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Showing papers on "Pressure measurement published in 2014"


Journal ArticleDOI
TL;DR: A sub-micron silica diaphragm-based fiber-tip Fabry-Perot interferometer for pressure sensing applications is demonstrated, with a high pressure sensitivity and low temperature cross-sensitivity, suitable for high sensitivity pressure sensing in harsh environments.
Abstract: We demonstrate a sub-micron silica diaphragm-based fiber-tip Fabry–Perot interferometer for pressure sensing applications. The thinnest silica diaphragm, with a thickness of ∼320 nm, has been achieved by use of an improved electrical arc discharge technique. Such a sub-micron silica diaphragm breaks the sensitivity limitation imposed by traditional all-silica Fabry–Perot interferometric pressure sensors and, as a result, a high pressure sensitivity of ∼1036 pm/MPa at 1550 nm and a low temperature cross-sensitivity of ∼960 Pa/°C are achieved when a silica diaphragm of ∼500 nm in thickness is used. Moreover, the all-silica spherical structure enhanced the mechanical strength of the micro-cavity sensor, making it suitable for high sensitivity pressure sensing in harsh environments.

173 citations


Journal ArticleDOI
TL;DR: In this paper, an experimental study carried out to better understand the wind pressure distribution on stand-alone panel surfaces and panels attached to flat building roofs was carried out at a 1:200 geometric scale.

88 citations


Journal ArticleDOI
TL;DR: In this paper, the pressure measurement subsystem of the Mars Science Laboratory (MSL) Rover Environmental Measurement Station (REMS-P) performed accurate observations of the Martian atmospheric surface pressure.
Abstract: [1] REMS-P, the pressure measurement subsystem of the Mars Science Laboratory (MSL) Rover Environmental Measurement Station (REMS), is performing accurate observations of the Martian atmospheric surface pressure. It has demonstrated high data quality and good temporal coverage, carrying out the first in situ pressure observations in the Martian equatorial regions. We describe the REMS-P initial results by MSL mission sol 100 including the instrument performance and data quality and illustrate some initial interpretations of the observed features. The observations show both expected and new phenomena at various spatial and temporal scales, e.g., the gradually increasing pressure due to the advancing Martian season signals from the diurnal tides as well as various local atmospheric phenomena and thermal vortices. Among the unexpected new phenomena discovered in the pressure data are a small regular pressure drop at every sol and pressure oscillations occurring in the early evening. We look forward to continued high-quality observations by REMS-P, extending the data set to reveal characteristics of seasonal variations and improved insights into regional and local phenomena.

87 citations


Journal ArticleDOI
TL;DR: In this article, a dual-cavity Fabry-Perot sensor for simultaneous pressure and temperature measurements is presented, which consists of an UV-molded cavity covered by a metal/polymer composite diaphragm for achieving a high pressure sensitivity while maintaining a miniature sensor size.
Abstract: We present a novel hybrid miniature dual-cavity Fabry-Perot sensor for simultaneous pressure and temperature measurements. The pressure sensing cavity is composed of an UV-molded cavity covered by a metal/polymer composite diaphragm for achieving a high pressure sensitivity while maintaining a miniature sensor size. Another intrinsic polymer/silica cavity is adopted for temperature sensing, which enables a high temperature sensitivity even with a short cavity length due to the large thermal expansion of the polymer. The sensor is fabricated by using a unique UV molding process with simple and safe procedures. The overall sensor size is around 150 μm in diameter and 343 μm in length. Experimental studies show that the sensor exhibits a good linearity over a pressure range of 6.89 to 27.58 kPa with a pressure sensitivity of 0.0122 μm/kPa at 26 °C, and a temperature range of 26.0 °C to 50.0 °C with a temperature sensitivity of 0.0029 μm/°C. An optical signal processing method is developed to retrieve the two cavity length changes, which is demonstrated to have a better resolution and a faster speed than the conventional method. The sensor is expected to benefit many fronts that require simultaneous pressure and temperature measurements with minimum intrusiveness, especially for biomedical applications.

