Total Pressure Measurements Research Articles

Design and validation of an online partial and total pressure measurement system for Li-ion cells

Online Electrochemical Mass Spectrometry (OEMS) provides unparalleled access to the details of electrode/electrolyte interfacial reactions in electrochemical systems. Herein, the development and validation of an OEMS system along with detailed calibration protocols and limits of detection sensitivity are showcased. Combined partial and total pressure monitoring provides a clear advantage when detailing major and minor gas reactions as well as when determining unaccounted gases. A classical Li-ion LiCoO2/Graphite full cell is studied during overcharge to 4.9 V vs. Li+/Li at 50 °C at an unprecedented level of detail and the results are compared to LiCoO2/LiFePO4 and Graphite/LiFePO4 cells in order to differentiate between gases forming at the anode and cathode. The release of O2 from LixCoO2 (x < 0.4) during both charge and discharge demonstrates that its degradation is dependent on state of charge 1-x rather than potential. The presented methodology establishes an improved experimental basis for deeper understanding of interfacial reactions in batteries and electrochemical systems alike.

Simulation of undrained quasi-saturated soil with pore pressure measurements using a discrete element (DEM) algorithm

A method is presented for using DEM to find the pore pressure, total stress, and effective stress within a granular assembly during either undrained or drained conditions, by using poroelastic principles to directly determine the pore fluid pressure. The paper considers both the saturated and quasi-saturated conditions, the latter meaning a slightly unsaturated granular material, in which isolated gas bubbles reduce the compressibility of the pore fluid but do not form liquid bridges between the particles. The presence of air increases the pore fluid compressibility and is known to improve undrained strength and liquefaction resistance and has been considered for remediation of loose, susceptible soils. Past DEM studies have approximated undrained loading as a constant-volume condition, but this approximation does not allow the simulation of complex loading sequences, even with fully saturated materials. The paper’s method allows the direct control and measurement of total stress, water pressure, and water influx. The method includes the effects of water compressibility, grain compressibility, pore air compressibility, surface tension, air solubility within the pore liquid, and vapor pressure of the water gas phase. These factors all affect the evolving sizes of the bubbles and the consequent compressibility of the air–water mixture. The resulting algorithm is applied in three examples: the laboratory saturation of a soil specimen by increasing chamber pressure and back pressure, the undrained triaxial compression of quasi-saturated specimens, and the cyclic undrained triaxial liquefaction of quasi-saturated specimens. Example simulations agree favorably with laboratory tests.

The association between healthy eating index and serum antioxidant indices in patients with different degrees of cataract compared to healthy subjects: a case-control study

Purpose Studies conducted on association between diet and cataract, found conflicting results. This paper aims to investigate the association between healthy eating index (HEI) and serum antioxidant and oxidant indices in patients with different degrees of cataract compared to the healthy subjects. Design/methodology/approach Ninety volunteers (aged &gt; 50 years) were divided into the cataract (n = 45) and healthy control (n = 45) groups in this case-control study. Anthropometric variables, HEI score, serum total oxidant capacity (TOC) and total antioxidant capacity (TAC), blood pressure, physical activity and stress measurements were done for all participants. Findings There was a significant difference in stress level between subgroup of first-degree cataract and healthy controls (16.6 ± 2.3 vs 42.5 ± 29.0, p &lt; 0.001) as well as third-degree cataract (16.6 ± 2.3 vs 75.2 ± 22.6, p &lt; 0.001). Serum TAC was significantly higher in healthy people compared to the first-degree (1.2 ± 0.2 vs 1 ± 0.2, p = 0.002) and third-degree cataract patients (1.2 ± 0.2 vs 1.0 ± 0.2, p = 0.013). Also, serum TOC was significantly lower in healthy controls compared to the first-degree (8.2 ± 1.1 vs 9.2 ± 1.0, p = 0.006) and third-degree cataract patients (8.2 ± 1.1 vs 9.1 ± 1.2, p = 0.015). There was a significant direct correlation between moderation (r = 0.61, p = 0.019) and total score of HEI (r = 0.57, p = 0.031) with serum TAC only in the first-degree cataract patients. Also there was a significant negative correlation between moderation score of HEI with serum TOC in the first-degree cataract patients (r = −0.60, p = 0.025), and there was a significant negative correlation between moderation (r = −0.36, p = 0.017) and total score (r=−0.35, p = 0.021) of HEI and TOC in the total cataract patients. Originality/value To the best of the authors’ knowledge, this is the first study on the assessment of the relationship between components of HEI and serum antioxidant indicators in different types of cataract compared to healthy individuals. It could be a start point for more detailed and large-scaled studies, even intervention studies, in this field.

