The characteristics of flame propagation in hydrogen/oxygen mixtures

Abstract

The extreme explosiveness and high flame velocity of hydrogen challenge its application. Overcoming these challenges requires improving the fundamental flame characteristics of H 2 /O 2 mixtures. In this study, the propagation characteristics of H 2 /O 2 flames are investigated. The laminar burning velocity (LBV) is evaluated using nonlinear extrapolation. The empirical relations of LBV are given with the equivalence ratio (ER) and initial mixture pressure (IMP). The LBV increases first and then decreases as the ER increases and reaches its maximum value at the ER slightly higher than 1.0 (φ = 1.1–1.2). The LBV increases monotonically with increasing IMP. The critical instability radius and Markstein length increase as the ER increases, while decreasing with the IMP increase. The flame thickness decreases significantly with increasing IMP. The flame remains stable and smooth throughout the propagation process for all examined ERs only at the lower IMPs of 0.1 atm and 0.3 atm. • The LBV is evaluated by using the nonlinear extrapolation method owning to the high stretch effect of H 2 /O 2 flame. • The LBV increases monotonically with the increase in initial pressure at the experimental pressure range. • The flame instability is induced only by the hydrodynamic mechanism for mixtures in rich-hydrogen conditions. • Only at the lower pressures of 0.1 atm and 0.3 atm does the flame remain stable at all examined equivalence ratios.