81 citations


Journal ArticleDOI
TL;DR: In this paper, the authors focused on the pressure variations in a high-head Francis turbine during the transients and found that the largest pressure variation was observed during partial load rejection at the trailing edge of the blade.
Abstract: Hydraulic turbines are frequently used to maintain electrical grid parameters. An angular movement of the guide vanes (GVs) during transients such as load acceptance and rejection within short time raised significant concerns for increased wear and instabilities. The present work focuses on the pressure variations in a high-head Francis turbine during the transients. Six transient conditions were investigated including time-domain rotor–stator interaction. The measurements in the vaneless space and runner indicated the presence of unsteady vortical flow during transients. The vortices travelled to the runner and affected the flow in the blade channels. The GVs angular movement increases the pressure difference between the pressure and suction sides of the blade. The largest pressure variation was observed during the partial load rejection at the trailing edge of the blade. Preliminary results indicated that an appropriate closure of the GVs may minimize large pressure fluctuations in the runner.

69 citations


Journal ArticleDOI
TL;DR: The performance of the HPTSS indicates that it could be an ideal candidate for high-pressure and high-temperature sensing in real application and the structure and configuration of the sensor chip are analyzed theoretically and simulated by the finite element method.
Abstract: This paper describes a design method for optimizing sensitivity of piezoresistive pressure sensor in high-pressure and high-temperature environment. In order to prove the method, a piezoresistive pressure sensor (HPTSS) is designed. With the purpose of increasing sensitivity and to improve the measurement range, the piezoresistive sensor adopts rectangular membrane and thick film structure. The configuration of piezoresistors is arranged according to the characteristic of the rectangular membrane. The structure and configuration of the sensor chip are analyzed theoretically and simulated by the finite element method. This design enables the sensor chip to operate in high pressure condition (such as 150 MPa) with a high sensitivity and accuracy. The silicon on insulator wafer is selected to guarantee the thermo stability of the sensor chip. In order to optimize the fabrication and improve the yield of production, an electric conduction step is devised. Series of experiments demonstrates a favorable linearity of 0.13% and a high accuracy of 0.48%. And the sensitivity of HTPSS is about six times as high as a conventional square-membrane sensor chip in the experiment. Compared with the square-membrane pressure sensor and current production, the strength of HPTTS lies in sensitivity and measurement. The performance of the HPTSS indicates that it could be an ideal candidate for high-pressure and high-temperature sensing in real application.

69 citations


Journal ArticleDOI
08 Jul 2014-Sensors
TL;DR: The experimental results demonstrate that the proposed smart temperature compensation system is valid for the temperature compensation and high accuracy requirement of the sensor.
Abstract: Theoretical analysis in this paper indicates that the accuracy of a silicon piezoresistive pressure sensor is mainly affected by thermal drift, and varies nonlinearly with the temperature. Here, a smart temperature compensation system to reduce its effect on accuracy is proposed. Firstly, an effective conditioning circuit for signal processing and data acquisition is designed. The hardware to implement the system is fabricated. Then, a program is developed on LabVIEW which incorporates an extreme learning machine (ELM) as the calibration algorithm for the pressure drift. The implementation of the algorithm was ported to a micro-control unit (MCU) after calibration in the computer. Practical pressure measurement experiments are carried out to verify the system’s performance. The temperature compensation is solved in the interval from −40 to 85 °C. The compensated sensor is aimed at providing pressure measurement in oil-gas pipelines. Compared with other algorithms, ELM acquires higher accuracy and is more suitable for batch compensation because of its higher generalization and faster learning speed. The accuracy, linearity, zero temperature coefficient and sensitivity temperature coefficient of the tested sensor are 2.57% FS, 2.49% FS, 8.1 × 10−5/°C and 29.5 × 10−5/°C before compensation, and are improved to 0.13%FS, 0.15%FS, 1.17 × 10−5/°C and 2.1 × 10−5/°C respectively, after compensation. The experimental results demonstrate that the proposed system is valid for the temperature compensation and high accuracy requirement of the sensor.

