基于虚拟仪器的微弱信号检测处理技术研究

本文针对检测大气中有害气体浓度的热点问题,提出了运用相关检测技术对微弱气体浓度信号进行检测,通过可调谐半导体激光吸收光谱(TDLAS)技术对大气中的有害气体浓度信号进行初步采集,然后对采集到的信号进行除噪处理.通过理论的分析与证明,相关检测技术可有效的分析出被测信号中的有用信号,而且可以在噪声功率大于有用信号功率的情况下对有用信号进行有效识别.为了进一步验证该方案的有效性,本文还建立了LabVIEW的仿真实验平台,结论有效地论证了通过可调谐半导体激光吸收光谱技术与相关检测技术相结合可以方便的提取噪声中的有用信号,从而检测出气体的浓度.     

利用TDLAS技术检测SF6高压开关中的HF气体

介绍了一种可基于TDLAS技术的用于检测SF6高压开关中HF气体浓度的仪表,采用了电流调谐的方法,使用锁相放大器进行检波,并引入了三光路自动校准技术,避免了光路偏转以及光强衰减造成的误差,提高了仪表的稳定性、可靠性和测量准确性.     

基于FPGA在线气体检测系统设计

以FPGA为平台设计一套TDLAS在线气体检测系统。在线气体检测需要高精度以及快速的数据分析和处理速度。相比于传统单片机,FPGA在工作速度以及功耗等方面具有较大优势,可以保证数据分析和处理的实时性;基于TDLAS（可调谐二极管吸收光谱学）的二次谐波检测技术可以减小噪声等因素带来的影响,保证检测结果的精度。本文详细介绍了系统的检测原理以及TDL驱动电路的设计方法,并由FPGA产生所需调制信号。该系统适用于现场高精度高速度的气体监测。     

基于TDLAS技术的在线多组分气体浓度检测系统

为了提高环境气体监测精度,降低设备维护成本需求,设计了一种多组分气体同时或近同时在线检测系统。该系统基于TDLAS技术采用DFB可调谐激光测量气体浓度,能够实现760 nm O_2和2 326 nm CO混合气体同时在线监测。设计发射单元、接收单元等模块,分析TDLAS可调谐激光检测、PID温度控制、锁相检测原理。结合火电厂烟道氧量浓度测试,对系统进行了验证。实验结果表明:与传统的工业气体测量装置相比,该系统能获得更高的精度、更快的响应速度以及良好的稳定性,适应恶劣环境能力强,具有较好的实用性及可行性。     

可调谐半导体激光吸收光谱技术在脱硝微量氨检测系统中的应用

脱硝主要还原剂氨气的在线检测,是防止氨气对环境二次污染的有效手段。LGA-4500是基于可调谐半导体激光吸收光谱技术(TDLAS)的实时在线分析系统,可提供快速准确可靠的分析数据,是确保烟气排放安全、环保的一种理想分析系统。     

激光气体检测及温压补偿研究

可调谐半导体激光吸收光谱(TDLAS)是一种灵敏度高、分辨力高和响应快速的气体测量技术,基于(TDLAS)的激光气体分析仪具有预处理简单、不受背景气体和粉尘影响的特点,是工业过程气体在线分析理想选择。本文介绍了波长调制的吸收光谱浓度测量原理以及实际工况下浓度的温压补偿方法。     

基于TDLAS技术的低浓度CO检测系统设计

采用光谱法进行低浓度CO(ppm量级)检测时,由于信号强度低,噪声强,很难真实有效的将信号将测出来。针对这一特点,设计了一种基于可调谐半导体激光吸收光谱(TDLAS)技术的低浓度CO气体在线监测系统。该系统采用TDLAS技术,可以获得精细的CO吸收光谱信息,因此可以降低其他成分吸收的干扰。同时采用放大一滤波一再放大过程实现系统降噪,能够很好的获得低浓度CO的光吸收信息。经测试,该系统还具有较好的实时性、灵敏度和较高的准确性。     

激光微量水测量技术及应用

针对化工生产过程介质中微量水测量技术的不足,根据实际应用经验,介绍一种基于可调谐半导体激光吸收光谱技术(TDLAS)的激光微量水测量及其原理,与传统测量方法进行比较,说明该技术在响应速度、精度等方面的技术优势及应用效果.     

