Showing papers on "Pressure measurement published in 1997"

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Abstract: The unit-cell parameters of quartz, SiO2, have been determined by single-crystal diffraction at 22 pressures to a maximum pressure of 8.9 GPa (at room temperature) with an average precision of 1 part in 9000. Pressure was determined by the measurement of the unit-cell volume of CaF2 fluorite included in the diamond-anvil pressure cell. The variation of quartz unit-cell parameters with pressure is described by: a −4.91300 (11) = −0.0468 (2) P + 0.00256 (7) P2 − 0.000094 (6) P3, c − 5.40482 (17) = − 0.03851 (2) P + 0.00305 (7) P2 − 0.000121 (6) P3, where P is in GPa and the cell parameters are in angstroms. The volume–pressure data of quartz are described by a Birch–Murnaghan third-order equation of state with parameters V0 = 112.981 (2) a3, KT0 = 37.12 (9) GPa and K′ = 5.99 (4). Refinement of K′′ in a fourth-order equation of state yielded a value not significantly different from the value implied by the third-order equation. The use of oriented quartz single crystals is proposed as an improved internal pressure standard for high-pressure single-crystal diffraction experiments in diamond-anvil cells. A measurement precision of 1 part in 10 000 in the volume of quartz leads to a precision in pressure measurement of 0.009 GPa at 9 GPa.

Increased intra-abdominal pressure and cardiac filling pressures in obesity-associated pseudotumor cerebri

Abstract: Objectives.: To determine whether intra-abdominal pressure (as estimated from urinary bladder pressure) is elevated in patients with central obesity (as measured by sagittal abdominal diameter) and pseudotumor cerebri and whether this increased intra-abdominal pressure is associated with increased pleural pressure and cardiac filling pressure, implying a resistance to venous return from the brain. Design.: Nonrandomized, prospective. Setting.: University hospital, operating room. Main outcome measurements.: Intracranial pressure, urinary bladder pressure, sagittal abdominal diameter, transesophageal pleural pressure, central venous pressure, pulmonary artery pressure, and pulmonary artery occlusion pressure. Subjects.: Six women with pseudotumor cerebri (one with CSF leak, one with lumboperitoneal shunt). Results.: Urinary bladder pressure (22 ± 3 cm H 2 O) and sagittal abdominal diameter (29 ± 3 cm) were significantly elevated in these patients with elevated intracranial pressure (293 ± 80 mm H 2 O) compared with a previously reported group of nonobese control patients. The transesophageal pleural pressure (15 ± 10 mm Hg), central venous pressure (20 ± 6 mm Hg), mean pulmonary artery pressure (31 ± 6 mm Hg), and pulmonary artery occlusion pressure (21 ± 7 mm Hg) were all markedly elevated compared with published normal values and with previous data from obese patients without pseudotumor cerebri. Conclusions.: These data support the hypothesis that central obesity raises intra-abdominal pressure, which increases pleural pressure and cardiac filling pressure, which impede venous return from the brain, leading to increased intracranial venous pressure and increased intracranial pressure associated with pseudotumor cerebri.

Sound-pressure measurements in the cochlear vestibule of human-cadaver ears

Abstract: The middle-ear pressure gain for the 50-Hz to 12-kHz range was determined from the ratio of sound pressures measured in the vestibule and the ear canal of four human-cadaver ears. The magnitude of the middle-ear pressure gain is 20 dB for frequencies between 500 Hz and 2 kHz. Above 4 kHz, the gain changes as a function of frequency at a rate of approximately -8 dB/octave and below 400 Hz at 4 dB/octave. The standard error of the mean magnitude across the four ears is typically less than 3 dB. The phase angle of the pressure gain also changes with frequency. Interruption of the ossicular chain decreases the vestibule pressure by at least 20 dB. It is shown that air bubbles in the inner ear can diminish the vestibule pressure; procedures are used to remove bubbles. From these pressure measurements and previous measurements of stapes motion, the frequency dependence of behavioral thresholds for tones was tested to discover whether it corresponds to the constancy of a physiological variable at the cochlear input. Among pressure, power, or stapes-motion measures, the vestibule pressure is most nearly constant with frequency at the behavioral "minimum audible pressure."

