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Showing papers on "Overpressure published in 1991"


Patent
16 Apr 1991
TL;DR: A limiting circuit breaker with a molded case comprises an overpressure actuator which brings about actuation by a piston, subjected to this overpressure, of the circuit breaker trip bar as discussed by the authors.
Abstract: A limiting circuit breaker with a molded case comprises an overpressure actuator which, when an overpressure occurs in the arc extinguishing chamber due to the action of an arc drawn by the electrodynamic repulsion of the contacts, brings about actuation by a piston, subjected to this overpressure, of the circuit breaker trip bar. The overpressure actuator forms an almost leaktight assembly.

105 citations


Journal ArticleDOI
01 Nov 1991-Icarus
TL;DR: In this article, the authors present results from fragmentation experiments at elevated external pressure; the application of overpressure to a small target allows the experiment to match the lithospheric compressive stress of a larger body's interior.

82 citations


Journal ArticleDOI
C.A. Catlin1
TL;DR: In this paper, a field-scale experimental study of the external jet explosion caused by a confined explosion vents gas into a cloud of the same mixture is described, and the peak overpressure-jet velocity relationships have been collapsed into a single correlation against an effective Karlovitz number.

59 citations


Journal ArticleDOI
TL;DR: In this article, the results of coal dust explosion experiments obtained by means of the Barknecht-Siwek 20 litre sphere are presented and discussed, which lead to an extension of the hazard limits for coal dusts with respect to data in the current literature.
Abstract: Results of coal dust explosion experiments obtained by means of the Barknecht-Siwek 20 litre sphere are presented and discussed. Several coal dusts have been tested at ambient conditions. The oxygen mass fraction and the initial pressure have been varied to test their influence. The data collected lead to an extension of the hazard limits for coal dusts with respect to data in the current literature. The maximum explosion overpressure depends linearly on the partial pressure of atmospheric oxygen. The ‘optimum’ dust concentration depends linearly on the oxygen concentration in the suspending atmosphere. This has led to a useful non-dimensional representation of the results: in the new variables, maximum explosion overpressure data for a coal dust at various values of the initial oxygen partial pressure are correlated by a single curve for all tests in which most of the oxygen is consumed. Differences in the maximum explosion overpressure exhibited by different coals could not be related to chemical parameters due to the prevailing effect of non-adiabatic explosions in this apparatus at such low rates of pressure rise. The maximum rate of pressure rise has been found generally to increase with the standard volatile matter content and with the hydrogen content in the coal.

23 citations


01 Jan 1991
TL;DR: In this article, the C-weighted Sound Exposure Level (CSEL) was estimated for 43 near steady supersonic flights of the above United States Air Force and United States Navy aircraft.
Abstract: : A sonic measurement program was conducted at Edwards Air Force Base Sonic boom signatures, produced by F-4, F-14, F-15, F-16, F-18, F111, SR-71, and T-38 aircraft, were obtained under the flight track and at various lateral sites which were located up to 18 miles off-track Thirteen monitors developed by Det 1 AL/BBE were used to collect full sonic boom waveforms, and nine modified dosimeters were used to collect supplemental peak overpressures and the C- weighted Sound Exposure Levels (CSEL) for 43 near steady supersonic flights of the above United States Air Force and United States Navy aircraft This report describes the measured database (BOOMFILE) that contains sonic boom signatures and overpressures, aircraft tracking, and local weather data These measured data highlight the major influences on sonic boom propagation and generation The data from this study show that a constant offset of 26 from the peak overpressure expressed in dB gives a good estimate of the CSEL of a sonic boom

16 citations


Patent
01 Apr 1991
TL;DR: In this paper, the products are subjected to an overpressure treatment of at least 10 seconds and then an expansion is effected from the state of overpressure directly to the states of vacuum, wherewith the cells are opened such that the subsequent drying in the vacuum proceeds faster and a porous structure is arrived at.
Abstract: After a thermal treatment the products are subjected to an overpressure treatment of at least 10 seconds. Afterwards, an expansion is effected from the state of overpressure directly to the state of vacuum, wherewith the cells are opened such that the subsequent drying in the vacuum proceeds faster and a porous structure is arrived at.

