NUMERICAL PREDICTION OF OBLIQUE DETONATION-WAVE STRUCTURES USING DETAILED AND REDUCED REACTION-MECHANISMS

Modelling of the structure and the limiting Bow turning angles of an o blique detonation wave, established by a two-dimensional wedge, requir es the implementation of detailed chemical kinetic models involving a large number of chemical species. In this paper, a method of reducing the computational effort involved in simulating such high-speed reacti ng Bows by implementing a systematically reduced reaction mechanism is presented. For a hydrogen-air mixture, starting with an elementary me chanism having eight species in 12 reactions, three alternate four-ste p reduced reaction mechanisms are developed by introducing the steady- state approximation for the reaction intermediates HO2, O and OH, resp ectively. Additional reduction of the computational effort is achieved by introducing simplifications to the thermochemical data evaluations . The influence of the numerical grid used in predicting the induction process behind the shock is also investigated. Comparisons of the ind uction zone predicted by two-dimensional oblique detonation wave calcu lations with that of a static reactor model (with initial conditions o f the gas mixture specified by those behind the nonreactive oblique sh ock wave) are also presented. The reasonably good agreement between th e three four-step reduced mechanism predictions and the starting mecha nism predictions indicates that further reduction to a two-step mechan ism is feasible for the physical flow time scales (corresponding to in flow Mach numbers of 8-10) considered here, and needs to be pursued in the future.