Showing papers on "Atmospheric pressure published in 1969"

Combustion of Boron Particles at Atmospheric Pressure

Abstract: Single particles of pure crystalline boron were injected into streams of hot oxidizing gases, generated by a gas-burner, at atmospheric pressure. Two powder samples, having average diameters of 34.5 and 44.2 μ respectively, were studied. Gas temperatures were varied from 1800 to 2900 °K, mole fractions of oxygen from 0.08 to 0.37, and mole fractions of water from 0 to 0.21. Qualitative photographic and spectroscopic observations of the panicle combustion process are described. Ignition temperatures of boron particles, 1850 to 2000 °K, were found to be independent of particle size and of gas temperature, but affected by the composition of ambient gases. Burning times, ranging from 10 to 40 msec, were found to be inversely proportional to the mole fraction of oxygen in the gas, to decrease slightly with increasing gas temperature, and to decrease substantially with addition of water vapor. Experimentally determined burning rates are correlated with diffusion rates of gaseous oxidants to the surface...

Pressure and Temperature Dependence of the Acoustic Velocities in Polymethylmethacrylate

Abstract: The acoustic velocities in polymethylmethacrylate have been measured with an ultrasonic pulse‐echo technique as functions of frequency, temperature, and pressure. At atmospheric pressure, data on the velocities and attenuation coefficients were obtained for the temperature range of 22°–75°C in the frequency range of 6–30 MHz. For the measurements of velocity and attenuation as a function of frequency, the complex adiabatic bulk modulus was calculated at room temperature and atmospheric pressure for the above frequencies. At temperatures of 25°, 40°, 55°, and 75°C, the pressure dependence of the longitudinal and shear velocity was determined to 150 kpsi at a frequency of 6 MHz. It was found that the measured velocities under increasing pressure conditions were generally lower than those of decreasing pressure by about 0.5% for the longitudinal measurements and about 1% for the shear measurements. However, measurements of the velocities at atmospheric pressure after the specimens had been exposed to 150 kpsi were usually within 0.1% of the initial values. A discussion is presented which compares the continuity of the present data with equation of state determinations in PMMA at elevated pressures.

Atmospheric pressure background fluctuations in the mesoscale range

Abstract: A study of mesoscale-range pressure fluctuations on a large (250-km) array of microbarographs has shown a correlation of seasonal pressure spectrum levels with horizontal distance to the core of jet-stream winds. On a long-term basis, the greatest pressure variance results from occasional synoptic-scale weather disturbances that are concentrated into short intervals of time (at most a few tens of hours). A lower-level but more continuous source of pressure background results from waves generated directly by jet-stream perturbations. These waves correlate in velocity and direction with the jet-stream winds over the array.

Middle distillate fuel having increased low temperature flowability

Abstract: The low temperature flowability of a middle distillate petroleum fuel oil boiling within the range of about 250* to about 700*F. at atmospheric pressure is improved by adding to the fuel oil from about 0.1 to about 3 weight percent of an essentially saturated hydrocarbon fraction which is substantially free of normal paraffinic hydrocarbons and which has a number average molecular weight in the range of about 600 to about 3,000, together with a flow-improving additive such as a copolymer of ethylene and an unsaturated ester, wherein said copolymer has less than six methyl terminating side branches per 100 methylene groups, the weight ratio of said saturated hydrocarbon fraction to said copolymer flow-improving additive being in the range of about 25:1 to 1:1.

Chemistry of polynuclear compounds. Part XV. Halogenocarbonylruthenium compounds

Abstract: Oxidation of dodecacarbonyltriruthenium with halogens (X2; X = Cl, Br, or I) gives the monomeric cis-Ru(CO)4X2, the dimeric Ru2(CO)6X4, the trimeric Ru3(CO)12X6 or the polymeric [Ru(CO)2X2]n depending upon the reaction conditions. On the basis of i.r. studies, it would appear that the initial product in all of these oxidation is cis-Ru(CO)4X2 with subsequent polymerisation to give the dimeric and the trimeric compounds. No evidence for the formation of trans-Ru(CO)4X2 has been found. The dimeric, trimeric, and polymeric compounds are also produced from the reaction of the ruthenium trihalides (RuX3) with carbon monoxide at atmospheric pressure and moderate temperatures. I.r. and mass spectral data are reported and various structural possibilities for these compounds are discussed.Oxidation of (Ph3P)3Ru3(CO)9 with halogens give the mononuclear derivatives (Ph3P)Ru(CO)3X2. These are unstable in solution and decompose with loss of carbon monoxide to give the dinuclear compounds [(Ph3P)Ru(CO)2X2].

