Showing papers on "Overpressure published in 1990"

Extended measurement capability transmitter having shared overpressure protection means.

Abstract: A transmitter (10) measures pressures and has a pressure sensor (88) and an additional pressure sensor (90) providing additional measurement capability to the transmitter (10), such as an extended measurement range or measurement redundancy. Both pressure sensors (88, 90) share an overpressure protection device (12) which protects them from pressures exceeding a preselected pressure limit. The pressure sensors (88, 90) are batch fabricated and are formed in a single piece of brittle material (86).

Versatile, overpressure proof, absolute pressure sensor

Abstract: A non membrane-based overpressure proof gas pressure microsensor. It is not a membrane-based microsensor but is based on an open microbridge sensor structure. A method and apparatus is described to determine gas pressure from thermal conductivity, k, and volumetric specific heat, c pu , as well as pressure, P, using a microbridge sensor.

Retrieval of turbulent pressure fluctuations at the ground surface beneath a forest

Abstract: The relationship between surface pressure fluctuations and the velocity field associated with turbulent coherent structures is examined for flow within and above a deciduous forest. Measurements were taken with tower-mounted sonic anemometer/thermometers at six heights, Lyman-alpha humidiometers at three heights, and a pressure sensor at the forest floor. We find a strong, near-linear relationship between the mean square turbulent velocity and the standard deviation of the high-pass-filtered pressure fluctuations. Lagged cross-correlations between vertical velocity fluctuations and those of pressure show maximum correlations of ± 0.5 but with a phase offset. Examination of surface pressure during the passage of coherent structures, which are characterized by a transition from ejection to sweep, reveals a period of overpressure about 20 s in duration roughly centered on the time of passage of the scalar microfront at the top of the canopy. Pressure patterns associated with coherent structures appear to be largely responsible for the form of the correlations stated above. Pressure patterns calculated from an integrated Poisson equation, using observed velocity and temperature signals during coherent structures, match the main features of the observed pressure. Retrieval of the pressure fluctuations in this manner reveals that the mean wind shear/turbulence interaction term is dominant, but that important contributions arise from two other terms in the equation. Buoyancy effects are negligible. We show that the surface pressure signal is mainly created by the velocity field near the top of the forest, and present evidence to suggest that features of the sub-crown air movement result directly from this pressure field.

Application of CFD to sonic boom near and mid flow-field prediction

Abstract: A 3-D parabolized Navier-Stokes (PNS) code was used to calculate the supersonic overpressures from three different geometries at near- and mid-flow fields. Wind tunnel data is used for code validation. Comparison of the computed results with different grid refinements is shown. It is observed that a large number of grid points is needed to resolve the tail shock/expansion fan interaction. Therefore, an adaptive grid approach is employed to calculate the flow field. The agreement between the numerical results and the wind tunnel data confirms that computational fluid dynamics can be applied to the problem of sonic boom prediction.

Single-crysytal silicon pressure sensors with 500 × overpressure protection

Abstract: Single-crystal silicon piezoresistive pressure sensors with high overpressure tolerance have been fabricated using the process of silicon fusion bonding. A mechanical stopping surface beneath a conventional diaphragm structure limits diaphragm displacement during overpressure conditions. Uniform and bossed diaphragms in gage and absolute configurations are possible using this process. Sensors with sensitivities as high as 3 mV/ V/psi (typical of sensors used for 5–10 psi full-scale applications) survived overpressures of up to 5000 psi. Finite element modeling is compared to experimental results.

Tensioning device for chain or belt drives

Abstract: A tensioning device for chain or belt drives comprising a damping piston guided in a cylindrical housing and loaded in the chain tensioning direction by a compression spring located in the housing, wherein a high pressure chamber for hydraulic fluid is situated between the housing bottom and the damping piston and is open via a leakage gap formed by the guide bore of the housing and the damping piston and closed with respect to an oil reservoir by a non-return valve, the hydraulic pressure in the high pressure chamber during the operation of the tensioning device being higher in the cold state than in the heated state due to differences in viscosity, characterized in that the high pressure chamber is delimited by an additional piston acting as an overpressure piston on which a second compression spring acts in the direction of the high pressure chamber, the overpressure piston being able to bear against a fixed stop and the spring force of the second compression spring and the effective surface of the overpressure piston are so dimensioned that in the cold state, the overpressure piston is displaceable by the force applied to it by the hydraulic pressure and in the heated state, it is retained at the fixed stop by the second compression spring.

