Report on the relationship between molecular structure and compression ignition fuels, both conventional and HCCI

NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Executive Summary The U.S. Department of Energy (DOE) is committed to increasing our nation's energy security by decreasing our dependence on imported petroleum. The Fuels Technologies Subprogram within DOE's Office of Freedom Car and Vehicle Technology (OFCVT) supports research that allows the United States to develop advanced fuels that enable efficient engines with low emissions. This document reports the completion of NREL FY 2004 Annual Operating Plan milestone 10.2: " Report on the relationship between molecular structure and compression ignition fuels, both conventional and HCCI. " This work is an incremental step toward the OFCVT Multi-Year Program Plan APBF/NPBF Milestone No. 3: " Establish fuel and lubricant constituents that are required for advanced combustion regime engines. " We must understand the effects of fuel chemistry on ignition to develop fuels that enable more efficient engine designs, using both today's technology and future advanced combustion concepts. NREL has conducted two parallel activities aimed at understanding how molecular structure affects ignition properties. First, we developed an empirical tool to predict the cetane number (CN) of pure compounds with only the molecular structure as input. Then, we experimentally investigated the ignition properties of pure chemicals with varying functional groups. In the first activity, we conducted a comprehensive search of CN data in the published literature to understand how molecular structure affects compression ignition. This resulted in CN data for 275 pure compounds, including 147 hydrocarbons and 128 oxygenates. These compounds were then input into a Quantitative Structure Activity Relationship (QSAR) software package. Then we calculated a set of approximately 100 molecular descriptors from the molecular structure of each compound. These descriptors …