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Structures and Extinctions in Hydrogen Non-Premixed Lifted Turbulent Jet Flame

Two dimensional direct numerical simulation of H2-air lift-off flame with height jet velocity is performed with full chemical kinetics. Hydrogen non-premixed turbulent jet flame structure is obtained and its quenching process at the lifted position is examined. Introduction Non-premixed as well as premixed jet flame is widely used in industrial combustion systems. Flows in these combustion devices are turbulence and the study of their detailed mechanisms is required for efficiency and safety. Fundamental research of flame structure, lift-off, blow off, and quenching, is indispensable for practical combustors as well as applied research. Many works have been done on those fundamental subjects [1-5]. However, as far as the issue of turbulence is concerned, there are always difficulties for theoretical and numerical studies. Recently, with the increase of computational power, the direct numerical simulation (DNS) has become easier to handle than the time when Kim calculate channel flow and become an essential tool to understand combustion problems [6]. The aim of this study is an investigation of the unsteady behavior of lift-off jet flame in two dimensions using DNS. Chemical reactions are considered H2-air system with full kinetics. Particular interest is dedicated to quenching process of the flame. Numerical Formulations A lifted H2 jet flame under consideration was shown in Fig.1. The flame obeys the conservation of the mass, momentum, energy, and species mass for reacting flow [7]. The mixture is regarded as ideal gas and the state relation holds. Thermodynamic and transport properties are based on CHEMKIN package [8]. As for the chemical reaction, 19 elementary reactions with 9 species of H2 O2 O H HO2 H2O2 H2O , and N2 are considered [9].