Showing papers on "Pressure measurement published in 1976"

On the separation of air flow over water waves

Abstract: Conditions leading to the onset of air-flow separation over a mobile air-water interface are discussed. It is argued that, in a frame of reference in which the interfacial boundary assumes a steady shape, the occurrence of separation requires a stagnation point on the interface. In the case of air blowing over water waves, this corresponds to the onset of wave breaking. These arguments are strongly supported by flow visualization and pressure measurements carried out in a laboratory wind-wave flume. Furthermore, the pressure measurements show a greatly enhanced interfacial shear stress for a breaking wave compared with that over an unbroken wave of the same wavelength. The implications of these findings for wind-wave generation are discussed.

Surface-acoustic-wave pressure and temperature sensors

Abstract: A sensitive sensor for the measurement of pressure and temperature is created by fabricating a surface-acoustic-wave (SAW) delay path on the surface of a thin diaphragm which, in turn, is in contact with the medium to be measured. The SAW delay path and associated electroacoustic transducers are utilized as the feedback circuit in a miniature electronic oscillator. Since the SAW time delay varies almost linearly with diaphragm temperature and pressure induced strain, the oscillator frequency is also a predominantly linear function of pressure and temperature. A frequency output sensor is desirable both for high-measurement resolution and for compatibility with digital data processors. Sensor configurations are discussed which can be optimized for independent measurement of either temperature or pressure.

Vapor Pressure of Water at Its Triple Point.

Abstract: The vapor pressure of water at its triple point was measured with exceptionally high accuracy by realizing it with a special apparatus and measuring the pressure with the NBS precision mercury manometer. The vapor pressure apparatus had a system for circulating the liquid water. Actual triple point conditions were established with a thin sheet of freshly distilled liquid flowing down over an exposed mantle of ice frozen on a vertical well. This technique reduced non-volatile contaminants and the vapor was repeatedly pumped to remove accumulated volatile contaminants. A diaphragm pressure transducer was used to separate the water vapor from the helium used to transmit the pressure to the manometer. The value found for the vapor pressure of water at its triple point was 611.657 Pa with an uncertainty of ± 0.010 Pa from random errors, computed at 99 percent confidence limits. The systematic errors are estimated to be insignificant relative to the random errors.

Respiration system with patient assist capability

Abstract: A method and apparatus for initiating a positive-pressure-assisted inspiration phase in response to a patient's inspiratory effort, and independently of the absolute pressure at the time of the inspiratory effort, since the absolute pressure may vary from patient to patient or depend upon a particular mode of operation of the respiration system. The invention apparatus includes a differentiator circuit for obtaining a time-differentiated pressure signal, and a circuit for detecting a change in the sign of the slope of the differentiated signal. The patient's inspiratory effort is manifested as an increased rate of pressure drop, and this shows up as a change in the sign of the slope of the differentiated pressure, which is detected independently of absolute pressure, and is utilized to initiate an assisted inspiration phase. The apparatus also includes circuitry for detecting a predetermined drop in pressure, from the time of detection of the inspiratory effort, to ensure that minor variations in the pressure signal will not trigger a spurious inspiration phase.

Multiple function pressure sensor

Abstract: Disclosed herein is a multiple function pressure sensor for use in combination with an electronic fuel injection system for an internal combustion engine. The preferred embodiment has two pressure sensitive elements in a single housing which generate signals indicative of the absolute pressure in the engine's intake manifold and the absolute value of the ambient or atmospheric pressure. Included electronic circuitry subtracts the value of the engine's manifold pressure from the value of the atmospheric pressure and generates a third pressure signal indicative of the difference between the manifold pressure and atmospheric pressure. These three pressure signals are utilized in the electronic fuel injection system for computing the fuel requirements of the engine under various operating conditions.

Digital pressure gauge system

Abstract: The digital pressure gauge system is particularly useful for reading blood pressures of humans, and has general utility in dial or disc type gauges for reading liquid and gas pressures. The digital pressure gauge system includes a rotary encoder which takes the place of the dial or disc of a conventional pressure gauge and therefore rotates to a degree proportional to the magnitude of the pressure being read. The rotary encoder carries a plurality of light sources which are selectively located for encoding particular angular positions of the rotary encoder. These light sources selectively direct light on photosensors which are connected by circuitry to digital readouts for converting the encoded information into a digital display. The displays may be contained in the gauge unit or they may be located remotely from the gauge unit if desired.

