Gas Pressure Measurement Research Articles

Nimh Gas Model for Dynamic Behaviour Study

The NiMH battery is an intercalation battery with a positive NiOH electrode and a negative metal hydride electrode. The electrolyte used is a highly alkaline aqueous solution, typically 6:1 KOH:LiOH. As a consequence of this and the reaction potentials of the electrodes, splitting of water into its constituting elements is a part of normal battery operation. When charging at high SOC, as well as when overcharging, oxygen is formed as a side-reaction. It then diffuses through the separator and recombines at the negative electrode. This recombination cycle causes the temperature in the battery to rise, something that is commonly used to terminate battery charging, either through ΔT or -ΔV criteria. In addition to oxygen production at high state of charge, overdischarging of the battery can produce hydrogen at the positive electrode, with a pressure increase at end of discharge indicating a harmful overdischarge of the battery [1]. Hydrogen is also present in the battery gas composition as a consequence of the negative hydrogen intercalation electrode material which is in equilibrium with gaseous hydrogen, an equilibrium which shifts with electrode hydrogen content [2]. Figure Left: A schematic showing the main gas reactions in the metal NiMH battery. Right: An example cycle of a NiMH battery, showing cell voltage (blue), cell gas pressure (green) and cell surface temperature (teal).The internal gas reactions of the NiMH battery have a great impact on battery function, both in regard to energy efficiency and battery aging. While measurements of battery internal total gas pressure occur in some battery systems, measurements of individual constituents would be impractical in the field, as such measurements require laboratory equipment. Therefore, a gas model that can estimate the internal pressure distribution under dynamic conditions would be a valuable tool to study the effects of different application drive cycles, as well as a possibility to further enhance BMS function for battery stability and longevity.There have been many attempts at modeling the gaseous side reactions in the NiMH battery. Some of these models are part of comprehensive battery models, which combines a voltage response model with added side reactions [3,4]. Other models look only at specific gas related processes [5]. However, a limitation with these models is that they are not able to model the battery during dynamic current conditions. The main reason for this is the presence of a strong open circuit voltage hysteresis, something that these models do not capture well.This study presents a model of the gas reactions and heat generation in the NiMH battery. The model is not coupled to a voltage model, instead it simulates internal temperature and pressure when supplied with experimental current, voltage and surface temperature data. This removes the complication of the open circuit voltage hysteresis effect and lets us model dynamic battery behavior. The model is in zero dimensions and based on physical principles. There are several parameters that are optimized by fitting to experimental data. The model is then validated by simulating pressure for a second set of data, based on the fitted values of the parameters. The simplicity of the model not only allows for it to be used in battery monitoring hardware, it can also be coupled to voltage and multidimensional models to build a more comprehensive predictive model.References Notten, P. H. L.; Latroche, M. Nickel-Metal Hydride: Metal Hydrides. In Encyclopedia of Electrochemical Power Sources; Garche, J., Dyer, C., Moseley, P., Ogumi, Z., Rand, D., Scrosati, B., Eds.; Elsevier B.V., 2009; Vol. 50, pp 502–521.Tserolas, V.; Katagiri, M.; Onodera, H.; Ogawa, H. Thermodynamical Modeling of P-C Isotherms for Metal Hydride Materials. Trans. Mater. Res. Soc. Japan 2010, 35 (2), 221–226. https://doi.org/10.14723/tmrsj.35.221.Albertus, P.; Christensen, J.; Newman, J. Modeling Side Reactions and Nonisothermal Effects in Nickel Metal-Hydride Batteries. J. Electrochem. Soc. 2008, 155 (1), A48. https://doi.org/10.1149/1.2801381.Ledovskikh, A.; Verbitskiy, E.; Ayeb, A.; Notten, P. H. L. Modelling of Rechargeable NiMH Batteries. J. Alloys Compd. 2003, 356–357, 742–745. https://doi.org/10.1016/S0925-8388(03)00082-3.Notten, P. H. L.; Ouwerkerk, M.; Ledovskikh, A.; Senoh, H.; Iwakura, C. Hydride-Forming Electrode Materials Seen from a Kinetic Perspective. J. Alloys Compd. 2003, 356–357, 759–763. https://doi.org/10.1016/S0925-8388(03)00085-9. Figure 1