Pt resistor thermometry and pressure calibration in a clamped pressure cell with the medium, Daphne 7373

Abstract: Calibration of a Pt resistance thermometer (Netsushin) in magnetic fields and under pressure in the range of 1.5–300 K and below 1.5 GPa is presented. With the pressure medium, olefin olygomers, Daphne 7373, the pressure is continuous at its solidification and the pressure drop from 300 to 4.2 K by 0.15–0.17 GPa is constant, irrespective of the initial clamped pressure at 300 K. The applicability of the thermometer and the medium for precise study in field and pressure at low temperature is discussed.

Improved calibration of the SrB4O7:Sm2+ optical pressure gauge: Advantages at very high pressures and high temperatures

Abstract: This paper presents a new calibration of the pressure shift of the 7D0−5F0 fluorescence line of SrB4O7:Sm2+, in hydrostatic medium (helium) up to 124 GPa and in nonhydrostatic medium (H2O) up to 130 GPa. There is no quenching of the luminescence, in contrast to that observed in similar compounds. We show that this line permits more accurate pressure measurements at very high pressure than the commonly used R1 emission line of ruby because it remains intense, sharp, well isolated from the other lines, and weakly dependent on nonhydrostaticity. The wavelength pressure shift of the 7D0−5F0 line is found to be very well represented by the nonlinear relation: P=4.032Δλ(1+9.29×10−3Δλ)/(1+2.32×10−2Δλ) with P in GPa and Δλ=λ−685.41 in nm. High temperature experiments up to 900 K at room pressure were also performed. The negligible temperature dependence and the small thermal line broadening are further advantages for high pressure–high temperature studies in diamond anvil cells. A metrology for in situ measurements of pressure and temperature, based on the combined use of this compound with ruby is also presented, along with a new calibration of the ruby R1 frequency shift with temperature from 300 to 800 K.

Identifying and Removing Barometric Pressure Effects in Confined and Unconfined Aquifers

Abstract: Failing to account for barometric pressure effects in water level measurements can introduce errors by misestimating the total head and by adding noise to water level measurements. For determining the total head in an aquifer, we assert that the air pressure head at the water surface in the well must be added to measured water levels (equivalent to using an absolute pressure transducer) even though the resulting values may have larger temporal and spatial variability than the original water level measurements. At the Savannah River Site in South Carolina, the average barometric pressure variation is 6 to 7 cm, with a range of over 30 cm. Failure to account for barometric pressure variability could result in misestimation of the direction and magnitude of the hydraulic gradient at the site. We also demonstrate procedures for removing barometric effects, such as to reduce noise during an aquifer pumping test, and to identify mechanisms by which barometric pressure affects water levels. Three mechanisms are summarized including: an instantaneous response for confined aquifers; a delayed response due to borehole storage in confined and unconfined aquifers; and a delayed response in unconfined aquifers due to the passage of barometric pressure changes through the unsaturated zone. Using data from the Savannah River Site, barometric efficiencies are estimated using linear regression and a modification of Clark's Method. Delayed responses are estimated using regression deconvolution. The type of barometric effect provides diagnostic information about whether the aquifer is confined or not, the presence of borehole storage or skin effects, and the air diffusivity coefficient within the unsaturated zone. We also show how removal of barometric pressure effects improves the ability to observe otherwise unnoticeable effects.

Development and validation of a noninvasive method to determine arterial pressure and vascular compliance

