A Method To Employ the Aerodynamic Particle Sizer Factory Calibration Under Different Operating Conditions

Abstract

The dimensionless aerodynamic particle sizer (APS) response function (normalized particle velocity against particle Stokes number) first reported by Chen et al. (1985) is explored for much larger solid particles (diameters to 35 pm) over a similar range of instrument pressures (624-740 mm Hg) and flow rates (4.2-6.0 L/min). An essentially unique response function is found for low and intermediate Stokes numbers under a variety of operating conditions, including the use of argon as the carrier gas. For large particles, however, non-Stokesian drag effects introduce systematic differences among calibration sets so that a unique response function no longer applies. The largest differences are observed between calibrations performed in air and argon, although even in this case the sizing error amounts to < 12% for a 20-pm polystyrene latex sphere. For intermediate Stokes numbers, a direct consequence of this work is that a reference calibration (channel number against Stokes number) can be used under different ambient conditions by setting the APS to operate at the same nozzle velocity as used in the reference calibration. With the single-velocity method, the factory-supplied calibration relating channel number to aerodynamic diameter can be used for air over a reasonable range of ambient temperatures and pressures. The same calibration can be used with an argon carrier gas provided that the aerodynamic diameters reported by the APS software are adjusted by the square root of the gas viscosity ratio. For the singlevelocity mode of operation, a generalization of a correction proposed by John (1987, 1989) can be made and is shown to reduce by one half the sizing error introduced by non-Stokesian drag.

Uncertainty Budget of the SMPS–APS System in the Measurement of PM1, PM2.5, and PM10

“…The aerosol flow rate uncertainty, u m−APS,i (θ ), was evaluated as ±10% on the basis of Rader et al (1990) and TSI Inc. APS specifications (2004). The APS counting statistical uncertainty, u m−AP S,i c i , was estimated through the Poisson distribution as reported in the SMPS uncertainty analysis.…”

Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

“…Although the APS gives a repeatable, high-resolution response for particle diameters < 30 pm, it does require a calibration, particularly for deformable droplets (Brockmann et al, 1988). Rader et al (1990) described a new technique for operating the APS which allows the use of factory calibration curves in nonstandard operating conditions, and confers greater sizing accuracy than was previously possible. This method was adopted for the present set of experiments.…”

Bioaerosol collection and concentration for microseparations-based detectors.

“…The APS provides particle concentration (number of particles per cm3 of air) versus aerodynamic diameter over the range of 0.5 to 30 pm at a sample flow rate of 5.4 liters per minute (LPM). As the particle response curve (velocity vs. size) cannot be predicted apriori, a calibration is required (e.g., Rader et al 1990). In this study, commercially prepared monodisperse polystyrene latex (PSL) calibration particles (Duke Scientific, Palo Alto, CA) were used to verify the APS calibration curve.…”

“…microparticles, the surface tension force is by far the dominant force, exceeding all other forces, in most cases, by several orders of magnitude for particles 5 1 pm diameter [Ref. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Only the inertial forces of a high velocity impingement can come close to equaling or exceeding the surface tension force.…”

“…A general purpose finite element fluid mechanics code [Ref. [3][4][5][6][7][8][9][10][11] was used to calculate the free surface deformation and fluid forces.…”