Abstract
The paper numerically and experimentally examines a method to reduce combustion length within a Mach 12, shape-transitioning scramjet. As the examined airframe-integrated engine transitions from a rectangular inlet to an elliptical throat, highly three-dimensional flow is delivered to the combustor. Tailored to this nonuniform flowfield, hydrogen fuel is injected at both inlet- and combustor-based stations. The current work shortens the engine combustor and removes a legacy rear-facing step. Computational fluid dynamics guides the length by which the combustor may be reduced while still ensuring sufficient combustion. Experimental validation under shock-tunnel conditions follows. Static pressure and heat transfer measurements throughout the flowpath examined combustion at on-design conditions. Comparisons are made to unfueled and suppressed combustion cases, and efficient combustion is attained with combined inlet- and combustor-based fueling within a combustor reduced in length by 68%. Inlet-only fueling displays similar ignition characteristics to the combined-fueling cases, whereas combustor-only fueling displays marginal pressure and heat transfer increases from suppressed-combustion cases. Measured pressure on the engine nozzle displays greater increases under combined fueling than that which would be obtained through the direct summation of the constituent inlet-only and combustor-only fueled cases, indicating inlet-injected fuel pilots combustion of combustor-injected fuel.
Published Version
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