Comprehensive Eulerian models for electrostatic phenomena in polydisperse gas-particle flows

Iowa State University, Ames IA

Investigators

Abstract

Solid particles in motion in a gas form a gas-particle flow, often encountered in the food, pharmaceutical, and chemical industries. In this flow type, particles repeatedly collide with other particles or walls and become electrically charged. Such charged particles can accumulate in parts of the systems used to produce and process them, degrading performance or preventing correct operations. They can also cause sparks, leading to explosions, such as those that happen when emptying corn silos, with serious safety implications for workers and infrastructure. This award will develop computer models to better predict when electric charge accumulates on solid particles and how it affects the behavior of gas-particle flows. These predictions will allow hazardous conditions or situations adverse to the process under consideration to be mitigated at the design stage, potentially reducing design costs, and improving system performance and safety. Graduate and undergraduate students will be trained as part of the award, contributing to education and workforce development. In addition to disseminating the results through scientific publications and conferences, a short course targeting the relevant industry sectors will be organized to facilitate knowledge transfer. A comprehensive Eulerian multiphase model for electrostatic charging in granular and gas-particle flows will be formulated. Kinetic theory closures for the hydrodynamic properties and electrostatic charging will be derived, accounting for finite contact time, consistently with the constitutive contact charge model. The experimentally observed normal distribution of charge saturation, currently assumed constant in most computational models, and the dependency of charge saturation on the local temperature and pressure value will be incorporated into the model. Wall boundary conditions accounting for the effect of electric force will be proposed to enable the correct description of charged particles at solid surfaces. Multiphase RANS closures will be formulated to account for the effect of turbulence on particle charging, enabling the application of the newly formulated model to regimes with higher gas flow rates and turbulent behavior, such as those encountered in fluidized bed risers and pneumatic conveying. Validation against experiments and direct numerical simulations from the literature will be performed to establish and demonstrate the predictive capabilities of the newly developed model. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.