Supplemental materials for: Hot surface ignition of sustainable aviation fuels under well-controlled thermally stratified test conditions

Flammable liquids leaking on hot surfaces are an ignition hazard for fires in aircraft, vehicles, and heavy machinery. Engineering analysis to assess fire risk in these devices, must account for the flammability properties of fuels and other liquids. The autoignition temperature (AIT) is most often used for this purpose. AIT is determined following a standard procedure such as ASTM E659, but it is well-established that the minimum ignition temperature in practical industrial configurations is often significantly higher than the AIT. In this work, we introduce a canonical experimental apparatus that addresses this gap. This proposed apparatus enables the characterization of the probabilistic hot surface ignition behavior of flammable liquids in configurations featuring thermal stratification and reduced residence times compared to ASTM E659. It is highly flexible, enabling testing with various surface materials, droplet diameter, impact velocities, and repetition rate. The introduction of automated optical diagnostic enables rapid testing of multiple fuels. The main focus of the present work is to demonstrate the repeatability of the measurements conducted in this apparatus: In repeated experiments with n-hexane, we find that the standard deviation of the hot surface ignition temperature is 3.8 K. A thorough analysis of the experimental uncertainties is also conducted. We demonstrate the capabilities of the apparatus by examining fuel effects on the ignition behavior of eight fuels: n-hexane, a conventionally-derived Jet-A fuel, and six synthetic aviation turbine fuels and blending compounds (SAFs). We find that the 50 % ignition probability temperature of the most ignitable and least ignitable of our six SAFs differed by 70 K, which motivates future efforts to better account for fuel effects in ignition risk analysis as new SAFs are rapidly entering the aviation fuel market.

This deposit contains the supplementary materials for this article: composition of the fuel samples and experimental data.