Abstract: The ability not only to record automated systolic and diastolic pressure, but also to derive measurements of the rate of pressure change during the cardiac cycle, would have great potential clinical value. A new method has been developed to obtain pressure measurements at 20-ms intervals by oscillometric cuff signal pattern recognition. Derivation of noninvasive pressure measurements is based on a T tube aorta and straight tube brachial artery, and assumes that the systolic phase of the suprasystolic cuff signal and the diastolic phase of the subdiastolic cuff signal most closely approximate systolic and diastolic aortic pressures, respectively. Arterial pressures obtained by this method were compared with simultaneous invasive measurements from the thoracic aorta in 36 patients. Good agreement was observed between noninvasive and invasive methods for systolic (146 +/- 4 vs 145 +/- 5 mm Hg), diastolic (80 +/- 2 vs 77 +/- 2 mm Hg), and mean (100 +/- 3 vs 100 +/- 3 mm Hg) arterial pressures, and correlation coefficients were r = 0.94, 0.91, and 0.95, respectively. To assess the validity of measurements of the rate of pressure change, oscillometric cuff signals from a subgroup of 14 patients were analyzed in detail for the peak positive pressure derivative (dP/dt(Max)), peak negative pressure derivative (dP/dt(Min)), and time interval between peak positive and peak negative pressure derivatives [t(pp)]. Results (mean +/- SEM) were: [table in text]. The incorporation of measurements of the rate of pressure change into a physical model of the brachial artery was used to derive vascular compliance. A significant correlation was observed between vascular compliance derived from the oscillometric signal and determinations by either thermodilution or Fick methods and noninvasive pressures (n = 20, r = 0.83, p 4%, representing a reproducible measure of vascular structure and function. We conclude that the measurement of absolute pressure and rate of pressure change show good correlation with catheter data and that vascular compliance can be reliably assessed by this new method. The technology should provide a valuable noninvasive tool for the assessment of both cardiac function and vascular properties.

Vortex Shedding in a Large Solid Rocket Motor Without Inhibitors at the Segment Interfaces

Abstract: The internal acoustic response of the Titan IV Solid Rocket Motor Upgrade (SRMU) is analyzed using pressure oscillation time histories measured during four static e ring tests. Pressure oscillations for other large solid rocket motors are caused by vortex shedding at annular inhibitors and acoustic feedback resulting from impingement of the vortices on other inhibitors or on the solid rocket motor nozzle. The SRMU does not have inhibitors, but it is shown that acoustic feedback also dee nes its pressure oscillations. Vortices are shed around the cavity between the center and aft segments and impinge on the nozzle entrance. The frequencies of the pressure oscillations vary about that of the motor fundamental acoustic mode and generally agree with a simple empirical relationship that has been used to model acoustic feedback. The effect of the SRMU pressure oscillations on dynamics and control of the Titan IV system is minor. I. Introduction A NEW solid rocket motor design called the Solid Rocket Motor Upgrade (SRMU) will be integrated with the Titan IV system beginning in late 1996. The SRMU has a lower inert weight and higher propellant weight than the current Titan IV solid rocket motor, and therefore, augments system performance. The SRMU has three segments (forward, center, and aft) and is the only large solid rocket motor in production that does not have annular inhibitors at the segment interfaces to prevent combustion and to support the propellant grain during burning. A. SRMU Static Firing Tests Five static e ring tests were conducted for qualie cation of the SRMU. The test articles included one preliminary qualie cation motor (called PQM19) and four qualie cation motors (called QM1, QM2, QM3, and QM4 ). The tests were conducted vertically, nozzle down at the Phillips Laboratory 1-125 Firing Complex, Edwards Air Force Base. 1 The test cone guration and the attachments of the solid rocket motor to the test stand simulated e ight. The physical differences between the e ve test motors were minor and are believed to have had a negligible effect on combustion stability. The static e ring tests were conducted at propellant bulk temperatures in the range 36.5‐ 937F (2.5‐ 33.97C) to assess the effect on motor performance. The static e ring test instrumentation included Condec gauges (CCC-406) of absolute pressure on the forward closure (measurement PCF1 ) and on the aft dome (measurement PCA1), and a Kistler gauge (202M122) of oscillatory pressure (measurement PD4 ) on the forward closure. 2 Measurements PCF1 and PCA1 were recorded by a Neff digital acquisition system, while measurement PD4 was recorded by a Metraplex FM system. The Neff system applied a 100-Hz low-pass e lter and recorded measurements PCF1 and PCA1 at 250 samples/s.

