基于可调谐二极管激光吸收光谱技术在线监测机动车尾气排放CO和CO2的方法

基于可调谐二极管激光吸收光谱学(TDLAS)技术的原理,在分析了在线监测机动车尾气排放的污染气体浓度的特殊性的基础上,研究了烟羽的影响以及在线监测中浓度反演的方法,研制了TDLAS实验系统,用该系统对北京市学院路监测点和大羊坊高速公路收费站监测点进行了机动车尾气CO和CO2的实时在线监测,并对监测数据进行了统计和分析.实验表明,TDLAS技术具有灵敏度高、选择性好、响应速度快等特点,适合于机动车尾气排放CO和CO2的在线监测.     

烟气分析仪中电化学气体传感器的使用与维护

烟气分析仪被广泛地应用于烟道中有害气体和氧含量的测量,电化学气体传感器是烟气分析仪检测气体的核心,科学合理地使用、维护,可有效地延长电化学传感器的寿命.正确使用、维护与标定,对保证其测量结果的准确度尤为重要,以保证烟气分析仪的测量准确性.     

用pVTt法气体流量装置检定流量计

为满足0.2级及0.5级高准确度气体流量计量值溯源需求,建立大标准容积的pVTt法气体流量标准装置,使用组合阀门换向法对气体流量计进行动态检定,利用附加质量修正消除阀门换向系统时间引起的误差,分析检定过程中关键参数如压力、温度变化规律,获得使测量不确定度最优化的检定流程。通过分析测量过程中标准容器、温度、压力、附加质量等关键量的影响,进行测量不确定度评定,得到使用pVTt法气体流量标准装置检定气体流量计的测量不确定度为Ur=0.11%(k=2),证明使用pVTt法气体流量标准装置检定0.2级及0.5级气体流量计的可行性及合理性。     

浅谈旋进漩涡智能流量计在使用中存在的弊端

在测量气体流量时,由于气体的密度受压力、温度的影响较大,为了准确地测量气体的体积流量,就必须同时跟踪被测气体的工况压力和温度,从而将不同工况下的气体体积流量转变为标准状态下的体积流量。旋进漩涡智能流量计就是基于这一要求而开发研制出来的一种流量计。该流量计是集压力传感器、温度传感器、流量计算机、即地显示于一体,并能进行温度、压力、压缩因子自动补偿的新一代流量计,无机械可动部件。     

能连续计量的钟罩式气体流量标准装置

介绍能连续计量的钟罩式气体流量标准装置,以某型检测容积为2000L的气体流量标准装置为例,详述了其系统结构及工作原理.研制完成后,使用经第三方机构检定的2台标准流量计(E+H气体科式质量流量计)对其进行了校验,结果表明,本装置的测量值与标准流量计的读数值之间的误差范围均在标准流量计的精度等级范围内.     

采用流量计测量复合分子泵抽速装置研制

本工作研制了一台采用流量计测量复合分子泵抽速的装置.本装置由测试台车、机柜、计算机自动控制和数据采集处理系统三部分组成.选用3个高精度流量计,满量程分别为1000 sccm、100 sccm和10 sccm,并联组成流量计组件用于测量输入气体的流量,选用高精度的复合真空计测量真空测试罩内气压.抽速测试结果显示,一台1200 L/s的复合分子泵N2抽速重复测量5次,14个气压测试点对应的抽速的最大相对标准偏差小于2％,重复性好.抽速测量的误差主要由流量计和真空计的系统误差决定.采用流量计测量一台分子泵在气压2.00×10-3 Pa～2.00 Pa范围的抽速,测量时间20 min以内.     