Leak location equipment for waste water channels - includes remotely controlled mobile unit with pressure chamber, over pressure generator and pressure sensors

Abstract: An arrangement for locating leaks in waste water channels contains a remotely controlled mobile device (1) which can generate an overpressure and has two chamber walls (2) which seal a pressure chamber (7) formed by the walls and the section of channel between them. Pressure sensors measure the overpressure in the chamber and in the double walls. A measurement and computer unit compares the individual pressure variations with time and displays the leakage rates. USE - Location of leakage points in general but esp. of those below water level.

Similarities of Shock Wave Damage in Air and in Water

Abstract: The damage done to structures in air or under water by a charge of mass W exploding a certain distance R away, can in both media be described by the so-called square root relation, . This is better than a simple rule-of-thumb, because it implies the physical quantity of an energy density. It is shown that this energy density can also be derived from the product of peak overpressure times impulse for a blast wave in air or a shock wave in water.

A method and arrangement for preventing the spreading of unpleasant odours from lavatory basins

Abstract: An arrangement for preventing the spreading of unpleasant odours from lavatory basins. The arrangement includes an array of inlet openings (10) through which air is delivered at overpressure to the lavatory basin, and an array of outlet openings (11) through which air is extracted from the basin space by suction. The inlet openings (10) for air under overpressure are disposed so that the air exiting therefrom will form a turbulent air layer of given overpressure in the upper part of the basin space, whereas the outlet openings (11) are disposed so that air is extracted from the basin space essentially at a level which lies beneath the air layer. The invention also relates to a method for preventing the spreading of unpleasant odours from a toilet basin.

A new pressure sensor with innercompensation for nonlinearity and protection to overpressure

Abstract: An improved silicon diaphragm pressure sensor with twin rectangular isles is presented. The twin rectangular silicon isles are formed by anisotropic etching and pattern compensation technology for convex corner undercutting. Two pairs of diffused piezoresistive gauges are located at the top surface of the edge grooves and the center groove formed by the twin isles respectively. Innercompensation of nonlinearity can be carried out by using this structure. The optimum compensation conditions have been investigated. An effective design of protection to overpressure is also presented. Its protection range is larger than 25 times the full-scale of the standard pressure range.

A Semiempirical Method for Obtaining Fuselage Normal Areas From Fuselage Mach Sliced Areas

Abstract: An aircraft designed to meet low sonic boom or shaped ground overpressure signature requirements has a volume and lift equivalent area distribution which is in close agreement with the equivalent areas of a desired theoretical curve. Final-stage design modifications of the aircraft's geometry to meet this requirement are usually made through adjustments to the fuselage normal cross-section areas that are derived from the corresponding fuselage equivalent areas by iterative methods. The time required to obtain a good agreement between the desired low-boom area distribution and the conceptual aircraft total area distribution can be reduced by using a semi-empirical method which eliminates much of the final trial-and-error iteration previously employed. Fuselages from conceptual aircraft designed to generate low sonic boom ground overpressures at cruise Mach numbers of 2.0 and 3.0 were used as examples to examine the method's capabilities and limitations. Results indicated that the method has merit as a design tool consistent with other linear theory methods.

Summary of Sonic Boom Rise Times Observed During FAA Community Response Studies over a 6-Month Period in the Oklahoma City Area

Abstract: The sonic boom signature data acquired from about 1225 supersonic flights, over a 6-month period in 1964 in the Oklahoma City area, was enhanced with the addition of data relating to rise times and total signature duration. These later parameters, not available at the time of publication of the original report on the Oklahoma City sonic boom exposures, are listed in tabular form along with overpressure, positive impulse, positive duration, and waveform category. Airplane operating information along with the surface weather observations are also included. Sonic boom rise times include readings to the 1/2, 3/4, and maximum overpressure values. Rise time relative probabilities for various lateral locations from the ground track of 0, 5, and 10 miles are presented along with the variation of rise times with flight altitude. The tabulated signature data, along with corresponding airplane operating conditions and surface and upper level atmospheric information, are also available on electronic files to provide it in the format for more efficient and effective utilization.

Modeling of the Non-Auditory Response to Blast Overpressure. Design and Field Test of a Blast Overpressure Test Module

Abstract: : It has been conclusively determined by field testing, in which the thorax and lung dynamics are directly measured, and by computational simulation, that it is the surface loading on the body which is the direct coupling between the blast field and the biophysical response. The surface loading, expressed as a pressure-time history, differs significantly from the so-called free-field pressure variation that has been widely reported. The two differ both because of reflection, whose effects have been studied under simplified conditions, and because of the geometric effects of the body's shape, orientation to the blast, and relation to surrounding objects, including the ground plane. This latter difference has never been adequately described. If animal exposures to blast are to be properly interpreted, the pressure loading on the body surface must be measured directly. Attempts to place pressure gauges on the animal are extremely difficult and are not practical in routine studies.

