Measuring PM Emissions from Aircraft Auxiliary Power Units, Tires, and Brakes (2013)

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29 AAFEX: Alternative Aviation Fuel Experiment; an aircraft emissions measurement campaign using alternative aviation fuels conducted January 20 to February 3, 2009, at NASA Dryden Aircraft Operation Facility advected plume: wind-transported exhaust plume, subjected to local meteorological conditions aerodynamic diameter: the diameter of an equivalent unit density sphere with the same settling velocity in still air as the particle in question aircraft gas turbine engine: any gas turbine engine used for aircraft propulsion or for power generation on an aircraft, including those commonly called turbojet, turbofan, turbo- prop, or turboshaft type engines1 AMS: aerosol mass spectrometer APEX: a series of aircraft engine emissions field measure- ment campaigns including APEX1, Delta Atlanta-Hartsfield Study, JETS-APEX2, and APEX3 APU: auxiliary power unit, a small gas turbine engine that provides (bleed air) aircraft power for pneumatic systems, ventilation, and heating BC: black carbon CAPS: cavity attenuation phase shift CH4: methane C2H2: acetylene C2H4: ethylene C2H6: ethane C4H10: butane C24H14: dibenzopyrene CO: carbon monoxide CO2: carbon dioxide Cu: copper elemental carbon: the refractory carbon found in combustion- generated particulate matter. Also known as graphitic carbon1 EGT: exhaust gas temperature EI: emissions index, the emissions of a given constituent per unit of fuel burned (EIm—emission index (mass) in g/kg fuel; EIn—emission index (number) in number of particles/kg fuel) engine exit plane: any point within the area of the engine exhaust nozzle at an axial distance within 0.5 diameters (or equivalent, if not circular) downstream from the outer edge of the nozzle Fe: iron GMD: geometric mean diameter GSD: geometric standard deviation HAPs: hazardous air pollutants, 188 pollutants that the Clean Air Act Amendments of 1990 required the EPA to regulate. The complete list of pollutants can be found on the EPA web- site: http://www.epa.gov/ttn/atw/orig189.html (for a com- plete list, see Appendix C—The Clean Air Act Amendments of 1990 List of Hazardous Air Pollutants). H2: hydrogen HCHO: formaldehyde HCOOH: formic acid HC: hydrocarbon line loss: percent of particles lost during transit through a given sample line. Particle loss mechanisms include impaction, Glossary of Terms, Acronyms, and Abbreviations 1 Society of Automotive Engineers Aerospace Information Report 5892 copy- right © 2007 SAE.

30 diffusion, settling (gravitational), and thermophoresis (thermodiffusion). MAAP: multi-angle absorption photometer mass-based emission index: the mass of emissions of a given constituent per thousand mass units of fuel burned (e.g., g/kg fuel). Also total mass of particulate emissions in the same units. N2: nitrogen gas NH3: ammonia Ni: nickel NO: nitrogen oxide NO2: nitrogen dioxide NOx: nitrogen oxides non-volatile particles: particles that exist at engine exit plane temperature and pressure conditions2 nucleation: the process of initial formation of a particle from vapor. This process is usually facilitated by the presence of small particles called condensation nuclei, which serve as sites for condensation.3 OPS: optical particle spectrometer organic carbon: often abbreviated as OC, is a major compo- nent of particulate carbon and is composed of many com- pounds, most of which partition between the gas and aerosol phases at ambient conditions parameterization: expression in terms of statistically repre- sentative characteristics. parts per million (ppmv): the unit volume concentration of a gas per million unit volumes of the gas mixture of which it is part. (Also applicable to mass measurements and referred to as ppmm)4 PM10, PM2.5, PM1.0: regulatory designations of particulate matter less than or equal to 10 micrometers, 2.5 micrometers, and 1.0 micrometers, respectively, in diameter. These measures are similar to the terms coarse, fine, and ultrafine, respectively. PMex: particle extinction monitor PTR-MS: proton transfer reaction mass spectrometer RPM: revolutions per minute Smoke: small gas-borne solid particles, including but not limited to black carbonaceous material from the burning of fuel, which in sufficient concentration create visible opacity smoke number: often abbreviated as SN, the dimensionless term quantifying smoke emission. SN increases with smoke density and is rated on a scale from 0 to 100. SN is evaluated for a sample size of 16.2 kg of exhaust gas/m2 (0.0239 lb/in2) of filter area. Soluble mass fraction: the fraction of the aerosol mass that is soluble in water SO2: sulfur dioxide total carbon: the sum of elemental carbon and organic carbon5 transients: momentary or temporary variation in a variable of interest, e.g., engine power, ambient pressure, temperature. UHC: unburned hydrocarbon VOC: volatile organic compound volatile particles: particles formed from condensable gases after the exhaust has been cooled to below engine exit conditions 2 Society of Automotive Engineers Aerospace Information Report 5892 copy- right © 2007 SAE. 3 Baron P.A. and Willeke, K. (Eds.) Aerosol Measurementa Principles, Techniques and Applications, 2nd Edition, John Wiley and Sons, New York, 2001. 4 Society of Automotive Engineers Aerospace Information Report 5892 copy- right © 2007 SAE. 5 Society of Automotive Engineers Aerospace Information Report 5892 copy- right © 2007 SAE.