德国联邦物理技术研究院(PTB)气体微流量计量评介

在真空技术应用中 ,高精度气体微流量计用于连续膨胀法校准系统压力的产生、漏孔漏率的测量以及真空泵抽速的测定。PTB先后研制了三代气体微流量计 ,第一代为手动型 ,第二代为半自动型 ,第三代为全自动型。本文详细介绍了PTB研制的气体微流量计的性能和特点 ,并介绍了气体微流量计在真空漏孔的漏率测量方面的应用。另外 ,还介绍了PTB最近研制的大气压力下漏孔漏率测量系统的性能和特点     

推导式变组分气体质量流量计的原理与现场验证

干气是石化行业重要的物料，对其进行准确计量具有重要意义。但其是典型的变组分气体，不能采用恒定组分气体质量流量的测量方法。推导式气体质量流量计，用涡街流量传感器测量工况条件下的体积流量，用旋涡发生体前后的压差计算流量计出口侧气体密度，经计算得到质量流量，从而解决了变组分气体质量流量测量难题。文章阐述了测量管内气体雷诺数影响校正、可膨胀性补偿，以及设计计算、计量检定方法和安装调试。实践表明，这种方法简单可靠，相比科氏力质量流量计可显著节省投资。     

德国联邦物理技术研究院（PTB）气体微流量计量评介

在真空技术应用中，高精度气体微流量计用于连续膨胀法校准系统压力的产生、漏孔漏率的测量以及真空泵抽速的测定。FIB先后研制了三代气体微流量计，第一代为手动型，第二代为半自动型，第三代为全自动型。本详细介绍了FIB研制的气体微流量计的性能和特点，并介绍了气体微流量计在真空漏孔的漏率测量方面的应用。另外，还介绍了FIB最近研制的大气压力下漏孔漏率测量系统的性能和特点。     

锥形量热仪的校准方法研究

本文概括说明了锥形量热仪的原理、构成,提出了参照JJG 968-2002<烟气分析仪>和JJG 257-2007<浮子流量计>国家计量检定规程对其核心部件气体分析仪和气体流量计的校准,校准参量包括气体分析仪的零点漂移、示值误差、示值重复性、示值稳定性和响应时间以及气体流量计的示值误差和回差.该校准方法量值准确可靠、简单...     

Influence of ethanol-gasoline blended fuel on emission characteristics from a four-stroke motorcycle engine

Emission characteristics from a four-stroke motorcycle engine using 10% (v/v) ethanol-gasoline blended fuel (E10) were investigated at different driving modes on the chassis dynamometers. The results indicate that CO and HC emissions in the engine exhaust are lower with the operation of E10 as compared to the use of unleaded gasoline, whereas the effect of ethanol on NO(X) emission is not significant. Furthermore, species of both unburned hydrocarbons and their ramifications were analyzed by the combination of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/flame ionization detection (GC/FID). This analysis shows that aromatic compounds (benzene, toluene, xylene isomers (o-xylene, m-xylene and p-xylene), ethyltoluene isomers (o-ethyltoluene, m-ethyltoluene and p-ethyltoluene) and trimethylbenzene isomers (1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene)) and fatty group ones (ethylene, methane, acetaldehyde, ethanol, butene, pentane and hexane) are major compounds in motorcycle engine exhaust. It is found that the E10-fueled motorcycle engine produces more ethylene, acetaldehyde and ethanol emissions than unleaded gasoline engine does. The no significant reduction of aromatics is observed in the case of ethanol-gasoline blended fuel. The ethanol-gasoline blended fuel can somewhat improve emissions of the rest species.     

烟气超声流量计时间测量准确度校准方法研究

大口径气体超声波流量计广泛应用于烟道排放监测和工业控制等领域。超声波流量计的传播时间测量准确度校准是非实流校准的重要环节,通过建立超声波流量计时间测量准确度校准装置,实现对大口径气体超声流量计传播时间的非实流校准。该文首先提出3种不同的超声流量计传播时间校准方法,分析不同方法的影响因素,其次通过改变探头间距离,对不同探头间距时超声波流量计传播时间的测量误差进行校准。试验结果表明:超声波流量计传播时间的测量误差随距离变化,并确定利用标准声速对超声波流量计传播时间进行修正的方法更为准确,测量结果不确定度为0.2%。     

Design and implementation of a smartphone-based portable ultrasound pulsed-wave Doppler device for blood flow measurement

