Surface Temperature Measurements in the Mevinq Wire Technique

Abstract

Abstract – The surface temperature of a substrate at ignition is a sensitive measure of its ignitability and one which holds the promise of providing direct information about the fundamental chemistry and physics of ignition. We present measurements of the surface temperature of the substrate in the moving wire technique (MWT) for studying polymer combustion. In the MWT. the substrate is moved at a controlled speed through a stationary ignition source, with the result that combustion is held stationary in laboratory coordinates. The measurement of surface temperature is a vital part of the MWT and substantially clarifies the ignition process. The measurements were achieved by two methods. The first employs a null point method in which a thermocouple is in rubbing contact with the substrate; the thermocouple is surrounded by an oven whose temperature is adjusted to the null point. The second method makes use of thermal paints in the nonburning regimes. Our results for teflon indicate that the surface temperature at ignition in an O2-rich source flame is independent of the shape, temperature, flow speed and O2-level of the source flame. It is also independent of the size and probably the geometry of the substrate. Hence, ignition temperature appears to be invariant, and information of direct applicability to real practical systems can thus be gathered in the scientifically simpler moving wire system.