Systems and methods for suppressing thermoacoustic instabilities of flames

Abstract

Systems and methods of operating a combustion burner to affect a flame output from the combustion burner are described. The combustion burner is configured to output the flame from a face of the burner defining a gas flow path in a direction away from the burner, with a positive electrode positioned within or adjacent to the flame, and a negative electrode positioned within or adjacent to the flame. The method includes generating a flame from the burner, generating a first electric field between the positive electrode and the negative electrode, thereby generating a modified flame, and combining a second electric field with the first electric field to affect the modified flame.

I/We claim: 
     
         1 . An apparatus, comprising:
 (a) a combustion burner configured to output a flame and a gas flow from a face of the burner, wherein the gas flow defines a gas flow path in a direction away from the burner;   (b) a first conductive element positioned within the flame;   (c) a second conductive element positioned across the face of the burner;   (d) a power source;   (e) a positive electrode and a negative electrode each coupled with the power source, wherein the positive electrode is electrically coupled with the first conductive element and the negative electrode is electrically coupled with the second conductive element;   wherein the positive electrode and the negative electrode are selectively operable to apply a first electric signal to the flame to form a modified flame having a modified flame characteristic relative to the flame; and   wherein the positive electrode and the negative electrode are selectively operable to apply a second electric signal, simultaneous with the first electric signal, to the flame to affect a characteristic of the modified flame.   
     
     
         2 . The apparatus of  claim 1 , wherein the first electric signal defines a first signal frequency, wherein the second electric signal defines a second signal frequency, wherein the second signal frequency is greater than the first signal frequency. 
     
     
         3 . The apparatus of  claim 1 , wherein the second electric signal includes a periodic voltage signal. 
     
     
         4 . The apparatus of  claim 3 , wherein the periodic voltage signal includes one of a sinusoidal signal, a pulse-width modulation (PWM) signal, or a pulse train signal. 
     
     
         5 . The apparatus of  claim 1 , wherein the first electric signal defines a first signal amplitude, wherein the second electric signal defines a second signal amplitude, wherein the second signal amplitude is greater than the first signal amplitude. 
     
     
         6 . The apparatus of  claim 1 , wherein the first electric signal is oriented parallel to the gas flow path, wherein the first electric signal is oriented in an opposite direction to the gas flow path. 
     
     
         7 . The apparatus of  claim 1 , further comprising:
 (a) a sensor configured to determine an acoustic characteristic of the combustion burner and output a data signal based upon the acoustic characteristic; and   (b) a data processor communicatively coupled with the sensor and the power source, wherein the data processor is configured to receive the data signal and selectively operate the power source to modify at least one of the first electric signal and the second electric signal based upon the data signal.   
     
     
         8 . The apparatus of  claim 7 , wherein the data processor is configured to compare the acoustic characteristic to a pre-determined acoustic characteristic, wherein the data processor is configured to modify at least one of the first electric signal and the second electric signal to thereby achieve an improved acoustic characteristic. 
     
     
         9 . The apparatus of  claim 7 , wherein the second electric signal defines a signal frequency, wherein the data processor is configured to compare the acoustic characteristic to a pre-determined acoustic characteristic, wherein the data processor is configured to modify the signal frequency of the second electric signal to thereby achieve an improved acoustic characteristic. 
     
     
         10 . A method of operating a combustion burner to affect a flame output from the combustion burner, wherein the combustion burner is configured to output the flame from a face of the burner defining a gas flow path in a direction away from the burner, wherein a positive electrode is positioned within or adjacent to the flame, and a negative electrode is within or adjacent to the flame, the method comprising:
 (a) generating a flame from the burner;   (b) generating a first electric field between the positive electrode and the negative electrode, thereby generating a modified flame;   (c) combining a second electric field with the first electric field to affect the modified flame, wherein the second electric field selectively generates pinch-off and pocket formation of the modified flame.   
     
     
         11 . The method of  claim 10 , wherein generating the first electric field between the positive electrode and the negative electrode includes generating the first electric field in an orientation parallel to the gas flow path and in an opposite direction relative to the flow path. 
     
     
         12 . The method of  claim 10 , wherein the first electric field includes a first signal frequency, wherein the second electric field includes a second signal frequency, the method comprising generating the second electrical field having a second signal frequency that is greater than the first signal frequency. 
     
     
         13 . The method of  claim 10 , comprising generating the second electrical field having a a periodic voltage signal. 
     
     
         14 . The method of  claim 13 , generating the second electrical field having a one of a sinusoidal signal, a pulse-width modulation (PWM) signal, or a pulse train signal. 
     
     
         15 . The method of  claim 10 , wherein the first electric field includes a first signal amplitude, wherein the second electric field includes a second signal amplitude, the method comprising generating the second electrical field having a second signal amplitude that is greater than the first signal amplitude. 
     
     
         16 . The method of  claim 10 , wherein the second electric field defines a signal frequency, the method comprising:
 comparing, with a data processor, an acoustic characteristic of the flame to a pre-determined acoustic characteristic of the flame; and   modifying the signal frequency of the second electric field to achieve an improved acoustic characteristic of the flame.   
     
     
         17 . A method of operating a combustion burner, wherein the combustion burner is configured to output a flame and a gas flow from a face of the burner defining a gas flow path in a direction away from the burner, wherein a conductive element is positioned across the face of the burner, a positive electrode is positioned within the flame, and a negative electrode is coupled with the conductive element, the method comprising:
 (a) generating a flame from the burner;   (b) applying a first electric signal and a second electric signal to the flame simultaneously, wherein the first and second electric signals define different frequencies;   (c) measuring an acoustic characteristic of the burner;   (d) comparing the acoustic characteristic to a pre-determined acoustic characteristic; and   (e) based upon the comparison, selectively modifying at least the first or second electric signal induced between the positive electrode and the negative electrode to modify the flame.   
     
     
         18 . The method of  claim 17 , wherein the acoustic characteristic includes an acoustic pressure. 
     
     
         19 . The method of  claim 17 , wherein selectively modifying at least the first or second electric signal includes adjusting a signal frequency of the second electric signal to modify the flame. 
     
     
         20 . The method of  claim 17 , wherein applying the second electric signal to the flame includes generating a periodic voltage signal.