High sensitivity gas pressure sensor based on two parallel-connected Fabry–Perot interferometers and Vernier effect

In this study, a highly sensitive gas pressure sensor based on two Fabry–Perot interferometers (FPIs) in parallel with the Vernier effect is designed and demonstrated. In the sensor, FPI1 and FPI2 were used as the detection and reference units, respectively. FPI1 and FPI2 have similar structures, both comprising a single-mode fiber and capillary splicing. However, the microaperture is processed on the capillary of the FPI1 with a femtosecond laser, enabling the external gas to enter the FPI1 cavity through the microaperture channel to realize the gas pressure measurement. The Vernier effect is achieved by superimposing the reflective spectra of FPI1 and FPI2, which have a small cavity length. The gas pressure response, repeatability, and stability of the sensor structures were investigated. The sensitivity of the sensor was improved owing to the Vernier effect. Experimental results indicate that the sensor sensitivity is up to 47.76 nm MPa−1, which is 11.9 times that of a single FPI1 sensor without the Vernier effect. The measured temperature cross-sensitivity of the sensor is approximately 5.1 kPa/ °C. In addition, the sensor has the advantages of simple manufacturing, robust structure, and stable operation. Finally, the manufacturing method of FPI and the parallel connection mode of FPIs could also be used in other sensing fields, providing an alternative design scheme for high-sensitivity sensors.

Measurement of gas pressure in packaged electric double layer capacitors

Electric double layer capacitors (EDLCs) are popular energy storage devices in part because they have very long life with a highly predictable failure time. EDLCs generate gas during operation, particularly when operated at their maximum rated temperature and voltage, which leads to pressure rise in a sealed package with the possibility of package rupture. However, EDLC package rupture is seldom observed because it can be prevented with proper application engineering, which requires knowledge of the gas generation rate. We demonstrate two approaches for the measurement of gas pressure in packaged EDLCs. The first is indirect and relies on package deformation to infer the internal gas pressure. This is easy to implement and has low cost but it lacks high precision. The second approach measures gas pressure directly using an electronic transducer. It is more cumbersome and costly (a special apparatus is needed) but does provide continuous measurement with high precision. Details of both gas pressure measurement approaches are reported and demonstrated using packaged 100-F-size EDLCs. • Gas pressure was measured in packaged electric double layer capacitors two ways. • Gas generation began when voltage was first applied to the capacitor. • The indirect measurement approach was fast and low cost but it lacked precision. • The direct measurement approach had high precision but was more cumbersome.

Modeling for gas dissolution and diffusion in water-intrusion coal seam and its potential applications

In order to determine the gas pressure for water-intrusion borehole, a new method of gas pressure measurement in water-intrusion borehole based on gas solubility was proposed. A mathematical model of gas migration in water-intrusion borehole considering the effective diffusion coefficient was established. The influencing factors, such as water-intrusion radius, diffusion coefficient and solution convection, on the dissolution equilibrium of gas in borehole water were investigated. Finally, the feasibility of the new gas pressure measurement method was discussed. Results showed that the gas diffusion coefficient and water-intrusion radius of coal seam are the key factors influencing the equilibrium duration of gas dissolution. During the accumulation stage of formation water in borehole, the gas is able to quickly dissolve and diffuse in borehole water. The amount of dissolved gas can reach more than 90% of solubility in three days. After the formation water enters the coal seam, the equilibrium time grows sharply because the effective diffusion coefficient of gas in water-saturated coal is much lower than that in pure water. In addition, the water convection causes a higher amount of gas dissolved at the borehole bottom. Finally, the field applicability for the new method of pressure measurement were analyzed by combining the data from previous works. This work provided a new idea for the gas pressure measurement of water-intrusion borehole.

