高压压气机出口级叶型加工偏差特征及其影响

以高压压气机出口级叶片叶中截面作为研究对象,获得了实际压气机叶片加工偏差的分布特征,并分析了实际加工偏差对叶型气动性能的影响。以此为基础,研究了加工偏差对叶型性能的影响机理。研究结果表明,实际叶型加工偏差存在一定的系统性偏差,从而导致实际叶型气动性能的平均值偏离设计值。叶型偏差对叶型气动性能的影响存在一定的非线性效应,这在前缘区域更为明显,从而导致了平均叶型的气动性能与实际叶型平均性能出现了明显偏差。前缘附近的几何偏差对吸力面和压力面的速度峰值有较大的影响,因此前缘附近的偏差是使叶型的气动性能产生系统性偏差和增大不确定度的主要因素。根据对流动机理的分析,进口几何角偏差是导致叶型性能出现系统性偏差的主要原因;可以近似用均匀偏差来估计叶身加工偏差对正负攻角范围和损失的影响。     

多节点探测器软着陆的路径规划方法

面向小行星探测任务的需要,柔性连接的多节点深空探测器是针对单节点探测器着陆易倾覆或反弹等问题的一种解决方案.基于此构建了一种采用柔性连接的三节点探测器并对其软着陆情况进行建模,提出了带自注意力机制的多任务深度强化学习方法.各节点以探测器主体为参照物描述自身状态,节点之间通过联合学习来提高各自对复杂环境的适应能力;在对探...     

Design and analysis of truss deployable antenna mechanism based on a novel symmetric hexagonal profile division method

As the deployment, supporting, and stability mechanisms of satellite antennas, space-deployable mechanisms play a key role in the field of aerospace. In order to design truss deployable antenna supporting mechanisms with large folding rate, high accuracy, easy deployment and strong stability, aiming at the geometric division of the parabolic reflector, a novel method based on symmetric hexagonal division and its corresponding modular truss deployable antenna mechanism is proposed, and the original method based on asymmetric triangular division and its corresponding mechanisms are presented for comparative analysis. Then, the screw theory is employed to analyze the mobility of different mechanisms. Furthermore, the improved three-dimensional mesh method is used to divide the reflector surface of a large parabolic antenna designed by the two different methods, and the profile accuracy and the type of links are taken as the evaluation indexes to quantitatively analyze the division results. Finally, a three-dimensional model of the modular deployable mechanism based on the symmetric hexagonal design is developed, and the deployable mechanisms with different configurations based on the two design methods are compared and analyzed from the mechanical perspective. The research results provide a good theoretical reference for the design of deployable truss antenna mechanisms and their application in the aerospace field.     

Multiscale modeling of mechanical behavior and failure mechanism of 3D angle-interlock woven aluminum composites subjected to warp/weft directional tension loading

The mechanical behavior and progressive damage mechanism of novel aluminum matrix composites reinforced with 3D angle-interlock woven carbon fibers were investigated using a multiscale modeling approach. The mechanical properties and failure of yarns were evaluated using a microscale model under different loading scenarios. On this basis, a mesoscale model was developed to analyze the tensile behavior and failure mechanism of the composites. The interfacial decohesion, matrix damage, and failure of fibers and yarns were incorporated into the microscopic and mesoscopic models. The stress–strain curves and fracture modes from simulation show good agreement with the experimental curves and fracture morphology. Local interface and matrix damage initiate first under warp directional tension. Thereafter, interfacial failure, weft yarn cracking, and matrix failure occur successively. Axial fracture of warp yarn, which displays a quasi-ductile fracture characteristic, dominates the ultimate composites failure. Under weft directional tension, interfacial failure and warp yarn rupture occur at the early and middle stages. Matrix failure and weft yarn fracture emerge simultaneously at the final stage, leading to the cata-strophic failure of composites. The weft directional strength and fracture strain are lower than the warp directional ones because of the lower weft density and the more serious brittle fracture of weft yarns.     

