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Gas Turbine Engine Particle Emission Characterization


OBJECTIVE: Develop a capability for fast measurements of gas turbine engine particle mass and number emission indices. DESCRIPTION: The goal is to develop a fast, accurate capability for measurements of particle number density, size distribution and mass-based emission factors (indices) as an alternate to EPA Method 5 currently used by DoD for reporting turbine particulate matter (PM) emission rates. The DoD-JSF Environmental office, EPA, FAA and NASA have expressed this need to the SAE E31 Committee. Air bases, many in non-attainment areas, remain non-exempt from local air quality PM Regulations as upheld in courts, March 2002 [1]. Method 5 does not provide PM size (critical for health effect issues) and is costly, requiring long engine run times. Aircraft-generated PM is composed of nonvolatile particles (soot) and volatile particles, including volatile condensed onto nonvolatile. PM techniques used in research for determining particle size, number, and mass require fundamental research before EPA and FAA will accept the viability of these PM techniques and associated sampling methodologies for regulatory compliance. Current acceptable measurement practices do not provide real-time data [2]. Differential mobility analyzers and CNCs are used to measure number densities and size distributions [3]. Assumptions for particle shape factors and mass density, used to convert these measurements to mass-based emission indices, add a large uncertainty to the mass based emission indices thus determined. Fundamental research is required to experimentally determine these shape factors and particle mass densities as a function of combustion aerosol size for aircraft engine emissions to thus define and possibly eliminate these uncertainties. Measurements in the laboratory and on a variety of engines are required to establish correlations for shape factor and mass density to engine type and engine operating conditions. Ultimately, a fast technique (~1 Hz per 10-1000 nm dia. scan) is required for measuring accurate number densities, size distributions and mass based emission factors as a function of engine type and operating condition for engines in a variety of test environments to provide a sound, accurate basis for DOD to report PM emission rates to the regulatory authorities. PHASE I: Demonstrate the feasibility of resolving measurement system particle density and particle shape factor effects. PHASE II: Develop a prototype measurement system for fast particle emission indices in gas turbine engine exhausts. PHASE III: Military applications include environmental reporting of military aircraft, potential quantitative replacement of smoke number, and fast diagnostic for plume observables. REFERENCES: 1. Office of Air Quality Planning & Standards,"Draft Staff Paper for Particulate Matter Fact Sheet,"Environmental Protection Agency, Washington DC, August 2003. 2. SAE E31 Committee,"Nonvolatile Exhaust Particle Measurement Techniques,"SAE E31 AIR5892 Committee Aerospace Information Report. 3. SAE E31 Committee,"Nonvolatile Exhaust Particle Measurement Techniques,"SAE E31 AIR6037 Committee Aerospace Information Report. 4. Schmid, Otmar, Hagen, Donald, Whitefield, Philip, Trueblood, Max, Rutter, Andrew, and Lilenfeld, H.,"Methodology for Particle Characterization in the Exhaust Flows of Gas Turbine Engines,"Aerosol Science & Technology Volume 38, Number 11 / November 2004, pages 1108 1122.
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