Gas Flow Rate Measurement Research Articles

Leveraging long short‐term memory networks and transfer learning for the soft‐measurement of flue gas flowrate from coal‐fired boilers

AbstractThe dynamic operation and deep peak‐shaving of power‐generating units cause significant fluctuations in flue gas flowrate, thus affecting the accuracy of CO2 emissions measured by continuous emission monitoring systems (CEMS). This study established a long short‐term memory network with an attention mechanism (LSTM‐AM) for the soft measurement of the flue gas flowrate in real‐time. First, flue gas flowrate data and continuous operation parameters over 25 days were sampled from a typical 660 MW coal‐fired boiler in China. Then, a carbon balance model was established to verify the data reliability. The LSTM‐AM model was trained and testified at the 660 MW coal‐fired boiler. Results show that the LSTM‐AM model significantly surpassed the pristine LSTM model without attention, the convolutional neural network (CNN) with LSTM, and the static support vector regression (SVR) model in the real‐time prediction of flue gas flowrate. Finally, the LSTM‐AM model was generalized to a 630 MW coal‐fired power unit via transfer learning, which was further demonstrated to outperform the model re‐trained from scratch. This work manifests the feasibility of deep learning for the soft measurement of flue gas flowrate, which is promising to solve data‐lagging issues when measuring CO2 emissions from coal‐fired power plants.

A simplified open flux chamber method for the measurement of greenhouse gas emissions from activated sludge reactors

ABSTRACT Measuring greenhouse gas emissions from wastewater treatment plants is of utmost importance in the context of climate change. However, due to their variability and complexity, it is a particularly challenging task in aerated reactors. The current methods involve capturing gas emissions from the water surface, measuring gas flow rates, and determining the concentration of the emitted gas at that location. Our study proposes a new, more efficient method that eliminates the need for gas flow rate measurements and additional equipment. The proposed technique uses a gas analyzer and a specially designed floating chamber to measure the transient trend of gas concentration within the chamber from the moment it is deployed to when it reaches a new steady state. Our research shows that this method accurately determines methane and carbon dioxide emissions from aerated reactors and potentially other gases emitted in wastewater treatment plants. It is cost effective, versatile, and simplifies the measurement process. This method facilitates the assessment of greenhouse gas emissions in wastewater treatment plants. Our findings are backed by comprehensive testing in the aeration tanks of a full-scale activated sludge plant, across diverse conditions, including fine- and coarse-bubble aeration.

Accurate measurement of micro gas flow rates for comprehensive evaluation of polymeric membranes applicable in gaseous separations

ABSTRACT The time-lag method is the most useful technique to determine gas permeability, diffusivity, and solubility. However, it is difficult to evaluate the transport properties of the membrane accurately because gas permeability depends on the technique used to assess gas flow. The significance of the present study is to design an economic isochoric apparatus to accurately measure micro-range gas flow rates ranging from 10−6 to 10 cm3(STP) s−1. A strategic procedure is demonstrated to eliminate possible artifacts while conducting the gas permeation experiments, including utilizing downstream pressure rise profiles to identify nanoscale defects as well as transient and steady-state permeation. An indigenous apparatus was developed to estimate the polymeric intrinsic properties of the dense and thin-film composite membranes. The device has been successfully used to measure the gas permeation flow rate ranging from 1 × 10−5 to 1 × 10−1cm3 (STP) s−1, which indicates the broad applicability and reproducibility of the data suggesting the reliability of the designed apparatus. Permeation flow rates of binary mixtures of CO2/CH4 through the defect-free membranes were compared with the numerical estimations to validate the measured transport properties.

