Flow Enthalpy of Nonequilibrium Plasma in 1 MW Arc-Heated Wind Tunnel

Takahashi, Yusuke; Enoki, Naoya; Koike, Toshio; Tanaka, Mayuko; Yamada, Kazuhiko; Shimoda, Takayuki

doi:10.2514/1.j058407

Cited by 6 publications

(11 citation statements)

References 51 publications

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“…The test model with a diameter of 50 mm was located at x = 150 mm. A previous study [35] reported that strong thermal nonequilibrium is also observed inside the nozzle, where the electron temperature and vibrational temperature at the nozzle exit (x = 0 mm) are higher than the translational and rotational temperatures. This trend was the same as that of the free jet in the test chamber.…”

Section: Shock Layer Structurementioning

confidence: 88%

“…For each, we calculated the mean value and standard deviation from the rotational temperature result obtained by spectral fitting. The determination of the rotational temperature of the free jet spectra is described in reference [35]. The NO rotational temperature in the shock layer was 6620 ± 350 K; this is higher than the free jet rotational temperature of 770 ± 60 K. This is because the translational temperature first increases due to the flow stagnation across the shock wave, following which the rotational temperature increases owing to the energy relaxation process from the translational to the rotational degrees of freedom.…”

Section: Measured Rotational Temperaturementioning

confidence: 97%

“…test chamber inlet). In this study, we used the computational results reported by Takahashi et al [35], which numerically reproduced the arc discharge and supersonic expansion in the arc-heated wind tunnel. The results were validated on comparison with the experimental data.…”

Section: Arc-heated Flowmentioning

confidence: 99%

“…The JAXA 1 MW arc-heated wind tunnel is one of the largest wind tunnels in the world, and it has been used for TPS research and development for the Hayabusa sample return capsule [33,34]. Takahashi et al [35] determined the enthalpy of a 1 MW arc-heated free jet using spectroscopic tests and a computational science approach. However, the shock layer of the arc-heated flow has not yet been clarified.…”

Section: Introductionmentioning

confidence: 99%

“…Figure 2.Computed total enthalpy distribution at nozzle exit of arc-heated wind tunnel. From[35]. Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc.…”

mentioning

confidence: 99%

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Nonequilibrium shock layer in large-scale arc-heated wind tunnel

Takahashi¹,

Takasawa²,

Yamada³

et al. 2022

J. Phys. D: Appl. Phys.

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An arc-heated wind tunnel is one of the most important facilities to reproduce the high-temperature environment during atmospheric entry for plasma studies and spacecraft development. However, the properties of the plasma flow cannot be determined easily, because of the complex physical phenomena, such as arc discharge and supersonic expansion, occurring inside the tunnel. The shock-layer structure should be clarified to evaluate the aerodynamic characteristics, communication conditions, and thermal- protection performance in a high-temperature environment. In this study, shock-layer spectroscopic measurements of a plasma flow in a 1 MW-class arc-heated wind tunnel were performed. The γ-band system spectra of nitric oxide (NO) molecules in the ultraviolet region were measured, and the rotational temperature was determined via spectral fitting through comparison with numerical spectra. The rotational temperature of the NO molecules in the shock layer was 6,620±350 K, whereas that in the free jet was much lower at 770±60 K. This difference is attributed to the increase in translational temperature by flow stagnation across the shock wave, followed by the increase in rotational temperature owing to energy relaxation. A computational science approach revealed the detailed structure of the flow through comparisons with the spectroscopic measurement data. The wind tunnel flow became hypersonic with high temperature and low pressure due to the expansion and acceleration at the nozzle and test chamber. Although the temperature increased across the shock wave, the chemical reaction progressed slowly owing to the low-pressure environment. The rotational temperature in the shock layer increased with the translational temperature; this agrees with the trend of the measurement results. The arc-heated flow was found to be in strong thermo- chemical nonequilibrium in the shock layer. Through this study, a detailed structure of arc-heated flow was revealed and its methodology was also proposed.

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Section: Shock Layer Structurementioning

confidence: 88%

Section: Measured Rotational Temperaturementioning

confidence: 97%

Section: Arc-heated Flowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Figure 2.Computed total enthalpy distribution at nozzle exit of arc-heated wind tunnel. From[35]. Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc.…”

mentioning

confidence: 99%

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Nonequilibrium shock layer in large-scale arc-heated wind tunnel

Takahashi¹,

Takasawa²,

Yamada³

et al. 2022

J. Phys. D: Appl. Phys.

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Numerical study on instantaneous heat transfer characteristics of AC arc-fault

Yang

Zhang

et al. 2021

AIP Advances

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Studying the heat transfer characteristics of alternating current (AC) arc-fault to electrodes is a key issue in electrical fires. In this paper, an instantaneous heat transfer numerical model of AC arc-fault is developed based on the magneto-hydrodynamic principle. The temperature distribution of the AC arc at the microseconds level and the influence of heat transfer on electrodes at the seconds level when the arc heats are studied. The numerical simulation of the axial temperature of the electrodes is verified by experiments, and the temperature variation in the electrodes at different currents and times is discussed. The results show that the arc temperature varies periodically similar to the current at the microseconds level but it does not go out when the current passes zero. The high-temperature region of electrodes diffuses with the increase in current or time. However, the axial temperature gradient of the electrode decreases with time and increases with current. Furthermore, the range of temperature increase in the electrode position decreases with the increase in current and time, but the electrode position near the arc has a higher initial temperature increase.

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Experimental demonstration and mechanism of mitigating reentry blackout via surface catalysis effects

Takasawa¹,

Takahashi²,

Oshima³

et al. 2021

J. Phys. D: Appl. Phys.

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The reentry blackout phenomenon, which is the communication cut-off between the re-entry vehicle and ground station, is a crucial problem that needs to be addressed. To improve safety during reentry, a new mitigation method was proposed using the surface catalysis effect. However, this method has not been investigated extensively by experimental methods. In this study, we experimentally demonstrated the mitigation method using a 1 MW arc-heated wind tunnel and numerically clarified the mitigation mechanism. As a demonstration experiment, communication tests were conducted to compare the two cases. In the first case, a ceramic surface was used as a low catalytic wall, whereas in the second case, a copper surface was used as a high catalytic wall in the arc-heated wind tunnel. The experimental results indicated that the blackout occurred when alumina was used as the low catalytic wall. On the other hand, for the high catalytic wall using copper, blackout was avoided. The tests were reproduced in the wind tunnel using a numerical simulation technique. From the simulation results, the mitigation mechanism suggested that: (a) the number of nitrogen and oxygen atoms decreased due to catalysis; (b) forward reactions of electron impact ionization were suppressed due to the decrease in the number of atoms; and (c) the suppression of reactions decreased the number of electrons, thereby mitigating the reentry blackout. In addition, the numerical simulations performed on the reentry plasma around the re-entry capsule suggested that the mitigation mechanisms between the arc-heated wind flow and reentry plasma were similar despite the different airflow conditions.

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Flow Enthalpy of Nonequilibrium Plasma in 1 MW Arc-Heated Wind Tunnel

Cited by 6 publications

References 51 publications

Nonequilibrium shock layer in large-scale arc-heated wind tunnel

Nonequilibrium shock layer in large-scale arc-heated wind tunnel

Numerical study on instantaneous heat transfer characteristics of AC arc-fault

Experimental demonstration and mechanism of mitigating reentry blackout via surface catalysis effects

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