PDE and Applied Mathematics Seminar
October 27 (Applied Math Lab, 2:30-3:30 pm) Daniel L. Dietrich (NASA Glenn Research Center) will speak on "Low Temperature Burning of Fuel Droplets in Microgravity - Results from the International Space Station".
Recent experiments from the International Space Station (ISS) involving the spherically symmetric combustion of hydrocarbon fuel droplets showed unique and unexpected behavior. The experiments involve igniting an ideally motionless fuel droplet free-floating in a large quiescent ambient environment. Smaller droplets (< 3 mm diameter) burn either to completion (i.e. flame extinction coincident with droplet disappearance) or extinction (i.e., flame extinction at a finite droplet diameter) as expected. Large (< 3 mm diameter) n-alkane fuel droplets burn with a hot flame that extinguishes at a relatively large size due to excessive radiative losses relative to heat release from combustion, again as expected. After radiative extinction, however, the droplets continue to burn without any visible flame. This vigorous burning then ends with an abrupt decrease in the vaporization rate of the fuel droplet coincident with the formation of a large 'cloud' of condensed gases. Theoretical analysis and numerical modeling shows that following radiative extinction of the hot flame the droplet continues to burn with a low temperature flame. These studies show that the cool-flame combustion of droplets is stable only in the Negative-Temperature-Coefficient (NTC) region where the reactivity decreases with increasing temperature.
This presentation will focus on the ISS experiments where cool flame burning has been observed. The topics to be presented include the conditions under which cool flames are observed and diagnostic efforts to image and better understand cool flame burning behavior. Recent observations of the unexpected pressure dependence of cool flame burning will be discussed as well as future experiments and the potential practical applications of the results.
November 24 (Applied Math Lab, 2:30-3:30 pm) Fedor Nazarov (Kent State University) will speak on "Diffusion on Graphs".