A heat thermistor gas microflowmeter

The design and operating principle of an autonomous thermistor gas microflowmeter are described. The instrument can operate in constant-power and constant-temperature modes and yields output signals in the ohmic, frequency, and current forms. The autonomous operation of the flowmeter is ensured by the temperature stabilization of the controlled medium at a specified level. The results of the experimental studies of the instrument’s characteristics are presented, and the methods for their improvement are shown. Its accuracy is estimated at a level of ～0.5% at a gas flow rate of 60–70 mg/s, and the time constant is ～3 s. Owing to its hermetically sealed housing, the flowmeter can be used in a vacuum chamber.     

A gas microflowmeter with a specified sensitivity value

A method for specifying the output signal and constant (in a 0- to 50-mg/s flow rate range) sensitivity of a microflowmeter independently of the sort of the monitored gas is described. Results of an experimental study of quantitative and qualitative characteristics of a thermoanemometric thermal flowmeter based on indirect-heating thermistors are given. In a 0- to 25-mg/s nitrogen and argon flow rate range, the output signal varies from 70 to 100 V and the sensitivity is 2 V/(mg s^?1). The measurement accuracy is 0.13–0.28%, depending on the specified tempeature difference. The temperature self-regulation of the flowmeter is ensured by heat-carrier thermal stabilization at temperature levels specified by a special thermostabilization system. The active behavior of the heat-carrier thermostabilzation system assumes that it can be used in the vacuum chamber of the test stand.     

Analysis of viscosity effect on turbine flowmeter performance based on experiments and CFD simulations

Viscosity effect is one important factor that affects the performance of turbine flowmeter. The fluid dynamics mechanism of the viscosity effect on turbine flowmeter performance is still not fully understood. In this study, the curves of meter factor and linearity error of the turbine flowmeter changing with fluid viscosity variations were obtained from multi-viscosity experiments (the viscosity range covered is 1.0×10^–6 m²/s–112×10^–6 m²/s). The results indicate that the average meter factor of turbine flowmeter decreases with viscosity increases, while the linearity error increases. Furthermore, Computational Fluid Dynamics (CFD) simulation was carried out to analyze three-dimensional internal flow fields of turbine flowmeter. It was demonstrated that viscosity changes lead to changes of the wake flow behind the upstream flow conditioner blade and the flow velocity profile before fluid entering turbine rotor blade, which affect the distribution of pressure on the rotor blades, so impact the turbine flowmeter performance.     

温压补偿型超声气体质量流量计

对超声时差法进行算法改进后，结合气体密度公式推导出超声质量流量方程，据此设计出温压补偿型超声气体质量流量计，给出了流量计核心系统及温压补偿部分的硬件设计。将只用于流体体积流量测量的超声流量计推广到气体质量流量测量领域，使超声流量计趋向理想化。经实验证明此流量计在测量常压空气时精度可达1．42％。     

基于软硬件联合补偿的智能槽道流量计

按照智能化、精度高、通用性强、性价比高的技术要求,针对槽道流量计提出采用硬件电路和软件优化算法相结合的方式对各检测流体的压力、温度、密度、压缩系数、黏性系数及可膨胀系数等参数进行相应补偿,使其适用于常用流体的测量,且精度大幅提升,可达0.3%～0.5%左右,从而在复杂现场构建一个多参数高精度的可靠性流量检测平台.     

A Portable Dilution Refrigerator

Refrigerating units of two dilution cryostats manufactured in the form of inserts for a commercial portable nitrogen-free cryostat for liquid helium are described. The ³He circulation in both apparatuses is achieved by its evacuation via its condensation on a wall at a temperature of 0.35–0.5 K, which is cooled by the sorption-based evacuation of ³He from a separate bath. One of the apparatuses operates periodically. A temperature below 0.1 K is maintained in it for several hours, after which the sorption pump needs to be regenerated for ∼0.5 h. The other apparatus includes an additional bath with liquid ³He that maintains its circulation during the sorption-pump regeneration thanks to the large specific heat of this liquid. The minimum temperature reached in experiments was 0.035 K. The refrigerators operate at a circulation rate of ∼2–10 μmol/s and consume 1–2 l/day of liquid helium for maintaining their operation. The refrigerators are designed to cool photodetectors or samples in experiments that do not require a high refrigerating capacity. __________ Translated from Pribory i Tekhnika Eksperimenta, No. 5, 2005, pp. 142–152. Original Russian Text Copyright ? 2005 by Herrmann, Ofitserov, Khlyustikov, Edel'man.     