68 citations


Journal ArticleDOI
TL;DR: In this paper, a new method for the identification of flow regime in vertical upward gas-liquid flows has been proposed, which consists of an application of the elastic maps algorithm, which is a machine learning method, to the probability density function of differential pressure measurements in pipes.

65 citations


Journal ArticleDOI
TL;DR: A flexible capacitive tactile sensor with adjustable characteristics, i.e., measurement range and sensitivity, has been developed in this paper, where polydimethylsiloxane (PDMS) material is selected as the material of the dielectric layer between the parallel plate electrodes of the sensor.
Abstract: A flexible capacitive tactile sensor with adjustable characteristics, i.e., measurement range and sensitivity, has been developed. The proposed sensor is designed for large pressure measurement; therefore, polydimethylsiloxane (PDMS) material is selected as the material of the dielectric layer between the parallel plate electrodes of the sensor. Since the elasticity of the PDMS material can be adjusted by the mixing ratio of PDMS pre-polymer and curing agent during formation, sensors in different measurement ranges, i.e., 240–1,000 and 400–3,000 kPa, and corresponding sensitivities, i.e., 2.24 and 0.28 %/MPa, were respectively constructed and demonstrated. These measurement ranges are suitable for most of the biomechanical applications, especially for plantar pressure measurement. Moreover, because the output of the sensor, i.e., capacitance, is highly influenced by the dimension of the sensor structure, each sensor consists of four independent capacitance elements. The output of each sensor is averaged by four capacitances for single force measurement. This could improve the measurement accuracy in practical situation. Also, linearity of the measurement response could be enhanced and it was shown by the R-squared values in two measurement ranges, i.e., 0.9751 and 0.9881, respectively. The proposed sensor is flexible and miniaturized and has the potential to be applied to biomechanical applications.

61 citations


Journal ArticleDOI
TL;DR: In this article, a new approach of mathematical correlations performance of thermal vapor compressor (TVC) is presented, where the results of the mathematical model of TVC mixing ratios and performance diagram are very close approach to the Power's lines.

56 citations


Journal ArticleDOI
TL;DR: A micromachining process based on selective chemical etching of specially designed phosphorus-doped fibers, and a sequence of splice and cleave steps were used to fabricate the sensor.
Abstract: This Letter presents a fiber-optic sensor created at the tip of an optical fiber for simultaneous measurements of pressure and refractive index. The sensor diameter does not exceed the standard fiber diameter and is shorter than 300 μm. Measurement resolutions of 0.2 mbar and 2×10−5 RIU were demonstrated experimentally by using spectral interrogation and Fourier-transform-based measurement algorithms (interrogation system bandwidth corresponded to 1 Hz). A micromachining process based on selective chemical etching of specially designed phosphorus-doped fibers, and a sequence of splice and cleave steps were used to fabricate the sensor.

Journal ArticleDOI
TL;DR: Catheter geometry produces significant measurement bias in both the peak pressure and the waveform shape even with radius ratios considered acceptable in clinical practice, showing that the wire allows for more accurate pressure quantification, in agreement with the numerical model without a catheter.
Abstract: Accurate measurement of blood pressure is important because it is a biomarker for cardiovascular disease. Diagnostic catheterization is routinely used for pressure acquisition in vessels despite being subject to significant measurement errors. To investigate these errors, this study compares pressure measurement using two different techniques in vitro and numerical simulations. Pressure was acquired in a pulsatile flow phantom using a 6F fluid-filled catheter and a 0.014′′ pressure wire, which is considered the current gold standard. Numerical simulations of the experimental set-up with and without a catheter were also performed. Despite the low catheter-to-vessel radius ratio, the catheter traces showed a 24% peak systolic pressure overestimation compared to the wire. The numerical models replicated this difference and indicated the cause for overestimation was the increased flow resistance due to the presence of the catheter. Further, the higher frequency pressure oscillations observed in the wire and numerical data were absent in the catheter, resulting in an overestimation of the pulse wave velocity with the latter modality. These results show that catheter geometry produces significant measurement bias in both the peak pressure and the waveform shape even with radius ratios considered acceptable in clinical practice. The wire allows for more accurate pressure quantification, in agreement with the numerical model without a catheter.

