Chemical Properties of Aircraft Engine Particulate Exhaust Emissions

Abstract

The chemical properties of the particulate exhaust emissions from an in-use commercial aircraft engine were characterized in April 2004 as part of the Aircraft Particle Emissions Experiment. The test aircraft was the NASA DC-8 equipped with CFM56-2-C1 engines and the test matrix included 11 different engine throttle levels, three fuel compositions, and three sampling distances. The variations in particle emissions number, size, mass, and chemical composition were measured using a suite of instruments, including an aerosol mass spectrometer. The particle emissions were characterized by a trimodal size distribution. The largest mode was dominated by ambient accumulation mode particles mixed into the plume. The middle mode consisted of carbon soot with sulfate and organic coatings. The smallest mode was completely volatile and consisted of sulfate and organic components. The soot emission indices increased with power from 2-120 mg=kg fuel. The semivolatile components increased with distance and decreased with power from 33-5 mg=kg fuel. The sulfate emissions increased with distance and fuel sulfur content. The emissions under low power were dominated by organics, and the high-power conditions were dominated by soot. The CFM56 engine was less efficient at the low thrust levels typically used on the ground at an airport.

Sampling Artifacts from Conductive Silicone Tubing

“…Substantial PDMS pick up is evident on the 30-100 nm vacuum aerodynamic diameter soot particles (roughly 10% by mass), and the PDMS is present as an internally mixed aerosol together with soot particles (Timko et al 2008;Onasch et al 2009). The silicone tubing data in Figure 4b show that organic aerosol particles present in the air in our laboratory and used to dilute the primary exhaust sample (i.e., the size mode greater than about 500 nm) picked up about 1-3 wt % of the PDMS contaminant.…”

“…We previously observed siloxane compounds during several campaigns to characterize aircraft engine exhaust particles (APEX-1, Lobo et al 2007;Onasch et al 2009; JETS-APEX2/APEX3, ). With repeated FIG.…”

Composition and Sources of the Organic Particle Emissions from Aircraft Engines

“…Onasch et al (2009), Timko et al (2010b, 2011, 2013, and Yu et al (2010) have described the use of the AMS specifically to characterize aircraft exhaust PM. Briefly, the AMS converts aerosols into a particle beam that is focused onto a tungsten vaporizer (typically held at 600…”

“…Motivated by these environmental concerns, researchers have performed studies to advance the current state of knowledge of gas turbine engine NO X Wormhoudt et al 2007;Wood et al 2008;Timko et al 2010a; Lee et al 2011;Santoni et al 2011), volatile organic compounds (Spicer et al 1994;Herndon et al 2006Herndon et al , 2009Knighton et al 2007;Yelvington et al 2007;Timko et al 2010c;Beyersdorf et al 2012), and PM emissions (Herndon et al 2005bLobo et al 2007Lobo et al , 2011Hagen et al 2009;Onasch et al 2009;Bulzan et al 2010;Timko et al 2010b). Partly because the knowledge base was limited and partly due to the potential impacts, particular emphasis has been placed on characterizing turbine engine PM emissions.…”

“…Onasch et al (2009) reported that the aircraft volatile PM is a complex mixture of sulfate and organic compounds. Timko et al (2010b) reported that-under idle conditions-organic material could constitute more than 90% of the mass of the nucleation/growth mode material.…”