Comparison of Mach 10 Scramjet Measurements from Different Impulse Facilities

A comparison is made between scramjet pressure data taken in two different impulse facilities, a reflected shock tunnel and an expansion tunnel, to provide verification of flow similarity. A two-dimensional hydrogen-fueled scramjet was tested in both facilities at a Mach 10, 66 kPa dynamic pressure, flight-replication condition. The entire flowfield was reproduced, including the inlet, combustor, and thrust nozzle. The expansion-tunnel model was a 40%- scaled model of that investigated in the shock tunnel, as the generated core flow was smaller. Applying density-length scaling, the density of the freestream was increased by a factor of 2.5 in the expansion tube to maintain similarity between the experimental setups. Results show agreement within the experimental uncertainty between the two data sets at similar fuel equivalence ratios, indicating the repeatability of scramjet pressure measurements, independent of the experimental facility used. It is further demonstrated that density-length scaling is appropriate for the flows generated in the investigated scramjet engines. Verification is also provided of the analysis technique used to process experimental scramjet data sets that involve transient inflow conditions