Lean-Burn Aircraft Engine Emissions from Burning Sustainable Aviation Fuels: Results from the 2021 and 2022 Boeing ecoDemonstrator Ground Tests

Richard Moore, Steven Baughcum, Matthew Brown, BENJAMIN A. NAULT, Bruce Anderson, Josh DiGangi, Edward Fortner, Andrew Freedman, Francisco Guzman, Jennifer Klettlinger, Richard Miake-Lye, Kevin Sanchez, Michael Shook, Gregory Smallwood, Elizabeth Wiggins, Edward Winstead, Luke Ziemba, NASA

     Abstract Number: 122
     Working Group: Combustion

Abstract
Advancements in technology and fuel sources have led to reductions in the non-volatile and volatile particle emissions from aircraft gas turbine engines. To understand these changes, particle and trace gas emissions were sampled on the ground at 30-60 m behind on-wing engines with lean burn combustors over two years of testing. The 2021 test sampled behind a 737-9 aircraft located at Boeing Field (Seattle, WA, USA), while the 2022 test sampled behind a 787-10 aircraft and a 777-200ER aircraft located at Boeing’s Everett Delivery Center (Everett, WA, USA). Four different fuels were investigated, including 100% sustainable aviation fuel (SAF), petroleum-based Jet A fuel, petroleum-based Jet A low sulfur fuel, and a SAF blend.

Volatile and non-volatile particles and trace gases were measured for each fuel and engine combination. Trace gases included CO2, CO, NOx. Total and non-volatile particle number concentration were measured with a pair of condensation particle counters (CPCs), while total and non-volatile particle number size distributions were obtained from a pair of Scanning Mobility Particle Sizers (SMPS). For the non-volatile particle measurements, the CPC and SMPS were operated behind a custom-built thermal denuder heated to 350°C. Non-volatile mass was estimated from particle light absorption techniques from different instruments, and non-volatile and volatile mass in the accumulation mode with a Soot Particle Aerosol Mass Spectrometer. A detailed list of instruments is given on the project websites [1,2].

Overall, the results are consistent with expectations based on the ICAO Emissions Databank for non-volatile particles. Stark reductions in non-volatile particle number and mass were observed for higher thrust conditions when the engine staged. The lowest non-volatile particle emissions were observed for the 100% SAF. Low sulfur fuels were observed to reduce sulfate particle emissions; although, the measured sulfate mass concentrations were always above the ambient background. This paper provides a quantitative assessment of engine emissions indices for lean burn engines burning SAF relative to conventional Jet A.

References:
[1] Boeing ecoDemonstrator Science and Engineering Team (2022). 2021 Boeing ecoDemonstrator Emissions Ground Test Dataset, https://doi.org/10.57700/1f7s-tn05.
[2] Boeing ecoDemonstrator Science and Engineering Team (2023). 2022 Boeing ecoDemonstrator Emissions Ground Test Dataset, https://doi.org/10.57700/7ktk-3y74.

This work was supported by the Boeing ecoDemonstrator Program, the NASA Advanced Air Transport Technology (AATT) Project within the Advance Air Vehicles Program (AAVP), and FAA ASCENT Program.