利用小孔射流改善气膜冷却效率的数值研究

为了获得气膜孔下游放置一对射流小孔对气膜冷却效率的影响规律,采用数值模拟方法研究了不同吹风比下射流小孔出口位置尺寸不同时流动过程和冷却效率的分布情况,并与常规气膜孔冷却结构形式进行对比,以揭示小孔射流改善气膜冷却效率的作用机理.研究表明:在常规气膜孔下游开两个射流小孔后,两射流小孔分别产生一个较弱的与气膜孔反向涡对方向相反的反向涡对,反向涡对的相互作用减弱了气膜孔反向涡对的强度,使气膜的贴壁效果更好,提高了气膜孔的冷却效率.在各吹风比条件下,气膜孔下游有射流小孔时,冷却效率都有一定的提高,并且射流小孔间距较大时对两气膜孔中心线之间的横向平均冷却效率改善较大,吹风比较大时,效果更明显.      

扩展型面排孔气膜冷却的实验

设计了三种型面的气膜孔扩展结构,研究了气膜冷却效率、壁面换热系数及流量系数随吹风比的变化规律.研究结果表明,与典型的圆柱形气膜孔相比,有后向扩展型面的气膜孔具有相对较高的冷却效率和换热系数,流量系数略有降低.扩展型面的流向扩展角对冷却效率和换热系数的影响大于侧向扩展角的影响.侧向扩展角只在特定吹风比下才对提高气膜的侧向覆盖率、进而提高气膜冷却效率起作用,它使得位于二次流出流下游的低压区域范围增大,流量系数减小.      

Improvement on shaped-hole film cooling effectiveness by integrating upstream sand-dune-shaped ramps

A numerical investigation and experimental validation is performed to address deeper insights into the combined effect of shaped holes and Sand-Dune-shaped upstream Ramp (SDR) on enhancing the film cooling effectiveness, under a wide blowing ratio range (M = 0.25–1.5). Three kinds of holes (Cylindrical Hole (CH), Fan-Shaped Hole (FSH), and Crater-Shaped Hole (CSH)) are taken into consideration. The SDR shows an inherent affecting mechanism on the mutual interaction of jet-in-crossflow. It aggravates the lateral spreading of cooling jet and thus improves the film cooling uniformity significantly, regardless of film-hole shape and blowing ratio. When the blowing ratio is beyond 1.0, the combined effect of shaped holes and SDR on improving film cooling effectiveness behaves more significantly. It is suggested that FSH-SDR is a most favorable film cooling scheme. For FSH-SDR case, the spatially-averaged film cooling effectiveness is increased monotonously with the increase of blowing ratio, among the present bowing ratio range.     

基于深度学习光流法的荧光油膜全局速度测量

针对基于先验的传统光流法存在前提条件苛刻的问题，提出使用基于深度学习的光流法进行荧光油膜全局速度测量。采用数值仿真试验对基于先验的改进HS光流法和基于深度学习的FlowNet2光流法进行对比，结果显示：在不外加干扰时，改进HS光流法和FlowNet2光流法的平均端点误差分别为0.458 7像素/s和0.381 7像素/s；在亮度变化、噪声干扰或不同的演化时间下，FlowNet2光流法的平均端点误差均明显低于改进HS光流法，平均端点误差差值最大可达5.19像素/s；风洞试验进一步证明，FlowNet2光流法能够获得正确、清晰、定量的荧光油膜全局速度场，较改进HS光流法鲁棒性更高，对风洞工程应用具有一定的参考价值。     

