Gas Flow Rate Measurement Research Articles

Gas and Liquid Flow Rate Measurement in Wet Gas Based on Differential Pressure Signals

Gas and Liquid Flow Rate Measurement in Wet Gas Based on Differential Pressure Signals

Evaluation of Leakage Through Graphite-Based Compression Packing Rings

The prediction of leakage is one of the most challenging tasks when designing bolted flanged connections and industrial valves. Failure of these pressure vessel components can cause shutdowns but also accidents, loss of revenue, and environmental damages. With the strict regulations on fugitive emissions and environmental protection laws new tightness-based standards and design methods are being adopted to improve the sealing performance of bolted joints and valves. In addition, there is a practical interest in using a reliable correlation that could predict leak rates of one fluid on the basis of tests carried out with another on compressed packings. The paper presents an innovative approach to accurately predict and correlate leak rates in porous braided packing rings. The approach is based on Darcy–Klinkenberg to which a modified effective diffusion term is added to the equation. Experimentally measured gas flow rates were performed on a set of graphite-based compression packing rings with a large range of leak rates under isothermal steady conditions. Leakage from three different gases namely helium, nitrogen, and argon were used to validate the developed correlation. In the presence of the statistical properties of porous packings, the leak rates for different gases can be predicted with reasonable accuracy.

Novel application of gas chromatography in measurement of gas flow rate

Real-time volume flow rate of gas component for slowly changing composition mixtures is of chief importance for some special research applications. However, it is always difficult for us to achieve the goal by sophisticated gas flowmeter. In this study, we demonstrate two methods for the problem solution by the flow measurement of acetylene in unsteady gas flow based on online gas chromatography accompanying with a gas mass-flowmeter. For Method 1, high purity methane is applied as an internal standard and the volume flow rate of acetylene is obtained via coherent equations. Method 2 makes fully use of the online gas chromatography automated integration under fixed gas chromatography work conditions. Results have shown that both methods are feasible and effective, and Method 2 is more accurate than Method 1 with relative error less than 0.7%.

Error analysis of gas and liquid flow rates metering method based on differential pressure in wet gas

Online measurement of gas and liquid flow rates in wet gas is of great significance in industry. When the differential pressure meter is used to measure the gas and liquid flow rates, an over-reading correlation is needed to correct the liquid-induced overestimation of the gas flow rate and an auxiliary correlation is needed to obtain the liquid fraction or flow rate. With the two correlations incorporated, the gas and liquid flow rates can be calculated. In the present study, error analysis of this metering method is conducted. The results demonstrate that metering methods based on differential pressure exhibit similar error pattern, i.e., the prediction error of gas phase is small while that of the liquid phase is large. This phenomenon can be interpreted by error propagation and the underlying physics is that the two-phase differential pressure is mainly dependent on the gas phase but insensitive to the liquid phase. It is found that both the mean value and the fluctuation of the differential pressure signals are able to reflect flow rate changes of wet gas flow. However, metering methods based on the differential pressure fluctuation present larger prediction errors than that based on the differential pressure mean value. The reason is that the differential pressure fluctuation has much poorer repeatability compared with the differential pressure mean value.

Online measurement of gas and liquid flow rate in wet gas through one V-Cone throttle device

In the present study, an accurate cost-effective online system for metering both the gas flow rate and the liquid flow rate in wet gas with only one V-Cone throttle device is developed. The two-phase mass flow coefficient is employed to correct the measurement deviation of the V-Cone throttle device. The effects of the liquid densiometric Froude number, the gas densiometric Froude number and the ratio of gas density to liquid density on the two-phase mass flow coefficient are experimentally investigated. The equivalent diameter ratio of the V-Cone throttle device is 0.55. The experimental fluids are air and tap water. The operating pressure, the superficial gas velocity and superficial liquid velocity range from 0.1MPa to 0.3MPa, 4.87m/s to 25.26m/s and 0 to 0.38m/s, respectively. The results show that the two-phase mass flow coefficient linearly increases with the liquid densiometric Froude number and is affected by the gas densiometric Froude number and the ratio of gas density to liquid density. On the basis of the two-phase mass flow coefficient, the correlation for measuring the gas flow rate of the wet gas is developed. To reflect the influences of the liquid on the measurement, the pressure loss ratio of the V-Cone throttle is proposed. By incorporating the gas measurement correlation of the wet gas, the wet gas correlations to simultaneously meter the gas and liquid flow rate are concluded. In the present cases, the relative error of the gas mass flow rate predicted by the correlations is within ±5.0% and the mean absolute percentage error is 2.52%; the full scale relative error of the liquid mass flow rate is within ±5.0% and the mean absolute percentage error is 7.03%. The method proposed in this study creates a simple inexpensive wet gas metering system that can operate well in a significant range of industrial applications.

