• Dr. Adam Steinberg
  • German Aerospace Center (DLR) Institute of Combustion Technology
  • 1010 Torgersen Hall
  • 10:05 a.m.

The past several years have seen a great increase in gas turbine engine deployments, along with a concurrent demand for drastically reduced pollutant emissions. Effectively meeting these increasingly stringent emission targets has been hampered by the tendency of low-emission engines to exhibit self-excited and self-destructive thermo-acoustic instabilities. Such instabilities are driven by a complex flow-combustion-acoustic coupling, the prediction of which is not yet possible. Control schemes are therefore applied as a redesign or retrofit when unstable conditions are encountered in late-stage testing of new engines, at a great expense of time and money. Furthermore, since the instabilities are not fundamentally solved, they have a tendency to reappear when minor design upgrades or changes in fuel composition are made. However, our understanding and management of thermo-acoustic instabilities can be greatly aided by recent advances in high-repetition-rate laser-based flow and combustion diagnostics. This seminar will discuss a current research program that uses a suite of such diagnostics to better understand and predict how thermo-acoustic instabilities are excited in low-emission gas turbine combustors. A detailed analysis of the flow-combustion-acoustic coupling will be presented for a variety of swirl-stabilized flames. Due to the temporal resolution afforded by the diagnostics, quantification of previously unobserved and thermo-acoustically coupled flow-flame interaction dynamics is possible.  Furthermore, by simultaneously resolving multiple periodic processes, the high-speed measurements provide a three-dimensional map of how energy is transferred between heat release and acoustic oscillations through such interactions. The understanding of thermo-acoustic energy transfer gained from this analysis has the potential not only to aid in avoiding unstable states, but to allow tailoring of combustors such that natural flow features provide an effective means of damping instabilities.