基于AMS2750标准对温度仪表校准要求和校准方法的探讨

AMS2750标准《高温测量》是热处理Nadcap特种工艺认证项目的重要内容.温度仪表作为高温测量过程中直接读取温度测试数据的设备,在AMS2750标准中有明确的校准和周期性控制要求.本文针对这些要求,对其中最常用的热电偶信号仪表在周期性校准中校准方法的选用及注意事项进行了研究,通过理论和试验验证了使用标准测试仪表内部...     

基于AMS2750E《高温测量》解决航空热加工设备系统精度超差的方法探讨

系统精度测试(SAT)不仅可以确定加热设备温度测量系统的误差,而且可以及时监控其变化趋势,预防由于加热设备温度测量系统的漂移造成设备温场均匀性(TUS)超出工艺要求的情况。航空热加工设备由于工艺传感器、工艺仪表内部误差等原因导致热加工设备的系统精度性能层次不齐,AMS2750E《高温测量》中共列举了5种系统精度计算示例,但是描述较为简单,会导致客户在选取AMS2750E《高温测量》中系统精度计算方法时存在误使用、错使用的情况。因此,本文首先对AMS2750E《高温测量》中列举的5种系统精度计算示例进行分析及相应的优缺点介绍,然后梳理出热加工设备系统精度超差的一些案例,通过对不同类型的超差情况进行分析,最后选择合适的系统精度计算方法。     

基于AMS2750D高温测试规范的温度巡检系统的设计

AMS2750D高温测试规范对热处理使用的热加工设备提出了更高的要求,本系统针对该规范对热处理设备的系统精度测试和温场均匀性测试的要求进行设计,实现了对系统精度的测试和温场均匀性的测试功能,并且按照规范要求实现了对测试用传感器、测试用采集器以及客户设备信息的管理等功能。     

航空发动机研制高温测量技术探讨

针对发动机高温测量的新要求,探讨了各种高温测量技术在航空发动机高温测量上的应用情况,并重点叙述了非标准分度热电偶、蓝宝石光纤测温技术、细线超声波测温技术和多光谱测温技术的发展和应用前景.     

热电偶温度自动测量及预测系统研制

在利用热电偶对石油、石化等场所的设备进行温度测量时,由于某些测试环境的特殊性,这就要求热电偶对测温点进行"瞬态"测量,而热电偶的热接点由于受热惯性的影响,短时间很难对测温点进行准确测量.考虑到热电偶测温的阶跃响应特性,利用计算机及A/D转换装置研制了热电偶温度自动监测系统并编制了温度测试系统"预测"软件,在对部分采样的数据进行线性回归后,可实现对温度信号的自动采集及对测量值的跟踪"预测",缩短了测试时间并降低了测试强度.     

高温热电偶保护套管材料

热电偶在工业生产和科学研究等领域中已成为应用最广泛的感温元件。热电偶保护管材料的性能影响热电偶长期稳定性、使用寿命等各项性能指标。在高温下工作的热电偶，对套管材料有更严格的要求。文章综述了高温套管材料的性能和分类及应用，阐述了高温熔体和高温流动粉体的温度测量的难点和研究现状。     

多轴运动机械臂及定位装置在热电偶自动检校领域的应用方案探究

近年来,对热电偶自动检校的研究主要集中在热电偶检定炉、电测仪表和控制软件的系统集成,而对检校中的抓取、推送、定位等研究较少,且人工操作定位精度低、效率低、存在高温安全风险等。本文总结了热电偶自动检校技术的现状,分析了将多轴运动机械臂和三轴运动定位装置两种类型的自动运动定位设备引入热电偶自动检校系统的技术方案,并进行测试验证,为提升热电偶检校的全过程自动化提供可行性方案。     

杯式高温合金均温块的实验研究

文章设计杯式高温合金均温块,与管式热电偶检定炉组合成恒温设备,用于工作用廉金属热电偶的检定。这种组合式恒温设备,经过大量的实验与传统的管式炉进行比较,其轴向温场、径向温场的温差减小了很多,而且与JJG 351—1996《工作用廉金属热电偶》检定规程的技术要求相比,其轴向温场温差减少1/2,径向温场温差减少1/4,提高了检定工作用廉金属热电偶整套装置的技术指标,减小了测量结果的不确定度。     