Evaluation of flowmeters for heat metering

Heat flowmeters are expected to be reasonably priced, be very reliable, and have high measurement accuracy. Various types of heat flowmeters have been developed and they are widely used in large residential and industrial buildings. In this study, three types of heat flowmeters (turbine, electromagnetic and ultrasonic) were tested for accuracy, effect of installation position and vibration, durability and performance in the field for several installation positions and in the presence of vibration. We used a liquid flow standard system and a customized durability test system in accordance with the International Organization of Legal Metrology (OIML) R 75-2 heat meter testing method. The field test was conducted in eight different locations from winter to summer. All flowmeters were calibrated before and after the field test, and the measurement deviation and the relative expanded uncertainty were calculated. The mean deviations obtained were–0.21%,–0.07%, and 0.11%, with the relative expanded uncertainties 0.48%, 0.17%, and 0.40% for turbine, electromagnetic, and ultrasonic flowmeters, respectively. The results of position and rotation tests, mean deviations by rotation angles at 90°, 180°and 270°relative to 0°(horizontal position) were–1.24%,–1.07% and–0.80%, respectively. For the vibration tests at 1 m/s² and 5 m/s² vibration acceleration, the turbine flowmeter, the electromagnetic flowmeter and the ultrasonic flowmeter showed deviations that ranged from −0.2% to −0.5%, −0.6% (2.6 m³/h), and 0.0% (negligible), respectively. In the durability tests, the accuracy of all three types of heat flowmeters remained at ±1% or less, showing sufficient durability. In the field test, the deviation of the turbine flowmeter and the ultrasonic flowmeter showed ±2.5% or less deviation. However, the electromagnetic flowmeter seems to be inaccurate below 6.9% of the maximum flow rate.     

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.     

Experimental and numerical study of the flow characteristics of a novel olive-shaped flowmeter (OSF)

A novel differential pressure flowmeter with an olive-shaped flowmeter (OSF) is proposed and investigated both experimentally and numerically. The streamline, pressure and velocity are obtained and numerically analysed. The results indicate that the proposed OSF exhibits less permanent pressure loss than the orifice plate flowmeter (OPF). The pressure also tends to be more stable in the OSF, which ensures high measurement accuracy and repeatability. The OSF is superior to the OPF in terms of relative pressure loss, streamline distribution, pressure distribution and velocity distribution. In the experiment, an oil pump transported diesel oil into the measurement pipe, through the check valve, filter, pressure-regulating container, and flow-regulating valve, before it was finally returned to the fuel tank. The experimental results showed that the pressure loss of the OSF was only about 14.94% of that of the OPF under the same conditions. The pressure loss curve of the OPF increased rapidly by up to 2,700 Pa with each 1 m³/h increase in the flow rate, whereas that of the OSF increased only slightly.     

Study of the factors influencing the over-reading characteristics of the precession Venturi

In the energy industry, such as the gas field, precise measurement of wet gas is becoming increasingly crucial. Many studies have focused on the over-reading (OR) of throttle flowmeter in wet gas measurement. By using the dimensional analysis method, we proposed a precession Venturi and established a new OR correlation based on the gas Froude number, liquid-gas density ratio, and the Lockhart–Martinelli parameter. Experimental tests of air-water flow were conducted, and the relationships between differential pressure and OR with liquid volume fraction were investigated at various pressures and superficial gas velocities. The experimental results show that the uncertainty of gas flow rate measurement is in the range of 0.35%–0.56%, and 90.8% of the points are in the range of 0.35%–0.45%, with a relative error band of ±2.94% calculated by the OR correlation at a confidence probability of 95.5%.     

A mini fluidic oscillating flowmeter

This paper presents a mini fluidic oscillating flowmeter. This device is composed of three microfluidic laminar bistable amplifiers. The microfluidic amplifiers are connected in such a way that the measured flow through the mini fluidic oscillating flowmeter generates a periodical pressure signal with a high value of SNR (signal to noise ratio). The frequency of the pressure signal is proportional to the measured flow. The mini fluidic oscillating flowmeter works with gas or liquid. To calibrate the mini fluidic oscillating flowmeter, for gas flows, a volumetric flowmeter was used. To calibrate it for liquid flows, an experimental test bench was realized. The gas operating range of the mini fluidic oscillating flowmeter is up to Re=1500 starting from Re=200; the liquid operating range is up to Re=5700 starting from Re=170. The maximum error of the measurement is <2% of the full scale value, the reading error is <3% for gas flows and <3.8% for liquid flows.     

