影响冷镜式露点仪测量准确度因素分析及解决方法研究

目前国际上的精密露点仪大多为光电检测且热电制冷的镜面冷凝式露点仪。露点仪的种类繁多，且冷却方式、露点检测方法各不相同。文中阐述了影响冷镜式露点仪的测量的一些因素，诸如过冷水、镜面杂质、开尔文效应等，并进行了相应分析，提出了一些解决方法。     

冷镜式精密露点仪标准装置的技术改造

介绍通过设计多级干燥模式和精密露点仪校验台系统,实现对冷镜式精密露点仪标准装置进行技术改造,从而达到提高露点温度检测范围、检测精度,检测效率的目的,具有广泛借鉴价值。     

基于冷镜式原理的高精度露点温度检测系统设计

为了实现对露点温度的精密测量,设计了一种基于冷镜式原理的高精度露点温度检测系统。硬件部分主要设计了铂电阻测温电路、温度采集电路等。运用冷镜式露点温度检测方法,同时采用铂电阻测温电路的设计,实现了对露点温度的精密测量。实验结果表明,该系统稳定性好、测量精度优于±0.5℃。     

冷镜式露点检测系统的设计

为实现露点温度的精确测量,基于冷镜式原理设计了一套低成本、检测精度高、分析速度快、便携型的露点检测系统。该检测系统通过调节PWM占空比,实现对制冷器功率的有效控制。采用二次冷凝的露点检测方法,同时通过四线制铂电阻测温电路的设计,实现露点温度的精密测量。实验结果表明:该系统在-40~20℃露点测量范围内,露点测量精度优于±0.3℃。     

基于图像处理的SF6气体湿度测量方法的研究

提出使用冷镜式露点仪来测量SF6气体的湿度,并用图像处理的方法来代替传统的人工检测和光电检测方法。针对传统检测方法的不足,提出了基于小波包的纹理分析方法,并完成了系统的方案设计,通过仿真证明其优越性。     

高压充气站露点仪的改型设计

针对高压充气站上早期进口的冷镜式露点仪存在的不足,改型设计出阻容式露点仪,该露点仪具有响应快、精度高、智能化的特点。该文详细介绍了阻容式露点仪的工作原理、结构、部件选型。从性能测试的结果来看,露点仪的改型设计是成功的。     

基于ARM处理器的双加热湿度传感器设计

为消除地面气象探测领域中湿度传感器的温漂误差与沾湿误差,设计了一种双加热湿度传感器。利用24位低噪声模数转换器和电容-数字转换器实现温度和湿度的低噪声、高线性度测量,以Optidew Vision冷镜式露点仪作为标定仪器并结合遗传算法拟合修正温漂,使用交替加热的方法抑制沾湿误差。实验结果表明,该传感器的相对湿度测量精度可达±1%,并在6 min内将10%量级的沾湿误差降低至±1%。     

可控气氛中 CO_2的非水测定法

可控气氛中,CO_2和 H_2O 的测量,对于判断气氛的氧化—还原、渗碳—脱碳具有非常重要的意义。目前国内外已经有很多种仪表用来测量炉气中 CO_2及 H_2O 的含量。如红外线 CO_2分析仪、电导 CO_2测量仪、氯化锂露点仪、雾室露点仪、冷镜面露点仪和露点杯等。此外还有用于全分析的奥氏气体分析仪、和气相色谱仪。但是无论那种自动测量仪表都必须用基准仪器或标准样气来校对。露点杯广泛用来做为基准仪器校对各种露点仪。其结构简单,测量方便,稳定可靠。误差可达到±1℃。但是 CO_2分析仪表,目前还没有象露点杯那样一种基准校对仪器。只能用标准样气校对。可是标准样气一般厂无法配制和标定。本试验证明,CO_2的非水测定法可用来做为 CO_2分析仪表的基准校对方法,以及标定自己配制的样气。这点可以和露点杯相媲美。当加上一些附加装置后,还可以测量其他含碳气体(如 CO、CnH_2n及 CH_4等)。     

隔离段内激波位置对TDLAS测量结果影响规律研究

可调谐半导体激光吸收光谱技术(TDLAS)可以实现流场多组分、多参数的测量,具有其极强的环境适应性,可以用于超燃冲压发动机流场测量。为了研究超燃冲压发动机流场中激波对TDLAS测量的影响,利用计算流体力学方法(CFD)模拟了四种马赫数条件下的斜坡流场分布,采用双谱线测温法获得垂直于流道方向每条光线的平均温度。分析了温度测量结果与激波分布的关系,给出了TDLAS光学探头测量位置的建议。本文得到的结论对TDLAS工程应用和测量结果分析具有重要的参考意义。     

露点仪的研制及其应用

为测定气体中微量水分,设计了简易目视镜面露点仪,对仪器的结构参数、准确度和应用进行了研究。目视露点仪的测量误差为±1℃露点,最低安全检测下限达-110℃露点(相当于1ppb_v H_2O),可用作次级基准和工作基准.     

