Internal Flow Field Measurement of Gas Turbine Based on Optical Flow Method

The in-cylinder flow field of the internal combustion engine is an important factor affecting the quality and combustion quality of the fuel mixture in the cylinder. In order to calculate the high-precision flow field, the paper presents a flow field calculation method based on the optical flow algorithm. The motion of the point was calculated using the change in pixel intensity within two temporally adjacent frame images. The results show the high accuracy and resolution of the flow field at small displacement conditions.

Simultaneous estimation of aerosol optical constants and size distribution from angular light-scattering measurement signals

The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.

A New Method for Measurement of Local Solid Flux in Gas-Solid Two-phase Flow

Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.

RESEARCH ON OPTICAL METHOD OF MONITORING PHOTOCATHODE PROCESS

The principle of an optical method of photocathode processing control, which is one ofphotocathode processing monitoring techniques, is discussed. A designed monitoring apparatus is describedand has been applied to investigate the optical parameters of multialkali photoemitter during the process offabrication. Some actual schemes using the method to monitor the preparation of photocathodεs are sug-gested.

Methods Development for the Optical Determination of the Black Carbon Content of Loess Samples

We evaluate the applicability of an optical transmission measurement method commonly used for the analysis of the Black Carbon (BC) content of aerosol sample, to determine the BC content of loess sediments. A number of different sample pretreatment procedures are developed and compared, leading to an optimum preparation process. The results include: 1) Subtraction of the optical attenuation values before and after heating of the sample filters (“ΔATN”) varies linearly with the sample mass. The slope of the regression line provides the best determination of BC concentration. 2) When the sample mass is small, (NaPO3)6 pretreatment is best for BC measurement, and the BC concentration results are given by the slope of the regression between ΔATN and sample mass, for a series of samples of varying mass. 3) HF pretreatment accompanied by centrifugation and rinsing may produce a negative bias on the result. 4) Replicate measurements of BC for loess samples showed a maximum deviation less than 5.6%, suggesting that measurements of the BC concentration of a sequence of loess samples could determine variations to this degree of significance. 5) The overall trends of BC concentration in loess section sequences were similar for all chemical pretreatments. The BC concentration result for replicate samples is comparable when pretreated by the same procedure.

Optical measuring systems and technologies for some urgent tasks in industry and science

Modern industry and science take novel optical measuring systems and laser technologies with high resolution and productivity for solving actual tasks,including safety problems for mining,oil,atomic and railway in-dustries.The TDI SIE's results in these trends are presented.

Utilization of Extrinsic Fabry-Perot Interferometers with Spectral Interferometric Interrogation for Microdisplacement Measurement

The paper presents a number of signal processing approaches for the spectral interferometric interrogation of extrinsic Fabry-Perot interferometers(EFPIs). The analysis of attainable microdisplacement resolution is performed and the analytical equations describing the dependence of resolution on parameters of the interrogation setup are derived. The efficiency of the proposed signal processing approaches and the validity of analytical derivations are supported by experiments. The proposed approaches allow the interrogation of up to four multiplexed sensors with attained resolution between 30 pm and 80 pm, up to three times improvement of microdisplacement resolution of a single sensor by means of using the reference interferometer and noisecompensating approach, and ability to register signals with frequencies up to 1 kHz in the case of 1 Hz spectrum acquisition rate. The proposed approaches can be used for various applications, including biomedical, industrial inspection, and others, amongst the microdisplacement measurement.

磁光晶体式光纤电流传感器的设计及微电流测量

为了实现微弱电流的智能化实时监测,基于法拉第效应,利用磁光晶体作为传感元件制作光纤电流传感器,具有维尔德常数大、灵敏度高、体积小、便于集成等优势。通过琼斯矩阵推导并分析了磁光晶体式光纤电流传感器的解调机理,搭建了基于磁光晶体偏振型光纤电流传感器的微弱电流测量系统;在偏振分析技术的基础上,提出双光路自平衡差分测量的方法消除两光路损耗系数的不相等,得到了实际应用中偏振型光纤电流传感器的解调表达式,使灵敏度达到最高为7.15×10^(-4)rad/mA,微电流测量分辨率优于0.5mArms。

Retrieval of aerosol optical constants from angular light-scattering measurement signals using principal component analysis approach

