A Condensation Feedback Mechanism for Oscillatory Nucleation and Growth

Abstract

The competition between nucleation and condensation on new particle surfaces is shown to provide an effective control mechanism capable of regulating the dynamics, size, and number density of particles formed through gas-to-particle conversion. Calculations are presented for a continuous stirred tank aerosol reactor (CSTR) under conditions approximating coal-gas aerosol and atmospheric particle formation. A linearized normal mode analysis is used to obtain a complete stability diagram for the system, and both stable and unstable regimes of operation are found. An expression for the period of marginal oscillation at the boundary between these regimes is obtained. Computer simulations for the evolution of particle number and particle surface area densities are presented for representative operating conditions in the stable, marginally stable, and unstable condition regimes. In the unstable regime, sustained limit-cycle oscillations in particle size and number density are found. Each of these effects is traced to nonlinearity inherent in the classical description of evaporation and growth.