Journal ArticleDOI
TL;DR: In this paper, the impact of hydrostatic pressure (0-1.97 GPa) on superconductivity of recently discovered 2 K superconductor Sr0.5La 0.5FBiS2 was reported.
Abstract: We report the impact of hydrostatic pressure (0–1.97 GPa) on superconductivity of recently discovered 2 K superconductor Sr0.5La0.5FBiS2. Resistivity under pressure measurements are performed by using HPC-33 Piston type pressure cell with Quantum design DC resistivity Option. The superconducting transition temperature (Tc) is increased by 5 fold to around 10 K with just above 1 GPa pressure, which remains nearly unaltered for studied higher pressures of up to 1.97 GPa. The fivefold increase in Tc accompanied with decrease in normal state resistivity of Sr0.5La0.5FBiS2 with just above 1 GPa pressure calls for the attention of solid state physics community.

Proceedings ArticleDOI
23 Apr 2014
TL;DR: A Bluetooth Low Energy (BLE) based blood pressure monitoring system, which integrated a homemade blood pressure measuring device and a smartphone, which has high accuracy for measuring blood pressure and pulse rate.
Abstract: In this paper, we successfully developed a Bluetooth Low Energy (BLE) based blood pressure monitoring system, which integrated a homemade blood pressure measuring device and a smartphone. The device uses single BLE System-on-Chip to process the algorithm of blood pressure measurement and data transmission. Through the newest Bluetooth Low Energy technology, device can send measured results to the smartphone. Therefore, users can get the information of systolic blood pressure, diastolic blood pressure and pulse rate on the smartphone. Besides, the format of data transmission packet is based on the standard Blood Pressure Profile specification from Bluetooth SIG. The homemade blood pressure monitor has high compatibility to communication with other devices using the same Bluetooth profile. The accuracy of pulse rate and blood pressures are verified through the CuffLink simulator. The accuracy of pulse rate is −1.13 ± 0.52 beats, the accuracy of systolic blood pressure is 0.69 ± 1.63 mmHg, and the accuracy of diastolic blood pressure is 0.20 ± 1.02 mmHg. In clinical trials, the systolic blood pressure average difference between our method and auscultatory method is 2.66 ± 2.71 mmHg. The diastolic blood pressure average difference between our method and auscultatory method is 3.42 ± 4.42 mmHg. As a result, this device has high accuracy for measuring blood pressure and pulse rate.

Journal ArticleDOI
TL;DR: In this paper, high-resolution neutron-diffraction experiments were performed on elemental lead as functions of both temperature (80-298 K) and applied pressure (up to 8.9 GPa), with the pressure values derived from the NaCl pressure gauge.
Abstract: From high-resolution neutron-diffraction experiments we present equation-of-state (EOS) data of elemental lead as functions of both temperature (80-298 K) and applied pressure (up to 8.9 GPa), with the pressure values derived from the NaCl pressure gauge. Based on Brown's 1999 NaCl EOS we find the bulk modulus of lead of B-0 = 41.2(2) GPa at 298 K to increase by 14% to B-0 = 47.0(5) GPa by 80 K. The ambient temperature value coincides within 0.35 GPa (1.7%) of the value determined from published ultrasonic data. The good agreement between the neutron and ultrasonic data deteriorates if pressure values are derived from Decker's 1971 scale. Our results hence lend significant support to Brown's revised NaCl pressure standard. Furthermore, the experimental results are compared with T = 0 K first-principles calculations.

