Xu Ying, Zhang Tao, Wang Huaxiang, Liu Zhengxian, Chen Deyu
Computational Investigation on the Float-Type Flowmeter in Three-Dimensional Turbulence Flow Field

Based on the turbulence models and computational fluid dynamics (CFD), this paper presents a computational investigation on three-dimensional turbulence flow field of the float-type flowmeter. The forced floating element can be analyzed quantitatively from pressure field and the meter's flow rate from velocity field can be obtained. Meanwhile, this research is combined with an approach proposed by the authors, i.e. the error analysis method of the float-forced-balance-degree', which can realize a reliable estimate of the flow rate of the studied flowmeter. Simulation and experimental results show that the maximum full-scale error of flow rate is 3.4 %, and the full-scale mean error, 1.77 %. However, the corresponding errors using conventional design are 23.7 % and 8.9 % respectively.

Ki Won Lim
An Experimental Study on the Characteristics of Oval Gear Flowmeters

An experimental investigation was conducted into the characteristics of an oval gear flowmeter (OGF) using various fluids with different viscosities such as liquid butane (0.17 cP), gasoline (0.40 cP), spindle oil (12.0 cP), etc. Three OGFs were adopted that have a 50 mm inner diameter and ± 0.2 % repeatability in the range of 3 and 17 m³/h . The top and side clearances were measured to see their effects on its overall characteristics. The leakage flow through the clearance between its rotor and casing body was determined by liquid viscosity and the size of the clearance. The amount of the leakage flow has been both measured experimentally and estimated theoretically with the calculated velocity profile in the clearance. In the experiment, the piston prover, the gravimetric, and the volumetric calibrators have been employed. Then, the uncertainty of each calibrator was evaluated as being within ± 0.1 % in flow quantity determination using an evaluation procedure that follows ISO recommendation. It was found that the characteristics of OGFs depend on the viscosity of fluid and the magnitude of clearance. Also, the characteristics, when measured with other liquids than water, can be predicted based on the water measurement results. As the results of this study, a correction equation of ( δQ = 0.272 In µ – 0.0113 is proposed to predict the flow measurements of other liquids by utilizing a correction method developed in this study.

Zhang Xiaozhong, Wu Pingdong, Liang Minghua, Sun Yuehao
The Experimental Study and Uncertainty Analysis on the Double Turbine Mass Flowmeter with the Corrective Property for Velocity Distribution

This paper presents an experimental test results on the double turbine mass flowmeter with the corrective property of liquid velocity distribution. Further analysis on its uncertainty has been conducted accordingly.

Floris Huijsmans, Johan Bats
The On-line Energy Meas urement of Natural Gas New Technologies

Since the early eighties, Process Gas Chromatographs have been the de facto standard for on-line energy measurement. Being a robust, accurate and widely accepted technology, it is however relatively slow and therefore not suited for control applications.
Instromet recently developed both a new generation of Process Gas Chromatographs, and a fast Correlative Energy Meter. This allows to serve the complete on-line energy market, from the accountable measurement systems requiring ultimate precision to control applications with the accent on speed of response.
The EnCal 3000 represents a new era in Process Gas Chromatography for natural gas. The combination of MEMS based analytical components with narrow-bore capillary columns improves analytical performance, analysis time, utility consumption and overall dimensions with a factor 3 to 5 compared to systems based on conventional technology.
The EnSonic is a Correlative Energy Meter, calculating the on-line gas properties based on only 3 input parameters using a patented correlative algorithm. The continuous input of the Velocity of Sound at elevated pressure (VoSH) and at near-atmospheric conditions (VoSL), together with the measurement of the CO₂ concentration, provides the base for the on-line assessment of all gas properties within seconds, at an accuracy level comparable to conventional Process Gas Chromatographs.
The paper explains the 2 technologies in detail with extensive field test results, and gives examples of typical applications for both devices.

H.J. (Henk) Riezebobs
Acoustic Effects in Metering Stations; Impacts on Performance of Flow Metering Equipment

Acoustics plays a central role in the current state-of-the-art gas metering equipment. In the last decade the benefits of ultrasonic techniques in fiscal metering of high gas volumes has become apparent. These metering technique expresses lots of advantageous features, like high accuracy, large rangability, low pressure drop and self-diagnostic capabilities.
Recently in addition to flow metering applications the acoustic techniques have also been applied in energy flow or Wobbe metering devices. An example of this is the Ensonic, a fast energy meter, which uses a correlative technique based upon measurements of the velocity of sound (VOS) at two different pressures and the CO₂ percentage. This technique yields a fast, low cost device, which is with respect to uncertainty (< 0,3 %) and reproducibility (< 0,1 %) fully comparable to the highly accurate field GC which are used for custody transfer purposes. Because of its very fast measuring cycle of <~ 5 seconds this technique is excellently suited for gas quality control purposes.
Application of these techniques raises the question whether acoustic effects always present in piping systems can influence the reliability and accuracy of the measurements. Acoustic effects are present in any piping systems, either through sources like compressors or valves, but also through possible flow induced pulsations. All flow measurement devices in some way are affected by their presence. Orifice and venturi flow meters, based on measurement of differential pressure across a restriction experience a square-root error and/ or gauge line errors due to pulsations. Turbine meters experience so-called rotor-slip errors when operating in dynamic acoustical conditions. Moreover, practical experience at Gasunie shows that sometimes turbine meters are rotating under the influence of acoustic waves even when they are positioned in a standby metering run with closed valves! Some examples are shown in the paper.
How about the devices based upon the current state-of-the-art ultrasonic measurement techniques? Theoretically some aliasing errors can occur when the acoustical periods are close to the sampling time interval. In practice we have noticed some other effects. A serious drawback of the ultrasonic measurement technique is its sensitivity to noise of pressure reducing elements. It is somewhat ironical, that especially low-noise valves have more disturbing ability than regular valves. This ability originates in the fact, that low-noise techniques focus on the audible noise region and this sometimes implies a shift of the noise levels to the more ultrasonic part of the spectrum, where they can influence the signal-to-noise ratio of the US metering equipment.
Besides disturbing valves also certain flow straighteners can produce acoustic effects. These effects have been studied at Gasunie Research in bi-directional metering run tests at our flow facility in Westerbork. In such a setup always one of the two flow straighteners experiences an opposite flow direction. Such a flow straightener will produce whistling sounds at high flow velocities, which at a certain levels will affect the US metering performance.
As long as metering devices remain sensitive for all types of acoustic influences it is strongly advised to have an acoustic eye already in the design stage of metering or calibration facilities. Acoustic control is crucial in obtaining state-of-the-art quality and low measurement inaccuracy.