A liquid pulsed microwave radiation calorimeter

A wideband calorimeter intended for measuring energies of the pulsed microwave radiation with duration of several nanoseconds to 1 s is described. The calorimeter’s principle of operation is based on measuring the volume increment that results from heating, when the radiation is absorbed by a polar liquid. The energy measurement range is 10 mJ–100 J, the energy-absorption coefficient is >0.9 in a frequency band of 1.6–20 GHz and ～0.99 at frequencies of 4–18 GHz. The measurement error of the absorbed energy in the range 0.2–50 J does not exceed ±4%.     

超声波气体流量计检测精度影响因素分析

在天然气的管道运输过程中,提高气体流量测量的精度是提高运输效率、避免安全事故发生的关键技术。利用流体力学仿真（CFD）方法建立组合双弯管及变径管道模型,定量计算修正系数,对双声道超声波流量计结构和安装位置对于管道内气体速度场的影响进行研究。通过仿真得出超声波流量计的最优声道位置,并结合实验验证了仿真结果的可信性。模拟结果表明,双弯管和变径管与超声波流量计的安装位置至少为10D才能保证流体充分流动;通过修正系数随雷诺数的变化情况得出双声道超声波流量计的最优声道位置为距管道截面中心0.25D处。研究结论对于不同性质气体的流量检测同样适用,为工业中气体运输检测精度的提高以及超声波流量计的优化提供了依据。     

原子荧光法测定环境水样中的锑

利用氢化物发生-原子荧光分析技术(HG-AFS)对环境水样包括地表水、地下水、废水中的锑进行分析方法探究。通过一系列正交实验,优化出AFS-830原子荧光光度仪分析测定锑的最佳实验条件,方法的精密度为1.2%～8.6%、回收率为88%～112%、检出限为0.2μg/L、线性关系r大于0.999。实验结果表明:应用优化的仪器条件测定锑能够满足环境水样的分析要求。     

Experimental investigation of gas-liquid flow in a vertical venturi installed downstream of a horizontal blind tee flow conditioner and the flow regime transition

A venturi device is commonly used as an integral part of a multiphase flowmeter (MPFM) in real-time oil-gas production monitoring. Partial flow mixing is required by installing the venturi device vertically downstream of a blind tee pipework that conditions the incoming horizontal gas-liquid flow (for an accurate determination of individual phase fraction and flow rate). To study the flow-mixing effect of the blind tee, high-speed video flow visualization of gas-liquid flows has been performed at blind tee and venturi sections by using a purpose-built transparent test rig over a wide range of superficial liquid velocities (0.3–2.4 m/s) and gas volume fractions (10–95%). There is little ‘homogenization’ effect of the blind tee on the incoming intermittent horizontal flow regimes across the tested flow conditions, with the flow remaining intermittent but becoming more axis-symmetric and predictable in the venturi measurement section. A horizontal (blind tee) to vertical (venturi) flow-pattern transition map is proposed based on gas and liquid mass fluxes (weighted by the Baker parameters). Flow patterns can be identified from the mean and variance of a fast electrical capacitance holdup measured at the venturi throat.     

Particle image velocimetry flowmeter for natural gas applications

Ultrasonic flowmeters are currently used in the measurement of large natural gas flow. However, their high sensitivity to noise signals can cause measurement errors and direct economic losses. Particle image velocimetry (PIV) measurement technology has several advantages, including convenient installation and maintenance, and strong anti-interference ability, thereby presenting an innovative idea for its application in the field of flow measurement. In this paper, a cyclic integration method is proposed for the application of PIV technology in flow measurement of natural gas. The results show that PIV flowmeter and ultrasonic flowmeter are basically consistent, and the maximum deviation is about 2%. confirming the feasibility of the PIV flowmeter. Therefore, this study provides a theoretical and technical reference for the development of a PIV flowmeter for natural gas.     

