Alternative Fuels Tests on a C-17 Aircraft: Emissions Characteristics

Abstract

Abstract : Emissions evaluations were conducted on a C-17 Globemaster III F117-PW-100 engine operated with alternative fuels blends. These tests support the USAF goal of 50% domestic fuel consumption using alternative (synthetic) fuels with lower or equal carbon footprint than petroleum fuels by 2016. The tests took place at Edwards Air Force Base on the period of August 16 through 27, 2010 as part of the United States Air Force (USAF) Alternative Fuels Certification Office (AFCO) ground and flight tests to certify the C-17 on a 50/50 by volume JP-8/hydroprocessed renewable jet (HRJ) fuel blend. Emissions were collected from engine 3 of the parked aircraft operated on conventional JP-8 and 50/50 blends of JP-8 and a beef tallow-derived HRJ, and a 50/25/25 blend of JP-8, HRJ and a coal-derived Fischer-Tropsch (FT) fuel. Gaseous and particulate matter (PM) emissions were measured. PM measurements included particle number (concentration), mass and size distribution. In addition, hazardous air pollutant (HAPs) emissions, smoke numbers and chemical analysis of soot samples were performed for the engine operated with the three fuels. Emissions were collected for five engine operating conditions ranging from 4% (idle) to ~63% of rated maximum thrust. Test results show that the alternative fuel blends resulted in no operational anomalies or detrimental impacts on the gaseous or PM emissions of the F117 engine for any of the conditions tested. Moderate reductions in carbon monoxide (CO) emissions (~30%) and more significant reductions in sulfur oxides (50%), measured HAPs (>60%) and PM emissions (30-60%) relative to operation with JP-8 were observed. The alternative fuels had negligible impact on nitrogen oxides (NOx) emissions.