Design of Wide Particle Size Range Aerodynamic Inlet System with New Pre-focus Structure

Abstract. A new aerodynamic lens injection system has been designed for wide particle size range, which adds virtual impact and pre-focus structure on the basis of traditional PM2.5 lenses. The system has a small volume and successfully improves the focusing ability of traditional PM2.5 lens systems to 100 nm–10 μm. The structure of the new pre-focus hole solves the problem of affecting the transmission and focusing of large particles, effectively reducing the beam width and dispersion angle of particles entering the virtual impactor, significantly improving the focusing effect of large particles, and enhancing the transmission efficiency of large particles. It can also effectively focus particles without significantly accelerating particles, avoiding the structural size of the buffer chamber being too large. Numerical simulation shows that the new injection system can transmit particles with 100 % efficiency in the range of 0.2–4 μm particles, and can achieve the transmission of 1–9 μm particles with an efficiency higher than 90 %. The standard microsphere experiment verified the good consistency between the performance of the injection system and the simulation results. In the testing of standard Arizona dust, the wide-range particle size distribution obtained by the new injection system is highly consistent with APS 3321. The new injection system combines a new pre-focus structure, a smaller buffer chamber, a five-stage lens, and the whole injection system volume that is up to 90 % smaller than previous self-made wide-range lens designs. At the same time, it has ultra-high transmission efficiency, demonstrating the potential for miniaturization of single particle aerosol mass spectrometer in detecting particles with a wide particle size range.