14 citations


Journal ArticleDOI
TL;DR: In this article, the effects of viscosity and vibrational nonequilibrium on the profile of a weak, spherical N-wave in air are experimentally and numerically studied.
Abstract: Effects of viscosity and vibrational nonequilibrium on the profile of a weak, spherical N-wave in air are experimentally and numerically studied. Weak blast waves were generated, in a quiescent air dome, by spark discharges and exploding wires and observed by high frequency response microphones over 40 meters. Some similarity relationships were obtained from the blast wave experiments. For observed N-waves having less than 100 Pa peak overpressure, the peak overpressure Δpfand the duration of the positive phasetd+are found to vary with the radial distance from the sourcer as Δpf∝r−1.38 andtd+ ∝r0.19, whilst the rise time of the blast wave Δtflinearly increases with distance. Similar trends were also found for the negative phase of the blast wave. Numerical simulations were carried out to compare with the blast wave data. The Navier-Stokes equations for spherical symmetric flows were solved by coupling with a relaxation equation for vibrational excitation of oxygen using the random choice method (RCM) adapted to supercomputing with an operator splitting technique. The resultant N-wave profiles are in good agreement with the experimental results. The numerical results clearly indicate that the wave-easing process due to the dispersive effect of vibrational relaxation plays a dominant role in determining the rise time of the N-wave.

14 citations


Patent
04 Oct 1991
TL;DR: In this paper, the authors propose a method for feeding bulk material into a space under overpressure, wherein the bulk material (20) is fed into a chamber (10) which is pressurized to a higher pressure, preferably corresponding substantially to said overpressure.
Abstract: Method for feeding bulk material into a space under overpressure, wherein the bulk material (20) is fed into a chamber (10) which is pressurized to a higher pressure, preferably corresponding substantially to said overpressure, and the material is fed into the space from the pressurized chamber. Simultaneously with or after the material being fed into the space, the volume of the chamber is reduced to a volume which is a fractional part of the normal volume of the chamber.

12 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the effects of residual air on the heating rate of a convection heating product processed in a continuous rotary sterilizer and found that the average process time was a linear function of overpressure.
Abstract: Effects of residual air were evaluated on the heating rates of a convectionheating product processed in a continuous rotary sterilizer. Heat penetration tests were conducted in a Steritort at various reel speeds (1-10 rpm) and air overpressures (0-69.0 kPa) using 211 × 300, 300 × 407 and 603 × 700 cans containing Washington white beans in brine. Sterilization times calculated by Ball's formula method were longer for test cans processed with overpressure than those processed with no overpressure. Maximum reduction in calculated lethality for 69.0 kPa air overpressure was 15.2% for 211 × 300 and 300 × 407 experiments and 49.4% for 603 × 700 experiments. For each can size and reel speed, average process time was a linear function of overpressure.

11 citations


Patent
15 Apr 1991
TL;DR: In this article, a circuit-breaker with moulded casing includes an overpressure actuator, which constitutes a quasi-sealed unit and acts as a tripping bar of the circuit breaker.
Abstract: A circuit-breaker with moulded casing (10) of the limiter type includes an overpressure actuator (26, 27) bringing about, when an overpressure appears in the disconnection chamber (13) under the action of an arc drawn by the electrodynamic repulsion of the contacts (11, 12), actuation by a piston (26), subjected to this overpressure, of the tripping bar (23) of the circuit-breaker. The overpressure actuator constitutes a quasi-sealed unit.

11 citations


Proceedings ArticleDOI
01 Jan 1991
TL;DR: In this article, a parametric study of loudness levels with respect to weight, altitude, and Mach number for sonic boom signatures generated by two Mach 2.0 conceptual configurations is presented and compared with a similar study for nose shock overpressure.
Abstract: A parametric study of loudness levels with respect to weight, altitude, and Mach number for sonic boom signatures generated by two Mach 2.0 conceptual configurations is presented and compared with a similar study for nose shock overpressure. This paper discusses the relative importance of the two sonic boom metrics and the implications of the trends shown. Of the two configurations considered in this study, one was designed for optimum aerodynamic performance and the second was designed to produce a constrained overpressure sonic boom signature at cruise flight conditions. Results indicate that reductions in both loudness and overpressure level are possible when the configuration is shaped to produce a low boom signature. Results also prove that the loudness metric is a more reliable measure of the disturbance due to sonic booms than nose shock overpressure, because the overpressure does not include the sometimes significant effects of embedded shocks which are often present in mid-field low boom signatures.


