| 摘要 |
<p>A method of operating a combustor for a turbine includes variably staging of fuel to the fuel nozzles in the turbine combustor such that a stable and quiet transfer from the diffusion mode of operation to the premixed mode of operation in a dry low NOx combustion system can be accomplished. Fundamentally, the present method provides for the variable control of the flow of fuel through the nozzles to the combustion zone downstream of the nozzles to provide an asymmetric flow of fuel across the combustor during the transition and during portions of the premixed mode of operation. That is, the present method affords an imbalance of fuel across the combustor, i.e., an uneven flow of fuel through the nozzles in an annular array whereby the fuel/air ratio among the nozzles is different from one another. This occurs during both the diffusion mode of operation at the initiation of the transition, during transition and during premixed mode of operation at less than full power. By increasing the percentage of premixed fuel to one or more premix nozzles during transition from diffusion to premixed mode of operation and/or during steady state operation in a premixed mode, the local equivalence ratio at the one or more fuel nozzle exits is higher than at the exit of the remaining nozzles, resulting in a more stable flame at the one or more nozzles. So one nozzle has a higher fuel/air ratio than any one of the remaining other nozzles. Hence, this first nozzle runs rich and stable and stabilizes the remaining other nozzles by creating an asymmetric heat release in the head end of the combustor, which inhibits the onset of strong dynamic pressure oscillations in the combustor. Once established in steady state premixed mode, the fuel split can be equalized among the premixed nozzles. <MATH></p> |
