基于TDLAS技术的N_2O气体检测系统设计

基于红外光谱吸收及谐波检测原理,讨论了谐波信号和气体浓度关系,搭建了基于可调谐激光吸收光谱技术的气体检测系统。该系统采用低频锯齿波和高频正弦波联合调制激光器,并由锁相放大电路提取一次谐波和二次谐波信号幅值,以STM32F103VB控制器为核心,进行数据处理与数据上传,实现对0~0.1%浓度范围氧化亚氮(N_2O)气体实时测量。首先,介绍了系统的总体设计与核心结构,包括系统的硬件结构与软件结构;并进行了系统的标定和性能测试,结果表明二次谐波和一次谐波信号幅值比与浓度具有良好的线性关系,检测精度可达20×10~(-6),满足对N_2O气体实时监测的需求。     

基于激光吸收光谱的SF_6/N_2混合气分解产物同时检测

针对SF_6分解气中H_2S、CO、HF等3种气体进行在线监测,研制基于激光吸收光谱的SF_6分解气在线监测装置,提出采用时分复用的方案实现多组分气体同时测量,对激光器的波长参数进行分析并测试。针对近红外波段CO和H_2S气体吸收谱线弱的问题,提出独立放大电路方案,研制样机并通入混合组分气体进行验证。根据获得二次谐波曲线和浓度随时间变化曲线表明,该系统目前可以实现的检测限为CO 10 ppm,H_2S 4 ppm,HF 1 ppm,可以满足高灵敏度SF_6分解气在线监测和故障预警需求。     

基于剩余幅度调制技术对强吸收下气体体积分数的测量研究

在可调谐半导体激光吸收光谱技术中,可利用剩余幅度调制信号实现对气体参数的免标定测量。然而现有RAM方法均需做弱吸收假设和简化,同时引入复杂的修正函数以提取完整的透射率信号用于气体浓度反演。针对此问题,建立了适用于任意吸光度和调制系数下的傅里叶光谱吸收模型,提出了直接对背景信号归一化的一次谐波Y分量进行拟合的免标定算法,减少了重建吸光度引入修正函数的过程。使用CH4为目标气体进行实验,体积分数计算的相对误差小于2%,标准偏差均小于4×10-2%,验证了该方法的可行性。     

基于实时反射率修正的离轴积分腔甲烷测量系统

针对大气CH_4浓度测量中的H_2O干扰以及高反镜反射率的标定问题,提出了一种波长调制离轴积分腔测量系统中反射率实时标定的方法,并结合CH_4浓度免标定反演修正算法解决了CH_4浓度测量中H_2O干扰的问题,实现了大气CH_4浓度的免标定测量。利用该系统对大气CH_4浓度进行了测量,测量得到的大气CH_4平均浓度为1.821 ppmv,标准偏差为0.024 ppmv,时间分辨率为10 s。Allan方差分析表明该测量系统检测限可达4.6 ppbv。因此,该系统可实现大气CH_4浓度的免标定实时测量。     

光纤多气体检测系统的研究

采用光纤光栅波分复用技术,通过光纤光栅和压电陶瓷对LED进行波长调制,获得与气体吸收峰对应的窄带反射出射光,检测二次谐波,实现多气体浓度检测.建立了谐波检测的数学模型,进行了C2H2和CO测量系统的研究.     

FP6型内燃机废气综合分析装置的研制

FP6型内燃机废气综合分析装置由取样装置、分析装置、自动记录仪三部份组成。取样方式为直接取样,样气经除尘、半导体致冷除水处理后,分四路进入分析装置。分析装置装有四台红外线气体分析仪,分别测量内燃机排气中的CO、CO_2、HC、NO四种成份的浓度,测量结果由表头直接显示,并由自动记录仪进行记录。本文中还概述了国外测量CO、CO_2、     

稀释法CEMS在氨法脱硫的应用

文章针对神华宁煤某电厂锅炉氨法脱硫后烟气湿度大,难以利用一般CEMS测量方法准确测量烟气成分的问题,根据稀释法CEMS测量特点,作者将该测量方法利用在氨法脱硫后烟气测量中,并对测量系统进行了详细设计。根据最终运行结果显示,稀释法CEMS测量适合氨法脱硫后烟气测量。     