Pull-in time dynamics as a measure of absolute pressure

Abstract: The squeezed-film damping component of the pull-in time of an electrostatically-actuated micromechanical fixed-fixed beam is shown to be a sensitive, and nearly linear function of ambient air pressure in the measured range of 0.1 mbar to 1013 mbar (1 atm or 760 Torr). Pull-in time simulations, based on a one-dimensional macromodel using a damping constant proportional to pressure, are in good agreement with measured data. The data and simulations show that pull-in type devices will make excellent microelectromechanical systems (MEMS) sensors for broad-range absolute pressure measurements and for in situ leak monitoring of hermetically scaled packages containing other sensors or IC's. The pull-in sensors are compatible with any MEMS fabrication processes that allow out-of-plane electrostatic actuation, including surface micromachining and silicon wafer-bonding, and they do not require a cavity sealed at vacuum or at a reference air pressure.

Method and apparatus for measuring pressure in a coriolis mass flowmeter

Abstract: A method for determining pressure in an operating Coriolis effect mass flowmeter (10). The Coriolis flowmeter flow tubes (130, 130') are vibrated in both a bending mode (as is normal for measuring mass flow rate) and in a twisting mode. The ratio of the fundamental frequencies at which the flow tubes vibrate in each of the two vibration modes is proportional to the pressure within the flow tubes. In the preferred embodiment, a sum/difference method initially isolates the superposed sinusoids representing the fundamental frequencies of the two vibrational modes. Fast conjugate gradient (FCG) digital filters (512, 514) are then used to rapidly estimate the fundamental frequencies in each of the two vibration modes. The estimated frequencies are then used by filter chains including digital notch (518, 508) and band pass filters (506, 1520) as well as recursive maximum likelihood (RML) digital filter (510, 522) techniques to enhance the bending mode and twisting mode fundamental frequency estimates. The enhanced bending mode andtwisting mode frequency estimates are used to determine the pressure within the flow tubes as a function of the ratio of the two frequencies as well as to center the notch and band pass filter chains used to enhance the bending mode frequency of the two vibration sensor channels for mass flow rate computations. The pressureso determined may then be used to correct mass flow rate computations or for other pressure measurement purposes per se.

Collisional particle pressure measurements in solid liquid flows

Abstract: Experiments were conducted to measure the collisional particle pressure in both cocurrent and countercurrent flows of liquid-solid mixtures. The collisional particle pressure, or granular pressure, is the additional pressure exerted on the containing walls of a particulate system due to the particle collisions. The present experiments involve both a liquid-fluidized bed using glass, plastic or steel spheres and a vertical gravity-driven flow using glass spheres. The particle pressure was measured using a high-frequency-response flush-mounted pressure transducer. Detailed recordings were made of many different particle collisions with the active face of this transducer. The solids fraction of the flowing mixtures was measured using an impedance volume fraction meter. Results show that the magnitude of the measured particle pressure increases from low concentrations (>10% solid volume fraction), reaches a maximum for intermediate values of solid fraction (30-40%), and decreases again for more concentrated mixtures (>40%). The measured collisional particle pressure appears to scale with the particle dynamic pressure based on the particle density and terminal velocity. Results were obtained and compared for a range of particle sizes, as well as for two different test section diameters. In addition, a detailed analysis of the collisions was performed that included the probability density functions for the collisoin duration and collision impulse. Two distinct contributions to the collisional particle pressure were identified: one contribution from direct contact of particles with the pressure transducer, and the second one resulting from particle collisions in the bulk that are transmitted through the liquid to the pressure transducer.

Impulse line blockage detector systems and methods

Abstract: A differential pressure sensor is attached to a process via a high and a low pressure impulse line. An absolute pressure sensor is also attached to each impulse line. To determine if an impulse line is blocked, a noise signal is acquired from the corresponding absolute pressure sensor. A variance of the noise signal is determined and compared to a threshold. If the variance is less than the threshold, an impulse line blockage is indicated.