Field evidence of CO2 sequestration by mineral carbonation in ultramafic milling wastes, Thetford Mines, Canada

Two experimental small-scale cells have been constructed in the field to better understand passive mineral carbonation under natural atmospheric conditions in the ultramafic milling wastes of Thetford Mines (Québec, Canada). The magnesium-rich milling wastes mainly consist of poorly sorted grains and fibers of lizardite and chrysotile, with smaller amounts of antigorite, brucite and magnetite. These wastes could serve as significant and long-term CO2 sinks but the mechanisms and rates of mineral carbonation are not well understood. In this paper, the design of the experimental cells along with observations on gas composition, gas pressure, soil temperature, volumetric water content and mineral composition are presented with the objective to better understand the mineral carbonation processes under natural conditions and to propose a conceptual model for mineral carbonation at the field cell scale. Low CO2 concentrations (5–50ppm) measured in the experimental cells and the presence of hydromagnesite suggest that natural and passive mineral carbonation is a significant process occurring in the magnesium-rich wastes (4kg/m3/year of sequestrated CO2). In the proposed conceptual model, atmospheric CO2 (∼400ppm) dissolves in the hygroscopic water of the piles, where weathering of magnesium silicates forms magnesium carbonates. Water saturation in the cells is relatively stable over time and varies between 0.4 and 0.65, which is higher than optimal saturation values proposed in the literature, reducing CO2 transport in the unsaturated zone. Gas-phase CO2 concentrations along with gas flow rate measurements in the cells suggest that the reaction is most active close to the surface and that diffusion of CO2 is the dominant transport mechanism in the wastes. Although the carbonation reaction is exothermic, no evidence of thermal convection has been observed in the experimental cells. This conceptual model will serve to support a reactive transport model in order to quantify and optimize the amount of CO2 that can be captured in chrysotile milling waste piles.

Research and realization of ultrasonic gas flow rate measurement based on ultrasonic exponential model

For ultrasonic gas flow rate measurement based on ultrasonic exponential model, when the noise frequency is close to that of the desired signals (called similar-frequency noise) or the received signal amplitude is small and unstable at big flow rate, local convergence of the algorithm genetic-ant colony optimization-3cycles may appear, and measurement accuracy may be affected. Therefore, an improved method energy genetic-ant colony optimization-3cycles (EGACO-3cycles) is proposed to solve this problem. By judging the maximum energy position of signal, the initial parameter range of exponential model can be narrowed and then the local convergence can be avoided. Moreover, a DN100 flow rate measurement system with EGACO-3cycles method is established based on NI PCI-6110 and personal computer. A series of experiments are carried out for testing the new method and the measurement system. It is shown that local convergence doesn’t appear with EGACO-3cycles method when similar-frequency noises exist and flow rate is big. Then correct time of flight can be obtained. Furthermore, through flow calibration on this system, the measurement range ratio is achieved 500:1, and the measurement accuracy is 0.5% with a low transition velocity 0.3m/s.

Online Measurement of Gas and Liquid Flow Rate in Wet Gas Base on Single V-cone Throttle

Online Measurement of Gas and Liquid Flow Rate in Wet Gas Base on Single V-cone Throttle

Gas sampling system for matrix of semiconductor gas sensors

Semiconductor gas sensors are popular commercial sensors applied in numerous gas detection systems. They are reliable, small, rugged and inexpensive. However, there are a few problem limiting the wider use of such sensors. Semiconductor gas sensor usually exhibits a low selectivity, low repeatability, drift of response, strong temperature and moisture influence on sensor properties. Sample flow rate is one of the parameters that influence sensors response what should be considered in the measurement system. This paper describes low cost module for controlling measured gas flow rate. The proposed equipment will be used as a component of electronic nose system employed for classifying and distinguishing different levels of contamination in air.