烟气连续排放监测系统 (3 测量气体浓度和烟气流速的在线监测系统)

由于抽取式监测系统存在不少问题 ,导致直接在烟道测量源水平气体浓度在线监测系统的发展。所谓在线系统即在没有改变烟气的组成并在颗粒物存在的条件下直接测量气体浓度的系统。在线监测系统要求能经受烟道环境条件的考验 ,结构简单 ,比抽取式监测系统的子系统要少。最初设计的在线监测系统 ,只能测量燃烧源排放烟气中污染物浓度在 5 0 0ＰＰｍ和以上的气体。业已证明 ,只要按适合的质量保证措施进行维护 ,在线监测系统就能够顺利地、连续地运行。由于气体控制装置的出现 ,使排气中污染物的浓度降低。一些在线监测器要满足测量低浓度的污染…     

基于彩色相机的运动燃煤颗粒温度测量研究

基于McKenna燃烧器的平面火焰携带流燃烧器系统的燃烧环境,采用彩色相机测温系统对运动中的燃煤颗粒进行拍摄。彩色相机测温系统经过黑体炉进行温度测量标定后,利用其r、g波段的响应,采用双色法对燃煤颗粒的温度进行测量。测温系统的标定采用基于BP神经网络训练的方法进行,通过对蜡烛燃烧火焰的拍摄,将得到的颗粒温度与热电偶数据进行对比,验证了测温系统的可靠性。实验研究了燃烧器出口不同距离处燃煤颗粒的温度信息,结果表明,燃煤颗粒温度随颗粒到喷嘴出口距离的变化整体呈先上升后下降趋势。该结果为研究煤粉燃烧过程及着火机理提供了参考。     

固定污染源烟气汞排放在线连续监测中的若干难点及系统设计

我国是一个产煤大国,而且由于我国燃煤技术普遍落后,燃煤释放的汞对环境生态系统的污染更为严重,因此对烟气重金属汞的排放监测是很重要的。烟气汞排放的的测量主要有湿化学分析法、干法吸附剂法和在线分析法。由于汞的特殊性及烟气中汞形态的复杂性,烟气汞在线连续监测有较多的难点。本文在介绍汞的危害、当前汞监测的主要方法的基础上,提出了若干个烟气汞在线监测的难点,比如浓度低、易吸附、汞形态转换、抗干扰等,并针对这些难点提出了一定的解决方案,最后设计了一套烟气汞排放在线监测系统,主要包括烟气采样、样气传输、气体转化、冷凝除湿、汞分析仪、流量控制等单元,并对其性能进行了相关测试。     

Numerical study on no emission with flue gas dilution in air and fuel sides

Flue gas recirculation (FGR) is widely adopted to control NO emission in combustion systems. Recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance much improved reduction in NO per unit mass of recirculated gas, as compared to conventional FGR in air. In the present study, the effect of dilution methods in air and fuel sides on NO reduction has been investigated numerically by using N3 and CO2 as diluent gases to simulate flue gases. Counterflow diffusion flames were studied in conjunction with the laminar flamelet model of turbulent flames. Results showed that CO2 dilution was more effective in NO reduction because of large temperature drop due to the larger specific heat of CO2 compared to N₂. Fuel dilution was more effective in reducing NO emission than air dilution when the same recirculation ratio of dilution gas was used by the increase in the nozzle exit velocity, thereby the stretch rate, with dilution gas added to fuel side.     

