SUMMARY

The jet in crossflow (JICF) is a geometrically simple but remarkably effective configuration for mixing two dissimilar fluid streams. Staged fuel combustors found in advanced gas turbine engines rely on JICF-style injection systems to introduce additional fuel and stabilize a secondary combustion zone downstream of a lean premixed main burner. The vitiated crossflows in these systems are inherently unsteady and experience coherent thermo-acoustic oscillations. The fluctuating crossflow affects both the time-averaged and the dynamic behavior of the JICF. These effects are not well understood but have important implications for flow control and combustor operability. We present time-resolved chemiluminescence and particle image velocimetry (PIV) results obtained using a new facility designed and fabricated to study jet dynamics in vitiated crossflows at temperatures up to 1900 K. We analyze time-averaged and dynamic characteristics of non-reacting and reacting JICF at two different crossflow temperatures and a range of momentum flux ratios from 5 to 25. Finally, an experimental approach is proposed to study the response of JICF to crossflow forcing. The proposed parameter space for this study encompasses both non-reacting and reacting JICF at different jet-to-crossflow momentum flux ratios, jet-to-crossflow density ratios, crossflow temperatures, forcing frequencies, and forcing amplitudes. Simultaneous time-resolved OH* chemiluminescence, PIV, and dynamic pressure measurements will be used to quantify the jet response. Hydrodynamic stability theory, modal decomposition methods, and reduced order modeling will be used to interpret the results.