Study of forward smolder ignition of polyurethane foam: Fid-Bau Portal

Study of forward smolder ignition of polyurethane foam

Anthenien, R.A. / Fernandez-Pello, A.C.

Experiments have been conducted to study ignition of forward smolder of a high void fraction, flexible, polyurethane foam in a forced airflow. Tests are conducted in a small-scale, vertically oriented, cylindrical test section with supporting instrumentation. A Nichrome wire heater placed between two porous ceramic disks, one of which is in contact with the foam surface, is used to supply the necessary power to ignite and sustain a smolder reaction. A constant power is applied to the heater for a given time, and the resulting smolder is monitored. Reaction zone temperature and smolder propagation velocity are obtained from the temperature histories of thermocouples embedded at predetermined positions in the foam with junctions placed along the fuel centerline. Air is forced through the heater and foam and controlled via mass flow controllers. Forced flow air velocities of 0 to 10 mm/s during smolder ignition and 1 to 10 mm/s during smolder propagation were used. The results show a well-defined smolder ignition regime primarily determined by two parameters, igniter power flux, and the time the igniter is powered. They also show that a requirement for ignition is that the fuel-igniter interface must attain a minimum temperature. An energy balance model has been developed that describes the observed ignition results. The model is based on the assumption that for ignition to occur the heater must provide a heat flux equivalent to a propagating smolder front at a given distance from the igniter.