Journal ArticleDOI
TL;DR: In this paper, the interdiffusion coefficients and activation energies were determined by correlating the shift in the photoluminescence peaks with the calculated quantum well transition energies based on an error function composition profile.
Abstract: The interdiffusion of In and Ga at an InGaAs-GaAs interface subjected to different annealing temperatures, times, and environments is demonstrated. The interdiffusion coefficients and activation energies are determined by correlating the shift in the photoluminescence peaks with the calculated quantum well transition energies based on an error function composition profile. The results indicate that a higher In composition InxGa1-xGaAs single quantum well (SQW) leads to a higher interdiffusion coefficient of In and Ga in an As overpressure annealing condition. Also, As overpressure increases the interdiffusion, whereas Ga overpressure reduces the interdiffusion. The thermal activation energies for different In composition InGaAs-GaAs SQW’s (x = 0.057, 0.10, 0.15) range from 3.3 to 2.6 eV for an As overpressure environment and from 3 to 2.23 eV for the Ga overpressure situation. With respect to impurity induced disordering by Zn using a Ga or As overpressure significantly effects the depth of the Zn diffusion front but significant mixing does occur in either case when the impurity front reaches the quantum well.



Journal ArticleDOI
TL;DR: In this paper, the authors simulated the effects of explosion of explosives in model subsurface magazines using PISCES 2DELK code and found that the maximum overpressure and velocity of gases and shock waves were in fair agreement with their experimental values.
Abstract: The subsurface magazine is a new type of magazine in Japan, which is defined as a magazine constructed underground and equipped with elevators of other transportation means. and is different from the usual tunnel type underground magazine. Explosions of explosives in model subsurface magazines were carried out. and explosion gases and shock waves blown out from their entrances were observed by schlieren photography. The blast overpressures were also measured by piezoelectric transducers. these external effects by explosion of explosives in the subsurface magazines were found to be less than those in the underground magazines. The above phenomena were simulated by numerical analysis using PISCES 2DELK code. Caluculated maximum overpressure and velocity of gases and shock waves were in fair agreement with their experimental values.

Patent
23 Mar 1991
TL;DR: In this paper, the products, following a thermal treatment, are subjected to an overpressure treatment of at least 10 seconds, by means of which the cells are disrupted, so that the subsequent drying in vacuum proceeds more rapidly and a porous structure is obtained.
Abstract: In this process, the products, following a thermal treatment, are subjected to an overpressure treatment of at least 10 seconds. The products are then flashed directly into vacuum from the overpressure, by means of which the cells are disrupted, so that the subsequent drying in vacuum proceeds more rapidly and a porous structure is obtained. … …

Proceedings ArticleDOI
01 Oct 1991
TL;DR: In this paper, the design of overpressure proof tests for large airborne infrared windows is discussed, and a hypothetical proof test design for a large infrared window to be employed in a man-rated aircraft is developed to illustrate the application of the analytical methodology.
Abstract: Many commonly used infrared window materials, such as zinc sulfide and zinc selenide, are subject to structural failure due to stress-corrosion induced cracking. This failure mechanism is of critical importance in applications in which the window experiences high static pressure loading for prolonged periods in humid atmospheres, conditions typical of airborne optical windows. The most effective means of screening windows against failure due to this mechanism is by use of overpressure proof testing. In this paper, the design of overpressure proof tests for large airborne infrared windows is discussed. The underlying physical phenomena and governing mathematical relationships are presented. A hypothetical proof test design for a large infrared window to be employed in a man-rated aircraft is developed to illustrate the application of the analytical methodology; Practical considerations in the execution of large infrared window overpressure proof tests are also discussed.

