Article pubs.acs.org/est
Impact of Alternative Fuels on Emissions Characteristics of a Gas Turbine Engine − Part 1: Gaseous and Particulate Matter Emissions Prem Lobo,*,†,‡ Lucas Rye,§ Paul I. Williams,∥,⊥ Simon Christie,‡ Ilona Uryga-Bugajska,# Christopher W. Wilson,§ Donald E. Hagen,† Philip D. Whitefield,† Simon Blakey,§ Hugh Coe,⊥ David Raper,‡ and Mohamed Pourkashanian# †
Center of Excellence for Aerospace Particulate Emissions Reduction Research, Missouri University of Science and Technology, Rolla, Missouri 65409, United States ‡ Centre for Air Transport and the Environment, Manchester Metropolitan University, Manchester M1 5GD, United Kingdom § Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom ∥ National Centre for Atmospheric Science, University of Manchester, Manchester M13 9PL, United Kingdom ⊥ School of Earth, Atmospheric and Environmental Science, University of Manchester, Manchester M13 9PL, United Kingdom # Centre for Computational Fluid Dynamics, University of Leeds, Leeds LS2 9JT, United Kingdom S Supporting Information *
ABSTRACT: Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NOx emissions and 5−10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number.
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INTRODUCTION The impact of airport operations on local air quality in and around airports is of prime importance as airports expand to accommodate increased demand in air traffic. A growing number of airports around the United States and in Europe are studying measures to assess and reduce airport emissions. Aircraft engines and auxiliary power units (APUs) are significant contributors to the emissions inventory at airports. Several studies in recent years have focused on quantifying the impact of airport operations on local air quality.1−5 Particulate matter (PM) from aircraft © 2012 American Chemical Society
engines presents a unique source of emissions in the urban environment.6−8 The development of alternative fuels for use in gas turbine engines has been gaining momentum. Fuels derived from biomass via hydroprocessing, or synthesis from coal or natural gas via the Received: Revised: Accepted: Published: 10805
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Table 1. Properties of Fuelsa Being Studied fuel
density (g/L) @15 °C
energy content (MJ/kg)
fuel H/C ratiob
fuel sulfur content (ppm)
fuel aromatic content (% vol)
Jet A-1 CTL GTL 50:50 GTL:Jet A-1
801.9 781.2 737.9 769.9
43.2 43.7 43.8 43.5
1.90 2.14 2.20 2.05
700 100 5 352.5
18.5 10.9 0 9.2
a
Density, energy content, and sulfur and aromatic content for the test fuels was supplied by Royal Dutch Shell for Jet A-1, GTL, and 50:50 GTL:Jet A-1, and sourced from the literature for CTL.18 bFuel H/C ratio was calculated using GC × GC data.23
specifications for aviation fuel. The RME fails to meet the freeze point, energy content, and density specifications, while diesel does not satisfy the specification in terms of the boiling point distribution and energy content. The GC-FID chromatograms for selected test fuels are presented in Figure 1 to highlight differences in fuel composition
Fischer−Tropsch (FT) process, are being considered for use in the aviation sector as “drop-in” alternative fuels.9 Synthetic paraffinic kerosene (SPK) produced from either coal (coal-toliquid, CTL) or natural gas (gas-to-liquid, GTL) via the FT process has been successfully used as a drop-in alternative fuel and requires little or no modification of the existing infrastructure. Several flight demonstrations of commercial aircrafts burning various blends of conventional jet fuel and either biomass or FT fuels have been conducted recently.10 Also, a new fuel specification for up to 50% blends of synthetic fuel with conventional jet fuels has recently been adopted by the American Society for Testing and Materials (ASTM).11 Measurement studies focusing on the use of alternative fuels in military and commercial aircraft engines have shown that alternative fuels significantly reduce PM emissions,12−14 and thereby increase the potential for local air quality benefits. As new alternative fuels for aviation applications continue to be developed, their overall impact on the environment in terms of energy use and emission burdens of the entire life cycle from well to wake are being examined.15−17 The impact of the aircraft engines burning these alternative fuels on the environment as the emissions evolve after combustion has not been fully explored. The lack of availability of aircraft engines for emissions testing using alternative fuels and the costs associated with running such engines make them impractical to use for such evaluation applications. APUs, however, are well suited to perform evaluations of alternative fuels for use in the aviation sector. This paper summarizes the results of an experimental campaign to evaluate the gaseous and PM emissions characteristics of an aircraft APU burning several alternative fuels. The study was conducted at the University of Sheffield’s Low Carbon Combustion Centre in September/October 2009 and involved teams from the University of Sheffield, Missouri University of Science and Technology (Missouri S&T), the University of Manchester, and Manchester Metropolitan University. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the APU.
