Combustor oscillating pressure stabilization and method
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsRandall S. Gemmen, George A. Richards, Mui-Tong Joseph Yip, Edward H. Robey, Scott R. Cully, Richard E. Addis
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Abstract
High dynamic pressure oscillations in hydrocarbon-fueled combustors typically occur when the transport time of the fuel to the flame front is at some fraction of the acoustic period. These oscillations are reduced to acceptably lower levels by restructuring or repositioning the flame front in the combustor to increase the transport time. A pilot flame front located upstream of the oscillating flame and pulsed at a selected frequency and duration effectively restructures and repositions the oscillating flame in the combustor to alter the oscillation-causing transport time.
Claims22
Improved apparatus for the active control of unstable oscillation-producing combustion in a combustion system comprising a combustion chamber having a combustion zone with opposite end regions and means for introducing a first mixture of a fuel and oxidizer into the combustion zone at one end region thereof for the combustion of the fuel and oxidizer mixture, wherein the combustion of the fuel and oxidizer mixture forms an oscillating flame within the combustion zone at a location intermediate said end regions to effect the formation of dynamic pressure oscillations within the combustion chamber with the amplitude of said oscillations being dependent upon the degree of an in-phase relationship of the pressure wave produced by each oscillation with the periodic heat release produced by the combustion of the fuel in said fuel and oxidizer mixture, the improved apparatus defined by combustion oscillating pressure stabilizing means for reducing the amplitude of the pressure oscillations within the combustion chamber and comprising, chamber means communicating with said combustion chamber at said one end region thereof, fuel supplying means and oxidizer supplying means coupled to one of said chamber means and said combustion chamber for introducing thereinto at least one flowing stream of fuel and oxidizer for forming a second mixture thereof for producing a pilot flame within said combustion zone at said one end region thereof, and flow control means for intermittently interrupting the flow of at least one of the fuel from the fuel supplying means and the oxidizer from the oxidizer supplying means into the chamber means at a selected frequency and duration for intermittently and sequentially interrupting and establishing the flow of said at least one of the fuel from the fuel supplying means and the oxidizer from the oxidizer supplying means into said one of the chamber means and the combustion chamber for forming discrete mixtures of fuel and oxidizer from said second mixture which sequentially produce a pulsing pilot flame within said combustion zone for contact with the oscillating flame in the combustion zone, said control means providing a frequency and duration of interrupting and establishing the flow of said at least one of the fuel and the oxidizer adequate to provide the pulsing pilot flame with sufficient thermal energy within said combustion zone to effect the restructuring of the oscillating flame and thereby sufficiently repositioning the oscillating flame in the combustion zone to change the phase relationship of each pressure wave with the each periodic heat release away from an in-phase relationship therebetween for reducing the amplitude of the pressure oscillations.
In the operation of a combustion system comprising a combustion chamber having a combustion zone with opposite end regions and fuel and oxidizer delivery means for forming and introducing a first mixture of fuel and oxidizer into the combustion zone at one end region thereof for the combustion of the first mixture of the fuel and oxidizer whereby the combustion of the first mixture produces an oscillating flame within the combustion zone at locations intermediate said end regions to effect the formation of dynamic pressure oscillations within the combustion chamber at a frequency in the range of about 20 Hz to about 5000 Hz, wherein the amplitude of each of the oscillations being dependent upon the degree of in-phase relationship of the pressure wave produced by each oscillation with the periodic heat release produced by the combustion of the first fuel and oxidizer mixture, the method for reducing the amplitude of the oscillations within the combustion chamber by the steps comprising:
- forming a second mixture of fuel and oxidizer from separate flows of fuel and oxidizer, introducing the second mixture into said combustion zone at a location adjacent to said one end region thereof for producing a pilot flame within said combustion zone at said one end region thereof;
- and, intermittently interrupting the flow of at least one of the fuel and the oxidizer forming said second mixture or the flow of the second mixture to produce discrete charges of the second mixture for intermittently interrupting and establishing the pilot flame within the combustion zone at a rate and for a duration adequate to produce sufficient thermal energy within said combustion zone for sufficiently restructuring the flame in the combustion zone and thereby repositioning the flame in the combustion zone with respect to said location for changing the phase relationship of each said pressure wave to each periodic heat release with respect to said in-phase relationship and thereby reducing the amplitude of the pressure oscillations in said combustion chamber.
Dependencies are inferred from the claim text.