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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Gas Turbine Engine Emissions—Part II: Chemical Properties of Particulate Matter

[+] Author and Article Information
Michael T. Timko, Timothy B. Onasch, Megan J. Northway, John T. Jayne, Manjula R. Canagaratna, Scott C. Herndon, Ezra C. Wood, Richard C. Miake-Lye

 Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976

W. Berk Knighton

Department of Chemistry, Montana State University, P.O. Box 173400, Bozeman, MT 59717-3400

J. Eng. Gas Turbines Power 132(6), 061505 (Mar 19, 2010) (15 pages) doi:10.1115/1.4000132 History: Received April 13, 2009; Revised July 07, 2009; Published March 19, 2010

The characterization of volatile and nonvolatile particle materials present in gas turbine exhaust is critical for accurate estimation of the potential impacts of airport activities on local air quality, atmospheric processes, and climate change. Two field campaigns were performed to collect an extensive set of particle and gaseous emission data for on-wing gas turbine engines. The tests included CFM56, RB211-535E4-B, AE3007, PW4158, and CJ610 engines, providing the opportunity to compare emissions from a wide range of engine technologies. Here we report mass, number, composition, and size data for the nonvolatile (soot) and volatile particles present in engine exhaust. For all engines, soot emissions (EIm-soot) are greater at climbout (85% power) and takeoff (100%) power than idle (4% or 7%) and approach (30%). At the engine exit plane, soot is the only type of particle detected. For exhaust sampled downwind (15–50 m) and diluted by ambient air, total particle number emissions (EIn-total) increases by about one or two orders of magnitude relative to the engine exit plane, and the increase is driven by volatile particles that have freshly nucleated in the cooling exhaust gas both in the free atmosphere and in the extractive sample lines. Fuel sulfur content is the determining factor for nucleation of new particles in the cooling exhaust gases. Compositional analysis indicates that the volatile particles consist of sulfate and organic materials (EIm-sulfate and EIm-organic). We estimate a lower bound S[IV] to S[VI] conversion efficiency of (0.08±0.01)%, independent of engine technology. Measurements of EIm-organic ranged from about 0.1mgkg1 to 40mgkg1. Lubrication oil was present in particles emitted by all engines and accounted for over 90% of the particulate organic mass under some conditions. The products of incomplete combustion are a likely source of the remaining volatile organic particle material.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Representative scanning mobility particle sizer (SMPS) data obtained during testing of a CFM56-7B22 engine (65% power). Data from samples collected at both 1 and 50 m are shown.

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Figure 2

Comparison of EIm-soot for the major engine technologies. A separate vertical axis was used to plot EIm-soot for the RB11-535E4-B so that the low power qualitative trends for the different engine types would be more easily distinguishable. For each engine type depicted, all available data points were averaged.

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Figure 3

Comparison of EIm-soot for just the CFM56-3B1 engines. The composite average for all CFM56-3B1 engines is shown for comparison and to guide the eyes.

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Figure 4

EIn-total (measured at 1 m) and EIm-soot (averaged over all available sampling locations) for an (a) AE3007-A1E and an (b) PW4158 engine. Panel (c) shows volume weighted peak diameters for the SMPS particle size distributions measured at 1 m.

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Figure 5

EIm-sulfate (30/43 m sampling probe) for two engines: (a) N14324 and CFM56-3B1, and (b) N74856 and RB211-535E4-B. Size-resolution data were used to apportion the organic PM mass to the nucleation/growth mode (10–50 nm), a soot condensation mode (50–300 nm), and an ambient mode (300–1000 nm)

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Figure 6

EIm-sulfate (30/43 m sampling probe) for all of the APEX-2/3 turbofan engines except AE3007s (internally mixed engines) and CJ6108A plotted as a function of measured fuel sulfur content. Only data at high power (80% or 85%) are included, as the capture efficiency of the aerosol mass spectrometer is maximized at these conditions. The data from APEX-1 are included for completeness and to expand the fuel sulfur content range. A best fit line for the entire data set is shown (R2=0.85).

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Figure 7

Mass spectra of exhaust gas samples from three engines (CJ6108A, CFM56-3B1, and RB211-535E4-B) and two lubrication oils (Mobil II and Air BP). Mass spectra of the lubrication oils were obtained by aerosolizing oil samples obtained from the engines (Mobil II from the RB211-535E4-B and Air BP from CFM56-3B1). Characteristic m/z signals are highlighted for easy reference. The m/z=27/29, 41/43, 55/57 series is due to hydrocarbons. The m/z=85, 113, 127 series is likely due to the synthetic esters in lubrication oil.

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Figure 8

Downstream measurements of EIn-total plotted as a function of fuel sulfur content for all of the engines studied in APEX-2/3 and the high sulfur data from APEX-1 (1600 ppm fuel sulfur). The outlying high-power data point (N14324/CFM56-3B1) had high EIm-soot. The lines are intended to guide the eyes, not to imply a definitive physical relationship. The marker size is proportional to dilution ratio—larger markers have a lower percentage of exhaust gas relative to ambient air.

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Figure 9

Downstream AMS measurements of condensed organic and sulfate materials emitted by the CFM56-3B1 engine of a B737 aircraft (N14324). The calculated particle transmission efficiency is shown based on the data from Ref. 50. In (a) at idle, a significant nucleation mode is visible at about 25 nm. The AMS is unable to detect particles smaller than about 30 nm, so the peak depicted at about 25–30 nm appears as a result of limited transmission of particles <50 nm—the true peak is almost certainly smaller.

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