Microgravity Superagglomerates Produced by Silane and Acetylene

Published

February 19, 2017

Author(s)

Matthew Bundy, George Mulholland, Samuel Manzello, Jiann C. Yang, J H. Scott

Abstract

A study of acetylene and silane diffusion flames was performed in normal gravity (1-g) and microgravity ([mu]-g) to determine the evolution of soot and silica agglomerates. The objective of this study was to understand the process of gas phase agglomeration leading to superagglomerates and a gel-like structure for 1-g silane and [mu]-g acetylene flames. Silane flames were observed in normal gravity using the drop rig hardware. Long fibrous particles were produced that consisted of partially fused spherule structures as well as cage-like structures at high silane flow.. Microgravity acetylene soot plume development was observed at fuel flow rates of 0.6 cm³/s, 1.0 cm³/s, and 2.0 cm³/s. Primary particle size distributions were measured using TEM analysis on soot particle agglomerates sampled using a thermophoretic probe in the post-flame region of the plume. Soot superagglomerates were observed in microgravity as large as 1 mm using direct imaging of the soot plume. For the first time, visible particles are imaged both in the luminous flame zone and the plume. A computer simulation was used to predict the profiles for particle volume fraction, temperature, species, and velocity. The simulations showed good qualitative agreement with the visible flame and plume structure from the 1-g and [mu]-g acetylene experiments. The flame simulation results were used as input conditions for a model to predict the agglomerate growth and gelation. The agglomeration simulations predict that the formation of large soot agglomerates (> 100 [mu]m) are possible at [mu]-g conditions but not at 1-g based on free molecular agglomeration including gelation.

Citation

AIAA Aerospace Science Meeting and Exhibit

Pub Type

Journals

Keywords

acetylene, agglomerates, gelation, microgravity, silane, soot

Citation

Bundy, M. , Mulholland, G. , Manzello, S. , Yang, J. and Scott, J. (2017), Microgravity Superagglomerates Produced by Silane and Acetylene, AIAA Aerospace Science Meeting and Exhibit (Accessed February 5, 2025)