The primary NASA need for this technology is to measure soot particle mass distribution from aircraft engine exhaust. At present, particle mass distribution is calculated from particle size distribution, which is measured by the Engine Exhaust Particle Sizer (EEPS) and Scanning Mobility particle Sizer (SMPS) techniques. Both techniques provide information on particle count at each electrical mobility diameter. To calculate particle mass distribution, an assumption of particle density becomes necessary. Since engine soot particles are intrinsically fractal aggregates, their densities are complex function of particle size and compositions. Obtaining the particle density information requires sophisticated measurement instrumentation. The proposed soot mass distribution monitor will directly measure particle mass distribution, from which total particle count and mass could be determined. In the past, NASA has funded a number of field measurement programs such as EXCAVATE, APEX, UNA-UNA, and AAFEX that focus on the measurement of black carbon emissions from civilian aircraft engines.
We expect that the soot particle mass monitor developed under this program will significantly benefit the scientific community interested in characterizing soot particle mass from a variety of internal combustion engines. The ability of one instrument to measure particle charge at specific mass will enable continuous measurements of particle mass distribution that can be directly used to determine total particle count and mass. In combination with an electrical aerosol charger, either with a radioactive source like 85Kr or non-radioactive source like corona discharge, this instrument will provide a direct measurement on particle count and mass simultaneously for any particles or aerosols. This measurement technique could be applied to ambient aerosol monitoring, PM emission detection, and particle manufacture process.