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Comparison of a Direct-Connect and Freejet Dual-Mode Scramjet

2015; American Institute of Aeronautics and Astronautics; Volume: 31; Issue: 5 Linguagem: Inglês

10.2514/1.b35221

1533-3876

Thomas B. Steva, Christopher P. Goyne, Robert D. Rockwell, Daniel Cresci, Jonathan W. Osborne,

Gas Dynamics and Kinetic Theory

Testing of identical dual-mode scramjet flowpath geometries in the freejet and direct-connect configurations was conducted in two separate facilities. These tests enabled a comparison study between the two configurations, which was directed toward the determination of the effects of inlet distortion and backpressure on the performance and operability of a dual-mode scramjet. Bulk flow conditions were matched between the two facilities at the isolator entrance plane to simulate Mach 4.8 flight, and a series of metrics were established to quantify similarities and differences. The effects of flowpath backpressure in the direct-connect case were seen to be isolated to regions close to the exhaust. An approximate 10% decrease in combustor pressure rise and consequently integrated pressure force were observed in the freejet configuration; shock train length, however, remained the same. Mode transition was delayed from an equivalence ratio of in the direct-connect case to in the freejet configuration. Further, ignition difficulties were experienced in the freejet tests which were not encountered in those of direct-connect tests, limiting the scope of comparable test points. This work represents the first attempt at a quantitative comparison in the literature of an identical direct-connect and freejet dual-mode scramjet.