无塌陷型面出流及输送管内推进剂利用技术研究

针对火箭通用芯级氧箱的共底贮箱结构，通过理论分析及数值仿真，提出了“无塌陷型面+消漩叶片”的出流方案，并通过优化型面起始点半径，确保出流过程中不产生明显的液面塌陷。仿真及缩比试验结果表明，相比传统的“圆盘+倒锥”出流方案，贮箱推进剂在无塌陷型面出流方案下的出流过程中，没有明显的气液掺混或漩涡夹气现象，贮箱内推进剂可得到充分利用。在此基础上，利用Wallis两相漂移模型对输送管内两相介质传播速度进行了理论研究，并结合出流过程中气泡运动速度的试验结果，提出了输送管内推进剂的可用量准则。     

车用液冷机壳电机定子绕组热性能直接设计法

电动汽车驱动电机极力追求高密度轻量小型化,不断推进电机的冷却散热与热传导技术的进步与发展。为此,开展车用驱动电机的电-磁-热一体化设计方法研究,通过构建一种工程化定子热路模型提出了定子绕组热性能直接设计法及其关键热参数,并直接融入电磁设计中,强化热性能设计的同时也弥补了传统电磁设计热负荷AJ值评估热性能的缺陷。通过快速评估电机的热传导能力和绕组温升,可评估比较不同设计方案的热性能,得到电-磁-热一体化设计的最佳解决方案,从而提升电机持续运行的输出转矩。采用定子绕组热性能直接设计法,改进设计了一台液冷机壳车用永磁同步驱动电机样机,显著降低了定子绕组温升。样机温升试验验证了定子绕组热性能直接设计法及其关键热参数评估热性能的有效性。     

北斗星基增强系统双频多星座服务覆盖范围评估

双频多星座（DFMC）服务已成为星基增强系统（SBAS）未来能力提升的重要方向之一，相关国际标准也将在2023年11月正式发布。北斗星基增强系统（BDSBAS）是全球范围内唯一持续播发DFMC增强服务测试信号的星基增强系统。在详细介绍SBAS DFMC服务可用性和保护级计算方法的基础上，利用实测的BDSBAS B2a增强电文对BDSBAS DFMC增强服务的一类垂向引导进近（APV-I）/垂向导航信标性能（LPV）和决断高度200英尺垂向导航信标性能（LPV-200）等级的服务覆盖率进行了初步评估。评估结果表明，当前BDSBAS DFMC增强服务能够实现对中国及周边广大区域的服务覆盖，且双系统（BeiDou navigation satellite system和global positioning system，BDS+GPS）增强服务的APV-I和LPV-200等级99%可用性覆盖率比单系统（BDS）增强服务的覆盖率分别提升16%和32%。     

一种可靠性增长试验抽样数Max-Min准则的反馈修正方法

对成败型航空发动机部件可靠性增长试验抽样数的确定问题进行了研究。推导出了初始故障数服从典型离散分布时的最小化最大准则(Max-Min准则),提出了一种逐次抽样样本估计值反馈修正方法。最后给出了一个应用实例,验证了该方法的有效性。     

Transfer learning: A new aerodynamic force identification network based on adaptive EMD and soft thresholding in hypersonic wind tunnel

The aerodynamic test in the pulse combustion wind tunnel is very important for the design, evaluation and optimization of aerodynamic characteristics of the hypersonic aircraft. The test accuracy even affects the success or failure of hypersonic aircraft development. In the aerodynamic test of pulse combustion wind tunnel, the aerodynamic signal is disturbed by the inertial force signal, which seriously affects the test accuracy of aerodynamic force. Aiming at the above problems, this paper innovatively proposes an aerodynamic intelligent identification method, that is the transfer learning network based on adaptive Empirical Modal Decomposition (EMD) and Soft Thresholding (TLN-AE&ST). Compared with the existing aerodynamic intelligent identification model based on deep learning technology, this study introduces the transfer learning idea into the aerodynamic intelligent identification model for the first time. The TLN-AE&ST effectively alleviates the problem of scarcity of training samples for intelligent models due to the high cost of wind tunnel tests, and provides a new idea for further implementation of deep learning technology in the field of wind tunnel aerodynamic testing. And this study designed residual attention block with soft threshold and dense block with adaptive EMD in TLN-AE&ST model. Residual attention block with soft threshold module can more effectively suppress the influence of instrument noise signal on model training effect. Dense block with adaptive EMD makes the deep learning model no longer a black box to a certain extent, and has certain physical significance. Finally, a series of wind tunnel tests were carried out in the Φ = 2.4 m pulse combustion wind tunnel of China Aerodynamic Research and Development Center to verify the effectiveness of TLN-AE&ST.     

Modelling and analysis of metal flowing behaviors in constraining ring rolling of tapered ring with thin wall and three high ribs

Tapered ring with thin wall and three high ribs(TRTWTHR), showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm), is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin, rocket body and fuel tank because of light weight and high carrying capacity. How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve. In this work, constraining ring rolling(CRR) techn...     

高马赫数V字形钝化前缘平板表面压力特性

针对三维内转式进气道V字形唇口下游面临的严酷压力载荷问题，将唇口简化为V字形钝化前缘平板，在来流马赫数为6的条件下，采用数值模拟结合激波风洞压敏涂料测量方法，研究了半径比R/r = 0 ~ 20（V字形根部倒圆半径R与前缘钝化半径r之比）的平板表面压力演化特性。结果表明，随着R/r增大，V字形钝化前缘产生的三维波系结构发生变化，引起下游平板表面压力演变出4种类型。R/r较小时，V字形钝化前缘激波干扰产生的大范围流动分离，诱导形成了偏离中心线较远的分叉状高压区（Type Ⅰ，分叉型）；随着R/r增大，流动分离减弱，分叉状高压区逐渐消失，由透射激波扫掠壁面所形成的条带状高压和超声速射流对撞所形成的中心线高压区逐渐显露，依次出现过渡型（Type Ⅱ）、严酷型（Type Ⅲ）和渐匀型（Type Ⅳ）压力分布。平板上分叉型和过渡型的压力最大值仅为4.3 ~ 7.2p∞（p∞为来流静压），但V字形钝化前缘处的流场品质恶劣；严酷型的压力最大值，随着射流对撞强度的增强而增大，最高可达19p∞；渐匀型的压力最大值，随着射流对撞强度的减弱，逐渐趋近于二维钝前缘平板产生的压力最大值4p∞。