Advanced Combustion via Microgravity Experiments-Structure and Response of Spherical Diffusion Flames

A series of experiments is proposed with the following specific objectives, in both soot-free and sooty flames, to compare with detailed computational simulation to assess transport properties and detailed chemical kinetics (including chemiluminescence): Objective A. Measure and characterize the transient structure (such as temperature and species distribution) of diffusion flames established at initially non-steady, spherical flame structures for mixtures of different H2/CH4/diluent ratios (soot-free) and different C2H4/diluent ratios (sooty), for different flow rates. Objective B. Determine the quasi-steady convective/chemical-kinetic extinction limits (low system Damköhler numbers) and radiative/chemical-kinetic extinction limits (high system Damköhler numbers) for mixtures of different H2/CH4/diluent ratios (soot-free) and different C2H4/diluent ratios (sooty). Objective C. Determine the existence (for different Zeldovich number, Ze), onset (as a function Da), and nature (i.e. mode, frequency, amplitude) of pulsating instabilities theoretically predicted to occur in transient spherical diffusion flames using fuel/diluent mixtures that are above a critical Lewis number.