Gas Flow Rate Measurement Research Articles

DEVELOPMENT OF UNSTEADY GAS FLOW GENERATOR WITH HIGHLY PRECISE INLET FLOW RATE CONTROL SYSTEM

In industry, an unsteady flow rate measurement of gases is becoming important increasingly. Our group has been developed an unsteady flow generator with an isothermal chamber for gases and showed that the calibration of the dynamic characteristics for the tested flow meter was effective. However, not only the measurement of the instantaneous flow rate value but also the evaluation of the time mean value in the unsteady flow becomes important in industry. And it was difficult to control precisely the time mean value of the generated flow rate using the former unsteady flow generator which we developed. In this research, to improve the precision of the generated flow rate with the unsteady flow generator, we suggest the inlet flow rate control method with the sonic nozzle and the high precise pressure control system and apply this method to the developed generator. Moreover, we perform the experiments and uncertainty analysis and confirm the effective of the suggested method.

KPIM of Gas Transportation: Robust Modification of Gas Pipeline Equations

KPIM of Gas Transportation: Robust Modification of Gas Pipeline Equations Studies of the flow conditions of natural gases in pipelines have led to the development of complex equations for relating the volume transmitted through a gas pipeline to the various factors involved, thus deciding the optimum pressures and pipeline dimensions to be used. From equations of this type, various combinations of pipe diameter and wall thickness for a desired rate of gas throughput can be calculated. This research work presents modified forms of the basic gas flow equation for horizontal flow developed by Weymouth and the basic gas flow equation for inclined flow developed by Ferguson. The modified equations incorporate non-iterative forms of the Colebrook-White friction factor into the original forms of the Weymouth's and Ferguson's equations. These modified equations thus eliminate the need for iteration in predicting the flow rate of gas through pipelines as is the case with their original forms when the Colebrook-White friction factor is used. The modified equations also have a wider range of application since the Colebrook-White friction factor is valid for turbulent gas flow as well as for gas flow in a transition zone. On comparing the results it can be seen that the modified Ferguson's equation gives a more accurate prediction of gas flow rates because it takes the pipeline elevation into account. Lower deviations from measured gas flow rates were observed with the modified Ferguson's equation than with the modified basic gas flow equation. The deviations observed using the modified Ferguson equation were found to range from -0.16% to +3.21%. Conclusively, these less cumbersome newly developed equations with high degree reliability will be useful in predicting the rates of gas flow for a wide range of its conditions, pipeline elevation and pipeline lengths.

Identifying Condensate Banking With Multiphase Flowmeters - A Case Study

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 105362, "The Identification of Condensate Banking With Multiphase Flowmeters - A Case Study," by B.C. Theuveny, SPE, P.D. Maizeret, SPE, N.S. Hopman, SPE, and S. Perez, Schlumberger, prepared for the 2007 SPE Middle East Oil & Gas Show and Conference, Bahrain, 11–14 March. Identifying condensate banking is a challenge. Large productivity losses can result if a condensate bank in the near-wellbore region is not detected early. One method that has been considered more theoretical than practical is detection of a leaner effluent stream at the wellhead during production. High-resolution measurement of subtle changes in the condensate/gas ratio (CGR) is essential for successful detection of condensate banking. The multiphase flowmeter can identify such a gradual change of the CGR. Introduction The main difficulty of testing gas wells with traditional test separators is determining accurate gas, condensate, and water flow-rate measurements. The short retention time in traditional test separators can lead to significant carryover of condensate into the gas line, resulting in underestimating the condensate rate and a potentially significant error in the gas rate. The level of error in the gas rate will depend on the measurement technology used. If a traditional orifice plate is used, the presence of condensate in the gas stream usually leads to an overestimate of the gas rate. The error in the gas measurement can be compounded with the accumulation of well liquids (i.e., water or condensate) in the tubing leads of the differential-pressure (DP) cell around an orifice plate, which can create large errors (usually identifiable in the raw data by a near-linear drift of the DP measurement). There also can be a significant amount of liquid trapped at the bottom of the pipe in front of the orifice plate, which can affect the flow-rate measurements adversely. Field identification of such a problem can be straightforward, but its remediation may be impossible during the course of the well-test operation. Liquid carryover in the gas line is a large problem when testing gas wells with small separators. Short retention time, combined with very small liquid-droplet size, can lead to the entrainment of 50% of the liquid through the gas outlet of the body of the separator. Attempts to reduce the losses of condensate have yielded various levels of success. These efforts include centrifugal separation at the inlet of test separator and use of mist extractors. Although these methods improve separation, the remaining liquid carryover is not necessarily negligible.