300℃以上热电偶量传体系问题分析及对策

针对目前300℃以上热电偶量传体系存在不确定度过大、计量能力不满足要求等问题,分析了高温共晶点和实用型固定点温度复现、纯金属热电偶温度测量和1500℃以上高温热电偶校准等技术的最新进展,提出基于固定点温度复现方法的新的量值传递体系设想,可大大减小热电偶量值传递的不确定度,使各级计量标准装置不确定度分布更为合理,能保证热电偶量值的逐级量传,满足科研生产对热电偶的溯源要求。     

廉金属热电偶校准装置测量水平的提高

新热电偶校准规范主要变化有:被测热电偶校准温度范围和长度、补偿导线技术要求,恒温设备技术要求,增加标准铂电阻做标准的计算公式,整百摄氏度热电势和温度对照表计算方法,方法上删除了退火,增加了补偿导线校准。还有一个最大变化是电测仪表选择与被测热电偶的等级对应起来。本文从对测量结果引入不确定度影响最大的几个因素分析,如何正确选择设备,如何提高测量准确度,如何实现新技术规范提出的使用设备的技术指标。     

About the Proper Wavelength for Pyrometry on Shock Physics Experiments

Usually one wants to measure the thermal radiance emitted by a hot-surface at a wavelength as short as possible, since the uncertainty in the true temperature due to unknown emissivity decreases with decreasing wavelength. Unfortunately the radiance also decreases with decreasing wavelength, and hence the signal-to-noise ratio becomes worse with shorter wavelengths. Depending on what temperature range is to be covered, a reasonable compromise can be found for most applications. When pyrometry is applied to shock physics experiments, there is an additional factor that has to be taken into consideration. Due to the nature of shock physics experiments, one has to deal with background light caused by flashes from air lighting up, high-explosive light, and muzzle flash from a powder gun, etc. In addition, even if the experiment is designed appropriately, there is often a temperature non-uniformity as well as thermal radiation from transparent anvils that are used to increase the interface pressure. In most cases, there is no engineering approach to minimize these temperature non-uniformities. The sensitivity to these non-uniformities increases with decreasing wavelength for the very same reason that the sensitivity to uncertainties in emissivity is increasing. This paper describes the above problems, deals with the problem of temperature non-uniformity in detail, and presents arguments why single-wavelength pyrometry in shock physics experiments can be very deceiving even in well designed experiments.     

Study of thermodynamic properties of carbon nanoparticles by the laser heating method

A new experimental approach to the analysis of thermodynamic properties of amorphous carbon nanoparticles synthesized via hydrocarbon pyrolysis behind shock waves is discussed. The proposed approach is based on the analysis of thermal radiation of nanoparticles heated by a laser pulse. The sublimation temperature of the carbon nanoparticles might be determined by the two-colour pyrometry; their sizes, by laserinduced incandescence; and the volume fraction of the sublimated substance, by the laser extinction method. The sublimation temperature depends on both the particle size and the temperature conditions of their formation. The value of surface energy for amorphous carbon nanoparticles was estimated.     

Werkstücktemperaturen bei der Zerspanung – Messung und Berechnung

Workpiece Temperatures in Machining - Measurement and Calculation Workpiece temperatures in machining of an austenitic steel, an aluminum alloy and copper have been both determined experimentally using infrared pyrometry and calculated numerically with a finite-difference-model. The influence of the cutting parameters such as cutting speed, cutting depth and rake angle on the workpiece temperature were investigated. Depending on the thermal diffusivity of the material an increase in cutting speed or cutting depth can either increase or decrease the maximum workpiece temperature. Increasing the rake angle always leads to decreasing workpiece temperatures.     

数据中心热环境评价指标研究

数据中心是集中放置并管理数据处理设备的空间,热环境是保障数据处理设备能够安全、稳定、连续运行的关键。这里在回顾并分析现有数据中心热环境评价方法的基础上,定义掺混指数参数,来评估数据中心空间发生冷热气流混合对设备安全性的影响,并评价其热健康程度。与现有的以设备平均进风温度为基础的评价方法不同,掺混指数侧重对热环境安全性的评价。通过考察掺混指数的空间分布,不仅可以了解数据中心气流组织的分布特性,还可以找出数据中心存在热环境安全隐患的位置,有针对性地加以改进。借助热量加权后的掺混指数,可以对不同规模、布局、气流组织模式的数据中心热环境质量进行直观比较,从而指导新数据中心的设计和已有数据中心的优化。     