Devices and methods for wet gas flow metering: A comprehensive review

Wet gas is commonly encountered in various industries, including energy, chemical, and electric power sectors. For example, natural gas extracted from production often contains small amounts of liquid, such as water and hydrocarbon condensates, which classifies it as wet gas. The presence of liquid within the gas poses challenges for accurate flow measurement. To improve the performances of wet gas flow metering methods, significant research and development efforts have been invested into the wet gas flow metering technologies due to their vital importance in the production, transfer, and trade benefits.This paper presents a comprehensive overview of the recent development of wet gas flow metering. Firstly, a comprehensive discussion of the Lockhart-Martinelli parameter (Xlm) and its relation to the gas void fraction (αg) is presented, which was mostly overlooked in previous wet gas research work. The occurrence of various flow patterns in wet gas conditions at different orientations (horizontal and vertical) was explored. Following an investigation of pressure impact on the wet gas flow patterns and development of the wet gas regions, a different test matrix for further research work was suggested. After a novel classification of wet gas measurement methods, the paper offers a detailed comparison of differential pressure (DP) meters including Venturi, Cone meter, and orifice meters, by considering both liquid and gas flow rate measurements. Secondly, the paper discusses and compares vortex flow meters, Coriolis and ultrasonic meters in comparison to DP meters. Notable phase fraction meters are also examined and compared to one another. Thirdly, the paper reviewed the concept of existing and potential hybrid wet gas meters, conducting a detailed discussion and comparison with commercial solutions by evaluating their ranges and accuracies. This assessment provides valuable insights into the capabilities of these hybrid meters, highlighting their potential to enhance the measurement of wet gas flow rates.

Hydromechanical characterization of gas transport amidst uncertainty for underground nuclear explosion detection

Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone, surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions (UNEs). However, the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved, including the generation of complex fracture networks, reactivation of natural fractures and faults, and thermo-hydro-mechanical-chemical (THMC) coupling of radionuclide gas transport in the subsurface. In this study, we provide an experimental investigation of hydro-mechanical (HM) coupling among gas flow, stress states, rock deformation, and rock damage using a unique multi-physics triaxial direct shear rock testing system. The testing system also features redundant gas pressure and flow rate measurements, well suited for parameter uncertainty quantification. Using porous tuff and tight granite samples that are relevant to historic UNE tests, we measured the Biot effective stress coefficient, rock matrix gas permeability, and fracture gas permeability at a range of pore pressure and stress conditions. The Biot effective stress coefficient varies from 0.69 to 1 for the tuff, whose porosity averages 35.3% ± 0.7%, while this coefficient varies from 0.51 to 0.78 for the tight granite (porosity <1%, perhaps an underestimate). Matrix gas permeability is strongly correlated to effective stress for the granite, but not for the porous tuff. Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event: (1) The porous tuff shows apparent fracture dilation or compression upon stress changes, which does not necessarily change the gas permeability; (2) The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement; and (3) Hydromechanical coupling among stress states, rock damage, and gas flow appears to be stronger in tight granite than in porous tuff.

Design and development of a low-cost non-intrusive passive acoustic sensor

In this paper, we report on the development and performance study of a low-cost non-intrusive passive acoustic sensor (NIPAS), suitable for gas flow rate measurement and monitoring in pipelines and other similar applications. Detailed information on the design considerations, development, construction, and assembly of the sensor and its unit are also provided in this paper. The complete NIPAS unit is made up of two sensor heads fixed at the test section of a designed flow loop to receive the acoustic emission signals generated from the varying gas flow rate and processed by a control unit for data collection and analysis. The electronic unit was enclosed in a Perspex casing for easy interfacing and protection. Observations on the performance of the developed NIPAS are presented as a voltage-time signal and analyzed in both time and frequency domains. Calibration of the NIPAS was done using suitable statistical features, which are the mean, standard deviation, and coefficient of variation of the signals. Results obtained indicate that the developed NIPAS unit shows proof of concept and it is suitable for measuring and monitoring gas flow rates in pipes.

Rapid On-Line and Non-Invasive Flow Rate Measurement of Gas–Liquid Slug Flow Based Only on Basic Differential Pressure Fluctuations