Arc Measurement of Some Ar ii Optical Transition Probabilities

Abstract: Wall-stabilized arc measurements employing the generalized Fowler–Milne diagnostic technique have been carried out in argon at atmospheric pressure. Transition probabilities are reported for all lines of the 4s–4p and 3d–4p Ar ii arrays lying below 7200 A.

Oscillator strengths of spectral lines of neutral and singly ionized silicon

Abstract: The emission spectra of a cascade arc operated at atmospheric pressure in argon containing small admixtures of SiCl 4 or SiCl 4 and hydrogen have been analyzed under the assumption that local thermodynamic equilibrium is established in the arc. The radial temperature distribution has been calculated from the experimentally determined radial emission coefficients of ArI lines and from the known values of the transition probabilities. The radial electron pressure distribution has also been obtained from the measured radial profiles or half-widths of the Stark-broadened H β and ArI 6032 A lines. Relative oscillator strengths for 48 SiI and SiII lines were obtained from the corresponding emission coefficients. In addition, an absolute calibration of the relative f -values was attempted using the remaining experimental data. The absolute f -values are partly in agreement with those given by other experimentalists. However, major discrepancies occur between the f -values for SiI lines determined in the present study and the f -values calculated using the Coulomb approximation method and the assumption of L,S-coupling.

High-current arcs in transverse magnetic fields in air at atmospheric pressure

Abstract: This paper gives measurements of the velocity and voltage, and estimates of the size (‘effective drag width’) of electric arcs driven by transverse magnetic fields in air at atmospheric pressure. Ranges of parameters covered are: electrode spacing up to 10cm, magnetic field up to 1.75Wb/m2, and current up to 20000A. Several different electrode configurations and dimensions, and various electrode materials, are used, and conditions have been found where arc movement is virtually independent of the electrode material and spacing. Some comments on the interaction of electrode and column influences are made. In particular, it is noted that electrode influences can be significant under some conditions, and should then be accounted for, in the analysis of experimental results by similarity parameters based on column theory. Although the condensation of data achieved by similarity parameters is very great and highly illuminating in that under many conditions it is possible to predict arc velocity and column voltage gradient within about ±50%, given only the arc current, magnetic field, and electrode spacing and material, there is still much variation within these limits which is difficult to predict. Thus the dependence of the behaviour of an arc on the precise nature of its environment should not be overlooked.

Gravity and atmospheric pressure effects on crater formation in sand

Abstract: An experimental investigation was conducted to determine the effects of varying gravity and atmospheric pressure on the size of small explosion craters formed in cohesionless sand. The explosives used were commercially available squibs and caps and a linear detonating cord. Gravity was varied by flying the test container in an aircraft through carefully controlled maneuvers to simulate 0.17, 0.38, and 2.5 times terrestrial gravity. Atmospheric pressure was controlled separately by means of a ground-based vacuum chamber. The influence of boundary conditions, aircraft vibrations, changes in sand density and moisture content, and techniques of measurement were all considered and evaluated. It was concluded that both gravity and atmospheric pressure, when varied, will lead to significant changes in crater dimensions. The ratio of diameters is inversely proportional to the ratio of gravities to the power n, where n increases as the depth of burst of the explosive increases. The n values are less than 0.16. Crater dimensions are less sensitive to changes in atmospheric pressure in the range from 5×10−4 to about 300 mm Hg than in the range from about 300 to 1000 mm Hg. In the atmospheric pressure range from 300 to 1000 mm Hg, the ratio of diameters is inversely proportional to the ratio of pressures (mm Hg) to the power n, where n = 0.044 ± 0.004. Diameters of craters formed at pressures between 1.0 and 5×10−4 mm Hg were on the average 1.10±0.02 times the diameters of craters formed at pressures near terrestrial atmospheric. Cratering in layers of colored sand was also studied, and effects of pressure and gravity on crater morphology were noted.