An angular light-scattering measurement (ALSM) method combined with the probability density function-bmsed ant colony optimization algorithm (PDF-ACO) is proposed for retrieval of aerosol optical constants. An optimal measurement angle selection method using a principal component analysis (PCA) approach is developed to improve retrieval accuracy. Results indicate that optimized angle selection can ensure retrieval accuracy. The aerosol optical constants over Beijing, China, which are available from the Aerosol Robotic Network (AERONET), are then rec on structed. The ALSM method's con vergence properties are also studied via comparison w让h those of the light reflection-transmittance measurement (LRTM) method. Results retrieved using the ALSM method show better convergence speed and accuracy than those retrieved using the LRTM method because the ALSM method does not require solution of the radiative transfer equation and allows more useful signals to be obtained. Additionally, the inverse accuracy of the refractive index results is better than that of the absorption index results;this is attributed to differences between the monodromic characteristics of the refractive index and absorption index retrieval results. All results confirm that the combination of the ALSM method w让h the PDF-ACO algorithm and the optimal measurement angle selection method provides effective and reliable aerosol optical constant reconstructio n.

Absolute surface form measurement of flat optics based on oblique incidence method

In this Letter, a test method based on oblique incidence is practically implemented in the interferometric measurement process. Three sets of wavefront data are achieved through cavity interference measurement with a Fizeau interferometer and one oblique incidence measurement. An iterative algorithm is applied to retrieve the absolute surface shape of the test flat. By adding two sets of measurements, the absolute surface error of the interferometer＇s reference flat can be obtained. The new method can not only calibrate the reference flat error of interferometer, but also provide the absolute measurement method for high precision optical components applied in high power laser systems.

基于物理信息神经网络的金属表面吸收率测量方法

漫反射金属吸收率的准确测量十分重要且比较困难.量热法可靠性较高,但是参数反演较为困难.为此,建立了一种物理信息神经网络方法.该方法通过神经网络拟合温度上升段曲线,进而获得吸收率.为了验证该方法,开展了数值仿真和实验研究.数值仿真结果表明,该方法适用于吸收率测量,抗干扰能力强,反演精度高,在0.05—0.2的吸收率范围内,最大误差为0.00092.实验以喷砂镀金铝板为被测对象,受表面粗糙度、镀金工艺等影响,这些样品的吸收率处于2%—10%之间,测量重复精度优于1%.基于物理信息神经网络的吸收率测量方法有望成为一种有力的金属表面吸收率测量方法.

基于光学法的水下爆炸冲击波流场压强测量与分析

针对水下爆炸流场多参数测量,发展了基于OpenCV图像处理技术的光学法,对水下爆炸实验中冲击波超压进行测量并与理论和数值结果作对比。发现基于OpenCV图像处理技术的光学法能够较好地实现冲击波阵面的捕获与超压测量并实现冲击波传播过程、爆轰产物发展等流场信息的获取,可为光学法在水下爆炸实验中的应用提供借鉴参考。

基于实体GIS设备试验的局部放电光学信号传播特性研究

光测法具有电磁免疫性,特别适用于具有封闭结构的气体绝缘开关设备(gas insulated switchgear, GIS)局部放电检测,但是光信号在传播过程中易因传播距离增加或部件遮挡而快速衰减。为此,基于110 kV实际GIS设备开展局部放电光学信号传播特性试验,研究传播距离和绝缘子遮挡对导杆尖刺缺陷和悬浮电位缺陷局部放电光信号的影响规律。结果表明,随着传播距离的增加:尖刺缺陷检测到光信号最大幅值和放电数均有所衰减,放电谱图变化不大;悬浮缺陷放电光信号幅值明显衰减,放电数不变,放电谱图特征逐渐失去“矩形”特征。此外,当光学信号透过带有通气孔的绝缘子传播时,光学信号明显衰减,且幅值波动较大。

基于等效最小光程的大范围浊度测量方法

浊度测量在水质监测等领域有重要应用。针对大范围浊度测量问题,提出了一种基于等效最小光程的浊度测量方法。利用90°散射法,通过多组光程与散射光强测量值进行线性拟合,计算出光强截距,建立了光强截距与待测浊度的数学关系。该光强截距表征最小光程条件下的等效散射光强,从而减小了高浊度下光程的影响,保证了低浊度和高浊度区间的高测量精度。搭建了13路光程组合的浊度测量实验装置,实验结果表明,在250~2000 NTU的范围内,该方法最大相对误差为2.818%,与散射法直接测量相比,平均相对误差降低约71%,在保证测量精度的前提下扩展了散射法的测量范围。

