NSF Award
2414401
Soot emissions from combustion devices and fires have been plaguing humans for centuries, with repercussions on health and climate. Understanding the process by which soot forms remains a challenging topic in combustion research because of difficulties in describing the critical steps involved. The most sophisticated approaches to study soot formation in flames entail detailed measurements of gaseous soot precursors and soot particles with multiple, complementary diagnostics that follow the entire evolution from parent fuel molecule. At the other end of the diagnostic spectrum, the sooting tendency is described by a simple sooting index, without the assessment of soot production rates necessary for modeling soot in engine-relevant conditions. This proposal seeks a middle ground, aiming to quantify the soot production rate while maintaining the simplicity of single index characterizations. The study will impact the design of practical engines, the reduction of the environmental footprint of combustion, and, indirectly, air quality, public health, and climate.<br/><br/>The research goal is to quantify soot production rates of several relevant fuels in a simple but fundamental manner, without ad hoc assumptions. The approach involves establishing opposed jet gaseous diffusion flames, doping them with a few thousand parts per million of pre-vaporized practical fuel components and measuring soot volume fraction through pyrometry. The experimental work is complemented by numerical simulation of the flames structure to accurately describe the velocity and temperature fields. These data enable the quantification of the soot production rate from the soot governing equation. In this study, fuels to be tested are common components of Jet fuels and Diesel fuels, and their surrogates, including: iso-octane, n-decane, n-hexadecane, iso-cetane, toluene, 1,2,4 tri-methylbenzene, methyl-naphthalene and decalin. They will be tested individually at first and then in blends mimicking the sooting tendency of jet fuel and Diesel fuel. The developed database will allow a quantitative comparisons of different fuels in highly controlled environments either by keeping a constant temperature-time history, which affects soot formation critically, or by varying peak temperature over several hundred degrees and pressure in the 0.1-3.0 MPa range. The quantified soot production rates will be converted to sooting yields and their explicit dependence on temperature, pressure, strain rate, and local mixture fraction will be established.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
