In order to achieve a wide-range design for the inlet of an atmosphere-breathing electric propulsion system operat-ing in the upper atmosphere, a comprehensive numerical analysis is performed to investigate gas flows inside the inlet using the direct simulation Monte Carlo method. The effects of inlet geometry and gas-surface interaction (GSI) model on flow features, compression and collection performances are considered and the underlying physical mechanism is interpreted based on the gas kinetic theory. Results show that, for the case of completely diffuse re-flection, the converging effect induced by the concave inlet leads to a larger gas pressure and mass flux, with the high-pressure region close to the ionization section, while the diverging effect caused by the convex inlet results in a smaller gas pressure and mass flux, with the high-pressure region far from the ionization section. For the case of GSI accommodation coefficient σ = 0.5, both the gas pressure and mass flux achieve their local peak values at some locations in the ionization section. The underlying mechanism behind the phenomena is that, after reflecting in a specular manner from the concave surface similar to a paraboloid, gas molecules congregate at the focus and enter the ionization section. The drop of GSI accommodation coefficient from 1 to 0.5 brings about a considerable in-crease in the compression factor and collection efficiency, achieving a rate of increase of 85%~125% and 55%~77%, respectively. For the cases of completely and partially diffuse reflections, the concave inlet has the best compression and collection performances. Under some reasonable assumptions, the concave inlet with a GSI ac-commodation coefficient of 0.5 can produce a thrust at the altitude of 180 km, which is larger than the atmospheric drag. Therefore, this inlet design is feasible in concept.
[1] https://www.cast.org.cn/xw/BWTJ/art/2023/art_32e91b9e6bdd45d5aa8c1dd01b6c72aa.html （中国科协官网）
[2] 沈清, 黄飞, 程晓丽, 靳旭红. 飞行器上层大气层空气动力特性探讨 [J]. 气体物理, 2021, 6(1): 1-9.
[3] Chen Z, Huang F, Jin X H, et al. A novel lightweight aerodynamic design for the wings of hypersonic vehicles cruising in the upper atmosphere [J]. Aerospace Science and Technology, 2020, 109: 106418.
[4] Crisp N H, Roberts P, Livadiotti S, et al. The benefits of very low earth orbit for earth observation missions [J]. Progress in Aerospace Sciences, 2020, 117: 100619.
[5] Crisp N H, Roberts P, Livadiotti S, et al. In-orbit aerody-namic coefficient measurements using SOAR (Satellite for Orbital Aerodynamics Research) [J]. Acta Astronauti-ca, 2021, 180: 85-99.
[6] Prieto D M, Graziano B P, Roberts P. Spacecraft drag modelling [J]. Progress in Aerospace Sciences, 2014, 64:56-65.
[7] Nishiyama K. Air breathing ion engine concept. In: Pro-ceedings of 54th International Astronautical Congress of the International Astronautical Federation. Reston: AIAA, 2003. 1-8.
[8] Pekker L, Keidar M. Analysis of airbreathing Hall-effect thrusters [J]. Journal of Propulsion and Power, 2012, 28:1399-1405.
[9] Andreussi T, Ferrato E, Paissoni C A, et al. The AETHER project: development of air-breathing electric propulsion for VLEO missions [J]. CEAS Space Journal, 2022, 14: 717–740.
[10] Romano F, Massuti-Ballester B, Binder T, et al. System analysis and test-bed for an atmosphere-breathing electric propulsion system using an inductive plasma thruster [J]. Acta Astronautica, 2018, 147: 114-126.
[11] 靳旭红, 程晓丽, 沈清, 艾邦成. 吸气式电推进系统进气道气体流动数值分析 [J]. 中国科学: 物理学 力学 天文学, 2024.
[12] Romano F, Chan Y A, Herdrich G, et al. RF Helicon-based inductive plasma thruster (IPT) design for an at-mosphere-breathing electric propulsion system (ABEP) [J]. Acta Astronautica, 2020, 176: 476-483.
[13] Singh L A, Walker M L R. A review of research in low earth orbit propellant collection [J]. Progress in Aero-space Sciences, 2015, 75: 15-25.
[14] Wu J, Zheng P, Zhang Y, et al. Recent development of intake devices for atmosphere-breathing electric propul-sion system [J]. Progress in Aerospace Sciences, 2022, 133: 100848.
