Gas Pressure Measurement Research Articles

Erratum: Tomographic measurement of the intergalactic gas pressure through galaxy-tSZ cross-correlations

Erratum: Tomographic measurement of the intergalactic gas pressure through galaxy-tSZ cross-correlations

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

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

Optimization of Filtered Rayleigh Scattering for the Measurement of Pressure and Temperature

ABSTRACT The stand-off measurements of temperature and pressure are important for a variety of physical and engineering processes. Filtered Rayleigh scattering (FRS) configurations that enhance and suppress sensitivity to temperature are modeled and demonstrated using premixed, atmospheric methane-air Hencken burner generating temperatures up to 2100 K. For a characteristic flame gas mixture, modeling of the FRS signal using a molecular iodine filter shows that conditions exist for which the signal has a greater dynamic range or does not change significantly with respect to high gas temperatures. Laser Rayleigh scattering (LRS) measurements coupled with nonadiabatic flame simulations validate the temperatures, while FRS measurements are compared with the model predictions for different observation angles and iodine cell conditions. Results are discussed in the context of making direct measurements of gas pressure at high temperatures and within turbulent flames.

Measurement of gas pressure inside large-format prismatic lithium-ion cells during operation and cycle aging

In this study we investigate the influence of the state of charge (SOC), temperature and aging on the gas pressure inside prismatic lithium-ion cells with a LiNi1/3Mn1/3Co1/3O2 cathode and a graphite anode. The internal gas pressure inside lithium-ion cells has so far been only investigated for small cells using large-size laboratory measurement equipment. We show for the first time that measuring the internal gas pressure is also possible for large-format prismatic cells and by using miniaturized pressure sensors that can be integrated into a battery pack. We also show that this measurement method enables the monitoring of the gas pressure during long-term cycling without leading to premature battery failure or accelerated aging. The gas pressure depends on the SOC in a non-linear way. This is caused by the dependence of the electrode volumes on the degree of lithiation. The gas pressure also correlates non-linearly with temperature, and the magnitude of temperature dependence increases with aging. During long-term cycling, the pressure irreversibly increases, which is most likely due mainly to gas formation. The increase in pressure correlates with a loss of capacity, which basically qualifies internal gas pressure for an indicator for state of health.

Calculation method of gas‐pressure rising process in puffer chamber of high‐voltage SF6 circuit‐breaker

AbstractRegarding a PTFE (polytetrafluoroethylene) nozzle ablation due to arc radiation exposure in SF6 circuit‐breaker, the ablated mass of the nozzle was formulated as a function of an arc current and an internal radius of the nozzle surface considering the radiation power absorbed on the surface. Furthermore, this formulation contributed to subsequent development of calculation method for evaluating gas pressure rise process during current interruption. And, verification experiments of the calculation method were performed with a model SF6 circuit‐breaker equipped a puffer chamber. Calculation results derived from the developed calculation method showed good agreement with measured gas pressure rise process. On the basis of the verified results, a discussion was made to explain pressure rise mechanism.

A Simple, Highly Sensitive Fiber Sensor for Simultaneous Measurement of Pressure and Temperature

A simple, highly sensitive fiber Fabry-Perot interference sensor based on polydimethylsiloxane (PDMS) is proposed and demonstrated for simultaneous measurement of gas pressure and temperature. The sensor is fabricated by fusion splicing a short segment of hollow capillary tube to a standard single mode fiber and injecting PDMS in sections into capillary tube, then three reflecting surfaces are formed. Experimental results show that sensitivities of temperature and gas pressure are 2.62 nm/°C and 20.63 nm/MPa, respectively. The proposed sensor has advantages of compact size, low cost, robust structure, easy fabrication, and it is applicable to real sensing application.

