Materials Compatibility

Many currently approved SAFs are limited to a maximum blend ratio of 50% with conventional jet fuel due to materials compatibility issues (i.e., O-ring volume swell). Previous work, which is cited below, proposed that cycloalkanes can be used in SAFs to (1) overcome the blend limit of SAFs, (2) minimize particulate matter emissions and radiative forcing, and (3) add to the value proposition of SAFs. The previous work showed that optimized blends consisting primarily of cycloalkanes can potentially swell in the conventional range while providing fuel performance gains.

Current efforts are focused on optical dilatometer measurements of volume swell for SAFs at an early stage of the approval process. These measurements are being incorporated into two fuel prescreening tiers: Tier α and Tier β. Optical dilatometry measurements are coupled with two-dimensional gas chromatography (GCxGC) data to predict volume swell with <1 mL of fuel for Tier α.

1. Kosir S, Heyne J, Graham J, "A machine learning framework for drop-in volume swell characteristics of sustainable aviation fuel", Fuel, 2020, https://doi.org/10.1016/j.fuel.2020.117832.