新型钕铁硼永磁材料化学与热稳定性研究

钕铁硼永磁材料以其高磁性能、不易脆、价格低的优点逐渐成为第3代永磁材料,但其在热稳定性和化学稳定性方面的缺陷一直阻碍其在航天机电产品上的推广应用。文章针对钕铁硼永磁体的稳定性进行分析研究,并结合空间电机的应用实际成功解决了缺陷问题,为钕铁硼永磁材料在航天用永磁无刷直流电机上的广泛应用提供了参考。     

均匀磁场中高超声速弱电离气体流动数值模拟

采用7组元化学模型并应用组分公式计算电导率,通过求解黏性MHD(magneto-hydro-dy-namics)方程组,研究了不同强度均匀磁场对三维钝头体高超声速绕流化学非平衡流动的影响.结果表明,随着磁场的增强,激波脱体距离逐渐增加;总阻力系数和壁面温度逐渐减小.在B_y=0.03 T磁场作用下,与无磁场的结果相比,化学非平衡流中的激波脱体距离增加约7%,总阻力系数减小约5%,局部壁面温度最大降低74%;而冻结流中的激波脱体距离增加约43%,总阻力系数减小约6.9%,局部壁面温度最大降低18%.      

最小二乘支持向量回归机在可靠性分析中的应用(英文)

经典的响应面方法作为回归方法来模拟可靠性设计中的状态变量和基本变量之间的函数关系,用以解决直接数值模拟方法计算量大的问题。这类算法已经成功解决了一些隐式功能函数的可靠性分析问题,但它依据的"经验风险最小"原则影响了它的使用范围。基于"结构风险最小化"的支持向量回归机方法具有良好的小样本学习性能和泛化能立,比传统的回归方法具有优越性。但支持向量回归机方法对大样本的可靠性问题在时间和空间上开销巨大。为了克服这一不足,本文将最小二乘支持向量回归机引入到可靠性分析中。算例结果表明:基于最小二乘支持向量回归机的可靠性方法计算得到结果精度较高,在计算耗时上远小于支持向量回归机的可靠性方法,因此在工程应用上具有一定价值。     

基于变论域的导弹电液伺服机构自适应模糊滑模控制

针对导弹电液伺服机构的跟踪控制,提出了一种自适应变论域模糊滑模的设计方案。引入变论域自适应模糊控制器,在线调节输入变量论域和规则后件隶属度函数以逼近理想控制器,使控制器的设计不依赖于被控对象的精确数学模型,确定模糊滑模补偿控制项,以补偿逼近误差并消除外部干扰的影响。仿真实验结果验证了该控制方案的有效性。     

对接机构方案样机轴向缓冲力仿真分析与试验验证

在对接机构方案样机缓冲试验中发现了轴向缓冲力超标的问题. 针对这一问题, 理论分析了轴向缓冲力过大的原因, 进行了仿真计算, 给出了降低轴向缓冲力的措施, 并在对接机构方案样机上实施了部分措施进行验证试验, 验证试验数据表明仿真正确、措施有效. 仿真也复现了飞行器模拟件自振频率对轴向缓冲力的影响, 并在飞行器模拟件的模态测试中得到了验证, 仿真给出了必须对试验数据进行滤波分析的结论.      

含气相细节化学反应的二硝酰胺铵燃烧模型

为了研究二硝酰胺铵ADN(Ammonium DiNitramide)燃烧中的细节物理化学过程,建立了一个包含细节气相化学反应的ADN燃烧数学计算模型.该模型基于总连续方程,组元连续方程及能量守恒方程而建立,并运用了有限速率化学动力学原理,最后引入多组元系统状态方程以封闭方程组.此外,该燃烧模型还成功应用了包含34种组元和165个细节气相化学反应的化学动力学方案.使用该模型对0.3MPa下ADN燃烧气相组元摩尔分数与火焰温度分布进行预测,计算结果与试验数据相当吻合,说明该燃烧能够准确描述ADN气相燃烧波结构.