Gas Pressure Measurement Research Articles

Total Dissolved Gas Pressure Measurements for Assessing Contaminant Degradation Processes in Groundwater

AbstractThe total dissolved gas pressure (PTDG ) probe has been used in groundwater studies for over a decade, but rarely in assessing contaminant degradation, despite the many degradation reactions that produce or consume dissolved gases. Here we present three studies to demonstrate the application of PTDG measurements to groundwater experiencing contaminant degradation, with discussion of its benefits and limitations. The first study is a pilot‐scale laboratory experiment simulating dissolved ethanol contamination of an anaerobic sand aquifer. Continuous monitoring of PTDG showed the rapid onset of microbial hydrocarbon degradation via denitrification and fermentation. The subsequent formation of a gas phase was revealed when PTDG began mimicking the bubbling pressure (PG *; sum of hydrostatic and atmospheric pressure), fluctuating with atmospheric pressure. Some deviations of PTDG above PG * occurred also, which may hold promise for signalling substantial changes in the rate or type of degradation process (here, the onset of methanogenesis). In the second study, synoptic field measurements at a petroleum plume site demonstrated how elevated PTDG could identify wells with evidence of hydrocarbon degradation (denitrification and/or methanogenesis). And finally, combined field measurements of dissolved oxygen (DO) and PTDG in monitoring wells of a nitrate‐contaminated aquifer (Abbottsford‐Sumas) revealed areas where denitrification was likely occurring. Limitations to PTDG use identified in these studies included the masking of degradation processes by the presence of a gas phase, as when trapped following water table fluctuations or formed from rigorous degradation reactions, and confounded assessment of PTDG patterns from other natural or anthropogenic processes that can also influence groundwater PTDG .

Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

Neutron resonance absorption imaging is a non-destructive technique that can characterize the elemental composition of a sample by measuring nuclear resonances in the spectrum of a transmitted beam. Recent developments in pixelated time-of-flight imaging detectors coupled with pulsed neutron sources pose new opportunities for energy-resolved imaging. In this paper we demonstrate non-contact measurements of the partial pressure of xenon and krypton gases encapsulated in a steel pipe while simultaneously passing the neutron beam through high-Z materials. The configuration was chosen as a proof of principle demonstration of the potential to make non-destructive measurement of gas composition in nuclear fuel rods. The pressure measured from neutron transmission spectra (∼739 ± 98 kPa and ∼751 ± 154 kPa for two Xe resonances) is in relatively good agreement with the pressure value of ∼758 ± 21 kPa measured by a pressure gauge. This type of imaging has been performed previously for solids with a spatial resolution of ∼ 100 μm. In the present study it is demonstrated that the high penetration capability of epithermal neutrons enables quantitative mapping of gases encapsulate within high-Z materials such as steel, tungsten, urania and others. This technique may be beneficial for the non-destructive testing of bulk composition of objects (such as spent nuclear fuel assemblies and others) containing various elements opaque to other more conventional imaging techniques. The ability to image the gaseous substances concealed within solid materials also allows non-destructive leak testing of various containers and ultimately measurement of gas partial pressures with sub-mm spatial resolution.

Status of the development of diagnostic pressure gauges for the operation in ITER

The ITER Diagnostic Pressure Gauges (DPG) shall provide the measurement of the neutral gas pressure, which is an important parameter for basic control of the operation of the ITER machine as well as for input to physics models of the plasma boundary. The reference sensor is a hot cathode ionization gauge, which is able to operate in an environment with strong magnetic fields (up to 8T), strong and noisy background signals and fast pressure changes. In total 52 DPG sensor heads will be installed in 4 lower ports, 4 divertor cassettes and 2 equatorial ports. The DPG system is currently being developed by IPP in collaboration with F4E and Sgenia within the Framework Partnership Agreement FPA-364. As part of the system level design activities several different architectures of the DPG system, including gauge head and supporting electronic equipment, have been evaluated in detail with the aim to fulfil technical requirements imposed by the integration in ITER. Most important steps made towards the currently defined baseline design of the DPG system, which is based on ASDEX Pressure Gauge (APG) technology, are discussed in the present paper.

Pressure prediction model based on artificial neural network optimized by genetic algorithm and its application in quasi-static calibration of piezoelectric high-pressure sensor.

