非接触式叶片振测系统的叶尖定时传感器的研究

介绍了一种新型的叶尖定时传感器 ,传感器采用Y型耦合光纤与自聚焦透镜相结合 ,实现聚光照明及叶尖散射光的高效收集 ,大大提高了检测灵敏度。光源采用 4 5mW的半导体激光器 ,光电接收元件采用雪崩式光电二极管。传感器具有体积小、结构简单、成本低、安装和调节方便、测量精度高等优点。实验表明 ,该传感器对信号有良好的接收能力 ,满足涡轮机叶片高速、实时检测的要求 ,能为后续处理电路提供稳定而可靠的信号     

磁电式脉冲传感器原理与叶尖定时误差分析

基于叶尖定时测振原理,分析了磁电式脉冲传感器工作原理。结合传感器外形,通过计算推导,得出了影响叶尖定时精度的因素。并且通过理论仿真和实验对相关波形进行了比较。为磁电式脉冲传感器的设计,提高叶尖定时精度提供了理论基础。     

叶片叶尖间隙测量的光纤传感器

根据叶尖间隙测量的要求,设计了一种新型的光纤传感器。它采用了单光纤传光、多组光纤束接收散射光的结构。发射光纤位于中心,周围均布多组接收光纤。通过各组接收光纤光强的比值运算,消除了叶尖表面反射率变化对测量结果的影响,也可减小叶尖表面与传感器端面夹角给测量结果带来的影响。在转速同步传感器的配合下,该传感器可以实时测量所有叶片的叶尖间隙。当叶片转速在0—12000r／min之间变化时,叶尖间隙的测量范围为0-3mm,测量精度为25μm。     

叶尖定时旋转叶片实时振动测量技术

设计了一套基于叶尖定时传感的旋转叶片振动测量系统。系统主要由光电传感系统、数据采集与预处理系统、叶片振动数据处理系统三部分组成。叶尖定时传感器采用单根光纤发射、多光纤接收的 Y 型结构,并用高性能专用集成芯片完成弱光信号的放大检测,使传感器信噪比大于500,信号带宽大于 50MHz。利用 CPLD 和 DSP 技术,实现了叶尖定时信号的高速实时采集与处理;建立了同步共振条件下叶片振动的数据处理模型,实现了叶片振动的实时监测。整套测量系统在现场某大型压气机上进行了原理性验证,在转速高达 9210rpm的情况下测得的同步共振最大幅值为 0.4231mm,接近于同等条件下国外的测量结果,从而验证了整套测量系统的可靠性。     

基于叶尖定时法的旋转叶片振动监测技术研究与应用进展

自叶尖定时法提出以来,其众多突出的优点使其成为当前旋转叶片在线监测领域中的研究热点。在现有文献的基础上,首先对叶尖定时测量方法的基本原理进行简述,总结近几年国内外在该领域取得的成果和研究现状;然后,介绍几种基于叶尖定时法的传感器和叶片振动参数辨识的新方法,并对其进行分析和比较。最后,提出该领域未来研究的方向和难点。     

基于叶尖定时技术的叶轮叶片动态监测研究现状

叶轮作为旋转机械的核心部件之一,在复杂恶劣的工况中容易使叶片产生振动,进而引发疲劳断裂等失效形式,因此对叶片振动进行状态监测具有重要意义。非接触式的叶尖定时技术具有同时监测整级叶片的优势,为叶片振动及损伤诊断提供了有效方式。本文从叶尖定时传感、叶片振动及损伤监测等三个方面对国内外研究现状进行综述,总结了当前研究中存在的不足,并就叶尖定时技术及叶片健康监测的发展方向进行了展望。     

蓝宝石光纤与光纤高温传感器

蓝宝石光纤作为一种高品质的单晶光纤,具有极好的高温稳定性和光学、机械特性,因此在光纤高温传感和中红外激光传能方面具有相当重要的应用价值。 浙江大学物理系光纤电子材料研究室单晶光纤及应用研究课题组。于1987年在国内首次拉制成功蓝宝石单晶光纤和YAG单晶光纤,并经过多年努力,在蓝宝石光纤高温传感头及光纤测温仪的实用化研究中,取得了较好的研究结果。目前已建立起稳定的晶体光纤激光加热基座法(LHPG)生长设备;能小批量生长优质的蓝宝石单晶光纤材料,光纤光传输损耗优于     

无转速同步叶尖定时预处理方法及误差分析

提出了一种无转速同步叶尖定时信号预处理方法,通过同一叶片到达不同叶尖定时传感器的振动位移差进行振动参数辨识和转速测量。误差分析表明,该方法可以降低转速测量误差以及转速误差对振动位移测量的影响。分析了振动位移差的测量误差,并与采用转速同步的方法进行了比较。实验结果表明,该方法能够有效地实现叶尖定时测量并具有良好的测量精度。     

