T. Mušič, G. Bobovnik, J. Kutin
The article presents a computer vision system for liquid level detection in standard capacity measures that can be used for automating measurements or preforming them in inaccessible places. The developed computer vision system consists of a digital camera and a computer program in the LabVIEW environment. The acquired images are processed and corrected for different distortions (parallax, lens and tilt distortion). By using the edge detection method, liquid level is detected and corrected for all distortions. The computer vision system was tested using water in a laboratory environment on...
U. Primožič, G. Bobovnik, J. Kutin
A PVTt primary flow standard operates on the principle of determining the change of density of the measured gas in the tank of a known volume and the corresponding time interval. The PVTt standard presented in this paper is based on the diverter-operated flying start and finish method. It contains the gas collection tank that is constructed as a dismountable assembly, which enables determining its internal volume by dimensional measurements. The standard is designed for the flow range from 0.12 mg/min to 12 mg/min and it achieves the relative expanded measurement uncertainty between 0.12%...
G. Bobovnik, J. Kutin
The leakage flow rate represents one of the most important contributions to the uncertainty of the measured gas flow rate at the bottom limit of the measuring range in a clearance-sealed piston prover. In order to successfully minimize its uncertainty contribution, it is necessary to understand the effects related to the reproducibility of the piston's travelling path relative to the cylinder and to the ability to position the piston prover in the ideal vertical position. The paper deals with an experimental study of the leakage flow rate in the inclined piston prover. The test results show...
Chen Hui-yu, Cui Li-shui
In order to solving the natural gas flow measurement problem about measuring flow under the complicated conditions and the measurement traceability of large diameter instruments, a set of optical natural gas flow metering devices based on Laser Doppler Velocimetry was established, translating the traditional flow volume measurement into pipeline section velocity field measurement to achieve the accurate measurement of natural gas flow. Results show that: the facility can achieve 1.45Mpa, 500m³/h the largest experiment measuring ability and the expanded uncertainty was 1.42% (k = 2); The...
H. Warnecke, C. Kroner, D. Schumann, J. Tränckner
Cavitation is a phenomenon, which is typically associated with negative effects, for example damage at propellers in water. However, there are various applications in which cavitation is exploited advantageously such as injection nozzles in diesel engines or cleaning with an ultrasonic bath. A new application is the deployment of cavitating nozzles in liquid flow measurements. The novelty of the application means from a metrological point of view the requirement to analyse potential influencing factors on the measurement quality in-depth. These comprise among others the installation...
D. Jonker, W. M. Dlamini, R. M. Molefe
Interlaboratory comparison and verification measurements performed in the Gas Flow Laboratory indicated stability problems in the flow ranges below 50 mL/min and above 30 L/min. Initially the stability problems in the low flow range below 50 mL/min were attributed to the flow cell used as reference standard. The unstable measurements above 30 L/min were attributed to the lack of sufficient pressure drop in the flow path from the gas cylinder to the measuring point. However, further measurements performed indicated that this might not be the cause of the instabilities experienced. To further...
Jos van der Grinten, Bodo Mickan
Currently all measurement capabilities for high-pressure gas flows in Germany are based on a single traceability chain. However, there are three primary standards available that can be made traceable without mutual dependencies. In this study PTB investigates the benefits of combining three independent traceability chains. The applied method is identical to the harmonization of the high-pressure cubic metre of natural gas [1]. For two G1000 transfer reference meters the measurement uncertainty decreases from 0.110% to 0.089%. For the working standards the CMCs decrease from 0.156% and 0.175%...
M. Olbrich, E. Schmeyer, M. Bär, M. Sieber, K. Oberleithner, S. Schmelter
Multiphase flow measurement devices are significantly affected by the occurring flow pattern, such as, e.g., slug flow, leading to large uncertainties. In this context, the slug flow pattern in horizontal pipes is investigated with the aim of finding a statistical characterization of the structures in space and time. For this, two different instances of slug flow are analyzed with a snapshot proper orthogonal decomposition and an additional mode coupling algorithm, which provides an energy-ranked mode basis of the underlying coherent structures. For the considered flows, the most energetic...
Felipe Jaloretto, Marcelo Souza de Castro
This work describes the procedure used to define the measurements uncertainties of experiments in horizontal air-water two-phase flow performed in order to identify influences due to pipe diameter. These experiments were performed with 4 different pipe diameters, always using the same test section length, therefore varying the length-by-diameter (L/D) ratio. Several parameters were measured, such as fluid flow, pressure, temperature and pressure drop; other parameters were calculated, such as the superficial velocities of each fluid, as well as their respective properties. The main...
S. Schmelter, M. Olbrich, E. Schmeyer, M. Bär
Multiphase flow, especially two-phase gas-liquid flow, is of great importance for a variety of applications and industrial processes, for example in the nuclear, chemical, or oil and gas industries. In this contribution, we present simulation results for gas-liquid slug flow in large horizontal pipes. Six test cases with different oil, water, and gas flow rates are considered, which cover a wide range of different slug flows. The numerical predictions are validated by comparison with experimental data obtained from video observations, which have been recorded at NEL as part of the European...