The Discharge Heated Channel Region Visualization based on Thermal Imaging Registration

Abstract

The paper presents the results of non-stationary thermal fields panoramic visualization, based on infrared thermography at the STDO-3 device (Shock Tube -Discharge -Optics) of the Lomonosov Moscow State University, Faculty of Physics. The main purpose of the work was to study the heating and cooling processes in a rectangular channel region under the influence of pulsed surface high-current discharges sliding over the dielectric surface, taking into account the supersonic flow in a channel with an obstacle. A pulsed surface discharge initiated in a 24x48 mm2 channel was studied in a quiescent air and in a high-speed flow behind the shock. When initiated in the flow (the delay time after the shock wave passage is up to 0.4 ms), the discharge plasma is localized mainly in the downwind region behind the reverse step (rectangular ledge). The discharge produces a pulsed (submicrosecond) contracted energy input with a 30 mm length in the localization zone. As a result, there is a short-term heating of the section of the channel wall adjacent to it. Using infrared (IR) thermographic imaging through the chamber quartz windows transparent to IR radiation, it was found that in the discharge chamber the discharge plasma noticeably heats the surface of the flat channel wall. Based on the obtained data of panoramic visualization with an exposure time up from 200 µs, we studied the channel walls cooling process both in quiescent air and in flow at different oncoming gas velocities -in the downwind region behind the dielectric ledge.