排尘孔涡轮冷却叶片叶顶流动与传热研究

涡轮叶片叶顶排尘孔用于清除冷气中掺杂的尘粒,以保证气膜孔和冲击孔的可靠工作,但排尘孔射流引起叶顶流动和传热问题。采用参数化方法建立有、无排尘孔涡轮冷却叶片几何模型,基于包含叶片主体、主燃气通道和三腔回流式内冷却通道的全局模型,采用流热耦合数值分析,开展排尘孔对涡轮冷却叶片叶顶流动与传热问题的初步研究。研究结果表明,对比有、无排尘孔叶片,排尘孔射流可降低叶顶平均温度约25 K;冷却通道对流换热作用和叶顶排尘孔射流可使叶顶平面降温400～600 K,冷却效果与冷却通道冷气流量和尘孔结构在叶顶位置相关;排尘孔叶顶射流对叶顶间隙高温燃气泄漏具有阻碍作用,可以提高叶片总压恢复系数约0.5%～1.5%,随着冷气流量的增大,这种作用增强;尘孔结构设计应兼顾射流对叶顶流动与传热的共同影响。     

Effects of flow disturbance on an ultrasonic gas flowmeter

A series of tests are carried out to assess the effects of flow disturbance on a small dimension ultrasonic gas flowmeter. Flow disturbances generated by cone couplings, and single and double elbows are investigated. Measurements with a 100 D straight pipe upstream with a smooth connection to the meter body are used as a reference. Our measurements show that the symmetrical disturbance produced by a cone coupling at a 12 D distance from the transducer path does not impair the performance of the flowmeter. An asymmetrical disturbance, such as a single or a double elbow at the same distance, seems generally to give an underestimation of the flow velocity, resulting in reading errors of −1% or worse. Measurements with straight pipes of 10 D, 20 D, 40 D and 80 D between the disturbance and the flowmeter have also been made showing that 10 D can cause an overestimation of flow velocity. Increasing the length of the straight pipe generally decreases the error. More than 80 D straight pipe between the disturbance and the flowmeter is required to give a result within ±1% of reference conditions. The angle between the elbow plane and the transducer plane is changed from 0 to 315° in 45° steps. The meter error is plotted as a function of inlet angle, showing a clear relationship between these values.     

Influence of tube wall longitudinal heat conduction on temperature measurement of cryogenic gas with low mass flow rates

Longitudinal heat conduction is an important parameter in the cryogenic field, especially in cryogenic heat exchangers. In the present study, the parasitic effect of tube wall longitudinal heat conduction on temperature measurement within the tube has been studied for cryogenic gas with low mass flow rates by finite element method and experimental tests. The effects of various parameters such as tube outlet temperature, tube wall thermal conductivity, mass flow rate, and tube wall thickness have been investigated. Axial positioning errors of temperature sensor due to tube wall longitudinal heat conduction were higher for lower gas flow rates. The results showed that the tube wall thermal conductivity leads to axial heat conduction within the tube wall, but the higher tube wall thermal conductivity does not lead to bigger axial positioning error of temperature sensor at tube outlet. According to data obtained from simulations and experiments, sensor with distance of 5 mm from tube outlet had 14.92% and 8.51% temperature measurement error (with respect to gas flow temperature at tube outlet) for tube wall thermal conductivities of 16 and 400 W m⁻¹ K⁻¹, respectively.     

High GVF and low pressure gas–liquid two-phase flow measurement based on dual-cone flowmeter

Parameter measurement of gas–liquid two-phase flows with a high gas volume fraction (GVF) has received great attention in the research field of multiphase flow. The cone meter, as a new proposed differential pressure (DP) meter, is increasingly being applied in flowrate measurement of gas–liquid two-phase flow. A dual-parameter measurement method of gas–liquid two-phase flow based on a dual-cone meter is proposed. The two-phase flow is investigated in a horizontal pipeline with high GVF and low pressure, and exists in the form of annular flow. By adding a second cone meter, both gas mass fraction (GMF) and mass flowrate are measured. The pressure drop performances of five different sized cones have been discussed to make a cooperating cone selection and efficiently position the dual-cone in the pipe. Dual-cone flowmeter experiments of 0.45 and 0.65 equivalent diameter ratio combination, and 0.65 and 0.85 equivalent diameter ratio combination are respectively carried out to analyze the linearity of two-phase flow multiplier with Lockhart–Martinelli parameter and obtain the dual-parameter measurement results. The relative experiment error of GMF, gas mass flowrate and total mass flowrate are respectively within ±7%, ±5% and ±10%. The relative error of the liquid phase is within ±10% when the liquid mass fraction is beyond 40%. The experimental results show that it is efficient to utilize this dual-cone method for high GVF and low pressure gas–liquid two-phase flow measurement.