http://idea.library.drexel.edu/handle/1860/831 Search the Channel search http://idea.library.drexel.edu/simple-search http://idea.library.drexel.edu/handle/1860/1878 Title: Cool flames at terrestrial, partial, and near-zero gravity <br/> <br/>Authors: Foster, Michael Robert; Pearlman, Howard <br/> <br/>Abstract: Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra < 600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; and reduced gravity, ∼10^−2g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350°C (593–623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive– diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results. Thu, 28 Sep 2006 22:58:59 GMT http://idea.library.drexel.edu/handle/1860/1111 Title: Earth, Partial, and Reduced Gravity Experiments and Numerical Work on Propane-Oxygen Cool Flames at Sub-atmospheric Pressures <br/> <br/>Authors: Foster, Michael Robert <br/> <br/>Abstract: Natural convection plays an important role in nearly all terrestrial (1g), unstirred, static reactor cool flame and low-temperature auto-ignition studies. At near-zero gravity, however, Rayleigh numbers (Ra) less than the critical Ra for onset of buoyant convection can be achieved and the effects of convection can be suppressed. In this case, transport occurs strictly through diffusive fluxes of heat and species. To systematically vary the relative importance of natural convection versus diffusive transport without varying the mixture stoichiometry, reactor pressure, or vessel size, low-temperature reactions and cool flames are studied experimentally in a closed, unstirred, static reactor at 1g and aboard NASA’s KC-135A subject to different gravitational accelerations (Martian—0.38g, Lunar—0.16g, and reduced-gravity—10−2g). Representative results will be presented on the visible light emission, the temperature histories, and the pressure histories at temperatures ranging from 593–623 K (320–350◦C) in sub-atmospheric propane:oxygen premixtures. The results are compared qualitatively to numerical predictions derived from solutions to the coupled species, energy, and incompressible Navier-Stokes equations using a Gray-Yang skeletal kinetic mechanism. <br/> <br/>Description: Master's Thesis Tue, 26 Sep 2006 20:23:33 GMT