变厚度涡轮盘上能量与应力分布的关联分析

提出一种分段解析法,推导给定变厚度涡轮盘内外缘加热能量下涡轮盘的温度分布与应力分布,从而建立起以能量转移系数表示的涡轮盘能量分布与温度分布及应力分布之间的直接关联.该关联应用于某型航空发动机低压涡轮盘,并通过与数值模拟对比,结果显示:温度与应力的理论分析结果与数值模拟结果吻合较好,最大相对偏差分别为2%与13%;等边界热流量条件下,随着能量转移系数的增大,涡轮盘内缘温度增大,外缘温度减小,涡轮盘等效应力水平降低,最大等效应力减小.分段解析法获得的能量分布与应力分布关联的准确性与可行性得到了验证.      

风扇/压气机叶型厚度对颤振特性的影响

采用计算流体力学与结构动力学相结合的方法,数值模拟了三维振荡叶栅非定常黏性流场;通过对叶片表面非定常气动力及其所做非定常气动功的计算分析,采用能量法对叶片颤振与否进行预估判断。针对三维直叶片和风扇转子叶片,通过调整叶片的相对厚度,研究了叶片厚度变化对风扇/压气机颤振特性的影响。此外,通过对振荡叶栅非定常流场结构的研究,发现了叶片吸力面气流分离与叶片振动之间的耦合关系。本文的研究在风扇/压气机设计中,可用于评估最大相对厚度等叶型结构设计参数对气弹稳定性的影响,对叶轮机颤振机理研究具有一定的参考意义。     

离心力场下多孔层的不同厚度对热驱动换热的影响

以涡轮叶片新型超级冷却技术的研究为背景,在具有冷却通道的新型冷却结构中加入多孔介质,采用实验与数值模拟相结合的方法研究了不同多孔层厚度条件下,新型冷却结构的热驱动换热规律,实验和计算结果基本一致.研究结果表明不同多孔层厚度条件下,该新型冷却结构具有相同的换热规律:随着旋转速度、热流密度和冷气进口速度的增大,该结构的热驱动换热能力逐渐增强.同时实验研究发现,随着多孔层厚度的增大,热驱动换热效果降低.      

CMP加工过程中加工载荷对液膜厚度的影响分析

本文采用激光诱导荧光技术(LIF)来研究抛光参数对化学机械抛光加工区液膜厚度的影响.研究表明,抛光液膜厚度随着抛光载荷的增加而减少,减小的趋势随抛光载荷的提高而减缓.同时液膜厚度随着抛光速度的增加而变大.通过抛光参数的变化对抛光液液膜厚度影响的分析,为改善CMP加工工艺提供理论性的依据.     

热障涂层厚度及厚度不均热无损检测的数值模拟

研究了热障涂层(TBC)厚度及厚度不均的红外热无损检测(IRTNDT)的建模和基于有限单元法的数值模拟。在柱坐标系下以轴对称模型描述热障涂层结构的瞬态热传导,建立相应的物理模型及有限元模型。用有限元分析软件ANSYS计算涂层结构受热脉冲激励后的温度场,研究热无损检测可检信息参数(如最大温差和最大对比度)与厚度特征参数(厚度差和厚度)的关系。结果表明,在涂层公称厚度一定时,最大温差和最大对比度与厚度差呈非线性关系,它们随着厚度差的增大而增大;在涂层厚度差一定时,最大温差和最大对比度与涂层公称厚度呈非线性关系,它们随着涂层公称厚度的增加而减小。利用计算所得的可检信息参数与厚度特征参数的关系可以反向估计陶瓷层厚度差和厚度。这些研究结果为热障涂层厚度及厚度不均的红外热无损检测及表征提供了基本理论依据。     

Validation of University of New Brunswick Ionospheric Modeling Technique with ionosonde TEC estimation over South Africa

For more than a decade, ionospheric research over South Africa has been carried out using data from ionosondes geographically located at Madimbo (28.38°S, 30.88°E), Grahamstown (33.32°S, 26.50°E), and Louisvale (28.51°S, 21.24°E). The objective has been modelling the bottomside ionospheric characteristics using neural networks. The use of Global Navigation Satellite System (GNSS) data is described as a new technique to monitor the dynamics and variations of the ionosphere over South Africa, with possible future application in high frequency radio communication. For this task, the University of New Brunswick Ionospheric Modelling Technique (UNB-IMT) was applied to compute midday (10:00 UT) GNSS-derived total electron content (GTEC). GTEC values were computed using GNSS data for stations located near ionosondes for the years 2002 and 2005 near solar maximum and minimum, respectively. The GTEC was compared with the midday ionosonde-derived TEC (ITEC) measurements to validate the UNB-IMT results. It was found that the variation trends of GTEC and ITEC over all stations are in good agreement and show a pronounced seasonal variation for the period near solar maximum, with maximum values (∼80 TECU) around autumn and spring equinoxes, and minimum values (∼22 TECU) around winter and summer. Furthermore, the residual ΔTEC = GTEC − ITEC was computed. It was evident that ΔTEC, which is believed to correspond to plasmaspheric electron content, showed a pronounced seasonal variation with maximum values (∼20 TECU) around equinoxes and minimum (∼5 TECU) around winter near solar maximum. The equivalent ionospheric and total slab thicknesses were also computed and comprehensively discussed. The results verified the use of UNB-IMT as one of the tools for future ionospheric TEC research over South Africa.     

