MODELING OF HYDROGEN COMBUSTION - TURBULENT FLAME ACCELERATION AND DETONATION

Detailed knowledge about the acceleration of hydrogen-air flames in re al geometries is needed to avoid deflagration-to-detonation transition (DDT). Depending on the initial and boundary conditions, the burning velocity of the same hydrogen-air mixture can vary by an order of magn itude. For the modelling of the acceleration process, a 2-D algorithm based on a direct numerical simulation method and including large-eddy simulation is used to calculate the flame folding in the early phase of the process after ignition. Complex mapping functions to realize di fferent obstacle areas in tubes are presented, the effects of combusti on on the structure of the turbulence in the flow field and the effect s of Bow field instability on the flame development in tubes containin g line or expanded obstacles are discussed. Further flame acceleration can lead to DDT. The initiation of detonation by transverse shock wav es and its inverse process, detonation quenching, are simulated numeri cally, using a FCT-algorithm with possible refinement at the detonatio n front. Reaction kinetics and detonation induction times and lengths are treated rather globally, thus leading to almost tolerable CPU-time . The kinetics are based on an induction parameter model which adapted to a wide range of H-2-air mixtures. The initiation processes of deto nation served in the experiments, the development of the detonation ce ll structure, and quenching based pn geometrical boundary conditions c ould be reproduced numerically. In particular, the cell structure of t he detonation develops automatically from the originally plane front d ue to small local disturbances in the induction times and lengths. Cop yright (C) 1996 International Association for Hydrogen Energy