A transient one-dimensional model for metal combustion in steam

Alternate Titles

• NPS-72-86-001CR.

Description

The possibility of ignition of some particles of a fragmented Under- Water (U/W) Shaped-Charge (S/C) jet is examined. It was determined that only minute particles (less than 6 micron diameter) are likely to undergo complete melting. This estimate was based on the high stagnation temperature upstream of a particle moving at a speed of 7000 m/sec in water vapor within the cavity. Some two-color pyrometry tests of exploding wire that had been conducted at the Naval Postgraduate School were re-examined. It is suggested that color photographs of the corona region exhibit on going gas phase combustion. Due to the high temperature (inferred from the color), it is contended droplets do not occur in that region (either metal or oxide). The mode of combustion is distinctly different from metal droplet combustion such as may take place in U/W S/C or in rocket combustion/Existing models for metal droplet combustion were found to lack two features, namely full time-dependence and oxide cloud radiation for a large volatile droplet. We suggest to incorporate these features in the proposed model. For simplicity, only the one dimensional (spherically symmetry) case is considered. Metal liquid to vapor interface is not treated explicitly but through including th vapor quality and vaporization latent heat into the total metal enthalpy. The condensed oxide (according to local equilibrium composition), is considered as a second phase. Thus the model ought to be adequate for either volatile or non-volatile process of metal combustion. Keywords: Metal combustion, Exploding wire, Transient droplet combustion.

Subjects