The gas–liquid two-phase flow is widely encountered in many industrial applications, and its on-line and non-separation flow rate measurement for each phase has plagued the industry for many years. Based on the one-to-one correspondence between differential pressure fluctuations and the movement of Taylor bubbles (TBs) and liquid slugs (LSs), a novel method is proposed to measure the flow rate of gas–liquid slug flow in this article. Theoretical correlations between flow characteristics (velocity, length, and void fraction) and differential pressure fluctuations were quantitatively analyzed by experiments, and the gas–liquid ratio was found to be linearly related to the length ratio of TB and LS. The gas flow rate and liquid flow rate were predicted based on the measured flow characteristics. Experimental tests on air–water two-phase flow show that the proposed method and correlations were effective, and the average relative errors (AREs) in the gas flow rate and liquid flow rate are 5.50% and 5.62% with maximum values of 11.46% and 12.06%, respectively, under the conditions of 0.16–0.56 m/s of air superficial velocity and 0.23–0.48 m/s of water velocity. This method is based only on the differential pressure fluctuations and is on-line, non-separation, noninvasive, and radiation-free, which provides a new cost-effective solution for the flow rate measurement of industrial two-phase flows.

Study of the factors influencing the over-reading characteristics of the precession Venturi

In the energy industry, such as the gas field, precise measurement of wet gas is becoming increasingly crucial. Many studies have focused on the over-reading (OR) of throttle flowmeter in wet gas measurement. By using the dimensional analysis method, we proposed a precession Venturi and established a new OR correlation based on the gas Froude number, liquid-gas density ratio, and the Lockhart–Martinelli parameter. Experimental tests of air-water flow were conducted, and the relationships between differential pressure and OR with liquid volume fraction were investigated at various pressures and superficial gas velocities. The experimental results show that the uncertainty of gas flow rate measurement is in the range of 0.35%–0.56%, and 90.8% of the points are in the range of 0.35%–0.45%, with a relative error band of ±2.94% calculated by the OR correlation at a confidence probability of 95.5%.

Measurement of Gas Flow Rate at Gasification of Low-Melting Materials in a Flow-Through Gas Generator

A semi-empirical method is proposed for determining the rate of gas production in a flow-through gas generator (GG) with the allocation of a part of the gas flow produced by gasification of a low-melting solid material (LSM) in the total gas flow rate through the GG. The method is verified by test fires with polypropylene sample gasification by hot air under conditions of incoming supersonic flow with Mach number 2.43, 2.94, and 3.81 and stagnation temperature 600–700 K. The mean flow rates of gasification products obtained in test fires were 0.08 kg/s at Mach 2.43, 0.10 kg/s at Mach 2.94, and 0.05–0.02 kg/s at Mach 3.81. For obtaining 1 kg of gasification products in the test fires there was a need of 1.61 to 2.86 kg of gasifying agent.

Construction of natural gas energy-measuring system in China: A discussion

During the 13th Five-Year Plan, China's natural gas industry developed rapidly, and a diversified supply and marketing pattern was formed, including domestic conventional gas, unconventional gas (shale gas, tight sandstone gas, coalbed methane, etc.), coal-based synthetic natural gas, imported LNG and imported pipeline gas. The gross calorific value of gas sources ranged from 34 MJ/m3 to 43 MJ/m3, and the maximum difference of calorific value between different gas sources exceeded 20%. On May 24th, 2019, the National Development and Reform Commission and other three ministries/commissions jointly issued the Supervision Regulation on the Fair Access of Oil and Gas Pipeline Network Facilities and required that a natural gas energy measuring and pricing system shall be established within 24 months from the implementation date of this Regulation. In order to speed up the construction of China's natural gas energy measuring system, this paper summarizes domestic achievements in the construction of natural gas energy measuring system from the aspects of value traceability and energy measurement standard, and analyzes natural gas flowrate measurement technology, calorific value determination technology, value traceability, localization, intelligentization and application technology of key energy measurement equipment, natural gas pipeline network energy balancing technology based on big data analysis, multi-source quality tracking and monitoring technology, and energy measurement standard system, the need of new energy detection and measurement technology, and put forward strategy for the development of natural gas measuring in China. And the following research results are obtained. First, China's natural gas energy measuring system can basically meet the requirements of implementing natural gas energy measurement, but it still falls behind the international leading level in terms of calibration and application of high-level flowmeter (such as 0.5 class), high-accuracy gas reference material, level of calorific value reference equipment, and measurement standard system, and needs to be further improved. Second, it is necessary for China to speed up the research and application of the localization and intelligentization technologies of key energy measurement equipment. Third, natural gas pipeline network shall be equipped with measurement check method, energy balancing system based on big data analysis, and multi-source quality tracking and monitoring system, so that the energy transmission loss index of natural gas pipeline network can be superior to the international leading level (0.10%). Fourth, to realize the large-scale application of hydrogen energy and bio-energy and the mixed transportation of hydrogen, bio-methane and natural gas, it is necessary to carry out research on new technology and standardization of hydrogen/bio-methane blended natural gas detection and measurement.

