The promotion of ignition in a supersonic H2-air mixing layer by laser-induced excitation of O2 molecules: Numerical study

A possibility of a considerable enhancement of ignition in a diffusion mode in a supersonic non-premixed H-2-air flow by means of the laser-induced excitation of O-2 molecules to the b(1)Sigma(.)(g) electronic state is investigated oil the base of numerical simulation. It is shown that for significant shortening the induction zone length it is sufficient to expose only a thin air layer (with thickness of 1-2 cm) to resonance laser radiation with a small input radiation energy 5 x 10(-3)-2 x 10(-2) J/cm(3). Even a small amount of radiation energy transmitted to the air flow makes it possible to arrange a stable combustion at a short distance (<= 1 m) from the irradiation region at a relatively low temperature of the air (T = 800 K), Shortening the induction zone length, in this case, is due to intensification of chain-branching via excitation of O-2 molecules by laser radiation and penetration of excited molecules into the shear layer. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.