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polarized light scattering measurements for sizing diesel particulates

OBJECTIVES. Develop a method to characterize diesel exhaust soot from polarized light scatteringDevelop a real-time light scattering instrument to measure diesel particulate size Study the effect on particulate characteristics ofRunning conditionsFuel compositionPost-combustion factors (humidity, dilution, etc.).

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polarized light scattering measurements for sizing diesel particulates

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    1. POLARIZED LIGHT SCATTERING MEASUREMENTS FOR SIZING DIESEL PARTICULATES A.J. Hunt, I.G. Shepherd, M.S. Quinby-Hunt Lawrence Berkeley National Laboratory Petroleum Environmental Research Forum Berkeley, CA March 10, 1999

    3. RELEVANCE TO DOE-OTT CIDI OBJECTIVES PM emissions are technical barriers to all but one CIDI R&D task Accurate real time measurements of PM are essential for engine development and monitoring evaluation of aftertreatment technologies Emissions Compliance Current measurement methods are inadequate (e.g., smoke meter, filter methods, impactors

    4. RELEVANCE TO DIESEL DEVELOPMENT, TESTING, AND USE Accurate real time measurements of PM are essential for engine development and monitoring evaluation of aftertreatment technologies Emissions Compliance Current measurement methods are inadequate (e.g., smoke meter, filter methods, impactors) or slow (e.g. mobility analyzers)

    5. APPROACH A existing light scattering instrument used to measure diesel exhaust streams in situ : angle-dependent scattering intensity angle-dependent polarization transformations determine size distribution and optical properties (n, k) (refractive and absorptive) properties of soot by comparing experimental data with modeled scattering Model soot scattering as: spheres - Mie scattering theory to fit data agglomerates -represent clusters as coupled dipoles

    6. Polarized Light Scattering

    8. PROJECT ACCOMPLISHMENTS

    9. Scattering Results for Two EnginesCummins B5.9 175 MAN turbo-diesel and Acme Motori - ADX 300

    10. Time Response(Acme Motori - ADX 300 Diesel)

    11. INTERPRETING SCATTERING DATA Mie scattering theory - spherical particles Calculates angle dependent polarized scattering given size and optical properties of particles Levenburg-Marquardt optimization Matches observed scattering with Mie calculations varying: Log normal, Gaussian, power law distributions Real and imaginary indices of refraction Fits four matrix elements simultaneously Determines particle size distribution and their complex refractive index (composition)

    12. Comparison: Mie Theory & Experiment(Small Diesel)

    13. Particle Size Distribution from Mie FittingAcme Motori -ADX 300

    14. Number and Mass based Size Distributions, Cummins Diesel

    15. Effects of Oxygenated FuelPreliminary Results

    16. DIESEL PARTICLE SCATTEROMETER(DPS) Three simultaneous matrix elements sufficient 0f, 1f, & 2f with single detection polarization Laser Wavelength (450 - 900 nm) Detector system design Number - 12 Type - compact programmable photomultiplier Placement - 20o intervals Multiplexed into 16 bit A/D converter Software implementation of lock-in detection Time response (1 -10 Hz)

    17. DPS DESIGN

    18. Fractal-Like Soot Particle(if S22 1 use correction or coupled dipole calculation)

    19. MODELING OF DIESEL SOOT PARTICLES AND SCATTERING Particle generated by random walk procedure Size (characterized by radius of gyration) is specified by number of primary soot particles Fractal dimension calculated (compactness) Coupled dipole calculation in parallel on Cray T3E (using up to 512 processors) Sizing by Levenburg-Marquardt optimization technique using look-up tables

    20. COLLABORATIONS Joint development project with ORNL (Engineering Technology Division) Combined measurement program with UCB Engine Laboratory (Prof. Dibble) Software development with Prof. Patricia Hull of Tennessee state University Working with researchers in the environmental program at LBNL on diesel particulate characterization

    21. Future Plans Complete calibration of 2 scatterometers for particle size measurements at 1-10 Hz rates (ORNL & LBNL) Compare scatterometer results with Scanning Mobility Particle Sizer and Electrical Aerosol Analyzer (>50nm) Characterize exhaust from several fuels in OAAT fuel matrix Explore shorter wavelengths for enhanced sensitivity Continue coupled-dipole modeling for sizing non-spherical diesel particles with the scatterometer Evaluate commercial potential of scatterometer

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