共查询到18条相似文献,搜索用时 218 毫秒
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微型柔性热敏传感器阵列应用研究 总被引:1,自引:0,他引:1
边界层分离点检测是实现分离流主动控制的前提和基础,也是气动控制灵巧蒙皮系统研究的重点和难点。以流体边界层分离点检测技术为研究对象,以流体边界层分离点判定的风洞实验为验证目标,设计制作微型热敏传感器与聚酰亚胺柔性衬底,并首次利用微装配技术集成分立敏感元件与柔性衬底形成热敏传感器阵列。首先,采用分立元件通过表面贴装工艺来实现柔性微型热膜传感器阵列的集成,并研究该传感器阵列中敏感元件、柔性衬底的设计及传感器的排布。然后,在低速风洞实验中对传感器阵列的性能和传感器阵列输出信号采用统计量算法的方式进行处理判断,判定圆柱翼型的流体分离点位置。最后,对实验的结果所作的分析表明,该微型柔性热敏传感器阵列满足流体分离检测系统实时性、动态性的要求。 相似文献
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微型剪应力传感器以尺寸小、时空分辨率高的特点在边界层分离点测量中表现出了突出的优势。通过分析用于检测流体参数的微型热敏剪应力传感器的工作原理,设计了柔性热敏剪应力传感器阵列和恒流驱动电路。使用DAQPCI6024E及LabVIEW软件完成数据采集与实时信号处理,并提出采用均值变化量判断分离点的位置。风洞试验结果表明:该方法可行有效,可精确确定边界层分离点的位置。 相似文献
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低速流体边界层分离检测试验 总被引:1,自引:0,他引:1
结合边界层分离点附近的切应力变化规律,对边界层分离特性进行研究,确定边界层分离点的判定依据.采用分立元件通过表面贴装工艺来实现柔性微型热膜传感器阵列的集成,并研究该传感器阵列中敏感元件、柔性衬底的设计及传感器的排布,解决柔性传感器阵列对微细加工工艺要求较高的难题.根据边界层分离点判定依据,在低速风洞试验中对传感器阵列的性能和传感器阵列输出信号采用统计量算法和傅里叶变换功率谱算法进行处理判断,并与计算流体力学仿真结果对比,结果表明制造的微型热敏传感器阵列能够实现对流体边界层分离位置的在线测量. 相似文献
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微型热敏剪应力传感器在航空航天等领域有重要应用价值,然而基于热敏感原理的间接剪应力测量会引入流体环境温度的影响.结合热敏剪应力传感嚣的热交换模型,研究了流体环境温度变化的影响机理.分析了常用温度修正方法的应用局限性,设计了结合流体温度、从信号处理角度修正传感器输出的温度补偿方法,没有增加电路复杂程度,显著提高了测量精度.测试实验表明:当流体环境温度在10~20℃范围变化时,温度造成的输出信号偏移误差从原来的2%/℃降低到了0.5%/℃,证明了该方法的有效性. 相似文献
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An experimental study was conducted in order to investigate unsteady boundary layers for a pitching airfoil. An NACA0012 airfoil
sinusoid-pitched at quarter chord was employed, and its mean angle-of-attack and oscillation amplitude were 0° and 6°, respectively.
