基于CCD后向散射激光信号的PM2.5测量研究

根据米散射理论和激光传播方程,建立PM 2.5颗粒物浓度与后向散射光强的关系模型,并提出了基于电荷耦合器件(CCD)后向散射激光雷达的实时PM 2.5颗粒物浓度的监测方法。设计了以532 nm波长的激光器为光源、CCD为接收器的后向散射激光雷达实验装置。根据获得的实时大气颗粒物后向散射图像,提取灰度值矩阵并分析了散射图像的光强分布;对比赛默飞世尔科技公司的PM 2.5监测仪(SHARP)的实验结果,拟合了PM 2.5颗粒物浓度与散射光强的5个关系式,拟合度均在0.95以上。这种成本较低、操作便利的实时PM 2.5颗粒物浓度监测装置的推广,有助于建立PM 2.5污染物的分布和运动模型并绘制污染地图,具有重要意义。     

大气颗粒物近前向光散射特性研究EI北大核心CSCD

为了考察大气颗粒物近前向光散射特性及其在粉尘质量浓度测量中的应用,建立了大气颗粒物近前向散射光测量实验装置,通过单分散和多分散颗粒物样本的实验测量和基于米散射理论的颗粒物光散射计算,得到颗粒物近前向散射光强度与粒径及分布宽度的关系,结果表明该装置可用于测量环境大气气溶胶质量浓度。通过已知参数的单分散气溶胶样品测量,借助米散射理论计算,可以获得较为准确的响应度数值,并估计测量实际大气颗粒物的误差范围。采用亚利桑那超细标准粉尘进行质量浓度定标,测量城区自然环境颗粒物的粉尘质量浓度,需要约2.5倍的修正。     

大气颗粒物近前向光散射特性研究

为了考察大气颗粒物近前向光散射特性及其在粉尘质量浓度测量中的应用,建立了大气颗粒物近前向散射光测量实验装置,通过单分散和多分散颗粒物样本的实验测量和基于米散射理论的颗粒物光散射计算,得到颗粒物近前向散射光强度与粒径及分布宽度的关系,结果表明该装置可用于测量环境大气气溶胶质量浓度。通过已知参数的单分散气溶胶样品测量,借助米散射理论计算,可以获得较为准确的响应度数值,并估计测量实际大气颗粒物的误差范围。采用亚利桑那超细标准粉尘进行质量浓度定标,测量城区自然环境颗粒物的粉尘质量浓度,需要约2.5倍的修正。     

非球形烟尘粒子后向散射场的光谱分析

在利用后向散射法测量烟尘浓度和粒径的过程中,对烟尘粒子模型的后向散射光谱特性进了计算,确定影响后向散射光谱强度的主要因素并进行分析。对实际排放的烟尘进行显微观察表明,利用椭球、圆柱和广义切比雪夫3种非球模型可以较好地模拟烟尘粒子,其等效直径约1μm。通过"T矩阵法"对这3种非球形粒子模型后向散射场的光谱特性进行了分析,结果表明:非球形粒子的可见/红外波段后向散射现象较球形粒子明显,特别是广义切比雪夫粒子的后向散射光强最高可达到前向的3.5倍;对于吸收性非球形粒子(复折射率m=1.57-0.56i),后向散射光强远大于非吸收性非球形粒子(复折射率m=1.57-0.001i);随着粒子等效半径的增大,光源波长也应随之增加。这为在实际测量时光源及方位的选择提供了理论依据。     

排放源颗粒物浓度及粒径连续监测技术的研究

１前言我国实施了“主要污染物排放总量控制”的环境控制战略，把污染排放总量逐级下达到每一个排放源。为此，亟需解决排放源颗粒物浓度的测量技术。取样法（ＳａｍＰｌｉｎｇ）不能连续测量，测量周期也长，操作繁杂，劳动强度大，使得对排放源的复检率很低，测量误差也较高【‘］。浊度法（ＯＰａｃｉｔｙ）及近期发展的杂散光法（ＳｔｒａｙＬｉｇｈｔ）【’］，虽易于实现连续测量，但其测量结果为浊度或散射光强，烟尘浓度值则需通过标定的方法才能得到。实际上，浊度和散射光强不仅与烟尘的浓度相关，还要受到烟尘颗粒的粒径及折射率…     

