煤油-氧火焰中铁的辐射光谱实验研究

为了对羽流激波中金属光谱特性进行研究,用煤油-氧火焰气体模拟煤油-氧发动机的羽流,以二茂铁溶于煤油模拟发动机材料铁的磨损,给出不同混合比下铁在火焰中辐射光谱的实验与仿真结果.实验光谱数据随铁的浓度不同而变化,理论光谱与实验结果吻合较好,验证了羽流中金属原子辐射光谱的仿真程序.为基于羽流光谱分析的发动机故障诊断研究奠定了实验与理论基础.     

真空羽流污染的数值模拟

姿控发动机真空环境下工作产生的喷流对航天器造成的污染非常严重.根据污染的性质,羽流污染又分为机械污染、热污染、沉积污染和化学污染.用直接模拟的蒙特卡罗(DSMC)法数值求解真空羽流场,在此基础上计算热污染和沉积污染,将对空间飞行器的设计和科学实验有参考价值.      

基于海杂波稀疏性与非均匀度的样本挑选方法

针对预警雷达对海监视面临海杂波分布非均匀与杂波样本受目标污染,导致自适应杂波抑制处理性能恶化和目标能量损失的问题,提出了一种基于海杂波稀疏性与非均匀度的样本挑选方法。该方法将目标的导向约束与广义内积样本挑选方法结合,先利用海杂波在空时二维平面上的稀疏分布特性,根据海杂波与目标空时二维分布差异剔除被目标污染的样本,再利用广义内积准则衡量海杂波分布的非均匀程度,并获取均匀样本,以提高杂波协方差矩阵的估计精度。仿真结果表明:所提方法能在提高杂波抑制性能的同时,减小目标信号能量损失。该方法可广泛应用于海面预警监视雷达系统。     

卫星真空烘烤试验方案及验证

为降低非金属材料在试验中大量出气及产生的分子污染,文章从非金属材料挥发和凝结特性、国内外卫星真空烘烤试验的实施现状等方面进行分析,提出了卫星热真空试验前进行真空烘烤试验的方案,方案中给出了试验剖面、试验温度、试验时间以及试验压力等参数要求。在某卫星上的试验验证结果表明,该方案合理可行,有效改善了星内真空度,降低了星内污染。完成真空烘烤后的卫星在热真空试验中未发生射频组件低气压放电现象,说明真空烘烤试验能够有效防止对真空度和分子污染敏感的设备在试验中可能产生的故障。     

Numerical study on similarity of plume infrared radiation between reduced-scale solid rocket motors

This study seeks to determine the similarities in plume radiation between reduced and full-scale solid rocket models in ground test conditions through investigation of flow and radiation for a series of scale ratios ranging from 0.1 to 1. The radiative transfer equation(RTE) considering gas and particle radiation in a non-uniform plume has been adopted and solved by the finite volume method(FVM) to compute the three dimensional, spectral and directional radiation of a plume in the infrared waveband 2–6 μm. Conditions at wavelengths 2.7 μm and 4.3 μm are discussed in detail, and ratios of plume radiation for reduced-scale through full-scale models are examined. This work shows that, with increasing scale ratio of a computed rocket motor, area of the hightemperature core increases as a 2 power function of the scale ratio, and the radiation intensity of the plume increases with 2–2.5 power of the scale ratio. The infrared radiation of plume gases shows a strong spectral dependency, while that of Al_2O_3 particles shows spectral continuity of gray media.Spectral radiation intensity of a computed solid rocket plume's high temperature core increases significantly in peak radiation spectra of plume gases CO and CO_2. Al_2O_3 particles are the major radiation component in a rocket plume. There is good similarity between contours of plume spectral radiance from different scale models of computed rockets, and there are two peak spectra of radiation intensity at wavebands 2.7–3.0 μm and 4.2–4.6 μm. Directed radiation intensity of the entire plume volume will rise with increasing elevation angle.     

运输类飞机平尾失速敏感性及其试飞技术研究

从平尾失速理论研究出发,探讨了可能产生平尾失速的飞行状态,总结了可用于运输类飞机平尾失速敏感性研究的飞行试验技术,研究了平尾失速和机翼失速的相互区别,帮助飞行员在遇到机翼失速或平尾失速时进行必要的清晰判断,并采取适当的改出方法,从而保证飞机飞行安全.研究结果可为未来大型运输类飞机平尾失速敏感性试飞提供很好的技术支持.     

Plume aerodynamic effects of cushion engine in lunar landing

 During the second period of China "Tanyue" Project, the explorer will softland on the moon. The cushion engines are used to decelerate the explorer and reduce the impact on the lunar ground. It is necessary to study its plume effects on the explorer component. The self-developed PWS (Plume WorkStation) software based on direct simulation Monte Carlo (DSMC) method is used to simulate the plume effects of two 150 N engines. Due to the complex structure of the explorer, PWS uses a decoupling method to treat the boundary mesh, which mainly interacts with simulation particles, and has no relation with the computational grids. After the analytical expressions of plane surfaces and curved surfaces of each boundary block are given, the particle position within or without the boundary blocks can be easily determined. Finally the 3D plume field of two 150 N engines is simulated. The pressure, temperature and velocity distributions of plume field are clearly presented by three characteristic slices. The aerodynamic effects on the explorer bottom, the landfall legs and antenna are separately shown. The compression influence on the plume flow of four landfall legs can be observed.     

Gaseous plume flows in space propulsion

This paper presents a gaskinetic study on high-speed, highly rarefied jets expanding into a vacuum from a cluster of planar or annular exits. Based on the corresponding exact expressions for a planar or annular jet, it is convenient to derive the combined multiple jet flowfield solutions of density and velocity components. For the combined temperature and pressure solutions, extra attention is needed. Several direct simulation Monte Carlo simulation results are provided to validate these analytical solutions. The analytical and numerical solutions are essentially identical for these high Knudsen number jet flows.     

航空发动机燃油污染快速检测技术的初步研究

针对航空发动机润滑系统受到燃油污染的问题,提出1种基于红外光谱分析的快速检测技术。利用傅里叶变换红外光谱技术(FIRT),结合偏最小二乘算法(PLS),建立了燃油污染定量检测的数学校正模型。讨论了不同光谱预处理方法和PLS因子数对模型预测能力的影响。通过对光谱预处理和优化建模参数,提高了模型的预测精度,在一定的燃油质量分数范围内,得到了较为理想的数学校正模型。使用建立的分析模型对预测集样本进行预测,预测值与实际值相关性良好,相关系数R=0.9994,预测均方根误差RMSEP=0.082,重现性实验标准偏差SD=0.044~0.088。研究结果表明该燃油污染快速检测技术是可行的。     

一种超声速射流计算方法与实验验证

高温射流流场计算是尾焰辐射目标特性计算的前提,然而由于缺少可靠实验数据,针对湍流超声速射流的数值模拟多集中于低温射流,高温射流计算与实验的对比工作还很少见。利用k-ωSST双方程湍流模型,模拟了多个典型超声速射流实验的流场速度与温度分布,通过与实验结果进行对比,建立了一种超声速射流计算方法。首先,通过对比多个低温射流的实验与计算结果,探索了湍流模型中可压缩修正以及来流湍动粘性比对超声速射流计算结果的影响;进而,针对火箭发动机尾焰实验,计算尾焰流场与流场红外辐射,流场辐射计算结果与实验观测结果符合较好,进一步验证了计算方法。最终认为经过可压缩修正的k-ωSST双方程湍流模型结合湍动粘性比取值30可以作为超声射流计算中较为典型的湍流计算方法。