光子晶体光纤F-P干涉式高温传感器研究

本文提出一种用于高温测量的光子晶体光纤F-P干涉传感器,通过熔接机放电使无截止单模光子晶体光纤(ESM-PCF)一个端面完全塌陷,然后再将其与单模光纤(SMF-28e)熔接起来,最后按照设计长度切断ESM-PCF。由于在熔接点处ESM-PCF完全塌陷使其模场直径扩大,减小了与SMF-28e的模场失配损耗,并提高了熔接面的反射光强。这种方式制作简单,相对于以往的光子晶体光纤F-P干涉传感器具有更高的干涉光强度。实验结果表明,该传感器测量温度可达1100℃,温度灵敏度为29.4nm/℃,可以预见这种结构稳定、线性度好的全光纤传感器在机械、航空、冶金领域等具有一定的潜在应用价值。     

基于叶尖定时的旋转叶片同步振动辨识新方法

为掌握旋转叶片在不同工作转速下的振动特性,利用叶尖定时测振系统对旋转叶片进行振动测试。分析了基于变速扫频测量的速矢端迹法理论,设计了一种多传感器辨识叶片同步振动的新方法。运用该方法对某型号航空设备的旋转叶片进行振动测量实验,准确地辨识出不同转速下旋转叶片的振动倍频、动频、振幅及阻尼系数等参数。频率和振幅辨识重复性精度分别高达0.0072Hz和5.7um。正确绘制出叶片振动坎贝尔图,实验辨识结果与叶片理论设计结果基本一致。     

An optical fiber sensor for remote pH sensing and imaging

A fiber-optical probe for pH sensing and real-time imaging is successfully fabricated by connecting a polymer imaging fiber and a gradient index (GRIN) lens rod which was modified with a sensing film. By employing an improved metallographic microscope, an optical system is designed to cooperate with the probe. This novel technique has high-quality imaging capabilities for observing remote samples while measuring pH. The linear range of the probe is pH 1.2-3.5. This technique overcomes the difficulty that high-quality images cannot be obtained when directly using conventional imaging bundles for pH sensing and imaging. As preliminary applications, the corrosion behavior of an iron screw and the reaction process of rust were investigated in buffer solutions of pH 2.0 and 2.9, respectively. The experiment demonstrated that the pH values of the analytes' surface were higher than that of buffer solutions due to the chemical reaction. It provides great potential for applications in optical multifunctional detection, especially in chemical sensing and biosensing.     

Micromachined optical fiber current sensor

We describe a micromachined optical fiber current sensor. The sensing element consists of a squared silicon membrane (8 mm long and 20 mum thick) that has a cylindrical permanent magnet (NdFeB alloy, 3-mm diameter, 1.5 mm high) fixed on its central region. This structure allows the permanent magnet to vibrate in the presence of the magnetic field gradient generated by an ac. A linear relation between the electrical current and the magnet displacement was measured with white-light interferometry with an optical fiber low-finesse Fabry-Perot microcavity. A measurement range of 0-70 A and a minimum detectable intensity of 20 mA were obtained when distance D between the membrane and the electrical power line was 5 mm. The output signal directly shows a linear response with distance D.     

A dual modality optical fiber sensor

We propose and demonstrate a fibre optic system based on bi-tapered silica fibre that can simultaneously measure strain and fibre curvature. Both modalities on the signal can be extracted with no measurable crosstalk between them. The experimental signal has a pure phase modulation when strain is applied to the tapered fibre optic section of the sensor and the signal shows only intensity modulation when an un-tapered fibre section is bent. High sensitivity is achieved from the experimental results for strain and bending losses and the estimation of measurement errors is 0.2 and 0.1%, respectively. This system offers low-cost, compactness and it can be adapted for structural health monitoring.     

An optical fiber radiation sensor for remote detection of radiological materials

This paper demonstrates the feasibility of a portable radiation sensor system that uses the pulsed optically stimulated luminescence technique to remotely interrogate an aluminum oxide (Al/sub 2/O/sub 3/:C) radiation sensor via an optical fiber. The objective is to develop a system for applications requiring simple and inexpensive sensors for widespread monitoring of ionizing radiation levels, which can be remotely interrogated at regular periods with little or no human intervention and are easy to install, operate, and maintain. Results on the optimization and performance of the system are presented. The current minimum detectable dose is of the order of 5 /spl mu/Gy, which is already satisfactory for applications such as the monitoring of radioactive plumes from radioactive waste sites. We also discuss potential developments that could decrease the minimum detectable dose to allow radiation doses as low as the background level to be measured over short time intervals, making the system more versatile for detecting radiological materials.     