基于CCD侧向散射激光雷达的PM2.5浓度测量研究

基于侧向散射激光雷达方程和Mie散射理论,建立了PM2.5浓度与侧向散射光强的关系模型,提出了一种基于电荷耦合器件(CCD)实时监测近地面PM2.5浓度的方法。设计了以波长532nm激光器为光源、CCD为接收器的侧向散射激光雷达装置,利用该装置测量了散射角在15°~45°之间的侧向散射回波信号图,从回波信号图提取灰度值矩阵并分析其光强分布。与赛默飞世尔科技公司PM2.5监测仪(SHARP)提供的测量结果对比,拟合了PM2.5浓度与3个灰度等级光总能量的关系式,拟合度均在0.97以上。该装置具有操作便利、移动便捷、监测实时、成本较低的特点,在近地面比后向散射激光雷达具有更高的精度与实用性,有助于建立PM2.5污染物的分布和运动模型并绘制污染地图。     

气溶胶激光散射信号的特征分析

本文应用Mie散射理论对微球体粒子光散射的性质进行了理论分析与数值计算,得出了散射光分布与微球体尺度参数、复折射率之间的关系。结果表明:不同尺度参数的粒子的散射光强的分布相差极大,随着尺度参数的增加散射光强越来越集中于前向;复折射率的变化对散射光强影响不大。并且在边界层大陆乡村型霾的气溶胶模型下对大气气溶胶的体角散射系数进行了分析与数值计算,得出:气溶胶粒子的散射光强主要分布在前向,并且随着散射角的增加有规律的减小。由此提出了利用气溶胶粒子体散射系数的性质,通过测量散射点前向散射光强和延迟时间来实现激光束的近轴定位的方法。     

神光Ⅲ原型全孔径背向散射测量系统研制及应用

为了测量激光与等离子体相互作用产生的散射光份额,获得黑腔耦合效率实验中的激光注入率,研制了基于神光Ⅲ原型装置的全孔径背向散射测量系统。该系统利用聚焦透镜收集散射光,通过离轴抛物面镜进行缩束,并采用二向色镜将散射光分为两个支路后分别进行受激布里渊散射和受激拉曼散射光的能量、时间过程和光谱测量。实验测量了有、无束匀滑条件下的散射光份额。结果表明,在当前实验条件下,通过束匀滑可有效降低散射光份额,提高激光注入率。     

DOP气溶胶浓度的光学检测

为了保证高效过滤器良好的工作性能,对广泛应用于高效过滤器效率及现场检漏的邻苯二甲酸二辛酯法进行了分析,并针对邻苯二甲酸二辛酯气溶胶浓度的光学检测理论进行了归纳总结.在Mie氏散射理论基础上,获得了在发特定气溶胶情况下,散射光强与被测粒子浓度的数学模型.在此理论模型下,设计制作了检测光学模组,并对其进行了测试.实验表明,理论模型合理,散射光强度与其质量浓度具有良好的线性关系.     

DOP气溶胶浓度的光学检测

为了保证高效过滤器良好的工作性能,对广泛应用于高效过滤器效率及现场检漏的邻苯二甲酸二辛酯法进行了分析,并针对邻苯二甲酸二辛酯气溶胶浓度的光学检测理论进行了归纳总结.在Mie氏散射理论基础上,获得了在发特定气溶胶情况下,散射光强与被测粒子浓度的数学模型.在此理论模型下,设计制作了检测光学模组,并对其进行了测试.实验表明,理论模型合理,散射光强度与其质量浓度具有良好的线性关系.     