An inversion approach for lunar regolith layer thickness using optical albedo data and microwave emission simulation

An approach to inversion of the lunar regolith layer thickness by using multi-channel brightness temperature observation in passive microwave remote sensing is developed. To first make simulation of brightness temperature from the lunar layered media, the lunar regolith layer thickness (d) is proposed being constructed by available lunar DEM (digital elevation mapping) and on site measurements. The physical temperature distribution (T) over the lunar surface is also empirically assumed as a monotonic function of the latitude. Optical albedo of the lunar nearside from the telescopic observation is employed to construct the spatial distribution of the FeO+TiO₂ content (S) in the lunar regolith layer. A statistic relationship between the DEM and S of the lunar nearside is further extended to construction of S of the lunar farside. Thus, the dielectric permittivity (ε) of global lunar regolith layer can then be determined. Based on all these conditions (d,T,ε), brightness temperature of the lunar regolith layer in passive microwave remote sensing, which is planned for China's Chang-E lunar project, is numerically simulated by a parallel layering model using the strong fluctuation theory of random media.Then, taking these simulations with random noise as observations, an inversion method of the lunar regolith layer thickness is developed by using three- or two-channels brightness temperatures. When the S is low, and the four channels brightness temperatures in China's Chang-E project are well distinguishable, the regolith layer thickness and physical temperature of the underlying lunar rock media can be inverted by the three-channels approach. When the S becomes high that the brightness temperature at high frequency channels such as 19.35, 37 GHz are saturated, the regolith layer thickness is alternatively inverted only by the two-channels approach.Numerical simulation and inversion approach in this paper make an evaluation of the performance for lunar passive microwave remote sensing, and for future data calibration and validation.     

变截面梁式压电智能板振动控制的小波模式

基于 Daubechies小波理论的尺度函数变换 ,对于变截面悬臂板结构的弯曲建立了由压电片感应器的观测电量识别挠曲变形构形的显式关系式。此基础上 ,采用具有位移与速度信号负反馈控制律后 ,建立了抑制振动的压电动力控制程序。由于小波尺度函数逼近具有低带通性质 ,即具有自动滤除高频分量的能力 ,该控制程序将不会出现由观测溢出与控制溢出耦合而造成的控制失稳 (即在抑制低频 (阶 )扰动时系统激发出高频 (阶 )扰动的现象 )。数值仿真结果表明 :该控制方法所能控制的模态阶数与压电片数相同 ,而且其控制程序在抑制外界干扰方面是有效的。     

民用飞机短舱复合材料结构雷电直接效应试验验证方法及漆层厚度影响研究

随着飞机设计的发展,复合材料广泛应用于民用飞机短舱结构。由于碳纤维复合材料结构的导电性以及抗雷电损伤能力比铝合金结构差,复合材料短舱结构雷电防护能力已成为影响飞机飞行安全的一项关键问题。依据相关适航条款和相应的国际标准,阐述了民用飞机短舱复合材料雷电防护试验验证方法,并依据验证方法对漆层厚度的损伤影响进行了试验研究。短舱常规蒙皮构型的复合材料试验件,在不同漆层厚度下的雷电防护试验结果表明,漆层较薄时,漆层对短舱复合材料的雷电直接效应防护能力无明显的影响;当漆层厚度达到一定厚度时,较厚的漆层将显著降低短舱复合材料的雷电直接效应防护能力,最严重时将造成复合材料蒙皮的击穿,损伤蒙皮内部系统设备,从而危害飞行安全。试验结果与理论的机理分析具有良好的一致性,对民用飞机短舱复合材料结构的雷电防护设计提供了指导方向和参考意义。     

基于瞬态尾迹模型的直升机旋翼旋转噪声计算

针对旋翼噪声时域方式求解的特点,本文在能考虑厚度影响的桨叶升力面气动模型的基础上,建立了一个随时间推进的瞬时自由尾迹模型,在该模型中,为提高桨叶载荷计算的准确性,计入了翼型的非定常气动力影响、桨叶的挥舞运动和旋翼的气动力平衡。利用建立的自由尾迹模型,结合Farassat的时域噪声预测理论,构建了一个旋翼旋转噪声预测方法。利用该方法首先计算了模型旋翼在前飞时的载荷和声压时间历程,通过与试验数据的对比,验证了方法的有效性,然后基于本文建立的噪声预测方法,计算了悬停和前飞状态直升机旋翼的厚度噪声、载荷噪声及总旋转噪声的声压时间历程和频谱特性。