A Combined Experimental and Computational Study of Soot Formation in Normal and Microgravity Conditions

In this paper, we consider a combined experimental and computational study of sooting, ethylene-air, laminar, coflow diffusion flames under normal and microgravity conditions. Two different burner configurations (Yale and ACME) are studied. Microgravity experiments are performed aboard the International Space Station. Computed simulations for both configurations under 1 g and 0 g conditions support previous experimental and modeling conclusions that at 0 g, the flame is lengthened, becomes broader and more diffuse, temperatures decrease and soot levels and gas residence times increase. However, in the case of the smaller ACME flame, these effects are significantly diminished. In an effort to assess the cause of the differences between the experimental and computational results at the two gravity levels, we perturbed a variety of model parameters associated with soot evolution to observe their effects on the simulation results. We also investigated the effects of radiation and its re-absorption. The results of the study indicate that it is likely that the model inadequately predicts the thermal field and the use of experimental temperatures imposed onto the solution would provide more accurate simulations of the soot field and heat transfer to the burner lip could alter the boundary conditions of the flames and hence the subsequent solutions.