Soot formation characteristics in a lab-scale turbulent pulverized coal flame with simultaneous planar measurements of laser induced incandescence of soot and Mie scattering of pulverized coal

Soot formation characteristics of a lab-scale pulverized coal flame were investigated by performing carefully controlled laser diagnostics. The spatial distributions of soot volume fraction and the pulverized coal particles were measured simultaneously by laser induced incandescence (LII) and Mie scattering imaging, respectively. In addition, the radial distributions of the soot volume fraction were compared with the OH radical fluorescence, gas temperature and oxygen concentration obtained in our previous studies [1], [2]. The results indicated that the laser pulse fluence used for LII measurement should be carefully controlled to measure the soot volume fraction in pulverized coal flames. To precisely measure the soot volume fraction in pulverized coal flames using LII, it is necessary to adjust the laser pulse fluence so that it is sufficiently high to heat up all the soot particles to the sublimation temperature but also sufficiently low to avoid including a too large of a change in the morphology of the soot particles and the superposition of the LII signal from the pulverized coal particles on that from the soot particles. It was also found that the radial position of the peak LII signal intensity was located between the positions of the peak Mie scattering signal intensity and peak OH radical signal intensity. The region, in which LII signal, OH radical fluorescence and Mie scattering coexisted, expanded with increasing height above the burner port. It was also found that the soot formation in pulverized coal flames was enhanced at locations where the conditions of high temperature, low oxygen concentration and the existence of pulverized coal particles were satisfied simultaneously.     

Effect of intrinsic optical feedback on the intersubband optical properties of spherical quantum dots

Optical feedback due to mutual relation between local field effect and intersubband transition in quantum dots is investigated for the first time. In this regard, dielectric function of quantum dots is considered up to the third order of nonlinearity. It is found that near the resonance, the intensity inside the dot is a function of frequency, which is determined by the optical feedback. This effect changes the magnitude of optical nonlinearity and its symmetry around the transition energy. The results indicate that the magnitude of the dielectric function decreases at frequencies below the transition frequency because of concentration of electric field inside the dot and vice versa. It is also shown that this effect is enhanced by increasing the intensity and resonance contribution in the dielectric function.     

Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.     

轴对称含烟黑火焰非均匀温度与烟黑浓度分布同时重建模拟研究

对于非均匀吸收、发射、无散射的轴对称含烟黑火焰对象,常规双色法不再适用。本文基于烟黑辐射特性,提出并模拟研究了同时重建火焰温度与烟黑容积份额的新的辐射测量方法。从重建结果看,重建误差主要集中在火焰中心区域,这是观测路径上测量误差累积的结果。温度重建主要受火焰断面参数分布类型影响,而烟黑容积份额重建主要受测量误差的影响,这由它们与单色辐射强度的内在关系所决定。     

旋光晶体在偏光干涉实验中电光效应的研究

研究了旋光晶体在偏光干涉实验中的电光效应，给出了旋光晶体在偏光干涉实验中出射光强与晶体旋光性之间关系的表达式I—Ao^2cos^2[β-（π/λ）（n1-nr)l]，以及与旋光晶体电光效应之间关系的表达式I—Ao^2cos^2[β-（π/λ）（n1-nr)l (π/λ）（n2-n1)l]。根据这些表达式给出的关系，将典型的旋光晶体La3Ga5SiO14制作成了电光Q开关，像那些用无旋光性晶体制作的Q开关一样工作良好。在中等功率输出的激光器中，La3Ga5SiO14晶体电光Q开关有可能取代氘化磷酸二氢钾(DKDP)晶体电光Q开关。     

Analysis of uncertainties in instantaneous soot volume fraction measurements using two-dimensional, auto-compensating, laser-induced incandescence (2D-AC-LII)

Laser-induced incandescence (LII) is an optical measurement technique capable of measuring soot volume fraction over a wide range of conditions. However, development of two-dimensional auto-compensating LII (2D-AC-LII) in the literature has been limited and until now, instantaneous measurements have not been demonstrated. In this paper, we successfully demonstrate instantaneous 2D-AC-LII soot volume fraction (SVF) measurements in an ethylene-air co-annular diffusion flame. Results were then used to support a detailed uncertainty analysis based on a Monte-Carlo simulation. Agreement between both the instantaneous and average SVF measurements with published data from attenuation measurements under identical conditions was found to be good. Uncertainties are discussed both in terms of an overall accuracy of the SVF measurement, which is strongly dominated by uncertainty in the optical properties of soot, and the comparative uncertainties with optical properties fixed. The uncertainty in an instantaneous 2D determination of SVF for a comparative measurement is dominated by photon shot noise, and in regions of high soot volume fraction it is below 25% (95% confidence interval). Shot noise uncertainty could be further reduced with additional pixel averaging at the expense of spatial resolution. This diagnostic shows significant promise for quantitative planar soot concentration measurements within turbulent flames.     

