| Abstract: | A computer code PROVER-I for propagation phase of vapor explosion is developed to couple with MPS simulation. From the simulation results by MPS method, a new thermal fragmentation model is proposed with three types of time scale for modeling instant fragmentation, spontaneous nucleation fragmentation and normal boiling fragmentation. The structure of vapor explosion is investigated based on different fragmentation models. The vapor explosion with spontaneous nucleation fragmentation is characterized as a non-equilibrium overdriven detonation, and vapor explosion with hydrodynamic fragmentation is characterized as a non-equilibrium spontaneous burning. Sensitivity analyses are carried out for some parameters such as fragmentation time scale, delay time and vapor volume fraction. Spontaneous nucleation fragmentation with shorter delay time results in a vapor explosion structure situated between a non-equilibrium overdriven detonation and a non-equilibrium spontaneous burning, while a longer delay time gives a composite structure of vapor explosion which includes a shock and a non-equilibrium deflagration. The energy conversion ratio of a non-equilibrium overdriven detonation is much larger than that of a non-equilibrium spontaneous burning. The composite structure has the same destructive potential as non-equilibrium overdriven detonation. The variation of energy conversion ratio with the vapor volume fraction is consistent with the observations in fuel-coolant interaction experiments. |
