Method and device for the control of thermoacoustic instabilities or oscillations in a combustion system

Abstract

In a method for the control of thermoacoustic instabilities or oscillations in a combustion system ( 15 ), pressure oscillations and/or heat release oscillations in the combustion system ( 15 ), which are linked to the thermoacoustic instabilities, are measured, the resulting measurement signal is filtered, time-delayed and amplified, and, according to the filtered, delayed and amplified measurement signal, the fuel stream to or the combustion air for the combustion system ( 15 ) is modulated. In such a method, the use of more cost-effective modulation devices is achieved in that modulation takes place at a subharmonic of a dominant instability frequency in the combustion system ( 15 ).

1 . A method for the control of thermoacoustic instabilities or oscillations in a combustion system ( 15 ), in which pressure oscillations and/or heat release oscillations in the combustion system ( 15 ), which are linked to the thermoacoustic instabilities, are measured, the resulting measurement signal is filtered, time-delayed and amplified, and, according to the filtered, delayed and amplified measurement signal, the fuel stream to or the combustion air for the combustion system ( 15 ) is modulated, characterized in that modulation takes place at a subharmonic of a dominant instability frequency in the combustion system ( 15 ).  
     
     
         2 . The method as claimed in  claim 1 , characterized in that the filtering of the measurement signal takes place in a bandpass filter ( 11 ).  
     
     
         3 . The method as claimed in either of claims  1  and  2 , characterized in that modulation takes place at the 2nd subharmonic of a dominant instability frequency.  
     
     
         4 . A device for carrying out the method as claimed in  claim 1 , comprising means for measuring the pressure oscillations and/or heat release oscillations in the combustion system which are linked to the thermoacoustic instabilities, a bandpass filter ( 11 ), a delay and amplification unit ( 12 ), a modulation device ( 13 ) and a modulation channel ( 14 ) leading to the combustion system ( 15 ), which are arranged in a closed control loop ( 17 ), characterized in that the bandpass filter ( 11 ) is tuned to a subharmonic of a dominant instability frequency in the combustion system ( 15 ).  
     
     
         5 . The device as claimed in  claim 4 , characterized in that the bandpass filter ( 11 ) is tuned to the second subharmonic of a dominant instability frequency in the combustion system ( 15 ).  
     
     
         6 . The device as claimed in either of claims  4  and  5 , characterized in that the modulation device ( 13 ) comprises a high-speed valve and the modulation channel ( 14 ) is the fuel supply to the combustion system ( 15 ).  
     
     
         7 . The device as claimed in either of claims  4  and  5 , characterized in that the modulation device ( 13 ) comprises an acoustic driver and the modulation channel ( 14 ) is the combustion air supply to the combustion system ( 15 ).