Expansion Tubes in Australia

Gildfind, David; Morgan, Richard G.; Jacobs, Peter A.

doi:10.1007/978-3-319-23745-9_13

Cited by 62 publications

(52 citation statements)

References 46 publications

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“…1) is a free pistondriven expansion tube that is configured with a freely sliding piston, a shock tube containing the test gas, an acceleration tube, and a nozzle exiting into a test section where the model is mounted. Its operation has been described in detail by Gildfind et al [8], and thus will only be briefly summarized here.…”

Section: Experimental Methodologymentioning

confidence: 99%

See 1 more Smart Citation

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Banerji¹,

Leyland²,

Fahy³

et al. 2018

Journal of Thermophysics and Heat Transfer

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The effects of phenolic decomposition on shock-layer radiation were investigated experimentally in X2 expansion tube for a Venus entry flow. A carbon-phenolic composite aeroshell was subjected to a flow with a flight equivalent velocity of 9.35 km ⋅ s −1 . Emission spectroscopy was used to measure boundary-layer radiation in parts of the ultraviolet (380-480 nm) and visible (620-700 nm) spectrum, and it was compared to control measurements taken with a cold steel model. With the composite model in place, the calibrated spectral radiance measured was seen to increase for the O (645.598 nm) atomic line and the N 2 (391.22 nm) band head, but it decreased for the C 2 Swan band (420-480 nm). The recorded data were then compared to numerical spectra produced by two-dimensional axisymmetric computational fluid dynamic simulations coupled to a radiation solver. Both of the applied chemistry models overpredicted CN violet Δν 0 band radiation, which demonstrated strong self-absorption at these conditions. Better comparisons were achieved for the C 2 Swan band radiation. At visible wavelengths, peak intensities were underestimated by the numerical simulations. Several possible reasons were hypothesized for these discrepancies.

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Section: Experimental Methodologymentioning

confidence: 99%

“…Computational fluid dynamic (CFD) simulations have been used to numerically rebuild several expansion tube experiments [8]. Potter used two-dimensional (2-D) axisymmetric CFD coupled to the inhouse radiation code Photaura to compare shock-layer radiation, simulated around a cylindrical model in a Martian flow, to experiments [9].…”

mentioning

confidence: 99%

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Banerji¹,

Leyland²,

Fahy³

et al. 2018

Journal of Thermophysics and Heat Transfer

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“…This facility is capable of providing representative reentry flow environments for use with subscale test models, with a typical steady flow time ranging from 10 to 100 µs, depending on the condition [90,91]. This study used the same flow condition as Zander et al [25], with facility fill pressures, measured shock speeds, and cone-head pressure (see Gildfind [77]) as shown in Table 5.1.…”

Section: Facility and Test Conditionmentioning

confidence: 99%

Hypervelocity shock layer emission spectroscopy with high temperature ablating models

Lewis¹

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During reentry into the atmosphere, a vehicle can encounter extreme convective and possibly radiative heating loads. Such spacecraft must rely on a carefully designed thermal protection system to maintain the integrity of the underlying structure, thus ensuring the survival of any cargo or crew it may contain. Despite many past developments and research efforts, to this day there remain large uncertainties associated with the prediction of heat shield performance. In particular, accurate modelling of ablation phenomena is critical to minimising uncertainties, reducing excess weight, and increasing safety. This includes thermochemical ablation by oxidation, nitridation, and sublimation, as well as the mechanical removal of material via spallation. Due to the high costs associated with in-flight testing, and the difficulty of mounting precision instruments and advanced diagnostics on flight vehicles, ground-based experiments stand as a cost-effective method for reducing modelling uncertainties.Ablation testing is generally conducted in long-duration facilities such as arc jets, which are well suited to investigating in-depth material response due to their ability to provide representative heating rates for extended periods. They are, however, unable to reproduce a realistic in-flight shock layer due to low Reynolds numbers and, depending on the facility type, a high degree of thermal and chemical nonequilibrium in the free-stream. In contrast, impulse facilities such as shock tubes and their variants are well suited to reproducing realistic flight conditions with free-streams that are a closer match for flows dominated by binary processes in terms of Reynolds number, temperature, and chemical composition. Due to their extremely short test times, however, ranging from the order of 10 µs to several milliseconds, they are unable to aerothermally heat test models up to representative in-flight temperatures, or recreate the quasi-steady heat and mass flux balance of flight. This key limitation of impulse facilities was recently overcome in experiments using the University of Queensland's X2 expansion tunnel by electrically pre-heating samples to temperatures approaching 2500 K immediately prior to a test.In this work, the pre-heating methodology was enhanced to generate maximum surface temperatures approaching 3300 K in order to study sublimation phenomena. It was found that although sublimation-regime temperatures could be achieved, the relevant surface processes themselves were suppressed due to the high pitot pressures of the conditions used. Instead, the nitridation process was studied by observing air shock layer CN emissions with pure graphite models heated to surface temperatures ranging from 1770-3300 K. These results were compared with numerical simulations which predicted a monotonic increase of emissions with surface temperature for all models considered, whereas the experiments showed an initial increase from 1770-2500 K and then remained relatively constant from 2500-3300 K. The simulations also su...