Figure 1. GC-FID chromatograms for the Jet A-1 and GTL fuels tested.
of conventional Jet A-1 versus an alternative GTL fuel. The spectra were obtained using a Perkin and Elmer autosystem XL gas chromatograph fitted with a general purpose ZB-5 column (7HG-G002-11), and are similar in properties to those reported for conventional and FT fuels.24 An Auto System FID was used as the detector. Fluka gas chromatograph standards (n-alkane) were sourced from Sigma Aldrich to aid identification. Operation of this instrument, including configuration, is reported elsewhere.23
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EXPERIMENTAL METHODS Engine and Test Conditions. A recommissioned Artouste Mk113 APU, located at the University of Sheffield’s Low Carbon Combustion Centre, was used as the test bed for the emissions measurements. The APU was instrumented to monitor and record key engine operating conditions, such as temperatures, pressures, engine RPM, fuel flow rates, etc. The combustor conditions were varied by altering APU load, thus allowing for direct control over the air/fuel ratio. Exhaust gas temperature (EGT) was measured using a thermocouple installed (by the manufacturer) in the exhaust gas flow. PM and gaseous emissions were sampled at an idle (no load) and then a full power (load) condition, before returning the engine to a hot idle condition prior to engine shutdown. Sampling at a selected test condition was conducted over a six minute interval, beginning once the APU had stabilized. Table 2 lists the nominal values for selected APU operational parameters achieved when the APU was burning Jet A-1 at the two operating conditions, idle and full power. Sampling System. One gas and two PM sampling probes were mounted on a stainless steel plate positioned half an exhaust
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FUEL PROPERTIES The fuels used in this study along with their properties are listed in Table 1. The Jet A-1, GTL, and 50:50 GTL:Jet A-1 fuels were supplied by Royal Dutch Shell, with the coal based synthetic CTL provided by Rolls-Royce. The CTL fuel is a fully synthetic jet fuel developed by Sasol for certification testing.18 The Jet A-1 and CTL fuels meet current specifications, i.e., ASTM D165519 and DEF STAN 91-91,20 respectively. The GTL fuel fails to meet the specification due to its lack of aromatic characteristics. Both neat and blended GTL fuels do not satisfy the ASTM minimum specification density. Two other fuels, a rapeseed methyl ester (RME) and a diesel fuel, were also evaluated during the study21,22 but were not included in this analysis since they do not meet the 10806
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Sable System CA-2A NDIR detector. These two measurements provided an accurate assessment of the dilution factor for the PM exhaust samples. The PM emissions characterization instrumentation suite included two Cambustion DMS500s26,27 to gather real-time size distribution information and number concentrations of exhaust PM from 5 nm to 1000 nm. One DMS500 measured the total PM, while the second DMS500 had an upstream thermal denuder (operating at 300 °C) to remove any volatile PM and thus measured the nonvolatile PM (nvPM). The DMS500 size distribution data were corrected for transmission losses using previously reported20 size dependent loss functions for both total and nonvolatile PM. PM number concentrations were determined by integrating the area under the size distribution curves, and PM mass concentrations were computed in a similar manner by assuming particle sphericity and a density of 1 g/cm3. A high resolution, time-of-flight aerosol mass spectrometer (HR-ToF-AMS)28,29 measured the submicrometer, nonrefractory PM composition with a 100% transmission window between 60 and 600 nm.
