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

Design Parameters for an Aircraft Engine Exit Plane Particle Sampling System

[+] Author and Article Information
Hsi-Wu Wong, Zhenhong Yu, Michael T. Timko, Scott C. Herndon, Elena de la Rosa Blanco, Richard C. Miake-Lye

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

Robert P. Howard

Aerospace Testing Alliance, Arnold Air Force Base, TN 37389

J. Eng. Gas Turbines Power 133(2), 021501 (Oct 26, 2010) (15 pages) doi:10.1115/1.4001979 History: Received March 12, 2010; Revised June 02, 2010; Published October 26, 2010; Online October 26, 2010

The experimental data and numerical modeling were utilized to investigate the effects of exhaust sampling parameters on the measurements of particulate matter (PM) emitted at the exit plane of gas-turbine engines. The results provide guidance for sampling system design and operation. Engine power level is the most critical factor that influences the size and quantity of black carbon soot particles emitted from gas-turbine engines and must be considered in sampling system design. The results of this investigation indicate that the available soot surface area significantly affects the amount of volatile gases that can condense onto soot particles. During exhaust particle measurements, a dilution gas is typically added to the sampled exhaust stream to suppress volatile particle formation in the sampling line. Modeling results indicate that the dilution gas should be introduced upstream before a critical location in the sampling line that corresponds to the onset of particle formation microphysics. Also, the dilution gas should be dry for maximum nucleation suppression. In most aircraft PM emissions measurements, the probe-rake systems are water cooled and the sampling line may be heated. Modeling results suggest that the water cooling of the probe tip should be limited to avoid overcooling the sampling line wall temperature and, thus, minimize additional particle formation in the sampling line. The experimental data show that heating the sampling lines will decrease black carbon and sulfate PM mass and increase organic PM mass reaching the instruments. Sampling line transmission losses may prevent some of the particles emitted at the engine exit plane from reaching the instruments, especially particles that are smaller in size. Modeling results suggest that homogeneous nucleation can occur in the engine exit plane sampling line. If newly nucleated particles, typically smaller than 10 nm, are indeed formed in the sampling line, sampling line particle losses provide a possible explanation, in addition to the application of dry diluent, that they are generally not observed in the PM emissions measurements.

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Figures

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Figure 1

Schematic representation of an engine exit plane particle sampling system: (a) sampling rake configuration, (b) probe tip with cooling water and dilution gas, and (c) the geometry of the modeled sampling system and where the sampling system is located in the exhaust plume

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Figure 2

Modeling results describing representative particulate matter evolution in an engine exit plane particle sampling system: (a) temperature and relative humidity evolution, (b) concentration (N) and size (Dp) evolution of liquid droplets, (c) concentration (N) and size evolution of liquid embryos, (d) size evolution of coated soot particles, and (e) evolution of SVI mass fraction

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Figure 3

Measured particle size distributions normalized to the emitted CO2 concentrations for idle and take-off fuel flow conditions during the first F100 test (note that the discontinuous particle size distributions are caused by signal noise, short scanning time, and resolution of the bin size)

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Figure 4

(a) Measured sulfate (SO4) and organic mass emission index (EIm) as a function of dilution level during the second F100 test; (b) model predicted effects of dilution levels on sulfate mass fraction in the condensed phase (note that the sampling line wall temperature is determined by the ambient temperature specified above each bar)

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Figure 5

Measured (a) black carbon soot, (b) sulfate (SO4), and (c) organic mass emission index (EIm) versus normalized fuel flow when dilution gas was applied at the probe tip and the rake base (130 cm downstream from the tip) during the second F100 test

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Figure 6

Model predicted effects of dilution locations and engine power settings on sulfate mass fraction in the condensed phase

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Figure 7

Model predicted effects of diluent relative humidity on sulfate mass fraction in soot mode and nucleation mode for engine power settings of (a) 100% and (b) 7%

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Figure 8

Model predicted effects of water cooling and engine power settings on sulfate mass fraction in the condensed phase

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Figure 9

Measured (a) black carbon soot, (b) sulfate (SO4), and (c) organic mass emission index (EIm) versus normalized fuel flow for heated and unheated sampling lines during the first F100 test

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Figure 10

Model predicted effects of sampling line temperature and engine power settings on sulfate mass fraction in the condensed phase (note that available soot surface area is greater in higher power settings, resulting in greater amount of sulfate condensed on soot)

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Figure 11

(a) Predicted particle penetration using the differential equations derived in this work and the algebraic equations in literature versus the prediction from the calibration curve used in APEX-1, (b) predicted particle size distributions with or without particle loss mechanisms, and (c) predicted effects of particle line loss on sulfate mass fraction in the condensed phase

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