The Effect of Fuel Composition on Performance and Emissions of a Variety of Natural Gas Engines

Abstract

<div class="section abstract"><div class="htmlview paragraph">Work was performed to determine the feasibility of operating heavy-duty natural gas engines over a wide range of fuel compositions by evaluating engine performance and emission levels. Heavy-duty compressed natural gas engines from various engine manufacturers, spanning a range of model years and technologies, were evaluated using a diversity of fuel blends. Performance and regulated emission levels from these engines were evaluated using natural gas fuel blends with varying methane number (MN) and Wobbe Index in a dynamometer test cell. Eight natural gas blends were tested with each engine, and ranged from MN 75 to MN 100. Test engines included a 2007 model year Cummins ISL G, a 2006 model year Cummins C Gas Plus, a 2005 model year John Deere 6081H, a 1998 model year Cummins C Gas, and a 1999 model year Detroit Diesel Series 50G TK. All engines used lean-burn technology, except for the ISL G, which was a stoichiometric engine.</div><div class="htmlview paragraph">Performance testing consisted of monitoring engine knock or auto-ignition, as well as engine power levels and overall engine operability. Emissions of total hydrocarbons (HC), non-methane hydrocarbons (NMHC), carbon monoxide (CO), oxides of nitrogen (NO<sub>X</sub>), nitrogen dioxide (NO₂), particulate matter (PM), and carbon dioxide (CO₂) were measured using procedures developed by the United States Environmental Protection Agency (EPA) for heavy-duty, on-highway engines. The engines showed no sign of autoignition throughout the program, with slight differences in power levels with the various test fuels. All lean burn engines showed increased NO<sub>X</sub> and HC emission levels with decreased MN and increased Wobbe level, while the stoichiometric ISL G showed no clear trend in NO<sub>X</sub> or HC levels with the various fuels.</div></div>