Hollow Core Bragg Fiber Integrated With Regenerate Fiber Bragg Grating for Simultaneous High Temperature and gas Pressure Sensing

We have proposed and experimentally demonstrated a novel optical fiber sensor for simultaneous measurement of high temperature and gas pressure based on a Regenerated Fiber Bragg grating (RFBG) cascaded with a homemade hollow core Bragg fiber (HCBF). The HCBF functions as an anti-resonant reflecting waveguide and acts as a pressure and temperature sensing unit. The sample was fabricated and tested in our lab, exhibiting a high linear pressure and temperature sensitivity of −3.747 nm/MPa and 25.925 pm/°C in a large-dynamic range of 2 MPa and 600 °C, respectively. The RFBG, as a temperature monitor, was integrated to compensate the temperature cross-correspondence of the HCBF. By utilizing a 2 × 2 matrix obtained with the experimental results, simultaneous measurement of temperature and gas pressure can be achieved. Besides, compact size, low cost and high sensitivity make the sensor more competitive in harsh environment application.

Study and application of a new gas pressure inversion model in coal seam while drilling based on directional drilling technology

China is one of the countries most seriously affected by coal and gas outburst disasters. Gas pressure is an important parameter to evaluate the risk of coal and gas outburst. In order to solve the problem existing in the traditional gas pressure measurement method, a dynamic inversion model of gas pressure while drilling is established based on the gas emission rule of coal particle and the gas radial migration equation of borehole wall in this paper. Combined with the directional drilling system and the special gas emission measuring device, the dynamic inversion model is applied to measure the gas pressure in the coal seam. The results show that: (1) The theoretical value of gas pressure obtained from the new model has a small error range by comparing with the actual value of gas pressure, which indicates that the new model has good reliability and applicability; (2) The distribution range of gas pressure value is wide, which shows the non-uniformity of gas occurrence in coal seam. The heterogeneity of gas pressure value shows an approximate normal distribution law in statistics; (3) Influenced by the occurrence of original gas in coal seam, the evolution law of outburst elimination in each area of coal seam also presents the characteristics of non-uniformity. The research results have important practical significance to assist the early warning of coal and gas outburst and to achieve coal and gas co-mining with safety mining.

Cascaded fiber MZIs for simultaneous measurement of pressure and temperature

A hybrid cascade structure composed of two Mach–Zehnder interferometers (MZI) is proposed and demonstrated to measure gas pressure and temperature, simultaneously. The key sensing components of the two MZIs are all based on a tapered single mode fiber (TSMF) spliced between two multimode optical fibers. The difference is that one of the TSMFs is covered with PDMS material, while the other one is exposed to air. Because of the large changes in the refractive index versus air pressure and the high thermo-optic coefficient of PDMS, the MZI covered with PDMS has a high sensitivity to gas pressure and temperature. While the MZI exposed to air has only high gas pressure sensitivity because the air is directly involved in the sensing as a signal of interferometer and the effective refractive index of air varies with the pressure. Experimental results show that the gas pressure and temperature sensitivities of the MZI filled with PDMS can be as high as 78.553 nm/MPa and 8.455 nm/°C, respectively, and another MZI can obtain −8.405 nm/MPa and 0.038 nm/°C, respectively. Therefore, the simultaneous measurement can be achieved by utilizing two MZIs with different gas pressure and temperature sensitivities.

Impact of a pressurised membrane: Contact time

Pressurised membranes are used in various situations involving humans (protections, sports, etc). In this context, impacts mechanics of membranes is critical since under or over inflated membranes may create injuries. The effect of inflation pressure on contact time is investigated on a model experiment using a spherical membrane. Both gas pressure and impact speed decrease contact time. Direct measurements of gas pressure and temperature variations indicate an adiabatic compression in strong interaction with the membrane. The contact time of an inflated membrane is described by three dimensionless numbers, (i) the relative inflation P˜, (ii) the presso-elactic number PE that considers the gas-membrane interaction and (iii) the presso-inertial number IP that scales membrane inertia to pressure forces. A model of pressurised membrane impact is provided and compared with experiments. It shows that contact time depends mainly on IP with corrections on PE and P˜.