Table 2. Nominal APU Operating Conditions APU operating condition
RPM
fuel flow rate (kg/h)
fuel air ratio
EGT (°C)
idle full power
22 541 34 463
57 109
0.0125 0.0131
445 460
diameter behind the APU engine exhaust plane. These probes have been used in previous measurement campaigns to extract PM and gas samples from a gas turbine engine burning conventional and alternative fuels.6,14 Details of the exit plane probes and sampling system have been previously reported.21 Another PM probe (50.8 mm o.d.) was positioned approximately 10 m from the APU exit plane to sample the exhaust after it had cooled and mixed with ambient air. A probe to extract samples for polycyclic aromatic hydrocarbon (PAH) analysis was located midway between the engine exit plane and the downstream probe, and the results of this analysis are presented elsewhere.25 Gaseous exhaust was sampled via the water cooled gas probe and transferred through a 6.35 mm o.d. heated line maintained at 150 °C before being split using a y-connector between the gaseous analysis suite and a smoke meter, both operated by the University of Sheffield. For the PM samples extracted at the engine exit plane, one probe (PM probe 1) was designed to provide tip dilution and the other (PM probe 2) permitted dilution to be introduced 1 m downstream of the probe tip. The PM sample was diluted to reduce and/or eliminate condensation, agglomeration, and gas-to-particle conversion in the sampling system. The point of introduction of dilution was varied to investigate the effects of downstream dilution, and the results of this portion of the study are presented elsewhere.22 The dilution flows for the exit plane PM probes were drawn from particle-free dry nitrogen gas. For the samples extracted from the 10 m PM sampling probe (PM probe 3), no dilution, other than that achieved by mixing with the ambient air, was provided. Typical dilution ratios achieved were greater than 10:1, and in many cases exceeded 20:1. PM exhaust samples were delivered to the Missouri S&T and the University of Manchester instrumentation suite located approximately ∼20 m away, using 9.52 mm o.d. (7.75 mm i.d.) stainless steel tubing. A switching box permitted sequential selection of PM samples from the three PM probes. The PM sampling lines were not actively heated, and thus, the sample temperature equilibrated to the ambient temperature a few meters from the sample extraction point. Data from PM probe 1 and PM probe 3 are presented in this paper. Instrumentation. A list of the instrumentation deployed in this study is presented in Table 3. CO2 was measured in the undiluted gaseous sample stream using a Rosemount Binos 1000 NDIR detector and in the diluted PM sample stream using a
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RESULTS AND DISCUSSION Emissions Measured at the Exit Plane. PM and gaseous emissions concentration data were converted to their respective emission indices to allow quantification of emissions per kilogram of fuel burned using the standard calculation.6,8,14,30 Average values of the nonvolatile PM number and mass-based emission indices, EIn and EIm, respectively, gas phase emission indices for NOx, CO, and UHC, along with smoke number (SN) measurements measured at the engine exit plane for the different fuels studied are presented in Table 4, along with 1σ measurement uncertainties. Eln and EIm values reported in Table 4 were obtained using the DMS500 data. General trends in the gas phase, nvPM emissions, and smoke number as a function of engine operating condition are consistent with those reported for other gas turbines engines; i.e., UHC and CO decrease with increasing engine power while NOx, nvPM, and SN increase with power.31,6,32 No statistically significant differences in NOx emissions were observed between Jet A-1 and the GTL and 50:50 GTL:Jet A-1 fuels, at idle and full power. For CTL, a 5% reduction in NOx is observed when compared to Jet A-1 at full power. Other studies investigating the NOx reduction from FT fuels on larger gas turbine engines have indicated a 5−10% reduction in NOx, attributed to the chemical differences between the alternative fuels and conventional jet fuel.32−34 Limited NOx related fuel effects were observed due to the lower primary zone flame temperature and combustor residence time of the APU. CO emissions were found to correlate well with fuel energy content (correlation coefficient: −0.84), i.e., the higher the fuel energy
Table 3. Gas and PM Emissions Characterization Instrument Suite instrument gas phase characterization gas phase characterization gas phase characterization gas phase characterization gas phase characterization smoke PM physical characterization
EcoPhysics CLA 700 EL ht NDIR Rosemount Binos 1000 NDIR Rosemount Binos 1000 Signal 3000-M hydrocarbon analyzer NDIR CO2 detector (Sable Systems CA-2A) Richard Oliver smoke meter Cambustion DMS500
PM chemical characterization
high resolution, time-of-flight aerosol mass spectrometer (HR-ToF-AMS) 10807
species measured
detection range
NO, NO2, NOx (nitrogen oxides) CO (carbon monoxide) undiluted CO2 UHC (unburned hydrocarbons) diluted CO2 smoke number total and nonvolatile PM size distribution and number concentration size resolved PM mass and composition
0−100 ppm 0−1500 ppm 0−5% 0−1000 ppm 0−5000 ppm 0−100 5−1000 nm 60−600 nm
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188.3 ± 59.5 84.9 ± 24.3 18.1 ± 5.1 66.1 ± 18.9 (1.9 ± 0.6) × 1016 (1.9 ± 0.7) × 1016 (0.3 ± 0.1) × 1016 (1.5 ± 0.5) × 1016 27.3 ± 0.6 10.3 ± 1.2 0.7 ± 0.6 6.3 ± 0.6 8.5 ± 3.4 7.0 ± 3.3 5.2 ± 3.5 6.0 ± 3.4 4.10 ± 0.05 3.87 ± 0.05 4.00 ± 0.05 4.01 ± 0.05 50.7 ± 14.1 12.9 ± 3.5 7.5 ± 2.7 10.5 ± 2.8 (1.2 ± 0.4) × 1016 (0.7 ± 0.2) × 1016 (0.02 ± 0.007) × 1016 (0.5 ± 0.2) × 1016 10.3 ± 0.6 2.6 ± 1.5 0.7 ± 0.6 2.0 ± 1.0
Figure 2. Total PM number size distributions at the downstream location measured with the DMS500 for the (a) idle and (b) full power conditions.