Neutral gas analysis for JET DT operation

Neutral gas analysis, the measurement and evaluation of total and partial pressures, is a key technique to study the impact of neutral gas dynamics on retention, recycling and release processes of fuel or impurity species in fusion devices. At JET, the experiment closest to ITER in terms of operating parameters and size, various detectors and techniques for partial pressure and total pressure measurements are deployed together to characterise neutral gas dynamics during and after plasma operation on various toroidal and poloidal locations. An extensive modification of JET's sub-divertor neutral gas diagnostic system aims at retaining and extending established measurement capabilities in the forthcoming Deuterium-Tritium (DT) experiments (DTE2). To achieve DT compatibility, a separation of radiation-sensitive electronics from the sensor and adequate radiation shielding is required, as well as utilisation of a DT compatible differential pumping system with adjustable throughput to account for the strong pressure variation in the sub-divertor region. Finally, the sub-divertor neutral gas diagnostic will be equipped with multiple Residual Gas Analysers (RGAs), utilising quadrupole mass spectrometry and electrostatic ion-trap-principles, all operating with remote electronics located behind the biological radiation shield. These RGAs will record data in a fast selected discrete mass mode during plasma pulses (cycle ∼2 s) and will automatically switch back to continuous data recording (cycle ∼100 s) afterwards. They will be complemented by a newly improved Penning gauge spectroscopy configuration in particular supporting the He and D2 separation relevant for DT operation. The distance between these devices and their associated control unit is typically 15m . A newly developed RGA with a cable length of 80 m, compatible with the ITER environment, will also be employed for the first time. This set-up and its operation in DTE2 will provide vital input to the development of the ITER divertor RGA in the most relevant environment currently available.

Der Alleskönner der Messtechnik

SummaryThe all‐rounder of measurement technology – Monitoring of vacuum propertiesThe Novion is an all‐rounder of vacuum measurement technology. The newly developed sensor is based on a novel ion source and an integrated TOF mass spectrometer. The new vacuum measuring instrument is versatile: precise total pressure measurement over a wide range and simultaneously determination of helium partial pressure and residual gas analysis. By using the patented ion source, the instrument also achieves a high dynamic range without the use of a cost‐intensive electron multiplier, down to the UHV range. The Novion comes with a compact design, easy maintenance and an intuitive operation. The article covers the fields of application of this multi‐method sensor and explains its functionality in detail.

Solubility of Carbon Monoxide and Hydrogen in Methanol and Methyl Formate: 298–373 K and 0.3–3.3 MPa

In this study, we report the solubility of the gases carbon monoxide (CO) and hydrogen (H2) in methanol and methyl formate using the synthetic isothermal method via total pressure measurement. The ...

