Characteristics of Particulate Matter from Sustainable Aviation Fuel Combustion in a miniCAST Soot Generator
RAPHAEL MAERKL, Edward Winstead, Bruce Anderson, Matthew Brown, Eva-Lou Edwards, Carolyn Jordan, Francesca Gallo, Susan Mathai, Sayantee Roy, Michael Shook, Elizabeth Wiggins, Luke Ziemba, Richard Moore, NASA Langley Research Center
Abstract Number: 200
Working Group: Combustion
Abstract
Contrails form on aircraft engine particle emissions and contribute substantially to the overall climate impact of aviation. Reduced soot particle number concentrations from zero-aromatic sustainable aviation fuels (SAFs) have been shown to decrease the number of contrail ice crystals and the contrail radiative forcing. Soot particle size distributions as well as soot morphology are expected to play a significant role in the corresponding contrail ice particle number concentrations and resulting radiative forcing. While in-situ case studies comparing SAF combustion to conventional fuel use exist, a systematic parameter study on single fuel parameters and SAF blending ratios is essential in determining corresponding sensitivity of soot characteristics.
The Jing Ltd miniCAST Series D soot generator is used to perform these parameter studies with small amounts of liquid fuel. We change the soot particle properties by varying nitrogen mixing gas and oxidant air flow rates. Test series varying single fuel parameters such as sulfur, aromatic, or naphthalene content allow isolating their impact on soot particle number concentration, size distribution, or morphology. Similarly, the influence of small step variations in SAF blending ratios can be examined.
The measurements are carried out under controlled laboratory conditions with a suite of aerosol microphysical and optical instrumentation connected to the miniCAST exhaust line. The particle exhaust stream can either be probed in its raw state or after passing through a thermodenuder to remove gas-phase components.
These laboratory results are compared to ground-based and in-flight measurements performed during the 2023 EcoDemonstrator campaign. This ensures that miniCAST particles serve as valid cruise emission surrogates and findings are transferable to real-life aircraft engine emission scenarios.
The results of this study will uncover the fuel chemical compositions and combustion parameters which minimize contrail ice particle formation. This way, benefits of the limited resource SAF can be maximized by not only reducing soot particle numbers but also identifying soot size distributions that minimize ice particle activation potential.