Sooting Behavior in Concurrent and Upward Burning of Cylindrical PMMA-samples

Date

2023-07-16

Journal Title

Journal ISSN

Volume Title

Publisher

2023 International Conference on Environmental Systems

Abstract

IR videography has proven useful for tracking the position of the pyrolysis front under a flame propagating upward in 1g. Since PMMA burns with low soot formation in 1g conditions, the radiation density of the gases above the sample is very low and the flame is hardly visible. As a result, the surface can be easily followed and the temperature at the pyrolysis front can be determined. The phenomenological definition of the pyrolysis front remains difficult. In experiments on concurrent propagation along cylindrical PMMA samples under µg conditions during the Sounding Rocket flight TEXUS 57, it was shown that the drastically increased soot production compared to terrestrial conditions leads to a significantly increased radiation fraction by the gas phase above the sample. Here, pyrolysis front temperatures were determined to exceed 450 °C and include a significant radiative fraction of soot formed between the flame and the sample. This also sheds light on the significantly elevated local temperatures under µg conditions, which can lead to self-sustaining burning of some materials in microgravity that are inflammable or extinguishing on ground– this despite the overall reduced mass burn rate observed in microgravity. The paper compares pyrolysis front velocities in upward configuration (1g) along cylindrical PMMA samples with diameters of 5, 20, and 25 mm with concurrent propagation (µg) of the same samples. Both the 1g and µg experiments were performed in hypoxic exploration atmosphere (70 kPa, 26.5% O2). While the 1g experiments were subjected to buoyant convection only with a typical but averaged flow velocity of 20 to 30 cm/s, a forced inflow between 20 and 30 cm/s was set for the µg experiments. Soot formation was also analyzed in the microgravity tests.

Description

Christian Eigenbrod, University of Bremen, Center of Applied Space Technology an Microgravity(ZARM), Germany
Florian Meyer, University of Bremen, Center of Applied Space Technology an Microgravity(ZARM), Germany
Hans-Christoph Ries, University of Bremen, Center of Applied Space Technology an Microgravity(ZARM), Germany
Jan Heissmeier, University of Bremen, Center of Applied Space Technology an Microgravity(ZARM), Germany
ICES509: Fire Safety in Spacecraft and Enclosed Habitats
The 52nd International Conference on Environmental Systems was held in Calgary, Canada, on 16 July 2023 through 20 July 2023.

Keywords

concurrent flame spread, upward burning, radiation effects, PMMA cylinder

Citation