Analysis of a Pseudo-active Approach for the Control of Thermoacoustic Instabilities

This work describes a first characterization study of a novel approach, named 'pseudo-active' instability control (PAIC), which might afford the versatility of active control, but with much simpler hardware requirements. The objective is to spontaneously induce oscillations in pilot fuel injection due to the pressure fluctuations in the combustion chamber, in order to produce effects similar to those obtained with active instability control methods. For optimized designs, this interaction could be exploited to damp pressure fluctuations in gas-turbine combustors. The experimental study was performed for different PAIC configurations and under situations of strong, self-sustained pressure fluctuations. The results obtained show good potentialities of the system proposed, and also revealed purely acoustic interactions between the burner and the pilot line, which superimposed on the interaction between the pilot and main flames. Overall, this work provides novel results on the, previously unexplored, influence of the acoustic properties of the pilot fuel injection on the limit cycle as well as first evidence on the rationale and benefits that could be derived from the so-called PAIC strategy.