Gas Flow Rate Measurement Research Articles

NOX selective catalytic reduction control based on simple models

Abstract In the paper, a new approach to the control of the selective catalytic reduction process of NO X is presented. The reduction process can be efficiently controlled using a combination of feed-forward and feed-back control structures. However, this approach requires expensive measurement equipment. It is shown that measurement of nitric oxide concentration at the input of the catalytic converter and measurement of the flue gas flow rate can be successfully substituted by corresponding “software sensors”. The software sensors are based on simple mathematical models and on measurements of excess oxygen concentration in flue gas and the fuel flow rate which are usually parts of already available standard combustion control system equipment. In the paper the complete derivation of the required mathematical models is given, and the proposed new control structure is described. The structure is tested using simulation and implemented on an industrial pilot plant.

マイクロフローセンサを用いた管内一点の流速からの気体の振動流量計測

マイクロフローセンサを用いた管内一点の流速からの気体の振動流量計測

Mechanisms and Modeling of Liquid Steel Decarburization below 10 ppm Carbon

Steel grades for packaging or automotive industry applications require ultra low carbon levels and carbon contents below 10 ppm have to be obtained in the industrial decarburization reactor (tank degasser or vacuum circulation degasser, known as RH). In the ultra low carbon range (below 10 ppm in the vacuum vessel), the decarburization kinetics cannot be obtained from the analysis of metal samples but can be deduced from continuous exhaust gas analysis and flow rate measurements. This was done on an industrial RH-OB degasser and a reliable and precise measurement of reaction rates in the ultra low carbon range was obtained. The rate was evaluated by an overall volumetric coefficient of decarburization ak⁄S. A model of decarburization kinetics in vacuum vessel has been developed at IRSID based on a physical description of three different reaction sites: spontaneous CO boiling in metal layer just beneath bath surface where carbon and oxygen contents are in excess with respect to equilibrium CO partial pressure, decarburization by purging gas in zones where metal and injected gas bubbles are in contact and decarburization of metal drops projected in vacuum vessel by bubble bursting. The experimental results indicate that CO boiling is responsible for the largest part of decarburization, but, the decarburization of metal drops projected in vacuum vessel is dominating below 10 ppm. The dynamic modeling of the process describes simultaneously the evolution of vessel pressure, oxygen and carbon contents. It explains with very good accuracy the experimental results and is used to define optimal process parameters for industrial treatments.

Evaluation of Critical Pressure Ratios Sonic Nozzle at Low Reynolds Numbers

A sonic nozzle is used as a reference flow meter in the area of gas flow rate measurement. The critical pressure ratio of sonic nozzle is an important factor in maintaining its operating condition. ISO9300 suggested the critical pressure ratio of sonic nozzle as a function of area ratio. In this study, 13 sonic nozzles were made by the design of ISC9300 with different half diffuser angles of 2。 to 8。 and throat diameters of 0.28 to 4.48 mm. The test results of half diffuser angles below 8。 ar quite similar to those of ISO9300. On the other hand, the critical pressure ratio for the nozzle of 8。 decreases by 5.5% in comparison with ISO9300. However, ISO9300 does not predict the critical pressure ratio at lower Reynolds numbers than 10(sup)5. Therefore, it is found that it is a better way for the flow of low Reynolds number to express the critical pressure ratio of sonic nozzle as a function of Reynolds number than area ratios. A correlation equation of critical pressure is introduced with uncertainty 3.2 % at 95% confidence level.

In situ rock salt permeability measurement for long term safety assessment of storage

Abstract A field test was carried out in the Amelie Mine owned by Mines de Potasse d'Alsace (MDPA, France) for the purpose of measuring rock salt permeability away from underground facilities. The selected salt bed is about 1 m thick and located 16 m away from the gallery floor. The permeability was measured by means of nitrogen and saturated brine injection. Theoretical studies indicated that in order to control the `disturbing effects' (thermal effects, chemical reaction between halite and brine), the work should be done at constant temperature and pressure. The field experiment results confirm that rock salt is permeable to gas and brine, even relatively far from underground openings. The measurements of the tests with brine were interpreted satisfactorily by a model based on Darcy's law, with an intrinsic permeability value of 2×10 −21 m 2 and an initial pore pressure value of 1 MPa. Interpretation of the measured gas flow rate shows that: (a) after brine percolation, the capillary pressure effect is significant and (b) gas migration in salt is not controlled by Darcy's law; the Knudsen effect and partial saturation may play an important role.

Development of the Calibration Facility for Small Mass Flow Rates of Gases and the Sonic Venturi Nozzle Transfer Standard.

A calibration facility based on gravimetric method has been developed at NRLM for small mass flow rates of gas. This calibration facility establishes a primary gas flow rate measurement standard in Japan with an extended standard uncertainty of 0.12 percent at maximum, in mass flow rates from 0.01 g/min to 50 g/min for nitrogen. Five sonic Venturi nozzles were tested using this facility and the results showed that they can work well as a flow transfer standard for small mass flow rates. These sonic Venturi nozzles can be used to establish flow transfer standards within an extended standard uncertainty of 0.15 percent.

