Characterization of Particulate Matter Morphology and Volatility for Two Direct-Injection Engines

  • Author / Creator
    Graves, Brian M
  • Particulate matter emitted from two direct injection engines has been characterized by morphology, volatility, mass-mobility exponent, effective density, and size distribution using tandem measurements from a centrifugal particle mass analyzer (CPMA) and differential mobility analyzers (DMA). The engines consisted of a heavy duty, natural gas, compression ignition engine fitted with a high pressure direct injection (HPDI) system, and a four cylinder gasoline direct injection (GDI) engine fueled with gasoline and ethanol blends. The HPDI engine was tested at six conditions which varied load, speed, EGR fraction, and fuel delivery strategy. The GDI was tested at three engine loads at 2250 RPM (4%, 13%, and 26% of maximum load) in addition to an idle condition, while it was fueled using gasoline mixed with ethanol fractions of 0% (E0), 10% (E10), and 50% (E50) by volume. An increase in engine load increased particle number concentration for both engines, but the GDI idle condition produced approximately as many particles as at 13% load. An increase in ethanol fraction in the GDI decreased number concentration, but E10 produced more particles than E0 at idle and 26% load. HPDI size distributions were log-normal whereas GDI size distributions were not log-normal and were instead skewed. The fraction of the number of purely volatile particles to total number of particles (number volatile fraction, fN) for the HPDI engine decreased as load increased, although the low-speed, partially premixed mode had the lowest fN. The fN for the GDI both overall and as a function of particle mobility-equivalent diameter was under 10 percent at all engine conditions and fuels. The size-segregated ratio of the mass of internally mixed volatile material to total particle mass (fm) was similarly low for the GDI. The fm for the HPDI was higher; however it decreased with an increase in load and with particle mobility-equivalent diameter. HPDI effective density was seen to collapse to approximately a single line, but engine modes with higher fm values had slightly higher effective densities suggesting that the soot structures have collapsed into more dense shapes. Effective density and mass-mobility exponent for the GDI engine increased with load. Effective density decreased with an increase in ethanol fraction and a slight decrease in mass-mobility exponent was also observed for all conditions except idle. Effective density trends from both engines were compared to data from other GDI engines, a port fuel injection engine, and diesels, and the data is relatively similar between all engine types, with 90% of data points being within ±27% of a common trend line.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.