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.

The proposed work directly addresses an objective called out in NASA’s ARMD 2023 Strategic Implementation Plan: that of achieving cleaner, faster, and safer air travel in ways that minimize adverse impacts on the environment. The instrument to be developed would help the country to meet its goal of achieving net-zero aviation carbon emissions by 2050 by providing critical measurements of engine particulates in their natural state that are needed to identify optimal sustainable aviation fuels (SAFs). SAFs don’t release new CO2 into the environment and therefore they are considered essential to meeting this goal. An optimal SAF would produce minimal contrails, which can trap heat in the Earth’s atmosphere. NASA works toward achieving optimal SAFs by a combination of computational modeling, emissions and combustion laboratory testing, and flight testing. The proposed advanced diagnostic is needed to improve our understanding of the soot formation process and to help characterize new fuel formulations for their propensities to form soot. The proposed instrument would have a significant advantage over extractive devices on the market today, potentially replacing condensation nuclei counters and centrifugal mass analyzers in many applications. Present markets that will be targeted include aircraft engine manufacturers, commercial airlines, industrial processing plants (i.e., stack monitors), commercial trucks, and automobiles.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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