Computational investigation of airflow, shock wave and nano-particle separation in supersonic and hypersonic impactors

In this paper, the airflow field and particle transport in supersonic/hypersonic impactors were studied and the corresponding collection efficiencies were analyzed. A series of simulations were performed using the coupled Navier-Stokes and energy equations. A new correlation for the distance of Mach disk to impactor plate in supersonic/hypersonic impactors was obtained. A computer model for evaluating the Lagrangian particle trajectories including all the relevant forces was developed. Particular attention was given to accurate analysis of Brownian motions of nano-particles in supersonic and hypersonic flows. The importance of the accurate modeling of the Brownian motion of nano-particles was further emphasized. The simulation results of present model for collection efficiency were found to be in better agreement with the experimental data compared to the earlier models. In particular, the model accurately predicted the loss of the nano-particles in the upstream nozzle due to their Brownian motion. (c) 2007 Elsevier Ltd. All rights reserved.