Abstract View
Turbulence Impacts upon nvPM Sizes
MADHU SINGH, Akshay Gharpure, Randy Vander Wal, Prem Lobo, Joel Corbin, Gregory Smallwood, Penn State University
Abstract Number: 4
Working Group: Combustion
Abstract
In a multi-partner collaboration led by NASA and DLR, the field campaign ND-MAX/ECLIF2 was conducted between January 14 and February 3, 2018 from Ramstein Air Base in southwest Germany. Ground-based particle and gas measurements were performed on the DLR A320 “Advanced Technology Research Aircraft (ATRA)” with IAE V2527 engines as the emissions source. A series of reference and blended fuels were studied in order to vary aromatic concentration, H-content, sulfur content and naphthalene content. Results presented here are results from TEM analysis of non-volatile particulate matter (nvPM). Collected directly upon TEM film grids, aggregate, primary particle and nanostructure scales were analyzed for selected conditions.
A striking observation is the range of primary particle size. Projected particle diameter range is 5 – 100 nm. Notably this range of primary particle sizes is that repeatedly found within a single aggregate. This range of particle size is interpreted as describing the corresponding ensemble of fuel rich pockets in the combustion zone in terms of phi and residence time. Some parcels are sufficiently diluted or short-lived by turbulent action to allow only small primary particles to form. Subsequently aggregation of varied particles from different fuel-rich regions then occurs (also due to turbulence) – effectively remixing these fuel-rich pockets. In this manner the soot particles provide forensic insights into the turbulent mixing dynamics. As a consequence and unlike laboratory soot sources, there is no single streamline or trajectory describing particle growth and no single condition in equivalence ratio or temperature for particle nucleation. Given the different trajectories of small/large particles and growth histories and species origins, a difference in H-content would be expected. This is reflected in the relative contributions of sp2/sp3 content within the particles as confirmed by EELs analysis.