Book Description

"Energy deposition in front of dual-mode ram/scramjet engines is numerically investigated utilizing two-dimensional CFD for its potential to modify inlet/isolator flow-fields for engine start/unstart control and for its general potential for generating large-scale flow-field modification in such flows. A simplified (high Mach number) constant-area duct geometry is initially defined in order to test the feasibility of the concept; the results from this initial investigation demonstrates possible beneficial effects of depositing energy upstream of a thermally choked duct in terms of causing massive changes in flow patterns, including the reestablishment of supersonic flow throughout the duct. This study is followed by the definition of a realistic high-speed engine domain focusing on the lower external and internal engine side of a hypersonic vehicle. A quasi-one-dimensional solver is constructed and used to establish approximate understanding of thermal choking limits in the defined geometry. A CFD investigation of this actual engine geometry is performed in which heating blocks are used to simulate fuel-air combustion in the engine combustor. Actual choking limits are established and a base-line case defined with substantial (choked flow) upstream interaction. A range of energy deposition cases are then run in order to assess the use of upstream energy deposition for facilititating restarting an unstarted engine, mitigating unstart, and generating large-scale flow-field modification in the isolator/inlet of a dual-mode ram/scramjet engine. Results indicate that, although the ability to actually increase performance of an unstarted engine through the use of upstream energy deposition is minimal, there is indication that the use of such a technique for generating a "virtual cowl" and/or a "virtual" isolator (including throats, etc.) is possible"--Abstract, leaf iii