地质力学模型实验中变形量测方法的应用研究

地质力学模型实验作为一种便捷高效、成本低廉的研究方法,不仅可以将工程的破坏过程直观地呈现出来,而且可以作为了解工程整体力学特征、破坏模式和稳定情况的重要研究手段,在各类岩土工程问题的研究中有着广泛应用。由于地质力学模型材料的变形模量较低,同等应力条件下应变极其敏感,因此模型实验中变形测量显得至关重要。为了提升地质力学模型实验中变形量测的便捷性和准确性,对目前地质力学模型中变形测量的主要方法进行总结分析。结果表明:目前对于模型变形量测的方法主要分为电测式测量方法、光学测量方法和机械式测量方法,其中电测式测量方法主要包括电阻式应变片法和位移计法,光学测量方法主要包括光纤类传感器法、数字图像相关法、光弹性贴片法和云纹干涉法,机械式测量方法主要包括百分表测量法和经纬仪观测法。通过对各种方法工作原理、主要应用案例及优缺点的阐述对比,得出不同方法的主要区别是测量范围和适用范围的差异,其中百分表测量法适用于测量小区域变形;测量内部变形可选择电阻式应变片法及光纤类传感器法;较大区域的变形可选择位移计法及光纤类传感器法;指定点位移可选择经纬仪观测法;全场观测可选择数字图像相关法、云纹干涉法以及光弹性贴片法。该成果可为相关地质力学模型实验的变形测量提供实验参考。

基于线结构光的牵伸罗拉工作面圆跳动测量方法

针对牵伸罗拉工作面圆跳动的人工测量精度不稳定、效率低等问题,课题组提出了基于线结构光的牵伸机罗拉工作面圆跳动测量方法。通过线结构光获取牵伸罗拉工作面的条纹图像,在条纹图像预处理的基础上采用Steger算法提取条纹图像的中线点云数据;建立基于点云的牵伸罗拉工作面圆跳动测量模型;通过构建虚拟平面,得到牵伸罗拉的圆跳动值。实验结果表明:课题组所提出测量方法的绝对误差在0.01 mm之内,小于传统测量方法的绝对误差,提高了测量精度。

基于量热法的高功率激光功率测试技术

针对高功率激光功率的测试,尤其是高功率激光器烤机时的长时间测量需求,设计了基于水冷却的激光功率测量方法。利用热敏电阻测量冷却水进水口和出水口的温差计算激光功率。利用有限元仿真软件建立了吸收腔热路结构的三维有限元模型,并对不同口径的冷却水路进行模拟仿真。测试结果表明,用该方法测试高功率激光功率,测量相对误差可以保证在1.6%以内。

基于光流像素匹配的扫描显微相位测量轮廓术

在扫描相位测量轮廓术中,需要先将不同位置的物体匹配到同一点,再根据相移算法提取相位信息,而像素匹配精度与相移算法均会影响测量精度。为此,采用显微系统,根据其远心光路特性实现物体移动量与像素移动量的等量转换;通过交替采集白场图像和条纹图像,由白场图像通过光流法实现精确的像素匹配,再根据物体匀速运动特点实现条纹图像的精确像素匹配;根据初始条纹周期选择基本符合满周期的N幅条纹图,由任意步数相移方法计算出截断相位分布,再通过概率密度函数搜索最佳条纹周期,进而得到准确的相位信息,完成物体形貌测量。实验表明,所提方法有效提高了测量精度,相移算法也适用于任意N(N≥3)幅图,在模拟工业流水线场景中物体的三维测量时,RMSE(均方根误差)可达0.008 mm左右。

基于趋势外推法的分布式光纤测温系统的温度预测

分布式测温传感器被广泛运用于温度监测。本文以此为背景,提出了一种具有温度监测和温度预测功能的分布式光纤系统。在实现温度监测的同时,建立了一种基于机器学习的趋势外推模型,通过不断更新的历史数据来预测未来温度。实验模拟了一般火灾的温度变化并进行预测。结果表明,当采样时间为5 s,预测1 min后的温度时,预测误差最大值为2.88℃,均方误差为0.958℃,说明模型准确度较高,对工程实践具有一定的参考价值。

几何量检测中非接触式测量技术的应用研究

随着我国机械零件精密度的逐步提高,对机械制造中的几何量检测工作提出了更高要求。通过对非接触式测量技术的运用,不仅可以提高测量精度,还能减少安全隐患的发生。基于此,本文重点分析激光测距法、视觉测量法、结构光法、光学干涉法、工业CT法等非接触式测量技术的应用,并对其技术进行分析与展望。旨在充分发挥非接触式测量技术的优点,不断提高其技术水准,助力几何量检测工作的顺利开展。