A New Interferometric Manometer

Abstract: A new manometer to measure gas pressures between vacuum and one atmosphere has been developed and is capable of easily tracking a continuously changing pressure at rates up to 600 Pa/s. It consists of a U-tube manometer in which the mercury surfaces are the reflectors of a Michelson interferometer. The difference in heights of the mercury surfaces is detected and measured by use of laser interferometry techniques with a He-Ne laser. The manometer is sensitive to changes in pressure of less than 40 mPa, but the ultimate accuracy of 180 mPa at a pressure of 101 kPa (2 parts in 106) is limited by the temperature uniformity and stability (10 mK).

Core noise source diagnostics on a turbofan engine using correlation and coherence techniques

Abstract: Fluctuating pressure measurements at several locations within the core of a turbofan engine were made simultaneously with far field acoustic measurements. Correlation and coherence techniques were used to determine the relative amplitude and phase relationships between core pressures at these various locations and between the core pressures and far field acoustic pressure. The combustor is a low frequency source region for acoustic propagation through the core nozzle and out to the far field. The relation between source pressure and the resulting sound pressure involves a 180 degree phase shift and an amplitude transfer function which varies approximately as frequency squared. This is consistent with a simplified model using fluctuating entropy as a source term.

Engine turbocharger diagnostics

Abstract: The turbocharger of an internal combustion engine is diagnosed by virtue of a single pressure measurement made during an acceleration of the engine using only its accessory loading, drag and inertia as a load, instead of making a profile of pressure ratio across the turbocharger under full load conditions on a dynomometer, as in the prior art. As the engine accelerates, pressure is continuously monitored, the ratio of the rate of change of the pressure with respect to time is made, and the maximum change in pressure per unit of time recorded; the minimum pressure sensed may also be recorded as an indication of the restrictive effect of the turbocharger when not being driven to its capacity.

Diffused semiconductor pressure gauge

Abstract: A diaphragm for a miniature pressure transducer has its surface sculptured by anisotropic etching to provide gauge areas in the form of narrow thin flexure areas between thick areas in the form of islands or motes. The thick areas act to constrain or stiffen the flexure areas from bending along their lengths while facilitating the bending thereof about axes parallel to their lengths when the diaphragm deflects in response to a pressure change. Linear piezoresistive gauges diffused into the gauge areas are responsive to the bending of said flexure areas to change resistance by an amount corresponding to the pressure change.

Mean Wind Loading on Rough-Walled Cooling Towers

Abstract: Mean pressure distributions were measured on a cooling tower model in uniform wind for several longitudinal-rib configurations and two uniformly distributed roughnesses. The base pressure coefficient is shown to be fairly constant along the cooling-tower height and independent of roughness in the range of Reynolds number independence. The difference between the base and minimum pressure coefficients, on the other hand, is shown to decrease with increasing relative roughness or decreasing relative rib spacing if there is not interaction between the flow patterns around consecutive ribs. This results in significant reductions in the magnitude of the negative mean side pressures on the structure and supports the use of strakes on prototypes for the purpose of reducing the mean side sections. The physical mechanisms responsible for the surface roughness effects are identified in the light of the boundary-layer theory. Possible choices as roughness configurations are examined within the limits of the available data.

Aircraft with oxygen supply and method of supplying oxygen thereto

Abstract: Oxygen is discharged from a source of supply into the cabin of an airplane under the control of an oxygen sensing device to maintain the supply of oxygen in each volume of air at a comfortable level but without increasing the pressure of the atmosphere in the plane above the pressure of the atmosphere at the altitude at which the plane is flying Expressed in other terms, as the plane ascends to altitudes above a preset level, the partial pressure of oxygen is maintained at a preset comfortable level while the absolute pressure in the cabin decreases with the decrease in pressure of the atmosphere outside the plane and remains at a level above the preset height This eliminates pressurizing the cabin or the need for breathing masks

The sodium chloride primary pressure gauge

Abstract: The failure of a central force model for sodium chloride is discussed. It is noted that it does not closely satisfy the Cauchy conditions at low temperatures, and that it fails the central force requirement of the Love condition. The available shock data for sodium chloride and its analysis is examined, and two reasons why the Hugoniot transformation pressure is likely to be less than 231 kbar are discussed. The important (but unjustified) theoretical assumptions made in converting Hugoniot to isothermal data is discussed; it is noted that serious error can enter for very large pressures for a given material and that at such high pressures the isothermal data should thus be considered only semiquantitative even if the Hugoniot data itself is accurate. An alternate method of estimating the isothermal transformation pressure from the Hugoniot transformation pressure is used. This method is based on the temperature derivative of the transformation pressure. On this basis it is concluded that an upper bound for the isothermal transformation of NaCl (to a CsCl-type structure) at room temperature is 257 kbar; it is noted that the actual value may be considerably less than this.

