Calculation of the Pitot tube correction factor for Newtonian and non-Newtonian fluids

This paper presents the numerical investigation performed to calculate the correction factor for Pitot tubes. The purely viscous non-Newtonian fluids with the power-law model constitutive equation were considered. It was shown that the power-law index, the Reynolds number, and the distance between the impact and static tubes have a major influence on the Pitot tube correction factor. The problem was solved for a wide range of these parameters. It was shown that employing Bernoulli's equation could lead to large errors, which depend on the magnitude of the kinetic energy and energy friction loss terms. A neural network model was used to correlate the correction factor of a Pitot tube as a function of these three parameters. This correlation is valid for most Newtonian, pseudoplastic, and dilatant fluids at low Reynolds number.     

光电非接触式表面流速测量

针对水工物理模型试验中尚无简单易行的表面流速测量方法,提出了一种新型光电非接触式表面流速直接测量法。在对光束入射水体后散射光强度公式进行推导的基础上,根据水体浅层泥沙浓度的统计继承效应,得出了经上下游浅层泥沙调制的散射光强成相关特性的结论。根据上下游散射光的相关特性,推导了流速测量公式,并分析了上下游测量间距、水流流速、采样率对测量结果的影响。搭建了实验系统,在6种不同标定流速下,分析了不同含沙量对测量精度的影响。实验结果表明,在0～50kg/m36种不同含沙量情况下,实测流速与标定流速的一致性均较好,但水体在10～50kg/m3适量含沙情况下,测量精度较不含沙情况有所提高,测量绝对误差均小于0.1m/s,相对误差能控制在8%以内。     

Experimental research into a new design of flow-averaging tube

This paper presents the results of investigations into a new design of flow-averaging tube (FAT). The design uses two flow-averaging profiles that affect each other. One of these profiles receives a positive pressure p⁺, and the other a negative pressure p⁻. The differential pressure obtained, , is considerably higher than the differential pressure in other probes on the market. The research reported here aimed to optimize the respective positioning of the profiles. The experiments were performed in an aerodynamic tunnel. Subsequently, tests of prototypes with the profiles were conducted in pipelines with diameters of 104–296 mm. The results are presented in the form of the characteristics of the flow coefficient K as a function of the mean velocity of the air passing through a pipeline. It was found that the new probe design was associated with relatively high measured differential pressures. The observed characteristics are flat over an extensive flow range. This makes it possible to use a constant flow value without degrading the measurement uncertainty.     

皮托管在气流测量中一些问题的探讨

皮托管在气流速度测量中受多种因素影响。怎样使测量的数据准确可靠，除了仪器设备外，还要找出影响测量结果的其他原因并对其修正，就显得十分重要。本文的主要目的就是探讨在气流测量中风速的有关修正问题（如水的密度、压力损失、压缩性影响）。以国家气象计量站的设备和测量数据为例，经过水的密度、压力损失、压缩性影响的修正，60m／s时，其修正量为-0．5m／s。这就是为什么在高速时，标准风速偏高的原因。这一结果对于国内国际比对，使气流速度的量值与世界统一具有重要意义。     

New techniques for multi-component flow velocity measurement using high-frequency pulsed diode lasers

The application of high-frequency pulsed laser diodes for fringe-type laser Doppler anemometry allows multi-component flow velocity measurements by using only one receiver and one signal processing chain. This is effected by synchronization of the laser pulses with the sampling process of the data acquisition system. Consequently, an identical wavelength can be used for all components. The experimental verification of this new technique is described. The technique permits the design of miniaturized and low cost optical flow sensors which can be used for low and high speed flows.     

Application of averaging bidirectional flow tube for measurement of single-phase flow rate in a piping system

