OPEN-LOOP PERFORMANCE OF A FAST-RESPONSE, ACTIVELY CONTROLLED FUEL INJECTOR ACTUATOR

This paper describes a study of the frequency dependence of a secondar y combustion process response (SCPR) produced by a gaseous fuel inject or actuator that was developed for the control of unstable combustor o scillations, Initially, two different approaches are presented for det ermining the SCPR; one uses pressure data measured in a short combusto r 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 sig nificant SCPR over a 0-800 Hz frequency range. The results also show t hat the phase lag of the SCPR increases almost linearly with the frequ ency, suggesting that a pure time delay plays a role in the mechanisms that control the SCPR. Additional studies presented in the paper inve stigate the dependence of the SCPR on the characteristics of the fuel actuator and the main injector geometry, These show that the SCPR stro ngly depends on the location of the modulated fuel stream injection re lative to the location of the primary combustion process, and that a l arger SCPR is obtained when the secondary, modulated, fuel stream is i njected directly into the primary combustion zone.