70.3 ± 0.3 67.0 ± 0.3 63.4 ± 0.2 65.2 ± 0.2 2.26 ± 0.09 2.13 ± 0.09 2.30 ± 0.09 2.31 ± 0.09 Jet A-1 CTL GTL 50:50 GTL:Jet A-1
fuel
content, the lower the CO emissions. Reductions in CO emissions, ranging from 5% to 10%, at idle were observed with the various alternative fuels. The reductions may be smaller in large gas turbine engines due to improved combustion efficiency. For UHC emissions at idle, the CTL fuel registered a 7% increase relative to Jet A-1, whereas a 40% reduction for the GTL and 30% reduction for 50:50 GTL:Jet A-1 was observed. Off-line analysis of PAH compounds in the exhaust stream revealed that CTL had the greatest mass of PAH followed by Jet A-1, 50:50 GTL:Jet A-1, and GTL,25 consistent with the UHC emissions data. The nvPM size distributions at idle and full power for all fuels have a mean particle size of ∼15 nm with a geometric standard deviation of 1.5. The greatest reductions in emissions were observed for nvPM at the idle condition. For EIn at idle, dramatic reductions of 99% were observed for the GTL fuel, with 60% reduction for 50:50 GTL: Jet A-1 and 42% reduction for CTL. For EIn at full power, the greatest reduction was measured with GTL (85%) followed by a 20% reduction with 50:50 GTL:Jet A-1. The EIn value for CTL at full power was the same as that for Jet A-1. The average EIm reductions compared to Jet A-1 at idle and full power were in the following order: GTL (90%) > 50:50 GTL:Jet A-1 (72%) > CTL (65%). The average reductions in SN for all alternative fuels relative to Jet A-1 followed the same trend as that for EIm, with GTL having the greatest reduction (95%) followed by 50:50 GTL:Jet A-1 (80%) and CTL (70%). These reductions in nvPM number and mass-based emission indices and SN are consistent with those reported in previous studies of gas turbine engines burning alternative fuels,14,32,33,35 with the greatest reductions occurring for fuels with the lowest aromatic content. Emissions Measured 10 m Downstream of Exit Plane. Figures 2 and 3 present the total PM number size distributions
39.8 ± 2.8 42.7 ± 2.7 25.6 ± 3.1 28.5 ± 3.0
EIn (#/kg fuel) SN idle CO (g/kg fuel) NOx (g/kg fuel)
UHC (g/kg fuel)
Article
28.3 ± 0.5 27.3 ± 0.5 28.3 ± 0.5 28.4 ± 0.5
EIm (mg/kg fuel) EIn (#/kg fuel) SN
full power
UHC (g/kg fuel) CO (g/kg fuel) NOx (g/kg fuel) EIm (mg/kg fuel)
APU operating condition
Table 4. Summary of Gaseous and Nonvolatile PM Emission Indices and Smoke Number for Different Fuels as a Function of APU Operating Condition Measured at the Engine Exit Plane
Environmental Science & Technology
and PM mass size distributions, respectively, sampled 10 m downstream of the engine exit plane. The total PM number size 10808
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Figure 4. PM organic and number-based emission indices as a function of fuel type, engine operating condition, and measurement location.
the downstream location, the EIorg values vary by a factor of 100 while EIn remains relatively constant (∼4 × 1016 particles/kg fuel burned). Also, while a small change in EIn is observed between the idle and full power conditions, a very significant variation in EIorg over the same conditions is found, implying that the condensation of organic species is the dominant process occurring as the plume evolves. A strong correlation between EIorg and EIm (correlation coefficient: +0.88) confirms that the increase in mass is a consequence of an organic coating on the surface of the PM (Figure 5).
