Volatility characterization of nanoparticles from single and dual-fuel low temperature combustion in compression ignition engines

ABSTRACT

This work explores the volatility of particles produced from two diesel low temperature combustion (LTC) modes proposed for high-efficiency compression ignition engines. It also explores mechanisms of particulate formation and growth upon dilution in the near-tailpipe environment. The number distribution of exhaust particles from low- and mid-load dual-fuel reactivity controlled compression ignition (RCCI) and single-fuel premixed charge compression ignition (PPCI) modes were experimentally studied over a gradient of dilution temperature. Particle volatility of select particle diameters was investigated using volatility tandem differential mobility analysis (V-TDMA). Evaporation rates for exhaust particles were compared with V-TDMA results for candidate pure n-alkanes to identify species with similar volatility characteristics. The results show that LTC particles are mostly comprised of material with volatility similar to engine oil alkanes. V-TDMA results were used as inputs to an aerosol condensation and evaporation model to support the finding that smaller particles in the distribution are comprised of lower volatility material than large particles under primary dilution conditions. Although our results show that saturation levels are high enough to drive condensation of alkanes onto existing particles under the dilution conditions investigated, they are not high enough to allow homogeneous nucleation of these same compounds in the primary exhaust plume. Therefore, we conclude that observed particles from LTC operation must grow from low concentrations of highly nonvolatile compounds present in the exhaust.

Copyright © 2016 American Association for Aerosol Research

EDITOR:

• Matti Maricq

Acknowledgments

The University of Minnesota authors would like to thank the Oak Ridge National Laboratory Fuels, Engines, and Emissions Research Center for providing a complete test cell, instrumentation, and operating expertise for the RCCI measurements conducted in this study. The authors would also like to thank Prof. David Kittelson at University of Minnesota for his technical guidance in designing and conducting the experimental study. The ORNL authors gratefully acknowledge the support and guidance of Gurpreet Singh, Ken Howden, and Leo Breton in the U.S. Department of Energy Vehicle Technologies Office.

Disclaimer

This article has been authored by UT-Battelle, LLC under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this article, or allow others to do so, for the U.S. Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Funding

Funding the accommodations of G. Lucachick was provided by Oak Ridge National Laboratory Fuels, Engines, and Emissions Research Center. Funding of the University of Minnesota portion of this work was provided by a research gift from General Motors.