Design and Analysis of a High Brightness Axial Flash lamp

Abstract: A high color temperature, pulsed axial flashlamp which is very simple to build is described. The radiation is produced in argon or helium gas which is contained in an alumina tube at atmospheric pressure and allowed to flow out into the atmosphere through a hollow anode. At current densities of 40 kA/cm2 (in a 1.5 cm2 bore) the helium plasma radiates like a 30,000 K blackbody and can produce about one W/ angstrom of uv radiation in a f/8 solid angle. The voltage vs current relation of the arc discharge is of the form υ=K0|i|12 which allows one to design an R, L, C series discharge circuit which can produce a critically damped current pulse of arbitrary length.

Recombination of electrons and ions in an atmospheric argon plasma

Abstract: Spectroscopic studies were made of a plasma jet of argon at atmospheric pressure. Analysis of temperatures, velocities, and excitation populations allowed the determination of the recombination coefficient for electrons and ions and prediction of a dissociative-molecular-ion model to describe the mechanism of the recombination. Temperatures were in the region from 3000 to 11 000°K and electron densities in the range from 10 12 to 10 15 particles per cubic centimeter.

Differential thermal analysis of polyethylene under high pressure

Abstract: The design of a differential thermal analysis apparatus for use at elevated pressure is described. Experiments on melting and crystallization of folded-chain crystals of polyethylene and poly(ethylene–butene-1) copolymer, and melting of extended-chain polyethylene crystals have been conducted at pressures up to 4200 bars. The precision in transition temperature measurement was ±1°C. The Clausius-Clapeyron equation predicts the melting point increase with pressure at atmospheric pressure to be 32.0°C/kb. The melting point depression due to copolymerization remained constant over the complete pressure range analyzed on the poly(ethylene–butene-1) used in this study. Crystallization of polyethylene is retarded at elevated pressures, and a 50% larger degree of supercooling is necessary at 5000 bars to give a crystallization rate equal to that observed at atmospheric pressure. The difference in melting point between folded-chain and extended-chain polyethylene increases from 8.4°C at 1 bar to 25.6°C at 3000 bars.

Tracking Jet Stream Winds from Ground Level Pressure Signals

Abstract: A major portion of atmospheric pressure fluctuations in the 30–90 min period range was observed to move across a small array of microbarographs with speeds and directions that correlate with jet stream winds. Measured speeds (10–50 m sec−1) and periods, with plane wave assumptions, yield wavelengths of the order of 100 km. The pressure fluctuations were observed, however, to decorrelate in much less than one wavelength, implying that they are not free waves, but more likely are disturbances dragged along by the tropopause winds.

Low‐frequency sea level behavior and continental shelf waves off North Carolina

Abstract: Spectrums and cross spectrums of 12 hourly mean sea levels and atmospheric pressures at Southport and Morehead City, North Carolina, show that the response of sea level to pressure is nonbarometric in most of the frequency range studied (0–0.5 cycle/day). Cross spectrums between sea levels adjusted to constant atmospheric pressure at the two stations show phase shifts consistent with the hypothesis of continental shelf waves traveling in the direction predicted by theory (southward). There is some evidence of a seasonal variation in wave speed, which may be associated with the seasonal variation in the surface speed of the Gulf Stream. Broad peaks in the sea level spectrums, centered around a period of 15 days, are also thought to be connected with the Gulf Stream current, rather than with atmospheric pressure.

Extended-chain crystals. VI. Annealing of polyethylene under elevated pressure

Abstract: : Polyethylene crystals of different degree of perfection were annealed at 5.1 kb pressure for 20 hours at varying temperatures and analyzed by electron microscopy, thermal analysis, and density determination. No annealing took place until the temperature of annealing was close to the melting point of the starting material. Up to 235C increasing solid state annealing was observed. Mixed crystals of up to 0.989 g/cu cm density and 1,500 A thickness in the chain direction could be produced. At slightly higher temperature recrystallization to extended chain crystals rather than annealing occurred. Annealing at atmospheric pressure seems to be similar in nature, but takes much longer times for comparable perfection. From a comparison of annealing and crystallization it is concluded that polymer crystallization goes through a stage of internally imperfect order during which most of the observed chain extension occurs. Estimates of this outer imperfect layer of a growing crystal place its depth at 30,000 A. (Author)

Fuel Drop Vaporization under Pressure on a Hot Surface

Abstract: The evaporation lifetime of liquid fuel drops in contact with a hot surface is investigated at pressures of up to 69 atm. Modes of evaporation and drop behaviour at subcriticai and supercritical conditions of temperature and pressure are described. It is shown that at any subcriticai pressure the lifetime is a minimum at a surface temperature just above the saturation temperature; the lifetime at all supercritical pressures is a constant minimum when the surface temperature is 60 degC or more than the critical temperature of the liquid. The heat flux to a drop in the contact modes of evaporation has a maximum value comparable to the peak heat flux obtained in boiling heat transfer work. Subsidiary tests at atmospheric pressure investigate the influence of surface material, surface finish, and initial drop temperature upon the lifetime; the transient surface interface temperature during evaporation is also investigated. The application of the data to deposited fuel in engines is discussed.

