| A computational study (emphasizing the effects of oxygen enhancement, gravity and inverse burning on species mass-fraction, velocity, temperature, radiative losses, transport properties, reaction rates, species emission and flame size) has been performed for ethane fueled laminar gas jet diffusion flames. Fire safety, efficient energy utilization and fundamental research, both on earth and in space, are the areas where this study is of great value. However, unfortunately because of genuine modeling and resource limitations, a systematic study of its kind has previously not been completed. With this vision, 22 axisymmetric flames with varying oxidizer compositions (21, 30, 50, 100% O2 moles in N2) were studied using steady-state global and detailed (34 species--388 reactions and 99 species--1071 reactions) chemistry mechanisms. Results for 16 flames were compared with flame images obtained at NASA Glenn Research Center. The oxygen enhancement resulted in increased flame temperatures and presence of gravity led to increased gas velocities. For inverse diffusion flames, oxygen enhancement caused an increase in CO and soot emission, whereas opposite trend was observed for normal diffusion flames. For normal diffusion flames, their flame-lengths decreased and flames-widths increased (2-3 times) when going from earth-gravity to microgravity, and flame-length decreased by five times when going from air to pure oxygen environment. For inverse diffusion flames, radiation emission increased with oxygen enhancement and gravity reduction. Soot and CO 2 were the major contributors to radiation emission. Evaluation of diffusion flame theory where estimates of reaction rates can be made using composition data revealed that this theory can be applied to inverse diffusion flames with greater confidence. Gravity-reduction and oxygen enhancement cause deviations from this theory. Findings from this study will help make critical design decisions for various energy related applications, will help evaluate fire associated risks and will assist in developing better analytical flame models. |