轴承钢等离子体基离子注碳复合改性层化学结构的研究

通过激光Ｒａｍａｎ光谱、Ｘ射线光电子谱以及电阻和显微硬度的测试，研究了ＧＣｒ１５钢及镀钛ＧＣｒ１５钢试样经乙等离子基离子注入所得表面改性层的化学结构。     

真空100 keV质子辐照对石墨膜热性能的影响

研究了25 μm石墨膜在能量100 keV最大注量2.5×10¹⁵ p/cm²的真空质子辐照条件下的微观结构和热性能，采用拉曼光谱（Raman spectrum）、X射线衍射（XRD）、X射线光电子能谱（XPS）进行微观结构分析，采用激光闪射法（LFA）进行热性能分析。石墨膜晶面间距为0.335 83 nm，石墨化度为95.0%。结果发现，质子辐照会导致石墨膜表层产生缺陷，片层间距增大，石墨化度降低，氧含量升高；随着质子辐照注量的增加，Raman光谱中D和G峰的积分面积比表明缺陷密度不断增加。25 μm石墨膜经过能量为100 keV注量为2.5×10¹⁵ p/cm²质子辐照后，石墨膜热扩散系数无明显变化。     

湿式摩擦离合器挤压过程及接合特性分析

针对湿式摩擦离合器接合过程中的挤压机理及微凸体接触问题，综合考虑摩擦片表面油槽结构，材料渗透性等因素，根据修正雷诺方程和K-E（Kogut-Etsion）接触模型，对湿式摩擦离合器的挤压过程中的动压承载力、微凸体承载力以及转矩转速变化等建模分析，并采用有限差分法对修正雷诺方程求解，对挤压过程中的油膜压缩速度、油膜厚度变化率和片间承载力等挤压特性和转速、转矩等接合特性展开了仿真分析。并采用SAE#2试验机进行了相关试验获得了转速、转矩、压力、摩擦因数等数据，与仿真分析进行了对比。结果表明：湿式摩擦离合器接合过程可分为3个阶段，通常会在1 s内完成，在0.02 s左右开始从挤压阶段经压紧阶段在0.03 s左右过渡到全微凸体接触阶段，试验与理论分析结果一致。     

Frequency reconfigurable antenna actuated by inflated triangular structure: Design and analysis

This paper proposes a frequency reconfigurable triangular antenna actuated by an inflated triangular structure. The open path antenna is transformed from an open type to a closed structure by inflating. Inflatable structures are easy to manufacture by fusing 2 inextensible membranes together along a defined pattern of lines. However, the prediction of their deployed shape remains a challenge. To solve the pattern changed problem, guided by geometric analyses and local buckle characteristics, the inflated triangular structure has been designed and verified by experiment and simulation. In the process of transformation of the antenna, the resonant frequency of the antenna is changed because this frequency is determined by the conformational change. The resonant frequency changes from GHz to kHz when the design of initial structure sizes is from millimeter to meter. The measured peak gains, the frequency, and the radiation direction are also reconfigurable by the initial size. Finally, the reconfigurable resonator array is presented, which is coupled to electric fields to absorb all incident radiation. In this work, the changed pattern design by inflating is applied to the antenna design, and its frequency reconfigurability is achieved. Through the electricity performance analysis of the reconfigurable antenna, precise manufacturing will be possible and provide guidance for manufacturing frequency reconfigurable antennas.     

Parylene C薄膜微波电路的应用可行性研究

针对三防材料在微波电路中多余物防控方面的可行性、可靠性问题,提出在产品表面用真空化学气相沉积法镀Parylene C薄膜,结果表明该膜层可有效控制直径d小于1 mm的可动多余物,提高微波产品PIND(颗粒碰撞粒子检测)测试的合格率.同时与焊接、胶粘、互联、清洗等配装工艺有良好的适配性,且满足可靠性要求.该薄膜较高的绝缘...     

航空发动机涡轮叶片接触式测温技术应用进展

航空发动机涡轮叶片测温技术能够揭示涡轮叶片的温度分布情况，对其开展性能评估、失效分析和优化设计具有重要意义。涡轮进口温度的不断提升对应用于航空发动机涡轮叶片的测温技术提出了更高的要求。现有的航空发动机涡轮叶片接触式测温技术可采集叶片表面温度和近表面气流温度，本文主要介绍了三种应用于涡轮叶片的接触式测温技术，包括薄膜热电偶、测温晶体和示温漆，简要说明了三种测温技术的工作原理，归纳了国内外应用现状，总结了各自的优势与不足，并对其发展方向进行了展望。