Implementation of a state-to-state analytical framework for the calculation of expansion tube flow properties

James, Christopher M.; Gildfind, David; Lewis, Steven W.; Morgan, Richard G.; Zander, Fabian

doi:10.1007/s00193-017-0763-3

Cited by 69 publications

(48 citation statements)

References 50 publications

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“…The experiments are used to validate and fine-tune the modelling, which then allows estimation of the free-stream properties. Full details of the procedure are described by James et al [107], so only a summary is provided here.…”

Section: Appendicesmentioning

confidence: 99%

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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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Section: Appendicesmentioning

confidence: 99%

“…The process used for characterising the test conditions involved a combination of experiments and facility modelling using UQ's in-house shock tunnel simulation code, PITOT [103,107]. The experiments are used to validate and fine-tune the modelling, which then allows estimation of the free-stream properties.…”

Section: Appendicesmentioning

confidence: 99%

Hypervelocity shock layer emission spectroscopy with high temperature ablating models

Lewis¹

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“…The measured bar gauge pitot pressure is then compared to a calculated nominal pitot pressure at State 8 (nozzle exit condition) determined by PITOT, a UQ shock tunnel simulation code presented in James et al [22]. PITOT can use either the experimental shock tube shock speed or acceleration tube shock speed or both simultaneously to perform the rest of the theoretical modelling.…”

Section: Comparison Of All Testsmentioning

confidence: 99%

“…These will be compared to calculated pitot pressures determined by James et al [22] using PITOT in Table 12 below. Firstly, the reading for the bar gauge had to be converted from mV to kPa using the calibration factor of 0.0001772714219 V/kPa determined in Section 4.3.…”

Section: Comparison Of All Testsmentioning

confidence: 99%

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Pitot pressure measurement in high enthalpy expansion tubes

Saric¹

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This report has investigated the use of a new bar gauge design in order to replace previous iterations of bar gauges and pitot pressure probes for use within UQ's expansion tube facilities.Preliminary hammer calibration testing on different arrangements of the bar gauge showed that the response remained almost constant regardless of shielding, no shielding or different clamping arrangements, varying by only a maximum of 14.59%. It was also concluded that the ratio of strain gauge output to hammer input remained almost constant for the entire test time, and that a calibration factor taken at the 50µs surrounding the peak of the signal will yield the most accurate result. It was determined that due to this reason, deconvolution was not necessary because the response could be characterised using a constant value, known as the calibration factor.

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Development of a Total Enthalpy and Reynolds Number Matched Apollo Re-entry Condition in the X2 Expansion Tunnel

Cullen

James

Gollan

et al. 2019

31st International Symposium on Shock Waves 2

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Implementation of a state-to-state analytical framework for the calculation of expansion tube flow properties

Cited by 69 publications

References 50 publications

Hypervelocity shock layer emission spectroscopy with high temperature ablating models

Hypervelocity shock layer emission spectroscopy with high temperature ablating models

Pitot pressure measurement in high enthalpy expansion tubes

Development of a Total Enthalpy and Reynolds Number Matched Apollo Re-entry Condition in the X2 Expansion Tunnel

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