Experimental Investigations of the Hypersonic Stream-Traced Performance Inlet at Subdesign Mach Number

Abstract

Stream-traced inlets offer superior compression efficiency for scramjet engines and are strong prospects for practical application. However, only limited experimental information is available on the subdesign performance of these inlets. In this study, the operation of a stream-traced truncated-Busemann inlet with a design point of Mach 5.5 and a physical contraction ratio of [Formula: see text] is experimentally investigated in a Mach 4.0 flow. Several nonintrusive flow measurement techniques are employed to provide a thorough understanding of the intricate flowfield within these inlets at various operation conditions. The measurements include surface pressure, mean streak-line patterns, off-body velocity fields, and qualitative gas density fields. Together, these datasets provided a unique understanding of the flow evolution and load distribution within the inlet and isolator with and without application of an external backpressure. The facility effects on the inlet operation are also explored. Without appropriate boundary-layer conditioning, the wind-tunnel starting shock could not be swallowed by the inlet; this is termed a “failed start” operation. During the failed start operation the inlet flowfield and surface pressure field, even without external backpressure, exhibited strong similarities with an unstarted inlet. The failed start operation enabled a unique lens to the flowfield in the unstarted inlet throat that could not be otherwise obtained due to optical constraints.