Modelling oil and gas flow rate through chokes: A critical review of extant models

Oil and gas metering is primarily used as the basis for evaluating the economic viability of oil wells. Owing to the economic implications of oil and gas metering, the subject of oil and gas flow rate measurement has witnessed a sustained interest by the oil and gas community and the academia. To the best of the authors' knowledge, despite the growing number of published articles on this subject, there is yet no comprehensive critical review on it. The objective of this paper is to provide a broad overview of models and modelling techniques applied to the estimation of oil and gas flow rate through chokes while also critically evaluating them. For the sake of simplicity and ease of reference, the outcomes of the review are presented in tables in an integrated and concise manner. The articles for this review were extracted from many subject areas. For the theoretical pieces related to oil and gas flow rate in general, the authors relied heavily upon several key drilling fluid texts. For operational and field studies, the authors relied on conference proceedings from the society of petroleum engineers. These sources were supplemented with articles in peer reviewed journals in order to contextualize the subject in terms of current practices. This review is interspersed with critiques of the models while the areas requiring improvement were also outlined. Findings from the bibliometric analysis indicate that there is no universal model for all flow situations despite the huge efforts in this direction. Furthermore, a broad survey of literature on recent flow models reveals that researchers are gravitating towards the field of artificial intelligence due to the tremendous promises it offers. This review constitutes the first critical compilation on a broad range of models applied to predicting oil and gas flow rates through chokes.

Online Measurement of Gas and Liquid Flow Rates in Wet Gas Using Vortex Flowmeter Coupled With Conductance Ring Sensor

Wet gas flow commonly exists in several industries. The online measurement of gas and liquid flow rate is beneficial for economic efficiency. A combination of vortex flowmeter and liquid film sensor was proposed for two-phase flow measurement of wet gas. The specific form is as follows: the dual-modality sensing system was designed and calibrated by an annular mist flow loop. The fluid materials are pure air and water liquid. The ranges of operating pressure, the superficial gas velocity, and superficial liquid velocity are 1.5 bar–3.5 bar, 18.86–37.73 m/s, and 0.0028–0.028 m/s. Then the function relations of liquid film thickness and vortex frequency, with gas and liquid Weber numbers were built, respectively. Finally, a novel model for calculating gas and liquid flow rates in wet gas measurement was established, and solved by the Newton iterative algorithm. It showed that the percentage error (PE) of gas flow rate predicted by the model is within ±1.5%, and the mean absolute percentage error (MAPE) is 0.55%. The full-scale PE of liquid flow rate is within ±5% and the MAPE is 3.48%. The data show that this solution for gas and liquid flow rates measurement of wet gas by combining a vortex flowmeter with a conductance ring sensor is feasible.

An Analytical Method for Gas Flow Measurement Using Conservative Chemical Elements

Mass flow meters (MFMs) are widely used to secure reliable flow rates based on the mass value of the gas being measured. However, chemical reactions produce various kinds of gases, and their composition also changes in real time. Thus, there may be a large deviation in the gas flow if the gases’ composition and its mixing ratio are not known. In this study, we derived a gas flow rate measurement method using a chemically stable chemical specie and verified the precision of the proposed method through comparative analysis with an MFM. The flow rate by this method showed reliable results in both single and mixed gases. Notably, the results were within ±2.74% of the injected flowrate values in the gas mixtures. This method is expected to be able to fundamentally overcome the limitations of the mechanical flowmeter because it is not affected by changes in gas composition or mixing ratio during the reaction.

