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NASA NTRS2020

Particle Size Measurements from the 2018 Honeywell Uncertified Research Engine Test in the NASA Propulsion Systems Laboratory

The particle size measurements from the Honeywell Uncertified Research Engine Icing Test in the NASA Propulsion Systems Laboratory conducted in 2018 are presented. This work focuses on describing the experimental arrangement, the processing and analysis methods, and final results for select cases acquired during ice crystal cloud conditions. The measurements presented will include data acquired by two High Speed Imaging instruments located both upstream and downstream of the fan, in the engine bypass section. Experimental results demonstrate the expected downward shift in the particle size distribution as the cloud passes through the engine fan and the ice particles break-up. This work also demonstrates the feasibility of acquiring particle size distributions in the environment of a running engine.

Engine icing↗

NASA NTRSDate not supplied

Effect of Aromaticity on Soot Formation: A Reactive Molecular Dynamics Study

This study investigates the formation of soot from n-dodecane and its blend with m-xylene under pyrolytic and low-oxygen conditions with reactive molecular dynamics (MD) simulations. ReaxFF force field is used to simulate the interactions of fuel and oxygen molecules at engine-relevant conditions (2500-3500 K and 70-75 bar). Fuel molecules with carbon atom density of 0.03 g/cm 3 are dispersed into a cube and constant temperature simulations are carried out with a Nosé-Hoover thermostat. Pyrolysis of n-dodecane and the chemical pathway towards the formation of aromatic hydrocarbons are investigated. The initial pyrolysis rate of n-dodecane is observed to be slightly higher with the addition of aromatic compounds and oxygen. While the first aromatics formed from the decomposed n-dodecane are phenyl radicals at 2500 K, decomposition of the aliphatic fuel compound is observed to be necessary to build a carbon cluster, and eventually soot. Morphological properties of the created soot particles are also analyzed. The maturity, size and aromatics content of the soot particle are slightly affected with the addition of m-xylene and oxygen at 3500 K within the 3 ns simulation time possibly due the formation of larger and more condensed aromatic rings, resulting in larger soot molecules. The outcomes of this study provide important insights into the formation mechanism of soot and its morphological characteristics depending on varying fuel concentrations at pyrolysis and low oxygen engine conditions. Results of this analysis will further contribute to the understanding of contrail formation on generated soot particles originated from the combustion of different chemical components with particle chemistry matching companion experiments.

soot formation↗