大负荷低压涡轮叶型分离转捩流动的大涡模拟

应用动力模式大涡模拟数值方法,对来流无扰动、不可压、雷诺数为5×104(基于进口速度和轴向弦长),定常来流条件下大负荷低压涡轮叶型(Pak B)叶型吸力面非定常分离转捩流动进行了三维数值模拟。在与相关实验数据的对比基础之上,对非定常流动物理信息进行了详细的分析讨论,揭示了计算来流状态下的Pak B叶型吸力面非定常分离转捩流动机理。结果表明,由无粘Kelvin-Helmholtz机制产生的、空间线性增长的初始二维不稳定性在分离剪切内诱导展向旋涡形成并脱落,脱落过程中的展向涡在非线性增长的三维不稳定性作用下发生变形并最终破碎成湍流。计算得到的Kelvin-Helmholtz不稳定性特征频率处于相关实验测量范围内。     

RANS方程和附面层方程耦合求解转捩位置的方法

研究了基于线性稳定性分析的RANS（Reynolds-Averaged Navier-Stokes）方程和附面层方程耦合求解转捩位置的方法。RANS方程计算得附面层外边界的速度分布作为附面层方程计算的输入,求解附面层方程得到稳定性分析需要的附面层参数。由于附面层的解在分离点处的奇异性,用交互式附面层方程求解方法。用基于线性稳定性分析的e^N方法计算转捩位置,并考虑了Tollmien-Schliching波和层流附面层分离造成的转捩。迭代求解RANS方程和附面层方程,直到转捩位置收敛。RANS求解中使用转捩过渡区模型,避免了点转捩模型引入的数值扰动。通过对NA-CA0012翼型的计算并和实验结果及Xfoil计算的结果进行比较,吻合较好,有较好的工程实用价值。     

案例推理和神经网络在航空发动机稳态模型中的应用

传统建模方法难以准确建立航空发动机数学模型,单纯使用BP神经网络建模又有其不足.将案例推理和改进BP方法相结合,根据案例推理优化训练数据,再利用神经网络,建立了发动机稳态模型.结果表明,该模型有较高的稳态精度,而且具有较好的泛化能力.     

基于PSPICE的典型电路故障判定算法研究

文章给出典型电路故障判定信号特征参数的一般算法,针对PSPICE环境下特征参数仿真输出的数据特点,主要对3类参数算法进行变换、改进,并验证了它的有效性。     

CAS-1 lunar soil simulant

Lunar soil simulant is a geochemical reproduction of lunar regolith, and is needed for lunar science and engineering researches. This paper describes a new lunar soil simulant, CAS-1, prepared by the Chinese Academy of Sciences, to support lunar orbiter, soft-landing mission and sample return missions of China’s Lunar Exploration Program, which is scheduled for 2004–2020. Such simulants should match the samples returned from the Moon, all collected from the lunar regolith rather than outcrops. The average mineral and chemical composition of lunar soil sample returned from the Apollo 14 mission, which landed on the Fra Mauro Formation, is chosen as the model for the CAS-1 simulant. Source material for this simulant was a low-Ti basaltic scoria dated at 1600 years from the late Quaternary volcanic area in the Changbai Mountains of northeast China. The main minerals of this rock are pyroxene, olivine, and minor plagioclase, and about 20–40% modal glass. The scoria was analyzed by XRF and found to be chemically similar to Apollo 14 lunar sample 14163. It was crushed in an impact mill with a resulting median particle size 85.9 μm, similar to Apollo soils. Bulk density, shear resistance, complex permittivity, and reflectance spectra were also similar to Apollo 14 soil. We conclude that CAS-1 is an ideal lunar soil simulant for science and engineering research of future lunar exploration program.     

多分格相关与皮尔逊相关的蒙特卡罗仿真

为了解对于有序分类数据,使用多分格相关系数估计数据间线性依存关系的精确性,运用蒙特卡罗仿真法考察样本量的大小、分类数的多少、相关程度的高低以及数据分布的偏度对多分格相关系数估计精确度的影响;同样条件下计算皮尔逊相关系数并与之相比较.在实验设计的条件下,多分格相关系数的表现非常稳定,绝大多数情况下给出的估计值都比皮尔逊相关系数更精确.两种相关系数受样本量的影响都很有限,且估计值的偏差会明显随着分类数的增多而变小;但数据的偏态分布对皮尔逊相关系数的精确度有很大影响.     

基于Fliess泛函展开式的航天器姿态控制

绍用Fliess泛函展开式研究航天器姿态控制问题。首先讨论一步预测及多步预测下的姿态跟踪。接着讨论当系统的解耦矩阵满秩时,在适当反馈下,闭环系统的Fliess泛函展开式具有有限项。由于航天器姿态动态方程具有非奇异解耦矩阵,有限项Fliess泛函展开式可以方便地应用于航天器姿态控制的在线设计。     

畸变进气下压气机三维黏性数值计算模型

通过对压气机环形无叶片通道求解带源项的N-S(Navier-Stokes)方程,实现对压气机全通道流场的计算,建立了压气机三维黏性非定常数值计算模型.源项是由三维计算流体动力学(CFD)求解器定常计算的气流参数计算得到,求得不同工作点源项大小,然后根据进口参数对源项插值得到当前计算点源项.采用该模型对某跨声速单级压气机在均匀进气下性能和流场的计算结果与实验结果进行了对比,两者能够较好的一致,验证了模型的可靠性;之后应用该模型对周向总压畸变进气下的流场和性能进行了计算,分析了畸变进气对压气机三维流场和性能的影响,并引入压气机失稳判据分析畸变对压气机稳定性的影响.      

Deformation Compensation of Ram Components of Super-heavy-duty CNC Floor Type Boring and Milling Machine

Ram is a very important component of super-heavy-duty computer numerical control (CNC) floor type boring-milling machine, and deformation of ram is a significant source causing errors in machining process. To compensate the deformation error of super-heavy-duty CNC floor type boring-milling machine, based on force analysis theory, the law and compensation measures of deformation of ram are researched. Based on the principle of torque (force) balance of the ram components, the formulas of compensation forces and compensation torques are derived, the relations between compensation forces (compensation torques) and the stroke distance of the ram are given. According to theoretical analysis results and the structural characteristics of super-heavy-duty CNC floor type boring and milling machine of TK6932, rods compensation, hydrostatic pressure compensation and wire rope compensation measures are taken to compensate the deformation error of ram. The experiments and computer simulation results show that the straightness of the ram at its overhanging end meets the national machinery industry standards.     

颗粒增强铝基复合材料研究与应用发展

简要分析了颗粒增强铝基复合材料的性能优势,综述了国外颗粒增强铝基复合材料的制备技术、性能水平、工程化应用技术以及应用发展现状,总结了国内工程化应用研究现状,提出了铝基复合材料在航空航天领域的应用发展方向.