Propagation of a Vapor Explosion in a Confined Geometry

Abstract: The propagation of a vapor explosion within a narrow channel has been investigated experimentally with high-speed photography and fast-response pressure instrumentation for two different liquid pairs: (i) a liquid refrigerant and hot oil, and (ii) molten tin and water. In each case, the explosive interaction propagates as a front with a typical velocity in the range of 40–80 m/s. The pressure rise associated with the front has a peak overpressure in the range of 2–9 bar. The low propagation velocity and relatively long pressure rise times (∼1 ms) indicate that the propagation is not coupled to a leading shock wave. With liquid refrigerant drops immersed in oil, spatial propagation of the interaction is due to sequential explosion of the drops. The pressure rise and associated flow from a local explosion collapses the vapor film surrounding a nearby drop, leading to explosion propagation. The conversion ratio of thermal to mechanical energy was estimated to be about 5% in the refrigerant/glycol system. A similar propagation mechanism is observed for molten tin drops immersed in water. In a stratified molten tin/water system, the explosive interaction propagates along the surface of the tin, producing a wedge-shaped wake region that lofts the overlying water and the majority of the tin.

Tunnel-Exit Pressure and Impulse Effects on Free-Field Pressure and Impulse

Abstract: : This report presents the results of a series of experimental tests conducted to determine the effect of the overpressure vs. time history exiting a shock tube was used with a 22.86-cm driver section and a 133-cm driven section to produce a short-duration, decaying, pressure-time pulse at the exit end of the tube. Seven transducer locations recorded the peak over pressure and overpressure impulse vs. time along the zero-degree line. A second series of tests was conducted using a 150-cm driver to produce a long-duration, flattop, pressure-time pulse at the exit end of the tube. Again the overpressure vs. time was recorded at selected distances for comparison with the short driver results. It was determined that the flattop, longer duration, exit-pressure pulses produce higher pressure ratios, Delta P/P sub w, for the same distance ratio, R/ D sub 7, than the short-duration, exit-pressure pulse at R/D sub T greater than 10. It was determined that to correlate the impulse Is outside of the tube with the exit impulse L sub w it was necessary to scale both I sub s and R/D sub 7 by dividing each by I sub w raised to the 1/3 power (i.e. cube. rt.(I sub w)). The effect of the exiting wave shape would have some influence on the present or proposed quantity-distance safety criteria. (JHD)

Geology and Diagenetic History of Overpressured Sandstone Reservoirs in the Venture Gas Field, Offshore Nova Scotia, Canada [Abstract]

Abstract: Overpressured formations with pressure gradients of nearly twice the normal hydrostatic gradient occur over an area of approximately 10,000 km2 in the Scotian basin, offshore Nova Scotia. In the Venture Field, the overpressured zone is confined below a depth of 4,500 m, and contains prolific gas/condensate sandstone reservoirs and hydrocarbon source shales of Late Jurassic-Early Cretaceous age. The Venture Field exemplifies a hard-rock overpressured system developed within normally compacted strata. Late hydrocarbon generation and migration at depth are chiefly responsible for the overpressuring. Venture overpressure differs from U.S. Gulf Coast-type overpressure in that the former occurs within normally compacted shales interbedded with thick, vertically-stacked sandstone reservoir beds. The diagenetic history of the shales and sandstones in the Venture Field has been investigated through petrographic and SEM work. Clay studies show the overpressured shales are well indurated and display similar composition and texture above and below the onset of overpressure. Progressive shale diagenesis over time with compaction has led to near total loss of permeability. The overpressured sandstones exhibit textures and fabrics diagnostic of normal compaction with secondary reservoir porosity developed at depth via leaching of aluminosilicates and porefilling calcite cement. Three depth levels of secondary porosity generation are recognized across both normally and abnormally pressured strata. Hydrocarbon generation and migration lead to pore pressure buildup at depth and are postulated to be the main driving force behind Venture-type overpressure. Peak gas generation was initiated late in the compaction history of the basin. Diagenetic seals, such as impervious shales, sandstones and limestones, within and above the zone of peak gas generation ("hydrocarbon cooking machine"), are believed to behave as aquitards ("pressure cooker"). This results in net increments in rock pore pressure and the establishment of an overpressured zone. The recognition of Venture-type overpressure is important in that it provides clues as to the mechanisms of hydrocarbon generation and migration in the basin. It also defines a model that may assist in understanding overpressured regimes in other frontier basins. End_of_Record - Last_Page 174-------

A study of sonic boom overpressure trends with respect to weight, altitude, Mach number, and vehicle shaping

Abstract: This paper presents and discusses trends in nose shock overpressure generated by two conceptual Mach 2.0 configurations. One configuration was designed for high aerodynamic efficiency, while the other was designed to produce a low boom, shaped-overpressure signature. Aerodynamic lift, sonic boom minimization, and Mach-sliced/area-rule codes were used to analyze and compute the sonic boom characteristics of both configurations with respect to cruise Mach number, weight, and altitude. The influence of these parameters on the overpressure and the overpressure trends are discussed and conclusions are given.

