Self-excited transverse combustion instabilities in a high pressure lean premixed jet flame

Injector-coupled transverse instabilities in a multi-element premixed combustor

“…In contrast, for a combustor with a single, non-compact flame with an injector design similar to the current experiment, Buschhagen et al. 36 showed that the dominant excited mode, either axial or transverse, and the amplitude of the instabilities were sensitive to the operating condition. The change in the local interaction between the intrinsic jet hydrodynamics and the flame resulted in this sensitivity.…”

“…The design maintains similarities with several other rocket and gas turbine combustion experiments studied at Purdue University. 35,[37][38][39][40] VIPER-M was designed to promote self-excited, transverse instabilities while operating at a mean chamber pressure up to 825 kPa with an inlet air temperature up to 510 K. The multi-element configuration supports jet-stabilized combustion with flames anchored at the injector-exit plane (y ¼ 0), as labeled in Figure 1. This injector configuration is similar to the FLOX V R combustion experiments, which have been widely studied.…”

“…This corresponds to a jet velocity of 108 m/s at the exit of the injectors, which is within the range of values used in similar jet-stabilized combustion experiments. 34,35,42 Based on the combustion product gas properties for these inlet conditions and the chamber width, the expected fundamental transverse mode frequency is 1860 Hz. In the first injector configuration, the injector length ( L ) was designed to support a half-wave pressure mode shape in the axial direction at the 1T frequency.…”

“…Therefore, it is important to study how the transverse coupling mechanisms and flame response change as operation approaches realistic engine conditions. One of the few laboratory-scale experiments investigating HF instabilities in a gas turbine configuration at elevated pressure was performed by Buschhagen et al 35,36 This work characterized self-excited, transverse instabilities in a single-element, premixed jet flame that was acoustically non-compact. Changes to the overall flame shape and jet hydrodynamics were shown to influence the ability of flame-vortex coupling to drive transverse instabilities.…”

“…This allows for comparison with single-element experiments, which typically have noncompact flames with respect to the transverse acoustic wavelength and intra-element dynamics that dominate the flame-acoustic interactions. 35 For this purpose, a canonical experiment was developed and tested up to 825 kPa with injection Reynolds number of O 10 5 ð Þ . The resulting specific power density was 25-33 MW/ m 2 -bar (based on the combustor cross-sectional area), which is similar to the maximum value of 23 MW/m 2bar reported by Lammel et al 34 Variation of the injector length resulted in multiple self-excited instability regimes that are studied using high-speed CH* chemiluminescence and pressure measurements.…”