Measurement and Calculation of Shock Stand-off Distances over Hypersonic Spheres in CO<sub>2</sub>

Liao, Dongjun; Liu, Sen; Jian, Huang; Xie, Ai-Gen; Wang, Zonghao; Huang, Jie

doi:10.2514/6.2017-2124

Cited by 1 publication

(3 citation statements)

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“…This is because having excess energy stored in the thermochemical modes increases the shock standoff. Although CFD has been shown in the previous section to be incapable of describing transient CO2 flow in an expansion tube, CFD simulations using the two-temperature model has been shown to be capable of predicting the steady state CO2 shock wave location closely for similar inflow conditions [52] [89] [53] [105]. Therefore, a mismatch in shock wave location would likely be due to an incorrectly defined inflow condition rather than errors relating to the numerical modelling of the shock layer.…”

Section: Shock Wave Comparisonmentioning

confidence: 99%

“…Given the correct inflow, the two-temperature model has been shown to be capable of predicting the shock wave location well at similar conditions [52] [89] [105]. Therefore, comparing the computed shock wave location to the measured shock wave location can help assess the validity of the estimated inflow conditions.…”

Section: Shock Wave Locationmentioning

confidence: 99%

“…Nevertheless, this difference in shock location, although observable, is also small. Such a small discrepancy may be attributed to the limitations of the numerical model at predicting the shock location [105].…”

Section: Shock Wave Locationmentioning

confidence: 99%

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Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

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This thesis presents an experimental study of high temperature CO2 flowsfocusing on CO2 flows subjected to rapidly expanding conditions relevant to Mars entry and representative of the corner expansion around the shoulder, between the windward and leeward flows, on an entry capsule. This is an important but poorly understood aspect of spacecraft design. Past numerical research showed that, during Mars entry, the CO2 4.3 µm and 2.7 µm band radiation from the aforementioned expanding flow produce non-negligible contributions to the heating of the capsule afterbody.Consequently, this radiative heating should be considered in the sizing of the afterbody thermal protection systems (TPS). However, due to a lack of experimental research, the nonequilibrium characteristics of CO2 expanding flows are not well understood. Therefore, to help with the design of future Mars entry vehicles, it is necessary to investigate such flows.The X2 expansion tube was used to facilitate the current study. Three expansion tube test conditions with differing velocitiesnominally 2.8 km/s, 3.4 km/s, and 4.0 km/swere developed. Using a two-dimensional wedge model with a 54° convex corner along with the new conditions, flows with similarities to the expanding flow around the shoulder of an aeroshell at certain Mars entry conditions were created. Mid-wavelength infrared emission spectroscopy of the 4.3 μm and 2.7 μm bands were performed on the flow. The spectroscopic measurements were used to estimate the rotational and vibrational temperatures and the CO2 number densities using a spectral fitting method. Supplementing the spectroscopic measurements, filtered images of the 4.3 μm and 2.7 μm bands were taken to provide a two-dimensional spatial map of the band radiance in the flow around the wedge. Estimates of the experimental inflow conditions were produced by solving for the intermediate test gas states using measurements of various properties of the operating condition. CO2 spectroscopic measurements of the inflow along with measurements of the wedge model shock location and deduced post-shock conditions were also used to help characterize the test conditions. Using estimated inflow conditions, three-dimensional CFD simulations of the experiments were conducted using a two-temperature model. The computed results were compared to the available measurements to examine the appropriateness of the current numerical model at simulating the CO2 flow.Important qualitative results were obtained in this thesis in regards to the high temperature CO2expanding flow. The temperatures estimated in the wedge flow using both the 2.7 and 4.3 µm spectroscopic measurements were found to be the same. This provides some confidence to the validity of NEQAIR, using CDSD-4000, at predicting CO2 radiation under gas-dynamic conditions which are more relevant to Mars entry. Using the estimated rotational and vibrational temperatures, the CO2 II thermal non-equilibrium in the expanding flow was shown to be smallless than 10%. As the experiments simulate the expanding fl...

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Section: Shock Wave Comparisonmentioning

confidence: 99%

Section: Shock Wave Locationmentioning

confidence: 99%

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Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

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Measurement and Calculation of Shock Stand-off Distances over Hypersonic Spheres in CO₂

Cited by 1 publication

References 12 publications

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

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Measurement and Calculation of Shock Stand-off Distances over Hypersonic Spheres in CO2

Cited by 1 publication

References 12 publications

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

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Measurement and Calculation of Shock Stand-off Distances over Hypersonic Spheres in CO₂