关于蒸汽测量方面的经验介绍

蒸汽流量受蒸汽状态以及蒸汽流量计的设计、安装及密度补偿等各种因素的影响,其计量精度,特别是在小流量用汽的情况下,存在计量偏大或者计量偏小,经常会产生计量纠纷。为了解决此类计量纠纷,笔者总结了一些经验,这些经验也确实解决了计量纠纷带来的麻烦。该文主要介绍流量计安装经验及蒸汽流量的密度补偿。     

涡街流量计在蒸汽计量中的特性研究

蒸汽流量量值体系的溯源是保证蒸汽流量测量准确的关键。本文基于流体力学、热力学以及涡街流量计旋涡的产生机理,分析不同介质对涡街流量计的计量特性的影响,介质粘度的不同导致了三种介质测试下雷诺数的不同,影响到斯特劳哈数差异。但对涡街流量计的仪表系数影响不大,可忽略其影响。介质粘度的不同会导致流量范围的不同。该分析将有利于提高涡街流量计测量蒸汽流量的计量准确度。     

蒸汽流量计的检定

由于节能和经济核算的需要,目前有些厂家正在试制供测量蒸汽流量的专用流量计。这种流量计具有压力定值补偿或自动补偿,能很好的克服蒸汽压力变化产生的误差,对提高计量精度有着重要的意义,是一种比较理想的蒸汽计量仪表。但是,蒸汽流量计的标定是较为困难的。本文介绍的一种标定蒸汽流量计的方法,可供生产蒸汽流量计的单位及有关人员参考。     

石油流量计的设计

为了改善传统石油动态计量装置误差大,测量精度低,劳动强度大等问题,进行了石油流量计的设计。石油流量计通过对不同流体流量的精确测量和定量计量控制,实现了流量计量的自动化;同时对不同流体可以进行流量系数的更新,也可以在计量系统的输出端,通过切换阀与标准体积管连接,由键盘输入实际流量值,对流量系数进行修正,保证流量计量的精准、可靠。实验表明,该装置的测量误差小于0.525%,达到了使用要求,可以用于瞬时流量计量、累积流量计量和定量计量控制。本装置计量精度高,操作简单、使用方便,可以用于需要进行流量计量的场合。     

一种新式差压流量计的设计与应用

该文分析了影响蒸汽流量准确计量的主要因素,介绍了传统的蒸汽流量计如孔板流量计和涡街流量计的使用局限性,详细介绍了一种基于皮托管原理的新式差压式流量计的设计原理、结构特点及其标定方法,通过实例给出了典型蒸汽工况下选择流量计的考虑因素,以及应用这种新式差压式流量计的选型和计算过程。     

饱和蒸汽计量常见的问题及改进方案

在流量计量中饱和蒸汽计量是个难点,为了准确的计量饱和蒸汽本文从饱和蒸汽的特点、特性及计量检测装置对饱和蒸汽计量的影响入手提出了一些提高饱和蒸汽计量准确性的建议和方案。     

基于CFD仿真的差压微小流量计设计

微小流量计量在能源计量、精准医疗等多种场合中有着广泛应用,但是目前测量微小流量的流量计普遍存在准确度低等问题.因此,文中以精准测量微小流量为目的,设计了差压式微小流量计.借助计算流体动力学(computational fluid dynamics,CFD)仿真技术,设计了流量计的基本结构.通过实流实验验证了设计方案的可...     

浅谈高流速蒸汽对涡街流量计的影响

涡街流量计在计量蒸汽时,管内蒸汽流速必须限定在一个范围内,涡街流量计才能正常工作。有人使用一些看似无意其实违法的手段,致使下游的压力骤降,导致蒸汽流速超过涡街流量计测量流速上限,涡街流量计不能正常工作,计量严重偏小。最后提出采用加装限流装置的方法来控制蒸汽流速以保证涡街流量计正常计量。     

低功耗无线燃气表的研制

针对天然气流量计量中工作环境对其计量影响较大的问题,提出了一种温压补偿型燃气表设计方案。计量中将工况下的流量体积转换成标况下的流量体积,并通过无线的传输实现了在线流量监测,最终的样机实验结果表明,该燃气表的误差小于±1.5%.     