Numerical simulations of gas exchange in leaky grain silos, using measured boundary conditions

Commercial software was used to predict the gas exchange in leaky grain silos during modified atmosphere storage. Local hourly weather data and measured gas flow rate are used as model inputs to simulate two possible control strategies. Simulations are done for a purged grain silo with and without a maintenance flow rate. Predicted temperatures and gas mass fractions are presented which highlight the importance of a maintenance flow. Good agreement is shown with measured data taken inside a 450 tonne grain silo that is subjected to a constant gas flow. Improvements to the model and to the experimental procedures are suggested.

Parametric studies of the Hall current plasma thruster

The Hall current plasma thruster accelerates a plasma jet by an axial electric field and an applied radial magnetic field in an annular ceramic channel. A relatively large current density (>0.1 A/cm2) can be obtained as the acceleration mechanism is not limited by space charge effects. Such a device can be used as a small rocket engine on board spacecraft with the advantage of a large jet velocity compared to conventional rocket engines (10000–30000 m/s versus 2000–4800 m/s). An experimental Hall thruster was constructed and operated in a broad range of operating conditions and under various configuration variations. Electrical, magnetic and plasma diagnostics, and as well accurate thrust and gas flow rate measurements, have been used to investigate the dependence of thruster behavior on the applied voltage, gas flow rate, magnetic field, channel geometry and wall material. The studies conducted so far have demonstrated a significant effect of channel material on thruster electrical characteristics and the existence of an optimal channel length for a given flow rate. Representative results highlighting these findings are presented.

Development and investigation of a standard fluid mechanical flow rate meter

An automated fluid mechanical flow rate meter which provides for measuring gas flow rates in vacuum over the range from 10 −5 to 1 m 3Pa/s is described. The time it takes for the measurement to be carried out is not more than 5–15 min. A meter equation was derived, and constructional and operational features of the device were evaluated. The influence of additional processes and temperature variations on the meter readings was analyzed. The results of metrological investigations of the apparatus and the measured data concerning its practical use are presented.

Measurement of small gas flow rate by the conductance modulation method

Conductance modulation (CM) method has been applied to the measurement of small gas flow rate. We have realized the dynamic balancing of gases to simulate the condition of ultimate pressure in ultra-high-vacuum (UHV) and extremely-high-vacuum (XHV). In this condition, we have examined the ability, the accuracy and the detection limit for the measurement by CM method. It has been revealed from the experiments that the method has basic characteristics to measure accurately small gas flow rate in different vacuum conditions. An error of less than 20% is expected when Sig. N × S ∗ C > 1 and the lowest detection limit of the order of 10 −13Pa m 3s −1 is expected when C≒S ∗≒S, where Sig. N : signal-to-noise ratio, S∗: net pumping speed, C: conductance and S: intrinsic pumping speed.

Instantaneous Flow Rate Measurement of Ideal Gases

In this paper, a chamber called an “Isothermal Chamber” was developed. The isothermal chamber can almost realize isothermal condition due to larger heat transfer area and heat transfer coefficient by stuffing steel wool in it. Using this chamber, a simple method to measure flow rates of ideal gases was developed. As the process during charge or discharge is almost isothermal, instantaneous flow rates charged into or discharged from the chamber can be obtained measuring only pressure in the chamber. The steady and the unsteady flow rate of air were measured by the proposed method, and the effectiveness of the method was demonstrated. [S0022-0434(00)00301-4]

Wear-resistant orifices for measurement of liquid and gas flow rates

Wear-resistant orifices for measurement of liquid and gas flow rates

Quickly changeable device for gas and liquid flow rate measurement

Quickly changeable device for gas and liquid flow rate measurement

Gas flowrate measurements for leak calibration

Results concerning the calibration of metal capillary tubes of the linear and crimped types with different inert testing gases from 3 × 10 −8 Pa m 3 s −1 to 3 × 10 −5 Pa m 3 s −1 (1 × 10 −11 mol s −1 − 1 × 10 −8 mol s −1) are presented. A primary flowmeter connected to a dynamic expansion system is used as a reference. With gas flow rates above 5 × 10 −7 Pa m 3 s −1 (2 × 10 −10 mol s −1), direct comparisons are made, whereas for flow rates below that value the reduction method is applied. The unknown gas flow rates and those from the flowmeter are compared by means of a quadrupole mass spectrometer. These capillaries, after appropriate calibration, can be used as secondary reference leaks in the stated range with total uncertainty between 1.3 × 10 −2 and 9 × 10 −3 and the final object of this work is to provide a leak calibration service to users.

Optimal Feeding Distribution for Large Scale Aeration Basin

The pollution control problem is formulated for the large-scale wastewater treatment system with distributed water feeding in the aeration basin. It is formulated as the organic matter distribution control problem along the basin and solved by approximation of the original problem using finite-dimensional and by separation of the estimation and control problems. The feedback control is obtained in a relatively simple form as an explicit function of previous measurements such as the dissolved oxygen concentration, outlet gas flow rate and composition measurements. The control law is tested in the simulation experiment. An improvement of the treated water quality is demonstrated in the case of feeding distribution control.