Journal ArticleDOI
TL;DR: In this paper, a spatiotemporal description of the gas number densities of major species including O atoms, the hydrodynamic expansion and the relative distribution of the energy deposited in the specific molecular modes of N2(X) and O2 (X) following a nanosecond pulsed air discharge at atmospheric pressure is presented.
Abstract: The better understanding of nanosecond scale discharges under atmospheric pressure and the validation of plasmachemical models, require an increasing need for reliable data. This paper presents, in the first time to our knowledge, spatiotemporal description of the gas number densities of major species including O atoms, the hydrodynamic expansion and the relative distribution of the energy deposited in the specific molecular modes of N2(X) and O2(X) following a nanosecond pulsed air discharge at atmospheric pressure. These data are obtained from phase-locked average profiles of the ground states of N2 and O2 probed by spontaneous Raman scattering. The results complete part I of this investigation dedicated to the gas temperature and the vibrational distribution function of N2 and O2 and show that half of the total energy deposited is loaded on the vibrational mode (48% for N2 and 2% for O2). The energy released into fast gas heating represents 19% of the energy deposited. This fast gas heating (up to 1000 K) observed in tens of nanoseconds after the current rise leads to a shock wave propagation shown with the pressure measurements. These processes combined with vibration–vibration/translation energy transfers and convective transports induced by the shock wave propagation are spatiotemporally studied. The experimental data of this study provide space and time database for the validation of plasmachemical models of nanosecond pulsed discharges in atmospheric pressure air.

Journal ArticleDOI
TL;DR: In this article, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out.
Abstract: In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm–50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of −50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

Journal ArticleDOI
Ke Xu1, Chris P. Tostado1, Jianhong Xu1, Yangcheng Lu1, Guangsheng Luo1 
TL;DR: The gauge was used to monitor the drop formation and breakup process in a co-flow junction microfluidic device under different flow conditions across a large range of capillary numbers and was also used to clearly identify a transition between the dripping and jetting flow regimes.
Abstract: In this study, we developed a new method for the direct measurement of differential pressures in a co-flow junction microfluidic device using a Capillary Laplace Gauge (CLG). The CLG – used inside the microchannel device – was designed using a tapered glass-capillary set up in co-flow junction architecture with a three-phase liquid–liquid–gas system with two flowing liquid phases and an entrained gas phase. By taking advantage of the Laplace equation, basic geometric relations and an integrated image analysis program, the movement of the entrained gas phase with the flow of the liquid-phases is tracked and monitored, allowing the gauge to function as an ultra-sensitive, integrated, differential pressure sensor measuring fluctuations in the liquid-dispersed phase channel pressure as small as tens of Pascals caused by droplet formation. The gauge was used to monitor the drop formation and breakup process in a co-flow junction microfluidic device under different flow conditions across a large range (1 × 10−3 to 2.0 × 10−1) of capillary numbers. In addition to being able to monitor short and long term dispersed phase pressure fluctuation trends for both single drop and large droplet populations, the gauge was also used to clearly identify a transition between the dripping and jetting flow regimes. Overall, the combination of a unique, integrated image analysis program with this new type of sensor serves as a powerful tool with great potential for a variety of different research and industrial applications requiring sensitive microchannel pressure measurements.

