Theoretical Analysis of the Performance of the TSI Aerodynamic Particle Sizer The Effect of Density on Response

Abstract

The flow field in the TSI aerodynamic particle sizer (APS) has been modeled numerically and particle trajectories have been calculated. The effects of varying physical parameters such as beam location, beam separation, and nozzle separation were studied. Values of these parameters were determined for a particular APS by comparing the calculated particle transit times with measured ones for polystyrene latex and polyvinyl toluene aerosols. This configuration was used to determine the effect of particle density on APS response and to generate correction factors permitting actual aerodynamic diameter to be determined from indicated aerodynamic diameter when particle density is known. Sensitivity studies show that the calculated correction factors will apply to any TSI APS manufactured and operated within the manufacturer's specifications.

Behavior of Compact Nonspherical Particles in the TSI Aerodynamic Particle Sizer Model APS33B: Ultra-Stokesian Drag Forces

“…Spherical particles of higher densities appear as larger particles in the APS33B (higher accumulator channel numbers), because of the smaller drag force experienced by a denser sphere having the same aerodynamic diameter. This density effect has been predicted theoretically John, 1987, 1989;Ananth and Wilson, 1988;Cheng et al, 1990) and confirmed in experimental studies (Baron, 1986;. Methods for correcting this density effect have also been reported John 1987, 1989;Ananth and Wilson, 1988;Cheng et al, 1990).…”

“…However, under ultra-Stokesian conditions, the analyzer response depends on the particle density and shape, as has been identified by Chen et al (1985), Baron (1986), Wang and John (1987), Ananth and Wilson (1988), Brockmann and Rader (1990), and Cheng et al (1992) for the APS33B. Each APS33B unit is calibrated by the manufacturer using spherical PSL particles having a density of 1.05 g/cm3.…”

Calibration of a Counterflow Virtual Impactor at Aerodynamic Diameters from 1 to 15 μm

“…(Despite the name of the APS, the property in question is not quite aerodynamic diameter-a small density correction arises from the fact that both instruments operate outside the Stokes flow regime. A theoretical study of the density effect on APS performance can be found in Ananth and Wilson [1988]). Thus, in principle, a calibration aerosol of arbitrary shape and density can be used without correction to characterize the CVI response to unit density spheres.…”

Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China – interpretations of atmospheric measurements during EAST-AIRE

“…We measured the size-distributed particle number concentration with a TSI Aerodynamic Particle Sizer (APS) every 20 s. The APS separates aerosols according to their aerodynamic (flow) diameters between ∼0.5 and ∼20 µm (Ananth and Wilson, 1988). However, the sizing and detecting efficiencies are relatively poor below ∼0.7 µm, while significant particle loss from the inlet to the detector limits its sampling efficiency for aerosols greater than ∼10 µmin diameter.…”