On the accuracy of gas flow rate measurements in gas–liquid pipe flows by cross-correlating dual wire-mesh sensor signals

This article presents an assessment of the accuracy of gas flow rate measurement in gas–liquid pipe flows by cross-correlating dual wire-mesh sensor signals. The differences between the estimated and the actual gas superficial velocities in different flow regimes were analyzed. It was demonstrated that this gas flow rate measurement method is susceptible to significant systematic errors, some of which are inherent to the use of cross-correlation and others which are specific to wire-mesh sensors. It was concluded that this method would be accurate only for flow conditions within narrow ranges.

Evaluation of the Influence of the Composition of Natural Gas in the Ultrasonic Measurement of Flow in Flare-type Pressure Relief Systems

The objective of this work was to evaluate the influence of the composition of the natural gas on flow rate measurements in pressure relief flare systems, which is a legal requirement imposed by the Brazilian Regulator. The historical technical difficulties associated with collecting gas samples from flare systems, and the constant questions about the representativeness of the collected samples, are the main drivers motivating this study. The study indicated (i) a maximum error of 0.04% associated with ultrasonic measurement of gas flow rate when the actual gas composition was unknown; (ii) collected gas samples directly extracted from the flare systems do not necessarily represent the actual measured gas and (iii) the estimated maximum error associated with the totalization of the gas volume proved to be negligible when compared either to the total documented gas volume given by historical measurements or to the acceptable random errors that is inherent to this type of measurement system.

A new adaptive controller for bio-reactors with unknown kinetics and biomass concentration: Guarantees for the boundedness and convergence properties

In this work, an adaptive controller for bioreactors, using the measurement of output gas flow rate to handle the uncertainty on biomass concentration and kinetic rate is developed. A mass–balance model based on a unique reaction pathway to represent the input–output behavior is considered. Time-varying and unknown but bounded behavior of plant parameters, including the substrate concentration at the inflow and the yield coefficients is taken into account in the controller. The Lyapunov-like function method to develop the controller is used. A new method to handle the unknown time-varying behavior of the control gain is developed; with this method it is assured that the output tracks the desired reference with a user-defined tolerance and parameter drifting is avoided. The main contributions of the scheme with respect to closely related works are: (i) the exact values of the plant parameters are not required to be known; (ii) upper or lower bound related to the plant parameters is not required to be known; (iii) the time-varying behavior of plant parameters in the control design and in the convergence analysis is considered.

Simplified Method for Calculation of the Joule-Thomson Coefficient at Natural Gas Flowrate Measurement

This work deals with measurement of natural gas flowrate and volume by means of pressure differential devices. The existing methods for calculation of Joule-Thomson coefficient to be applied in pressure differential flowmeters are analyzed in the paper. A new method which uses a simplified set of parameters of gas composition, namely the density at standard conditions, the molar content of nitrogen and carbon dioxide, is developed by the authors. This method provides the possibility to calculate the Joule-Thomson coefficient within the pressure range from 0.1 MPa to 15.0 MPa and the temperature range from 250 K to 350 K. It was defined that for natural gas with density at standard conditions up to 0.75 kg/m3 and contents of nitrogen and carbon dioxide up to 5 % of each component, the relative error of the values derived according to the new developed method do not exceed 3.0 % in the specified ranges of temperature and pressure. The application of this method in calculators of flowrate and volume of natural gas will help to reduce the systematic error of flowrate and volume measurement caused by the distinction of gas temperature in the place of measurement downstream of primary device from gas temperature upstream of primary device. Подано аналіз існуючих методів розрахунку коефіцієнта Джоуля–Томсона, за результатами якого встановлено необхідність розроблення методу розрахунку на основі спрощеного набору параметрів складу газу. Представлено новий метод для розрахунку коефіцієнта Джоуля–Томсона у діапазоні абсолютного тиску газу від 0,1 МПа до 15 МПа та температури від 250 К до 350 К. Основне рівняння методу побудоване на основі принципу відповідних станів і описує залежність коефіцієнта Джоуля–Томсона від приведених температури та густини. Для обчислення приведеної густини газу запропоновано застосовувати розроблене авторами рівняння псевдокритичної густини природного газу. Виконано детальне тестування розробленого методу та встановлено, що для природних газів із густиною за стандартних умов rС£0,75 кг/м3 та вмістом азоту і вуглекислого газу до 5 % кожного, відносне відхилення значень методу від розрахункових значень коефіцієнта Джоуля–Томсона, отриманих за методом ISO 20765-1, не перевищує ±3,0% для вказаних діапазонів тиску та температури газу. Наведено приклади розрахунку систематичної похибки вимірювання витрати за допомогою витратоміра змінного перепаду тиску, зумовленої ефектом Джоуля–Томсона.

