SOLID-FUEL RAMJET FUEL REGRESSION RATE THRUST MODULATION

An experimental investigation was conducted to determine if inlet air swirl and/or secondary gaseous injection could be used effectively for fuel regression rate control or thrust modulation in a solid-fuel ramjet. Inlet swirl characteristics were measured in nonreacting flows. Tests were conducted at high and low air mass fluxes using three fuel compositions with equivalence ratios between 0.5 and 1.8. Swirl introduced downstream of the air inlet was found to be effective for obtaining limited increases in the fuel regression rate, but the magnitude was highly dependent upon motor geometry. Swirl interactions with the reattaching inlet flow and/or significantly increased near-wall mixing were found to be detrimental to efficient combustion. Energetic gaseous fuels (H-2, C2H4) can be easily injected and efficiently burned under fuel-lean conditions to significantly enhance thrust.