A method of measurement of gas flow rates in ECR and PIG ion sources

A method of measurement of an instantaneous value of the volume flow rate (in the range 0.05–5 cm3 min−1)of a gas flowing into an ion chamber of an ion source is described. It consists of the measurement of pressure differences (0–100 Pa) on a system of diaphragms with a small hole (0.2 mm) made in the center of them. The pressure differences are generated by the flowing of the gas through the latter. The sensitivity of the system depends on the number of diaphragms used. Parameters of diaphragms are estimated by the special equation describing the flow of the gas through an orifice in a pipe and the equation for laminar flow in a round tube. Calibrating measurements with He, air, Ar, and Xe demonstrated that our diaphragm can be used for the measurement of flow rates of all these gases.

The future domestic gas meter: Review of current developments

This paper illustrates the gas flow rate measurement techniques that can be introduced in future domestic applications. First, the role of the gas meter in legal metrology is introduced. Then, the “intelligent” (or “smart”) gas meter is analyzed, since it should be used in the near future. Such a meter is an improvement of the current domestic diaphragm gas meter, also equipped with electronic components, so as to obtain a more flexible instrument and a more convenient measurement data processing (temperature compensation, remote reading, etc.). After that, static gas meters are analyzed. Such meters have no moving parts. Of this category, only ultrasonic and fluidic oscillator meters are reviewed here. At present they are in an advanced phase of experimentation for custody transfer gas metering. Thanks to their design, which does not include any moving parts, these meters may represent in the future the best solution to measure the consumption of natural gas for domestic use. This paper discusses the operating principles and metrological characteristics of the static meters mentioned above, and provides some experimental results regarding domestic gas measurement. Finally, their possible evolution and application on the international scene are briefly outlined.

Use of on-line gas analysis to monitor recombinant mammalian cell cultures.

The development of a system capable of accurately measuring the oxygen uptake and carbon dioxide production rates during mammalian cell cultures is described. A detailed study of the specifications of the various components used in the system for the measurement of gas flow rates and composition, coupled with the validation of the system independent of the bioreactor was carried out. The aim of this study was to identify and eliminate where possible the errors controlling the accuracy of determination of gaseous metabolic rates. This study showed the importance of controlling the temperature of gaseous oxygen entering the system. With such temperature control, it was possible to obtain data with an accuracy of +/- 5% at the 95% confidence level. Another source of error, the use of bi-carbonate buffer, was studied. A mathematical model was used to compensate for the affect of such buffers on the determination of carbon dioxide production rates. The use of the system for the continuous determination of gaseous metabolism during the growth and production phase for recombinant CHO cell cultures is described.

An Electronic Minipermeameter for Use in the Field and Laboratory

AbstractThe quantification of permeability and geostatistical scaling from laboratory to well field to regional systems requires large spatial data sets for which field and laboratory minipermeameters have proven to be effective tools. We developed an electronic gas minipermeameter for use in either the field or the laboratory. This design alleviates several problems common to minipermeameters. In particular, errors in measurement of gas flow rate, calibration of flow rate meters, and countering pressure and temperature effects were reduced by using electronic mass‐flow transducers. Problems of sealing the injector (probe) tips and of measuring the permeability of weathering rinds and fracture “skins” were remedied with a sample chamber capable of handling thin wafers or rock cores of arbitrary dimensions. Calibrations with samples of known permeability were excellent. It is now possible to measure permeability very accurately on weathering rinds, fracture surfaces, utcrops, and large hand samples.

地震に伴う温泉ガスの挙動

Mineral spring gas compositions at several sites in central Japan have been continuously monitored by our laboratory for the earthquake prediction study. In connection with it, a new system for the measurement of mineral spring gas flow rate has been installed at Byakko mineral spring, Miaunami, Gifu Prefecture, a momitoring site. The continuous observation with this system has been conducted since January, 1993. The main body of the gas flow rate meter is a vertically submerged plastic pipe of 4.1cm in diameter attached by pressure transducer. The mineral spring gases issuing from the bottom of the spring pool are collected into the pipe, the upper end of which is closed by an electric valve. As the sample gas is accumulated, the water level in the pipe becomes lower and the inner gas pressure becomes higher. After a fixed period, the inner pressure is measured with the pressure transducer and subsequently the accumulated gas is librated by opening the valve and thus the operation proceeds repeatedly for the continuous monitoring. The gas flow rate is calculated from the measured pressure. These operations including gas analyses are controlled by two personal computers. The obtained data are sent to our laboratory through the public communication line. Although observed gas flow rates considerably fluctuate, the flow rate on moving averages is positively correlated with He/Ar ratio in the gas. Thirteen earthquakes felt around the monitoring site occurred during this one year, and, at the events of the largest three seismic intensity, coseismic anomalies emerged in the gas flow rate. The feature described above suggests that the coseismic anormalies in the rate are caused by the bubbling at the earthquake tremor. On the other hand, it seems that the coseismic change of He/Ar ratio is not always caused by the bubbling. Although the cause of this change still remains unsolved, it is likely that the behavior of He/Ar ratio is controlled by the changes of the compressive stress in the crust.