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

# Gas Turbine Engine Emissions—Part I: Volatile Organic Compounds and Nitrogen Oxides

[+] Author and Article Information
Michael T. Timko

Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976timko@aerodyne.com

Scott C. Herndon, Ezra C. Wood, Timothy B. Onasch, Megan J. Northway, John T. Jayne, Manjula R. Canagaratna, 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), 061504 (Mar 19, 2010) (14 pages) doi:10.1115/1.4000131 History: Received April 13, 2009; Revised July 07, 2009; Published March 19, 2010

## Abstract

The potential human health and environmental impacts of aircraft gas turbine engine emissions during normal airport operation are issues of growing concern. During the JETS/Aircraft Particle Emissions eXperiment(APEX)-2 and APEX-3 field campaigns, we performed an extensive series of gas phase and particulate emissions measurements of on-wing gas turbine engines. In all, nine different CFM56 style engines (including both CFM56-3B1 and -7B22 models) and seven additional engines (two RB211-535E4-B engines, three AE3007 engines, one PW4158, and one CJ6108A) were studied to evaluate engine-to-engine variability. Specific gas-phase measurements include $NO2$, NO, and total $NOx$, HCHO, $C2H4$, CO, and a range of volatile organic compounds (e.g., benzene, styrene, toluene, naphthalene). A number of broad conclusions can be made based on the gas-phase data set: (1) field measurements of gas-phase emission indices (EIs) are generally consistent with ICAO certification values; (2) speciation of gas phase $NOx$ between NO and $NO2$ is reproducible for different engine types and favors $NO2$ at low power (and low fuel flow rate) and NO at high power (high fuel flow rate); (3) emission indices of gas-phase organic compounds and CO decrease rapidly with increasing fuel flow rate; (4) plotting EI-CO or volatile organic compound EIs against fuel flow rate collapses much of the variability between the different engines, with one exception (AE3007); (5) HCHO, ethylene, acetaldehyde, and propene are the most abundant volatile organic compounds present in the exhaust gases that we can detect, independent of engine technology differences. Empirical correlations accurate to within 30% and based on the publicly available engine parameters are presented for estimating EI-$NOx$ and EI-$NO2$. Engine-to-engine variability, unavailability of combustor input conditions, changing ambient temperatures, and complex reaction dynamics limit the accuracy of global correlations for CO or volatile organic compound EIs.

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## Figures

Figure 1

Comparison of 1 m and >15 m EI-NO2 data for an engine, which showed a large discrepancy (CJ6108A/N616NA), and one that did not (RB211-535E4-B/N74856)

Figure 2

NOx speciation for (a) RB211-535E4-B and (b) CJ6108A engines. ICAO data points (▶◀) are shown for reference.

Figure 3

Emission indices of several representative volatile organic compounds measured during the engine tests (a) EIs for formaldehyde, benzene, and naphthalene plotted as functions of engine power for a CFM56–3B1 engine (N353SW). (b) Relative ratios of important volatile organic compound emissions for several representative engines operating at idle for the measurement suite available to us.

Figure 4

Emission indices of gaseous pollutants plotted as functions of fuel flow rate for APEX-2/3 engines: (a) NO; (b) the NO2/NOx emission index ratio; (c) acetaldehyde, a representative volatile organic compound. Lines are shown to guide the eye and are not intended to convey physical significance.

Figure 5

EIm-NOx data for the CFM56 engines: (a) EIm-NOx plotted against power condition; (b) EIm-NOx plotted against fuel flow rate to remove engine-to-engine variability for CFM56 type engines

Figure 7

Comparison of (a) CO and (b) HCHO measurements with the correlations of Eqs. 7,8, respectively. Each data point is the average of all available replicate measurements at a given set of conditions (i.e., sample rake, power, etc.). Error bars are defined in the text. The CJ6108A (△) is an outlier in both regressions, as is the first plane in APEX-3 (▲, N14324). Values of best-fit parameters are listed in the figure and in Table 6.

Figure 6

Comparison of nitrogen oxide measurements to the Eq. 6 fit: (a) NOx; (b) NO2. Each data point is the average of all available replicate measurements at a given set of conditions (i.e., sample rake, power, etc.). Error bars are defined in the text. EI-NO2 was divided into two regimes based on power, ≤45% and >45%. Values of best-fit parameters are listed in Table 6. CJ6108A (not shown) is an outlier in the NO2 analysis.

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