低温涡街流场特性数值仿真研究

通过FLUENT对典型的涡街流量计在低温流体中的卡门涡街流场特性进行理论分析和数值仿真,并与常温工况下的涡街流场进行比较,分析低温流体的旋涡分离过程,得出流量与涡街分离频率的对应关系.研究表明,数值仿真方法成本低,适于模拟复杂流场,为低温涡街流量计在涡街发生体形状和压电振动传感器采样位置的设计与优化提供理论依据.     

涡街流量计在能源计量中的应用探讨

文章阐述了涡街流量计在集中供热的园区企业能源计量中的应用,通过分析涡街流量计的工作原理,总结涡街流量计在不同介质的流体使用特性,重点阐述了在气体和蒸汽流量测量中注意事项。     

涡街流量计在蒸汽、空气及水介质下的仿真分析

利用计算流体力学数值计算仿真方法,对涡街流量计在蒸汽和空气两种气体流体介质下进行了仿真分析,与水为介质的液体流场进行分析比对,发现由于受气体可压缩性等物理特性影响,涡街流量计的流场存在差异,影响了涡街流量的计量性能,最终引起仪表系数在不同介质条件下存有偏差,并对流场分析结论进行了实验验证。     

弯管流量计在供热计量中的应用分析

文章介绍了弯管流量计在我公司热电机组一抽蒸汽出口计量的应用情况、弯管流量计在供热计量中的独特优点,并结合流体计量的理论对弯管流量计与孔板流量计、涡街流量计的性能差异作一简单分析。     

涡街流量计所受干扰分析及排除

一、引言涡街流量计的应用范围愈来愈广泛 ,并受到用户的欢迎。因为涡街流量计使用比较方便 ,量程比宽 ,压力损失小 ,更换检测元件无需重新标定 ,既有就地指示 ,又可进行运传 ,也省去了差压变送器 ,充分显示了它的优越性。涡街流量计是通过被检测介质产生的旋涡而产生脉冲信号 ,易受干扰 ,在投运中常遇到一些问题。本厂装了 10台ＬＵＧＢ系列涡街流量计 ,测量氯气和氯甲烷的流量 ,开始运行不正常 ,后来通过一段时间分析、改进、基本上能正常运行 ,本文介绍其投运过程。二、工作原理涡街流量计又称卡门旋涡流量计 ,它是利用流体自然振荡的原…     

测压、测温元件对涡街流量计计量的影响

在对涡街流量计检定时,可能需要使用测压、测温元件去测量流经流量计的流体温度、压力,以保证流量计计量的准确性。然而部分插入式测压、测温元件是需要插入流体中,这样相当于在流量计的涡街发生体后面的旋涡中在放置了一钝体,此钝体可能会影响已经形成的旋涡,也可能会影响旋涡脱落的频率,从而有可能影响流量计的计量性能。     

孔板流量计与涡街流量计测量蒸汽流量的误差分析

水蒸汽是石油、石化、冶金、电力、造纸、制药等企业生产过程中不可缺少的一种二次能源,由于其特殊的物理特性,对其进行质量流量计量将不同于其它流体.文章主要是对用涡街流量计和孔板流量计进行蒸汽质量计量时所产生的误差进行一个对比分析.     

涡街流量计的原理,安装及改进

涡街流量计的原理、安装及改进１简单原理与测量方式涡街流量计之所以能测量，是基于卡门涡街理论。所谓卡门涡街现象，就是在流体中设置三角柱形漩涡发生体，流体流经发生体，则从发生体两侧交替地产生有规则的漩涡，称为卡门漩涡，漩涡在发生体下游非对称排列。如图１设...     

涡街流量计在蒸汽测量中仪表系数的修正方法

本文简述涡街流量计的基本原理，分析了温度对传感器仪表系数的影响，给出了在测量高温流体时仪表修正的实用公式。     

涡街流量计选型中测量上/下限的核算

正多年工程实践证明,选型是用好涡街流量计的关键环节,而选型过程中对于测量上/下限的核算则是重要基础,抓住了这一基础环节,该流量计不失为一种性能卓越的流量计。选型过程中,首先是根据工艺要求选择正确的口径规格,以确保流体流量介于所需准确度等级下、流量计的最大及最小流量测量限之内;因为线性度与测量范围及雷诺数相关,流体的雷诺数不可超限;涡街流量计为速度式流量计,应采用工况流速进行测量范围的性能对比。     

双锥流量计实验研究与计算模拟

提出的双锥流量计是一种新型的差压式流量计.采用CFD软件Fluent模拟计算管内流体绕流双锥节流件结构时的流动情况,得到流量与差压信号之间的关系.对几种特定直径比β为0.4,0.5,0.6的双锥流量计进行实验研究.结果表明,实验与模拟基本一致,并且具有量程比大,直管段要求短,压损小等优点.     