A New Method for the Flowrate Measurement of Gas–Liquid Two-Phase Flow

A new method for the flowrate measurement of gas-liquid two-phase flow is proposed. A multicircle flowmeter is designed based on the measurement principle of the conventional loop flowmeter. Four differential-pressure signals are obtained from the multicircle sensor at different positions. Multiparameters of the two-phase flow are obtained. The total flowrate measurement models of the two-phase flow are established using the average values of the differential-pressure signals. The volume fraction is estimated through the static and the dynamic differential-pressure analyses. The measurement of the liquid and gas flowrates is realized by association with the volume fraction. Experimental results show that the measurement accuracy supports the proposed methods.

A study of the critical nozzle for flow rate measurement of high-pressure hydrogen gas

The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ideal gas law. However, when the critical nozzle measures the mass flow rate of a real gas such as hydrogen at a pressure of hundreds bar, the discharge coefficient exceeds unity, and the real gas effects should be taken into account. The present study aims at investigating the flow features of the critical nozzle using high-pressured hydrogen gas. The axisymmetric, compressible Navier-Stokes computation is employed to simulate the critical nozzle flow, and a fully implicit finite volume method is used to discretize the governing equation system. The real gas effects are simulated to consider the intermolecular forces, which account for the possibility of liquefying hydrogen gas. The computational results are compared with past experimental data. It has been found that the coefficient of discharge for real gas can be corrected properly below unity adopting the real gas assumption.

Influence of the presence of an upstream annular liquid film on the wet gas flow measured by a Venturi in a downward vertical configuration

This work is included in an overall study linked to the production of gas from high pressure natural reservoirs. During the extraction of the gas, a liquid phase appears as condensates and water. In many applications the gas volume fraction (GVF) is high and the flow can be considered as a wet gas. The exact metering of the extracted gas necessitates gas/liquid separation. In order to reduce the costs, another solution is to measure the whole flow with a single flow meter. Among the different methods on the market, the use of the Venturi meter is nowadays still widespread. Different empirical correlations based on a Lockhart–Martinelli parameter were proposed to take into account the liquid phase, in the gas flow rate measurement. Nevertheless the accuracy of these correlations is not sufficient for allocation or reservoir monitoring. In fact these correlations do not take into account the influence of the two phase flow characteristics in the pipe upstream of the flow meter. To improve the metering method, a research program based on modelling and experimental tests has been developed by Total, Gaz de France and ONERA. In this paper, experimental results on the influence of the liquid film characteristics on the Venturi pressure drop ( Δ P ) are presented. Visualizations of the film upstream and inside the Venturi meter are shown. They are completed by film thickness wave amplitude and wavelength measurements. The Δ P measurements indicate that for the same Lockhart–Martinelli parameter, the characteristics of the liquid film have a great influence on the correlation coefficient. A one dimensional model is proposed which evaluates the influence of the different phenomena occurring between the two pressure taps.

