"V"型内锥式流量计的应用前景

长期以来,标准孔板由于其发展技术成熟、标准化程度高、结构简单等特点在过热蒸汽流量计量中得到非常广泛的应用.然而,孔板流量计存在着一些固有的缺陷,如流出系数不稳定、线形差、重复性不高、准确度受客观因素制约而无法达到设计要求、量程比小、压损大等.本文介绍"V"型内锥式差压流量计的工作原理,分析了如何解决孔板流量计的这些缺陷,并通过计算实例介绍"V"型内锥式流量计在节能方面的优点,最后介绍在恶劣条件下"V"型内锥式流量计是如何提供准确计量的.     

V形内锥流量计关键参数对流出系数的影响

将计算流体动力学仿真试验和实流物理试验相结合,剖析V形内锥流量计的流出系数特性,探索不同等效直径比β、前后锥角以及雷诺数等对流出系数的影响规律。湍流模型为RNG k-ε模型。针对100 mm口径,设计了β值分别为0.50、0.65、0.85,前锥角分别为40º、45º、50º,后锥角分别为120º、130º、140º,共27种组合的V形内锥体,仿真介质为水,温度为293 K。经过数值模拟试验,获得了27条内锥流量计流出系数特性曲线。为进一步验证仿真试验结果,在已有实流试验系统的基础上,建立针对V形内锥流量计的专用自动标定平台。两类试验数据比较发现：内锥流量计的流出系数不仅和雷诺数有关,还与等效直径比β及前后锥角相关。首先,β值越大,流出系数越小,且β值越大,流出系数更易受雷诺数的影响;其次,β值相同时,前锥角对流出系数具有决定性的影响,而后锥角对流出系数的线性度具有一定程度的影响;第三,较大的前锥角可减弱雷诺数对流出系数的影响。数值模拟试验预测平均误差约5%,最大值小于10%。     

V锥流量计与孔板流量计的比较

V锥流量计和孔板流量计同属于差压类流量计,但是由于内部结构不同,V锥流量计和孔板流量计各有特点。该文结合实例,对V锥流量计和孔板流量计的优缺点做了详细的比较。     

新型内外管差压流量计特性研究

针对现有各种流量计机械结构较复杂、节流方式对流体的扰动大、差压信号稳定性不足的缺点,设计了一种新型内外管差压流量计.运用三维CFD模拟仿真软件对其结构进行优化设计,通过实验验证了内外管差压流量计三维CFD仿真分析结果的可靠性.以内锥流量计作为参照对象,对内外管差压流量计的特性进行了对比分析,对比分析的结果表明,内外管差压流量计较内锥流量计压力损失小、压损比小、差压信号稳定性高.为了得到本装置的其他特性参数,又进行了大量的标定试验,实验结果表明测量精度、量程比等参数均满足技术标准的要求.     

光纤光栅内锥式流量计的研究

光纤光栅传感技术具有光纤传感技术的所有优点,内锥式流量传感器具有量程比大,压损较小,耐高温高压,要求前后直管段长度小的特点。将光纤光栅和内锥流量传感器结合组成了新型的光纤光栅内锥式流量计,介绍了光纤光栅和内锥式流量传感器的工作原理,光纤光栅内锥式流量计的组成。实验数据和结论。     

V型内锥流量传感器使用灵活性研究

利用数值仿真和实验相结合的研究方法,主要研究V型内锥流量传感器的使用灵活性和安装条件,针对50 mm口径的管道,通过长200 mm的渐扩和渐缩管与100 mm口径等效直径比分别为0.45/0.65/0.85 3种结构类型的样机进行连接,对50mm口径的管道进行常温水流量测量.设计并进行了基线和扩管2类实验,仿真预测结果和实验结论吻合,研究结果表明,在一定的前直管段安装条件下,其流出系数相对误差和附加不确定度满足性能指标要求.研究结果可为V型内锥流量传感器实际安装和使用提供一定的参考.     