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“…Promising tests and discoveries about the small X1 tube's operation led to the construction of X2 and its larger sibling X3, measuring approximately 25 m and 65 m, respectively [46]. X2 was commissioned in 1995 [39], and has undergone several significant changes to reach its current format. It moved from a compound two-stage free piston driver [47] to a lightweight single free piston driver [48] [6], and the ability to change the driver conditions using different gases and orifice plates was added.…”

Section: Experiments In the X2 Free-piston Driven Expansion Tube 22mentioning

confidence: 99%

“…The realisation of X2 as a unique, world-class facility has progressed through many stages, and this is well-documented by current and past members of the Centre for Hypersonics, which the readers are encouraged to view (including [39], [6], [40], [41]). From a theoretical concept by Resler and Bloxom [42], early performance predictions by Trimpi [43] and discouraging test results from facilities including the NASA Langley expansion tube (see [44], for example), Stalker combined his free-piston driver with the expansion tube idea to create X1 at The University of Queensland [45].…”

Section: Experiments In the X2 Free-piston Driven Expansion Tube 22mentioning

confidence: 99%

Superorbital re-entry shock layers: flight and laboratory comparisons

Fahy¹

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Hypervelocity re-entry through the Earth's atmosphere surrounds an aeroshell with a radiating shock layer, which has complex and potentially critical interactions with the thermal protection system, the key component to the vehicle's survival. Aerothermodynamic re-entry flight data is rare, but the available radiation data has potential for replication in ground-based experimental and numerical testing, where flight equivalent conditions can be achieved. A greater understanding and ability to demonstrate the behaviour of re-entry vehicles will allow increased confidence in pre-flight laboratory predictions, design iterations based on testing and simulation, and an overall reduction in the thermal protection system (TPS) mass, therefore increasing the mass available for scientific payload. This thesis aims to replicate flight data from the unmanned Hayabusa and Stardust aeroshell re-entries in expansion tube experiments and numerical simulations, and assess the similarities and differences in the results. The flight data is in the form of infrared (IR) and ultraviolet (UV) spectra emanating from the bow shock, as captured by air-and ground-based observation missions.The experiments were performed in the X2 expansion tube, a hypervelocity impulse facility capable of producing flight equivalent conditions over a scaled aeroshell model for a brief test time. Prior to optical imaging tests, the conditions were designed through an iterative combination of analytical, experimental and numerical methods, based on binary scaling and enthalpy matching. Emissions from the radiating shock layers were captured by IR and UV spectroscopy, as well as two-dimensional intensity mapping through a narrow wavelength band filter, but the measurements were oriented differently to flight. The axisymmetry of certain imaging planes enabled the transformation of line of sight integrated intensities into radial quantities, which could describe the forebody shock layer and result in an integrated intensity comparable with integrated flight spectra.Numerical simulations must first model the flowfield before radiation modelling is possible. Compressible flow computational fluid dynamics (CFD) simulations were performed for the Hayabusa and Stardust flight vehicles at the selected trajectory points, and scaled models at idealised and simulated inflow conditions. Radiation spectra calculations were performed along the same lines of sight as imaged in experimental spectra, and over the entire flowfield to be comparable to flight data and experimental 2D imaging.iii The flight, experimental and numerical data combined for a series of comparisons to test the hypotheses that under binary scaling, spectral radiance along a line of sight is invariant, and radiative intensity scales with the square of the length scale. Spectra comparisons between experiment and CFD, and CFD and flight, tested the first hypothesis, and integrated intensity comparisons between experiment and CFD, and experiment and flight, tested the second hypothesis. Favourabl...

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Expansion Tubes in Australia

Cited by 62 publications

References 46 publications

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Venus Entry Flow over a Decomposing Aeroshell in X2 Expansion Tube

Hypervelocity shock layer emission spectroscopy with high temperature ablating models

Superorbital re-entry shock layers: flight and laboratory comparisons

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