Experiments were performed using n-heptane droplets burning in air under microgravity conditions in the 2.2 second drop-tower at NASA-Lewis Research Center. This study demonstrates the effects of pressure on the sooting behavior for droplet flames under microgravity conditions. The transient soot concentration distributions were measured by using a full-field light extinction technique and subsequent tomographic inversion.
The effective control of sooting and the accurate measurement of its magnitude are important for assessing the importance of sooting and radiation on the burning characteristics of droplets. Results indicate that sooting within the droplet flame is sensitive to the ambient pressure. Possible reasons for the reduction of soot concentrations include the reduction in the flame temperature and reduction in residence time for fuel vapor transport within the fuel-rich region.