Effects of geometrical parameters on eccentric cylindrical differential mobility analyzer

The Differential Mobility Analyzer (DMA) is a core instrument for classifying aerosol nanoparticles. Alsharifi and Chen (Aerosol Science and Technology, 2019) established a critical framework for analyzing axially eccentric DMAs and quantified the pronounced influence of geometric parameters on the transfer function under a defined set of design conditions. Building upon their essential findings, this work extends the investigation by systematically examining the effect of geometrical parameters across a comprehensive range of eccentricity levels. Through coupled numerical simulations of flow field, electric field, and particle dynamics, we demonstrate that increased eccentricity consistently degrades classification performance by reducing the transfer function peak and broadening its full width at half maximum (FWHM). More critically, the sensitivity of these metrics to specific geometric variations is highly parameter-dependent. A key finding is that at an eccentricity of just 2%, the transfer function undergoes a transition from a single to a double peak, which severely impairs classification efficiency. This study thus quantifies the performance boundaries of DMA design and provides actionable guidance for achieving the high-precision coaxial alignment essential for accurate particle sizing.