Morphology of Quasi-Direct-Current Discharges Collocated with Fuel Jets in a Supersonic Crossflow

Abstract

This study is focused on the morphology of a quasi-DC discharge generated concurrently with a jet of fuel injected normally into Mach 2 crossflow. It was observed that the filamentary plasma follows the local flowfield and localizes in the shear layer between the core flow and fuel jet. The details of behavior were explored by means of stereoscopic two-dimensional imaging with subsequent image processing and three-dimensional reconstruction of the plasma filament shape. On average, the plasma filament generated by the plasma-injection module has a total length over 100 mm and a plasma power on the order of 5 kW with a typical duration of 100 ms. Specifically, the discharge is located in a mixing layer, where the fuel–oxidizer ratio varies from down to stoichiometric ratio further downstream. Such a behavior of filamentary plasma promotes the fuel–air mixing, and is favorable for fuel ignition and flameholding. Tests were performed in the SBR-50 supersonic wind tunnel at the University of Notre Dame.