Axial flow development characteristics of circular and triangular supersonic jets in the presence of an annular coflow at large separation distance

Experimental studies were conducted to assess the effect of an annular coflow which surrounded a supersonic core jet in a coaxial jet system. Two different core jet shapes were employed which were circular and equilateral triangular. The core jets were maintained at two different total pressures, i.e. 360 and 550 kPa which corresponded to overexpansion conditions. The effect of coflow which surrounded core jet at a distance larger than the core jet diameter was such that the supersonic core length of the core jet was reduced in contrast to the elongation which was reported by earlier researchers for closer distances between the two jets. The Schlieren images of the coaxial jet system had shown that the region between the jet boundary of core jet and inner boundary of the annular coflow had a strong interaction with core jet which was characterised by a wave system and vortices. This region caused a reduction in supersonic core length and weakening of shock structure in the core jet. These findings have been corroborated by total pressure measurements along the core jet centreline. For the same operational conditions, the coflow caused reduction in supersonic core length more for triangular core jet when compared to that for circular core jet.

Horizontal tail local angle-of-attack and total pressure measurements through static pressure ports and Kiel pitot

ABSTRACTAircraft handling qualities may be influenced by wing-tip flow separations and horizontal tail (HT) reduced efficiency caused by loss of local dynamic pressure or local tailplane flow separations in high angle-of-attack manoeuvres. From the flight tester’s perspective, provided that the test aircraft presents sufficient longitudinal control authority to overcome an uncommanded nose-up motion, this characteristic should not be a safety factor. Monitoring and measuring the local airflow in the aircraft’s HT provides information for safe flight-test envelope expansion and data for early aerodynamic knowledge and model validation. This work presents the development, installation and pre-flight calibration using computational fluid dynamics (CFD), flight-test calibration, results and benefits of differential pressure based local angle-of-attack and total pressure measurements through 20 static pressure ports and a Kiel pitot. These sensors were installed in a single-aisle, four-abreast, full fly-by-wire medium-range jet airliner with twin turbofan engines and conventional HT (low vertical position).

Simple Apparatus for the Measurement of Total Pressure of Polymer‐Solvent Mixtures

Simple Apparatus for the Measurement of Total Pressure of Polymer‐Solvent Mixtures

VGAM: Compact and Low‐Power Mass Spectrometer‐Based Instrumentation for Volcanic Gas Monitoring

AbstractCompact mass spectrometers (MSs) can provide simultaneous multispecies analysis with high sensitivity and precision. For volcanic gas monitoring in situ, instrumental mass spectrometry requires reliability and ruggedness combined with low power usage and portability. The Volcanic Gas Analytical Monitor (VGAM) is capable of quantitative molecular analysis of a variety of atmospheric and volcanic gases in a single sensor by ion trap mass spectrometry. These gases include H2, He, H2O, N2, O2, Ar, NO, N2O, CO, CO2, H2S, SO, SO2, and CH4. Unlike previous field instruments using magnetic sector and quadrupole MSs with vacuums backed by compact turbomolecular pumps, the VGAM uses a low‐power autoresonant ion trap MS and nonevaporable getter‐ion pumped vacuum that operates at only 25‐W total power, which is often the power requirement for just the MS. Ratiometric mass spectral response is combined with total pressure measurements to report absolute partial pressures. Data are generated in real time and are recorded to internal flash memory. Relatively low power (&lt;1 W) data telemetry to remote sites is possible. Analysis of volcanic plumes, fumaroles, and solfatara fields is accomplished by direct inlet of gases, after trapping as much excess water vapor in both the external and internal foreline as possible. We report herein on the VGAM autorun and postprocessing procedures, initial calibration results for CO2, and the results of a brief field deployment at Sulfur Banks solfatara field, Kilauea Volcano, Hawaii.