Calibration of gas flow meters using choked flow and an evacuated vessel

The measurement of gas flow rates is of great importance in a wide range of modern technologies. This paper introduces a simple, yet accurate technique for in-house calibration of gas FMs (mass and volumetric) even under harsh environmental conditions such as encountered during field measurement campaigns. The method requires only readily available, low cost components: a vessel of known volume, an air pump, a pressure sensor and a metal plate orifice or a needle valve to act as a CO. The unique property of choked flow in the CO is used here for flow calibration. In the method presented here a vessel is evacuated to below the critical pressure (<0.53 of upstream pressure) and then allowed to refill with ambient air (or some other process gas) under so-called choked flow conditions through the CO. The method presented here leverages that the flow rate upstream of the CO is not only constant but readily determined from (a) the known V VESS, (b) the measured time rate of change of the absolute pressure in the vessel and (c) the ideal gas law. This calculated flow rate can be used for calibration of FMs. The accuracy of the method depends only on the accuracy of the pressure measurement, the timer and the value of the V VESS. The flow rate computed in this way is found to be in excellent agreement (typically 1% difference) with the flow rate measured by a soap film FM (Gilibrator). As expected from theory this method is found to work for all kinds of CFRs (here: various types of metal plate orifices and needle valves were tested), gas types (here: air, Argon, and CO2) and upstream pressures (here: between 650 hPa and 1400 hPa). The accuracy of this technique (∼1%) is as good as that of standard volume displacement methods (e.g. soap film FMs) (typically 1% difference), the standard of laboratory-based flow calibrators, but less expensive and more suitable for harsh environments.

Invariant method for measuring wet gas flow rate

The article deals with one of the important tasks of modern flow measurement, which is related to the measurement of the flow rate and the amount of wet gas. This task becomes especially important when it becomes necessary to obtain information about the separate amount of the dry part of the gas that is contained in the form of a mixture in the wet gas stream. The paper presents the principle of operation and structure of the invariant system for measuring the flow rate of wet gas, which is based on the combined use of differential pressure flowmeters and Coriolis flowmeters. The operation of the invariant wet gas flow rate measurement system is based on the simultaneous application of the multichannel principle and the partial flow measurement method. Coriolis flowmeters and the differential pressure flowmeter are used as the main elements of the system. The proposed measurement system does not offer applications for gases with abundant drip humidity. The article provides information about the test results of the proposed invariant system. The estimation of the metrological characteristics of the invariant system when measuring the flow rate of wet gas is given. The obtained test results of the invariant wet gas flow rate measurement system are relevant for natural gas production, transportation, and storage facilities.

A modified model for wet gas flowrate measurement considering entrainment downstream of a cone meter

To develop a reliable wet gas flowrate measurement model, the relationships between pressure drop characteristics and entrainment downstream of the cone are investigated experimentally. The equivalent diameter ratio of the cone is 0.45. The experimental fluids are air and tap water with XLM in the range of 0–0.3. The two-phase mass flow coefficient and pressure loss ratio are employed to establish the measurement model. The piecewise characteristics of pressure loss ratio are disclosed innovatively, which is explained by the different intensity of entrainment downstream of cone caused by gas-liquid jetting. A simplified method for evaluating the degree of entrainment is proposed to facilitate the establishment of the modified measurement model. Under the present experimental conditions, the relative error of liquid fluctuates within ±20% when XLM is larger than 0.02, and the relative error of gas flowrate is within ±5%. Compared with the model without piecewise consideration, the relative error of the liquid flowrate of the modified model reduces obviously under low wetness conditions (0.02<XLM<0.1). The modified measurement model provides a reliable and cost-effective technology for wet gas flowrate measurement.

Uncertainty analysis of stack gas flow measurements with an S-type Pitot tube for estimating greenhouse gas emissions using a continuous emission monitoring system

