PRESSURE-COUPLED RESPONSES OF LOX DROPLET VAPORIZATION AND COMBUSTION IN HIGH-PRESSURE HYDROGEN ENVIRONMENTS

The dynamic responses of liquid oxygen (LOX) droplet vaporization and combustion to externally imposed pressure oscillations in high-pressure hydrogen and water environments are studied systematically. Both subcritical and supercritical conditions are considered, under a broad range of pressures at 10-200 atm. A unified treatment of general fluid thermodynamics and a self-consistent numerical method are developed to treat the droplet behaviors over the entire fluid thermodynamic regime. Results are correlated with the instantaneous value of the liquid-phase thermal diffusion time normalized by the oscillation frequency, fR(2)/alpha(l). The magnitudes of the vaporization and combustion response functions increase with increasing ambient pressure. The magnitude of the combustion response function is much smaller than its corresponding gasification response due to the damping effect associated with vapor accumulation near the droplet surface. Significant difference exists between hydrogen/oxygen and hydrocarbon/air systems in terms of the cut-off and resonant values in the characteristic frequency spectrum.