LNG加气机检定装置流量计性能分析

为了找出影响液化天然气(LNG)加气机检定装置的主标准器——质量流量计的测量准确度的主要因素,为进一步提高检定装置的计量性能提供理论依据,通过CFD软件对流量计测量管内流场进行数值模拟.通过数值模拟计算,得出不同工况条件下流量计内部流场的分布情况,通过分析流量计的工作压力、质量流量和温度等参数对流量计准确度的影响,提出提高流量计的计量性能的办法.     

90°弯管内示踪气体混合均匀性的数值模拟与实验研究

示踪气体在管道内的混合均匀性,对示踪法测量气体流量的准确性或者在线校准管道气体流量计的校准精度影响很大.在直径为300mm的90°弯曲管道内,对示踪气体CO与空气的混合情况进行了数值模拟研究,并与实验结果进行了对比分析.结果表明,五孔释放混合效果明显要好于单孔释放,且五孔释放时弯管下游9D处示踪气体与空气混合基本均匀.数值模拟结果和实测结果基本吻合,可为示踪法测量气体流量和在线校准管道气体流量计提供参考.     

刮板流量计检定温度和流量计系数的相关性讨论与应用

目前国内管道一般以刮板流量计作为体积交接计量器具,采用在线检定方式,以流量计系数法进行动态计量交接.流量计系数由周期检定产生,受检定期间的检定温度影响.本文使用散布图和相关系数法,就刮板流量计检定温度和流量计系数的关系进行了分析,并对流量计在检定温度方面应当注意的问题给出了一些建议.     

V锥流量计的CFD数值模拟与分析

运用计算流体力学(CFD)方法,对V锥流量计进行了数值模拟,得到了锥体上的压力和速度的详细分布情况,并对其进行了分析.数值模拟得到的压差值与试验结果能较好吻合,这对V锥流量计的优化设计具有一定意义.     

便携式超声波流量计在线检测试验研究

为解决部分企业选用的流量计难以离线送检,襄阳市计量检定测试所采用便携式超声波流量计对其进行在线检测。基于该中心的油流量标准装置,利用PF300plus便携式超声波流量计与标准表进行比对试验,探讨并验证使用便携式超声波流量计对管道流量计进行在线检测的可行性,并着重研究两种传感器安装方法对不同管径的适用性。     

燃气单钝体绕流流场特性的数值模拟研究

应用基于有限体积法的FLUENT6.1计算软件对管道中单钝体的燃气绕流现象进行了仿真研究,即对实现管道燃气流量计量的DN200mm新型宽量程流量计的流场进行了数值模拟,就燃气计量管道中漩涡发生体的漩涡脱落频率与实测数据进行了比较。结果表明,数值计算结果与实测结果具有很好的一致性,从而提出了在新型燃气流量计的研制中可以应用数值模拟方法来优化流量计结构设计的结论。     

段塞流对弯管瞬态冲击的三维CFD数值模拟研究EI北大核心CSCD

在核电站和火电站管路系统中,来自上游的高压蒸汽可使管道中的凝结水团(段塞)加速运动,并在弯管、三通、阀门等非连续部位产生剧烈的冲击力,从而对管道造成严重破坏,影响电站的安全运行。针对管道中段塞运动的高维动力学特性,文章运用CFD对单个段塞在含弯头空管中的运动与冲击过程进行了三维数值模拟研究,并将数值模拟结果与文献中的物理试验结果进行了比较。结果表明,CFD模拟的冲击压力时程曲线及压力峰值都与试验结果具有良好的一致性。同时,基于理论分析,提出并详细论述了冲击过程中压力随时间变化的三种趋势,并通过数值模拟验证了其正确性;通过分析段塞长度的时程变化,得到了段塞的质量脱落率曲线;基于数值模拟得到的段塞瞬时冲击速度,验证了简化的冲击压力理论计算方法,发现理论计算值与试验以及数值模拟结果基本吻合。这证明了CFD数值模拟的准确性以及冲击压力简化计算方法的合理性,二者在实际工程应用中具有指导意义。     

大口径水流量计的在线检定方法和注意事项

一、大口径水流量计在线检定的必要性及检定方法和标准表选型 在水库供水和自来水公司供水中大量使用的是公称口径大于DN300的大口径水流量计，此类流量计用于贸易结算，涉及的数量和金额巨大，根据《计量法》的规定．对其必须进行强制检定。由于大口径水流量计多数是电磁流量计或插入式超声波流量计，仪表结构大都为法兰连接或者是插入管道，只在停流时才允许拆卸，且拆装和运输送检十分麻烦；另一方面，此类流量计的现场工作条件与实验室校验的工作条件相差很大，流量计准确度偏离无法确定。因此，在线检定大口径水流量计十分必要。     

原油流量计在线检定/校准技术研究

论述了适应于原油生产特点的原油外销与交接流量计在线检定/校准技术,解决了大型原油流量计拆卸送检带来的费时费力、生产成本高、检定长期积压等问题,消除了原油介质对流量计检定结果的影响,延长了流量计的使用寿命,实现了原油外销、交接流量计在线周检率100%的目标。     

安装条件对超声流量计计量准确性影响初探北大核心CSCD

采用实验测试与数值模拟相结合的方式,研究了不同安装条件对超声流量计计量准确性的影响。实验结果表明锈蚀直管段及是否安装整流器以及安装哪种整流器对流态及计量结果有较大影响,数值模拟结果佐证了实验结果。为保证贸易交接准确可靠,超声流量计检定和现场使用安装条件应符合标准要求,若不能做到一致时,建议一并送检流量计配套附件。     

利用CFD获取超声流量计截面速度分布

 通过CFD技术在超声波流量计设计过程中的引入,为流量系数的获取提供了新的途径.通过对特定管道的理论计算表明,采用CFD技术获取的管道内部流型完全可以与试验数据吻合,有助于超声波流量计应用场合流量系数曲线的获取及其精度的保证.     