Figure 3. PM mass size distributions at the downstream location measured with the HR-ToF-AMS for the (a) idle and (b) full power conditions.
distributions measured with the DMS500 include contributions from both nonvolatile PM and volatile PM, formed as a result of nucleation and condensation of species present in the gas phase at the engine exit plane, and have been corrected to account for ambient dilution. The PM mass size distributions measured with the HR-ToF-AMS provide a means to compare the various fuels in terms of their volatile PM content, present as organic coatings on the surface of the PM. The total PM number size distributions (Figure 2) indicate that the mean mobility particle diameter increases from idle to full power. EIn values at a given engine operating condition are essentially the same (within experimental uncertainty) for all fuels, averaging 5.4 × 1016 particles/kg fuel burned and 3.9 × 1016 particles/kg fuel burned, for idle and full power, respectively. PM mass distributions, differential mass concentrations plotted as a function of aerodynamic diameter (Figure 3), at idle show that Jet A-1 has a higher organic content than the other fuels. At full power, the PM mass distributions for Jet A-1 and CTL are similar, while that for GTL and 50:50 GTL:Jet A-1 show lower organic mass. The chemical composition of the organic PM measured during this study is discussed elsewhere.22 Plume Evolution. The PM emissions characteristics measured at the downstream location vary significantly from those measured at the engine exit plane. Fuel composition and nucleation/condensation of organic PM may be factors contributing to these observed differences. Figure 4 illustrates the correlation between PM organic and number-based emission indices (EIorg and EIn, respectively) between the engine exit plane and downstream sampling location for the four fuels being studied at the idle and full power operating conditions. The data can be grouped into two sections: exit plane data (red highlighted section) and downstream data (green highlighted section). At the engine exit plane, both EIorg and EIn are bound within a small range, with the exception of the GTL data point. EIorg for Jet A-1 at the exit plane idle condition was not measured, and hence, this data point does not appear on the plot. However, at
Figure 5. PM organic and mass-based emission indices as a function of fuel type, engine operating condition, and measurement location.
Impact of Alternative Fuels on Local Air Quality. The current projections for commercial air travel indicate a yearly increase of ∼5%.36 Alternative fuels are being considered as “drop in” replacements for conventional fuel to mitigate rising costs and security of supply of conventional jet fuel. Alternative fuels also have an additional benefit in that they have been shown to reduce nonvolatile PM emissions, and could potentially improve local air quality around airports. Studies have demonstrated that the fraction of volatile PM from gas turbine engines increases in the evolving plume.37,38 For local air quality assessments, both nonvolatile and volatile emissions need to be considered when developing PM emissions inventories, and are essential in understanding the impact of alternative fuels on the environment and in developing emissions mitigation and control strategies. A recent assessment of alternative aviation fuels 10809
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(11) ASTM D7566. Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons; ASTM International: West Conshohocken, PA. (12) Corporan, E.; DeWitt, M.; Belovich, V.; Pawlik, R.; Lynch, A. C.; Gord, J. R.; Meyer, T. R. Emissions characteristics of a turbine engine and research combustor burning a Fischer−Tropsch jet fuel. Energy Fuels 2007, 21, 2615−2626. (13) Anderson, B. E.; Beyersdorf, A. J.; Hudgins, C. H.; Plant, J. V.; Thornhill, K. L.; Winstead, E. L.; Ziemba, L. D.; Howard, R.; Corporan, E.; Miake-Lye, R. C.; Herndon, S. C.; Timko, M.; Wood, E.; Dodds, W.; Whitefield, P.; Hagen, D.; Lobo, P.; Knighton, W. B.; Bulzan, D.; Tacina, K.; Wey, C.; Vander Wal, R.; Bhargava, A.; Kinsey, J.; Liscinsky, D. S. Alternative Aviation Fuel Experiment (AAFEX); NASA/TM-2011217059, Hanover, MD; February 2011. (14) Lobo, P.; Hagen, D. E.; Whitefield, P. D. Comparison of PM emissions from a commercial jet engine burning conventional, biomass, and Fischer−Tropsch fuels. Environ. Sci. Technol. 