整车排放试验污染物瞬态质量测量方法研究

针对整车排放开发试验中直采排放测量设备不能直接测量出污染物瞬态质量的问题,采用了在袋采排放测量系统中增加稀释空气流量计SAO或者示踪CO2分析仪的方法,将袋采和直：采测量设备关联起来,实现了污染物的瞬态质量测量。采用SAO方法时,通过测量混合前稀释空气的瞬态流量,计算出汽车排气的瞬态体积,再用直采系统测出污染物的瞬态体积浓度值就可以换算成汽车排气污染物的瞬态质量值。采用TraceCO2方法时,通过比较稀释管道中混合气的CO2瞬态体积浓度值与稀释前尾气的CO2体积浓度,得出了动态稀释比,从而间接计算出了汽车排气的瞬态体积,进而计算出污染物瞬态质量值。试验结果证明,加装稀释空气流量计SAO和示踪CO2分析仪的排放测量系统,能够有效测量出汽车排气中污染物的瞬态质量值。     

Combustion monitoring of a water tube boiler using a discriminant radial basis network

This research work includes a combination of Fisher’s linear discriminant (FLD) analysis and a radial basis network (RBN) for monitoring the combustion conditions for a coal fired boiler so as to allow control of the air/fuel ratio. For this, two-dimensional flame images are required, which were captured with a CCD camera; the features of the images—average intensity, area, brightness and orientation etc of the flame—are extracted after preprocessing the images. The FLD is applied to reduce the n-dimensional feature size to a two-dimensional feature size for faster learning of the RBN. Also, three classes of images corresponding to different burning conditions of the flames have been extracted from continuous video processing. In this, the corresponding temperatures, and the carbon monoxide (CO) emissions and those of other flue gases have been obtained through measurement. Further, the training and testing of Fisher’s linear discriminant radial basis network (FLDRBN), with the data collected, have been carried out and the performance of the algorithms is presented.     

突扩燃烧室燃烧火焰深度二维温度场测量

针对电子耦合器件（CCD）辐射测温中因温度过高导致的辐射图像“发白”问题，提出了摄像机快门时间控制模型，该模型能有效地防止CCD光敏面输出过饱和电流。在此基础上，引入计算机断层图像检测理论，对燃烧火焰不同聚焦面的CCD成像过程进行研究，建立了用单一摄像机实现火焰深度方向聚焦面辐射图像与温度场分布关联模型，实现了火焰深度二维温度场的在线测量。实验室煤气燃烧实验表明：黑体炉标定后的关联模型实现了燃烧火焰内部温度场的在线测量与诊断，快门控制模型能有效解决辐射图像“发白”问题，扩大了CCD辐射测量的温度范围。     

用于汽车尾气监测的新型气体浓度传感器系统

针对汽车尾气新的排放标准和检定方法的实施,设计了用于汽车尾气监测的热电堆传感器系统。采用导电不定型碳多层镀膜技术的电调制红外光源,使其调制频率最高可以达到100 Hz.对传统气室结构进行了优化设计,使气室与外支撑分离,降低了外界环境的影响。实现了当红外光照射到吸收窗时,在输出引脚上产生与入射光功率成正比的输出信号电压,-3 dB衰减频率大约为10 Hz.实验结果表明：该气体浓度传感器系统满足汽车尾气中CO、CO2、HC监测的要求。     

Control of a pulse combustion reactor with thermoacoustic phenomena

We have developed a novel way of controlling parameters in reactors using flue gases from pulse combustion as a direct source of heat and as a means of transport of particulate materials synthesized in a slightly reductive environment or oxidative environment. The reactor is used for a spray pyrolysis synthesis of materials or the sintering of different ceramic powders. The reactor is heated directly, which means reduced energy losses, and the enhanced drying reported using pulse combustion is implemented for faster reaction. A slightly reductive atmosphere is maintained by combusting a stoichiometric fuel and air mixture and adding acetylene to the flue gas flow. Reaction conditions must be carefully controlled; this is achieved by influencing the characteristic times of the pulse combustion and changing the frequency of combustion and with it the temperature and flue gas composition in the reactor. The frequency is changed by nitrogen dilution of burning gas, influencing the mixing of the combustible mixture with hot flue gases and damping of frequencies with a secondary Helmholtz resonator. The frequency of pressure oscillations in the combustor should be the same as one of the harmonic frequencies of the reactor pipe to reach an acoustic resonance. In this work, the frequency of pulse combustion was altered in such a way that resonance was established with the reactor pipe and that a suitable reaction environment was obtained. With good control over all parameters, we were able to synthesize different Li-ion cathode materials, such as LiFePO₄ and Li(Ni_xMn_yCo_z)O_2.     

