(273g) Jet Aircraft Non-Volatile Particulate Matter Characterization and Estimation

Jet engine aircraft exhaust contains combustion byproducts and particulate matter in the form of non-volatile particulate matter (nvPM), black carbon (BC) is used synonymously for nvPM throughout this paper. Aircraft cruise emissions are the only direct source of anthropogenic BC particles at altitudes above the tropopause.¹ Black carbon aerosols are strong solar radiation absorbers and have long atmospheric lifetimes.² Therefore, BC results in positive radiative forcing and is believed to be the second largest contributor to climate change.³ Additionally, upper troposphere and lower stratosphere BC particles contribute to climate forcing indirectly by acting as ice nucleation sites and cloud activators.^4-6 With regards to human health, a link between cardiopulmonary diseases and carbonaceous black particulate matter has recently been suggested.⁷ As concern for human health risks and environmental impacts caused by aviation BC emissions increases, emission reduction strategies will need to be implemented. An ambitious carbon, solid and gaseous, emission reduction goal of 50% reduction by 2050 as compared to 2000-2005 levels have already been defined by the International Air Transport Association and Advisory Council for Aviation Research and Innovation in Europe.⁸ Meeting these goals will require significant engineering advancements requiring a long implementation period. However, in the near term, alternative jet fuels with reduced aromatic content are an attractive solution for reducing BC emission.^9-12 Alternative aviation fuels containing synthetic blend components with near zero aromatic content (synthetic paraffinic kerosenes, SPKs) such as those synthesized via the Fischer-Tropsch (FT-SPK) process and hydrotreated esters and fatty acids (HEFA-SPK) overall contain highly reduced aromatic content compared to conventional fuel and thus significantly reduce aircraft engine BC emissions.^9-12

Currently there is not a direct regulation on BC emissions from jet engines. Rather, BC emissions during the landing and take-off (LTO) cycle are limited by the International Civil Aviation Organization (ICAO) through regulations on smoke number (SN).¹³ The smoke number regulation introduced in 1981 was put in place with the purpose of reducing plume visibility and no engines have failed this regulation since 1990.¹⁴ With increasing concern on both human health and environmental impacts caused by jet engine BC emissions the EPA is expected to place regulations on such emissions.¹⁵ The ICAOâ??s Committee on Aviation Environmental Protection is currently developing a regulatory standard for BC emissions. The pending regulation will require BC emissions from new jet engines to be measured by a standard procedure. A standardized measurement methodology was defined in the Aerospace Information Report 6241¹⁶,with much of the research effort led by Missouri University of Science and Technology¹⁷. Such a regulation would likely apply to new engines with the existing fleet grandfathered in. However, in-service engine lifetimes can be in excess of 20 years and current engine designs will continue to be manufactured for several more years. Therefore, predictive tools capable of accurately estimating BC emissions from the current in-service fleet will be needed for the next couple decades to quantify atmospheric BC inventory from aviation.

Current models do not accurately predict BC emissions. The First Oder Approximation-3 (FOA3) methodology is used worldwide for estimating BC emissions within the vicinity of airports.¹⁵ The FOA3 was endorsed by the (ICAO)¹⁸ in February 2007 and relies on a measured SN to predict BC emission. Black carbon is most often reported as an emission index of black carbon (EI_BC), reported as milligrams of BC emitted per kilogram of fuel combusted. Due to inaccuracies in measuring low SNs produced by modern high bypass ratio engines, the FOA3 and its modifications are unreliable. Recently a kinetic model based on formation and oxidation rates termed the FOX method was reported.¹⁹ The FOX does not require input of a SN, instead the input variables are engine conditions. Hence, the FOX avoids the measurement error built into the FOA3. However, the FOX is fuel independent and cannot be applied to predict EI_BC from alternative fuels and alternative fuels blended with conventional jet fuels. Both the FOA3 and the FOX methods are designed to predict EI_BC at ground level, which is important for assessing human health concerns at and in the vicinity of airports, however, it is the cruise EI_BC that is of the most importance in determining the role aviation BC plays on the Earthâ??s radiative balance. The current practice to arrive at a predicted cruise EI_BC is to scale ground values with an additional kinetic type expression, the DoÌ?pelheuer and Lecht relation. At the time the DoÌ?pelheuer and Lecht relation was developed there were limited cruise BC emission measurements. The available data was not representative of real aviation emissions because the aircraft operated at reduced weight and velocities compared to regular operation.

In this work current predictive methods are evaluated for accuracy by comparison to over a decadeâ??s worth of field campaign data collected by the National Aeronautics and Space Administrationâ??s (NASA) Langley Aerosol Research Group with inclusion of cruise data.⁹ An improved semi-empirical method is developed. Accurate engine condition relations are developed based on proprietary engine cycle data for a common rich-quench-lean (RQL) style combustor. Alternative fuels and fuel blend predictive relations are developed as well as a direct cruise prediction. The intent is to provide an improved method to calculate EI_BC from in-service aircraft and account for EI_BC reductions from the use of alternative fuels.

References

1. Peck, J.; Oluwayemisi, O; Wong, H; Miake-Lye, R. An algorithm to estimate cruise black carbon emissions for use in developing a cruise emissions inventory. J. Air Waste Manage. Assoc. 2013, 63, 367-375.