2011, 45, 10744− 10749. (15) Bailis, R. E.; Baka, J. E. Greenhouse gas emissions and land use change from Jatropha Curcas-based jet fuel in Brazil. Environ. Sci. Technol. 2010, 44, 8684−8691. (16) Forman, G. S.; Hahn, T. E.; Jensen, S. D. Greenhouse gas emission evaluation of the GTL pathway. Environ. Sci. Technol. 2011, 45, 9084−9092. (17) Agusdinata, D. B.; Zhao, F.; Ileleji, K.; DeLaurentis, D. Life cycle assessment of potential biojet fuel production in the United States. Environ. Sci. Technol. 2011, 45, 9133−9143. (18) Moses, C. A.; Roets, P. N. J. Properties, characteristics and combustion performance of sasol fully synthetic jet fuel. J. Eng. Gas Turbines Power 2009, 131, 041502. (19) ASTM D1655. Standard Specification for Aviation Turbine Fuels; ASTM International: West Conshohocken, PA. (20) DEF STAN 91-91: Turbine Fuel, Aviation Kerosine Type, Jet A-1 NATO Code: F-35, Joint Service Designation: AVTUR, www.dstan. mod.uk. (21) Rye, L.; Lobo, P.; Williams, P. I.; Uryga-Bugajska, I.; Christie, S.; Wilson, C.; Hagen, D.; Whitefield, P.; Blakey, S.; Coe, H.; Raper, D.; Pourkashanian, M. Inadequacy of optical smoke measurements for characterisation of non-light absorbing particulate matter emissions from gas turbine engines. Combust. Sci. Technol. 2012, 184, DOI:10.1080/00102202.2012.697499. (22) Williams, P. I.; Allan, J. D.; Lobo, P.; Coe, H.; Christie, S.; Wilson, C.; Hagen, D.; Whitefield, P.; Raper, D. Impact of alternative fuels on emissions characteristics of a gas turbine engine. 2. Volatile and semivolatile particulate matter. Environ. Sci. Technol. 2012, DOI: 10.1021/es301899s. (23) Rye, L. The influence of alternative fuel composition on gas turbine combustion performance. Ph.D. Thesis, Department of Mechanical Engineering, University of Sheffield, 2012. (24) Corporan, E.; Edwards, T.; Shafer, L.; DeWitt, M. J.; Klingshirn, C.; Zabarnick, S.; West, Z.; Striebich, R.; Graham, J.; Klein, J. Chemical, thermal stability, seal swell, and emissions studies of alternative jet fuels. Energy Fuels 2011, 25, 955−966. (25) Christie, S.; Raper, D.; Lee, D. S.; Williams, P. I.; Rye, L.; Blakey, S.; Wilson, C. W.; Lobo, P.; Hagen, D.; Whitefield, P. D. Polycyclic aromatic hydrocarbon emissions from the combustion of alternative fuels in a gas turbine engine. Environ. Sci. Technol. 2012, 46, 6393−6400. (26) Reavell, K.; Hands, T.; Collings, N. A Fast Response Particulate Spectrometer for Combustion Aerosols; SAE Technical Paper 2002−01− 2714; 2002. (27) Hagen, D. E.; Lobo, P.; Whitefield, P. D.; Trueblood, M. B.; Alofs, D. J.; Schmid, O. Performance evaluation of a fast mobility-based particle spectrometer for aircraft exhaust. J. Propul. Power 2009, 25, 628−634. (28) DeCarlo, P. F.; Kimmel, J. R.; Trimborn, A.; Northway, M. J.; Jayne, J. T.; Aiken, A. C.; Gonin, M.; Fuhrer, K.; Horvath, T.; Docherty, K. S.; Worsnop, D. R.; Jimenez, J. L. Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer. Anal. Chem. 2006, 78, 8281− 8289.
indicated that the potential benefits may be offset by an increase in carbon emissions in the processes used to produce these fuels when considering climate impacts.39 Similar assessments for local air quality benefits have yet to be performed.
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ASSOCIATED CONTENT
S Supporting Information *
Exit plane nonvolatile PM number-based size distributions at idle and full power. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the sponsors. The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was separately funded by Royal Dutch Shell and the Federal Aviation Administration (FAA). FAA funding was through the Partnership for AiR Transportation for Noise and Emissions Reduction (PARTNER), an FAA-NASA-Transport Canada-US DoD-US EPA-sponsored Center of Excellence under Grant 07-C-NE-UMR Amendment 009 (Carl Ma, Project Manager).
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Environmental Science & Technology
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dx.doi.org/10.1021/es301898u | Environ. Sci. Technol. 2012, 46, 10805−10811