多通道超声波气体流量计的数学模型

在超声波气体流量计的实际测量中,多种不同因素引起流量测量的误差,其中流场分布是引起误差一个很重要的原因。采用多通道流量计可以较好地克服这一影响。但由于流体具有粘滞性,管道截面上不同半径处的流体速度各不相同,所以声通道测量的流体平均流速与实际管道中流体的面平均流速仍存在差异。对多通道超声波气体流量计的数学模型进行了研究,通过理论计算多通道超声流量计各通道的动力校正因子及权系数,由测得的若干超声传播路径上的线平均流速计算得到面平均流速,从而提高流量的测量精度。并将此应用于研制的四通道流量计中,进行了实验验证。     

TDC超声流量计设计中的同频噪声处理

介绍了一种基于TDC（Time—to—Digital Converter）传输延迟线法的时差法外夹式V型超声流量计的设计方法,分析了设计中存在的同频噪声的生成原因以及它对测量精度的影响;对同频噪声信号和待测信号进行建模,运用最大似然估计法对噪声的幅度、相位参数进行估计,给出同频噪声的消除算法;在同频噪声消除后,对待测信号的幅度、相他参数进行估计,利用估计结果给出TDC测时方法是否可用的判决函数,并给出TDC测时方法无法使用时的解决方案.     

前后直管内径对涡轮流量计的影响研究

涡轮流量计在安装和使用过程中往往存在直管段口径与流量计通径不完全一致的现象。选取CL系列和LWGY系列涡轮流量计,在燃油动态流量标准装置上进行了上下游直管段不同口径条件下的校准试验,从而得到直管段口径对涡轮流量计K系数的影响。试验证明,直管段口径所引入的误差不可忽视,因此在使用或校准涡轮流量计时应务必保证直管段口径与流量计通径一致。     

Influence of Normal Fluid Disturbances on Interactions of Solid Particles with Quantized Vortices

Two-dimensional Lagrangian trajectories of the inertial particle in helium II are analyzed in the vicinity of the triple-vortex structure, i.e. the superfluid vortex and the normal dipole-like vortex structure induced by the mutual friction. It is shown that the vortices in the normal fluid can deflect the particle which otherwise would have collided with the superfluid vortex and, provided that the relative velocity of the particle and the vortex is not too large, would have been trapped by it. A geometrical impact parameter, which in the considered two-dimensional model, plays a r?le of the cross-section of particle–vortex collision, is determined and calculated as a function of temperature, externally applied superfluid velocity, and the Stokes number defined by the size of the local vortex structure, superfluid line velocity, and particle viscous response time.     

A modified agglomeration kernel model used for particle agglomeration

Particle agglomeration in turbulent flows is an extremely complex process, and comprehensive study is beneficial to the development of turbulent agglomeration technology. The effects of vortex generator structure on particle agglomeration were investigated based on a combined computational fluid dynamics (CFD) and discrete element method (DEM) approach, including the geometric size, spanwise pitch, longitudinal pitch, row number, arrangement and form of the vortex generator. A dimensionless parameter K (the ratio of vorticity to strain rate, abbreviated as K) was defined to evaluate the agglomeration ability of the vortex generator, and the traditional agglomeration kernel function was modified by adding a correction coefficient α (agglomeration efficiency). By comparing the traditional agglomeration model and the modified agglomeration model with the experimental results, it showed that the modified agglomeration kernel model can simulate a result closer to the real agglomeration process.     

Numerical investigation of gas-particle hydrodynamics in a vortex chamber fluidized bed

Gas-particle hydrodynamic behaviour inside a vortex chamber fluidized bed is studied numerically with respect to different design and operating conditions. A three-dimensional computational fluid dynamics (CFD) model of a cylindrical vortex chamber is developed. Simulations are carried out with particles and without particles. In order to understand the gas-particle flow behavior velocity distribution, particle volume fraction distribution, radial pressure distribution and axial pressure distribution inside the vortex chamber are analyzed in detail. Particles of different diameters are used and its effect on the gas-particle flow behaviour is studied. Design parameters like the number of gas inlet slots and slot width are varied and their impact on the hydrodynamics of the vortex chamber is investigated. The numerical model is validated by comparing the numerical results with experimental results reported in literature.     

Equation for Self-Consistent Superfluid Vortex Line Dynamics

Turbulence in helium II takes the form of a disordered tangle of quantised vortex line. The existing equation of vortex dynamics used by Schwarz and others to model the evolution of the vortex tangle does not distinguish between the large scale normal fluid velocity and the local variation of the normal fluid velocity introduced by the presence of quantised vortex lines. We derive a new vortex dynamics equation which allows the local normal fluid velocity to be determined by a modified Navier–Stokes equation. Together, the two equations form a self-consistent model to determine the coupled evolution of the normal fluid and quantised vortices.     

Free convection heat transfer in horizontal channels and over a horizontal surface

Free convective heat transfer of a fluid in horizontal channels and above a horizontal surface is theoretically analyzed. The interaction of the fluid with the channel walls may be divided into two parts: formation of vortex flow cells, and heat transfer in the induced flow over the walls.     

充液管路系统中阀门流噪声的研究

用二方程模型封闭的雷诺平均N-S方程组,对水管路系统中三种常见阀门的三维分离流动进行数值模拟.模拟结果表明,随着蝶阀、闸阀和球阀开度的减小,流体在蝶阀背面、球阀阀门内外分别形成两个方向相反的漩涡,闸阀的漩涡出现在挡板与管道的壁角处,并且漩涡在阀门下游逐渐消失.同时实验表明,阀门下游的流噪声大于阀门上游的流噪声,涡声是阀门噪声的主要来源.