CO2 vibrational temperature measurements in CO + N2O gasdynamic laser

Kudriavtsev, N. N.; Новиков, С. С.; Svetlichnyi, I. B.

doi:10.1016/b978-0-08-025442-5.50038-x

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(3 citation statements)

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“…This non-equilibrium region was experimentally found to be more pronounced in lower enthalpy conditions [39] [28], which may explain the why the feature in Figure 4.36 is not seen in the 3.4 and 4.0 km/s conditions. Also mentioned in section 2.2, the 4.3 µm band corresponds to the fundamental transitions of the 3 asymmetric stretching vibrational mode [19], whereas the 2.7 µm band corresponds to the simultaneous transitions in the 1 and 3 and the 2 and 3 vibrational modes [22]. Thus, the cause of the observation seen in…”

Section: Resultsmentioning

confidence: 91%

“…In particular, the radiation is produced by the 2.7 µm and 4.3 µm bands of carbon dioxide. The ro-vibrational transition causing the 4.3 µm band is produced by single quantum transitions in the 3 asymmetric stretching mode with the rotational energy level either remaining the same or changing by a single quantum level [18] [19]. These transitions are called fundamental transitions and produce the strongest radiation emissions [20].…”

Section: Carbon Dioxide Thermochemistry and Radiationmentioning

confidence: 99%

“…This is illustrated in Figure 6. 19 where the chemical kinetics model 'BC' is the same model used in the CFD simulations in the current work. Hence, their scaling factor is independent of the location behind the shock wave.…”

Section: Band Radiancementioning

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: Resultsmentioning

confidence: 91%

Section: Carbon Dioxide Thermochemistry and Radiationmentioning

confidence: 99%