Flame spread over thin circular PMMA rods

TL;DR

This study investigates flame spread over thin PMMA rods in normal and microgravity, revealing faster spread in microgravity and with thinner rods, influenced by preheating length and curvature effects.

Contribution

It provides new insights into flame behavior on thin cylindrical fuels under different gravity conditions, combining experimental data with detailed analysis.

Findings

Flame spreads faster in microgravity for all tested diameters.

Thinner rods exhibit higher flame spread rates due to curvature effects.

Preheating length is longer in microgravity, facilitating faster flame propagation.

Abstract

In the present article, series of opposed flow, downward flame spread experiments are conducted using 80 mm long cast PMMA cylinders of 1 mm and 0.5 mm diameters at normal and micro gravity environments. All the experiments are conducted at 21 % of oxygen by volume in nitrogen at 1 atmospheric pressure with varying the opposed flow speed from 0 cm/s to 25 cm/s. Flame spread rate, flame shape, preheating, and pyrolysis parameters are observed and analysed by tracking the leading edge of the flame by digital image processing, measuring flame field temperatures, schileren imaging and microscopic observation of burnt solid cones. It is concluded from the study that, flame spreads faster in microgravity for all diameters and opposed flows considered in the study, because of longer preheating length which is confirmed by temperature measurement using 50 microns thermocouples in a flame field. The thinner the fuel faster the flame spread rate because of curvature effect and reduced thermal inertia. In normal gravity, the flame spread rate reduces very slightly with increasing opposed flow while in micro