激光干涉法在扭摆法测量微冲量中的应用

介绍了激光干涉法测微小转角的原理及测量方法,提出了采用激光干涉测量微冲量的方法,将激光与靶作用产生的微冲量转化为扭摆的转动角度,通过激光干涉法测量此微小转角从而计算出冲量。相同单脉冲能量下,以PVC+2%C为工质,用扭摆法测量了激光与工质作用产生的微冲量,结果表明该测试系统分辨率为2×10-8N.s,量程为2×10-7～0.8×10-5N.s。     

翼型动态失速DBD等离子体流动控制的数值模拟研究

进行了翼型深度动态失速及基于DBD介质阻挡放电等离子体激励器的流动控制技术数值模拟研究。将激励器对流动空气的作用以彻体力源项形式加入N-S方程。通过数值求解此N-S方程,研究了DBD激励器对NACA0012翼型俯仰运动深度动态失速的控制作用;研究了DBD激励器工作方式对动态失速平均气动力、气动力迟滞曲线的影响,提出了控制效果较好的激励器工作方式。     

TA15钛合金薄板等离子弧对接焊缝疲劳特性研究

为了探索钛合金等离子弧焊接头的疲劳性能,本文依据TA15标准试件和轧制板材试件疲劳试验数据处理结果,采用当量应力集中系数法,在TA15薄板等离子弧焊和对接焊缝磨削组合工艺试件的疲劳试验基础上,确定了中值当量应力集中系数和安全当量应力集中系数,最后建立了该TA15薄板的S-N曲线,给出了应用结论。     

Total electron content variations in equatorial anomaly region

Diurnal variations in the total electron content (TEC) at Makerere University (00°19′N, 32°40′E, Geo Dip −22°), Uganda, have been investigated using a NovAtel GSV400B GPS receiver for the year 2010. The highest TEC values occurred from 13h00 to 17h00 local time (LT) throughout the year, with the highest values being exhibited during equinoctial months. In addition, there was some correlation between this high TEC and the moderate storms that occurred in 2010. These high TEC values have been attributed to the solar EUV ionization coupled with the upward vertical ExB drift. Nighttime enhancements were also found to be seasonally dependant, attaining maximum values during equinoctial months. These results were also compared with modeled TEC values by the IRI-2007 model. The modeled values were in good agreement with the measured values except for these two points: (1) the model had a short-fall in predicting the nighttime enhancements; and (2) the model’s minimum TEC did not coincide with the measured minimum in most of the months. Observed TEC depletions were found to correlate with an increase in the S₄ index and have been identified as a manifestation of the plasma density depletions of the equatorial origin.     

基于小波神经网络的直升机主减速器故障诊断系统

应用离散小波变换(DWT)和神经网络相结合构建直升机主减速器速器故障诊断系统: DWT对振动信号进行特征提取,神经网络对故障进行辨识和分类。阐述了DWT、帕塞瓦尔定理和广义回归神经网络(GRNN)基本理论,提出了直升机主减速器的故障诊断系统流程图,最后用某型直升机飞行时主减速器上的振动数据对该系统进行验证。实验使用了BPNN(back-propagation neural network)和GRNN两种神经网络,结果表明:提出的故障诊断系统能对主减速器故障进行较好的辨识和分类,这将为直升机主减速器故障诊断系统的进一步开发提供新的技术参考。      

Experimental Investigation of the Effects of Various Plasma Actuator Configurations on Lift and Drag Coefficients of a Circular Cylinder Including the Effects of Electrodes

In this paper, the effects of the existence of plasma actuator electrodes and also various configurations of the actuator for controlling the flow field around a circular cylinder are experimentally investigated. The cylinder is made of PVC (Polyvinyl Chloride) and considered as a dielectric barrier. Two electrodes are flush-mounted on the surface of the cylinder and are connected to a DC high voltage power supply for generation of electrical discharge. Pressure distribution results show that the existence of the electrodes and also the plasma are able to change the pressure distribution around the cylinder and consequently the lift and drag coefficients. It is found that the effect of the existence of the electrodes is comparable with the effect of plasma actuator in controlling the flow field around the cylinder and this effect is not reported by other researchers. Eventually it is concluded that the existence of the electrodes or any extra objects on the cylinder and also the existence of the plasma are capable of changing the flow field structure around the cylinder so that the behavior of the lift and drag coefficients of the cylinder will be changed significantly.     

新型等离子体电扫描八木天线的关键技术研究

提出了一种新型等离子体电扫描八木天线,研究了基于等离子体的电扫描八木天线的关键技术。通过对等离子体半波振子的仿真,研究了等离子体半波振子天线的辐射性能、隐身性能和等离子体对电磁波的反射和吸收作用。通过实验测试了等离子体中电子密度,制作了一款等离子体电扫描八木天线原理样机．并进行了测试。     

朗缪尔探针在轨快速除污染技术研究

讨论了一种朗缪尔球形探针在轨快速去除表面污染的技术方法. 朗缪尔探针是空间等离子体原位探测的一项重要手段, 广泛应用于各种航天器. 探针传感器表面被污染时, 会造成探针I-V特性曲线失真, 从而导致探测获得的等离子体参数产生偏差. 通过试验验证了采用探针传感器加载高压的技术, 其可快速有效清除传感器表面污染, 确保朗缪尔探针在轨探测获得实时、准确的空间等离子体信息.      

钡钨空心阴极放电等离子体特性实验研究

空心阴极作为电推力器的核心部件之一,其放电等离子体特性对空心阴极的性能和可靠性具有决定性的作用。采用实验的方法,使用朗谬尔静电探针置于钡钨空心阴极放电出口处,诊断和分析了钡钨空心阴极出口处的放电等离子体特性随阴极推进剂流量和放电电流的变化规律,结果表明:阴极推进剂流量和放电电流对空心阴极放电等离子体特性具有比较明显的影响,各等离子体参量随阴极推进剂流量和放电电流均有明显的变化,其中,电子数密度随阴极推进剂流量和放电电流的增大而上升,等离子体电势随阴极推进剂流量和放电电流的增大而下降,电子温度随阴极推进剂流量的增加而下降,随放电电流的增大有略微升高,而且,放电电流对放电等离子体特性具有更显著的影响。     

等离子体合成射流对钝头激波的控制与减阻

为了验证等离子体合成射流对超声速流动的流动控制和减阻效果,在考虑热完全气体效应的情况下,工程拟合等离子体热力学属性和输运系数,利用能量源项模型对超声速平板和球头等典型流场结构进行了数值模拟,并取得了与实验较为一致的结果。研究结果表明：对于马赫数为2的超声速平板流动,等离子体合成射流能有效干扰边界层的发展,并诱导产生一系列大尺度结构;对于马赫数为3的球头流场,等离子体合成射流能显著改变激波脱体距离与球头的阻力特性;在放电后第1个周期内,合成射流能使球头平均阻力降低6.3%,而在射流峰值情况下使阻力降低32.0%,激波脱体距离增加2倍,实现了激波控制和流动减阻的预期效果。