主 办：爆炸科学与技术国家重点实验室

          安全与防护协同创新中心

报告题目：NEAR-LIMIT HYDROGEN FLAME PROPAGATION IN A THIN LAYER GEOMETRY

报告人：Prof. M. Kuznetsov

            Karlsruhe Institute of Technology. Germany

时间：2019年7月26日下午14:30

地点：北京理工大学3号教学楼146会议室

报告摘要：

A series of experiments on hydrogen flame propagation in a thin layer geometry is presented. Premixed hydrogen-air compositions in the range from 4.5 to 15%H2 (equivalence ratio from 0.11 to 0.42) are tested. Semi-open vertical combustion chamber consists of two transparent Plexiglas side walls with main dimensions of 90x20 cm with a gap from 1 to 10 mm in between. Test mixtures are ignited at the open end of the chamber so that the flame propagates towards the closed end. Ignition position changes from top to bottom in order to investigate an effect of gravity on flame propagation regimes. High-speed shadow imaging is used to visualize the combustion process. Thermal-diffusion, Darrieus-Landau and Saffman-Taylor instabilities are governing the general flame behavior. Heat losses to side walls and viscous friction in a thin layer may fully suppress the flame propagation with local or global extinction. The sensitivity to heat losses can be characterized using a Peclet number as a ratio of layer thickness to laminar flame thickness. Approaching to critical Peclet number Pec = 42 the planar or wrinkled flame surface degradates to one- or two-heads “finger” flame propagating straight (for two-heads flame) or chaotic (for one-head flame). Such a “fingering” of the flame is found for the first time for gaseous systems and very similar to that reported for smoldering or filtering combustion of solid materials and also under micro-gravity conditions. The distance between “fingers” may depend on deficit of limiting component. The processes investigated can be very important from academic and practical points of view with respect to safety of hydrogen fuel cells.