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931.
Miroslav A. Rozhkov Olga L. Starinova Irina V. Chernyakina 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(9):2757-2766
Detailed dynamic modeling of a solar sail requires recording of solar radiation pressure influence. A photon-solar sail is determined by the thrust value and the direction. We define the solar sail’s reflectivity depending on the film materials, the sail design and temperature, the thickness of multiple layers, and degradation factor, with a reasonable degree of accuracy. Thus, this work is devoted to the identification of optical characteristics of thin multilayer films in space flight conditions, i.e. to finding its reflectance, absorbance, and transmittance. In particular, the paper asks whether the solar sail simulates by a mathematical model of the optical characteristics of a multilayer epitaxial thin film. The temperature change effect and optical properties of solar sail degradation are considered as well. Solar sail flight from Earth to Mercury is designed as a simulation of the flight change in optical parameters. 相似文献
932.
为了找到一种改善低平尾涡桨飞机中小迎角下纵向静稳定度的方法,采用数值模拟手段研究了螺旋桨旋转方向对飞机俯仰力矩特性的影响。基于动态面搭接网格技术和非定常雷诺平均Navier-Stokes (URANS)方程,首先对某T尾双发涡桨飞机进行了计算,验证了方法的精度和可靠性,然后对同向旋转(CO)、对转-内侧上洗(CNIU)和对转-外侧上洗(CNOU)3种低平尾涡桨飞机构型开展了数值模拟,分析了各构型的俯仰力矩变化特点及流场细节。研究结果表明:对于常见的CO构型,在小迎角下由于平尾整体效率降低,飞机的俯仰力矩曲线斜率较无动力构型大幅度下降;在小迎角下,CO构型左侧平尾的效率几乎丧失,但右侧平尾却具有良好的效率;CO构型左右两侧平尾的效率呈现巨大差异的主要原因在于两侧平尾当地的下洗梯度不同;3个构型中,CNOU构型的俯仰力矩特性最差,CNIU构型在整个中小迎角范围内都能保持良好的俯仰力矩特性。 相似文献
933.
For a typical pressurized system with a novel dual-stage gas pressure reducing regulator, a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components. 相似文献
934.
935.
《中国航空学报》2020,33(9):2329-2341
The Pulsed Inductive Thruster (PIT) has the advantages of repeatable startup, no corruption and in-situ propellant feed. To study the flow expansion and circuit characteristics of PITs, the circuit-fluid model is developed, and the high temperature thermodynamic and transport models are combined with the circuit-fluid model to predict the critical plasma parameters. The flow fields of initial mass of 2–8 mg and charge voltages of 10–14 kV are simulated. Comparison of the flow fields of argon and helium propellants suggests that, the flow field structures are similar. Slight differences exist on the magnitude of the density and magnetic field, caused by larger velocity in lighter atom case and difference on the ionization gap between adjacent ionization levels. Analysis of the circuit characteristics by the two-dimensional results indicates that the ratio of coil inductance to circuit inductance affects both the rise rate and phase of the plasma current, the larger the ratio, the greater the rise rate and the better the following characteristic. The calculations show that the magnetic energy obtained within the decoupling distance determines the overall performance the thruster can be obtained; self-induced field maintained by the thermal motion after the main pulse leads to the long attenuation process and difference on the total impulse when the angle of conical pylon is varied under constant coil dimension. 相似文献
936.
The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization method is applied to update the concentration of contaminated particles within the LEHA, in order to gain insight into the erosion degradation process at various stages of degradation. The main contribution of the proposed model is the application of the dynamic concentration of contamination particles in erosion analysis of Electro-Hydraulic Servo Valves (EHSVs), throttle valves, spool valves, and needle valves. The effects of system parameters and working conditions on component wear are analyzed by simulations. The results of the proposed model match the expected degradation process. 相似文献
937.
航天器火工冲击环境复杂,冲击载荷的瞬态、高度非线性等特点,使得冲击响应的准确预示具有一定难度。卫星舱板上分布大量单机设备,其质量特性成为影响火工冲击传递的关键因素。根据火工冲击传递机理,建立了卫星舱板与单机设备的冲击有限元简化模型,计算了舱板上的火工冲击响应。通过与试验数据的对比,误差控制在±35dB内,验证了有限元建模的合理性。以此为基础,研究了火工冲击传递特性,为火工冲击响应预示及卫星舱板布局设计提供了参考。 相似文献
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