This paper applies back propagation neural network (BPNN) optimized by genetic algorithm (GA) for the prediction of pressure generated by a drop-weight device and the quasi-static calibration of piezoelectric high-pressure sensors for the measurement of propellant powder gas pressure. The method can effectively overcome the slow convergence and local minimum problems of BPNN. Based on test data of quasi-static comparison calibration method, a mathematical model between each parameter of drop-weight device and peak pressure and pulse width was established, through which the practical quasi-static calibration without continuously using expensive reference sensors could be realized. Compared with multiple linear regression method, the GA-BPNN model has higher prediction accuracy and stability. The percentages of prediction error of peak pressure and pulse width are less than 0.7% and 0.3%, respectively.

Antiresonant reflecting guidance mechanism in hollow-core fiber for gas pressure sensing.

A gas pressure sensor based on an antiresonant reflecting guidance mechanism in a hollow-core fiber (HCF) with an open microchannel is experimentally demonstrated for gas pressure sensing. The microchannel was created on the ring cladding of the HCF by femtosecond laser drilling to provide an air-core pressure equivalent to the external environment. The HCF cladding functions as an antiresonant reflecting waveguide, which induces sharp periodic lossy dips in the transmission spectrum. The proposed sensor exhibits a high pressure sensitivity of 3.592 nm/MPa and a low temperature cross-sensitivity of 7.5 kPa/°C. Theoretical analysis indicates that the observed high gas pressure sensitivity originates from the pressure induced refractive index change of the air in the hollow-core. The good operation durability and fabrication simplicity make the device an attractive candidate for reliable and highly sensitive gas pressure measurement in harsh environments.

Measurement of neutral gas pressure in the D-module of GAMMA 10/PDX by using ASDEX type fast ionization gauge.

In the divertor simulation experiments in the GAMMA 10/PDX tandem mirror, pressure of the neutral gas was investigated by using a fast ionization gauge. The gauge was absolutely calibrated for hydrogen gas by using a capacitance manometer. Change of the gauge sensitivity due to the magnetic field of GAMMA 10/PDX was also evaluated. The typical gas pressure measured in detached plasma experiments was 0.1-10 Pa. The degree of plasma detachment determined from the reduction of heat flux was enhanced as the gas pressure increases. Rapid increase of the gas pressure under the plasma flow was also observed.

Fiber Fabry–Pérot Interferometer for Measurement of Gas Pressure and Temperature

A fiber Fabry–Perot interferometer (FPI) is proposed and demonstrated for the measurement of gas pressure and temperature. The interferometer is fabricated by fusion splicing a short segment of capillary tube to a standard single mode fiber (SMF), followed by inserting a glass microsphere into the tube, the air gap between the SMF end face and the glass microsphere then forms a fiber FPI. Due to the additional reflection occurred on the rear surfaces of the microsphere, the reflection spectrum of the device is a three-beam interference pattern. Owing to the dependence of refractive index of gas on the pressure applied and the thermal-optical effect of glass microsphere, different dips in the interference fringe pattern exhibit different responses to the changes in gas pressure and temperature, which enables a simultaneous gas pressure and temperature sensing. The proposed device has the advantages of compact size, robust structure, easy fabrication, high gas pressure sensitivity, and supporting of range tunable operation.

Pressure pulse-decay tests in a dual-continuum medium: Late-time behavior

The pressure pulse-decay test has been one of the most widely used techniques to measure permeability for low-permeability rocks including shale, largely because relatively simple analytical solutions to fluid flow in a rock sample (characterized as a single continuum) exist for analyzing late-time test data. This work develops a new analytical solution for analyzing late-time pulse-decay test data for dual-continuum rock samples, motivated by the possibility that shale matrix (not including fractures) may exhibit dual- or multiple-continuum gas-flow behavior owing to its wide spread pore size distributions and property differences between organic and inorganic components of the shale matrix. This issue has important implications for characterizing and modeling gas flow in shale, because a dual-continuum medium involves more flow parameters and requires more complex modeling approaches than a single-continuum medium. Our new analytical solution shows that the relationship between gas pressure measurements from a pulse-decay test and permeability remains the same for both single- and dual-continuum systems, suggesting that shale-matrix permeability data in the literature, previously obtained from pulse-decay tests, are valid although the corresponding shale samples ought to be treated as dual-continuum instead of a single continuum system. In addition, our analytical solution relates mass transfer (between the two continua) to pressure change during late-time of a test. This relationship, with a clear and intuitive physical interpretation rooted in the mass balance principle, provides a simple and practical analysis technique to identify dual-continuum behavior from pulse-decay test data and to estimate mass transfer coefficient between the two continua if the dual-continuum behavior exists. The usefulness of the analytical solution is demonstrated by satisfactory matches with several pulse-decay test data sets. The data analysis results also indicate that not all shale samples exhibit dual-continuum gas-flow behavior regardless of their make-up and complex pore structures.