基于图像识别的精密露点仪

文中提出了基于图像识别的露点检测方法,介绍了这种露点仪的硬件组成,并对镜面结露（ 或霜） 状态的纹理特征进行了分析。     

基于冷镜式露点仪的湿度标准装置测量不确定度评定

高精度露点仪是一种高准确度的湿度测量仪器是国家湿度量值传递和国际比对通用的传递标准。而双压法湿度发生器能够连续输出恒湿气体,也是传递湿度量值的标准设备。本文讨论了高精度露点仪与双压法湿度发生器配套使用时,标准装置产生测量不确定度的多种因素。从双压法湿度发生器的工作原理出发,建立数学模型,并统一采用露点温度的形式,对本湿度标准装置的测量不确定度进行了评定。     

新的压缩空气露点温度换算图

给出了用于换算不同压力下压缩空气露点温度新的换算图,常压露点温度范围-70～10℃,压力范围为常压至1.0 MPa（表压）。图中压力单位采用我国法定计量单位。     

大口径SiC轻量化反射镜柔性带式支撑静摩擦影响

采用柔性带式支撑方式的大口径光学反射镜与支撑带之间的静摩擦力对反射镜面形精度影响较大,而且该影响难于直接定量测量。针对这一实际情况,考虑到温度变化将引起静摩擦力状态变化这一规律,建立了温度—静摩擦力间的关系表达式;接着,以反射镜所受静摩擦力与环境温度关系为基础,通过测量不同温度下的反射镜面形精度,间接推算出静摩擦力对反射镜面形精度的影响;以1.2米SiC轻量化反射镜为研究对象,利用干涉仪检测其柔性带式支撑机构在不同温度下的面形精度,并利用实测数据推导出温度—静摩擦关系的相应系数;最后借助ANSYS软件,对带式支撑机构的受力情况进行仿真分析。实测结果与仿真分析结果一致性较好,说明该研究方法可较为准确地推导出静摩擦力对大口径SiC轻量化反射镜面形影响。     

Multi-probe scanning system comprising three laser interferometers and one autocollimator for measuring flat bar mirror profile with nanometer accuracy

This paper describes a multi-probe scanning system comprising three laser interferometers and one autocollimator to measure a flat bar mirror profile with nanometer accuracy. The laser interferometers probe the surface of the flat bar mirror that is fixed on top of a scanning stage, while the autocollimator simultaneously measures the yaw error of the scanning stage. The flat bar mirror profile and horizontal straightness motion error are reconstructed by an application of simultaneous linear equations and least-squares method. Measurement uncertainties of the flat bar mirror profile were numerically evaluated for different installation distances between the laser interferometers. The average measurement uncertainty was found to be only 10 nm with installation distances of 10 and 21 mm between the first and second, and first and third interferometers, respectively. To validate the simulation results, a prototype system was built using an X–Y linear stage driven by a stepper motor with steps of 1 mm along the X direction. Experiments were conducted with fixed interferometers distances of 10 and 21 mm, as in the simulation, on a flat bar mirror with a profile known to an accuracy of λ = 632.8 nm. The average value of two standard deviations (95%) of the profile calculated over ten experiments was approximately 10 nm. Other results from the experiment showed that the system can also measure the yaw and horizontal straightness motion errors successfully at a high horizontal resolution. Comparing with the results measured by ZYGO's interferometer, our measured data excluding some edge points showed agreement to within approximately 10 nm. Therefore, we concluded that our measurement profile has an accuracy in the nanometer range.     

反射温度补偿法及其实验验证

为补偿环境辐射对红外测温的影响,根据红外辐射理论和红外热像仪的测温原理,提出了反射温度补偿法。介绍了该方法的原理,给出了该补偿方法的理论计算公式。相关实验显示,在被测物体周围存在高温物体的情况下,采用提出的反射温度补偿法可补偿高温物体的反射能量。红外反射镜的选取与被测物体的表面状况有关,若被测物体可视为朗伯体,则可选铝箔为红外反射镜;若被测物体为非朗伯体,则需选用与被测物体表面结构相似的材料为红外反射镜。经过反射温度补偿,能较为准确地得到朗伯体的表面温度,误差可控制在2%以内;该方法亦能够较大地提高对非朗伯体的测温精度,其误差不超过5%。这些结果表明该方法简单易行,精度较高,适用于大部分的红外热像仪。     

A humidity generator with a test chamber system

For the calibration of relative humidity hygrometers and dew-point hygrometers with an open sensor, a test chamber system was constructed and connected to a dew-point generator. The system includes several small chambers connected in series. By reversing the flow direction, humidity and temperature gradients in the test chamber system are monitored during calibration measurements. This paper reports the construction of the test chamber system and the improvements in the construction and the analysis of the dew-point generator. A full uncertainty analysis is presented. The expanded uncertainty of the dew-point temperature and the relative humidity with the coverage factor k=2 are from ±0.05°C to ±0.08°C and from ±0.1%rh to ±1.0%rh, respectively. Although the dew-point temperature range is from −40°C to +77°C, the limits for the temperature range of the test chamber system are −20°C and +60°C. The system was not tested with relative humidity values lower than 10% or higher than 95%.     

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.     

Luminescent Molecular Sensors for Assessment of Temperature Field in Machining

A new technique based on luminescent molecular sensors is utilized in these series of experiments for measurement of temperatures in material removal processes. 2-Dimensional machining of metals at low speeds and surface grinding configurations are used as the model experimental systems to understand the efficacy of this experimental technique. The experiments were conducted with a series of luminescent sensors and binder combinations for the temperature measurement. The luminescence of the sensor was measured through a charge-coupled device imaging camera, and intensive calibration exercises were performed on these sensors. Excellent agreement in the temperature fields measured through this new experimental approach and traditional infrared thermography is seen here. This technique offers the unique capability of allowing measurement of temperatures in the presence of a lubricant, akin to manufacturing conditions in situ. Extension of the technique to measure the temperature field at the tool-chip contact is described.     

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.