Influence of Leakage Flows on Hot Gas Ingress

One of the most important problems facing gas turbine designers today is the ingestion of hot mainstream gases into the wheel-space between the turbine disk (rotor) and its adjacent casing (stator). A rim seal is fitted at the periphery and a superposed sealant flow—typically fed through the bore of the stator—is used to prevent ingress. The majority of research studies investigating ingress do so in the absence of any leakage paths that exist throughout the engine's architecture. These inevitable pathways are found between the mating interfaces of adjacent pieces of hardware. In an environment where the turbine is subjected to aggressive thermal and centrifugal loading, these interface gaps can be difficult to predict and the resulting leakage flows which pass through them even harder to account for. This paper describes experimental results from a research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. The facility was specifically designed to incorporate leakage flows through the stator disk; leakage flows were introduced axially through the stator shroud or directly underneath the vane carrier ring. Measurements of CO2 gas concentration, static pressure, and total pressure were used to examine the wheel-space flow structure with and without ingress from the mainstream gas-path. Data are presented for a simple axial-clearance rim-seal. The results support two distinct flow-structures, which are shown to be dependent on the mass-flow ratio of bore and leakage flows. Once the leakage flow was increased above a certain threshold, the flow structure is shown to transition from a classical Batchelor-type rotor-stator system to a vortex-dominated structure. The existence of a toroidal vortex immediately inboard of the outer rim-seal is shown to encourage ingestion.

Synthetic colloid fluids (6% hydroxyethyl starch 130/0.4 and 4% succinylated gelatin) interfere with total plasma protein measurements in vitro.

High molecular weight (MW) synthetic colloids interfere with refractometry. The effect of low MW synthetic colloids on refractometry is unknown. To investigate the effect of 6% hydroxyethyl starch 130/0.4 (HES) and 4% succinylated gelatin (GELO) on the refractometric measurement of total plasma protein (TPP) and colloid osmotic pressure (COP) in canine plasma. Heparinized plasma from 10 dogs was diluted with 0.9% saline (NaCl), HES, and GELO in ratios of plasma:fluid, 9:1, 8:2, 7:3, 6:4, and 5:5. The biuret TPP (TPPb), refractometric TPP (TPPr), and COP assays were performed for all dilutions. Agreement (bias, 95% limits of agreement (LOA)) was tested between the TPPb (NaCl) and the TPPr of the NaCl, HES, and GELO plasma dilutions, and between the TPPb (NaCl) and the TPPb of the HES and GELO plasma dilutions. A small bias (0.06 g/dL, 95% LOA -0.51 to 0.39 g/dL) existed between TPPb (NaCl) and TPPr (NaCl). A large bias was found between TPPb (NaCl) and TPPr (HES) (1.38 g/dL, 95% LOA 0.30 to 3.10 g/dL), and TPPr (GELO) (1.18 g/dL, 95% LOA 0.53 to 2.88 g/dL). A small bias was found between TPPb (NaCl) and TPPb (HES) (0.08 g/dL, 95% LOA -2.04 to 2.20 g/dL), and a large bias was found between TPPb (NaCl) and TPPb (GELO) (1.00 g/dL, 95% LOA -0.59 to 2.60 g/dL). Increasing overestimation of TPPb (NaCl) by TPPr (HES and GELO) and TPPb (GELO) occurred with increasing colloid volumes. HES and GELO interfered with TPPr, and GELO also interfered with TPPb, in vitro. These variables should be interpreted with caution for dogs that have received these synthetic colloids.

Experimental evidence of non-ideal compressible effects in expanding flow of a high molecular complexity vapor

Supersonic expansions of a molecularly complex vapor occurring within the non-ideal thermodynamic region in the close proximity of liquid-vapor saturation curve were characterized experimentally for the first time. Results for two planar converging–diverging nozzles in the adapted regime and at different inlet conditions, from highly non-ideal to dilute gas state, are reported. Measurements of upstream total pressure and temperature are performed in the plenum ahead of the nozzle, while static pressure and supersonic Mach number measurements are carried out along the nozzle centerline. The investigated expansions are of interest for both fundamental research on non-ideal compressible flows and industrial applications, especially in the energy field. Siloxane MDM (octamethyltrisiloxane, text {C}_8text {H}_{24}text {O}_2text {Si}_3), a high molecular complexity organic compound, is used. Local pressure ratio P/P_mathrm{T} and Mach number M measurements display a dependence on the inlet total state, a typical non-ideal feature different from dilute gas conditions.

