Design Modification of Virtual Impactor for Enhancing Particle Concentration Performance

Experimental efforts were made to improve the performance of virtual impactors by introducing new design modifications. A flow guide to the minor flow inlet was conceived, designed, and implemented onto the conventional virtual impactor design. Several versions of the flow guides were designed. Subsequently, the effects of the modifications were experimentally evaluated. It was found that if designed properly, a flow guide can improve substantially the particle concentration performance of virtual impactors. The guide angle and distance between the guide and the exit of the aerosol inlet tube ahead of the guide were varied to obtain the optimum design. Subsequently, the performance of one conventional design of virtual impactor and of three different modification designs were compared systematically and the best design among the four was identified. It is expected that this new finding can help improve design of future virtual impactors.