A model for aerosol mass concentration using an optical particle counter

A model for measuring aerosol mass concentration by an optical particle counter is presented using the conception of the average mass. In this model, to understand the meaning of the pulse height distribution of particles which is used to inverse mass concentration, the relationship among intensity distribution in the optical sensing volume, particle shape, and the pulse height distribution is discussed. To solve the instability of the equivalent factor, a novel two-step calibration method is proposed. The experimental results demonstrate that mass concentrations calculated by the model are in good agreement with those measured by a norm-referenced instrument. For samples of soot and air, the slopes of fitting lines of data points are 0.9582 and 0.9220, and the correlation coefficients are 0.9991 and 0.9965, respectively.     

Experimental comparison of soot formation in turbulent flames of Diesel and surrogate Diesel fuels

Soot formation is compared in turbulent diffusion flames burning a commercial Diesel and two Diesel surrogates containing n-decane and α-methylnaphthalene. A burner equipped with a high-efficiency atomisation system has been specially designed and allows the stabilisation of liquid fuels flames with similar hydrodynamics conditions. The initial surrogate composition (70% n-decane, 30% α-methylnaphthalene) was previously used in the literature to simulate combustion in Diesel engines. In this work, a direct comparison of Diesel and surrogates soot tendencies is undertaken and relies on soot and fluorescent species mappings obtained respectively by Laser-Induced Incandescence (LII) at 1064 nm and Laser-Induced Fluorescence at 532 nm. LIF was assigned to soot precursors and mainly to high-number ring Polycyclic Aromatic Hydrocarbons (PAH). The initial surrogate was found to form 40% more soot than the tested Diesel. Consequently, a second surrogate containing a lower α-methylnaphthalene concentration (20%) has been formulated. That composition which presents a Threshold Soot Index (TSI) very close to Diesel one is also consistent with our Diesel composition that indicates a relatively low PAH content. The spatially resolved measurements of soot and fluorescent soot precursors are quite identical (in shape and intensity) in the Diesel and in the second surrogate flames. Furthermore the concordance of the LII temporal decays suggests that a similar growth of the primary soot particles has occurred for Diesel and surrogates. In addition, the comparison of the LII fluence curves indicates that physical/optical properties of soot contained in the different flames might be similar. The chemical composition present at the surface of soot particles collected in Diesel and surrogate flames has been obtained by laser-desorption ionisation time-of-flight mass spectrometry. An important difference is found between Diesel and surrogate samples indicating the influence of the fuel composition on soot content.     

基于光谱诊断的烃类火焰碳烟形成机理研究综述

碳烟主要是烃类燃料不完全燃烧生成的产物,其对人类健康、空气质量以及燃烧装置的使用寿命都会产生有害影响。碳烟生成是一个复杂的物理化学过程,控制碳烟排放,需要克服碳烟生成和燃烧过程中物理和化学演化的巨大差异,这些差异表现为对碳烟纳观结构和表面官能团随碳烟氧化活性反应变化的深入探索研究。近些年,研究人员对碳烟的生成机理开展了系列研究,对碳烟生成各个物理化学反应阶段有了一定认识。结合光谱诊断技术可深入了解燃烧系统碳烟形成过程,确定碳烟颗粒分子组成、精细结构、浓度分布等特征,也可从碳烟结构变化、黑体辐射强度等方面详细了解碳烟形成过程。该文旨在阐述光谱诊断技术对烃类火焰碳烟表征的研究进展和发展趋势,探讨LIBS, LII和LIF等作为诊断工具在包含背景辐射的火焰中检测碳烟生成过程产生辐射强度准确性等问题。主要介绍了烃类火焰碳烟的形成机理(从前驱体产生、生长到颗粒生成、凝聚,最后进行颗粒氧化)。总结了探测碳烟性质光谱诊断方法的应用以及光谱诊断技术对燃烧过程中碳烟表征的研究现状,包括对碳烟体积分数、温度和基于图像处理的碳烟结构表征,反应碳烟前驱体(多环芳烃)、反应气氛、温度等对碳烟颗粒物生成的影响。最...