Turbulent Quenching and Acceleration of Flames by Highly Blocking Obstacles

In the case of a hypothetical severe accident, a significant amount of hydrogen can be released. Mixed with the ambient air, the resulting explosive mixture can significantly endanger the containment integrity. Due to the complex physical processes at combustion phenomena and due to the large geometry of a reactor containment, the propagating of the flame and the resulting pressure load cannot be simulated with sufficient accuracy by now. One aim of the presented projects, which were performed within the fourth frame-work of the European Community, was to improve combustion models implemented into system codes, which are the state of the art for the simulation of severe accidents at real scale geometries with long transients. Within this paper, selected results in the field of turbulent flame propagation are pointed out. A correlation for both, turbulent flame acceleration and flame quenching at very high turbulence intensities, for lean hydrogen-air mixtures will be given. Due to the high accuracy of the performed optical measurements of both, the turbulent flow-field directly in front of the flame, as well as the development and the structure of the flame itself, the results of the experiments are currently also used to improve CFD models to simulate turbulent combustion phenomena. 1