Numerical Modeling of Jet Fuel Ignition and Ensuing Combustion using a Superheated Ignition Assistant

Energy-assisted ignition of liquid fuel sprays using superheated ignition assistant (IA) devices is a promising option for achieving consistently repeatable ignition of low-cetane-number jet fuels in airborne compression ignition engines operating at high altitudes. However, the repeated injection and combustion events occurring during the IA lifetime can lead to thermal fatigue and surface erosion of the IA. Designing an efficient and durable IA requires a detailed understanding of the complex physics of spray-wall interaction, fuel-air mixture ignition mechanism, and ensuing combustion process. Therefore, the objective of this study is to develop a comprehensive numerical framework to characterize the ignition processes of F-24 jet fuel resulting from the interaction between the fuel spray and the IA, in a rapid compression machine (RCM). A new data-driven skeletal chemical kinetic mechanism developed by the authors was used to model the ignition and combustion processes accurately. Additionally, a new phenomenological thermal spray-wall interaction (PT-SWI) model previously proposed by the authors was used to model the effects of film-boiling-induced heat transfer, atomization, and dispersion of fuel spray droplets impinging on the superheated IA surface. In this work, the authors combined the PT-SWI model and the skeletal chemistry mechanism to assess the accuracy of this modeling framework in predicting the different ignition modes and ensuing flame structures. Validation was performed against RCM optical experimental data for different IA surface temperatures and insertion depths.