The wire-mesh sensor as a two-phase flow meter

A novel gas and liquid flow rate measurement method is proposed for use in vertical upward and downward gas–liquid pipe flows. This method is based on the analysis of the time history of area-averaged void fraction that is measured using a conductivity wire-mesh sensor (WMS). WMS measurements were collected in vertical upward and downward air–water flows in a pipe with an internal diameter of 32.5 mm at nearly atmospheric pressure. The relative frequencies and the power spectral density of area-averaged void fraction were calculated and used as representative properties. Independent features, extracted from these properties using Principal Component Analysis and Independent Component Analysis, were used as inputs to artificial neural networks, which were trained to give the gas and liquid flow rates as outputs. The present method was shown to be accurate for all four encountered flow regimes and for a wide range of flow conditions. Besides providing accurate predictions for steady flows, the method was also tested successfully in three flows with transient liquid flow rates. The method was augmented by the use of the cross-correlation function of area-averaged void fraction determined from the output of a dual WMS unit as an additional representative property, which was found to improve the accuracy of flow rate prediction.

Measurement of gas and liquid flow rates in two-phase pipe flows by the application of machine learning techniques to differential pressure signals

A new method for the determination of gas and liquid flow rates in vertical upward gas–liquid pipe flows has been proposed. This method consists of an application of machine learning techniques on the probability density function (PDF) and the power spectral density (PSD) of the normalized output of a differential pressure transducer connected to two axially separated wall pressure taps in the pipe. The two-phase flow regime was first identified by the application of the elastic maps method on the differential pressure PDF. The transducer signal was then pre-processed using Principal Component Analysis, and independent features were extracted using Independent Component Analysis. The extracted features were used as inputs to multi-layer back-propagation neural networks, which gave the phase flow rates as output. The present method was used to calibrate a differential pressure sensor to estimate the flow rates of both phases in air–water flow in a vertical pipe of diameter 32.5mm and in the pressure range from 100 to 140kPa. Predictions of the present method were in good agreement with direct flow rate measurements. Compared to previously used methods of feature extraction from differential pressure signals, the present method was the only one to have a good, consistent performance over all flow regimes and for all flow conditions encountered in this study.

A new correlation for wet gas flow rate measurement with Venturi meter based on two-phase mass flow coefficient

Much attention has been devoted to the study of the correlation of the wet gas flow rate measurement with a Venturi meter. However, up to now a widely-accepted correlation or model is not available. In this study, a new correlation for wet gas flow rate measurement with Venturi meter based on a two-phase mass flow coefficient was proposed. The two-phase mass flow coefficient was found to linearly increase with the Lockhart–Martinelli parameter and decrease with the increase of the gas-to-liquid density ratio. It also decreased with the gas densiometric Froude number increasing. The relationships of the two-phase mass flow coefficient with the Lockhart–Martinelli parameter, the gas densiometric Froude number and the ratio of gas to liquid density were concluded. Comparisons with the existing correlations showed that the new correlation predicted the wet gas flow rate more accurately than other correlations under the following conditions: the Lockhart–Martinelli parameter ranging from 0 to 0.3, the gas densiometric Froude number from 0.6 to 4.7, the ratio of gas to liquid density from 0.01 to 0.081 and the inlet diameter of the Venturi meter from 50 to 200mm. The present work provided an alternative approach to the study on the wet gas flow rate measurement with the Venturi meter.

