Optimization Studies on a Slit Virtual Impactor

Abstract

This study reports the results of numerical investigations performed on a proposed slit virtual impactor configuration. Simulations were performed using the computational fluid dynamics program CFX-4.4. A detailed numerical investigation was carried out to determine the critical geometrical parameters of the proposed configuration that would optimize the performance for the anticipated operation conditions (specified Reynolds number and major-to-minor flow split ratio). A detailed sensitivity analysis was performed on the optimized configuration to determine its performance characteristics (impactor efficiency and wall loss curves) for (a) operation at different major-to-minor flow split ratios for a constant Reynolds number and (b) operation at different Reynolds numbers but at the same major-to-minor flow split ratio. Finally, the effect of modifying the radius of curvature of the receiving section of the optimized configuration on the impactor performance was studied for the anticipated operation conditions, and the results are reported.

Keywords:

• CFD
• virtual impactors
• Eulerian-Lagrangian modeling
• modeling disperse two-phase flow
• CFX-4.4

Acknowledgments

Funding provided for this work by the U.S. Army, Soldier Biological Chemical Command (SBBCOM), Edgewood Chemical Biological Center (ECBC), under supervision of Dr. Edward Stuebing and Dr. Jerry Bottiger, is gratefully acknowledged.

The help of Hong Xu, technical support (contact) at ANSYS-CFX (formerly AEA Technologies), Pittsburgh, is greatly acknowledged. Discussions with Dr. John Haglund, Aerosol Technology Laboratory, Department of Mechanical Engineering, TAMU, during this study are greatly acknowledged.

Notes

^a HDS: hybrid differencing scheme, CDS: central differencing scheme

^b URF: under relaxation factors

^c ICCG: preconditioned conjugate gradient solver, GEN AMG: general version of the algebraic multigrid solver