Experimental and numerical analysis of impacts, mass transfer, and deposition in dispersed phase systems

Abstract

Multiphase flows are fluid systems comprising at least two distinct phases that are transported jointly as a mixture. These systems pose challenges in engineering analysis and design due to the many permutations that arise from various mixture compositions and inter-phase interactions, often requiring case-specific analysis. The studies in this dissertation focus on experimental and numerical techniques to characterize dispersed phase systems, wherein the secondary phase(s) are dilute yet are able to greatly affect system behavior. Specific examples of such systems include (i) dusty high-speed flows where micrometer-sized atmospheric particles may lead to vehicle damage or failure, (ii) dissolved-ion transport in liquids near sensing membranes where coupled fluid flow and electrostatics can affect sensor performance, and (iii) nanometer to micrometer particle transport within electrostatic indoor air cleaners where device efficacy is directly related to particle size and composition. Motivated by these three examples, this thesis will be split into three main topics providing detail on (1) characterization of surface damage and erosion from high-speed particle impacts, (2) analysis of forced convection on ion-selective membranes using numerical solutions to the Navier-Stokes Nernst-Plank-Poisson system of equations, and (3) mass transfer analysis of particle collection with electrostatic precipitators using numerical methods developed from (2) alongside particle trajectory calculations. Through the study of these three topics, it was found that: (1) The extent of material damage from resulting high-speed particle impacts, as characterized by displaced material volume, can be collapsed into a single relationship for a wide range of impacting speeds and angles for ferrous sulfate projectiles onto Aluminum 6061-T6. (2) Phase boundary potentials in ion-selective membrane systems are influenced by external flow and can be described by unique dimensionless flow parameters such as the Debye length Reynolds number. (3) Newly developed approaches to describing particle mass transfer in electrostatic precipitators provide improvements in describing particle mass transfer rates in complex systems involving a combination of deterministic and stochastic particle motion.