The diamond 13C/12C isotope Raman pressure sensor system for high-temperature/pressure diamond-anvil cells with reactive samples

Abstract: By using a thin 13C diamond chip together with a 12C diamond chip as sensors, the diamond Raman spectra provide the means to measure pressure precisely (±0.3 GPa) at any temperature (10–1200 K) and simultaneous hydrostatic (or quasihydrostatic) pressure (0–25 GPa) for any sample compatible with an externally heated diamond-anvil cell. Minimum interference between the Raman spectrum from the diamond anvils and those of the pressure sensors is obtained by measuring pressures with the Raman signal from the 13C diamond chip up to 13 GPa, and that from the 12C chip above 10 GPa. The best crystallographic orientation of the diamond anvils is with the [100] direction along the direction of applied force, in order to further minimize the interference. At 298 K, the pressure dependence of the 13C diamond first-order Raman line is given by ν(P)=νRT+aP for 91 at. % 13C diamond, where νRT(13C)=1287.79±0.28 cm−1 and a(13C)=2.83±0.05 cm−1/GPa. Analysis of values from the literature shows that the pressure dependence of...

Levitation apparatus for structural studies of high temperature liquids using synchrotron radiation

Abstract: A new levitation apparatus coupled to a synchrotron-derived x-ray source has been developed to study the structure of liquids at temperatures up to 3000 K. The levitation apparatus employs conical nozzle levitation using aerodynamic forces to stably position solid and liquid specimens at high temperatures. A 270 W CO2 laser was used to heat the specimens to desired temperatures. Two optical pyrometers were used to record the specimen temperature, heating curves, and cooling curves. Three video cameras and a video recorder were employed to obtain and record specimen views in all three dimensions. The levitation assembly was supported on a three-axis translation stage to facilitate precise positioning of the specimen in the synchrotron radiation beam. The levitation system was enclosed in a vacuum chamber with Be windows, connections for vacuum and gas flow, ports for pyrometry, video, and pressure measurements. The vacuum system included automatic pressure control and multi-channel gas flow control. A phos...

Surface pressure measurement in a cryogenic wind tunnel by using luminescent coating

Abstract: In recent experiments, we demonstrated the feasibility of using luminescent coatings for surface pressure measurement in a cryogenic wind tunnel. This technique is based on a new coating technology in which luminescent molecules are directly deposited onto the model surface by an electrochemical process. The resulting coating has an extremely high oxygen sensitivity for mole fractions of oxygen is less than 0.1%. This capability allows us to measure the pressure field on the model surface in a cryogenic wind tunnel. To demonstrate this technology, a 14%-thick bump model was tested in the 0.1-m Transonic Cryogenic Wind Tunnel at NAL. Mach number was changed from 0.4 to 0.84 whereas temperature was maintained at 100 K. A small amount of oxygen was injected into the tunnel and the mole fraction of oxygen in the test gas was kept constant. We acquired two intensity images, one taken at low speeds and the other taken at high Mach numbers. By taking the ratio of these images, surface pressure distributions on the model were clearly captured. The result of the in situ calibration showed that effects of temperature dependence of the coating was negligible. The paint-derived pressure distributions are in good agreement with pressure tap measurements.

Article comprising an optical fiber attached to a micromechanical device

Abstract: An article having an optical fiber integrally attached to a micro-device having spaced movable and nonmoving layers suitable for creating optical interference effects is disclosed. In one configuration, the micro-device is suitable for optical modulation, wherein the movable layer is electrostatically actuated to move towards the nonmoving layer. Such movement changes the size of the gap between the layers, resulting in a change in micro-device reflectivity. An optical signal is modulated by controlling micro-device reflectivity via a controlled voltage source. In a second configuration, the micro-device is suitable for measuring pressure. For pressure measurement, the movable membrane moves in response to pressure changes. The change in membrane position again results in a change in micro-device reflectivity. Reflectivity is correlatable to pressure. In a third configuration, the micro-device is suitable for measuring temperature. In the third configuration, the movable membrane is isolated from pressure effects by the addition of an evacuated cavity located beneath the membrane. The region between the movable and nonmoving layers is gas filled. Changes in gas pressure due to changes in gas temperature cause the movable layer to move, affecting micro-device reflectivity. Reflectivity is correlatable to temperature.

Validation of an automated arterial tonometry monitor using Association for the Advancement of Medical Instrumentation standards.

