Flow Field Effects on Nucleation in a Reacting Mixture Layer.
Aero propulsion rept.,
AERONAUTICAL RESEARCH LABS MELBOURNE (AUSTRALIA)
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Chemical nucleation has been studied numerically in a stagnation point mixing layer in which reactants in two counter-flowing streams form a condensable monomer. The response of the subsequent nucleation kinetics to the velocity gradient in the flow is described in terms of a Damkohler number. Two limiting cases have been established. Firstly, if the Damkohler number for monomer production is small, i.e. the rate of monomer production is slow, then the nucleation of particles can be strongly affected by the flow field in a manner which is equivalent to the effect of supersaturation in a uniform vapour. Secondly, if the Damkohler numbers for cluster growth are smalldue to a small accommodation factor for monomer-cluster interactions, the concentrations of clusters do not achieve equilibrium levels. This can result in the suppression of particle formation over a critical range of Damkohler numbers. In this case the behavior of the nucleation kinetics is analogous to the transient phase of nucleation in a uniform vapour.
- Physical Chemistry