A Study of the Thermo-Structural Behavior of Boundary Layer Splitter for a Scramjet Module

ABSTRACT

Scramjet engine generally operates at high Mach numbers ranging from 5 to 10. Typically, it consists of a boundary layer splitter (BLS), followed by ramps, combustion chamber and nozzle exit. BLS diverts away high-energy fluid towards ramps. During hypersonic flight at dense atmosphere BLS experiences severe aerodynamic and aerothermal loads in addition to centrifugal loads varying with vehicle spin rate. A study on the thermo-structural behavior of BLS made of Inconel and attached to carrier vehicle using four fasteners was carried out. Aerodynamic heating rates corresponding to severe heating trajectory at different regions of BLS are evaluated using engineering methods. Heat flux estimates for a typical flight condition is validated using CFD. Thermal simulation tests have been carried out using plasma arc jet to evaluate thermal integrity of BLS. Tests show the capability of BLS to withstand severe flight thermal loads. Post-test analysis was carried out for simulated test conditions, which shows fairly good agreement between predicted and measured temperature histories.

Three-dimensional finite element model of BLS is generated and thermal response analysis carried out for entire flight duration. Further three-dimensional thermo-structural integrity of BLS is studied at critical time instants considering temperature dependent material properties. Margin of safety available on BLS is assessed for entire flight duration and effects of thermal relief at the fastener locations were examined. Analysis shows the adequacy of BLS design in maintaining its thermo-structural integrity under flight conditions.

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