Laser-Induced Incandescence Sensor for Soot Particle Size and Concentration

An instrument will be developed to measure the mass concentration and primary particle size of non-volatile particulate (nvPM) emissions from aircraft as they are injected into an altitude chamber for contrail formation studies at NASA’s PAL or similar facilities. Contrails are the main contributors of aircraft to climate change and research is needed to better understand, for example, the tendencies of various types of aviation fuel to form contrails. The technique uses a 10-ns laser pulse to heat the soot sample in situ, without the need for extractive sampling, while a detector measures the resulting incandescence signal containing information on the particle properties. Experimental studies conducted in the Phase I effort showed that an optimized laser-induced incandescence (LII) breadboard is able to achieve a detection limit of better than 0.1 micrograms per cubic meter, corresponding to an inferred nvPM number concentration of 1000 per cubic cm, at a standoff distance of 12 inches, meeting the requirements of the PAL facility. The Phase I work also showed through model predictions that the time-resolved LII technique can measure primary particle size with excellent sensitivity over the range of 5 to 100 nm at conditions corresponding to the altitudes of commercial aviation. The Phase II effort will include development of the prototype hardware, its operating software, methods to calibrate it for particle sizing and aerosol mass concentration, and a demonstration of the system in a relevant environment. A capability to synthesize soot particles of selectable size will be developed for accurate size calibrations through a collaboration with Pennsylvania State University. Potential customers include aircraft engine manufacturers, commercial airlines, industrial processing plants (i.e., stack monitors), and manufacturers of automobiles and trucks.