Characterization of Expansion Tube Flows for Hypervelocity Combustion Studies

Abstract

An expansion tube with an 89 mm inner diameter and a 12 m length was characterized for basic studies of the near-eld mixing and ame-holding characteristics of gaseous fuels injected in high-stagnation-enthalpy supersonic ows. The expansion tube provides a wide range of freestream conditions with little perturbation of test gas chemical composition. The latter is critical for supersonic-combustion studies in the high-stagnationenthalpy ows associated with hypersonic airbreathing propulsion systems. Efforts focused on achieving three operating points, simulating ight Mach 8, 10, and 12 stagnation-enthalpyconditions at the entrance of a supersonic combustor. The ability of the expansion tube to provide a steady-ow test time of adequate duration and a core ow of suf cient size for 2-mm jet-in-cross ow studies was veri ed. A core-ow size of 25 mm could be achieved in 6.2 MJ/kg stagnation-enthalpy ows with 400 ¹s of steady test time ( ight Mach 12 simulation). The primary effects of the boundary layer on the expansion tube ow were to extend the useful test time (in contrast with conventional shock-tube performance) and to decrease the core-ow size. NomenclatureDa = Damköhler number J = jet to freestream momentum ux ratio, (°pM 2 / j =.°pM 2 / 1 L = characteristic length L 1 = characteristic distance from edge of the injection plate L 2 = characteristic recirculation region length M = Mach number M s = shock Mach number M w = molecular weight p = static pressure q = dynamic pressure Re = Reynolds number T = static temperature t = time U = velocity x = distance°= speci c heat ratio°c = average speci c heat ratio, 1 2 .°0 C°3/ c = compression ef ciency through a hypersonic vehicle diffuser µ = characteristic temperature for the ignition delay time º i = gas composition ½ = density ¿ c = chemical time ¿ i = ignition delay time Subscripts j , jet = jet properties at the injection exit 0 = atmosphere conditions 1 = driven section conditions

Survey of high-enthalpy shock facilities in the perspective of radiation and chemical kinetics investigations

“…The expansion section is equipped with sapphire viewing ports for optical measurements. In addition, for flow characterization tests, a Pitot rake consisting of four pressure transducers across the diameter of the tube is positioned at the test section" (from [103]). …”

“…26, with the optical diagnostic devices, including lasers and optical arrangement for planar laser-induced fluorescence imaging [104,105], tunable DLAS [106], and a megahertz framing-rate intensified digital camera for Schlieren imaging. The instrumentation and available diagnostics have been detailed in [103]. A square test section of 27 Â 27 cm 2 cross section is mounted at the exit of the expansion tube.…”

“…This ground test [102,103] is 12 m in length (including driver, driven, and expansion sections and dump tank) with an inner diameter of 89 mm. The driver section is filled with highpressure helium gas and is separated by a double-diaphragm from the lower pressure driven section, which is filled with the desired test gas.…”

Development and testing of the ACT-1 experimental facility for hypersonic combustion research

“…Such short durations do not allow the investigation of the combustion stabilization process and other important phenomena including inlet unstart, that typically require at least tens of milliseconds for being fullydeveloped or reach steady-state. Nevertheless, impulsive facilities have become an important tool for testing of novel measurement and visualization techniques, and much fundamental knowledge regarding supersonic ignition phenomena have been gained in the process [10].…”

On the numerical technique for the simulation of hypervelocity test flows

“…A shock-expansion tube (SET) has the potential to mitigate the aforementioned concerns to a certain extent and generate relatively clean test gas of very high enthalpy and hypervelocity because the test flow is not stagnated anywhere. A series of SETs have been set up around the world, e.g., X-2 and X-3 at the Queensland University [1][2][3][4], HYPULSE at GASL [5], LENS-X at CUBRC [6], JX-1 in Japan [7,8], a SET of low-speed range for the investigation of scramjet at Stanford University [9][10][11], and others [12]. A detonation-driven SET has been built at the State Key Laboratory of High Gas Dynamics (LHD) and has successfully generated hypervelocity test flows of up to 8 km/s and beyond [13,14].…”