Turbulent structure in supersonic jets with a high Reynolds number

The turbulent properties of a supersonic jet were studied related to a high level of pressure pulsation found in model jets of a reentry flight vehicle approaching the landing ground. This study comprised measurements of total pressure at a small-size target using a dynamic pressure probe placed in a free jet. The most comprehensive data about jet turbulence can be obtained by direct transformation of the pressure reading at the stagnation point near the target into the normalized velocity. The oscillogram of normalized velocity produces the velocity average value, root-mean-square value as well as turbulence intensity and turbulence spectrum. It was demonstrated that a high level of turbulence for a high-head jet retains along the supersonic core length and at the beginning of subsonic interval.

Experimental characterization of the transonic test section flow in a Ludwieg tube

A new Ludwieg tube for transonic testing has been put into operation. For this, an existing shock tube has been modified to a Ludwieg tube. The ideal operating principle is described by theory and corresponding theoretical values are compared to experimental ones. Pressure histories as well as test section flow visualization demonstrate a better performance concerning flow quality and testing time compared to the former shock tube. Static as well as total pressure measurements have been performed within the test section. Pitot rake measurements show the homogeneity of the test section flow field. Additional boundary layer profile measurements give evidence of the temporal growth of the test section wall boundary layer. These results are compared with theoretical ones deduced from a theoretical approach for a boundary layer behind an expansion wave. Both, boundary layer and Pitot rake measurements allow to discuss the influence of a turbulent boundary layer on these measurements. Cookie cutters at the entrance to the test section act as boundary layer bleed which partially avoid the entering of the tube wall boundary layer into the test section. Their influence on the test section flow is discussed as well.

Entwicklung der Quadrupol‐Massenspektrometer in den letzten 30 Jahren

SummaryThe quest to determine the composition of gasThis article examines developments in quadrupole mass spectrometers over the past 30 years. It looks into the changing footprint of devices as well as at software and communication interfaces. It also introduces the advantages of modern compact devices, such as improved detection limits, integrated total pressure measurement and multiple interfaces. The outlook discusses the potential further development of operating software that may be replaced by a web application and the continuing miniaturization of devices.

Intrusive measurements of air-water flow properties in highly turbulent supported plunging jets and effects of inflow jet conditions

A plunging jet is an efficient device to entrain gas into liquid flow. In many practical occasions, the gas entrainment needs to be carefully controlled, and the interaction between the shear flow turbulence and entrained bubbles has to be better understood. This paper presents a physical study of vertical supported two-dimensional plunging jets using a relatively large-size facility. The air-water flow and turbulence properties were measured with an intrusive phase-detection probe and a total pressure sensor simultaneously. The inflow pre-aeration and turbulence level of the falling jet were carefully characterised, and the effects of jet impact velocity and jet length on air entrainment in plunging pool were investigated. The experimental results were systematically compared to relevant studies. A discussion was developed on the quantification of turbulence intensity in highly-aerated flow based on total pressure measurement. The flow turbulence properties were derived respectively from the interfacial phase-detection signals and total pressure signals. The results highlighted difference in terms of the turbulence intensities between interfacial motions and water-phase turbulence. The present work showed that the jet impact velocity, jet length, inflow disturbance and pre-entrainment of air had considerable effects on air entrainment capacity and subsurface air-water flow properties in plunging jets hence should be carefully characterised in relevant studies.

