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Comparison of Partial and Total Dilution Systems for the Measurement of Polycyclic Aromatic Hydrocarbons and Hydrocarbon Speciation in Diesel Exhaust
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
There are two methods of sampling exhaust emissions: total dilution using a constant volume sampling (CVS) system and partial flow dilution by proportionally diluting a small part from the main exhaust stream. The CVS dilutes the entire exhaust flow to a constant volumetric flowrate which allows for proportional sampling of the exhaust species during transient engine operation. For partial dilution sampling during transient engine operation, obtaining a proportional sample is more rigorous and the proportionality of the sample must be continuously changed throughout the cycle in order to be proportional to the overall continuously-changing exhaust flow. For this study, a Sierra Instruments BG-3 Partial Flow Sampling Cart (BG-3) and a standard CVS were used to compare the measurements for polycyclic aromatic hydrocarbons (PAH) and hydrocarbon speciation of compounds from methane to dodecane including aldehydes and ketones in diesel exhaust. Engine-out emissions from a 2016 12.4L Navistar without aftertreatment were sampled with both dilution systems, and samples for PAH and hydrocarbon speciation were collected and analyzed. A comparison of these two different dilution systems demonstrated that the BG-3 produced similar results for both the regulated and the unregulated emissions when compared to the CVS.