AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Counting Efficiency Evaluation of Optical Particle Counters in Micrometer Range by Using Inkjet Aerosol Generator as a Monodisperse Particle Number Standard
Abstract Number: 726 Working Group: Instrumentation and Methods
Abstract This poster presentation introduces a SI-traceable method to evaluate the counting efficiencies of optical particle counters. The method uses inkjet aerosol generator (IAG) as monodisperse particle number standard, and the particle diameter range of SI-traceable calibration is from 0.5 μm to 10 μm. IAG delivers monodisperse particles at precisely controlled rate into an OPC inlet. The method using the IAG defines the size of test particles as volume equivalent diameters because test particles are evaporation residue of an inkjet solution. PSL equivalent optical diameter of the test particles is evaluated by analyzing the pulse height of light scattering signals, and aerodynamic diameter is also measured by using an aerodynamic particle sizer. In order to simulate the sampling of uniformly mixed aerosol the IAG introduces particles at various points across the cone shaped inlet of an OPC. These points are chosen to simulate the spatial distribution of particle flux across the inlet assuming that the velocity distribution of gaseous component is either parabolic or plug. The circular area of the inlet is divided into four segments with equal flow rate under an assumed flow profile; the innermost segment is a circle and the other three are rings. The outlet tube of the IAG travels horizontally through a set of injection points across the inlet to make the number of particles injected to each equal-flow segment is nearly equal. Counting efficiency under an assumed velocity distribution is reproducible, and the reported uncertainty includes the error caused by that the true velocity distribution is somewhere between parabolic or plug. This presentation shares our recent calibration results obtained at 5 μm and 10 μm. The chemical composition of the test particles are lactose monohydrate and sodium chloride. The sampling flowrate and inlet diameter of the tested OPC are 6 L/min and 50 mm, respectively.