inventors

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

Classifications

• 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

• G01H1/08 Primary

  Amplitude · CPC title

• G01M15/14

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