Experimental Investigation on the Abnormal Measurement of Gas Pressure during Canister Desorption of Coal Cuttings

Accurate measurement of gas pressure during canister desorption of coal cuttings is an important foundation to prevent coal gas dynamic hazards and determine gas content of coal by volumetric method. It was a new finding that gas pressure in the insulation canister increased and then decreased during the initial desorption stage in the field test, which was different with common sense about gas desorption law. We took a series of experiments to explore the possible reason for this in the laboratory. The experimental results have shown the abnormal measurement of gas pressure was caused by the temperature decrease induced by adsorbing the heat and less external energy during canister desorption. The test condition was a key factor to accurate measurement of gas pressure in the canister. These findings offered insight into the temperature variation and also changed our understanding of the temperature effect on the gas pressure measurement during canister desorption of coal cuttings. The temperature variations induced by the adsorbed gas desorption should be taken into account in engineering application, especially the accurate measurement was applied for the initial stage of gas desorption.

Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder streams characteristics is essential to control the process and improve its reliability and reproducibly for industrial applications. This paper proposes multiple experimental techniques, such as gas pressure measurement, optical and weighting methods, to analyze the gas and particle velocity, the powder stream diameter, its focal plan position and density. This was carried out for three nozzle designs and multiple gas and powder flow rates conditions. The results reveal that (1) the particle stream follows a Gaussian distribution while the gas velocity field is closer to a top hat one; (2) axial, carrier and shaping gas flow significantly impact the powder stream’s focal plan position; (3) only shaping gas, powder flow rates and nozzle design impact the powder stream diameter. 2D axisymmetric models of the gas and powder streams with RANS turbulent model are then performed on each of the three nozzles and highlight good agreements with experimental results but an over-estimation of the gas velocity by pressure measurements.

Basic Metrology for 2020.

2019 was a big year for metrology. The international system of units was revised on World Metrology Day, May 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> , that year [1]. What will 2020 bring? In this article we discuss five promising advances that we have on a watchlist for 2020. First, we describe the measurement of volume and gas pressure using electromagnetic waves. These measurements rely on the fixed value of the speed of light in vacuum c <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . We then pivot to the Planck constant h. SI traceable measurements of mass and force can be obtained from h. Interesting developments are coming in mass metrology since the definition changed from the mass of the international prototype of the kilogram to the value of the Planck constant. Adding the elementary charge e to h gives access to resistance and impedance measurements via the quantum Hall effect. This has been a very interesting field for some time, since the discovery of graphene in 2004. The last section explains how the noise across a resistor can be used to measure thermodynamic temperature. As will be shown, the temperature can be linked to the quotient of the Boltzmann constant k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> and the Planck constant.

Oxidation and Characterization of Low-Concentration Gas in a High-Temperature Reactor

To achieve the efficient utilization of low-concentration mine gas, reduce resource waste and alleviate environmental pollution, the high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50%, which is directly discharged into the atmosphere during coal mine production, was carried out to recover heat for reuse. The gas oxidation equipment was improved for the heating process and the safety of low-concentration gas oxidation under a high-temperature environment was evaluated. The experimental results showed that the reactor could provide a 1000 °C high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 °C. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The minimum pressure difference was 4 kPa (air) and the maximum was 11 kPa (1.50% gas). The explosion limit varied with the temperature and the blend of oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration of gas is still safe after the shift of the explosion limit, which provides a safe concentration range for the efficient use of low-concentration gas in the future.

Direct measurement of pore gas pressure and water/gas phase transitions during methane hydrate dissociation

Methane hydrate deposits worldwide are vast potential sources of natural gas. Although field tests, and many laboratory studies, of hydrate dissociation have been performed, long term gas recovery from hydrate deposits still requires a comprehensive knowledge of the pore gas pressure and related phenomena. Pore gas pressure can significantly affect the safety and efficiency of gas production from hydrate deposits. Capillary-trapped residual gas saturation, known to cause elevated pore gas pressure during methane hydrate dissociation, was measured by magnetic resonance. Elevated pore gas pressure was estimated to be 8500 psi. Different molecular species and fluid environments produced during the methane hydrate dissociation process were discriminated. The results show that the majority of gas is initially confined as capillary-trapped gas upon dissociation. The evolution of water and gas saturations was measured as a function of time. Water migration, bed failure, and crack growth, related to elevated pore gas pressure, were observed both spatially and temporally resolved. Hydrate dissociation proceeded from the sand pack exterior to the interior, in a shrinking core manner, due to heat transfer effects. It was observed that hydrate dissociation resulted in pronounced water migration toward the low-pressure surface. This study was undertaken with advanced magnetic resonance imaging (MRI) and magnetic resonance (MR) methods employing a MR/MRI-compatible metallic core holder. A hydrate-bearing sand pack, with 96% initial hydrate saturation, underwent dissociation by depressurization at 290 psi and 4 °C.