DOAS与TDLAS方法应用于烟气在线监测中的对比分析

传统的应用于烟气连续排放监测系统(CEMS)的直接抽取采样方法在实际维护和使用中存在诸多问题,这就为不抽取采样方法差分光学吸收法(DOAS)和可调谐二极管激光吸收光谱法(TD-LAS)在CEMS中的应用开辟了广阔的空间。从硬件构成、原理、数据处理方法、各自特点及其检测气体种类等多方面将两种方法与传统方法进行了比较,发现这两种方法均有各自的特点和优势,DOAS方法更加适合应用于CEMS,而TDLAS由于目前的技术问题和成本问题,更适合于检测大气中痕量气体。     

可调谐半导体激光吸收光谱(TDLAS)技术在冻干机中的应用方案研究

冷冻干燥是一种低温低压下在封闭环境中除去水分的药品生产工艺,工艺条件要求较高。可调谐半导体激光吸收光谱(TDLAS)技术是一种气体在线监测技术,具有灵敏度高、抗干扰、易于调谐等诸多优点,可将其运用于冻干机中,在药品生产过程中通过监测水蒸气的升华速率以判断两次干燥过程的终点,提升药品质量。现论述了冷冻干燥和TDLAS的一般原理以及国内外近阶段对TDLAS的研究成果,探讨了将两者结合的可行性,分析了运用TDLAS技术监测水蒸气的优势和难点,并设计出了监测方案。     

可调谐二极管激光吸收光谱技术测量低温流场水汽露点温度

露点温度是表征气体状态的一个重要参数,针对低温环境的低露点温度精确、快速、连续、原位测量的迫切需要,提出了可调谐二极管激光吸收光谱(TDLAS)技术对水汽露点温度测量的方案。首先与安徽省气象局的冷镜式露点仪一起对比测量标准温湿度箱内的露点温度,验证波长为1 381nm的TDLAS系统露点温度测量的可行性及精度,然后结合一套开放式的测量装置,进行低温度环境(最低温度100K)水汽露点温度原位测量。得到了实时的露点温度值,其中TDLAS露点测量结果与冷镜式露点仪测量结果一致性较好(相差小于1K),TDLAS测量的时间分辨率为0.83s,远远快于冷镜式露点仪的时间响应速度。对于更低气体温度的露点测量,获得了与气体温度变化趋势相同的露点温度,同时得到了随着环境温度降低,水汽逐渐趋向饱和的结论。     

基于TDLAS气体测量系统的仿真与分析

本文介绍基于MATLAB中的动态仿真工具SIMULINK，建立基于TDLAS的气体测量系统的仿真模型。仿真模型能较准确、真实地反映实际的光源调制结果与气室吸收情况。分析了各主要参数的变化对气体吸收曲线与二次谐波波形的影响。仿真的结果对TDLAS系统的开发有一定的参考价值。     

Measurement of turbulent supersonic steam jet flow characteristics using TDLAS

Ejectors have no moving parts and are preferable to mechanical compressors in many applications, but ejectors typically have a relatively low efficiency. To aid in the ejector design process, thorough understanding of the turbulent mixing of multi-phase compressible jets is beneficial.This paper reports experimental results for Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurements derived from an axisymmetric supersonic steam jet apparatus.In this experimental work, a supersonic steam jet nozzle exit of a diameter 13.6 mm was surrounded by a low-speed flow of dry nitrogen. The TDLAS system was traversed through the flow at three different planes downstream from the ejector nozzle exit: 15, 20, and 30 mm distance. At each of the three planes, line-of-sight measurements were made with the laser passing through locations between 0 and 15 mm from the jet centreline.Through the analysis of the TDLAS data and application of the Abel inversion method, the radial distribution of the pressure, temperature, and the concentration of the water-vapour were obtained. The key findings are that it is possible to determine key physical parameters using experimental TDLAS measurements when combined with a suitable numerical optimization approach.     