A reflectometric optical fiber temperature sensor

A reflectometric fiber-optic temperature sensor was manufactured and characterized. The sensing probe is obtained by replacing the cladding with a temperature sensitive liquid on a short length of fiber. Its reduced dimensions make it suitable for monitoring applications whenever a high spatial resolution is required. A numerical modeling of the sensor, based on a ray-tracing technique, was carried out. The metrological performance of the first prototype seems to be very interesting in terms of accuracy and, above all, response time. A system for multipoint temperature measurements is also described.     

Fiber-Bragg-grating force sensor based on a wavelength-switching actively mode-locked erbium-doped fiber laser

A fiber-Bragg-grating (FBG) transverse-force sensor based on a wavelength-switching actively mode-locked erbium-doped fiber laser is proposed, in which a FBG is used as both the sensing element and the wavelength-selection element of the laser. When a force is applied to the FBG, the induced birefringence in the FBG causes the laser to emit pulses at two close wavelengths, whose separation is proportional to the applied force. To suppress the interference between the two wavelengths, the laser is made to emit at the two wavelengths alternately by use of a polarization-switching technique. The wavelength separation is converted into a time difference by transmission of the laser pulses through a dispersive single-mode fiber, so the wavelength measurement is replaced by the less-expensive time measurement. The output of the sensor is insensitive to temperature and axial strain changes along the FBG. To interrogate similar FBG sensing elements connected in series it is necessary only to change the modulating frequency of an electro-optic modulator to select the corresponding laser cavity. The practicability of this approach was demonstrated experimentally with two multiplexed sensing elements.     

Extrinsic Fabry-Perot cavity optical fiber liquid-level sensor

An optical fiber liquid-level sensor based on an extrinsic Fabry-Perot (FP) cavity is proposed and demonstrated. The FP cavity consists of the end of the single-mode optical fiber and the elastic silicon layer. Liquid pressures act on the mechanical construction to change the cavity length, resulting in differential phase shifts that may be observed as variations of the output signal intensity. Self-compensated steps have been taken to obtain high accuracy and long-term stability in realistic circumstances. Experimental results indicate that accuracy of 2 mm over a full scale of 3.5 m (water) is obtained under ambient temperature 10-38 degrees C. The sensor can be used to measure liquid levels continuously and accurately in explosive and flammable environments.     

An optical fiber chemical sensor for mercury ions based on a porphyrin dimer

The synthesis of a novel fluoroionophore, 5-p-[[4-(10',15',20'-triphenyl-5'-porphinato) phenyloxyl]-1-butyloxyl]phenyl-10,15,20-triphenylporphine (DTPP), and its application for preparation of a Hg(II)-sensitive optical fiber chemical sensor are described. The response of the sensor is based on the fluorescence quenching of DTPP by coordination with Hg(II). The porphyrin dimer-based sensor shows a linear response toward Hg(II) in the concentration range 5.2 x 10(-7)-3.1 x 10(-4) mol x L(-1), with a working pH range from 2.4 to 8.0. The sensor shows excellent selectivity for Hg(II) over transition metal cations including Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Zn(II), and Fe(III). As a sensing agent, the porphyrin dimer shows obviously better fluorescence response characteristics toward Hg(II) compared to porphyrin monomer or metalloporphyrin. The effect of the composition of the sensor membrane was studied, and the experimental conditions were optimized. The sensor has been used for determination of Hg(II) in water samples.     

荧光光纤传感器测量系统实现

光纤是20世纪的重要发明之一，它与激光器、半导体探测器等一起构成了新的光学技术。本文阐述了作为现代测量技术中利用荧光光纤传感器进行测量的技术，并着重介绍了荧光光纤传感器测量系统的结构、功能及实际的应用。     

调频连续波激光干涉光纤温度传感器

本文提出了一种调频连续波激光干涉非本征型法珀腔光纤温度传感器。使用具有较高热膨胀系数的不锈钢圆管封装法珀腔制成温度传感探头。不锈钢圆管作为法珀腔腔体的同时也是温度敏感元件。通过调频连续波干涉测量技术测量法珀腔因受热膨胀所产生的腔长变化量,实现对温度的传感。实验结果表明,该光纤温度传感器测温分辨率达到了0.0002 ℃,温度测量灵敏度可达3022 nm/℃。此温度传感器不仅具有较高的灵敏度与分辨率,且结构简单稳定,具有良好的应用前景。