Study on the Interaction between Low-Viscosity High-Permeability Pregrouting Sealing Material and Coal and Its Application

In order to ensure the intactness of pressure-measuring boreholes and the accuracy of gas pressure determination, pregrouting treatment with polymer materials is frequently applied to bedding drilling in coal mines. However, the existing polyurethane materials are of high viscosity, low permeability, and poor safety, bringing great difficulties to their field promotion and application. In view of this problem, after optimization and experiments, polylactide polyol/polyether polyol 4110/isocyanate was determined as the target system. Bio-based benzoxazine (Boz-F), red phosphorus, and melamine with a mass ratio of 2 : 1 : 2 were used as the flame retardant, which then underwent mechanical modification by hollow glass bubbles. Finally, the pregrouting material with low viscosity and high permeability was compounded, and its interaction with coal was experimentally studied. The results show that compared with traditional polyurethane, the new material increases the effective consolidation distance in the coal seam by 40% on average. Its permeation radius is also larger than the calculated radius of the plastic softening zone of a borehole. In addition, the strengths of coal-new material consolidated products with different ratios fully surpass those of coal-polyurethane material consolidated products. The enhancement of compressive strength and bending strength is up to 153% and 161%, respectively. The field application indicates that after pregrouting treatment of boreholes in the coal seam with the new material, the borehole formation rate reaches 100%. Therefore, the new material is safe and practical for gas pressure measurement through bedding drilling on site.

Mechanical Stability of Filaments for ITER Diagnostic Pressure Gauges Relating to Creep and Fatigue

Diagnostic pressure gauges (DPGs) shall provide measurements of the neutral gas pressure in various locations of the International Thermonuclear Experimental Reactor (ITER) vacuum vessel. This parameter is essential for the basic control of ITER operation as well as for input to physics models of the plasma boundary. The hot cathode (filament) is the component of the DPG sensor that is exposed to most demanding loads. In order to reach the required electron emission from the filament, it has to be heated to high temperatures by a direct current. As a result, thermal stresses appear, and in the presence of a magnetic field, additional mechanical stresses caused by Lorentz forces arises. On the one hand, due to a large number of pulses foreseen in ITER, this load will be cyclic, which may result in filament failure caused by fatigue. On the other hand, the longest pulses in ITER are expected to be in the order of 30 min, and thus, filaments could fail due to creep. In order to verify that the filament of the DPG sensor can withstand fatigue and creep dedicated experiments have been conducted. Results of these tests are discussed in this article.

Experimental assessment of damping and heat transfer coefficients in an active free piston Stirling engine using genetic algorithm

In this work, two critical parameters of an active free piston Stirling engine (AFPSE) namely, the heat transfer and damping coefficients are practically estimated using genetic algorithm (GA). Although, the mentioned parameters play a significant role in the accuracy of data obtained from the mathematical models, they cannot be measured directly. Indeed, there are no specific sensors to measure damping and heat transfer coefficients and it is the main challenge to achieve their practical values. Consequently, this work attempts to present an innovative scheme to estimate such immeasurable parameters based on other measurable variables. First, the modeling approach of the AFPSE is described and the significance of the mentioned parameters is highlighted. Then, two experimental works are conducted to measure gas pressure and power piston displacement at each engine frequency for identifying the immeasurable parameters indirectly. Subsequently, an appropriate objective function based on the error between the experimental and simulation data is defined for each of the identification scheme. Next, the GA is used to achieve the mentioned unknown parameters so as to minimize the proposed objective functions. Finally, the experimental and simulated outcomes clearly affirm the effectiveness of the proposed identification scheme of the considered immeasurable parameters.

