Improving accuracy of damage quantification based on two-level consistency control of PZT layers

Structural health monitoring-based quantitative damage diagnosis technique plays a key role in real-time condition monitoring. Among the current research, piezoelectric (PZT) sensor and Guided Wave (GW) based damage quantification methods are promising, which normally establish a calibration model between GW feature and damage degree by experiments on batch specimens, and then conduct the calibration model on the monitored specimen. However, the accuracy of PZT and GW based damage quantification is affected by dispersion introduced by sensor network performance, structural material, and damage propagation among the adopted batch specimens. For improving the accuracy of damage quantification, this paper adopts PZT layer as sensor network and creatively implements theoretical and experimental research on batch PZT layers consistency control. On one hand, a two-level consistency control method based on multidimensional features-Euclidean distance is proposed to ensure the performance consistency of PZT layers placed on different specimens. On the other hand, experimental research on typical aircraft lug structures is also carried out to evaluate the requirement on performance consistency of PZT layers when performing quantitative damage diagnosis, and further verify the proposed two-level consistency control method. Experimental results show that the accuracy of damage quantification raises by 38% when the dispersion of different PZT layers is controlled within 5%.     

运输类飞机翼身组合体参数化及快速气动力计算研究

飞机方案设计阶段,迫切需要一个能够快速评估、计算不同参数组合的翼身组合体基本气动力特性的分析平台。为满足这一实际工程设计需要,本文提出运输类飞机参数化概念和具体研究方法,结合运输机气动布局设计的基本准则,应用计算机图形学进行辅助设计,利用丰富的参数曲线,如NURBS曲线、贝塞尔曲线、拉格朗日插值等方法描述复杂的翼身组合体外形,开发了快速分析计算翼身组合体气动力特性分析平台,实现了从总体方案初步设计到MGAERO软件数值模拟的无缝过渡,并结合具体算例验证了方法的可行性和工程实用价值。     

可压缩湍流边界层壁面函数方法综述

以建立工程实用的高超声速湍流边界层模拟方法为目标,从湍流壁面函数是湍流边界层方程近似解的角度,梳理了相关文献的研究工作,得到如下认识:1)壁面函数与所求定解问题数值解的相容程度决定了壁面第一层网格允许放粗的程度,在流动分离点和再附点附近区域,目前壁面函数尚需进一步完善,而"子网格"壁面函数从理论上解决了相容性问题,尽管...     

高温热环境下EPDM绝热材料炭层表面相态试验

为了解EPDM绝热材料烧蚀过程中炭化层表面相态,以及在热态环境下炭化层的抗冲击结构特点,设计了一种表面碰撞试验装置.利用设计的试验装置,在含铝5％的复合推进剂燃气环境中,对一种EPDM绝热材料进行了炭化层表面相态探测试验,清晰地获得了撞击后的炭化层表面形貌.试验结果分析表明:在本研究条件下,EPDM绝热材料炭层表面基本...     

基于P3HT空穴传输层的碳基无机CsPbIBr2钙钛矿太阳电池

钙钛矿太阳电池是近年来快速兴起的第三代太阳电池,其中热稳定性优异、成本低、带隙超过2.0 eV的CsPbIBr_2无机钙钛矿太阳电池效率已经突破11%,应用前景广阔。目前,大部分研究都集中在无空穴传输层的碳基CsPbIBr_2钙钛矿太阳电池,较低的开路电压和填充因子是限制效率提升的主要原因。本文将溶液法制备的3-己基聚噻吩(P3HT)空穴传输层应用于CsPbIBr_2钙钛矿太阳电池,提高了内建电势,改善了载流子输运,减少了载流子复合,实现了电池开路电压、填充因子的改善和能量转换效率的提升,丰富了CsPbIBr_2钙钛矿太阳电池的载流子输运机理和效率提升途径,具有一定的推广意义。     

有机—无机层合玻璃的热应力分析

分析了膨胀系数相差一个数量级的两种透明材料的非对称层合结构在均匀变温下的热应力分布以及应力与材料参数、几何尺寸的关系。推导了含软胶夹层梁的热应力表达式。为无机与有机玻璃的复合结构作为飞机风挡的可行性分析提供理论基础。     

建筑物附近气流特征及湍流扩散的模拟试验

用非静力、能量闭合的大气边界层模式对建筑物附近的气流和湍流特征进行了模拟,为了检验模拟结果,将风场和湍流场输入到扩散模式获得了建筑物附近腔区和尾流区内的污染物浓度分布。结果与同样条件下的风洞测试的结果吻合。本文研究结果表明,在来流风速增大的情况下,建筑物下游的尾流区范围变化不大,而腔区范围增大,湍流运动增强。本文所用方法比采用拟合经验公式描述尾流、腔区的特征更能反映不同建筑物、不同来流的影响。     

近壁区理论耗散率模型的改进

提出了在边界层的近壁区,采用共振三波的理论模型描述湍流边界层相干结构,由此解决了对称三维波理论模型不能处理三阶相关量的问题,根据新的理论模型对ε方程逐项进行计算和分析.与原理论模型计算结果相比,本文理论结果与直接数值模拟(DNS)符合更好.     

A new stationary droplet evaporation model and its validation

The liquid droplet evaporation character is important for not only combustion chamber design process but also high-accuracy spray combustion simulation.In this paper,the suspended droplets' evaporation character was measured in a quiescent high-temperature environment by micro high-speed camera system.The gasoline and kerosene experimental results are consistent with the reference data.Methanol,common kerosene and aviation kerosene droplet evaporation characteristics,as well as their evaporation rate changing with temperature,were obtained.The evaporation rate experimental data were compared with the prediction result of Ranz-Marshall boiling temperature model (RMB),Ranz-Marshall low-temperature model (RML),drift flux model (DFM),mass analogy model (MAM),and stagnant film model (SFM).The disparity between the experimental data and the model prediction results was mainly caused by the neglect of the nat ural convection effect,which was never introduced into the droplet evaporation concept.A new droplet evaporation model with consideration of natural convection buoyancy force effect was proposed in this paper.Under the experimental conditions in this paper,the calculation results of the new droplet evaporation model were agreed with the experimental data for kerosene,methanol and other fuels,with less than 20％ relative deviations.The relative deviations between the new evaporation model predictions for kerosene and the experimental data from the references were within 10％.     

蛇形进气道地面工作状态附面层抽吸试验研究

对一种蛇形进气道开展了地面工作状态下的抽吸试验研究,结果表明,在该状态下进气道出口截面的总压恢复系数较低、流场畸变较大。为此,本文采用附面层抽吸技术对其进行了地面抽吸状态下的流场控制试验研究。研究结果表明:(1)地面工作状态下,随着出口马赫数的增加,蛇形进气道出口截面的总压恢复系数不断下降,而稳态周向畸变指数、紊流度和综合畸变指数均上升,稳态径向畸变指数变化不大。本研究的蛇形进气道在出口马赫数为0.45时,总压恢复系数为0.90,综合畸变指数为13.85%,总压恢复较低,畸变较大,超出了一般航空发动机的承受范围。(2)与原型方案的地面抽吸试验结果相比,采用附面层抽吸技术后,进气道出口截面的总压恢复系数得到了提高。在出口马赫数为0.45,相对抽吸量为0.043时总压恢复系数提高了2.6%。