Blood flow measurement using Doppler ultrasound has become a useful tool for diagnosing cardiovascular diseases and as a physiological monitor. Recently, pocket-sized ultrasound scanners have been introduced for portable diagnosis. The present paper reports the implementation of a portable ultrasound pulsed-wave (PW) Doppler flowmeter using a smartphone. A 10-MHz ultrasonic surface transducer was designed for the dynamic monitoring of blood flow velocity. The directional baseband Doppler shift signals were obtained using a portable analog circuit system. After hardware processing, the Doppler signals were fed directly to a smartphone for Doppler spectrogram analysis and display in real time. To the best of our knowledge, this is the first report of the use of this system for medical ultrasound Doppler signal processing. A Couette flow phantom, consisting of two parallel disks with a 2-mm gap, was used to evaluate and calibrate the device. Doppler spectrograms of porcine blood flow were measured using this stand-alone portable device under the pulsatile condition. Subsequently, in vivo portable system verification was performed by measuring the arterial blood flow of a rat and comparing the results with the measurement from a commercial ultrasound duplex scanner. All of the results demonstrated the potential for using a smartphone as a novel embedded system for portable medical ultrasound applications.     

Measurements of CO, CO2, OH, and H2O in room-temperature and combustion gases by use of a broadly current-tuned multisection InGaAsP diode laser

A new laser technology that achieves nearly 100-nm quasi-continuous tuning with only injection-current control in a four-section grating-coupler sampled-reflector laser was used to detect CO and CO(2) simultaneously in room-temperature gas mixtures. The same grating-coupler sampled-reflector laser was used to perform in situ measurements of CO, H(2)O, and OH in the exhaust gases of a CH(4)-air flame. This laser is being evaluated for inclusion in a multispecies combustion-emissions exhaust-analysis sensor, and its operational characteristics as they have an impact on gas sensing are described. Preliminary results suggest that this single laser can be used to replace multilaser sensor configurations for some combustion-emissions monitoring applications.     

Co-firing of paper sludge with high-calorific industrial wastes in a pilot-scale nozzle-grate incinerator

Experiments on the co-firing of high-calorific industrial wastes with paper sludge were performed in a pilot-scale industrial waste incinerator with a nozzle-type grate system. The incineration capacity was approximately 160kg/h. The temporal variations in the temperatures and exhaust gas emissions were monitored and used as parameters for determining the desirable incineration conditions. The high CO emissions that were mainly due to the rapid vaporization of combustibles from high-calorific industrial wastes could be alleviated through the co-firing of sludge with the high-calorific industrial wastes. Because of the high nitrogen content in the sludge, the increase in the co-firing rate caused higher NO emissions in the flue gas. If the total calorific value of the feed was lower than 750,000kcal/h, for 25-30% of sludge co-firing, the temperature of gases exiting the secondary combustion chamber might be lower than that required by regulations.     

便携式气体微流量计的设计

为了实现在工作现场对氦质谱检漏仪进行全量程漏率示值的校准,设计了一套便携式气体微流量计。该流量计由供气与抽气系统、定容室与压力测量系统、流量测量系统和烘烤系统等四部分组成,采用固定流导法及定容法两种模式提供和测量流量。在流量计的设计中,解决了小孔流导的设计和计算、定容室和抽气系统的小型化设计、应用选择性抽气技术延伸流量测量下限等关键技术,同时还采用了分体式结构设计,使流量计具有便于拆卸及携带,操作简单等优点。流量计预计达到的技术指标是,测量范围(:10-4～10-11)Pa.m3/s,标准不确定度小于10%。     

Characterization of a mid-infrared hollow waveguide gas cell for the analysis of carbon monoxide and nitric oxide

