Venkat Narayanan Mechanical Engineering PhD Comp Exam Presentation
- Friday, November 6, 2020 at 10:10am
- WebEx Meeting number (access code): 120 839 0754 Meeting password: q5mFXTStS35
NUMERICAL METHODS IN APPLICATIONS OF ELECTROHYDRODYNAMIC SPRAYS
A number of tasks are performed in an automobile manufacturing facility, one of which is painting. Paint shops can take up to 70% of the total energy costs and account for up to 80% of the environmental concerns in the facility. A device that is extensively used for painting vehicles is called a Rotary Bell Atomizer (RBA). In addition to atomizing paint by rotating at high speeds (10k-100k RPM), RBAs electrically charge the liquid and operate in a background electric field. Atomized charged droplets are directed towards the target surface by the electric field. The atomization process heavily influences transfer efficiency (TE) and surface finish quality. Optimal spray parameters used in industry are often obtained from expensive trial-and-error methods. In this work, a computational approach is used to simulate three-dimensional RBA near-bell atomization using a high-fidelity volume-of-fluid transport scheme and several physics modules including ones that model centrifugal, Coriolis and electrohydrodynamic (EHD) forces. Using the tools developed, numerical simulations are performed to understand the physics of electrically assisted atomization. In addition to development, testing and validation of these physics modules, a mesh independence study is conducted to test for convergence over six mesh resolutions and to identify the coarsest mesh that provides sufficiently detailed results. A parameter study is performed over three parameters (nozzle rotation rate, nozzle flow rate and liquid viscosity) to explore their effects on jet behavior. The primary goal of this research is to investigate the influence of EHD parameters on near-bell atomization of paint and subsequently improve TE in RBAs in a cost-effective manner.
Another electrospray phenomenon observed in laboratories is also explored. Experimental studies show the formation and propagation of whipping instabilities in a grounded electroyte jet flowing through an electric field. A numerical formulation of this system involves including a model for ion transport using the Nernst-Planck equation into the EHD module developed for modeling RBAs. A secondary goal of this research is to investigate the origin and dynamics of this jet behavior and further the understanding of the underlying physical processes in electrosprays.
- Department of Mechanical & Industrial Engineering