A new instrument, an averaging bidirectional flow tube (BDFT), is proposed to measure single-phase flow rates. This averaging BDFT has unique measuring characteristics foremost among which is the capability to measure bidirectional flow and insensitivity of the fluid attack angle. Single phase calibration tests were conducted to demonstrate the performance of the averaging BDFT. Likewise, to enhance the applicability of the averaging BDFT on various flow conditions, flow analyses using CFD code were performed focusing on design optimization of the BDFT. The calibration test results indicated that this averaging BDFT has a linearity within 0.5 % in the Reynolds (Re) number range of above 10,000 where it is meaningful in terms of application. The flow analyses results demonstrate a good linearity of the averaging BDFT with various design features. Therefore, averaging BDFT can be applied for measurement of flow rates within a wide range of flow conditions. This paper was recommended for publication in revised form by Associate Editor Won-Gu Joo Kyoung-Ho Kang received his B.S. and M. S. degrees in Nuclear Engineering from SNU (Seoul National University), KOREA in 1993 and 1995, respectively. He then received his Ph.D. degree in Nuclear and Quantum Engineering from KAIST (Korea Advanced Institute of Science and Technology) in 2009. Dr. Kang is currently a senior researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Kang’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, and experiments and modeling for the severe accidents. Byong-Jo Yun received his B.S. degree in Nuclear Engineering from SNU (Seoul National University), KOREA in 1989. He then received his M.S. and Ph.D. degrees from SNU in 1991 and 1996, respectively. Dr. Yun is currently a principal researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Yun’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, two-phase flow, scaling analysis, and development of instrumentation for two-phase flow. Dong-Jin Euh received his B.S. degree in Nuclear Engineering from Seoul University, Korea, in 1993. He then received his M.S. and Ph.D. degrees from same university in 1995 and 2002, respectively. Dr. Euh is currently a researcher at thermal hydraulic safety research department of Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Euh’s research interests include two-phase thermal hydraulics in the Nuclear Systems and Fundamental Phenomena. Won-Pil Baek has been working at KAERI as the general project manager (director) for development of nuclear thermalhydraulic experiment and analysis technology since 2001. He received his B.S. degree in nuclear engineering from Seoul National University and his M.S. and Ph.D. degrees from KAIST. In 1991–2000, he worked for KAIST as a researcher and research professor. Currently he also serves as an executive editor of the Nuclear Engineering and Technology, an international journal of the Korean Nuclear Society. His research interests include critical heat flux, integral effect tests, modeling, nuclear safety, and advanced reactor development.     

Examination of disturbed pipe flow and its effects on flow measurement using orifice plates

In a great number of measurements the influence of a disturbed flow on the flow coefficient of a standard orifice plate was investigated. Single bends and double bends out of plane with and without spacer tubes were used as typical disturbances. Experiments were also performed using a combination with a star-shaped flow straightener. The necessary correction factors of the flow coefficient were determined for upstream straight length shorter than detailed in ISO 5167. The flow velocity profiles produced by the disturbances were examined and on this basis profile numbers were calculated. The examinations presented here show that the existing standard should be revised as regards the definition of the fully developed turbulent flow profile and the selection of the required upstream straight lengths.     

皮托静压管的流量测量及不确定度评估

本文介绍了皮托静压管的结构原理及使用场合,讨论了使用皮托静压管进行流量测量时的测量计算方法,分析了实际测量条件下不同因素对流量测量结果的影响,并对测量结果的不确定度进行评估.     

Open channel flow measurement using international standards: introducing a standards programme and selecting a standard

This paper discusses the benefits and practicalities in introducing a standards programme in the field of open channel flow measurement. The work of ISO Technical Committee TC/113 and its subcommittees are discussed and the role of an ISO Technical Report (ISO/TR 8363) in identifying a measurement method is highlighted.     

Simulation on refrigerant flow in adiabatic capillary tube

This paper proposes a new mathematical model to calculate flow characteristics of the adiabatic capillary tube, which is aimed at solving problems existing in some earlier models. The Stocker’s model was modified with consideration of various effects due to sub-cooling, area concentration, and rolling diameter. The new model can be used not only for R22, but also for its substitutes such as R410A and R407C. A comparison of simulation results of the modified model with those in literature showed that the errors are within 10%. The flow characteristics are finally analyzed. __________ Translated from Journal of hydrodynamics, Ser. A, 2006, 21(3): 318-323 [译自: 水动力学研究与进展]     

Investigation of the batch measurement errors for single-straight tube Coriolis mass flowmeters

Batch flow is a typical method for calibrating Coriolis flowmeters. It is also an important application for Coriolis flowmeters in the process industry. Batch processes of short duration or from empty have been identified as an important development for Coriolis flowmeters. The measurement of total mass by a commercially available single-straight tube Coriolis flowmeter compared with a weigh scale is presented in this paper. A theoretical understanding for short batch is also provided by numerical simulations of both deterministic and probabilistic parameters. The simulation results agree with the batch tests and may, at least partially, explain the experimental findings.     

