Non-intrusive reduced-order model for predicting transonic flow with varying geometries

A Non-Intrusive Reduced-Order Model (NIROM) based on Proper Orthogonal Decomposition (POD) has been proposed for predicting the flow fields of transonic airfoils with geometry parameters. To provide a better reduced-order subspace to approximate the real flow field, a domain decomposition method has been used to separate the hard-to-predict regions from the full field and POD has been adopted in the regions individually. An Artificial Neural Network (ANN) has replaced the Radial Basis Function (RBF) to interpolate the coefficients of the POD modes, aiming at improving the approximation accuracy of the NIROM for non-samples. When predicting the flow fields of transonic airfoils, the proposed NIROM has demonstrated a high performance.     

Improving the modeling of bottomside thickness parameters over midlatitudes and high latitudes

This paper investigates bottomside thickness parameters at Digisonde stations over midlatitude and high latitude regions, and compares the diurnal, seasonal, and solar activity variations in 2014 and 2009. The geographic latitudes of high latitude considered in this work are located beyond ±60° and those of midlatitude are located between ±40° and ±60°. The IRI-modeled B0 with ABT-2009 option (B0_IRI) are also examined and compared with four kinds of the B0 values, i.e., the observed B0 (B0_obs) from GIRO, the computed B0 following to Jamjareegulgarn et al. (2017a) (B0_old), the calculated B0 with a correction factor regarding to Jamjareegulgarn et al. (2017b) (B0_new), and the B0 with an average correction factor (B0_new_c_av). The average correction factors are proposed additionally in this work so as to assist occasionally the experimental B0 nonexistence of Digisonde which are equal to 0.2658 and 0.2058 for midlatitudes and high latitudes, respectively. Results show that the diurnal variations of B0_new and B0_new_c_av are in a good agreement with those of B0_obs evidently compared with those of B0_IRI and B0_old at every station during the three seasons over high and middle latitudes. During the three seasons, the diurnal variations of B0_new_c_av show similar trends and are close to one another with the B0_obs and the B0_new with small deviations. The differences between the B0obs and the B0_new_c_av also show similar trends and are close to one another with those between the B0obs and the B0_new. In contrast, the B0_IRI with ABT-2009 option seems to predict the B0 values poorly during the three seasons at high latitudes and some seasons at midlatitudes. The proposed B0_new is useful for computing approximately the observed B0 and the ionogram-based total electron content (ITEC) of Digisonde, and the plasma scale height over midlatitudes and high latitudes.     

Robust fault-tolerant saturated control for spacecraft proximity operations with actuator saturation and faults

In this paper, the motion control problem of autonomous spacecraft rendezvous and docking with a tumbling target in the presence of unknown model parameters, external disturbances, actuator saturation and faults is investigated. Firstly, a nonlinear six degree-of-freedom dynamics model is established to describe the relative motion of the chaser spacecraft with respect to the tumbling target. Subsequently, a robust fault-tolerant saturated control strategy with no precise knowledge of model parameters and external disturbances is proposed by combining the sliding mode control technique with an adaptive methodology. Then, within the Lyapunov framework, it is proved that the designed robust fault-tolerant controller can guarantee the relative position and attitude errors converge into small regions containing the origin. Finally, numerical simulations are performed to demonstrate the effectiveness and robustness of the proposed control strategy.     

外弹道测量数据采集与处理技术

数据采集与处理技术是数据处理的关键。主要介绍外测事后数据处理过程中测量数据采集、异常数据识别、数据中奇异项剔除、数据丢点、重点检测方法、数据取齐、加密、压缩与采样时间校正、数据平滑滤波等关键技术,其对于研究数据处理新方法和提高数据处理精度,具有一定的参考价值。     

基于特征编码的飞机结构件工艺设计

为解决飞机结构件数控加工工艺决策效率低及自动化程度不高的问题,提出基于特征编码的飞机结构件工艺设计方法。首先,该方法借鉴成组技术,将飞机结构件加工元分类编码,形成特征编码表后,把通过特征识别得到的加工特征分解为加工元,与特征编码表匹配并排序得到加工方案。最后,在CATIA V5平台上开发了基于特征编码的飞机结构件工艺设计模块。     

基于直升机飞行性能需求的涡轴发动机设计参数选取方法研究

以直升机性能计算方法为基础,辅以考虑尺寸效应及设计能力的涡轴发动机设计方法,建立了以直升机旋翼桨盘载荷及最大起飞功重比为特征参数的直升机/涡轴发动机性能约束分析模型、任务分析模型及基于直升机飞行性能需求的涡轴发动机设计参数选取模型。针对涡轴发动机部件/系统设计能力及直升机飞行性能需求,首先开展了给定涡轴发动机循环参数下的流量匹配计算,然后开展了涡轴发动机循环参数选取研究。研究表明,所建立的直升机/涡轴发动机性能约束分析模型、任务分析模型可实现给定飞行任务的直升机/涡轴发动机性能耦合设计;在给定涡轴发动机循环参数条件,由于尺寸效应,涡轴发动机部件效率受进口流量的影响,其设计点功率并不随流量等比例变化,从而使得直升机起飞总重呈现非等比例变化;在涡轴发动机循环参数选择时,在满足直升机飞行性能需求下,存在涡轴发动机耗油率与单位功率之间权衡下的循环参数选取,使得直升机起飞总重最小。     