Abstract: BACKGROUND: Arterial tonometry is a noninvasive technique for monitoring the arterial blood pressure in a continuous manner. Real-time arterial blood pressure measurements are advantageous in many clinical settings, but arterial tonometric devices must be validated prior to clinical acceptance. Guidelines for accuracy for noninvasive blood pressure monitors have been established by the Association for the Advancement of Medical Instrumentation. OBJECTIVE: To test the Colin Pilot 9200 configured with an arterial tonometry module with 20 patients and to compare tonometric blood pressure measurements with intra-arterial blood pressure measurements. METHODS: All of the patients in the study were aged over 14 years and weighed over 35 kg; testing was performed in the operating room or in the intensive care unit. Data from each patient consisted of multiple simultaneous recordings of tonometric and intra-arterial blood pressure values. The data were then compared; the mean and SD of the difference between the two measurement devices were then calculated. RESULTS: Tonometric values were slightly less than the intra-arterial pressure measurements; the mean difference for systolic blood pressure was 2.24 +/- 8.7 mmHg and for diastolic pressure was 0.26 +/- 8.88 mmHg. CONCLUSION: The arterial tonometry module incorporated into the Colin Pilot 9200 was investigated for use with selected adult and pediatric populations. With our patients, it generated accurate data throughout a wide blood pressure range. It satisfied Association for the Advancement of Medical Instrumentation standards for mean systolic and diastolic blood pressure measurements and only minimally exceeded the allowable SD. This technology should prove to be a valuable tool for noninvasive blood pressure monitoring of various patient populations.

Miniature gauge pressure sensor using silicon fusion bonding and back etching

Abstract: A gauge or differential pressure sensor has a base portion having walls which define a cavity within the base portion and a diaphragm portion positioned over the cavity. The base portion comprises silicon; the diaphragm portion comprises silicon; the substrate has a passageway from a surface of the substrate into the chamber; the walls of the cavity form an angle with the diaphragm of no more than ninety degrees; and the chamber has a depth of at least about 5 microns. Preferably, the pressure sensor has a lip within the passageway which prevents an adhesive used to glue the sensor to a base from flowing to the diaphragm and fouling it. The pressure sensor is made by forming a cavity in a first wafer, fusion bonding a second wafer over the first wafer in an oxidizing environment, and using the thin oxide formed when fusion bonding the wafers as an etch stop when opening the cavity to the atmosphere. Etch conditions are selected to form the preferred lip in the passageway. The pressure sensor has improved accuracy and reliability as well as small size.

Rotor blade pressure measurement in a high speed axial compressor using pressure and temperature sensitive paints