Collision Cross Sections for 20 Protonated Amino Acids: Fourier Transform Ion Cyclotron Resonance and Ion Mobility Results.

We report relative dephasing cross sections for the 20 biogenic protonated amino acids measured using the cross sectional areas by Fourier transform ion cyclotron resonance (CRAFTI) technique at 1.9 keV in the laboratory reference frame, as well as momentum transfer cross sections for the same ions computed from Boltzmann-weighted structures determined using molecular mechanics. Cross sections generally increase with increasing molecular weight. Cross sections for aliphatic and aromatic protonated amino acids are larger than the average trend, suggesting these side chains do not fold efficiently. Sulfur-containing protonated amino acids have smaller than average cross sections, reflecting the mass of the S atom. Protonated amino acids that can internally hydrogen-bond have smaller than average cross sections, reflecting more extensive folding. The CRAFTI measurements correlate well with results from drift ion mobility (IMS) and traveling wave ion mobility (TWIMS) spectrometric measurements; CRAFTI results correlate with IMS values approximately as well as IMS and TWIMS values from independent measurements correlate with each other. Both CRAFTI and IMS results correlate well with the computed momentum transfer cross sections, suggesting both techniques provide accurate molecular structural information. Absolute values obtained using the various methods differ significantly; in the case of CRAFTI, this may be due to errors in measurements of collision gas pressure, measurement of excitation voltage, and/or dependence of cross sections on kinetic energy. Graphical Abstract ᅟ.

Combining Electrical and Pressure Measurements for Early Flooding Detection in a PEM Fuel Cell

Water flooding is one of the main causes of performance degradation for polymer electrolyte membrane fuel cells (FCs), and its prompt detection is therefore important to guarantee optimal FC operation. This paper aims at comparing the most common methods for flooding diagnosis, which are based on electrical or gas pressure measurements. Their differences in terms of sensitivity to flooding are investigated, primarily focusing on their suitability for its early detection. In particular, the differences between anodic and cathodic pressure drop measurements are highlighted, as well as their relationship with the FC electrical output. The experimental results show that cathodic pressure measurements are the most convenient choice for early flooding detection. Measurements have been performed on a single cell, since it allows an easier interpretation of the results, although the applicability of the considered methods to FC stacks for commercial applications is also discussed.

System for gas pressure measurements in the arc plasma environment

Developed measurements system for evaluation of gas pressure value in direct vicinity of switching arc plasma was described in this paper. The system is resistant to heavy duty conditions present inside the MV switch quenching chamber and its functionality was verified during large scale functional tests. In this paper results of gas pressure measurements performed for a current interrupter equipped with an arc quenching system based on combination of forced air flow and gassing material ablation were presented. Gas pressure was measured by means of developed system, for several values of capacitive load current at 12/24kV supplying voltage.

Evaluating pre-split performance through direct measurements of near field acceleration, particle velocity and gas pressure

Pre-split techniques are routinely used to minimise rock mass damage from production blasting. Design parameters rely on site-specific guidelines and in order to improve designs, it is important to be able to measure its performance. One criterion is related to the pre-split ability to adequately filter blast-induced stresses and explosion gases. This paper presents the results of a monitoring program implemented to evaluate the performance of pre-split practices. Triaxial accelerometers and pressure sensors were installed behind pre-split lines and a site-specific criterion was established to determine whether or not filtering effects were occurring. The recorded maximum peak particle velocity (PPV) vector sum behind pre-splits in all blasts monitored was below the threshold of damage of intact rock and rock mass discontinuities. With regards to the recorded gas pressure, measurements from production blasts showed fluctuations of low pressure levels, indicating that pre-split parameters were effectively filtering-induced stresses and gases.