基于多普勒原理的管道流量测量系统的设计

流量计量是计量科学与技术的重要组成部分,且应用广泛.与其他类型流量计相比,超声多普勒流量计具有非接触、高分辨率以及对流体的压力、粘度和温度因素不敏感等优点.文中采用多普勒法实现流量测量,建立了流速、体积流量计算模型,采用了以数字信号处理器(DSP)为信号处理核心的超声多普勒流量测试系统的设计方案.对测试系统部分硬件电路进行了介绍,并分析了主程序设计.对测试系统进行了调试研究.结果表明,该系统达到了拟定5％的精度要求,且稳定性较好.     

Energy metering system for high quality saturated steam

For accurate measurement of steam flow rate, the dryness fraction has to be included in the flow rate calculation; the dryness fraction is also a parameter that often needs to be monitored for effective process control and for condition monitoring of the plant. It is notoriously difficult, however, to measure dryness fraction easily and accurately. In this paper, an energy metering system which measures the steam quality, mass flow rate and thus the energy of the steam is proposed and tested. The system consists of a separator and condensate flowmeter followed by a steam flowmeter; the output signals of these devices are fed into a microcomputer which contains the characteristics of the devices and formulations for steam properties. Testing of the energy metering system showed that the average differences between the displayed output of the system and the values obtained using a condensate weightank was about 0.22% for the dryness fraction and 1.05% for the saturated steam flow rate.     

蒸汽介质分析及蒸汽计量系统综述

本文从蒸汽介质入手,介绍了蒸汽的产生、性质、分类及用途;进而提出了蒸汽用量计量问题;重点论述了蒸汽计量系统的工作原理和校准方法;最后给出了未来蒸汽计量的主要研究方向。有助于加深行业人员对蒸汽及蒸汽计量知识的理解和应用。     

舰载机蒸汽弹射器热力学仿真分析

舰载机依靠蒸汽弹射器输出的弹射力推动其达到起飞速度,因此控制弹射力的输出尤为重要,为了分析研究蒸汽弹射器对弹射力输出的控制,本文阐明了蒸汽弹射器中控制蒸汽流量的发射阀结构和基本工作原理,提出发射阀中测量杆的位移与流通面积的计算方法,从而求解蒸汽流量,并结合蒸汽弹射器的热力学变化过程进行数学建模。以C13型弹射器为例进行仿真,通过实验数据的对比分析,说明了本文所建模型的可行性和正确性,其仿真结果可为蒸汽弹射器的设计与试验提供有益参考。     

Assessment of combined V/Z clamp-on ultrasonic flow metering

Clamp-on ultrasonic flow metering can provide a non-invasive and portable means for flow measurement. However, it indicates flow rates with low measurement accuracy at low flow velocity in pipe flows. Typical accuracy of the clamp-on ultrasonic flow metering amounts as low as ±1% if the flow velocity in a pipe is greater than 0.5 m/s. The accuracy can be increased greater than ±2% if the flow velocity is lowered smaller than 0.5 m/s. Inner pipe diameter can be also an influential factor in flow metering when the exact value of the inner diameter is not known. The inner pipe diameter cannot be found if the pipe is too large to measure or if there are erosions or adhesions on the inner pipe surface due to small particles in the flow. These shortcomings of the clamp-on ultrasonic flow metering can be overcome by combining two transit times along a Z-shaped and a V-shaped ultrasonic path. This technique is termed combined V/Z clamp-on ultrasonic flow metering. With the water flow standard system in KRISS, this combined technique exhibited intermediate performance between the two flow metering techniques along the Z-shaped and the V-shaped ultrasonic paths. Notably, the combined technique showed better performance (expanded uncertainty less than 0.76%, k = 2) than the two flow metering techniques (1.61% and 1.17%, k = 2) in the flow range of (100–400) m³/h with pipe diameter of 250 mm.     