Abstract: Pressure and temperature sensitive paints have been utilized for the measurement of blade surface pressure and temperature distributions in a high speed axial compressor environment. Four blades were painted, two with temperature sensitive paints and two with pressure sensitive paints. This combination allows temperature distributions to be accounted for when determining the blade suction surface pressure distribution. Measurements were taken and pressure maps on the suction surface of a blade were obtained over a range of rotational speeds. The formation of a suction surface shock was detected at the higher speeds. Introduction Pressure and temperature sensitive paints (PSP and TSP) offer a unique and inexpensive means of determining surface pressure and temperature distributions. Continuous surface pressure and temperature distributions, impossible to obtain using conventional measurement techniques, are critical for understanding complex flow mechanism and allow direct comparisons with results from computational fluid dynamic calculations (CFD). Cost for a PSP/TSP measurement system can be justified when one considers the cost of a single permanently installed pressure f Postdoctoral Research Assistant, Member AIAA * Graduate Research Assistant, Student Member AIAA t Professor, Member AIAA Copyright © 1997 by the American Institute of Aeronautics and Astronautics, Inc. All Right Reserved. transducer. Not only is the cost of installing these conventional probes an issue, but the aerodynamics and structural dynamics of the model can be seriously altered by modifications to accommodate the transducers and static pressure taps. Data rates for PSP and TSP are several orders of magnitude faster than data rates for conventional techniques. The theory and applications of PSP and TSP techniques are detailed in the later sections. Aerodynamic loads on turbomachine blade rows result in fatigue failure of rotating components. Increased fatigue life of all internal components would lead to reduced costs incurred by the owner. Hence, advancement in the fundamental understanding of blade surface pressure distribution will lead to improved designs and reduced costs in both development and maintenance of a gas turbine engine. Pressure measurements obtained with pressure sensitive paints will provide not only the variations in pressure on the whole blade surface, but will provide a large data base of pressure data which will be useful in development of advanced forced response models for use in turbomachine design. Recently, PSP measurements on rotating machinery were conducted by Burns and Sullivan [1.] with a laser-PMT based system. They obtained pressure distributions on a small wooden propeller and a TRW Hartzell propeller. Their PSP-derived pressure distributions across the blades show reasonable trends. In this study, the PSP and TSP techniques are further used to measure pressure and temperature distributions on rotor blades in a high speed axial compressor. Axial Compressor Facility The Purdue Research Axial Fan Facility features a 30.48 cm (12 in.) diameter, 2/3 hubtip ratio compressor rotor which is integral with the shaft. The drive system consists of a 400 horsepower AC motor driving a magnetic clutch with a variable speed output that drives a gearbox, as shown in Figure 1. Eighteen inlet guide vanes are twisted to produce a free vortex whirl into a 19 blade axial flow rotor. Both the inlet guide vanes and the rotor blades are designed with NACA 65 series airfoil sections on circular arc meanlines. The aluminum rotor blades have 2 in. chord and 2 in. span from the hub to tip. Located downstream of the rotor are eight aerodynamic struts that support the rotor bearing housing. Axial spacing between the trailing edge of the rotor and the leading edge of one of the struts nondimensionalized by the rotor chord CR is L/CR = 3.47. For these experiments, axial IGV-to-rotor spacing to chord ratio is set at Z/CR = 0.6 (10° IGV stagger angle). Note that the selection of rotor speeds is dictated by th&vibrational level of the machine. The velocity measurements have been made using hot-film sensors between the IGV and rotors. Typical spanwise distrtbjjjfions of relative Mach numbers and absolute flow angles at 14,750 rpm are shown in Fig, 2 (a) and (b), where %U/CR is the relative upstream distance from the rotors. A detailed discussion about hot-film measurements in the compressor is given by Johnston and Fleeter [2], PSP and TSP Theory and Measurement Techniques The physical processes involved in behavior of PSP and TSP have been thoroughly presented in literature [3-11], but will be covered briefly in this section for completeness. A probe molecule embedded in a polymer^ binder is elevated to an excited state by absorbing light of a particular wavelength. The molecule will return to the ground state by releasing the excitation energy. Energy can be dissipated via emission of light (fluorescence and phosphorescence) or through radiation less deactivation processes such as oxygen quenching and thermal quenching. For pressure sensitive paints (PSPs), the excess energy can be absorbed by oxygen molecules through a process in which energy is transferred to oxygen molecules in a collisional manner. This process, known as oxygen quenching, depends upon the concentration of oxygen molecules. Since the concentration of oxygen molecules is proportional to the partial pressure of oxygen, luminescence is sensitive to pressure due to the oxygen quenching process and can be modeled with the Stern-Volmer relation:

High pressure combustion turbine and air separation system integration

Abstract: A high pressure combustion turbine is integrated with a double column cryogenic air separation system by cooling and purifying a portion of the compressed air from the combustion turbine compressor, work expanding a first portion of the resulting cooled air, and introducing the expanded air into the low pressure column. A second portion of the resulting cooled air is further cooled, throttled, and introduced into the high pressure column. A nitrogen product stream is returned to the turbine combustor, and a portion of the nitrogen product stream optionally is cooled, throttled, and recycled into the high pressure column. Preferably the higher pressure column operates at an absolute pressure which is about 20% to about 85% of the absolute pressure of the compressed air from the combustion turbine air compressor. Optionally an oxygen-rich liquid or a nitrogen-rich liquid is withdrawn from the higher pressure column during a period of low nitrogen product demand, stored, and withdrawn from storage to supplement feed to the lower pressure column during periods of high nitrogen product demand. Alternatively, high purity liquid oxygen is withdrawn from the lower pressure column during a period of low oxygen product, stored, and withdrawn from storage during periods of high oxygen product demand to supplement oxygen product withdrawn from the higher pressure column.