电参数对 7075铝合金微弧氧化膜硬度的影响

通过使用直流双脉冲电源对 7075铝合金进行微弧氧化试验,研究了正向电压、占空比和脉冲频率等电参数对铝合金微弧氧化膜层硬度的影响。通过正交试验,研究了单一水平因素下的膜层硬度平均值的变化规律,发现了通过电参数提升膜层硬度的方法;通过相对极差分析,发现正向电压对膜层影响程度最大,脉冲频率对膜层影响程度最小。提出了针对 7075铝合金微弧氧化膜硬度提升的电参数优化方案:提升氧化膜硬度,应优先考虑增大正向电压;保证氧化膜硬度的同时兼顾其他表面性能,应优先调整对膜层硬度影响最小的脉冲频率。     

Effects of geometrical parameters on wrinkling of thin-walled rectangular aluminum alloy wave-guide tubes in rotary-draw bending

Inner flange and side wrinkling often occur in rotary-draw bending process of rectangular aluminum alloy wave-guide tubes, and the distribution and magnitude of wrinkling is related to geometrical parameters of the tubes. In order to study the effects of geometrical parameters on wrinkling of rectangular wave-guide tubes, a 3D-FE model for rotary-draw bending processes of thin-walled rectangular aluminum alloy wave-guide tubes was built based on the platform of ABA-QUS/Explicit, and its reliability was validated by experiments. Simulation and analysis of the influence laws of geometrical parameters on the wave heights of inner flange and side wrinkling were then carried out. The results show that inner flange wrinkling is the main wrinkling way to rectan- gular wave-guide tubes in rotary-draw bending processes, but side wrinkling cannot be neglected because side wrinkling is 2/3 of inner flange wrinkling when b and h are smaller. Inner flange and side wrinkling increase with increasing b and h; the influence of b on side wrinkling is larger than that of h, while both b and h affect inner flange wrinkling greatly. Inner flange and side wrinkling decrease with increasing R/h; the influence of h on inner flange and side wrinkling is larger than that of R.     

1420 铝锂合金同种异种自冲铆单搭接头力学性能

为探究1420铝锂合金自冲铆接头的力学性能,本文采用自冲铆连接设备对1420铝锂合金(AL1420)同种及其与铜合金(H62)异种板材组合进行铆接,并通过拉伸-剪切试验测试接头的力学性能,运用SPSS数据分析软件对接头的最大载荷和最大位移量进行分析。结果表明:AL1420-AL1420和AL1420-H62两种接头的失效形式皆为铆钉从下板拉脱,铆钉头与上板接触区域出现不同程度撕裂;H62-AL1420接头除铆钉从下板拉脱,铆钉头与下板接触区域仅出现凹陷。AL1420-AL1420接头最大载荷最高(6 026.8 N),能量吸收性能最好(16.84 J)。对于异种板材组合,H62-AL1420接头的最大载荷(5 304.0 N)大于AL1420-H62接头(5 229.3 N),AL1420-H62接头的能量吸收值(16.79 J)大于H62-AL1420接头(15.08 J),异种板材铆接时则优先采用能量吸收性能较好的AL1420-H62搭接形式。     

加力燃烧室用气冷喷油杆结焦特性数值研究

为阐明实际工作环境参数下气冷喷油杆内燃油结焦速率与沉积厚度等特性,建立沿喷杆轴向的一维非稳态热-流-固耦合换热与燃油结焦计算模型,获得了喷杆壁面与燃油温度、结焦速率与相对结焦厚度等参数沿程分布。分析了燃油进口温度和质量流量对燃油结焦特性的影响,并与无气冷喷杆方案结果进行了对比。计算结果表明:燃油温度沿轴向逐渐升高,喷杆壁温在底端达到峰值。基准工况下气冷喷杆结焦速率和结焦厚度均沿轴向先升高后降低。结焦速率最大为26μg/(cm2·h),对应相对结焦沉积厚度0.6%。无气冷喷杆方案,在喷杆前端和底部各存在一结焦峰值区域。结焦速率峰值分别为398μg/(cm2·h)和807μg/(cm2·h),对应相对结焦沉积厚度8%和15%。固定燃油进口流量,随着燃油进口温度升高,结焦速率显著增大,喷杆内结焦总质量呈指数级增长趋势。固定燃油进口温度,进口流量越大,结焦速率略有增大,结焦总质量仅呈线性增长趋势。相较于无气冷喷杆,气冷喷杆可显著降低喷杆壁面与燃油温度,从而大幅抑制结焦生成。