Characterization of Lubrication Oil Emissions from Aircraft Engines

Abstract

In this first ever study, particulate matter (PM) emitted from the lubrication system overboard breather vent for two different models of aircraft engines has been systematically characterized. Lubrication oil was confirmed as the predominant component of the emitted particulate matter based upon the characteristic mass spectrum of the pure oil. Total particulate mass and size distributions of the emitted oil are also investigated by several high-sensitivity aerosol characterization instruments. The emission index (EI) of lubrication oil at engine idle is in the range of 2-12 mg kg(-1) and increases with engine power. The chemical composition of the oil droplets is essentially independent of engine thrust, suggesting that engine oil does not undergo thermally driven chemical transformations during the ∼4 h test window. Volumetric mean diameter is around 250-350 nm for all engine power conditions with a slight power dependence.

Composition and Sources of the Organic Particle Emissions from Aircraft Engines

“…In this study, the lubrication oil signatures of engines which are known to use Air BP lubrication oils (RB211-535E4-B) are dominated (10:1) by lube oil #1 factor, whereas engines which use Mobil II (CFM56, PW4158) are closer to a 1:1 mixture of lube oil #1 and lube oil #2 factors. The PMF results appear to support the contention by Yu et al (2010) that the two major lubricating oil types can be differentiated by using aerosol mass spectrometry.…”

“…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…”

“…One component of the organic PM exhaust we clearly identify as lubrication oil, a known component of aircraft engine PM emissions (Timko et al 2010b;Yu et al 2010Yu et al , 2012. Yu et al (2010) studied lubrication oil PM under well defined laboratory conditions and concluded that the mass spectra of pure synthetic lubrication oils could be differentiated from fuel-related hydrocarbons by strong signals at m/z 85 and 113 combined with weak signals for common ions derived from saturated and unsaturated hydrocarbons (i.e., delta series of 0 and +2 for unsaturated and saturated hydrocarbons, respectively; McLafferty and Tureček 1993).…”

“…Yu et al (2010) studied lubrication oil PM under well defined laboratory conditions and concluded that the mass spectra of pure synthetic lubrication oils could be differentiated from fuel-related hydrocarbons by strong signals at m/z 85 and 113 combined with weak signals for common ions derived from saturated and unsaturated hydrocarbons (i.e., delta series of 0 and +2 for unsaturated and saturated hydrocarbons, respectively; McLafferty and Tureček 1993). Timko et al (2010b) and Yu et al (2010) attributed the strong m/z 85 and 113 signals to synthetic esters (specifically the C 6 H 9 O and C 8 H 13 O fragments) that account for >90% of aircraft synthetic lubrication oil composition. The lubricating oil organic PM component is described by the sum of the two factors of the 6-factor PMF solution factors in this study; this result is robust, being obtained for six-factor PMF analyses on the total data set as well as for individual PMF analysis of the AAFEX and APEX-3 studies.…”

“…Accordingly, aerosol mass spectra for the two lubrication oils may be distinct from one another; however, the aerosol mass spectra have also been shown to be sensitive to the analytical conditions (specifically vaporizer temperature; Yu et al 2010). In this study, the lubrication oil signatures of engines which are known to use Air BP lubrication oils (RB211-535E4-B) are dominated (10:1) by lube oil #1 factor, whereas engines which use Mobil II (CFM56, PW4158) are closer to a 1:1 mixture of lube oil #1 and lube oil #2 factors.…”