Vertical lift machine

Abstract: A maneuverable lifting body wherein pressurized gas is discharged at supersonic velocity over the surface of at least three downwardly sloping lifting surfaces, the supersonically flowing gas separating and thereafter reattaching to the surface to provide a low pressure region intermediate the points of separation and reattachment. The low pressure region created on the upper surface, in cooperation with atmospheric pressure on the bottom of the body, results in vertical lifting forces which add to the vertical component of the momentum forces of the gas. Attitude control and maneuverability are accomplished by selectively venting ambient air into the low pressure regions whereby the low pressure region may be selectively destroyed with resultant force unbalance.

Effect of Humidify on Light-Scattering Methods of Measuring Particle Concentration

Abstract: An experimental investigation was undertaken to isolate and quantitatively determine the effect relative humidity has on the light-scattering ability of aerosols. Both the naturally-occurring ambient aerosol of State College, Pa., and several common test aerosols were used. A measured flow of aerosol was mixed with a measured flow of particle-free air to form a mixture of constant contaminant level; the humidity of this mixture was varied by controlling the moisture content of the clean diluent air. The total light scattered by a given aerosol sample, at various relative humidities, was measured with a Sinclair-Phoenix aerosol photometer (measures the total light scattered in the near forward direction). All measurements were carried out at atmospheric pressure, and after the particulates had an average of 1½ minutes to reach equilibrium with the water vapor. Natural and laboratory-generated aerosols were both tested in this manner.

External combustion power generating system

Abstract: Heat is converted into mechanical energy by introducing into an expansion engine superheated vapor of a thermally stable fluorine containing organic working fluid having a melting point below the lowest normal ambient temperature at the point of use and a boiling point at ambient atmospheric pressure in the range from about 70* C. to about 120* C. and a thermally stable fluorine containing organic lubricant fluid having a melting point below the lowest normal ambient temperature of the point of use and a boiling point at ambient atmospheric pressure substantially higher than the boiling point of the working fluid, condensing the exhaust vapors from the expansion engine, evaporating and superheating the condensed working fluid and returning the superheated vapor to the expansion engine. Lubricant fluid contained in the exhaust from the expansion engine may be separated prior to the condensation of the working fluid and returned to the engine directly or in admixture with the working fluid.

Spontaneous ignition and combustion of sodium droplets in various oxidizing atmospheres at atmospheric pressure

Abstract: The study of the combustion of a droplet of liquid sodium has been made possible thanks to a novel technique which samples the pure molten metal and keeps it free of contamination until released in a heated furnace in a controlled oxidizing atmosphere. Sixteen mm motion pictures were obtained and frame-by-frame examination made it possible to observe a vaporphase diffusion flame separated from the droplet by a visible dead space. This is adequately described by a concentric zones model. Burning rates and evaporation constants have been computed for different temperatures and oxygen mole fractions ranging from 0.1–0.5. The experimental results are interpreted by considering oxygen diffusion to be the rate-determining step.

Coupling between a moving air-pressure disturbance and the sea surface

Abstract: On 23 November 1953 an atmospheric pressure disturbance travelled eastward across Long Island Sound (east of New York City) at an average speed of 42 ft/sec. Simultaneously, abnormal water level heights were recorded with increasing amplitude in Long Island Sound eastward from New York City. This is explained as a disturbance produced by near resonant coupling between the atmospheric pressure disturbance and the free wave traveling in the region of appropriate depth in the Sound. DOI: 10.1111/j.2153-3490.1969.tb00478.x

Shrinkproofing of animal fibers by passing said through an electrical discharge zone containing ozone

Abstract: Proteinous animal fibers are rendered shrinkproof by passing said directly through a high-voltage electrical discharge ozonegenerating zone which is at atmospheric pressure and open to the atmosphere. The dyeing properties of the fiber are unaffected by the treatment. Apparatus embodying both planar and curved discharge zones are described.