PROPAGATION OF CELLULAR HETEROGENEOUS DETONATION UNDER THE CONDITION OF VARIABLE GEOMETRY
Two-dimensional flows of heterogeneous cellular detonations in channels with sudden expansion are numerically investigated on the model of detonation of suspensions of aluminum particles in oxygen. Influence of phase interaction processes on properties of the detonation wave diffraction behind a backward step and on following propagation in a wide part of the channel is investigated. The common properties with corresponding processes in gases are established: existence of three propagation regimes behind a step, re-initiation in the transverse waves, reconstructions of cellular structures, similar critical conditions of propagation in terms of geometrical parameters of the channel at diffraction of planar and cellular detonations. Characteristic features of scenarios of heterogeneous detonation development, caused by more complex flow structure and velocity and temperature interactions of the phases are revealed. Dependence of the flow patterns and diffraction regimes on dispersion (the size of particles) is established, the regime map is presented in the plane: particle size - exit channel width. Threefold decrease of critical number of cells in the channel in comparison with the gaseous detonations, caused by constitutive influence of processes of thermal and velocity relaxation on the ignition process, is shown and physically proved. The critical ratio of the transverse sizes of the channel for detonation propagation in the 3.5- micron mixture corresponds to data for gaseous detonations. However, this criterion cannot be universal applying to two-phase mixtures.