膜式燃气表内气流通道的优化思路

分析了影响膜式燃气表总压力损失的主要因素,提出了对表内气流通道的优化以降低表的总压力损失的主要思路.     

膜式燃气表压力损失分析

膜式燃气表是我国当前使用的主要燃气计量装置,以进出气口压差作为气体容积测量的依据,因此,气体压力的损失对燃气表精度的损耗必须予以认真的分析,本文从内部结构入手,对影响压力损失的各个环节、因素做出了深入的分析,对未来气体容积测量提出了新的思路。     

多表位燃气表检定装置表位差的成因及应对策略分析

多表位燃气表检定装置通过串联方式实现多台燃气表的同时检定，可显著提高工作效率。由于多表位燃气表检定装置表位差的存在，在一定程度上影响了计量检定结果的准确性。文章根据多表位燃气表检定装置使用过程中的实际经验，采用理论分析和试验验证相结合的方法，从压力损失、仪表误差特性、流场分布三个方面分析了造成表位差的原因以及应对措施，对消除多表位燃气表检定装置的表位差，保证燃气表串联检定结果的准确可靠具有实际指导意义。     

压力变化对燃气表示值误差的影响

本文通过理论推算和实验相结合,叙述了燃气表在多表位串联检定时因压力损失对各个表的示值误差所产生的影响.     

膜式燃气表产品质量国家监督抽查结果分析

近几年,国家燃气表质量监督检验中心(辽宁省计量科学研究院)与北京市计量检测科学研究院联合对全国范围内生产领域的膜式燃气表进行了国家监督抽查工作。膜式燃气表准确计量燃气流量,不仅对于节约能源、提高经济效益起着重要作用,也与广大人民群众的生产生活密切相关。燃气表的失准,直接影响到国家和消费者利益,同时密封性和压力损失等指标还会影响到人民的生命财产安全。最近十几年,行业产品质量有了大幅提高,随着几年国抽的开展,抽查合格率呈上升趋势,大部分企业产品质量保持较高水平。企业发展迅速,整体实力和国际综合竞争力显著增强。     

燃气表压力损失分析

通过生产实践中掌握的数据分析总结，简要介绍膜式燃气表的内部受力情况及压力损失。为旁路分流提供理论依据，并简单介绍以小流量表加旁路分流扩大过载量计量大流量的理论方法。     

气体介质湿度对膜式燃气表计量检定的影响

该文按照规程的要求,采用钟罩式气体流量标准装置对4台相对稳定燃气表在不同的湿度条件下进行检测,测得不同湿度下的压力损失、测量示值误差。结合管道中气体介质的相关特性理论进行比较分析,得出不同的湿度对燃气表检定的影响程度,为检定人员在检定过程中的判定提供参考依据,最后提出如何减弱湿度影响的措施。     

对燃气表气密性检定方法的一点建议

JJG577-2005《膜式燃气表》检定规程规定燃气表必须进行密封性试验,输入1.5倍最大工作压力,持续时间为3min,燃气表不得漏气,否则判定为气密性不合格。但是,在JJG577-2005中并未对检定原理或使用何种检定装置进行规定,由于基于"压力变化法"原理的检定装置价格适中、操作便捷,成为基层燃气表检定机构的首选。基于该原理设计的检定     

微热量式燃气表及其试验装置的研究

对家用燃气计量的创新型新产品———微热量式燃气表进行剖析,并对具有自主知识产权的微热量式燃气表温度试验装置进行研究。微热量式燃气表可实现流量、温度、温差、压力、密度等量的测量,并具有数据传输和计算功能,可用热能值对燃气进行结算。微热量燃气表试验装置是针对微热量式燃气表,在工况下进行温度变换检测的试验装置。     

极限温度条件下的膜表试验装置设计

为研究和优化极限温度状态下的膜式燃气表内部结构、材料及计量性能,文章研究设计了一种置入高低温程控箱内、检测极限温度下的膜式燃气表计量性能的试验装置。该装置采用临界流文丘里喷嘴作为主标准,罗茨流量计为参考标准。主标准由多个临界流喷嘴组成,可并联组合使用,喷嘴流出系数作相应的雷诺数修正。装置检测流量范围0.016~10 m3/h,适用温度范围-25~+55℃,装置扩展不确定度为0.5%(k=2)。可检测G1.6~G10各规格的膜式燃气表的流量误差特性和压力损失特性。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.