基于接触理论的弹簧管刚度测量技术的研究

本文研究了弹簧管头部与夹具孔间的接触变形对弹簧管的刚度测量精度的影响，基于Hertzian接触理论建立了接触模型及其误差分析模型。首先，给出弹簧管刚度测量原理和测量中的受力分析，然后，将测量力引起的接触力简化为均匀线分布后建立接触模型，最终建立测量误差和接触变形的量化关系。通过理论分析和实验验证，接触变形直接降低了测量精确度并增大了测量的不重复性误差。     

基于数字散斑相关法的弯管残余应力测量系统

为了测量圆形管件在弯曲后产生的残余应力的情况,提出了一种新的基于数字散斑相关法(DSCM)的残余应力测量方法并且搭建了对应的测量系统.利用该系统对90.弯管外圆弯曲处的残余应力进行了测量.使用电测法作为参考,验证了基于数字散斑相关法的测量方法能够有效测定弯管内残余应力的值.实验结果表明,该方法在保证一定的测量精度的同时能够大幅度地提高测量效率,为进一步研究残余应力对弯管工艺的影响提供了基础.     

相关法测两相流的研究

本文探讨一种以单片机为核心的两相流测量用软件相关仪中自动跟踪峰值,以确定流体渡越时间的新方法。将该方法与快速相关计算法相结合,可进行实时相关估计,同时可以保证峰值位置确定的可靠性。     

A mathematical model of the self-averaging Pitot tube: A mathematical model of a flow sensor

Flowmeters with self-averaging Pitot tubes are more and more often applied in practice. Their advantages are practically no additional flow losses, usability in the case of high temperature of fluids and simplicity of fitting. A mathematical model of a self-averaging Pitot tube including the influence of the probe shape, selected constructional features and flow conditions on the quantity of differential pressure gained has been given in this paper. The values and ranges of variations of the coefficients established for the model have been assessed on the basis of the numerically computed velocity and pressure fields around and inside the probe. Velocity and pressure fields were calculated by means of solving conservation equation and turbulence models. The characteristics linking values of the flow coefficient with values of the Reynolds number have been presented. The conclusions have been formulated taking flow metrology needs into account.     

德尔塔巴流量计在流量测量中的应用

介绍了一种用于流量测量的德尔塔巴流量计,简述了德尔塔巴的测量原理以及基本结构,详细的介绍了德尔塔巴流量计的特点并与孔板、转子流量计、涡街流量计等常见的流量仪表进行了对比,通过实例阐述了德尔塔巴在实际工程应用中的价值。     

Coriolis mass flow measurement of gas under normal conditions

This paper presents a new method of directly measuring the mass flow of gas using the well-known Coriolis principle, which has proved successful for mass flow measurement of liquids. The prototype consists of two U-shaped tubes, forming a device resembling very much a tuning fork, which is stimulated by electromagnetic actuators to perform autonomous bending oscillations. By this means the fluid is subjected to a radial velocity that, in combination with the axial velocity of the flow, induces harmonic Coriolis forces of the same frequency. This causes the U-shaped tube to perform torsional oscillations that superimpose on the bending oscillations. Both oscillations can be detected via electromagnetic transducers.

The amplitude of the torsional oscillation induced by the Coriolis forces is very small as the density of gas is very low. It can be amplified by tuning the eigenfrequencies of torsion and bending in a control loop. This results in an amplification of the torsional amplitude by a factor of 10², allowing the mass flow of gas to be measured under normal conditions.     

Time resolved measurement of pulsating flow using orifices

This article reviews the theoretical background of the measurement of pulsating flow using orifices as flow to pressure transducers, providing a synopsis of work done in this field. Special attention is paid to the temporal inertia and the applicability of expressions thereof given in the literature. Other factors influencing the measurement, such as changing flow profiles and the effect of connection tubes between the pressure sensor and the orifice are discussed. An experiment was performed to investigate the applicability of an equation taking reverse flow and temporal inertia into account for the measurement of pulsating flow with relative pulsation amplitudes around 1 and frequencies up to 50 Hz. It was found that the suggested equation may give tolerable results if the ratio of the pulsating part of the velocity to the angular frequency times orifice diameter is not too high. For high ratios, however, the results could not be explained by the suggested equation.     

Simultaneous measurement of continuous and dispersed phase in a two phase jet flow

In the present paper, a method is proposed and applied in order to increase the size range sensitivity of a Phase–Doppler–Anemometry (PDA) system, allowing simultaneous measurement of size and velocity distributions of continuous and dispersed phases in gaseous, dispersed two phase flow. Discrimination between the two phases is directly achieved here from the detected phase difference. Design considerations are presented to increase the size range sensitivity of the PDA system to 1:200. Therefore, the optical properties for light scattering of the particles are properly adjusted to the measurement problem by colouring the particles homogeneously. The application of the system is described by measurements of velocity profiles in a zone close to the nozzle of a two phase jet with a tracer to particle diameter range of 1–160 μm.