Influence of high temperatures on a fiber-optic probe for temperature measurement

The use of optical fiber in a temperature probe or sensor for optical pyrometry in the 100-1000 °C range is affected by the low thermal stability of classical fibers. We have studied the different sources of perturbations induced by exposure to high temperature. Two specific fibers especially suited for a high-temperature environment were tested and compared. Low (100 °C/min) and very fast (100 °C/s) fiber heating was performed to evaluate its influence on the guided flux and the induced error on temperature measurement. The metallic-coated fiber shows a reproducible temperature error that can be predicted. This important result permits the development of an uncooled fiber probe for temperature monitoring in high-temperature environments such as aerospace engines.     

Noncontact temperature measurement of a falling drop

The 105-m drop tube at the Marshall Space Flight Center has been used in a number of experiments to determine the effects of containerless, microgravity processing on the undercooling and solidification behavior of metals and alloys. These experiments have been limited, however, because direct temperature measurement of the falling drops has not been available. Undercooling and nucleation temperatures are calculated from thermophysical properties based on droplet cooling models. In most cases these properties are not well known, particularly in the undercooled state. This results in a large amount of uncertainty in the determination of nucleation temperatures. If temperature measurement can be accomplished, then the thermal history of the drops could be well documented. This would lead to a better understanding of the thermophysical and thermal radiative properties of undercooled melts. An effort to measure the temperature of a falling drop is under way at Vanderbilt and Marshall Space Flight Center. The technique uses two-color pyrometry and high-speed data acquisition. The approach is presented along with some preliminary data from drop tube experiments. The results from droplet cooling models will be compared with noncontact temperature measurements.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

辐射测温区域的界定分析

文章讨论了谱色测温系统研究中,基于测温坐标系的辐射测温区域的界定问题。以线性发射率模型以及改进的单调发射率模型为基础,通过测温坐标系标尺的考察,分析了不同光谱发射率模型下的辐射测温坐标系所限定的辐射测温有效区域的规律特征;以实际应用中特定的谱色测温仪器为例,给出该仪器适用的辐射测温的理论区域,并用黑体实验进行了验证。     

Pyrometry inside an arc furnace using a ray-tracing correction for surface emissivity

A general method using a ray-tracing analysis has been developed to improve the accuracy of surface temperatures measured by pyrometry inside a furnace. This method allows temperature correction for enclosed non-ideal black-body surfaces, having temperature gradients, by taking into account the contributions from the reflected fraction of the pyrometer field-of-view. The development has been made possible by the recent availability of internal furnace scanning pyrometry technology for complete temperature profile measurements inside furnaces. The correction method can be expressed in terms of the solution of a square matrix having a dimension corresponding to the number of spatially resolved points in the temperature profile, with the number of non-zero elements depending on the number of field-of-view reflective surface bounce points used in the analysis. The utility of this method is demonstrated for the correction of 19-point temperature profiles measured inside a dc arc furnace. Reflective contributions from two, three, and four field-of-view surface bounce points are considered. Generally, the lower the surface emissivity and the higher the temperatures, the more bounces needed in the analysis. It is shown that there can be significant corrections to internal furnace temperatures measured by pyrometry when temperature gradients exist.     

表面淬火等离子体束温度及宽度测量方法

等离子体表面淬火技术是一种新型表面处理技术。该技术通过等离子体发生器产生高能等离子体束作用于金属材料表面,使材料表面温度快速升高超过相变温度,再依靠自身快速冷却达到淬火效果。目前在缺少对淬火过程中等离子体束温度的测量方法。本文研究出一种数字图像处理与双色比色法相结合的方法能够测量出等离子体束在表面淬火过程中的温度。实验结果显示本方法可以有效观测到淬火过程中的等离子体束温度与宽度及其变化,为等离子体表面淬火技术提供了支持。     

The 1990 NIST Scales of Thermal Radiometry

Following an absolute NIST measurement of the freezing temperature of gold and the adoption of the International Temperature Scale of 1990 (ITS-90), NIST has adopted new measurement scales for the calibration services based on thermal radiometry. In this paper, the new scales are defined and compared to the ITS-90, and the effects of the scale changes on NIST measurement services in optical pyrometry, radiometry, and photometry are assessed quantitatively. The changes in reported calibration values are within quoted uncertainties, and have resulted in small improvements in accuracy and better consistency with other radiometric scales.