Book ChapterDOI
01 Jan 2014
TL;DR: Microwave vacuum drying is a dehydration process that uses microwave radiation to generate heat in the absolute pressure (chamber pressure) range from above the triple point of water to less than atmospheric pressure (0.61-101.33 kPa) as discussed by the authors.
Abstract: The potential of microwave energy combined with a vacuum environment for rapid low temperature dehydration that produces high quality products has long been recognized. Microwave vacuum drying is a dehydration process that uses microwave radiation to generate heat in the absolute pressure (chamber pressure) range from above the triple point of water to less than atmospheric pressure (0.61–101.33 kPa). The earliest related applications involved using a combination of radio frequency energy and vacuum. Potatoes and cabbage were reported to be rapidly dehydrated using this technique, and penicillin was dried using radio frequency energy (28 MHz) in combination with a vacuum to prevent the thermal degradation of the antibiotic. While the radiation used in these applications was below microwave frequency, these examples embody the concept of converting electromagnetic energy to heat inside a material rather than relying on conduction and convection for heat transfer and of using vacuum to maintain a low product temperature, resulting in improved product quality.

Journal ArticleDOI
TL;DR: In this article, a capacitive absolute pressure sensor whose pressure sensitive membrane is formed by the silicon on nothing (SON) structure was fabricated and evaluated, and the average sensitivity of the sensor array with 15 diaphragms is 2.88 fF/kPa.
Abstract: In the field of silicon on nothing (SON) structure , micrometer-thick monocrystalline layers suspended over their parent wafer were produced by high-temperature annealing of specific arrays of trenches. Those trenches reorganize into one single void and leave a thin overlayer on top. Since this method may be an easy way of synchronous fabricating high-quality silicon films and vacuum void, this paper investigates its potential applications for a pressure sensor. A capacitive absolute pressure sensor whose pressure sensitive membrane is formed by the SON structure was fabricated and evaluated. The radius and thickness of the sensitive membrane are 100 and 1.7-μm, respectively. The average sensitivity of the sensor array with 15 diaphragms is 2.88 fF/kPa. This novel fabrication process enables to easily form a high vacuum cavity without hermetical sealing process such as anodic bonding technology, to achieve an excellent long-term stability and reliability, in particular, and to easily integrate detection circuits with the sensor.

Journal ArticleDOI
TL;DR: In this article, a wind tunnel experiment for the evaluation of energy performance and aerodynamic forces acting on a small straight-bladed vertical axis wind turbine (VAWT) depending on several values of tip speed ratio was presented.
Abstract: This paper presents a wind tunnel experiment for the evaluation of energy performance and aerodynamic forces acting on a small straight-bladed vertical axis wind turbine (VAWT) depending on several values of tip speed ratio. In the present study, the wind turbine is a four-bladed VAWT. The test airfoil of blade is symmetry airfoil (NACA0021) with 32 pressure ports used for the pressure measurements on blade surface. Based on the pressure distributions which are acted on the surface of rotor blade measured during rotation by multiport pressure-scanner mounted on a hub, the power, tangential force, lift and drag coefficients which are obtained by pressure distribution are discussed as a function of azimuthally position. And then, the loads which are applied to the entire wind turbine are compared with the experiment data of pressure distribution. As a result, it is clarified that aerodynamic forces take maximum value when the blade is moving to upstream side, and become small and smooth at downstream side. The power and torque coefficients which are based on the pressure distribution are larger than that by torque meter.

Journal ArticleDOI
TL;DR: In this paper, a sensitivity-enhanced fiber-optic pressure sensor using a simplified hollow-core photonic crystal fiber (SHC-PCF) is presented. But the sensing head is fabricated by splicing a single mode fiber to a section of SHC-pcF, while the air claddings at the end of the PCF are selectively blocked by glue sealing and femtosecond laser machining.
Abstract: We experimentally demonstrate a sensitivity-enhanced fiber-optic pressure sensor using a simplified hollow-core photonic crystal fiber (SHC-PCF). The sensing head is fabricated by splicing a single mode fiber to a section of SHC-PCF, while the air claddings at the end of the PCF are selectively blocked by glue sealing and femtosecond laser machining. By immersing the end into water, a compressible Fabry-Perot cavity can be formed in the fiber core of the PCF. Since the air core is opened up to the air claddings at the splicing joint, changing of environmental pressure will cost a large change of the cavity length to balance the pressure, which greatly enhances the pressure sensitivity of the sensor. A pressure sensitivity of 18.15 $\mu$ m/kPa is experimentally demonstrated in the pressure range from 110 to 130 kPa. This sensor has potential applications in the area of highly sensitive pressure measurement.