Digital remote gauge assembly

Abstract: The present invention includes a portable, damage resistant, palm-held, low cost, high sensitivity ergonomically dimensioned digital remote gauge assembly unit for the measurement of external parameters that include by way of example temperature, pressure, and vacuum; a kit having a digital remote gauge assembly unit, a variety of probes and adapters that provide for the communication signals to the unit in response to externally measured parameters, and a communication link between a respective probe and the digital remote gauge assembly unit; and, a method of utilizing the kit and device to facilitate the rapid measurement of a variety of external parameters. The digital pressure gauge includes a gauge body dimensioned to be held in the palm of a user's hand. The gauge body has microprocessor controlled circuitry therein, an altitude and temperature compensated pressure transducer in communication with the microprocessor, and keys for actuating the microprocessor. The body also includes a display for informing the user of readings taken in a mode of operation of the device, a probe assembly; and, a multi-conductor shielded cable connecting the gauge body and the probe assembly. The gauge also includes routines providing a plurality of the modes of operation of the gauge including a PSI mode, a KPA mode, a PEAK HOLD mode, a HI/LO resolution mode, and a temperature mode in which the display presents a temperature of a fluid being tested in either °C. (Centigrade) or °F. (Fahrenheit).

Piezo-dynamometric platform for a more complete analysis of foot-to-floor interaction

Abstract: A compound instrument was constructed by superimposing a dedicated pressure platform on a commercial force platform. This instrument simultaneously estimates the ground reaction force resultants (vertical and shear forces, free moment and location of the center of pressure), pressure distribution throughout the foot-floor contact area, the trajectory of the center of pressure superimposed on the contact area (footprint). On the basis of the readings provided by the force plate the authors calibrated pressure sensors more accurately. They could therefore accurately estimate the vertical local components of the ground reaction. This information and the measured shear force resultants were essential for computing the shear forces acting on elementary areas corresponding to the active surface of each pressure sensor. This, in turn, allowed the authors to estimate the vertical and shear force resultants and free moment for subareas of the foot. This is a feature peculiar to this compound instrument, and for its effective exploitation the authors have implemented a few methods for the reliable identification of the subareas of interest. Two application instances are hereby reported.

System generating a pressure profile across a pressure sensitive membrane

Abstract: An improved fluid pressure sensor/sensor array is shown to provide high resolution, sensitivity which can be easily controlled based on anticipated or detected pressure range, and reliable pressure measurements with easy installation and low fabrication cost. A fluid pressure sensor is provided having a substantially incompressible mounting structure with a cavity formed therein. An elastic membrane is attached to said mounting structure and across said cavity, separating the cavity from the fluid to be measured. At least one non-contact transducer is attached to the mounting structure in the cavity to detect deflection at a selected plurality of regions on the membrane. The sensitivity and pressure range of the sensor can be chosen by preselecting the elasticity of the membrane, stretching the membrane across the cavity under a preselected tension, maintaining a predetermined reference pressure in the cavity, and/or actively controlling the membrane tension. For a pressure sensor array, there are at least two fluid pressure sensors, where at least one sensor is of the type described herein. A sensor array can also be formed by multiple cavities within a single mounting structure.

Device for compensating for flow resistance in a ventilator/respirator

Abstract: A device for compensating for flow resistance in an expiratory section of a ventilator system has a bellows system whose increase in volume during expiration is regulated by a regulatory device and a control unit, so that expired gas fills the bellows system. The increase in volume is regulated according to values measured for pressure so virtually complete compensation for flow resistance is attained. Pressure is measured with a first pressure gauge located by the bellows system, and a second pressure gauge located by the patient. The device can be a separate apparatus which is connectable to a ventilator, or can be totally integrated into the ventilator.

A high density capacitive pressure sensor array for fingerprint sensor application

Abstract: This paper reports on the first technological and electrical results on the sensitive part of a fingerprint sensor which consists of an X-Y array of absolute pressure capacitive sensitive cells with a pitch of 50 /spl mu/m. Manufacturing is carried out using a specific CMOS compatible silicon surface micromachining process. Very good cell sensitivity homogeneity has been measured at a wafer level thanks to an automatic probe test. Pressure sensor geometrical parameters and membrane material Young modulus have been deduced from tests on individual cells. Results are in good agreement with theory and have been confirmed by deflexion interferometric measurements.