2. Lee, D. S.; Fahey, D. W.; Forster, P. M.; Newton, P. J.; Wit, R. C. N.; Lim, L. L.; Owen, B.; Sausen, R. Aviation and global climate change in the 21st century. Atmos. Environ. 2009, 43, 3520-3537.

3. Bond, T.; Doherty, S.; Fahey, D.; Forster, P.; Berntsen, T.; DeAngelo, B.; Flanner, M.; Ghan, S.; Karcher, B.; Koch, D.; Kinne, S.; Kondo, Y.; Quinn, P.; Sarofim, M.; Schultz, M.; Schulz, M.; Venkataraman, C.; Zhang, H.; Zhang, S.; Bellouin, N.; Guttikunda, S.; Hopke, P.; Jacobson, M.; Kaiser, J.; Klimont, Z.; Lohmann, U.; Schwarz, J.; Shindell, D.; Storelvmo, T.; Warren, S.; Zender, C. Bounding the role of black carbon in the climate system: A scientific assessment. J. Geophys. Res.: Atmos. 2013, 118, 5380-5552.

4. Haywood, J. M.; Shine, K. P. The Effect of Anthropogenic Sulfate and Soot Aerosol on the Clear-Sky Planetary Radiation Budget. Geophys. Res. Lett. 1995, 22, 603-606

5. Karcher, B.; Peter, T.; Biermann, U. M. Schumann, U. The Initial Composition of Jet Condensation Trails. J. Atmos. Sci.1996, 53, 3066-3083.

6. Heymslield, A. J.; Lawson, R. P.; Sachse, G. W. Growth of Ice Crystals in Precipitating Contrail. Geophys. Res. Lett. 1998, 25, 1335-1338.

7. Pope, C. A.; Dockery, D. W. Health effects of fine particulate air pollution: Lines that connect. J. Air Waste Manage. Assoc. 2006, 56, 709-742.

8. Realising Europeâ??s Vision for Aviation: Strategic Research & Innovation Agenda (Executive Summary); Advisory Council for Aviation Research and Innovation in Europe (ACARE): Brussels, Belgium, 2012.

9. Moore, R.; Shook, M.; Beyersdorf, A.; Corr, C.; Herndon, S.; Knighton, W.; Miake-Lye, R.; Winstead, S.; Yu, Z.; Ziemba, L.; Anderson, B. Influence of Jet Fuel Composition on Aircraft Engine Emissions: A synthesis of aerosol emissions data from the NASA APEX, AAFEX, and ACCESS missions. Energy Fuels 2015, 29, 2591-2600.

10. Timko, M. T.; Herndon, S. C.; Blanco, E. R.; Wood, E. C.; Yu, Z.; Miake-Lye, R. C.; Knighton, W. B.; Shafer, L.; DeWitt, M. J.; Corporan, E. Combustion products of petroleum jet fuel, a Fischerâ??Tropsch synthetic fuel, and a biomass fatty acid methyl ester fuel for a gas turbine engine. Combust. Sci. Technol. 2011, 183, 1039-1068.

11. Corporan, E.; Dewitt, M. J.; Belovich, V.; Pawlik, R.; Lynch, A. C.; Gord J. R.; Meyer, T. R. Emissions characteristics of a turbine engine and research combustor burning a Fischerâ??Tropsch jet fuel. Energy Fuels 2007, 21, 2615â??2626.

12. Cain, J.; DeWitt, M.J.; Blunck, D.; Corporan, E.; Striebich, R.; Anneken, D.; Klingshirn, C.; Roquemore, W.; Vander Wal, R. Characterization of gaseous and particulate emissions from a turboshaft engine burning conventional, alternative, and surrogate fuels. Energy Fuels 2013, 27, 2290-2302.

13. ICAO. ICAO Annex 16: Environmental Protection, Volume II â?? Aircraft Engine Emissions; International Civil Aviation Organization: Montreal, Canada, 2008.

14. EASA ICAO Engine Emissions Databank [online]. Available at: http://easa.europa.eu/document-library/icao-aircraft-engine-emissions [Accessed 4 Jan 2016].

15. Wayson, R. L.; Fleming, G. G.; Lovinelli, R. Methodology to estimate particulate matter emissions from certified commercial aircraft engines. J. Air Waste Manage. Assoc. 2009, 59, 91-100.  

16. SAE. Aerospace Information Report AIR6241 Procedure for the Continuous Sampling and Measurement of Non-Volatile Particle Emissions from Aircraft Turbine Engines; SAE International: Warrendale, PA, 2013.

17. Lobo, P.; Durdina, L.; Smallwood, G. J.; Rindlisbacher, T.â?? Siegerist, F.; Black, E. A.; Wang, J. Measurement of aircraft engine non-volatile PM emissions: Results of the aviation-particle regulatory instrumentation demonstration experiment (A-PRIDE) 4 campaign. Aerosol Sci. Technol. 2015, 49, 472-484.

18. ICAO. Airport Air Quality Guidance Manual; International Civil Aviation Organization: Montreal, Canada, 2011.

19. Stettler, M. E. J.; Boise, A. M.; Petzold, A.; Barrett, S. R. H. Global civil aviation black carbon emissions. Environ. Sci. Technol. 2013a, 47, 10397-10404.