Supercritical flow dynamics and mixing of transverse jets*

The present study investigates the flow dynamics of a dodecane jet in crossflow at supercritical pressures, conditions typical of advanced combustors, using large-eddy simulation. The effects of various parameters, including pressure, jet-to-crossflow momentum flux ratios (J), and jet nozzle elevation, on the flow structures and stability characteristics are explored in detail. The results show the supercritical flow dynamics differ substantially from their subcritical counterparts. At a given J of 7.1, the jet's upstream shear layer is absolutely unstable at high supercritical pressure but becomes convectively unstable at low supercritical pressure. Such behavior can be attributed to the intensified real-fluid effect at low supercritical pressure, where the inflection of density variation in the mixing layer creates large density gradients to stabilize the shear layer. Elevating the jet nozzle with a stack alters the jet and crossflow mixing efficiency by introducing intricate interactions between jet and stack wake regions. An analysis of spatial mixing deficiencies demonstrates that incorporating an elevation stack with proper thickness and height can dramatically improve the jet-crossflow mixing efficiency.