Pressure drop and phase fraction in oil-water-air vertical pipe flow

Abstract: Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Gearless pressure or temperature gauge

Abstract: A pressure gauge comprising a diaphragm, a cylinder seat, and a driving helix movable up or down to constitute the operating elements. A rotary shaft with a pin fixed thereon rotates clockwise or counterclockwise responsive to the movement of the diaphragm. The rotary shaft will return to its initial position when the pressure on the diaphragm is removed by the restoring force of a helical spring.

Chronic measurement of epidural pressure with an induction-powered oscillator transducer

Abstract: ✓ An induction-powered oscillator transducer (IPOT) was designed for the chronic measurement of epidural pressure. The transducer was completely implantable so all pressure measurements were made through the intact skin. The IPOT had a linear pressure range from −50 to +200 cm H2O, was sensitive to 1 mm H2O, and had a zero drift of less than 1 mm H2O/day under full load. Zero drift was minimized by using a hermetically-sealed metal bellows transducing element which was chemically treated to prevent corrosion and creep. The correlation between epidural pressure and intraventricular pressure was determined during the first 24 hours after implantation in six dogs. Epidural pressure was found to be a linear function of intraventricular fluid pressure. Epidural pressure and intraventricular pressure were essentially equal provided the epidural wedge pressure was minimized by proper insertion of the transducer. The correlation between epidural pressure and intraventricular pressure was determined after chronic ...

Pressure shifts and broadenings in the arc spectrum of krypton

Abstract: The pressure shifts and broadenings of a number of lines of Xe i in the visible and near infrared have been measured with xenon at pressures up to 1.5 Torr and with xenon at low pressure in helium at pressures up to 6 Torr. In most of the lines the shift due to xenon is to a longer wavelength, while that due to helium is to a shorter wavelength.

Vapor Pressure of Water at Its Triple Point: Highly Accurate Value

Abstract: The vapor pressure of water at its triple point was measured with greatly increased accuracy. The triple point was realized with newly designed equipment that enhanced the stability of the pressure and permitted any air released from solution to be removed by pumping. A diaphragm pressure transducer separated the water vapor from the helium used to transmit the pressure to the manometer. The pressure was measured with the National Bureau of Standards precision mercury manometer. The vapor pressure at the triple point was found to be 611.657 pascals with random uncertainties at the 99 percent confidence level of ± 0.010 pascal. The systematic errors are estimated to be relatively insignificant.

Supersonic pressure measurements and comparison of theory to experiment for an arrow-wing configuration

Abstract: A wind tunnel test of an arrow-wing-body configuration consisting of flat and twisted wings, as well as leading- and trailing-edge control surface deflections, was conducted at Mach numbers from 1.54 to 2.50 to provide an experimental pressure data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using a state-of-the-art inviscid flow, constant-pressure-panel method. Emphasis was on conditions under which this theory is valid for both flat and twisted wings.

High pressure x‐ray diffraction at liquid‐helium temperature

Abstract: An apparatus for high pressure x‐ray diffraction at liquid‐He temperature is described that consists of a vessel capable of holding pressure up to 100 kilobar between Bridgman anvils immersed in liquid He in a cryostat. A technique is described for attachment of vacuum‐tight beryllium windows to the cryostat. With this apparatus, the superconducting transition temperature of Pb and its dependence on pressure were measured; the pressure was determined from the lattice parameter of NaCl on the basis of the equation of state for NaCl. The result can be used as a low temperature manometer.

An Investigation into the Use of a Cone-Jet Sensor for Clearance and Eccentricity Measurement in Turbomachinery

Abstract: SYNOPSIS The paper describes experiments which demonstrate the feasibility of using a fluidic cone-jet sensor supplied with air and producing a pressure output to measure mean clearance, eccentricity and rotor speed inside a steam turbine. Mean clearance can be indicated on a bourdon tube pressure gauge whilst eccentricity can be measured using a piezo-electric pressure transducer and phase sensitive detection. Variation in mean clearance from 2mm to 4mm and eccentricity up to 0.37 mm have been shown to provide linear outputs within ± 5% of full scale. There is no significant fall-off in eccentricity signal up to a turbine rotor speed of 6000 rev/min.

