A phenomenological model for predicting the size of soot primary particles emitted from an aero-engine combustor

Soot particles emitted from aero-engines are harmful to airport local air quality, and the adverse impact from soot particles is closely related to particle morphology, microstructure and chemical properties. To understand those properties of aviation soot particles, combustion experiments using conventional aviation fuel RP-3 were conducted on a Rich-Burn/Quick-Quench/Lean-Burn (RQL) aero-engine combustor. The soot emissions from the RQL combustor were analyzed via a high resolution transmission electron microscope (HRTEM), and the size distributions of primary particles at different power levels were determined based on the HRTEM images. Since the primary particle size is strongly related to the power level and follows an S-shaped curve, a phenomenological model with low-computational complexity and general applicability was established. Furthermore, the model was validated by using previously published experimental data of a CFM56-2C1 aero-engine burning four different fuels, including sustainable aviation fuels (SAF), demonstrating the influence of fuel properties on primary particle sizes at different power levels. Novelty and Significance Statement: In this paper, combustion experiments were conducted on an RQL combustor burning RP-3 fuel. Based on the HRTEM observation, the log-normal size distributions of primary particles at different power levels were determined. Furthermore, based on the fact that the relationship between primary particle size and power level followed an S-shaped curve, a phenomenological model linking primary particle size and combustor power was proposed and validated.