Igniter Effects on Metals Combustion Testing

Abstract

The combustion of 0.32-cm-diameter pure iron rods in gaseous oxygen under normal and reduced gravity conditions has been investigated to determine whether the upward Regression Rate of the Melting Interface (RRMI) and other burning characteristics are affected by the type of igniter material (wire) used. The experiments performed involved igniting the samples in normal gravity with different types of igniter wire at the two separate test pressures of 0.69 and 6.9 MPa (100 and 1000 psia). The igniter wires used were pure aluminum wire, pure iron wire and aluminum-palladium (Pyrofuze®) wire. The results have shown that in normal gravity the RRMI is unaffected by the type of igniter wire used when measured after the first two drops of molten oxide products have detached from the burning sample. However, the ignition event and subsequent first stages of burning of the iron rods were significantly different for the different igniter wires. Post-test microanalysis of test samples showed that in normal gravity, no igniter material was present with the formed oxide products on the end of the test sample rod. However, post-test microanalysis of test samples burned in reduced gravity showed a film of palladium, introduced by the Pyrofuze® igniter wire, coating the interface between the melted and resolidified portion of the rod and the formed oxide products. The physical orientation and location of the palladium film and the fact that palladium acts as a catalyst in many oxidation reactions suggests that reduced gravity burning could be influenced by the choice of igniter wire and further experimentation is warranted. Additionally, the palladium present during the ignition event in normal gravity tests may act as a catalyst to further promote the ignition of the sample and influence the initial stages of burning.