Recovery of Absolute Absorption Line Shapes in Tunable Diode Laser Spectroscopy Using External Amplitude Modulation With Balanced Detection

Accurate recovery of an absorption lineshape is important in many industrial applications for simultaneous measurement of gas concentration and pressure or temperature. Here, we demonstrate a method, based on a modification to the Hobbs balanced receiver circuit, for background signal nulling when external amplitude modulation of the laser output is used. Compared with direct or non-nulled detection techniques, we demonstrate that the method significantly improves the signal-to-noise ratio to a level comparable with that of the conventional second harmonic wavelength modulation spectroscopy. Most importantly, normalisation and recovery of the lineshape is straightforward and immune to the difficulties that afflict lineshape recovery with the conventional wavelength modulation spectroscopy.

Fiber-coupled diode-laser sensors for calibration-free stand-off measurements of gas temperature, pressure, and composition.

A fiber-coupled near-infrared diode-laser sensor for stand-off measurements of gas temperature, pressure, and composition is presented. This sensor utilizes a fiber bundle with six multimode catch fibers surrounding one single-mode pitch fiber to transmit and receive backscattered laser light in a handheld transmitter/receiver. Scanned-wavelength-modulation spectroscopy with 1f-normalized 2f-detection and fast (80-200 kHz) wavelength modulation were used to provide calibration-free measurements and reduce the influence of spurious cavity noise formed by the overlapping transmitted and reflected laser light. Demonstrations include two-color measurements of temperature, pressure, and H(2)O near 1.4 μm in a propane flame at 2 kHz (SNR=200) and measurements of CH(4) near 1.65 μm (SNR=20 to 1500) at stand-off distances of 15 cm and 10 m, respectively. The fraction of photons collected ranged from 10(4) to 1 parts per million at stand-off distances from 10 cm to 10 m, respectively, and is similar for aluminum and paper reflectors.

FBG Incorporated Side-open Fabry-Perot Cavity for Simultaneous Gas Pressure and Temperature Measurements

A dual-parameter sensing structure based on a fiber Bragg grating (FBG) incorporated side-open Fabry-Perot cavity (FPC) is proposed and experimentally demonstrated for simultaneous measurements of gas pressure and temperature. The side-open FPC consisted of a micro-piece of chemical etched side-hole fiber acts as a pressure sensing unit. Two samples with different cavity lengths of 60 μm and 100 μm were fabricated and tested for gas pressure and temperature sensing in the experiment. Linear gas pressure responses of 4.063 pm/kPa and 4.071 pm/kPa in a large measuring range of 0-1000 kPa were obtained, respectively, which agree well with the theoretical analysis. Meanwhile, the temperature cross-sensitivities were measured as 214 Pa/° and 204 Pa/°. As a local temperature monitor, the incorporation of a short FBG in the leading single mode fiber was used to compensate the temperature cross-sensitivity of the sensor. This kind of compact and highly sensitive fiber sensor is appropriate for simultaneous gas pressure and temperature sensing in harsh micro environment.

Determination of the VT-relaxation time of molecules from the compression pulse width of a photoacoustic signal: the effect of gas pressure measurement errors

Determination of the VT-relaxation time of molecules from the compression pulse width of a photoacoustic signal: the effect of gas pressure measurement errors

Gas Evolution in Operating Lithium-Ion Batteries Studied In Situ by Neutron Imaging.

Gas generation as a result of electrolyte decomposition is one of the major issues of high-performance rechargeable batteries. Here, we report the direct observation of gassing in operating lithium-ion batteries using neutron imaging. This technique can be used to obtain qualitative as well as quantitative information by applying a new analysis approach. Special emphasis is placed on high voltage LiNi0.5Mn1.5O4/graphite pouch cells. Continuous gassing due to oxidation and reduction of electrolyte solvents is observed. To separate gas evolution reactions occurring on the anode from those associated with the cathode interface and to gain more insight into the gassing behavior of LiNi0.5Mn1.5O4/graphite cells, neutron experiments were also conducted systematically on other cathode/anode combinations, including LiFePO4/graphite, LiNi0.5Mn1.5O4/Li4Ti5O12 and LiFePO4/Li4Ti5O12. In addition, the data were supported by gas pressure measurements. The results suggest that metal dissolution in the electrolyte and decomposition products resulting from the high potentials adversely affect the gas generation, particularly in the first charge cycle (i.e., during graphite solid-electrolyte interface layer formation).