V锥流量计的优化设计

主要目的在于探讨当前流行的“V”型内锥式非标准流量计的形状优化问题。采用计算流体力学软件FLUENT代替复杂繁琐的流量标定实验。对不同前后锥角节流装置进行了线}生J受、压损和压力梯度的对比分析,得出优化结果和各种规律性。采用三维建模,分析支撑杆对流量计性能的影响。使用有限元软件ANSYS,并结合FLUENT得出的流场条件,进行节流装置的结构刚度分析,得出最大应力区域和最大变形大小。以探讨其在大流场条件下的可靠性和准确性。     

内外管压差流量计的压力损失

针对现有流量计的节流方式存在压损大、扰动大以及差压信号稳定性不足等问题,设计了一个新型内外管差压流量计。在介质为水的情况下,对不同管径的六种模型进行Fluent仿真对比,结果表明异径管管径为10/20这一模型为最优模型。此外,在相同条件下,将该最优模型与等径比β为0.6的V锥流量计进行压损对比,得出该内外管压差流量计耗能仅为常规V锥流量计的不到10%的结论。     

上游双弯头对内锥流量计性能的影响

为提高对内锥流量计安装与使用条件的认识,开展了上游连续两个90°在同一平面成S型结构和互成垂直平面上弯头的数值仿真与实流实验研究.研制了实验样机一套,β值分别为0.45/0.65/0.85.利用平均流出系数相对误差及附加不确定度作为安装条件影响的主要评价标准,研究结果表明:对于β值分别为0.45/0.65/0.85的内锥流量计,在互成垂直面双弯头安装条件下所需最短直管段长度均为1D;在同平面S型双弯头安装条件下所需最短直管段长度分别为1D/1D/2D.     

湍流模型对双支撑型V锥流量计的适用性研究

本研究旨在探索一种适用于双支撑型V锥流量计仿真工作的湍流模型。以50 mm、100 mm、200 mm口径共计6种样机为研究对象,在常温常压条件下,以水为介质,雷诺数范围为1.0×104~29.9×104,分别采用标准k-ε、RNG k-ε以及SST k-ω3种湍流模型对其流出系数及其线性度误差指标进行仿真预测。为验证仿真准确度,同时开展实流实验研究,将仿真预测结果与实流实验进行对比,结果表明SST k-ω模型对于不同结构的V锥流量计的仿真线性度误差在0.04%~0.32%,与实流实验吻合较好。利用SST k-ω模型预测的流出系数与实验数据的平均误差为6.6%,优于经典的k-ε模型,更适用于双支撑型V锥流量计流场仿真和流出系数的预测。     

采用科里奥利质量流量计的流体粘度测量方法及影响因素研究

对流体在科里奥利质量流量计(以下简称科氏流量计)内的扭转运动状况进行了分析,得到运动速度与粘度的关系.通过对弯曲振动运动进行分析,结合流体运动及内摩擦力耗能情况,提出了一种新的粘度检测方法,导出了流体动力粘度与科氏流量计振动参数的关系,通过实验验证了方法的正确性.分析了影响粘度测量精度的部分因素.该方法简单、实用,拓展了科氏流量计的应用领域.     

高压电磁流量计电极结垢的解决方案

当测量介质具有易结垢的特性时,常规的高压型电磁流量计难以满足测量要求。为了解决此行业难题,本文对测量导管结构以及测量电极的形状做改进设计,由此可极大地延长此类工况条件下电磁流量计的无维护使用寿命。     

Performance tests of flowmeters for fuel consumption measurements in fishing vessels

In the study, we developed a flowmeter to be mounted on fishing vessels to measure their fuel consumption in the sea, and evaluated the performance of the flowmeter under the dynamic conditions of a fishing vessel. In order to analyze the dynamic behavior of the fishing vessel in the sea, dynamic motions (pitch and heave) based on the speed of the fishing vessel were obtained through simulation and field test. In the presence of vibration, the uncertainty of the ultrasonic flowmeter increased from 0.12% to 0.5%. The measurement error of the ultrasonic flowmeter also increased from 0.5% up to 2% when dynamic behavior motions (pitch and heave) increased with the speed of the fishing vessel. The results confirmed that the measurement errors of ultrasonic flowmeter were consistent at the same flow rate and speed of the fishing vessel in the dynamic test bed and sea field test. Additionally, to confirm the long-term stability of the developed flowmeter, a long-term test of the flowmeter was performed for three days in actual fishing conditions. The results indicated that the ultrasonic flowmeter developed in the study can measure the fuel consumption of an actual fishing vessel. To the best of the authors’ knowledge, this is the first study to measure the fuel consumption in the sea via mounting a flowmeter on an actual fishing vessel.     