Proceedings ArticleDOI
13 Jan 2014
TL;DR: In this paper, a 30° swept-wing model with a movable, leading-edge extending to 15% chord is used in low-disturbance wind-tunnel tests to study the effect of two-dimensional, step excrescences in a three-dimensional boundary layer.
Abstract: A 30° swept-wing model with a movable, leading-edge extending to 15% chord is used in low-disturbance wind-tunnel tests to study the effect of two-dimensional, step excrescences in a three-dimensional boundary layer. Forwardand aft-facing steps are modulated during the tests. Pressure measurements are compared with computational results, infrared thermography is used to globally detect boundary-layer transition, and hotwire measurements provide details of the boundary-layer profiles in the vicinity of the steps. An analysis of the results is provided including data from tests in a flight environment and from experimental studies of an unswept model of equivalent 2-D pressure gradient.

Journal ArticleDOI
TL;DR: A fiber optic sensing system for pressure measurement in invasive urodynamics is presented and experimentally validated, showing the premises for an EFPI-based diagnostic tool.
Abstract: A fiber optic sensing system for pressure measurement in invasive urodynamics is presented and experimentally validated. Probes are based on extrinsic Fabry–Perot interferometry (EFPI) principle, with an all-glass biocompatible design having 0.2-mm thickness. Pressure sensitivity of 1.0–1.6 nm/kPa with high stability and reduced thermal sensitivity has been achieved, leading to $0.3\hbox{-}{\rm cmH}_{2}{\rm O}$ pressure accuracy. The EFPI probes have been embedded in medical catheters with 4F size for dual bladder and abdominal pressure measurement throughout the full course of a urodynamic analysis. Pressure traces have been compared with a PICO2000 urodynamic instrument, showing improved accuracy and higher responsivity to local pressure variations. Tests have been carried out in vivo on seven patients; the main highlights are reported, showing the premises for an EFPI-based diagnostic tool.

Journal ArticleDOI
TL;DR: In this paper, the authors present results of an experimental investigation of the visible flame propagation and pressure measurements in 4mm extension tubes of up to 1m length attached to a bulk vessel by a rupture disc.

Journal ArticleDOI
07 May 2014
TL;DR: In this paper, an air-driven shock tube with Mylar® and aluminium diaphragms of various thicknesses was used for high-speed photography and pressure measurements of biological specimens.
Abstract: The shock tube is a versatile apparatus used in a wide range of scientific research fields. In this case, we are developing a system to use with biological specimens. The process of diaphragm rupture is closely linked to the shock wave generated. Experiments were performed on an air-driven shock tube with Mylar® and aluminium diaphragms of various thicknesses, to control the output. The evolution of shock pressure was measured and the diaphragm rupture process investigated. Single-diaphragm and double-diaphragm configurations were employed, as were open or closed tube configurations. The arrangement was designed to enable high-speed photography and pressure measurements. Overall, results are highly reproducible, and show that the double-diaphragm system enables a more controllable diaphragm burst pressure. The diaphragm burst pressure was linearly related to its thickness within the range studied. The observed relationship between the diaphragm burst pressure and the generated shock pressure presents a noticeable difference compared to the theoretical ideal gas description. Furthermore, the duration of the primary shock decreased proportionally with the length of the high-pressure charging volume. Computational modelling of the diaphragm breakage process was carried out using the ANSYS software package.