ReportDOI
01 Jan 1991

ReportDOI
01 Jan 1991

Journal ArticleDOI
TL;DR: The reverse-jet overpressure pulse used to detach filter cakes from fabrics in continuously-rated fabric dust filters can be regarded as a random sequence of pulses superimposed on a more slowly fluctuating pressure continuum as mentioned in this paper.
Abstract: The reverse-jet overpressure pulse used to detach filter cakes from fabrics in continuously-rated fabric dust filters can be regarded as a random sequence of pulses superimposed on a more slowly fluctuating pressure continuum. These pulses can have rates of rise of 200 Pa.μs−1, considerably more intense than the continuum value of approximately 600 Pa.ms−1 which is necessary to detach the filter cakes satisfactorily. By isolating the continuum pressure electronically, the energy spectra of these pulses have been studied for a range of reverse-jet assemblies. It has been found that the number and amplitude of these pulses can be reduced significantly by suitable design of the reverse-jet assembly. These observations are fully in accord with jet mixing theory when applied to reverse-jet assemblies, as indicated in the previous paper in this series(1).

Patent
21 Feb 1991
TL;DR: In this article, a compression spring is used to act on an overpressure piston in the direction of the high pressure chamber to obtain the characteristics which are uniform over a wide range of temperatures and which are independent of the difference in oil viscosity.
Abstract: PURPOSE: To obtain the characteristics which are uniform over a wide range of temperatures and which are entirely independent of the difference in oil viscosity by allowing a high pressure chamber to be limited by an overpressure piston, and allowing a compression spring to act on the overpressure piston in the direction of the high pressure chamber. CONSTITUTION: A high pressure chamber 9 is limited by an overpressure piston 10. A compression spring 12 acts on the overpressure piston 10 in the direction of the high pressure chamber 9. In the cold state, the overpressure piston 10 is displaceable by the force formed in the overpressure piston 10 by hydraulic pressure. In the heated state, the spring force of the compression spring 12 and the effective area of the overpressure piston 10 are set so that a stopper is held by the compression spring 12. Thus a tensioning device for chain or belt drives obtains the characteristics which are uniform over a wide range of temperatures and which are entirely independent of the difference in oil viscosity.

Patent
06 Nov 1991
TL;DR: In this paper, a central locking system for locks of doors and/or flaps of motor vehicles having pneumatic central-locking and theft-prevention elements and having a PNEumatic control unit which can generate two different overpressure levels and one underpressure level, for the simple and cost-effective generation of the different pressure levels there is a relief valve which has the control unit.
Abstract: In a central locking system for locks of doors and/or flaps of motor vehicles having pneumatic central-locking and theft-prevention elements and having a pneumatic control unit which can generate two different overpressure levels and one underpressure level, for the simple and cost-effective generation of the different pressure levels there is a relief valve which has the control unit. The relief valve opens at a predetermined overpressure level which is between the low overpressure level and the high overpressure level. Furthermore, the control unit has a shut-off valve which follows the relief valve.

Journal ArticleDOI
TL;DR: In this paper, the fast response capability of the hot film shear gauge was used to perform unique shock tube and field test blast wave surface shear measurements, and mean flow turbulent calibration data were presented from three different test facilities: a low speed wind tunnel, a high pressure pipe facility, and a laboratory scale shock tube.
Abstract: Use is made of the fast response capability of the hot film shear gauge to perform unique shock tube and field test blast wave surface shear measurements. Mean flow turbulent calibration data are presented from three different test facilities: a low speed wind tunnel, a high pressure pipe facility, and a laboratory scale shock tube. Favorable agreement in calibration data between the three facilities is demonstrated. The good correlation in calibration results validates the ‘‘established’’ formulation procedure and provides a unique verification of available shock tube shear data. Measurements of ground shear under clean wall, i.e., nondusty, flow conditions are reported for blast waves created by high explosive detonations under large scale field test conditions. Satisfactory scaling of results in terms of event yield and overpressure location is demonstrated.

Journal Article
TL;DR: In this article, the generic allowable internal gas pressure not violating this criterion is estimated as a function of rod power, and the results show that the generic allowed internal pressure decreases linearly with the increase of rod's power.