Shock Wave Interaction with a Quasi-Elliptical Laminar Flame Front. Part I
A. A. Tyaktev, Yu. A. Piskunov, I. L. Bugaenko, P. V. Promyslov, M. E. Ignatyuk, E. S. Morozov, N. B. Anikin
All-Russian Scientific Research Institute of Technical Physics (VNIITF), Snezhinsk, Russia
Keywords: shock tube, shock wave, Mach number, Richtmyer-Meshkov instability, hydrogen, flame, contact boundary
Abstract
The interaction of a shock wave with a Mach number of up to 2.5 with a quasi-elliptical lean laminar flame front was studied in a vertically positioned shock tube with a square cross-section of 138 × 138 mm. The low-pressure chamber of the shock tube was filled with a combustible mixture of 8% H2, 18.4% O2, and 73.6% Ar to a pressure of 20 kPa, and the high-pressure chamber was filled with air or helium to a pressure of 100 or 400 kPa. Pulsed laser radiation, focused onto a point near the axis of the low-pressure chamber, ignited the combustible mixture, resulting in the formation of an isolated, slowly growing flame source-a bubble. This quasi-elliptical shape represented the contact boundary between media of different densities-light combustion products in a heavy unburned mixture. After the membrane separating the high- and low-pressure chambers was forced to rupture, a shock wave formed in the latter. Upon interaction with the flame source, it caused the development of a Richtmyer-Meshkov instability at its boundary. The unstable flow-a quasi-elliptical flame evolving into a toroidal vortex-was recorded through a pair of optical windows in opposite walls of the tube using high-speed schlieren videography at a frame rate of 50 kHz.
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