Journal ArticleDOI
TL;DR: The experimental results have been compared with the existing unified Model and a good agreement has been noticed and the pressure gradients have been found to increase with the increase in gas flow rates.
Abstract: An experimental investigation has been carried out to study the flow regimes and pressure gradients of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and pressure gradients have been studied. The experiments have been conducted at 20°C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The pressure gradients have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the pressure gradients increased with the increase in the superficial liquid velocity. The pressure gradient first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.

Journal ArticleDOI
01 Mar 2014
TL;DR: In this article, the decelerated swirling flow in the draft tube cone of hydraulic turbines is responsible for self-induced instabilities which generates pressure pulsations that hinder the turbine operation.
Abstract: The decelerated swirling flow in the draft tube cone of hydraulic turbines (especially turbines with fixed blades) is responsible for self-induced instabilities which generates pressure pulsations that hinder the turbine operation. An experimental test rig was developed in order to investigate the flow instabilities. A new method was implemented to slow down the runner using a magneto rheological brake in order to be extended the flow regimes investigated. As a result, the experimental investigations are performed for 7 operating regimes in order to quantify the flow behaviour from part load operation to overload operation. The unsteady pressure measurements are carried out on 4 levels in the cone. The unsteady pressure measurements on the cone wall consist in quantifying of three aspects: i) the pressure recovery coefficient obtained based on mean pressure provides the energetic assessment on the draft tube cone; ii) the unsteady quantities (dominant amplitude and frequency) are determined revealing the dynamic behaviour; iii) the plunging and rotating components of the pressure pulsation. As a result, this new method helps us to investigate in detail the flow instability for different operating regimes and allows investigating various flow control solutions.

Journal ArticleDOI
TL;DR: The double threshold method realized by hardware circuits and high performance timing chip TDC-GP21 was successfully adapted to solve the key problem of ultrasonic distance measurement, the accurate time-of-flight (TOF) measurement of ultrasonic wave.
Abstract: The double threshold method realized by hardware circuits and high performance timing chip TDC-GP21 was successfully adapted to solve the key problem of ultrasonic distance measurement, the accurate time-of-flight (TOF) measurement of ultrasonic wave. Compared with other techniques of TOF measurement, the double threshold method presented in this work can suppress noise in the received signal, and achieve a time resolution of around 22 ps and real-time. This method is easy to realize and pertains the advantage of low cost. To compensate temperature and pressure deviations, a temperature measurement module of 10 mK in precision as well as a pressure measurement module of 0.01% in accuracy was developed. The system designed in this work can be exactly used as a two paths ultrasonic gas flowmeter without any adjustment of the hardware circuit. The double threshold method was further corroborated using experiment results of both the ultrasonic distance measurement and ultrasonic gas flow measurement. In distance measurement, the maximum absolute deviation and the maximum relative error are 0.69 mm and 0.28%, respectively, for a target distance range of 100–600 mm. In flow measurement, the maximum absolute deviation and the worst repeatability are 1.16% and 0.65% for a flow in the range of 50–700 m3/h.

Journal ArticleDOI
TL;DR: In this paper, the total pressure and air-water flow properties were measured simultaneously with intrusive probes, namely a miniature pressure transducer and a dual-tip phase-detection probe, in the jump roller.
Abstract: The large-scale turbulence and high air content in a hydraulic jump restrict the application of many traditional flow measurement techniques. This paper presents a physical modelling of hydraulic jump, where the total pressure and air–water flow properties were measured simultaneously with intrusive probes, namely a miniature pressure transducer and a dual-tip phase-detection probe, in the jump roller. The total pressure data were compared to theoretical values calculated based upon void fraction, water depth and flow velocity measured by the phase-detection probe. The successful comparison showed valid pressure measurement results in the turbulent shear region with constant flow direction. The roller region was characterised by hydrostatic pressure distributions, taking into account the void fraction distributions. The total pressure fluctuations were related to both velocity fluctuations in the air–water flow and free-surface dynamics above the roller, though the time scales of these motions differed substantially.