Open-Loop Performance of a Fast-Response, Actively Controlled Fuel Injector Actuator

This paper describes a study of the frequency dependence of a secondary combustion process response (SCPR) produced by a gaseous fuel injector actuator that was developed for the control of unstable combustor oscillations. Initially, two different approaches are presented for determining the SCPR; one uses pressure data measured in a short combustor and the other uses direct measurements of the global combustion zone radiation in a long combustor. The results of both approaches are in good agreement and show that the fuel injector actuator produces a signie cant SCPR over a 0 ‐ 800 Hz frequency range. The results also show that the phase lag of the SCPR increases almost linearly with the frequency, suggesting that a pure time delay plays a role in the mechanisms that control the SCPR. Additional studies presented in the paper investigate the dependence of the SCPR on the characteristics of the fuel actuator and the main injector geometry. These show that the SCPR strongly depends on the location of the modulated fuel stream injection relative to the location of the primary combustion process, and that a larger SCPR is obtained when the secondary, modulated, fuel stream is injected directly into the primary combustion zone.

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