Ignition of supercritical hydrothermal flames in co-flow jets

Abstract

Supercritical hydrothermal combustion is a new high-pressure combustion technology. Stable ignition of hydrothermal flames is one of the most important issues. To obtain the ignition criterion, the hydrothermal flame in continuous co-flow jets with methanol as auxiliary fuel was investigated in this study. The autoignition model for laminar fuel jets based on the Frank-Kamenetskii theory was modified by considering the jet’s actual specific heat. Piecewise relations between the ignition boundary and jet radius were obtained. Moreover, the eddy dissipation concept simulation for a turbulent fuel jet in the coaxial nozzle indicated the important influence of interfacial reaction in the jet initial region on the ignition of hydrothermal flames. Finally, the analysis and comparison of the two models demonstrated that the autoignition model is suitable to evaluate the ignition of turbulent jets when hydrothermal flames are ignited in the initial region of jet, and provides a judgement scheme.