AC Loss and Magnetic Shielding Measurements on 2GHTS Inductive Fault Current Limiter Prototype Modules

A new calorimetric measurement set up based on the measurement of nitrogen gas flow rate that results from the liquid nitrogen boil-off was established to measure ac losses in prototype superconducting modules of an inductive fault current limiter (iSFCL). A copper coil, to serve as the primary winding of iSFCL, was used to induce currents in the superconducting modules and drive them to a quench. The set up is suitable for superconducting devices of up to 360 mm in diameter and 400 mm in height. AC losses and magnetic shielding characteristics of the superconducting modules, made from wide second-generation high-temperature superconducting (2GHTS) tapes, were studied. Measurements were carried out at primary currents up to the quench current at frequencies from 10 Hz to 200 Hz. Dependence of primary quench current and ac losses on the frequency were measured. Implications of the extent of ac losses on the operating costs for maintaining liquid nitrogen in a practical iSFCL are discussed. The sudden change in the inductance of the primary coil and the corresponding change in the voltage during a quench of the superconducting modules were demonstrated.

Two-Phase Air–Water Slug Flow Measurement in Horizontal Pipe Using Conductance Probes and Neural Network

This paper presents a method to obtain gas and liquid flow rates of two-phase air-water slug flow in a horizontal pipe through conductance probes and neural network. Contrary to statistical features commonly used in other works, five characteristic parameters of the mechanistic slug flow model are extracted from conductance signals, i.e., translational velocity, slug holdup, film holdup, slug length, and film length, which are used as the neural network inputs. The translational velocity is obtained through cross correlation of signals from the two ring-type conductance probes that are placed apart at a fixed distance. A feedforward neural network is adopted to correlate the characteristic parameters of slug flow and the gas and liquid flow rates and further used as a prediction tool. The experimental results show that the neural network method is able to learn the implicit correlations between the characteristic parameters of slug flow and the corresponding gas and liquid flow rates. It provides a performance for measurement of gas and liquid flow rates in slug flow regime within ±10% of full scale.

Integrated Online Virtual Metrology and Fault Detection in Plasma Etch Tools

This paper presents an integrated virtual metrology (VM) and quality excursion detection framework for online implementation on a plasma etch tool. Traditional external metrology have inherent delays and are sparingly performed only on the most critical steps of manufacturing. To reduce metrology delay and limit the impact of quality excursion wafers, VM models can be used predict relevant quality outputs using process variables such as chamber pressure, gas flow rate, power level, and other plasma measurements. Although existing VM methods work well using off-line data sets, they face online implementation challenges, such as outliers and process drifts that degrade model accuracy. To develop an efficient and reliable framework for online VM monitoring, we combine data pretreatment using total partial least-squares projection, model updating with moving window PLS, and model feature selection using PLS variable importance in projections core filtering. The combined model can be implemented with low memory footprint and is also shown to be robust against drifts and disturbances. Modeling results from industrial data sets are shown to demonstrate the effectiveness of our approach.

Solid Mass Flowrate Measurement System Using the Double-Elbow Method

The gas-solid flow is widely used in the enterprises. The real-time solid mass flowrate measurement is an important role to the enterprise production. Based on the gas flowrate measurement principle of the Elbow, the new Double-Elbow real-time solid mass flowrate measurement method in the gas-solid flow is brought out in this paper. The new method can finger out the mass flowrate directly and need not measure the mixture density in advance. The instrument on measuring the solid mass flowrate is developed based on the new method; the instrument is using the 8031 as the MCU; the measurement result can be displayed on the LED. The experiment on measuring the solid mass flowrate is carried out in the pneumatic conveying system. The experimental results prove that the instrument can be real-time on-line measuring the solid mass flowrate.