Effect of Hydrodynamic Instabilities on the Development of Hydrogen-Air Flames

Abstract

The paper describes experimental investigation of hydrodynamic instabilities in lean hydrogen-air mixtures. The shock tube of 138 × 138 mm square section was used to experimentally study of evolution of flames in lean hydrogen-air mixtures. Obtained data demonstrate how flame development depends on the Rayleigh-Taylor instability in conditions of the superimposed artificial G-field.

Two modes of turbulent flame development are identified, i.e., convex and concave flames. Modes depend on the mixture concentration. Transition between modes takes place in the 16 ± 2% range of hydrogen concentration in the air. The convex flame mode is realized below the 16% hydrogen concentration in the air, and the concave flame mode is realized above the 16% hydrogen concentration. The 16% hydrogen concentration realizes the transition mode of the periodic oscillating flame. The flame development in the transition mode is driven by the Rayleigh-Taylor instability as far as superposition of the artificial G-field sharply intensifies development of the instability that preconditions the flame evolution in this mode.