Fundamental Studies of Cavity-Based Flameholder Concepts for Supersonic Combustors

TLDR

The study experimentally and computationally investigates cavity‑based flameholder concepts in nonreacting supersonic flows. All cavities were open type with L/D < 10, and the investigation varied L/D, offset ratio, and aft ramp angle to assess their influence on the shear layer. Results indicate that the aft ramp angle strongly governs the shear layer, with a 90° ramp producing a compression wave and strong unsteady recompression, while shallower ramps reduce pressure drop, delay recompression, and result in higher drag coefficients and shorter residence times.

Abstract

Experimentalandcomputationalinvestigationsofthee owe eldassociatedwithseveralcavity-basede ameholders in a nonreacting supersonic e ow are described. All cavity e ows were of the open type, that is, length-to-depth ratio L/D<10. Two values of L/D were studied with several offset ratios (OR) and aft ramp angles µ. Results indicate that the aft ramp angle plays an important role in determining the character of the shear layer that spans the cavity. For a rectangular cavity with OR=1 and µ=90 deg, a compression wave forms as the e ow separates from the cavity’ s upstream corner. A strong recompression occurs at the aft wall, and the e ow is visibly unsteady. The pressure on the cavity fore wall decreases steadily and the recompression process occurs more gradually with decreasing aftrampangle.Higherdrag coefe cientsandshorterresidencetimesarefoundin cavitieswithshallower ramp angles.