Fiber-tip gas pressure sensor based on dual capillaries.

A micro-cavity fiber Fabry-Perot interferometer based on dual capillaries is proposed and demonstrated for gas pressure measurement. Such a device is fabricated by fusion splicing of a tiny segment of a main-capillary with a feeding-capillary on one end, and a single mode fiber on the other, to allow gas enters the main-capillary via the feeding-capillary. The reflection spectrum of the interferometer device shifts with the variation of gas pressure due to the dependence of gas refractive index on the pressure applied. During the device fabrication process, a core-offset fusion splicing method is adopted, which turns out to be highly effective for reducing the detection limit of the sensor. The experimental results obtained show that the proposed device exhibits a high gas pressure sensitivity of 4147 pm/MPa, a low temperature cross-sensitivity of less than 0.3 KPa/°C at atmospheric pressure, and an excellently low detection limit down to ~4.81 KPa. The robust tip structure, ultra-compact device size and ease of fabrication make the device an attractive candidate for reliable and highly sensitive gas pressure measurement in a precise location.

The influence of experimental uncertainties in the measured gas pressures and wavenumber scale calibration on multispectrum fitting results

The paper considers the artificial corrections of measured gas pressures and wavenumber scale shifts for multispectrum fit by the example of R(22) carbon dioxide self-broadened line of 30013←00001 vibrational band. For this purpose the two quadratic and hypergeometric speed-dependent Voigt line profile models including line mixing within the (Rosenkranz) first-order approximation for line-coupling effects with linear dependences of corresponding model parameters on pressure were applied. The intercomparison of the retrieved results only for pressure corrections, only for wavenumber scale shifts, for both together, and for no correction case demonstrates considerable disagreement between them. The most significant differences in parameters, retrieved in such a way, belong to the first-order line-mixing coefficients and are caused mostly by the shift scattering of wavenumber scale at different pressures.

Infrared planar laser-induced fluorescence with a CW quantum-cascade laser for spatially resolved CO2 and gas properties

The design and demonstration of a new infrared laser-induced fluorescence (IR-LIF) technique that enables spatially resolved measurements of CO2, temperature, and pressure, with potential for velocity, are presented. A continuous-wave, wavelength-tunable, quantum-cascade laser (QCL) near $$4.3\,\upmu \hbox {m}$$ with up to 120 mW was used to directly excite the asymmetric-stretch fundamental-vibration band of CO2 for approximately 200 to $$10^5$$ times more absorbance compared with previous IR-LIF techniques. This enabled LIF detection limits (signal-to-noise ratio of 1) of 20 and 70 ppm of CO2 in Ar and $$\hbox {N}_2$$ , respectively, at 1 bar and 296 K in static-cell experiments. Simplified and detailed kinetic models for simulating the LIF signal as a function of gas properties are presented and enable quantitative, calibration-free, IR-LIF measurements of CO2 mole fraction within 1–8 % of known values at 0.5–1 bar. By scanning the laser across two absorption transitions and performing a multi-line Voigt fit to the LIF signal, measurements of temperature, pressure, and $$\chi _{\hbox {CO}_2}$$ within 2 % of known values were obtained. LIF measurements of gas pressure at a repetition rate up to 200 Hz (in argon) are also presented. Planar-LIF (PLIF) was used to image steady and unsteady CO2–Ar jets at 330 frames per second with a spatial signal-to-noise ratio (SNR) up to 25, corresponding to a detection limit (SNR = 1) of 200 ppm with a projected pixel size of $$40\,\upmu \hbox {m}$$ . The gas pressure was measured within $$3 \pm 2$$ % of the known value (1 bar) at 5 Hz by scanning the QCL across the P(42) absorption transition and least-squares fitting a Voigt profile to the PLIF signal. Spatially resolved measurements of absolute CO2 mole fraction in a laminar jet are also presented.