提高差压式蒸汽流量计测量精度的探讨

提高差压式蒸汽流量计的测量精度和稳定性,尤其是在小信号的工况下,以往的常规仪表甚至包括一些智能仪表都不能达到预期的要求。究其原因,主要是在计量的运算过程中,都未能严格按照国标GB／T2624—93的要求进行计算,并且对工况下一些影响计量精度的因数不能给予动态补偿,而且基本上都不考虑测量管道及安装质量对计量的影响。为了解决上述问题,有必要对传统的计量仪表作一些变革,采用某些特殊的功能（包括一体化安装等工艺细节）,改善和提高仪表的精度,使之更趋于实用化,使其真正达到GB／T2624—93的要求。     

The development of a multiphase flow meter without separation based on sloped open channel dynamics

The online continuous measurement of multiphase flow is one of the most key technologies which influences the development of oil industry in future. A new type of multiphase meter system is developed based on the open channel flow. The test pipe of the meter is slightly slopped to make the flow pattern mainly stratified flow. Based on the study of oil and gas flow dynamics in the open channel test pipe, the liquid metering model and gas metering model are deduced to calculate the gas and the liquid flow rate, the water cut is measured online by the principle of differential pressure. This device can work online without the separation of the production fluid. By the lab test and field application test, the results of the metering system show that the liquid flow rate errors are within ±5%, the gas flow rate errors can be within ±5%, and the water cut absolute error is within ±2%, which can meet the demands of the field flow rate measurement.     

The fractal flow conditioner for orifice plate flow meters

The sensitivity of orifice plate flow meters to the quality of the approaching flow continues to be a cause for concern in flow metering. The distortions caused by pipe fittings such as valves, bends, compressors and other devices located upstream of the orifice plate can lead to non-standard velocity profiles and give errors in measurement. The design of orifice plate meters that are independent of the initial flow conditions of the upstream is a major goal in flow metering. Either using a long straight pipe, or a flow conditioner upstream of an orifice plate, usually achieves this goal.The effect of a fractal flow conditioner for both standard and non-standard flow conditions was obtained in experimental work and also using simulations. The measurement of mass flow rate under different conditions and different Reynolds numbers was used to establish a change in discharge coefficient relative to a standard one. The experimental results using the fractal flow conditioner show that the combination of an orifice plate and a fractal flow conditioner is broadly insensitive to upstream disturbances.The simulation results also show that the device can be used as a part of a flow metering package that will considerably reduce installation lengths. Previous work with orifice plates has shown that a combination of flow conditioner and orifice plate was promising. The results of using a combination of the fractal flow conditioner and orifice plate for non-standard flow conditions including swirling flow and asymmetric flow show that this package can preserve the accuracy of metering up to the level required in the Standards.     

Forced oscillation to reduce zero flow error and thermal drift for non-reciprocal operating liquid ultrasonic flow meters

A new method using forced oscillation excitation for transit-time difference (TTD) measurement is proposed to improve the accuracy and stability in ultrasonic flow metering under non-reciprocal operating conditions. Forced oscillation guarantees the frequencies of the received signals in both directions constant and known, thus the TTD can be measured as the phase difference. Choosing the driving frequency slightly off the resonance of the transducers can considerably decrease the long-term drift of the TTD results caused by temperature variations, and minimize the zero flow error. In the simulations and experiments, the proposed method showed good performance in the non-reciprocal metering system, the zero flow error and the thermal drift on the TTD measurement results were reduced.     

Experimental study to establish an evaluating method for the responsiveness of liquid flowmeters to transient flow rates

An aim of this research work is to establish an evaluation method concerning a responsiveness of flowmeters for a transient flow rate. To this end, reference flow metering systems for the transient flow are proposed in this paper. Because a behavior of the responsiveness depends on the type of flowmeter, evaluations using different parameters, such as response time to sudden rise and sudden fall in flow rate, response to the frequency and amplitude of flow pulsation, mean characteristic and so on are needed. To achieve a precise evaluation, two reference flow metering methods for transient flow rates are proposed in this paper. One is a high-response weighing method and the other is a velocity profile measurement method using the ultrasonic pulsed Doppler method (UPDM). Since the behaviors of the transient flow rate measured by both methods show good agreement, we conclude them to be useable as a reference flow metering system.