Abstract
Recent progress in aerosol science has resulted in more challenging demands in the design of new particle beam introduction systems. In this paper, the concept of a variable orifice aerodynamic lens system is presented and supported by the numerical simulation results. This novel particle beam inlet can serve as either a narrow band pass filter (a particle segregator) that only confines particles with a specific size or a broad band pass filter (a particle concentrator) that allows particles with a wide size range to be concentrated on the beam axis. Following a brief description of the inlet system, computational details are described. Simulation of this inlet has been carried out by the commercial computational fluid dynamics protocol FLUENT. Focusing performance and characteristic of single-thin plate orifices have been first revealed and discussed, and then the dynamics and advantages of using multiple lenses with variable orifices are addressed. It is clearly shown that the focusing size range can be primarily adjusted by varying the working pressure, the orifice geometry, and/or the arrangement of orifices. As a result, a selection of the desired particle focusing size range can be achieved without the need of changing the inlet, thus increasing the versatility of the device for a broad range of applications.
Highlights
Rapid detection of ambient aerosols, especially bioaerosols, is inherently difficult due to the low concentration at which species are found
Theoretical studies carried out by Mallina et al [11] have suggested that a single sharp orifice can efficiently transmit particles with a selected narrow size range under specific condition, the working pressure needs to be scanned in order to aerodynamically focus, in a sequential way, particles over a wide size range
Particle motion through a single lens and multiple aerodynamic lenses was simulated by Zhang et al [17], using FLUENT, a commercial computational fluid dynamics (CFD) software package, and the results indicated that the focusing characteristics strongly depend on the inlet geometry and working conditions
Summary
Rapid detection of ambient aerosols, especially bioaerosols, is inherently difficult due to the low concentration at which species are found. Theoretical studies carried out by Mallina et al [11] have suggested that a single sharp orifice can efficiently transmit particles with a selected narrow size range under specific condition, the working pressure needs to be scanned in order to aerodynamically focus, in a sequential way, particles over a wide size range. This type of particle beam inlet is referred to as a “segregator” in this study since it can only produce particle beam within a small size range window. The technical and analytical characterization of this apparatus is described in detail in a companion paper [20]
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