Ignition and Combustion Characteristics of Overloaded Wire Insulations Under Weakly Buoyancy or Microgravity Environments

The electric wire, cable and components are the potential igniters, which might cause fire under certain unexpected circumstances. This chapter focuses on the pre-ignition characteristics by overload, the soot emission from the wire insulation during the pre-ignition and ignition stages, the smoke release and distribution characteristics of wire insulation combustion. We reviewed the research work on wire insulations completed by the authors. We first presented the functional simulation methods. The concept of "function simulation" means that the simulation is satisfied in heat transfer sense. A low pressure narrow channel method (LPNCM) was proposed to study fire initiation of wire insulation at microgravity. Then we introduced the experiments completed in microgravity by using the China recoverable satellites of SJ-8 and SJ-10. The experimental hardware were developed to perform the experiments ofwire insulation experiments caused by overload on board the SJ-8 and SJ-10 China recoverable satellites, respectively. In the experiments, the pre-fire characteristics including the temperature and radiation characteristics of the wire insulations were presented. For the SJ-10 experiments, the smoke emissions of overloaded wires insulations were investigated. Two smoke emitting modes, namely the end smoke jet and the bubbling smoke jet were identified with polyethylene insulation. The results show that the morphology of pyrolysis front dominated the direction and the range of the end smoke jet. The effects of the insulation thickness and the excess current on the temperature rise were discussed.