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ABSTRACT
Thermal response and chemical reaction of AP/HTPB in flame area of fire are different with that in near flame area of fire. AP/HTPB in flame area of fire is uniformly heated. This process is similar to that in the slow cook-off experiment. Thermal response and chemical reaction in AP/HTPB in near flame area of fire are not uniform, which cannot be characterized by slow cook-off experiment. In this study, a pool fire cook-off model has been established to examine hazard and critical condition of AP/HTPB explosion induced in near flame area of fire. The effects of fire temperatures on the AP/HTPB propellant explosion induced in near flame area of fire are studied using numerical simulation. Critical fire temperature (lowest fire temperature) for inducing explosion of AP/HTPB is 673K at that the initial explosion temperature of 576.4K at which explosion is initiated. At the fire temperature of lower than critical fire temperature, the AP/HTPB explosion cannot be initiated in the near flame area of fire. The ignition delay increases linearly with the decrease of fire temperature. At 673K fire temperature, the ignition delay is 1600s. The initial explosion temperature in the AP/HTPB propellant in the near flame area of fire increases from 736.5K to 790K with the decrease of fire temperature in range from 2000K to 1600K. However, initial explosion temperature of the AP/HTPB decreases from 790K to 576.4K with the decrease of fire temperature in range from 1600K to 673K. The initial explosion temperature in the AP/HTPB propellant in near flame area of fire reaches the maximum value of 790K at 1600K fire temperature.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| q | = | heat (J) |
| qrad | = | radiant heat (J) |
| qconv | = | convective heat (J) |
| A | = | heat transfer area (m2) |
| F | = | view factor |
| εf | = | flame emissivity |
| εs | = | wall emissivity |
| hf | = | convective heat transfer coefficient (W∙m−2∙K−4) |
| Gk | = | turbulent kinetic energy generation term |
| Gb | = | buoyancy turbulent flow energy term |
| YM | = | pulsating expansion contribution |
| = | position vector | |
| = | direction vector | |
| = | scattering vector | |
| s | = | length along the way |
| a | = | absorption coefficient |
| n | = | refractive index |
| σs | = | scattering coefficient |
| = | :boltzmann constant (5.67 × 10−8 W∙m−2∙K−4) | |
| I | = | radiation intensity |
| T | = | local temperature |
| ∅ | = | phase function |
| = | spatial solid angle | |
| A1;2 | = | pre-exponential factor (s−1) |
| E | = | activation energy (kJ∙mol−1) |
| p | = | pressure (Pa) |
| R | = | ideal gas constant |
| Tf | = | flame temperature (K) |
| Ts | = | wall temperature (K) |
| β | = | mass equivalent ratio |
| ρ | = | density (kg∙m−3) |