AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Uncertainty in Thermal-Optical Analysis for Elemental Carbon from Aircraft Engine Exhaust
GREGORY SMALLWOOD, Stephanie Gagne, Brett Smith, Joel Corbin, Benjamin Brem, Andrea Fischer, Lukas Durdina, Prem Lobo, National Research Council Canada
Abstract Number: 681 Working Group: Combustion
Abstract The real-time instruments used for regulatory measurements of aircraft engine non-volatile Particulate Matter (nvPM) mass emissions have to be calibrated to the mass of elemental carbon (EC) determined by thermal-optical analysis (TOA) of the filter-sampled emissions of a diffusion flame source. This EC is defined by an analysis method originally based on the National Institute of Occupational Safety and Health (NIOSH) Method 5040 for diesel PM. This method involves evaporating volatile organic carbon in an inert helium environment and non-volatile carbon in a helium-oxygen environment, while monitoring the filter transmittance to evaluate a pyrolysis correction to determine a so-called split point between organics and EC. However, significant differences have been observed in the EC content determined by different laboratories. These differences are observed as bias between different laboratory analyzers, differences in split-point assignment, and greater scatter on some laboratory instruments compared to others. To investigate the differences observed in the TOA results and determine the associated uncertainties, we performed a set of round-robin experiments following the standard procedures for determining EC mass concentration as described in SAE ARP6320. A total of 20 filter samples were acquired from the exhaust of a Rolls-Royce Gnome engine. Six punches from each filter were distributed amongst the five laboratories (one laboratory performed duplicate analyses), each following the standard TOA protocol defined in SAE ARP6320. Preliminary results indicate that the variability between different laboratories for EC was ± 11.4% with a standard deviation of ±2.6%. A separate two-way comparison was also performed on filter samples collected for nvPM emissions from a CFM56-7B engine. These results will be used to assess the reproducibility of this method.