The pressure exerted by an elastic stocking and its measurement.

Abstract: The pressure patterns exerted by elastic stockings are compared to the requirements, with some illustrations of pressure profiles. A simple gauge suitable for measuring pressure profiles is described and some results are given. The correct stocking and degree of vertical stretching may be determined using this pressure gauge as a monitor for the pressure profiles. The authors propose a simple method with the help of which it is possible to put the stocking on repeatedly with an identical pressure distribution to that obtained initially with the help of the gauge.

Monitor for blood pressure over long period - with pulse amplitude measurement for blocked flow simultaneous with pressure measurement

Abstract: The method for measuring and monitoring blood pressure over a long period is carried out by blocking arterial blood flow to measure first diastolic then systolic pressure, and simultaneously measuring pulse amplitude, and holding the results. for subsequent monitoring of blood pressure, pulse is measured at certain intervals. At least the fixed pulse amplitude value is compared with subsequently measured pulse amplitude. Any change in pulse amplitude and opt. diastolic pressure detected by comparison is used as a criterion for a change in systolic pressure.

Performance of a 1.57 pressure-ratio transonic fan stage with a screen-induced 90 deg circumferential inlet flow distortion

Abstract: A transonic fan stage having a design pressure ratio of 157 was tested with a 90 degree circumferential distortion imposed on the inlet flow The rotor diameter was approximately 508 cm, and the design pressure ratio was 160 at a tip speed of 425 m/sec Overall performance at 70 and 100 percent of design speed showed a loss of stall pressure ratio and flow range at design speed and no significant loss in stall pressure ratio at 70 percent of design speed Detailed flow measurements are presented to show the rotor-upstream flow interactions and the attenuation and amplification properties through the stage

Channel flow over a smooth-to-rough surface discontinuity with zero pressure gradient

Abstract: Measurements are given for the combined effects of a change of surface roughness and a simultaneous change of pressure gradient. The latter is negative in a fully developed turbulent, two-dimensional smooth channel flow upstream of the discontinuity, but is artifically held to a value of zero in the rough channel following the surface discontinuity. Measurements of mean velocity, turbulent intensity, and wall shear stress in the current zero pressure gradient apparatus are compared with similar measurements made in the same apparatus with a negative pressure gradient in the rough channel. Results indicate that removal of the pressure gradient in the rough channel does not affect the growth rate of the internal boundary layer nor that of the sublayer; nor does the modified pressure gradient greatly reduce the transitional overshoot of wall shear stress and turbulence intensity previously observed.

Blood pressure testing kit

Abstract: A blood pressure testing kit having the usual elements, namely, pressure gauge, humeral cuff, pump, bleed valve, and appropriate interconnections, and a stethoscope, is provided with a case which is in two parts hinged together but made of one integral piece of "living hinge" plastic material. One part of the case provides for storing all the said elements but the pressure gauge, which is mounted in the other case part, which acts also as lid for the same part. When the case is open, all the elements are manually accessible for use in blood pressure testing, and at the same time, the pressure gauge can be read while the testing procedure is being carried out.

Influence of tidal phenomena on interpretation of pressure buiild-up and pulse tests

Abstract: Bottom-hole pressure tests conducted in the Kingfish oil reservoir (located in Gippsland Basin - Offshore Victoria) during 1974 and 1975 using a high sensitivity surface recording electronic bottom-hole pressure gauge indicated the presence of sinusoidal pressure oscillations in the reservor. The oscillations are of the order of 0.1 psi in amplitude and their frequency suggests that they are in some way related to tidal phenomena. Although the oscillations do not affect production, they do influence interpretation of pressure build-up and pulse tests. Interpretations of both late time pressure build-up behaviour and pulse tests of small response magnitude and long time lags are considered to be particularly susceptible to errors due to these oscillations if they are not recognized and corrected for. Interpretations of early time pressure build-up data and pulse tests of definite response and relatively short time lags are not regarded as being significantly affected. The physical mechanism causing these pressure oscillations in the reservoirs is not known. However, one of the various possible hypotheses is that the Latrobe Formation sands could be outcropping on the ocean floor at abyssal depths southeast of Kingfish and that the pressure transients generated by changes in the hydrostatic head due to surfate tides are transmitted hydraulically to the reservoir. If this hypothesis is proved to be valid it could influence pressure performance predictions of Gippsland Basin reservoirs.