Improvement of Tunable Diode Laser Absorption System with a Novel Multipass Cell and Wavelet Transform

Combination of Tunable Diode Laser Absorption Spectroscopy(TDLAS)technique and multipass cell is an attractive approach for ultrahigh sensitive detection of trace gases.Theoretically,based on Beer-Lambert law,the longer optical path length and the larger gas absorption,the lower concentration gas could be detected.However,lower radiation intensity and inevitable etalon fringe resulted from multiple reflections would greatly weaken the Signal-to-Noise Ratio(SNR)and thus an expected ultrahigh sensitive detection system is difficult to achieve.In order to fully make use of the advantages of TDLAS and multipass cell,the base length and the total optical path length of the multipass cell are needed to be carefully balanced.Furthermore,the harmonic signals contaminated by various noises are processed with wavelet transform method.As a demonstration of this method,few low concentrations of gas CO in N2 are measured employing TDLAS technique and a novel sealed multipass cell with total optical length of 114 m.The detection limit is about 5×10-6(volume ratio),which is one order of magnitude better than earlier noise reduction.     

Time resolved 2D concentration and temperature measurement using CT tunable laser absorption spectroscopy

In this study, the noncontact and simultaneous 2D temperature and concentration measurement method has been developed to elucidate the reaction characteristics and improve the relevant simulation code. The technique is based on a CT method using absorption spectra of molecules such as H₂O, NH₃ and CH₄. The CT Tunable diode laser absorption spectroscopy (TDLAS) method using 16-path laser beams was applied to measure 2D temperature, NH₃ and CH₄ distributions in engine exhausts and oscillating flames. Simultaneous and time resolved 2D temperature, NH₃ and CH₄ distributions were successfully reconstructed using a set of 16-path absorption spectra. Since CT TDLAS has a potential of kHz response time, this method enables real-time 2D temperature and species concentration measurements in various industrial processes including engine applications.     

激光光谱技术在燃烧流场诊断中的应用

介绍了用于燃烧流场诊断的激光光谱技术的研究进展,叙述了相干反斯托克斯喇曼散射、自发振动喇曼散射、激光诱导荧光、分子滤波瑞利散射、可调谐二极管激光吸收光谱等技术的基本原理及其实验系统.给出并分析了激光光谱技术对预混火焰稳态燃烧场和固体燃剂瞬态燃烧场的温度、主要组分及浓度、流场密度和火焰构造测试的实验结果.实验结果表明,基...     

TDLAS技术在烯烃生产过程中的多组分检测应用

烯烃工业生产过程中的多组分在线检测是对其工业过程有效控制、提高处理装置综合效益的重要手段。本文以在线检测烯烃裂解炉的清焦过程生成的一氧化碳和二氧化碳为应用案例,采用可调谐二极管激光吸收光谱技术(TDLAS)作为分析平台进行多组分分析。针对清焦过程,设计了检测0~5%量程CO和CO_2的模拟实验。对气体含量随机分布的19组数据分别采用多变量最小二乘算法(CLS)、单组分偏最小二乘算法(PLS1)和多组分偏最小二乘算法(PLS2)进行建模和评估。在后续的多组分交叉干扰实验和CO_2的扩展量程准确性测试实验中,PLS1模型的最大误差小于±0.05%,PLS2的小于±0.10%,CLS的小于±0.20%。因此,TDLAS技术结合PLS1算法在实现化工过程中的多组分在线检测时具有先进性。     

A fiber optic methane sensor based on wavelength adaptive vertical cavity surface emitting laser without thermoelectric cooler

Based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) technique and the feature of Vertical Cavity Surface Emitting Laser (VCSEL) wavelength scanning range up to dozens of nanometer, methane detection technique based on wavelength adaptive VCSEL without Thermoelectric Cooler (TEC), is proposed, then the laser methane sensor system design is followed. The reliability experiments study under variety of environments in laboratory, such as temperature impact test, damp heat, and cyclic and dusty impact test, were carried out. And then the test data and some analysis were given. These data verified the feasibility of the wavelength adaptive technique, and these data showed the laser methane sensor can provide long working time without any calibration, and they have the advantages of high accuracy and stability.