[15] Andreussi1 T, Ferrato E, Giannetti V. A review of air?breathing electric propulsion: from mission studies to technology verification [J]. Journal of Electric Propulsion, 2022, 1:31.
[16] Tagawa M, Yokota K, Nishiyama K, et al. Experimental study of air breathing ion engine using laser detonation beam source [J]. Journal of Propulsion and Power, 2013, 2: 501-506.
[17] Jackson S W, Marshall R. Conceptual design of an air-breathing electric thruster for CubeSat applications [J]. Journal of Spacecraft and Rockets, 2018, 55: 632-639.
[18] Romano F, Espinosa-Orozco J, Pfeiffer M, et al. Intake design for an Atmosphere-Breathing Electric Propulsion System (ABEP) [J]. Acta Astronautica, 2021, 187: 225-235.
[19] Li Y, Chen X, Li D, et al. Design and analysis of vacuum air-intake device used in air-breathing electric propulsion [J]. Vacuum, 2015, 120: 89-95.
[20] Zheng P, Wu J, Wu B, et al. Design and numerical inves-tigation on the intake of atmosphere-breathing electric propulsion [J]. Acta Astronautica, 2021, 188: 215-228.
[21] Zheng P, Wu J, Zhang Y, et al. Design and optimization of vacuum intake for atmosphere-breathing electric pro-pulsion (ABEP) system [J]. Vacuum, 2022, 195: 110652.
[22] 谢晓乐, 李济源, 王娴, 等. 吸气式电推进系统近进气道结构对进气性能的影响 [J]. 航空学报, 2022, 43(3): 125272.
[23] Jin X H, Miao W B, Cheng X L, et al. Monte Carlo sim-ulation of inlet flows in atmosphere-breathing electric propulsion [J]. AIAA Journal, 2024.
[24] Jin X H, Cheng X L, Huang Y Q, et al. Numerical analy-sis of inlet flows at different altitudes in the upper atmos-phere [J]. Physics of Fluids, 2023, 35: 093605.
[25] Boyd I D, Van Gilder D. B, Liu X. Monte Carlo simula-tion of neutral xenon flows in electric propulsion devices [J]. Journal of Propulsion and Power, 1998, 14: 1009-1015.
[26] 靳旭红, 黄飞, 程晓丽, 等. Maxwell气固相互作用模型对稀薄高超声速凹腔绕流流动特征和热环境的影响 [J]. 航空学报, 2021, 42(3): 124118.
JIN Xuhong, HUANG Fei, CHENG Xiaoli, et al. Effect of gas-surface interaction models on flow characteristics and thermodynamic properties of rarefied hypersonic cavity flows [J]. Acta Aeronautica et Astronautica Sinica, 2021, 42(3): 124118. (in Chinese)
[27] Livadiotti S, Crisp N H, Roberts P C E, et al. A review of gas-surface interaction models for orbital aerodynamics applications [J]. Progress in Aerospace Sciences, 2020, 119: 100675.
[28] BIRD G A. Approach to translational equilibrium in a rigid sphere gas [J]. Physics of Fluids, 1963, 6: 1518–1519.
[29] BIRD G A. Molecular gas dynamics and the direct simu-lation of gas flows [M]. New York: Oxford University Press, 1994: 340–346.
[30] 靳旭红, 黄飞, 程晓丽, 王强. 稀薄流区高超声速飞行器表面缝隙流动结构及气动热环境的分子模拟 [J]. 航空动力学报, 2019, 34(1): 201-209.
[31] BIRD G A. Monte Carlo simulation of gas flows [J]. Annual Review of Fluid Mechanics, 1978, 10(8): 11–31.
[32] BORGNAKKE C, LARSEN P S. Statistical Collision Model for Monte Carlo Simulation of Polyatomic Gas Mixture [J]. Journal of Computational Physics, 1975, 18(4): 405–420.
[33] Rothe D E. Electron-beam studies of viscous flow in supersonic nozzles [J]. AIAA Journal, 1971, 9: 804-811
[34] Chung C H, Kim S C, Stubbs, R M, et al. Low-density nozzle flow by the direct simulation Monte Carlo and continuum methods [J]. Journal of Propulsion and Pow-er, 1995, 11: 64-70.
[35] Garrigues L. Computational study of Hall-effect thruster with ambient atmospheric gas as propellant [J]. Journal of Propulsion and Power, 2012, 28: 344-354.
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