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Journal of Combustion
Volume 2014, Article ID 686347, 15 pages
http://dx.doi.org/10.1155/2014/686347
Research Article

Numerical Simulation of the Deflagration-to-Detonation Transition in Inhomogeneous Mixtures

Lehrstuhl für Thermodynamik, Technische Universität München, 85748 Garching, Germany

Received 16 February 2014; Accepted 4 April 2014; Published 19 May 2014

Academic Editor: Yiguang Ju

Copyright © 2014 Florian Ettner et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this study the hazardous potential of flammable hydrogen-air mixtures with vertical concentration gradients is investigated numerically. The computational model is based on the formulation of a reaction progress variable and accounts for both deflagrative flame propagation and autoignition. The model is able to simulate the deflagration-to-detonation transition (DDT) without resolving all microscopic details of the flow. It works on relatively coarse grids and shows good agreement with experiments. It is found that a mixture with a vertical concentration gradient can have a much higher tendency to undergo DDT than a homogeneous mixture of the same hydrogen content. In addition, the pressure loads occurring can be much higher. However, the opposite effect can also be observed, with the decisive factor being the geometric boundary conditions. The model gives insight into different modes of DDT. Detonations occurring soon after ignition do not necessarily cause the highest pressure loads. In mixtures with concentration gradient, the highest loads can occur in regions of very low hydrogen content. These new findings should be considered in future safety studies.