Front Cover: In Situ Synchrotron X‐ray Diffraction Studies of the Mechanochemical Synthesis of ZnS from its Elements (Chem. Eur. J. 49/2021)

The mechanism of the mechanochemical synthesis of cubic ZnS from its elements via ball milling was studied by in situ synchrotron diffraction experiments coupled with gas pressure measurements inside the milling vessel. The combination of both techniques reveals a heterogeneous reaction mechanism including gaseous sulfur and solid zinc. Moreover, the reaction kinetics of the phase transition from cubic to hexagonal ZnS was determined from the in situ synchrotron diffraction experiments. More information can be found in the Full Paper by C. Weidenthaler et al. (DOI: 10.1002/chem.202101260).

Gas pressure measurement using micro-corona-discharging effect in surface acoustic wave resonators

This paper reports a gas pressure sensor using surface acoustic wave resonator (SAWR) based on both the field-induced electron emission and the micro-corona-discharging (MCD) phenomena. With the micron-scale finger-gap of electrodes covered with SiO2 passivation layer, the enhanced field-effect emission (FEE) at electrodes result in the micro-corona-discharging and thus the change in the dynamic resistance of SAWR. A high Q-factor SAWR was fabricated on ST-cut quartz substrate using microelectronics processing technology, and the gas-pressure-dependent return-loss was tested, and the MCD theory and the equivalent circuit model of SAWR were used to analyze the test results. Under argon pressure range from 0 to 601 kPa, the dynamic resistance of the SAWR varies from 24.569 to 41.589 Ω at 25 °C. The resistance rate reaches 69.3%, which is far higher than that of traditional piezoresistive pressure sensors. At the same time, the oxygen pressure was also tested by the SAWR as a comparison. The SAW-based gas pressure sensors have the potential for measurement of the super-high pressure.

Hypersensitive high-temperature gas pressure sensor with Vernier effect by two parallel Fabry-Perot interferometers

We demonstrate an optical fiber sensor produced by two parallel Fabry–Perot interferometers (FPIs) for simultaneous measurement of temperature and gas pressure under high temperature environments. Each FPI is manufactured by combining hollow silica tube (HST) and optical fiber. These two FPIs respectively form reference and sensing optical paths, which are connected by a 3-dB coupler to form the Vernier effect. A fiber Bragg grating (FBG) is introduced in sensing arm FPI to measure temperature. By optimizing the structure of the two FPIs, our sensor obtains relatively low temperature cross-sensitivity, and effectively improved the fringe contrast of the reflection spectrum by using multimode fiber (MMF). The temperature sensitivity of the sensor is 12.01 pm/°C within the range of 25–600 °C. The pressure sensitivity of the sensor is as high as 63.67 nm/MPa and 21.22 nm/MPa within the range of 0–0.7 MPa at 25 °C and at 600 °C respectively, which is approximately 15-times that of the open-cavity FPI. Its simple manufacturing method and relatively low temperature cross-sensitivity have potential application in high-temperature air pressure monitoring.

Fabry-Perot Pressure Sensors Based on Polycrystalline Diamond Membranes.

Pressure sensors based on diamond membranes were designed and tested for gas pressure measurement up to 6.8 MPa. The diamond film (2” diameter, 6 μm thickness)—grown by microwave plasma chemical vapor deposition on a silicon substrate—was a starting material to produce an array of membranes with different diameters in the 130–400 μm range, in order to optimize the sensor performance. Each 5 mm × 5 mm sensing element was obtained by subsequent silicon slicing. The fixed film thickness, full-scale pressure range, and sensor sensitivity were established by a proper design of the diameter of diamond membrane which represents the sensing element for differential pressure measurement. The pressure-induced deflection of the membrane was optically measured using a Fabry-Pérot interferometer formed by a single mode optical fiber front surface and the deflecting diamond film surface. The optical response of the system was numerically simulated using geometry and the elastic properties of the diamond diaphragm, and was compared with the experiments. Depending on the diamond membrane’s diameter, the fabricated sensors displayed a good modulation depth of response over different full-scale ranges, from 3 to 300 bar. In view of the excellent mechanical, thermal, and chemical properties of diamond, such pressure sensors could be useful for performance in a harsh environment.

