High-Speed 3-D Imaging of Ignition in a Circular Shock Tube

The primary reference fuels isooctane and n-heptane have been studied extensively in laboratory settings including rapid compression machines, shock tubes, jet-stirred reactors, and flames. These experimental investigations have been imperative to determining reaction rates and pathways to build comprehensive chemical kinetic mechanisms, but they do not provide information about the dynamics of ignition structure or behavior. In this work, high-speed three-dimensional images were taken at moderate temperatures and low pressures in a circular shock tube for the first time. This new imaging technique combines the end wall facing camera with a second high-speed camera that is placed perpendicular to the first, providing information on the ignition down the depth of the tube. With this novel technique, a better understanding of the three-dimensional exothermicity is achieved. Preliminary results show that the ignition for isooctane begins in the lower portion of the tube though ignition never completely consumes the entire test section. This work provides the next step in high-speed shock tube diagnostics and provides valuable insight into the ignition structure of the primary reference fuels.