In order to reduce greenhouse gas (GHG) emissions from producers in the energy and industrial fields to mitigate climate change more effectively, accurate and reliable studies of methods capable of estimating GHG emissions with proper uncertainty levels should initially be carried out. Continuous emission monitoring systems (CEMS) directly measure GHG emissions by measuring the GHG concentrations and volumetric flow rates of flue gases in smokestacks. Most studies of CEMS have tended to focus on the accuracy and uncertainty levels associated with GHG concentrations rather than on volumetric flow measurements. Particularly, the uncertainty associated with volumetric gas flow measurements by CEMS at a smokestack considering the individual plant must be determined to reduce the overall uncertainty. In the present study, the uncertainties of stack gas flow measurements with an S-type Pitot tube to estimate GHG emissions by CEMS are evaluated by applying the GUM and Monte Carlo methods to an on-site smokestack of an energy power plant. Velocity measurements in the stack were conducted using an S-type Pitot tube mainly used in Korea. The mathematical model equations of the accumulated volumetric gas flowrate measurements for estimating GHG emissions by CEMS are expressed in the form of detailed uncertainty equations by GUM. In the uncertainty evaluations by GUM, the combined standard uncertainty equation is expressed with the average gas flow velocity, stack diameter, static pressure, temperature and water content. The relative expanded uncertainty for volumetric gas flowrate measurements with an S-type Pitot tube in a smokestack by GUM is estimated to be 3.81% for a coverage factor (k = 2) at a confidence level of approximately 95%. In addition, the Monte Carlo method was applied to evaluate the associated uncertainty of volumetric gas flowrate measurements by an S-type Pitot tube for comparison with the results by the GUM method. The results of the uncertainty evaluations by GUM and MCM show good agreement, with only a 0.05% difference in the uncertainty outcomes.

Structural Design for ITER Gas Injection System Gas Fueling Gas Valve Box

The ITER gas injection system delivers gases from the tritium plant to the vacuum vessel, fueling pellet injection system, and neutral beam for plasma operation and fusion power shutdown. In this system, the gas fueling (GF) gas valve box (GVB) is an indispensable part that mainly provides functions of gas throughput control and measurement of gas pressure, flow rate, and temperature. The preliminary structure design is largely driven by the requirements of magnetic field compatibility and limited integration space. A strong magnetic field of over 0.2 T exists around the GVB locations, so a magnetic shielding design is required to ensure the normal function of susceptible components. Instead of the previous overall shielding, a local magnetic shielding has been developed by a validated analysis method. As a result, the total weight of the shield has been reduced from over 7000 kg to about 200 kg. Furthermore, considering the limited space reservation, a highly compact flat layout for the GF GVB has been developed to ensure enough maintenance space in front of it. In addition, other requirements such as structure integrity under various load combinations, leak detectability, in situ maintainability, etc., have all been taken into account.

Flexible ZnO thin film acoustic wave device for gas flow rate measurement

In this work, ZnO/Al thin film based flexible acoustic wave devices are demonstrated for their applications in gas flow rate measurements based on the changes in temperature of the devices. A good sensitivity of gas flow rate can be achieved, mainly because thin film based device has a large temperature coefficient of frequency of ∼280 ppm K−1, owing to the large coefficient of thermal expansion of aluminum foil. A heat source is used to enhance the sensitivity of the thin film device by introducing a temperature offset. The flexible acoustic wave device shows a high sensitivity, fast response times, and a good repeatability for measurement of the flow rate of nitrogen. When the flexible acoustic wave device is bent and attached onto the inner wall of a pipe, the device exhibits good performance for monitoring the gas flow rate, demonstrating its applications of flow rate measurement on curved or randomly shaped surfaces.

Low cost thermal transient anemometer for challenging gas flow rate measurements

Few commercially available gas flow rate measurement devices can be employed in applications with strict pressure drop allowances, high working pressures, or corrosive working fluids. Additionally, most measurement approaches (e.g., turbine, rotameter, thermal dispersion) have limited turn-down ratios, generally less than 50. Here, a new economical and mechanically simple thermal transient anemometer design is proposed and evaluated for internal gas volumetric flow measurement. The flow meter operates through cyclical electrical heating and convective cooling of a thermocouple probe. Flow rates are correlated with average cooling-period temperatures. Heating and cooling profiles are dynamically adjusted during operation, permitting relatively good accuracy and a large turn-down ratio (450). The objective of this investigation is to model, design, and demonstrate the operation of the anemometer using air as working fluid. The anemometer has a measurement range of 0.5–226.5 l min−1 with free stream temperatures varying between 22–26°C. A segmented numerical model, which includes the varying heating loads and velocity profiles in the working fluid, is developed and validated.