Phase-shifted fiber Bragg grating modulated by a hollow cavity for measuring gas pressure

A gas pressure sensor, based on a phase-shifted fiber Bragg grating (PS-FBG) modulated by a hollow cavity, is proposed and demonstrated in this Letter. The device was fabricated by fusing a hollow-core fiber (HCF) between two single-mode fibers (SMFs) exhibiting FBGs that were inscribed using line-by-line femtosecond (fs) laser etching. A pair of micro-channels were drilled orthogonally into the HCF using an fs laser to allow the argon gas to get in and out freely. Such a sensor exposes a high spectrum finesse, e.g., a Q -factor of ∼ 7302 , which can be improved by increasing the grating pitch quantity. Furthermore, a high gas pressure sensitivity of 1.22 nm/Mpa is obtained, corresponding the improved sensor with a grating pitch quantity of 300 and a hollow cavity length of 88.3 µm. In addition, the device exhibited a low temperature sensitivity of 8.92 pm/°C.

Vacuum metrology based on refractive index of gas

With the development of vacuum technology, subject to the influence of directional flow and uneven temperature, the thermodynamic equilibrium state is destroyed. In this case, the pressure reference is not suitable for characterizing the vacuum state. To ensure the long-term stability and reproducibility of the measurement system, vacuum metrology will be characterized by gas density. The precisive measurement of gas refractive index based on a Fabry-Perot cavity can be used to derive the gas density. This kind of an optical measurement of vacuum links macroscopic dielectric constants of gases with microscopic polarization parameters of atoms and molecules. It replaces the physical standard based on the mercury pressure gauge with the quantum standard. In this paper, we discuss the reverse process from refractive index to gas pressure, and use the laser-locked Fabry-Perot cavity method to measure the refractive index of argon gas. The contribution of related parameters to the uncertainty of determined gas pressure is analyzed. The influences of material parameters and experimental parameters such as gas molar susceptibility, molar susceptibility, dielectric second Virial coefficient and temperature on gas pressure accuracy are analyzed. The result shows that the uncertainty in our measurement of argon within 1 atm is &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$u = \sqrt {{{(6\;{\rm{mPa}})}^2} + {{(73 \times {{10}^{ - 6}}p)}^2}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20200706_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. Currently, the uncertainty mainly comes from the measurement deviation of gas temperature inside the cavity. After repeating the measurement a few times, the results show that the statistical uncertainty of refractive index is within 100 ppm, which is limited by the accuracy of the pressure gauge used here. In addition, we compare the dipole calculated by the &lt;i&gt;ab initio&lt;/i&gt; method with that by the DOSD method. The results show that the dynamic polarizability obtained by the &lt;i&gt;ab initio&lt;/i&gt; method is consistent with our experimental results. In conclusion, these experimental results show that the measurement of gas pressure based on the gas refractive index has high repeatability and accuracy. If the temperature control and corresponding measurement accuracy of the gas are further improved, this method can also be used to obtain high-precision microscopic parameters such as the polarizabilities of atoms and molecules. In the future work, we will focus on improving the temperature control and the design of the cavity to reduce cavity leakage and deflation. It is possible that the measurement accuracy of the gas pressure will be increased to 10 ppm level, which is the same level as the current standard pressure gauge and will become a new standard for pressure measurement in the future.

Gas Pressure Measurement Device and Medical Vacuum Design

Two methods are used in a digital pressure meter available in the market, namely positive pressure, and negative pressure. The positive one is used to measure the air pressure on a sphygmomanometer and medical gas pressure at an outlet in the treatment room so that operators can easily check medical gas pressure for the safety of the patient, or they can routinely check to find out how much pressure of the medical gas. Based on the background, the research aimed to design a digital pressure meter equipped with a medical gas measurement mode so that the device can be used to calibrate the sphygmomanometer, suction pump, and measure the medical gas pressure available at the medical gas outlet in each treatment room.