The usage of statistical analysis methods for controlling the operational stability of gas treatment facility

The paper considers the solutions to the scientific and practical task of improving the accuracy and reliability of natural gas consumption by conducting a statistical analysis of the results of gas pressure measurements in the pipeline, obtained from three pressure sensors during 12 hours. The importance of this task is underlined by the fact that the confidence interval for RMS errors is usually very wide. Testing of the hypothesis of the instability absence in the process of measuring gas pressure is carried out using a single factor dispersion analysis (the equation of the median values), a linear regression analysis (no influence of time on the value of the indicator for each voter) and a covariance analysis (no difference in the functional influence of the time on the number of an indicator). Three series of the measurement results of X control indicator (gas pressure in the pipeline) have been used. The analysis has confirmed the hypothesis that there are no disruptions to the stability of the gas pressure measurement process, which makes the pressure sensors metrologically reliable. It has been proved that the scientific and applied problems of increasing the reliability of objects control and diagnostics with stochastic parameters and improving their metrological reliability are relevant and important for the development of the theory and practice of non-destructive control and functional diagnostics of objects.
 Keywords: gas equipment; metrological reliability; statistical evaluation.

Low gas pressure sensor based on a polymer optical fiber grating.

A fiber Bragg grating (FBG) inscribed Zeonex-based novel, to the best of our knowledge, side hole polymer optical fiber (SHPOF) is proposed and demonstrated for low gas pressure measurement above and below the atmospheric pressure. Two different grades of Zeonex have been used to fabricate the core and cladding of this fiber, thereby making it dopant free. The side hole introduced in the cladding is parallel to the fiber core. A few ultrashort pulses with nanosecond duration have been used to write the FBG in the core of this fiber. The incorporation of the side hole leads to enhancement of pressure sensitivity as well as low hysteresis and performance repeatability compared to Zeonex-based conventional polymer optical fiber (CPOF). Above the atmospheric pressure, the proposed probe shows a pressure sensitivity of 0.47 pm/kPa, which is 80% more compared to the Zeonex-based CPOF and 0.48 pm/kPa for regime below atmospheric pressure. The sensor has a resolution of 2.12 kPa and exhibited very low hysteresis.

Optical Fiber Gas Pressure Sensor Based on Polydimethylsiloxane Microcavity

We experimentally demonstrated a high sensitive gas pressure sensor, which also has more concise processing steps and lower cost. The sensor was fabricated by splicing the single-mode fiber (SMF) and a short section of hollow-core fiber (HCF) which was filled with a Polydimethylsiloxane (PDMS) film to form an enclosed air microcavity with the length of 55 μm. The thin PDMS film also plays a role in reflecting the beam. The thermo-optical effect and the thickness of PDMS film can affect the cavity that is sensitive to external pressure. When the thickness of the PDMS membrane is 3 μm, the measured gas pressure sensitivity reaches to 52.143 nm/Mpa, the linearity is 99.86%, and the cross-sensitivity of the gas pressure over temperature is lower than 2.51 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> Mpa/°C. Moreover, the compact structure, high sensitivity, high mechanical strength, and convenient fabrication make it suitable for measuring gas pressure in harsh conditions.

Simultaneous measurement of gas temperature and pressure based on Rayleigh–Brillouin​ scattering in kinetic region of less than one standard atmospheric pressure

In order to detect high-precision atmospheric temperature data and realize simultaneous detection of atmospheric temperature and pressure, a decoupling method for the envelope spectrum of Rayleigh–Brillouin scattering in kinetic region of less than one atmosphere is presented. The parameters of envelope spectrum are characterized by using an experimental setup with the frequency locking, continuous tunable cavity Fabry–Perot interferometer, temperature and pressure control technologies. The nitrogen with the purity of 99.99% and compressed air acted as the examples are putted into the gas cell. Combined with the characteristics of actually detecting atmospheric parameters, the correction method is adopted to eliminate the influence of residual Mie scattering on the envelope spectrum. By choosing four discrete points on the envelope spectrum of Rayleigh–Brillouin scattering, the gas temperature and pressure can be inversed. There is a nice linearity between the measured results and theoretical values.

Plastic zone range of a roadway considering the creep effect

The plastic zone range is an important parameter in the analysis of damage characteristics and the degree of damage to the rock surrounding a roadway. Based on the establishment of a plastic zone calculation model considering the creep effect, this paper obtains the characteristics of the change in the plastic zone damage range with time by solving the model. Additionally, the validity of the model is verified by field experiments. The research results can provide guidance for gas pressure measurement and gas drainage in coal mines.

