Abstract:

The internal drag of cavities in tandem is investigated in a constant area scramjet engine on a direct-connected test stand. Cavities with depths of 10, 15 and 20 mm, and length to depth ratios of 5 and 7 are adopted to investigate the effect on its drag of different combinations, sequences, distances and numbers of cavities with different fuel injection schemes and equivalence ratios. Results reveal that, for a known fuel injection scheme the more cavities are installed in tandem, the higher is the internal drag; combination of cavities with higher drags leads to higher total drag; fuel injection scheme and equivalence ratio have great impact on combustor drag; with low equivalence hydrogen combustion will increase the internal drag; the drag of hydrogen combustion is higher than kerosene combustion with equal equivalence ratio. For certain suitable fuel injection schemes, multi-cavities may also produce a positive force.

Key words: multi-cavity combustor, scramjet, cavity flame holder, drag