High-Accuracy Wet-Gas Multiphase Well Testing and Production Metering

Summary Dedicated wet-gas flowmeters are now commercially available for the measurement of gas and liquid flow rates and offer a more compact measurement solution than does the traditional separator approach. The interpretation models of traditional multiphase flowmeters emphasize the liquid rate measurements and have been used to well test and meter mostly liquid-rich flow streams. These models were not developed for the measurement of gas flow rates, particularly those of wet gas. A new interpretation is described that allows a traditional multiphase flowmeter to operate in a dual mode either as a multiphase meter or as a wet-gas meter in 90 to 100% gas. The new interpretation model was developed for a commercially available multiphase flowmeter consisting of a venturi and a dual-energy composition meter. This combination results in excellent predictions of the gas flow rate; the liquid rate prediction is made with acceptable accuracy and no additional measurements. The wet gas and low-liquid-volume-fraction interpretation model is described together with the multiphase flowmeter. Examples of applying this model to data collected on flow loops are presented, with comparison to reference flow rates. The data from the Sintef and NEL flow loops show an error (including the reference meter error) in the gas flow rate, better than ±2% reading (95% confidence interval), at line conditions; the absolute error (including the reference meter error) in the measured total liquid flow rate at line conditions was better than ±2 m3/h (<±300 B/D: 95% confidence interval). This new interpretation model offers a significant advance in the metering of wet-gas multiphase flows and yields the possibility of high accuracies to meet the needs of gas-well testing and production allocation applications without the use of separators.

Influence of aprotic solvent on a signal of an amperometric sensor with Nafion ® membrane

The paper presents the results of investigation on characteristics of an amperometric sulphur dioxide sensor equipped with Nafion ® membrane and containing various amounts of dimethylsulphoxide within internal electrolyte. Sensitivity, response time to SO 2 concentration change, and influence of measured gas flow rate have been investigated and compared. The sensor utilizes a three-electrode system, where working and counter electrodes have been vacuum sublimation deposited on the membrane surface.

The indirect estimation of saturated hydraulic conductivity of soils, using measurements of gas permeability. I. Laboratory testing with dry granular soils

A comprehensive knowledge of soil hydraulic conductivity is essential when modelling the distribution of soil moisture within soil profiles and across catchments. The high spatial variability of soil hydraulic conductivity, however, necessitates the taking of many in situ measurements, which are costly, time-consuming, and labour-intensive. This paper presents an improved method for indirectly determining the saturated hydraulic conductivity of granular materials via an in situ gas flow technique. The apparatus employed consists of a cylindrical tube which is embedded in the soil to a prescribed depth. Nitrogen at a range of pressures was supplied to the tube and allowed to escape by permeating through the soil. A 3-dimensional, axisymmetric, steady-state, finite element flow model was then used to determine the value of the soil intrinsic gas permeability which produces the best fit to the pressure–air flow data. Saturated hydraulic conductivities estimated from the application of the gas flow technique to 5 granular soils covering a wide range of permeabilities were in close agreement with values determined using a conventional permeameter. The results of this preliminary study demonstrate the potential of this approach to the indirect determination of saturated hydraulic conductivity based on measurement of gas flow rates in granular and structured soils.

Imposed work of breathing during high-frequency oscillatory ventilation: a bench study

