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Edward Morrell
INTERACTIONS BETWEEN GAS FLOW MEASUREMENT INSTRUMENTS AND GAS FLOW SOURCES

The interconnections and procedures followed when using gas flow measurement instruments are critical to obtaining accurate flow measurements. Errors can be introduced from; interactions between flow sources and flow measurement instruments, interconnecting plumbing, thermal instabilities and pressure variations. The introduced uncertainties can be especially large when measuring gas flow in situ at industrial installations. Many end users have little knowledge or appreciation for these effects and as a result measurement errors are often introduced in gas flow measurements. In this paper, we report and quantify measurement errors when using a positive displacement piston prover to calibrate gas flow in industrial installations.

D. J. Pack, A. B. Chesnoy, J. Bosio
GAS FLOW MEASUREMENT AND THE IMPACT OF CONTAMINANTS IN THE GAS STREAM

Significant advances have been made over the past couple of decades with respect to flow metering technology applicable to natural gas transmission measurement. Current flow meter technology is characterised by high reliability, excellent turndown and very low measurement uncertainty. However, the environment in which these flow meters are being placed is becoming more demanding on the meter’s operation and performance. This is because of the trend to operate pipelines at higher pressures and transport varying gas composition from multiple pipeline system inlet points. These conditions are conducive to the formation of unwanted contaminants within the gas stream.

L. J. Huang, Y. Feng, K. S. Ling, W. T. Wong, M. F. Sham
MEMS MASS FLOW METERS WITH IN SITU GAS COMPOSITION COMPENSATION

Thermal mass flow meters for gas metering with complicated gas composition are often a challenge as it requires the real gas calibration. In many cases, particularly for gases with dangerous or harmful components the calibration is very costly and sometimes even not feasible for re-calibration at field. It is even worse that at the time gas composition varies, the calibration would be erroneous. In this paper, the design, theory and experiments for a MEMS thermal mass flow meter that is capable to dynamically compensate the gas composition variation during measurement are discussed. The meter can also provide in situ measured gas thermal values.

E. von Lavante, H. Kaya, F. Winzösch, S. Brinkhorst
DETAILED STUDY OF FLOW STRUCTURE IN CFVN AND ITS EFFECTS ON THE FLOW RATE

The flow fields in a toroidal Venturi nozzle shaped according to the ISO 9300 Standard, have been investigated using numerical flow simulation. The present study aimed at clarifying some of the phenomena associated with the unchoking of the throat. To this end, the shock structure has been studied for different Reynolds numbers and exit pressure ratios. The flow simulations were carried out in two and three dimensions. The flow fields were always unsteady, displaying a complex shock-boundary layer interaction.

Bradford W. Sims, Michael S. Carter, Charles L. Britton, Robert J. McKee,
BRADFORD SIMS - CHOKING PRESSURE RATIO GUIDELINES FOR SMALL CFVS

The ratio of maximum exit static pressure to inlet stagnation pressure that maintains sonic velocity at the throat of a Critical Flow Venturi (CFV) is referred to as the Maximum Back Pressure Ratio (MBPR). Current standards only provide MBPR equations for CFVs operated at throat Reynolds Numbers (Rent) above 200,000. This paper will provide MBPR guidelines for operating CFVs below a Rent of 200,000. Additionally this paper will examine the causes of "premature unchoking" and how diffuser geometry contributes to this effect.

Masahiro Ishibashi, Tatsuya Funaki
BOUNDARY LAYER TRANSITION IN HIGH PRECISION CRITICAL NOZZLES OF VARIOUS SHAPES

Calibration results of accurately machined critical flow Venturi nozzles are summarized and a single fitted curve of the discharge coefficient against the Reynolds number were obtained that covers from the laminar to the turbulent boundary layer regimes. Possibility to use critical flow Venturi nozzles with smaller inlet curvature such as R = 1.0 D is discussed. Effects of diffuser length, inlet curvature, inlet diameter and inlet shape are also discussed. It is shown that theories will fail to predict discharge coefficient correctly when R is small.

Lifen Wan, Chunhui Li, Yan Li, Lishui Cui
THE UPSTREAM INSTALLATION EFFECT ON THE CBPR OF SONIC NOZZLE

The test for the critical back pressure ratio (CBPR) of a sonic nozzle by using an orifice plate is established, and six types of upstream conditions are set up. Preliminary experimental results show that the upstream conditions have almost no effect on the CBPR at throat Reynolds number larger than 1.1 × 105, but better upstream conditions or the longer lengths of upstream straight pipe can improve flow stability; when throat Reynolds number smaller than 1.1 × 105, the upstream installation condition would have a significant impact on the CBPR, because of the occurrence of the premature unchoking phenomenon. Therefore, it is necessary to measure the CBPR in use for small throat diameter nozzle.

E. von Lavante, J. Allofs, F. Winzösch, R. Kramer, B. Mickan
NUMERICAL AND EXPERIMENTAL INVESTIGATION OF FLOW FIELDS IN CRITICAL FLOW SMALL SIZE NOZZLES

Due to their long term stability, well understood flow behaviour and very low uncertainty, standard critical flow Venturi nozzles (CFVN) are enjoying great popularity as a calibration tool and flow metering device. Their application to very small flow rates beyond the ISO 9300 Standard, however, leaves many questions unanswered. The present work aimed at detailed investigation of flow fields within CFVNs of diameters between 15 µm and 80 µm. The present numerical flow simulations were validated by corresponding experimental work carried out at the PTB.

Prof. Y. Pistun, Assoc. Prof. F. Matiko, Assoc. Prof. R. Fedoryshyn
IMPROVEMENT OF ACCURACY OF NATURAL GAS METERING BY MEANS OF HOUSEHOLD GAS METERS

The paper deals with the new technique for calibration of the household gas meters according to the working conditions in order to reduce the error caused by non-conversion of gas volume to base conditions. To apply this technique the studies of gas pressure and temperature variations in household gas meters during a year were carried out, the ratio of gas volumes consumed by household consumers during the cold and warm seasons of the year is defined. Based on the studies the average annual gas temperature and pressure weighed by the consumed gas volumes are defined. Based on the weighed values of gas temperature and pressure the nominal values of gas temperature and pressure are defined in order to convert the readings of the gas meters to these nominal values. Application of the developed technique provides reduction of unaccounted volume of gas and reduction of unbalances in gas distributing companies.

H.-B. Böckler, R. Kramer, B. Mickan,
INVESTIGATION OF METHANE LOSSES DURING THE CALORIC UPGRADING OF BIOGAS FOR GRID INJECTION

In the last years a large number of bio gas plants were build which generate gas mixtures of methane and carbon dioxide usually up to 1000 m3/h in a single plant. Often this gas is used as fuel for electrically power generation but there is also an interest to inject the gas into the public gas grid. For this purpose a purification is needed which increases (upgrades) the methane partition of the injected gas in order to realize gross caloric value similar to the natural gas in the grid. An important issue of CO2 -separation is the emission of methane into the atmosphere by losses which is dependent from the applied technology.

Page 495 of 977 Results 4941 - 4950 of 9762