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Diagnostics for Hypersonic Engine Isolator Study Complex Fluid Dynamics •Presently, no comprehensive under-standing of the details of the fluid behavior in isolators of hypersonic engines (in particular, transient behavior). •Transient CFD approaches not yet mature enough for predictive capability. •DNS currently limited to Reynolds numbers well-below those of isolator operation. Need for Measurements •Measurements of thermodynamic variables during isolator transients needed for: input to (CFD) modeling efforts input to reduced order control models •Currently only a few data sets of transient phenomena in hypersonic isolators with fueled combustors exist. Tandem Measurement Strategy •Simultaneously implement optical diagnostics for in-stream measurements and “surfacemounted” diagnostics. MAIN ACHIEVEMENTS: •Optical measurements have been executed in the boundary layer of supersonic flows upstream of: a laser spark, a pulse combustion device and a scramjet combustor transient. (Belowshadowgraph of pulse detonation event and corresponding transient optical signal (graph)) M 2 flow Planned Approach Perform simultaneous optical and nonoptical diagnostic measurements in isolators of varying design under varying flow conditions; in particular, transient conditions (along with their corresponding tare conditions). Perform measurements at data acquisition rates of 1 kHz and higher. Analyze acquired data to search for variables or correlations thereof that indicate impending fluid behavior changes such as shock-induced boundary-layer separation Research Goals END-OF-PHASE GOAL CURRENT APPROACH Implementation of Diagnostics in Isolators of Fueled Engines MEASUREMENT STRATEGY STATUS QUO Michael S. Brown / Jeffrey M. Donbar (FA8650-08-D) AFRL/Aerospace Propulsion Division Identification of measureable variable(s) whose time-dependent behavior predicts the onset of gross changes in isolator fluid dynamic behavior Collection of data sets of transient isolator phenomena suitable for CFD study 1 Highlight Slide Template Boundary Layer Dynamics Reveal Downstream Behavior Your Pic Shock associated with cavity flameholder disturbs upstream boundary layer Diode laser beams M 2 flow expansion fan isolator M 2 flow combustor oblique shock shear layer Density fluctuations in boundary layer are sensitive to the downstream behavior of supersonic flow Unlit combustor exhibits simple expansion fan at step Dr. Michael Brown Lit combustor leads to shear layer and shock wave that JANNAF influences the upstream Combustion boundary layer Laser beam in boundary layer gets “steered” by fluctuations isolator Impacts scramjet engine control Subcommittee for Diagnostics (organizer) • Associate Fellow, AIAA 2 Transmitted Light Amplitude Keep this space blank, too, same deal as last slide combustion no combustion Time(s) Boundary layer dynamics lead to diffraction of laser beams causing amplitude fluctuations of transmitted light These dynamics change ahead of full combustion as evidenced by the frequency-weighted power spectrum of the transition period (middle spectrum below) Brown & Donbar, AFRL 3