AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Detailed Characterization of Particulates Emitted by Pre-commercial High-Efficiency Gasoline Engines
ALLA ZELENYUK, Paul Reitz, Dan Imre, Mark Stewart, Paul Loeper, Cory Adams, Mitchell Hageman, Axel Maier, Stephen Sakai, David Foster, David Rothamer, Michael Andrie, Roger Krieger, Kushal Narayanaswamy, Paul Najt, Arun Solomon, Pacific Northwest National Laboratory
Abstract Number: 459 Working Group: Combustion
Abstract Aggressive fuel efficiency mandates drive development of advanced engine technologies, which blur the lines between traditional engine categories. Spark Ignition Direct Injection (SIDI) and Gasoline Direct Injection Compression Ignition (GDICI) are two gasoline engine technologies with potential to achieve very high fuel efficiency by operating more like diesel engines.
We present the results of a study, in which we characterized the size, composition, effective density, and mass of individual exhaust particles, which we use to calculate fractal dimension, average diameter of primary spherules (dp), and number of spherules, void fraction, and dynamic shape factors as function of particle size.
GDICI particulate matter (PM) properties varied markedly with engine load. Under low load conditions, PM is dominated by compact organic particles externally mixed with ~30% fractal soot aggregates comprised of primary spherules with dp=40 nm. Under high load conditions, all particles are fractal with dp=26 nm. Under both conditions fractal agglomerates contain ~55% elemental carbon and have fractal dimensions of 2.11.
Similar characterization of SIDI PM indicates that dp varies dramatically depending on engine operating condition and fuel, which is a marked contrast with diesel. Under some operating conditions, two distinct particle modes were observed: regions of rich air/fuel mixture in the combustion region lead to fractal agglomerates with smaller dp, while the larger primary spherules may be linked to wall/piston impingement. In addition, we find the SIDI PM to contain 40-60% organics tightly bound with the elemental carbon, making it impossible to remove by thermo-denuder.
These results point to significant differences between the properties of PM produced by diesel engines and that generated by SIDI and GDICI engines, requiring adaptation of existing after-treatment technologies used to reduce particulate emissions and their environmental impact.