肘形挠性接管冲击特性试验研究

针对肘形挠性接管特殊结构形式,提出了两根相同挠性接管对称或反对称安装测量方案,用于测量其不同坐标方向上的冲击特性。采用阶跃松弛释放法,测量了不同工况下肘形挠性接管冲击振荡的固有频率与阻尼比,从被测试件对应工况时机械阻抗测试曲线中获取了肘形挠性接管的端部等效质量,用于冲击刚度的计算,进而计算出阻尼系数。通过分析不同工况下冲击特性的变化规律,得到了一些初步结论,为抗冲击设计和计算提供了参考依据。     

环形管流量计测量气液两相流研究

提出了一种基于环形管流量计的新型气液两相流流量测量方法.设计了多圈环形管流量传感器,通过对多圈环形管的水平直径上和垂直直径上四个差压信号进行分析,建立了不同位置差压信号与总体积流量和总质量流量的关系模型,并由此获得气液两相流的混合密度,实现了气液两相流分相流量的测量.     

35MPa/70MPa加氢机用科氏质量流量计阻力特性数值模拟与实验研究

针对科氏质量流量计对介质的阻力在35MPa/70MPa加氢机加注主管路流动总阻力中占比最大的问题,进行了科氏质量流量计在加氢机运营工况下的数值模拟与实验研究。建立了包括入口段、测量管和出口段3个流动区域的科氏质量流量计的数学模型,在加氢机质量流量1~9kg/min时进行了数值模拟分析研究,得到了科氏质量流量计的压力分布和流速分布,根据压力和流速计算得到了科氏质量流量计阻力系数。计算结果与实验结果的对比表明两者能够较好吻合,阻力系数相对误差小于5%。     

Experimental and numerical analysis of a variable area ratio steam ejector

In the present paper, experimental and CFD results for a 5 kW capacity steam ejector with variable primary nozzle geometry are presented and compared. The variable geometry was achieved by applying a movable spindle at the primary nozzle inlet. Operating conditions were considered in a range that would be suitable for an air-conditioning application, with thermal energy supplied by vacuum tube solar collectors. The CFD model was based on the axi-symmetric representation of the experimental ejector, using water as working fluid. The experimental entrainment ratio varied in the range of 0.1–0.5 depending on operating conditions and spindle tip position. It was found that the primary flow rate can be successfully adjusted by the spindle. CFD and experimental primary flow rates agreed well, with an average relative error of 7.7%. CFD predicted the secondary flow rate and entrainment ratio with good accuracy only in 70% of the cases.     

Failure analysis and prediction of pipes due to the interaction between multiphase flow and structure

Frequently found in piping, erosion failures may lead to the leakage of pipes and even damage the whole system. Erosion is a form of material degradation that involves electrochemical corrosion and mechanical wear processes encountered on the surface of metal pipes. Research on the erosion–corrosion mechanism indicates that the erosion mainly results from the interactions between the pipe surface and the fluid traveling along the surface. This paper studied multiphase flow induced erosion–corrosion in pipes, mainly focusing on the interactions between the multiphase flow and the structure. In order to evaluate the erosion effects caused by the flow and the coupled dynamics, the multiphase flow regimes, flow dynamics parameters and the distribution of phases on different positions of the boundary layer in REAC pipe inner surface were analyzed. The CFD simulation results proved that the location, rate and the extent of erosion failures on the pipe surfaces can be well predicted, as compared with actual instances. Practically, this method can be used in optimizing the design of the inner sleeves of pipes.     

基于CFD的双声路超声水表研究

基于时差法的超声水表在中、大口径的水流量测量中,存在超声波信号易受外界干扰以及小流量的测量重复性较差等问题.针对以上问题,本文设计了具有缩径结构的管路模型.其次,通过CFD数值仿真研究了缩径管路模型在低流速下的流场分布情况.最后对本文设计的双声路超声水表样机进行了相关试验.试验结果表明,本文设计的管路模型有效提高了超声...     

Patient-specific analysis of post-operative aortic hemodynamics: a focus on thoracic endovascular repair (TEVAR)

The purpose of this study is to quantitatively evaluate the impact of endovascular repair on aortic hemodynamics. The study addresses the assessment of post-operative hemodynamic conditions of a real clinical case through patient-specific analysis, combining accurate medical image analysis and advanced computational fluid-dynamics (CFD). Although the main clinical concern was firstly directed to the endoluminal protrusion of the prosthesis, the CFD simulations have demonstrated that there are two other important areas where the local hemodynamics is impaired and a disturbed blood flow is present: the first one is the ostium of the subclavian artery, which is partially closed by the graft; the second one is the stenosis of the distal thoracic aorta. Besides the clinical relevance of these specific findings, this study highlights how CFD analyses allow to observe important flow effects resulting from the specific features of patient vessel geometries. Consequently, our results demonstrate the potential impact of computational biomechanics not only on the basic knowledge of physiopathology, but also on the clinical practice, thanks to a quantitative extraction of knowledge made possible by merging medical data and mathematical models.     

天然气能量测量不确定度评定

文中以天然气长输管道中超声流量计计量系统为例,通过分析系统配套的超声流量计、温度变送器、压力变送器、流量计算机以及在线气相色谱仪等计量器具对能量测得值不确定度的贡献,分别对其引入的不确定度进行了探讨,分析了能量测量的不确定度评定方法。     

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the pipe's wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.