Using a new inversion matrix for a fast-sizing spectrometer and a photo-acoustic instrument to determine suspended particulate mass over a transient cycle for light-duty vehicles

Xue, Jian; Li, Yang; Quiros, David; Wang, Xiaoliang; Durbin, Thomas D.; Johnson, Kent C.; Karavalakis, Georgios; Hu, Shaohua; Huai, Tao; Ayala, Alberto; Jung, Heejung S.

doi:10.6084/m9.figshare.3850659.v1

UAST_1239247_Supplemental File.docx (360.93 kB)

Using a new inversion matrix for a fast-sizing spectrometer and a photo-acoustic instrument to determine suspended particulate mass over a transient cycle for light-duty vehicles

journal contribution

posted on 2016-09-22, 20:18 authored by Jian Xue, Yang Li, David Quiros, Xiaoliang Wang, Thomas D. Durbin, Kent C. Johnson, Georgios Karavalakis, Shaohua Hu, Tao Huai, Alberto Ayala, Heejung S. Jung

Integrated particle size distribution (IPSD) is a promising alternative method for estimating particulate matter (PM) emissions at low levels. However, a recent light-duty vehicle (LDV) emissions study showed that particle mass estimated using IPSD (M_IPSD) with the TSI Engine Exhaust Particle Sizer (EEPS) Default Matrix was 56–75% lower than mass derived using the reference gravimetric method (M_Grav) over the Federal Test Procedure (FTP). In this study, M_IPSD calculated with a new inversion matrix, the Soot Matrix, is compared with M_Grav and also photoacoustic soot mass (M_Soot), to evaluate potential improvement of the IPSD method for estimating PM mass emissions from LDVs. In addition, an aerodynamic particle sizer (APS) was used to estimate mass emission rates attributed to larger particles (0.54–2.5 µm in aerodynamic diameter) that are not measured by the EEPS. Based on testing of 10 light-duty vehicles over the FTP cycle, the Soot Matrix significantly improved agreement between M_IPSD and M_Grav by increasing slopes of M_IPSD/M_Grav from 0.45–0.57 to 0.76–1.01 for gasoline direct injected (GDI) vehicles; however, for port-fuel injection (PFI) gasoline vehicles, a significant discrepancy still existed between M_IPSD and M_Grav, with M_IPSD accounting for 34 ± 37% of M_Grav. For all vehicles, strong correlations between M_IPSD and M_Soot were obtained, indicating the IPSD method is capable of capturing mass of soot particles. The discrepancy between the M_IPSD and M_Grav for PFI vehicles, which have relatively low PM emissions (0.22 to 1.83 mg/mile), could be partially due to limited size range of the EEPS by not capturing larger particles (0.54–2.5 µm) that accounts for ∼0.08 mg/mile of PM emission, uncertainties of particle effective density, and/or gas-phase adsorption onto filters that is not detected by in situ aerosol instrumentation.