IntroductionThe ventilator and the endotracheal tube impose additional workload in mechanically ventilated patients breathing spontaneously. The total work of breathing (WOB) includes elastic and resistive work. In a bench test we assessed the imposed WOB using 3100 A/3100 B SensorMedics high-frequency oscillatory ventilators.MethodsA computer-controlled piston-driven test lung was used to simulate a spontaneously breathing patient. The test lung was connected to a high-frequency oscillatory ventilation (HFOV) ventilator by an endotracheal tube. The inspiratory and expiratory airway flows and pressures at various places were sampled. The spontaneous breath rate and volume, tube size and ventilator settings were simulated as representative of the newborn to adult range. The fresh gas flow rate was set at a low and a high level. The imposed WOB was calculated using the Campbell diagram.ResultsIn the simulations for newborns (assumed body weight 3.5 kg) and infants (assumed body weight 10 kg) the imposed WOB (mean ± standard deviation) was 0.22 ± 0.07 and 0.87 ± 0.25 J/l, respectively. Comparison of the imposed WOB in low and high fresh gas flow rate measurements yielded values of 1.63 ± 0.32 and 0.96 ± 0.24 J/l (P = 0.01) in small children (assumed body weight 25 kg), of 1.81 ± 0.30 and 1.10 ± 0.27 J/l (P < 0.001) in large children (assumed body weight 40 kg), and of 1.95 ± 0.31 and 1.12 ± 0.34 J/l (P < 0.01) in adults (assumed body weight 70 kg). High peak inspiratory flow and low fresh gas flow rate significantly increased the imposed WOB. Mean airway pressure in the breathing circuit decreased dramatically during spontaneous breathing, most markedly at the low fresh gas flow rate. This led to ventilator shut-off when the inspiratory flow exceeded the fresh gas flow.ConclusionSpontaneous breathing during HFOV resulted in considerable imposed WOB in pediatric and adult simulations, explaining the discomfort seen in those patients breathing spontaneously during HFOV. The level of imposed WOB was lower in the newborn and infant simulations, explaining why these patients tolerate spontaneous breathing during HFOV well. A high fresh gas flow rate reduced the imposed WOB. These findings suggest the need for a demand flow system based on patient need allowing spontaneous breathing during HFOV.

Intercomparison of gas flow-rate measurements at IMGC, Italy, and UASG, Germany, in the range from 10 −8 to 10 −3 Pa m 3/s

Primary standard gas flow meters are developed for various applications such as calibration of leak artefacts, generation of calibration pressures by dynamic gas expansion and calibration of secondary standard gas flow meters. The Istituto di Metrologia “G. Colonnetti” (IMGC), Italy, and the University of Applied Sciences Giessen-Friedberg (UASG), Germany, maintain primary flow meters based on different principles in order to measure small gas flows delivered either to vacuum (i.e. practically zero pressure) or to atmosphere (ambient pressure). The principle, design and properties of these flow meters are described. Comparison of the primary standard flow meters maintained at these laboratories was performed over a range from 3×10 −8 to 7×10 −4 Pa m 3/s with nitrogen, using a crimped capillary leak as a transfer standard. IMGC was the pilot laboratory. During the intercomparison, the transfer standard changed by ca. −2% for flow to vacuum and by ca. −4% for flow to atmosphere without obvious reason. The results of the intercomparison show that the laboratories agree within their expanded uncertainties over the measured range of gas flows.

The Effect of Diesel Fuel Sulfur Content on Particulate Matter Emissions for a Nonroad Diesel Generator

The effect of sulfur content on diesel particulate matter (DPM) emissions was studied using a diesel generator (Generac Model SD080, rated at 80 kW) as the emission source to simulate nonroad diesel emissions. A load simulator was used to apply loads to the generator at 0, 25, 50, and 75 kW, respectively. Three diesel fuels containing 500, 2100, and 3700 ppm sulfur by weight were selected as generator fuels. The U.S. Environmental Protection Agency sampling Method 5 “Determination of Particulate Matter Emissions from Stationary Sources” together with Method 1A “Sample and Velocity Traverses for Stationary Sources with Small Stacks or Ducts” was adopted as a reference method for measurement of the exhaust gas flow rate and DPM mass concentration. The effects of various parameters on DPM concentration have been studied, such as fuel sulfur contents, engine loads, and fuel usage rates. The increase of average DPM concentrations from 3.9 mg/Nm3 (n cubic meter) at 0 kW to 36.8 mg/Nm3 at 75 kW is strongly correlated with the increase of applied loads and sulfur content in the diesel fuel, whereas the fuel consumption rates are only a function of applied loads. An empirical correlation for estimating DPM concentration is obtained when fuel sulfur content and engine loads are known for these types of generators: Y = Zm (αX + β), where Y is the DPM concentration, mg/m3, Z is the fuel sulfur content, ppmw (limited to 500-3700 ppmw), X is the applied load, kW, m is the constant, 0.407, α and β are the numerical coefficients, 0.0118 ± 0.0028 (95% confidence interval) and 0.4535 ± 0.1288 (95% confidence interval), respectively.

