Performance Impacts of Preheating the Primary Fuel Jet of an Ejector Ramjet

A major challenge of ramjet engines is their inability to produce appreciable thrust at subsonic speeds. The Atlantis Intake System (AIS) is a novel design for a ramjet inlet intended to produce thrust through a wide range of flight Mach numbers, including under static conditions. With the AIS, the ramjet operates as an ejector ramjet, using a supersonic hydrocarbon fuel jet to pressurize and entrain ambient air. A computational fluid dynamics study is performed to assess the change in performance of the AIS due to preheating the fuel jet using heat released from combustion. First, the computational model is assessed for two combustion-related problems relevant to an ejector ramjet: a three-dimensional bluff-body stabilized flame and a ramjet with the AIS operating under static conditions. The partially stirred reactor model is used for modeling turbulent combustion, and it is shown that using a modified mixing timescale with this model improves the accuracy of the computational results compared to the experiment. For an ejector ramjet, preheating the fuel jet is shown to increase the ratio of air to fuel entrained by the AIS and the specific impulse ([Formula: see text]).