Transport and reignition of n-Dodecane fuel droplets in a transverse jet in supersonic crossflow

The multiphase jet in a cross flow (JICF) problem is relevant to divert attitude control systems (DACS) and scramjet engines. This work presents results from detailed numerical Euler-Lagrange1 simulations of a 3D JICF configuration, where the jet is a mixture of burnt products and monodisperse 20μm n-Dodecane liquid fuel droplets, injected into a Mach 1.6 pure gaseous oxygen cross flow. The jet conditions are representative of a partially burnt exhaust from an engine/thruster. We investigate droplet breakup and burning characteristics, as well as the possibility of reignition of trapped, unburnt fuel droplets. As the high-pressure jet enters the cross flow, the droplets reach a local Weber number of ~300 triggering breakup. Our simulations show that droplets rapidly break up into child droplets with diameters below the critical Weber number for further breakup. The droplets continue to evaporate due to the surrounding hot carrier gas, resulting in reactions and burning. Reignition of unburnt fuel droplets in these extreme flow conditions can damage the external surface of vehicles employing DACS, or alter the forces expected by the control systems, and are thus an active area of interest.    

        

1. B. J. Musick et al., Combust. Flame, Suppl.  257, 113035 (2023).