(Invited) Internal Gas Pressure Measurement of Packaged Electric Double Layer Capacitors

One mode of electric double layer capacitor failure is package rupture, which usually leads to rapid deterioration of its electrical performance. This typically is caused by gas generated within a sealed capacitor with a subsequent pressure rise that eventually leads to the package bursting. The rate of gas generation, which ultimately can determine capacitor life, depends on materials purity, capacitor operating voltage, and the capacitor operating temperature. We measured the internal gas pressure and rate of gas pressure rise in spiral-wound, packaged electric double layer capacitors using an indirect and a direct approach. The indirect approach relied on physically measuring capacitor package deformation that had been caused by the internal gas pressure. This was then quantified by comparing the value with deformation caused by a known applied gas pressure. The direct approach relied on the use of an attached and calibrated solid-state pressure transducer. Internal gas pressure measurements using both approaches were made on 100-F-size electric double layer capacitors held at several temperatures with different applied voltages. Experimental details are reported with internal pressure measurements shown for 2000 hours of capacitor aging at 65 oC. Figure 1

A method for assessing the uncertainty of a secondary dynamic pressure standard using shock tube

Pressures are often measured in fast transient regimes, even if the transducers are not calibrated in dynamic regimes. If the solutions proposed for primary calibration of the dynamic response of pressure sensors must be fully recognised, secondary methods are also needed to disseminate the standard to final users. A method for assessing measurement uncertainty, carried out by comparison with a reference transducer, traceable to primary standard, is proposed here. A typical application is gas pressure measurement. This paper follows and supplements the work done on the Mach number method in 2018. For this work the reference transducer is calibrated by the ‘collective standard method’ currently used in the ‘Laboratoire de Métrologie Dynamique’( LNE/ENSAM). This primary standard uses steps of pressure as inputs for dynamic pressure calibration that are generated by shock tubes (STs) and fast-opening devices (FODs). The uncertainty on dynamic sensitivity is evaluated from the quasi-static to the low, medium and high-frequency range (up to 10 kHz) using bandwidth comparisons. To calibrate a secondary standard transducer in gas, the method also requires one or two step generators: an ST for high-frequency range calibration and a FOD for the low-frequency range. Concerning the main results of this paper, the transducer to be calibrated and the reference transducer are placed symmetrically on the endplate of an ST. The amplitude of the pressure step generated by the tube is used to excite the transducers. Finally, the uncertainty on the sensitivity in dynamic conditions is determined by comparison with a model expected to be exhaustive. The results are provided as an uncertainty budget assigned frequency by frequency. The question asked in this work concerns the measurand used in secondary calibration: can a pressure step generated by a non-ideal ST be used in the process of calibration by comparison, i.e. for a secondary dynamic calibration? A method is proposed. Since the secondary method is derived directly from the primary one, this paper recaps the primary dynamic calibration method in gas and the budget of the associated uncertainty. Then the paper presents a secondary method and options to overcome the principal default identified in the ST frequency range, namelythe non-uniform pressure fields existing in the tube.

A New Method for the Measurement of Gas Pressure in Water-Bearing Coal Seams and Its Application

Coal seam gas pressure is one of the fundamental parameters used to assess coal seam gas occurrence and is an important index in assessing the risk of gas disaster. However, the geological characteristics of coal seams become increasingly complex with increasing mining degree, thus decreasing the accuracy and success rate of direct methods for measuring gas pressure. To address such issues, we have developed a new method for direct measurement of gas pressure in water-bearing coal seams. In particular, we developed a pressure measurement device based on theoretical analysis and quantified the basic parameters of the device based on well testing. Then, we verified the applicability of our method based on comparative analysis of the results of field experiments and indirect measurements. Our results demonstrate that this new method can resolve the effects of water pressure, coal slime, and other factors on the estimation of gas pressure. The performance of this new method is considerably better than that of traditional methods. In particular, field test results demonstrate that our method can accurately and efficiently measure gas pressure in water-bearing coal seams. These results will be of great significance in the prevention and control of coal seam gas disaster.