AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Development of a Universal Aerosol Conditioning Device for Particle Measurement
Kerry Chen, Charles Robert Koch, JASON S. OLFERT, University of Alberta
Abstract Number: 328 Working Group: Instrumentation and Methods
Abstract Aerosol measurement typically requires some form of conditioning before measurements can be conducted. Typical aerosol conditioning processes include dilution, denuding, and humidification. These processes normally require separate devices; however, a newly developed device, the Universal Aerosol Conditioner (UAC) is able accomplish all of these tasks in one device with an additional application of being able to dilute the gas-phase of the aerosol without diluting the concentration of the particle-phase. This property is useful for applications where a low concentration of particles is present yet gas-phase dilution is required to prevent condensation of condensable material. For example, when measuring particulate from a DPF equipped diesel vehicle it is beneficial to reduce the concentration of the gas-phase to avoid water condensation while maintaining the initial concentration of the particles. The UAC is able to achieve this by exploiting the differences in diffusivity between the particle and gas-phases of the aerosol.
A convective-diffusion equation is used for a physics-based model of the UAC. The theoretical model was validated experimentally by running the UAC in a condition that dilutes the aerosol gas-phase but maintains the particle concentration. Particle penetration and gas-phase dilution performance of the UAC was evaluated using humid ambient particulate as the aerosol and dry air as the dilution gas. Dilution gas to aerosol flow was kept at a ratio of 10:1. At a low aerosol flow rate (0.2 LPM), the particle penetration efficiency was found to be 85% while the penetration efficiency at high flow (1.4 LPM) was 90% which agreed well with theory. Water vapour concentration was measured at the inlet and outlet of the UAC. The dilution factor was found to be ~9 which also agreed well with theory.