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OCR for page 33
33 Glossary Advected plume--wind-transported exhaust plume, subject to local and Airport-Related Hazardous Air Pollutants: Research Needs and meteorological conditions Analysis) Aircraft gas turbine engine1--any gas turbine engine used for aircraft Line loss--percent of particles lost during transit through a given sam- propulsion or for power generation on an aircraft, including those ple line; particle loss mechanisms include impaction, diffusion, commonly called turbojet, turbofan, turboprop, or turboshaft type settling (gravitational), and thermophoresis (thermodiffusion) engines Lognormal3--a normal distribution that is the distribution of the Black carbon--nonvolatile diesel particulate matter, often used inter- logarithm of a random variable changeably with soot or elemental carbon (see below), although it Normal distribution2--a probability density function that approximates is most often used when discussing optical properties the distribution of many random variables (as the proportion of out- Classical aerodynamic diameter1--diameter of an equivalent unit den- comes of a particular sort in a large number of independent repeti- sity sphere with the same settling velocity in still air as the particle tions of an experiment in which the probabilities remain constant in question from trial to trial) and that has the form f(x) = (1/(2)) Coarse particle2--particle with a classical aerodynamic diameter be- e(-1/2[(x - )/]2 where is the mean and is the standard deviation tween 2.5 and 10 m Nonroad--mobile emission sources not commonly operated on pub- Deposition--an airborne pollutant that reaches the ground by force of lic roadways such as airport ground support equipment, lawn gravity, rain, or by attaching to other particles mowers, etc. EIm1--Emission Index (mass), the mass of emissions of a given con- Nonvolatile particles1--particles that exist at engine exit plane tem- stituent per thousand mass units of fuel burned (e.g., g/kg fuel); perature and pressure conditions also total mass of particulate emissions in the same units Nucleation4--the process of initial formation of a particle from Elemental carbon1--often referred to as EC and frequently used inter- vapor; this process is usually facilitated by the presence of small changeably with black carbon and soot, although it is most often particles called condensation nuclei, which serve as sites for used when referring to chemical properties; the refractory carbon condensation found in combustion-generated particulate matter; the portion of Organic carbon2--often referred to as OC, is a major component of a sample of combustion-generated particulate matter that remains particulate carbon and is composed of many compounds, most of after volatile components have been removed; also known as which partition between the gas and aerosol phases at ambient con- graphitic carbon ditions and are referred to as semi-volatile organic compounds Engine exit plane--any point within the area of the engine exhaust (SVOC) (EPA) nozzle at an axial distance within 0.5 diameters (or equivalent, if Parameterization--to express in terms of statistically representative not circular) downstream from the outer edge of the nozzle characteristics Fine particle2--particle with a classical aerodynamic diameter less than Parts per million (ppmv) --the unit volume concentration of a gas per 2.5 m million unit volumes of the gas mixture of which it is part; also Geometric mean2--the nth root of the product of n numbers applicable to mass measurements as referred to as ppmm1 HAPs--hazardous air pollutants, 188 pollutants that the Clean Air Act Photochemical--the interaction of atoms, molecules, and light Amendments of 1990 required EPA to regulate; also referred to as PM10, PM2.5, PM1.0--regulatory designations of particulate matter less "air toxics"; the complete list of pollutants can be found in Appen- than or equal to 10 micrometers, 2.5 micrometers, and 1.0 microm- dix C: The Clean Air Act Amendments of 1990 List of Hazardous eters, respectively, in diameter; these measures are similar to the Air Pollutants and on the EPA website: terms coarse, fine, and ultrafine, respectively orig189.html; for the purpose of this report, particulate matter, Primary particle--a particle that is emitted directly from the source while hazardous and potentially toxic, are not included in the Refractory--resistant to heat: nonvolatile definition of HAPs (See also related report ACRP 02-03, Aircraft 3 Definition from Merriam-Webster Online Dictionary, copyright 2005, Merriam- 1 Webster, Inc. Definition from Society of Automotive Engineers, Aerospace Information Report 4 5892, copyright 2007, Society of Automotive Engineers. Definition from Baron P.A. and Willeke K. (eds) Aerosol Measurement Princi- 2 ples, Techniques and Applications, 2nd ed., John Wiley and Sons, New York, 2001. Definition from

OCR for page 33
34 Secondary particle--a particle that forms as the result of a chemical reac- Soot--nonvolatile diesel particulate matter, also referred to as black tion or other means by combining with other elements after leaving carbon or elemental carbon (see above) the source Total carbon1--the sum of elemental carbon and organic carbon Smoke--Small gas-borne solid particles, including but not limited to Transients--a momentary or temporary variation in a variable of interest, black carbonaceous material from the burning of fuel, which in suf- e.g., engine power, ambient pressure, temperature ficient concentration create visible opacity Ultrafine particles--particles with a classical aerodynamic diameter of Smoke number (SN)--the dimensionless term quantifying smoke less than 0.1 m emission; SN increases with smoke density and is rated on a scale Volatile particles1--particles formed from condensable gases after the from 0 to 100; SN is evaluated for a sample size of 16.2 kg of exhaust exhaust has been cooled to below engine exit conditions gas/m2 (0.0239 lb/in2) of filter area