The promotion of ignition in a supersonic H 2–air mixing layer by laser-induced excitation of O 2 molecules: Numerical study

• Published in: Combustion and flame Vol. 156; no. 8; pp. 1641 - 1652
• Main Authors: Starik, A.M., Titova, N.S., Bezgin, L.V., Kopchenov, V.I.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.08.2009
• Subjects: Chain-branching reactions; Combustion; Excited molecules; Laser radiation; Combustion; Excited molecules; Chain-branching reactions; Laser radiation
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2009.04.012

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 Σ g + electronic state is investigated on 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 × 10 −3–2 × 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.