烟气排放连续监测系统的烟气参数在线监测技术

简要介绍了烟气排放连续监测系统的烟气参数监测项目及技术要求,包括炯气流速、烟气水分含量、烟气含氧量在线监测技术。对烟气参数在线监测的应用与发展进行了探讨。     

空气分级炉膛煤粉燃烬模型及实炉试验对比

传统的炉膛分区段传热设计模型忽略了煤粉燃烬计算，适用于非空气分级燃烧。随着空气分级低NOx燃烧技术的普遍应用，在炉膛分区段传热计算中引入煤粉燃烧模型以确定沿炉膛高度燃烬分布，对于提高炉膛上部屏式或辐射受热面蒸汽温度设计准确性有较为重要的意义。建立了改进型分区段传热计算和煤粉燃烧相耦合的空气分级炉膛燃烬和传热模型，对一台空气分级低NOx燃烧锅炉进行了全负荷工况试验，采用该模型对试验工况进行燃烬和传热模拟，得到空气分级锅炉炉膛煤粉燃烧过程的物理图景以及煤粉沿炉膛高度燃尽分布，并研究了燃烧模式和表面反应动力学参数等对燃烬度分布的影响。结果表明，炉膛出口煤粉颗粒燃烬度数值解与大部分测试数据吻合较好，煤粉颗粒燃烧后期灰分引起热退火抑制效应以及炉内局部烟气含氧量分布不均匀是引起模型误差的主要因素，所建立的燃烧和传热耦合模型与传统的炉膛分区段传热模型计算量相当，适合工程应用。     

Development of an air fuel control system for a domestic wood pellet boiler

Wood pellets are a kind of solid biomass energy and a renewable energy source. Made by compressing sawdust, wood pellets have a higher energy density than split firewood and wood chips. In 2007, the new and renewable energy (NRE) portion was 2.4% with respect to total primary energy in Korea. The Korean government wants to increase the new and renewable energy (NRE) portion up to 6.1% by 2020 [1]. To achieve this target, the government has been establishing some policies, such as incentive policy, NRE mandatory use for public building and renewable portfolio standard (RPS) and so on. To supply wood pellets as fuel for the combustion chamber of a wood pellet boiler, most domestic wood pellet boilers put a constant volume by using an auger type fuel feed system. In an auger system as fuel feeding, there is the possibility of changing energy input due to the different density of wood pellets even in a constant volume flow rate of wood pellets. If fuel input rate is changed without any correction of air flow rate for combustion, the condition of combustion in a wood pellet boiler can be deteriorated. We have developed an air-fuel control system for a domestic wood pellet boiler by using flue gas oxygen concentration measurement and a PID controller. To measure O₂ concentration of flue gas, a wide band O₂ sensor was adopted. We changed fuel input from 100% to 50% by artificial manipulation to confirm the control system. The O₂ concentration in flue gas can be controlled to be 8.5% ± 1% without significant change of CO and NO_x concentration.     

Novel Gas Concentration Measurements based on Harmonic Detection and a Broadband Light Source

The determination of gas concentration based on harmonic detection was studied theoretically and experimentally. The principle of second harmonic detection technology based on a broadband light source and the impact of modulation parameters on the harmonic signals were analyzed theoretically. The principles of multiple modulation were analyzed in order to improve the detection resolution. A fiber Bragg grating bonded to a carbon fiber cantilever was designed to achieve wavelength modulation. The impact of the modulation frequency and voltage amplitude on the second harmonic signals were studied experimentally. The output of the detector and the impact of the random noise were analyzed at different modulation frequencies and amplitudes. The optimum frequency and amplitude were determined to be 40 Hz and 2 V. The measurement of acetylene was carried out using this system. The results show that the gas measurement limit was 500 ppm, the stability was 3.92%, and the system sensitivity was 1 µV/ppm.