Development of side wall type permanent magnet flowmeter for sodium flow measurement in large pipes of SFRs

Sodium cooled Fast Reactors (SFR) require measurement of liquid sodium flow in its primary and secondary circuits. For the primary system of the pool type concept of SFR design, flowmeters have to be immersed in sodium pool and require flow sensors which can withstand high temperatures up to 550 °C, nuclear radiation and chemically reactive sodium environment. Secondary circuits and safety grade decay heat removal (SGDHR) circuits of SFR need flow measurement in stainless steel (SS) pipes of diameter varying from 15 mm to 800 mm. For small pipes, flowmeters with permanent magnet flowmeter with ALNICO-V magnet assembly is the unanimous choice. Conventional permanent magnet flowmeters (PMFM) for large pipelines become bulky, heavy and have installation problems. For sodium flow measurement in large pipelines a few other alternate methods are considered. In the case of Prototype Fast Breeder Reactor (PFBR), which is at an advanced stage of construction at Kalpakkam, flow in the 800 mm diameter secondary main circuit is measured by means of a bypass flowmeter. Other sensors that could be deployed include eddy current flowmeters (ECFM), which are introduced into the pipe to measure flow velocity in the pipe, ultrasonic flowmeters and permanent magnet based side wall flowmeters. In permanent magnet based side wall flowmeter (SWFM), a permanent magnet block is mounted on one side of the large pipe and the magnetic field produced by the magnet penetrates through the pipe and interacts with the flowing sodium and induces an electro motive force (emf) proportional to the flow. This is a compact, cost effective and fairly accurate method for flow measurement in large pipelines of SFR circuits. SWFM is suitable for pipelines of 100 mm and above. In the present work a side wall flowmeter for 100 mm pipe is designed, manufactured, calibrated and tested in an existing sodium facility. Voltage signal developed in SWFM for different flowrates was simulated with three dimensional Finite Element Model (FEM) and validated with experimental results. Effect of asymmetric magnetic field on flowmeter voltage signal and dependence of flowmeter voltage signal on position of electrodes was also analyzed with model. The feasibility of use of this type of flowmeter for large pipelines of SFRs is demonstrated.     

基于LabVIEW的超声波相关法流速流量测量仪

讨论和分析了相关法超声波流量计的测量原理和数学模型，据此完成了相关法超声波流速流量测量虚拟仪器系统的结构设计和基于Lab-VIEW的软件设计，通过对该系统进行软件模块测试和系统信号仿真实验，论证了将虚拟仪器技术应用于超声波相关法流量测量领域的可行性，在相关法超声波流量计的理论研究和实验开发上具有一定的应用价值。     

影响科氏质量流量计振动管磨损的若干因素研究

黏性流体和被测流体中的固相颗粒对科里奥利质量流量计(以下简称科氏质量流量计)振动管内壁均存在磨损作用,振动管的磨损状态对流量计离线标定、故障诊断和基于振动的流体黏度的测量存在一定的影响.基于固相颗粒对管道的磨损机理,讨论了影响固相颗粒对流量计振动管磨损的几种因素.提出了减小振动管磨损速度和延长流量计使用寿命的措施建议.     

Effects of dissipative forces on Coriolis flowmeter readings

An indirect measurement method based on recording the phase difference of resonance vibrations of two symmetrical halves of the flow-carrying tube is used to quantify the mass flow rate of the current fluid in Coriolis mass flowmeters (CMFs). A variant of modeling the CMF vibration system is analyzed, which allows taking into account the influence of the dissipation of oscillations of a measuring tube with fluid flowing through it on the dependence between the mass flow rate of the fluid and the phase difference recorded by the sensor. The steady-state CMF vibration mode is considered as the result of the superposition of two principal vibrations of the measuring tube. The first principal coordinate corresponds to the deformation of the measuring tube along the lowest natural mode excited by an external driving force in the resonance mode. Vibrations of the other principal coordinate correspond to deformation in a natural mode corresponding to a higher natural frequency than the frequency of the exciting force. The relationship of the amplitudes of the principal coordinates is established on the basis of the gyroscopic coupling of the principal vibrations that occurs when a fluid flows through a tube. The coefficients of gyroscopic coupling are determined as a result of 3D finite-element simulation of the steady-state vibration mode of the measuring tube with a flowing fluid. The simulation is performed for five variants of the shape of the axis of the measuring tube, taking into account the distribution of the gyroscopic forces of the flowing fluid. Quantitative estimates of the influence of dissipative forces on the flowmeter readings are obtained on the example of dissipative forces of linear viscous friction. A comparison of the CMF simulation results for different tube axis shapes demonstrates how the phase shift arising in the vibration system is affected by the dissipation level and the proximity of the natural frequencies of the flowmeter measuring tube at a fixed mass flow rate of the fluid.