The Joule–Thomson effect in natural gas flow-rate measurements

A numerical procedure for the calculation of the Joule–Thomson (JT) coefficient of a natural gas is derived. The AGA-8 extended virial-type characterization equation is used to calculate the rate of change of the compression factor with respect to the temperature at constant pressure. The DIPPR/AIChE generic ideal heat capacity equations are used to derive the molar heat capacity of a natural gas mixture. The accuracy of the natural gas flow-rate measurements, based on differential devices, is analysed with respect to the temperature drop, characterized by the JT effect. The results obtained are illustrated graphically. The procedure derived enables compensation for the JT effect in natural gas flow-rate measurements.

Development of Continuous Unsteady Flow Generator for Gases

Recently, unsteady flow rate measurement of gases is very important in the various industrial fields. However, there is no way to calibrate and to examine the unsteady flow rate of gases experimentally. As a result, there is no test bench for the unsteady fl ow rate measurement of gases.In this paper, we developed a new type of unsteady flow generator for gases. Especially, we realized to generate the unsteady fl ow of gases continuously. Then, we verified experimentally the generated unsteady flow rate using a laminar flow meter that has quick response up to 50 [Hz]. Moreover, we investigated the heat transfer in the generator. As a result, we confirmed that this generator could generate the oscillatory flow up to the frequency of 30 [Hz], and the target flow continuously for 30 minutes. The generator is effective for the verification of the various unsteady phenomena of gases experimentally.

E141 木質バイオマスの熱分解過程に及ぼす含水量の影響(一般セッション 改質)

Pyrolysis of woody biomass attracts attention as one of the methods of using biomass energy effectively. The phenomenon governing the pyrolysis are both heat transfer and chemical reactions. Although about 30% of moisture other than organic ingredients, such as cellulose and lignin, is included in the woody biomass, change of heat and mass transfer by moisture evaporation is hardly considered. In order to investigate about the influence moisture content of the biomass affects pyrolysis process, experiments (temperature and gas flow rate measurement, gas analysis) were conducted by dry and wet biomass.

Study on Direct Measurement of Diesel Exhaust Gas Flow Rate(Transient Characteristics of Ultrasonic Exhaust Gas Flowmeter)

The partial flow dilution system is one of the typical measurement systems for particulate matter emission from diesel engines. In this system, exhaust gas at a transient flow rate should be transferred to a dilution tunnel at a constant split ratio of exhaust gas. The current partial flow dilution system is used under steady-state engine operating conditions in lieu of direct flow rate measurement of exhaust gas. Therefore development of an exhaust gas flowmeter is indispensable in the partial flow dilution system for transient engine operating conditions. An ultrasonic exhaust gas flowmeter had been developed. As for the developed ultrasonic exhaust gas flowmeter, the transient characteristics measuring exactly and instantaneously temperature, pressure and velocity that are the components of the exhaust gas mass flow rate, has not been perfectly verified. We have inspected the transient characteristics of the developed ultrasonic exhaust gas flowmeter by using a laser Doppler velocimeter and numerical calculation. Consequently, an ultrasonic exhaust gas flowmeter has been confirmed to be capable of measuring the exhaust gas flow rate with sufficient transient characteristics.

