Improving aerosol flow alignment and particle classification efficiency using rod-type sheath flow laminarizer in a differential mobility analyzer

The improvement in particle classification performance of a differential mobility analyzer (DMA), based on an original cost-effective design, was investigated using a simple sheath flow laminarizing structure. The DMA was designed as a parallel-type, and was used with high aerosol/sheath flow ratios to achieve a wide particle diameter range. The sheath flow of the laminarizing structure consisted of a vertical rod located at the center of the flow channel. A computational fluid dynamics (CFD) optimization was performed for enhancing aerosol flow alignment. With the flow laminarizer, the aerosol flow alignment toward the channel upper wall significantly improved. Subsequently, experiments were performed to examine the effects of the sheath flow laminarization and aerosol flow alignment on the particle classification performance of the DMA. As a result, the classification efficiency increased by 91.1, with a 200 nm particle sample and aerosol/sheath flow ratio of 1:5.