Non-reclosing pressure relief device for vacuum systems

Abstract: A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife.

The effect of molecular relaxation processes in air on the rise time of sonic booms

Abstract: A theory is developed to explain the effect of molecular relaxation processes on the rise time of sonic booms. To determine the rise time of sonic booms, both O2 and N2 relaxation processes must be included. The N2 relaxation process delays the shock pressure reaching the maximum pressure, and the O2 relaxation process causes a shock profile to have a gentle slope. The N2 relaxation controls the lower part of overpressure; the O2 relaxation controls the higher part. The constant rise time curves show that the rise times increase as the overpressures and humidity decrease. The present approach gives longer rise times than those acquired by Bass et al. for given shock overpressures.

Modeling of the Non-Auditory Response to Blast Overpressure. Summary of Blast Overpressure Field Data

Abstract: : This report is a compilation of blast overpressure field data taken at the Blast Overpressure Test Site in Albuquerque, New Mexico. The work was conducted under the direction of Dr. D.R. Richmond and a complete list of source documents is contained in the Reference section. Most of the field tests involved sheep placed in the blast environment. The purpose was to empirically correlate injury to blast wave parameters. This report summarizes the test data compiled to date, but is by no means all inclusive. Corresponding to each test are plots of the associated incident pressure field. The purpose of this report is to provide a convenient summary of these tests for use by all researchers. This report is organized into seven sections, each devoted to a different blast study. They are: Armored Personnel Carrier (APC); Bunker Summer Studies of 85, 86, 87; Double Peak; and Iso-Impulse. Within each section, a separate page describes each combination of charge type, charge weight, height of burst, and range. Keywords: RA 3, Weapons effects (Biological), Non-auditory responses, Blast overpressure, Explosions, Blast injuries, Field data, Tables(Data).

Improvement to the method for lost-foam moulding of metallic components

Abstract: The invention relates to an improvement to the method of lost-foam moulding of metallic components. This improvement consists in applying the increasing isostatic gaseous pressure over the mould after filling at a rate of increase such that the said pressure rapidly and temporarily generates, through loss of pressure through the sand, an overpressure of the molten metal with respect to the sand at the level of their interface, this overpressure reaching a value between two limits and then decreasing as the said pressure increases, then in maintaining the said pressure constant until complete solidification of the component. This invention applies to the production of components, particularly from aluminium alloys, which, in addition to improved compactness (density), have a surface which is free of bubbles (blistering) and carbon inclusions.

Comparison of shock wave rise time prediction techniques

Abstract: Two techniques for predicting sonic-boom rise times are described, and the values of the rise time (defined as the time required for the shock front to go from 10 percent to 90 percent of the maximum overpressure) predicted when using the two approaches are compared. The results are applied to the prediction of the rise time from two hypothetical supersonic transport aircraft. In both cases, the rise time predicted at the ground was much greater than that predicted for a conventional SST.

Accidental Detonation in Underground Munitions Storage Magazines: Prediction of Cover Rupture Overpressures

Abstract: : The Shallow Underground Tunnel/Chamber Explosion Test provides the only known airblast overpressure data produced by venting of the overburden cover from a decoupled high explosive detonation in a large-scale underground munitions storage chamber A limited amount of overpressure data are available from fully-coupled underground high explosive detonations in alluvium (Buckboard 11 and 12, Stagecoach II and III, and Scooter events (Snell et al, 1971)) , two recent tests in a recompacted soil media (Midnight Hour I and II), and small-scale Norwegian model tests in sand (Jenssen, 1979) This paper describes procedures used to develop prediction curves for overpressures produced by airblast venting through the rupture of the cover rock over an accidental explosion in an underground magazine

Influence of vehicle configuration and flight profile on X-30 sonic booms

Abstract: The role of vehicle configuration and the flight profile on sonic booms produced by the experimental NASP X-30 is investigated. Sonic boom signatures, overpressure levels, and footprints for X-30 are presented and compared with sonic boom measurements for F-104, SR-71, Concorde, XB-70, and STS Orbiter. Results show that the sonic boom signatures for X-30 fall within those of previous high-speed planes.