Bubble Velocity and Size Measurement with a Four‐Point Optical Fiber Probe

AbstractThe possibility to measure the velocity and size of individual bubbles in a high‐void fraction bubbly flow is investigated by using a four‐point optical fiber probe. The air bubbles have an initial spherical equivalent diameter ranging from 4 to 10 mm and the void fraction is up to 0.3. Firstly, single bubble experiments show that intrusiveness effects, i.e. bubble deformations due to the probe, are negligible provided that the bubble approaches the probe at the axis of the central fiber. A selection criterion is utilized for multiple bubble experiments. A good compromise can be found between the required accuracy, the duration of the measurements and the number of validated bubbles required for reliable statistical averaging. In an air‐water high‐void fraction vertical bubbly pipe flow, the void fraction obtained with the instrument is found to be in good agreement with both local single‐fiber probe measurements, and with the volume average void fraction obtained from pressure gradient measurements. The area average volumetric gas flow rate, based on the bubble velocity and void fraction as measured with the four‐point probe, agree with the measured gas flow rate. Also, the liquid velocity is measured by means of a laser‐Doppler anemometer, to investigate the slip velocity. The results show that reliable and interesting measurements can be obtained by using a four‐point optical fiber probe in high void fraction flows.

Hydrodynamic and metallurgical characterization of industrial flotation banks for control purposes

An industrial flotation circuit consisting of five parallel rougher flotation banks, each bank provided with 9 cells of 42.5 m 3, was characterized. The air flow rate delivered over the cross-sectional area was directly measured using a simple device that provides a continuous measurement of local gas flow rate. The range of superficial gas rate was 0.8–1.2 cm/s. Gas holdup was measured using a pulp sampler providing estimations of local gas holdup of 15–22%. Bubble size distribution was measured using the UCT bubble size analyzer and the mean bubble size was compared with direct observations of the bubble size distribution near the pulp/froth interface. The Sauter average bubble size observed was 0.9–1.1 mm. The effective residence time of the liquid and solid phases was evaluated from residence time distribution (RTD) measurements, using radioactive tracers. The mean solid residence time was 5% lower than the mean liquid residence time. RTD of non-floatable mineral was also evaluated at different particle size classes. Measurements of grade, solid percentage and particle size profiles from the top to the bottom of different cells along the bank gave a complete diagnosis of particle distribution and mixing. The use of compressed air and the effect of pulp level on the bank flotation kinetics was evaluated. Thus, a useful correlation between mass recovery and enrichment ratio from industrial flotation cells was found for control purposes.

Measurement of gas yields and flow rates using a custom flowmeter

A simple gas collection apparatus based on the principles of a Torricelli tube has been designed and built to measure gas volume yields and flow rates. This instrument is routinely used to monitor and collect methane gas released during methane hydrate dissociation experiments. It is easily and inexpensively built, operates at ambient pressures and temperatures, and measures gas volumes of up to 7 L to a precision of about 15 ml (about 0.0025 mol). It is capable of measuring gas flow rates varying from more than 103 to less than 10−1 ml/min during gas evolution events that span minutes to several days. We have obtained a highly reproducible hydrate number of n=5.891 with a propagated uncertainty of ±0.020 for synthetic methane hydrate.

The evaluation of critical pressure ratios of sonic nozzles at low Reynolds numbers

A sonic nozzle is presently used as a reference flow-meter in the area of gas flow-rate measurement. The critical pressure ratio of the sonic nozzle is an important factor in maintaining its operating condition. ISO 9300 suggested that the critical ratio of a sonic nozzle should be a function of area ratio. In this study, 13 nozzles designed according to ISO 9300, with diffuser half angles of 2°–8° and throat diameters of 0.28 to 4.48 mm were tested. The testing result for the angles of 2°–6° are similar to that of ISO 9300. But the critical ratio for the nozzle of 8° decreases by 5.5% in comparison with ISO 9300. However, ISO 9300 does not predict the critical pressure ratio at Reynolds numbers lower than 10 5. To express the critical pressure ratio of sonic nozzles at low Reynolds numbers, it is found that the critical pressure ratio should be related as a function of Reynolds number rather than area ratio, as used by ISO 9300. A correlated relation of critical pressure ratios and low Reynolds numbers for small sonic nozzles is suggested in this investigation, with an uncertainty of ±3.2% at 95% confidence level.