A Direct Numerical Simulation Study for Flame Structure and Propagation Characteristics of Multi-Jet Flames

Abstract

Lifted multi-jet flames of hydrogen and steam-diluted oxygen are studied using direct numerical simulations (DNS). The DNSs have been carried out for laminar and turbulent flame configurations. The simulation data are analyzed to investigate the flame and flame-base structures and the flame-base propagation in a configuration akin to a gas turbine with multiple fuel jets. The laminar flames have a tribrachial structure, although lean premixed and diffusi on flame branches collide downstream owing to preferential diffusion. The turbulent multi-jet flames have a single connected base region, whereas the laminar flames have separate bases, each of which is associated with the corresponding fuel jet. Although turbulent multi-jet flames have substantially different flame-base characteristics from laminar multi-jet flames (and conventional single-jet lifted flames), the propagation speed is similar for both conditions. The results suggest that the well-known flame-base stabilization theory can be straightforwardly applied to the multi-jet configuration, despite the turbulent flame structure's unconventional features.