Infrared spectroscopy is commonly applied to the analysis of small gas-phase molecules. One of the limitations of using Fourier transform infrared (FT-IR) spectroscopy for these applications is the time response of long path length gas cells. Hollow waveguides (HW) that transmit in the mid-infrared spectral range have higher optical efficiencies compared to long path length cells due to smaller cell volumes. This study characterizes a silver coated, 2 mm inner diameter HW for the analysis of carbon monoxide (CO) and nitric oxide (NO) and compares the performance to a 3 m gas cell and traditional gas analyzers. The HW was found to have a CO response time less than the NDIR analyzer and approximately one-tenth of the response time on the FT-IR system equipped with a 3 m gas cell. The utility of the increased response time was demonstrated by measuring CO concentrations in sidestream cigarette smoke at the same temporal resolution as an NDIR analyzer. A 10 to 60% increase in sensitivity using various frequencies for both CO and NO was observed using the HW compared to the 3 m multipass gas cell. However, cost savings for gas-sensing applications can be achieved on a per analyte basis by using FT-IR spectroscopy, especially in combination with a HW gas-sensing module, which is significantly less expensive than a multipass gas cell.     

Laser photoacoustic spectrometer for remote monitoring of atmospheric pollutants

An acoustically resonant CO(2) laser photoacoustic (PA) spectrometer for remote or in situ monitoring of air pollutants has been designed. The salient features of this PA system, along with the optimization tests of various operating parameters that affect the PA signal (buffer-gas pressure, type of buffer gas, laser power, gas concentration, and acoustic modes), are described. The system has been applied for the detection of pollutants emitted from the exhaust of a car located at a remote distance. Also, an alarm system based on the PA detection technique has been built for leak detection of toxic gases at industrial complexes. The minimum detectable concentration of C(2) H(4) and SO(2) with this system is 50 parts in 10(12) by volume and 50 parts in 10(9) by volume, respectively.     

Attribute Selection Based on Rough Set Theory for Electromagnetic Interference (EMI) Fault Diagnosis

Electromagnetic emissions are radiated from every part of a personal computer motherboard, thus producing electromagnetic interference (EMI). EMI has an adverse effect on the surrounding environment because EMI could cause malfunctions or fatal problems in other digital devices. EMI engineers diagnose motherboard EMI problems using the electromagnetic noise data measured by the spectrum analyzer. Finding the sources (e.g., PS2, USB, VGA) of electromagnetic noise is a time-consuming process. The attribute selection and fault diagnosis was developed based on the advantage of rough set theory (RST). RST is a novel data mining approach for dealing with vagueness and uncertainty. It can be used to find hidden patterns in data sets. In this study, the basic rough set theory concepts are introduced. The rough set approach enables one to discover the minimal subsets of condition attributes associated with the motherboard EMI fault diagnosis problem. The operating sequence includes data collection, data preprocessing, discretization, attribute reduction, reduction filtering, rule generation, and classification accuracy. Historical EMI noise data, colleted from a famous motherboard company in Taiwan, were used to generate diagnostic rules. Our research result (average diagnostic accuracy of 80% above) shows that the RST model is a promising approach for EMI diagnostic support systems.     

Adaptive Pulse Repetition Frequency Technique for an Ultrasonic Transit-Time Gas Flowmeter for Hot Pulsating Gases

A technique of using an adaptive pulse repetition frequency (PRF) to operate an ultrasonic contrapropagation transit-time gas flowmeter (UFM) is introduced. This adaptive PRF technique allows transient measurements of hot (up to 450$^circhboxC$) and pulsating (up to 1.5 kHz) gas flows. Such conditions occur in the exhaust gas of a combustion engine. Here, a UFM with the widely used fixed PRF technique is not applicable, because the large gas temperature variations would prevent a reliable detection of ultrasonic pulse arrival times. Coherently reflected waves are generated within the gas because of the unavoidable acoustic impedance mismatch between the gas and the transducers, and, depending on the gas temperatures, these echoes overlap with the main signal. The adaptive PRF technique overcomes this problem and allows correct pulse detection over the whole temperature range required. The UFM utilizes special high-temperature-resistant capacitance ultrasonic transducers (CUTs) to meet the requirements in terms of operating temperature range and dynamic response. Results, which are obtained with a preliminary laboratory prototype, are presented for the exhaust gas mass flow rate in a$varnothing$50-mm pipe measured at gas temperatures of up to 450$^circhboxC$and at PRFs of up to 5.5 kHz, which is an increase in frequency response of one order of magnitude in comparison to existing measurement systems.