Experiments on Plasma-Assisted Combustion in a Supersonic Flow: Optimization of Plasma Position in Relation to the Fuel Injector


K.V. Savelkin, D.A. Yarantsev (Russian Academy of Sciences)
S.B. Leonov (Russian Academy of Sciences) (University of Notre Dame)

The results of an experimental study of plasma-induced ethylene ignition and flameholding in a supersonic model combustor are presented in the paper. The experimental combustor has a cross-section of 72 mm (width) x 60 mm (height) and length of 600 mm. The fuel is directly injected into the supersonic airflow through wall orifices. The flow parameters are: Mach number M=2, static pressure Pst=160-250 Torr, stagnation temperature T0=300 K and total air flow rate Gair≤0.9 kg/s. The near-surface quasi-DC electrical discharge is generated by a series of flush-mounted electrodes, providing an electrical power deposition of Wpl=3-24 kW. The scope of the experiments includes the characterization of the discharge interacting with the main flow and fuel injection jet, a parametric study of ignition and flame front dynamics and a comparison of three plasma generation schemes: the first two examine upstream and downstream locations of plasma generators in relation to the fuel injectors. The third pattern follows a novel approach of a combined mixing/ignition technique, where the electrical discharge is distributed along the fuel jet, starting within the fuel injector. The last pattern demonstrates a significant advantage in terms of the flameholding limit. The experiments are supported by gas temperature and H2O vapor concentration measurements by Tunable Diode-Laser Absorption Spectroscopy (TDLAS). The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of the transition regime in a dual-mode scramjet and during off-design operation.

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