To explore the unsteady boundary layers, smoke-wire visualization and surface-mounted probe measurements were pursued for
three different cases, varying with Reynolds numbers (Rec=2.3×104, 3.3×104, and 4.8×104). A reduced frequency of 0.1 was identically set in all cases. Results show that in the presented Reynolds number range,
the separation bubble dependent on both angle-of-attack and Reynolds number was observed, accompanied with unsteady laminar
separation after reattachment. The unsteady laminar separation occurred at the saddle point, which was formed by the two vortices,
the wall, and the external flow, and it was independent of reverse flow. This result indicates that the unsteady laminar separation
occurs during the process of transition after the reattachment of separated boundary layer for an unsteady flow. The reverse
flow observed over the trailing edge significantly interacted with the trailing edge vortex that rotates in the streamwise
direction. This trailing edge vortex prevents the uppermost of the reverse flow from reaching to the unsteady laminar separation
point during the upstroke, and this induces that the boundary layer breakdown does not occur in spite of the occurrence of
laminar separation. The discrete vortices are formed by unsteady laminar separation, and its formation is ultimately affected
by the Reynolds number. Consequently, it is obvious that the unsteady boundary layers are ultimately sensitive to Reynolds
number in a low Reynolds number regime. 相似文献
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分析惯导用精密离心机动平衡测试系统的测试信号;分别研究静不平衡与偶不平衡作用下转子的回转中心,分析静不平衡与偶不平衡的输出信号,求得静不平衡与偶不平衡,对干脆步平衡及偶不平衡分别在双校正面上进行了分离。解决由于测试点不在转子的支承处,所测得的振幅无法直接应用于静偶不平衡分离的力方程和力矩方程中的问题。 相似文献
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浊点萃取(Cloud Point Extraction,CPE),是基于非离子型表面活性剂溶液的浊点现象和胶束增溶效应而建立的一种萃取技术。大部分金属螯合物具有微溶于水的特性,与表面活性剂的疏水基团结合,富集于小体积的富胶束相内,亲水性物质仍留在水相中。再经两相分离,即可实现样品中的目标化合物的分离和富集。浊点萃取法的优点:避免使用对人体有害的挥发性有机溶剂,不污染环境,安全;试剂消耗少,经济;减少萃取时间,快速高效;操作比较简便;对各种分析物具有高的萃取效率,富集倍数大;易于与仪器分析方法联用等。浊点萃取是分离和富集痕量金属离子的有效方法,是一种有发展前途的环境友好的分离富集技术。 相似文献
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This paper deals with the experiment to obtain quantitative information about conditions of the interface between a water
drop and surrounding oil. Velocity distributions in very close region of the interface are measured by introducing a new illumination
technique and a telecentric lens. It enables precise measurements of velocity distributions in the close region to the interface.
Although the measured velocity distributions exhibit strong influence from the solid wall of an experimental tube, the coincidence
of inner and outside velocities on the interface is clearly confirmed for the clean interface. The shearing stresses on the
interface, which are proportional to the velocity gradient normal to the interface, clearly show conditions of contaminated
interface, which can be divided into two parts. From front stagnation point to somewhere near a separation point, the distribution
of shearing stresses is well coincide with that of the Hadamard’s analytical solution, while the distribution on the latter
part of the interface shows quite different feature, which is supposed to be strongly influenced by contamination of the surface. 相似文献
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针对压电自感知执行器电学物理模型,分析了现有的提取结构振动信号方法存在的问题,改进了一维最小二乘均方自适应补偿系统的设计,提出了利用二维最小二乘均方自适应算法实现压电自感知执行器传感与激励信号间的动平衡分离,设计了基于TMS320LF2407DSP的二维最小二乘均方自适应信号分离系统,实现了对压电自感知执行器输出信号大小、相位的二维补偿,并从理论上进行了收敛性证明。实验结果证实,基于二维最小二乘均方自适应算法可真正实现压电自感知执行器传感与激励信号完全的、不失真的理想分离。 相似文献
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煤矸高效分选是实现煤炭资源绿色开采的重要手段,其核心技术是煤和矸石的快速精准识别。 因此,本文提出了基于
X 射线图像和激光点云融合的煤矸识别方法。 首先,设计了基于局部熵和全局均差加权的改进 Otsu 分割算法,以此提高 X 射
线图像的分割精度和分割效率;同时,利用直通滤波和体素栅格降采样简化了煤矸激光点云数据,进而提取了 X 射线图像和激
光点云的煤矸组合特征。 然后,针对传统麻雀搜索算法( SSA)易陷入局部最优和种群多样性差等问题,提出了多策略改进的
SSA 算法(ISSA),并用于轻量梯度提升机(LightGBM)参数的寻优,进而设计了基于 ISSA-LightGBM 的煤矸快速识别模型。 最
后,搭建了煤矸识别实验平台,开展了相应的实验对比分析,结果表明:ISSA-LightGBM 模型的煤矸识别准确达 99. 00% ,综合性
能优于其它模型,满足了煤矸高效识别的需求。 相似文献
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Natural habitats are created and developed through pool-riffle sequences in rivers, while vegetation cover could play a critical role in the sediment transfer and its quantity and quality. In this study, the effect of vegetation cover on the flow structure in a pool-riffle sequence is investigated in a laboratory flume under bed formation to compare with non-vegetated cover. In this context, instantaneous point velocities were measured by ADV to determine averaged velocity, shear velocity, root mean square velocity, friction factor, Reynolds shear stress and turbulence intensities. Results showed that the vegetation cover increases the thickness of the wall law. Meanwhile, the length of the flow separation zone in the vegetated bedform is more than in the non-vegetated bedform. Variation in roughness coefficients may cause a new boundary layer in which local flow velocities decrease. In both cases (vegetated and non-vegetated bedforms), the momentum is mostly transferred by ejection and sweep phenomena between flow and bedform. 相似文献