Influence of Backward- and Forward-Facing Steps on the Flow Through a Turning Mid Turbine Frame

For this work, reality effects, more precisely backward-facing steps (BFSs) and forward-facing steps (FFSs), and their influence on the flow through a two-stage two-spool turbine rig under engine-relevant conditions were experimentally investigated. The test rig consists of an high pressure (HP) and an low pressure (LP) stage, with the two rotors rotating in opposite direction with two different rotational speeds. An S-shaped transition duct, which is equipped with turning struts (so-called turning mid turbine frame (TMTF)) and making therefore a LP stator redundant, connects both stages and leads the flow from a smaller to a larger diameter. This test setup allows the investigation of a TMTF deformation, which occurs in a real aero-engine due to non-uniform warming of the duct during operation—especially during run up—and causes BFSs and FFSs in the flow path. This happens for nonsegmented ducts, which are predominantly part of smaller engines. In the case of the test rig, steps were not generated by varying temperature but by shifting the TMTF in horizontal direction while the rotor and its casing were kept in the same position. In this way, both BFSs and FFSs between duct endwalls and rotor casing could be created. In order to avoid steps further downstream of the interface between HP rotor and TMTF, the complete aft rig was moved laterally too. In this case, the aft rig incorporates among others the LP rotor, the LP rotor casing, and the deswirler downstream of the LP stage. In order to catch the influence of the steps on the whole flow field, 360 deg rake traverses were performed downstream of the HP rotor, downstream of the duct, and downstream of the LP rotor with newly designed, laser-sintered combi-rakes for the measurement of total pressure and total temperature. Only the compact design of the rakes, which can be easily realized by additive manufacturing, makes the aforementioned 360 deg traverses in this test rig possible and allows a number of radial measurements positions, which is comparable to those of a five-hole probe. To get a more detailed information about the flow, also five-hole probe measurements were carried out in three measurement planes and compared to the results of the combi-rakes.

Turbulent velocity and pressure fluctuations in gas turbine combustor exit flows

This paper presents the results of two test programmes using novel instrumentation to characterise the pressure and turbulent velocity fields in gas-turbine combustor exit flows. The probes are uncooled, therefore a fast-insertion traverse system is employed to prevent thermal degradation of the instrumentation in these severely hostile high-temperature environments. High-bandwidth ultra-miniature pressure transducers are used to measure unsteady total pressure, whilst a Pitot tube is employed to measure time-averaged total pressure. The probes are 4 mm in diameter with a measurement bandwidth of the order of 100 kHz. In the first test programme, the probes are used to characterise the streamwise turbulent velocity field approximately two axial chords downstream of an uncooled single-stage turbine in a turbojet engine. Established data reduction methods and calibration against a hot-wire are used to obtain turbulent velocity fluctuations from unsteady total pressure measurements. Comprehensive turbulence results are presented including time-histories, power spectra, intensities, and lengthscales obtained at four-engine conditions and at two radial and two circumferential measurement locations. In the second test programme the probes are demonstrated in an industrial combustor rig, featuring a can combustor with swirler nozzle and no dilution holes, at temperatures up to 1500 K. Static pressure fluctuations are obtained up to 100 kHz, and some typical combustor spectral features are identified.

An improved apparatus for vapour–liquid equilibria measurement in polymer + solvent systems at higher temperatures: A study of the water + poly(ethylene glycol) system

Recently we designed an apparatus for total pressure measurement in binary polymer + solvent systems. Accurate as it is, the apparatus is limited by its direct capacitance pressure sensor that can operate only at 318.15 K. In this study we tested a new setup that overcomes this limitation with a pressure transducer (MKS Baratron), which can be heated up to 430 K. The main improvement is that the new setup has eliminated solvent vapour condensation in the pressure measurement unit. Other parts of the equipment can easily be kept at temperatures higher than the system temperature with heating tapes. Unlike the ebulliometric method, which is limited by problems arising from the boiling of viscous mixtures, now we can study solutions with higher polymer concentrations. We tested the new setup by measuring the total pressure of binary poly(ethylene glycol) + water mixtures at six isotherms in the (308.15–343.15) K range. Additionally we determined new data for three isotherms (343.15, 353.15, and 363.15) K using ebulliometric method. We then correlated our measurements with both methods using the UNIQUAC–free volume model and compared them with available published data for isotherms 313.15 K and 333.15 K. The agreement with our static measurement results was excellent.