Tomographic measurement of the intergalactic gas pressure through galaxy–tSZ cross-correlations

ABSTRACT We cross-correlate maps of the thermal Sunyaev–Zeldovich (tSZ) Compton-y parameter published by Planck with the projected distribution of galaxies in a set of low-redshift tomographic bins. We use the nearly full-sky 2MASS Photometric Redshift and WISE × SuperCOSMOS public catalogues, covering the redshift range z ≲ 0.4. Our measurements allow us to place constraints on the redshift dependence of the mass–observable relation for tSZ cluster count analyses in terms of the so-called hydrostatic mass bias parameter $1-b_{\scriptscriptstyle \rm H}$. These results can also be interpreted as measurements of the bias-weighted average gas pressure 〈bPe〉 as a function of redshift, a quantity that can be related to the thermodynamics of gas inside haloes and used to constrain energy injection processes. We measure $1-b_{\scriptscriptstyle \rm H}$ with $\sim \!13{{\ \rm per\ cent}}$ precision in six equispaced redshift bins, and find no evidence for a redshift-dependent mass bias parameter, in agreement with previous analyses. Our mean value of $1-b_{\scriptscriptstyle \rm H}= 0.59\pm 0.03$ is also in good agreement with the one estimated by the joint analysis of Planck cluster counts and cosmic microwave background anisotropies. Our measurements of 〈bPe〉, at the level of $\sim \!10{{\ \rm per\ cent}}$ in each bin, are the most stringent constraints on the redshift dependence of this parameter to date, and agree well both with previous measurements and with theoretical expectations from shock-heating models.

Primary gas-pressure standard from electrical measurements and thermophysical ab initio calculations

Mechanical standards for measuring gas pressure up to 7 MPa based on a piston–cylinder system are known with relative uncertainties on the order of 1 ppm (ref. 1). The challenges in an experimental realization lie in determining the effective area of special pressure balances and in accounting for the pressure distortion. Comparisons of the mechanical pressure standard with independent methods to exclude sources of systematic uncertainty are currently available only around 0.1 MPa at the required uncertainty levels. Here, such an independent cross-check is performed up to 7 MPa based on electrical measurements of helium gas. Enabled by recent progress in ab initio calculations, pressure can be accessed through measurement of the dielectric constant. By using theoretical values for the polarizability and the virial coefficients of helium, the change in capacitance and hence the pressure can be determined up to 7 MPa. The relative uncertainty of this method is below 5 ppm and can serve as a new primary pressure standard complementary to the mechanical pressure standard. This answers the long-standing question whether a pressure standard based on capacitance measurements could be devised2. The measurement of the dielectric constant combined with ab initio calculations of the polarizability and the virial coefficient of helium provides a new primary pressure standard, which is complementary to the mechanical standard.

An immersive resonant sensor with microcantilever for pressure measurement

A micro electromechanical systems (MEMS) resonant sensing chip with microcantilever has been developed to measure gas pressure by immersing it in gaseous environment. The microcantilever was designed to sense surrounding gas molecules loading, owing to the gas density sensitive to the pressure, then the resonant frequency shifts of sensing chip were induced under different pressures. Especially, the sensing chip featuring no diaphragm realized embedded package and installation for the immersive measurement. The resonance response of the sensing chip for target pressure was theoretically analyzed and simulated, and a packaged pressure sensor with the proposed sensing chip was tested under flexural and torsional modes of the microcantilever. The experimental results proved that the proposed sensor had preferable measuring performance under the torsional mode with the RSS (root sum square) accuracy of 0.21%FS in the working range of 10–560 kPa. The temperature compensation was presented to alleviate the temperature disturbance for the sensor, and the maximum deviation of the frequency was 59 ppm over the full pressure and the temperature range of 26–55 ℃. The proposed sensing chip is potentially a better choice for pressure sensors with measurement demand for immersive gas pressure.